In this, the second edition, I have taken the opportunity to bring the book up to date in the light of subsequent developments; to rewrite entirety the "Historical Survey" (Chapter II); and to make an addition to the Appendix of a bibliography.

I have also been able to embody the gist of the very valuable criticisms of the first edition, made direct to me, by Mr. G. Edward Pendray, President of the American Rocket Society, and by Herr Willy Ley, Vice-President of the German Rocket Society. Outside of Russia, these two gentlemen, and Dr. Goddard, plan and direct practically all the important experimental rocket research that is being done to-day, and the corrections now made should add greatly to the authoritative value of the book.

The first edition having already justified its existence, renders any further introduction unnecessarj, and I therefore place the second edition, with every confidence, in the hands of the English public, as the standard popular work on Astronautics.

CHAS. G. PHILP.

CUFFLEY, HERTS.

August, 1935.

In presenting this book to the public, I believe it to be the first work of its kind published in England. For this reason I hope it will prove interesting reading to many.

I owe particular thanks to Mr. Hugo Gernsback, of New York, for the very extensive use of subject-matter and drawings which have appeared in Science and Mechanics and Wonder Stories, and also to the Daily Express and Sunday Referee for details particularized in the text.

I have drawn also upon information contained in Modern Mechanix, Popular Science Monthly, and numerous other publications, to the authors and publishers of which I take this opportunity of expressing my indebtedness.

C. G. P.

Consider, for example, the lot of the early pioneers of heavier-than-air flight. Apart from the great risk to life and limb which acconrpanied their earlier experiments, the very forces of Nature seemed allied against them.

The vast mysterious force of gravitation, so palpably manifest everywhere, seemed to offer a fundamental physical barrier which they could never hope to surmount.

Every falling stone, every stream of water, a feather even, followed the inexorable law of gravitation and fell back to earth or sought its lowest level. How then could a heavier-than-air machine be expected to fly ?

And to add to their difficulties, the weight of orthodox scientific opinion was all against them. Indeed, a famous astronomer demonstrated mathematically that heavier-than-air flight was an impossibility !

Nevertheless, as all the world knows, the modern miracle of heavier-than-air flight was first successfully achieved by Wilbur Wright on 17th December, 1903. Since that date the progress and development made during its lifetime of thirty years have been without parallel in the scientific world.

The Wright aeroplane, with a 12-15 h.p. engine, attained a speed of about 35 miles per hour. To-day speeds twelve times as great have been achieved. In the early days of aeroplane flight it was something to talk about when a passenger was carried for the first time. To-day the giant German aeroplane, the DO-X, with engines developing 7000 h.p., weighs 50 tons, and has carried as many as 169 people at one time.

Over 25,000 aeroplanes are now in use, and regular air services link all parts of the world. In Europe alone-there are over 00,000 miles of air routes, and it is possible to connect from London with over 150 Continental cities, most of which can be reached in one day.

In the London-Melbourne Air Race of October, 1934, all previous records were broken to an amazing degree. India was reached in one day, Singapore in forty hours, Australia (Port Darwin) in 5 2| hours, and Melbourne in just under three days.

Mainly as the result of these remarkable achievements, experts now confidently assert that transatlantic and transpacific aeroplane services will be inaugurated within a very short time — probably during 1938. These services are planned to run twice daily — east to west and west to east- — and will convey mails and passengers. They will be made safe and practicable by means of a chain of floating "seadromes" anchored to the sea bed at intervals of 500 miles. The successful accomplishment of services of this kind will mark an epoch in the history of the world comparable with the opening of the Suez and Panama Canals.

As to the near future, planes nearly three times the size of the DO-X are being planned, and speeds of 1000 miles per hour are confidently predicted.

It is at this juncture, as if to tax man's credulity to the utmost, that the science of Astronautics, or Space Flight, gradually begins to force itself into public notice.

For many years past, bands of earnest and enthusiastic workers — scientists, "dreamers," and practical men — have been striving to solve the problem of travelling in the vacuum of outer space. It is the result of their labours, their experiments, calculations, and analyses of the conditions and requisites necessary for space flight, not only in the upper limits of the earth's atmosjDhere, but beyond it in the vacuum of space, that has formed the skeleton framework upon which the new science of Astronautics is based.

Not only would travelling in the highly rarefied regions of upper and outer space require but a fraction of the power expended by the ordinary aeroplane, but at such altitudes an eternal sameness reigns. The adverse climatic conditions encountered in close proximity to the earth's surface, such as fog and snow% lightning, and storms, are non-existent there. Hence, travelling at ultra-high speeds, with safety and reliability, is always possible in these altitudes, no matter what may be the conditions below.

And it is because no form of internal combustion-engined aeroplane could conceivably operate in these highly rarefied regions, and because the ultra-high speeds projected would be quite impossible in the lower regions, on account of the heat generated by friction, that an entirely new type of space ship has had to be evolved. Thus an entirely new science of space flight has come into being. This new science has been called Astronautics.

Notwithstanding the enormous progress and development of the present-day aeroplane, and notwithstanding the brilliant prophecies made on its behalf for the future, the adherents of Astronautics maintain that the potentialities of space flight are so vast and stupendous, that it offers to futurity a revolution in passenger transit, as great in comparison with present-day air travel, as the locomotive and the motor-car were to the horse-driven stage coach.

Where air flight promises the accomplishment of future long distance journeys as a matter of days, space flight promises the same in hours. In fact, it is affirmed that by space flight no terrestrial journey, even to the most distant part of the world, need be longer than a matter of two or three hours! And, moreover, once this stage is reached, journeys to the moon, or even Venus or Mars, far from being an impossible dream, will be reasonably possible of achievement.

That such interplanetary journeys will one day be attempted seems more than probable. In every age, and in every clime, intrepid men will be found, who are prompted by a high spirit of adventure, caring as little for terrible risks and dangers as for the hope of reward. The more daring spirits among them, "longing for fresh worlds to conquer," will, of a certainty, push out, ever further and further, into the vastness of space. The call, the urge, of the unfathomable unknown will be on them, for even to-day it is generally conceded that there may well be inhabited worlds other than our own. Who knows but that one day these ardent spirits will laugh at us "ancients" for declaring interplanetary travel "impossible," just as the scientists, wriseacres and critics of only thirty years ago declared heavier-than-air flight "impossible"?

As this is a much debatable question, we will leave it for the present, and confine ourselves to the more immediate and practical problem of space travel in its application'to terrestrial journeys.

Modern reaction propulsion may be said to date from 1919, in which year Professor Robert H. Goddard, of Clark University, Worcester, Mass., announced to the world the results of the experiments by which he verified his previous belief that the rocket would operate as effectively, or more so, in a vacuum.

Although his work was anticipated by the Russian author Konstantin E. Ziolkovsky, who in 1903 published a theoretical treatise entitled The Rocket in Cosmic Space, Professor Goddard was, nevertheless, the first scientist to put his theories to actual experimental test and proof.

Professor Goddard's proposals wrere twofold —

1. To send rockets up into the atmosphere for meteorological purposes and research data; and

2. To send to the moon a rocket, which on arrival there would light a magnesium flare, thereby proving it had duly reached its destination.

Generally speaking, Professor Goddard was not taken seriously at the time. Subsequently, however, the idea that reaction propulsion, as exemplified in the rocket, was a practicable principle for terrestrial and interplanetary transportation, gradually impressed itself on scientific minds, and every important country in the world began to regard the rocket seriously.

At the present time there are groups and individuals hard at work on this problem in the United States, France, Germany, Austria, Russia, England, Holland, Italy, Romania, and Japan, each and all seeking to solve the technical barriers to the practical application of reaction propulsion as exemplified in the rocket. In order to trace the progress and development made, it will perhaps be best to describe in detail the activities of each country, more especially as the various groups have not always been able to agree with each other, and even to-day are still divided in opinion over various important questions.

In America, as the result of a donation of ?20,000 made by the late Mr. Simeon Guggenheim to the Goddard experiments, Professor Goddard was able, in 1930, to establish a modern, completely equipped rocket laboratory at Roswell, New Mexico. Here for two years he carried out his experiments with meteorological rockets, but the economic depression compelled him to cease his labours, and in 1932 he resumed his duties at Clark University. However, this interruption in his experimental work proved only of a temporary nature, and in 1934 he was able to return to Roswell, where he is at present actively engaged as before. His last announced intention is to develop altitude rockets for stratosphere research, with the idea of reaching heights of forty miles or more.

Professor Goddard's researches have also taken the form of devising a mechanism which combines the principles of the rocket and the turbine. He hopes thereby to give to the world an entirely new vehicle of transportation, capable of travelling hundreds of miles above the earth's surface, and perhaps one day of making a trip to the moon. He was granted a patent for this new rocket turbine in 1931.

Another American who is devoting his attention to the matter is Harry W. Bull, who gained international attention in the spring of 1930 by his experiments with a rocket sled. Mr. Bull, whilst a student at Syracuse University, N.Y., was granted the use of the laboratories of the University to enable him to carry out exhaustive experiments for developing and adapting liquid fuels for rocket propulsion. With a view to increasing the range of the rocket, he also conducted research work, extending over a period of eight months, on the rocket combustion chamber. Although Mr. Bull, having graduated, has now left the University, he still continues his experimental rocket activities as part of his private life.

Public interest in rocketry was slow to awaken in America, and no definite organization was created until March, 1930, when a group of scientists and laymen founded the American Interplanetary Society with Mr. David Lasser as President. In 1934 Mr. G. Edward Pendray, who did so much toward the organization of the Society in the first place, succeeded Mr. Lasser as President, and the title of the organization was changed to that of the American Rocket Society.

The American Rocket Society is devoted to scientific research in the development of rockets for high altitude and long distance flight. Its programme consists of developing high altitude rockets capable of carrying cameras, meteorological instruments, cosmic ray recorders and other equipment for the exploration of the upper atmosphere.

Under the able presidency of Mr. Pendray, who personally plans and directs all experiments, the Society's designers have constructed liquid fuel rockets of remarkable efficiency. They have also devised feeding systems that do not require pumps, and made considerable progress in evolving dependable landing gear, and the development of proper steering apparatus. Thanks to the practical knowledge gained by Mr. Pendray when he visited the Raketenfiugplatz, Berlin, in 1931, the Society does not look to sensational immediate results,'but rather to the building up of a technique of rocketry on a solid basis which will make its future secure.

Prominent in the membership of the American Rocket Society are Dr. Robert H. Goddard, the famous rocket experimenter of Clark University; Dr. H. H. Sheldon, Professor of Physics, of New York University; Sir Hubert Wilkins, the explorer; Robert Esnault-Pelterie, French aviation engineer and rocket designer ; Willy Ley, Vice-President and Secretary of the German Rocket Society, and rocket designer ; Professor Nicholas Rynin, Russian rocket experimenter and mathematician ; and others.

The growth of interest in America in rocketry is also evidenced by the formation of other societies in other parts of the country, e.g. Cleveland, Ohio ; and Peoria, Illinois; and it is not too much to say that America is fast becoming the premier country in the world in the development of this infant prodigy of science.

In France, thanks to the generosity of Andre Hirsch, a well-known banker, and Robert Esnault-Pelterie, an aeronautical engineer of international reputation, the French Astronomical Society awards an annual prize of 10;000 francs (1931) for the best scientific work, theoretical or practical, which has for its object the furtherance of astronautics.

Monsieur Esnault-Pelterie, in addition to being a well-known scientist, is also the author of L'Astronau-tique. This work, based on the results of twenty-five years' investigations in aeronautics and astronautics, deals most exhaustively with the problem of rocket flight, and also includes a systematic plan, with all details worked out, for a journey to the moon. First, however, he plans to build a rocket containing only scientific instruments that will travel one hundred miles into the air, and, by means of a parachute, bring back data of the atmosphere.

In Germany the real beginning of rocketry may be said to date from the publication, in 1923, of a booklet by Professor Hermann Oberthv entitled Die Rakete zu den Planetenraumen. Professor Oberth is not only a great mathematician, but also an astronomer and physicist of the first order. His later publication, Wege zur Raumshiffdhrt, is to-day regarded as the classic work on rockets throughout the whole world. It is, however, far too advanced in its mathematical treatment for the average person to follow.

In 1927 the German Interplanetary Society was formed, and practical work began in real earnest in 1928. In this year several rocket-driven cars were produced, and the first rocket aeroplane successfully flew a distance of about one mile. Owing to the inefficiency of the rocket motors in an atmosphere, this line of development gave little promise of being a commercial proposition, and it was believed that the science of rocketry would be best furthered by concentrating on the development of aerial rockets.

Practically the whole of the practical and experimental work in connection with the development of aerial rockets was carried out at the Raketenfmgplatz, near Berlin- — the largest and most extensive experimental ground in the world for the study of rockets, being larger than the famous flying fields at Templehof. It is situated at Reinickendorf, barely five miles from the German capital, and extends northwards into the surrounding hilly country.

Here, under the support of the German Interplanetary Society (the Verein fur Raumschiffahrt; Professor Oberth, President), a staff of engineers was kept hard at work for several years in an endeavour to develop giant rockets to commercial purposes. But following the Hitler revolution, and partly due to internal dissension, this, at one time the largest society of astronauts and rocket enthusiasts in the world, was dissolved, and Professor Oberth left Germai.

It was succeeded by a new organization known as the E.V. Fortschrittliche Verkehrstechnik, with Major Hans Wolf von Dickhuth-Harrach, the well-known German aeronaut, as President, and Mr. Willy Ley, Secretary and Vice-President of the old Verein, holding similar offices in the new organization. Mr. Ley is but 29 years of age, he knows and has met practically everybody of note in the world of rocketry, and has an extensive knowledge of foreign languages. He is the official representative of his Society in all foreign rocket societies, and is an acknowledged and world-renowned authority on rocketry. With Mr. Ley as its moving spirit it is confidently expected that active experimental work will soon begin again at the Raketenflugplatz of the old Verein.

Apart from taking an active part in numerous German rocket experiments, Mr. Ley is the author of three books and of many articles on rocketry. He is at present (July, 1935) the guest of the American Rocket Society, New York, who are preparing a special rocket flight in his honour.

In Russia in 1903 a scientific theory of space travel was advanced by a Russian author, Konstantin E. Ziolkovsky, under the title of The Rochet Into Cosmic Space. This book was subsequently followed by others, and aroused great interest in Russia, which later on spread into Germany.

The World War, and its after effects, put an end for a time to the interest thus aroused, but in 1928 it was again revived by the publication in Leningrad of the first volume of a projected series of twelve of an encyclopaedia of rocketry. The author was Professor Nikolai Rynin, a mathematician and engineer of considerable repute, and the title of the work was Interplanetarer Verkehr (Interplanetary Communication). Up to the present time nine of the twelve volumes have been published.

In 1929 the Russian Rocket Society was formed, under the guidance of Professor Rynin and Dr. Jakow I. Perlmami — the latter a distinguished scientist at the Leningrad University Observatory.

Russia has recently attracted world-wide attention by the Soviet stratosphere balloon ascents, and to-day holds the world's record of 1 If.miles, made on 30th September, 1933, with the safe return of its passengers. In January, 1934, the Soviet balloon "Sirius " reached the record height of nearly 13 miles, but collapsed and crashed, killing its three occupants.

Concurrently with these balloon ascents Russia has been active with experiments and research work in rocketry. In this respect the line of research would appear to take a much more practical form than those at present being carried out in Germany and America, consisting mainly of a combination of the aeroplane and rocket plane. Latest advices from Moscow state that the first experimental passenger rocket will in all probability be ready this year (1935). It will be similar in shape to the present "streamlined" aircraft, and will be propelled by liquid oxygen, by which motive power they hope to revolutionize air transport. Tests will first be made at lower altitudes, with one man inside, preparatory to stratosphere ascents later. Although the rocket plane is hopelessly inefficient at low levels, and for that reason practically abandoned by German and American experimenters, surprising results are anticipated in the stratosphere, where a fraction of the same propulsive effect — only obtainable in this practically airless region by rocket propulsion — will produce enormously greater results.

Good work is also taking place with aerial rockets, of the type experimented with in Germany and America and a Soviet committee has recently (June, 1935) ordered the construction of a rocket capable of attaining an altitude of 34 miles, whilst plans are being studied for a larger rocket designed to ascend several hundred miles.

In England, thanks to the sympathetic encouragement of three well-known publications — Chambers Journal, the Liverpool Echo, and the Daily Express — the first English Rocket Society was formed in October, 1933. Its title is "The British'lnterplanetary Society" and it owes its origin to the energy and enterprise of its first President, Mr. P. E. Cleator. The address of the Secretary is 46 Mill Lane, Liverpool, 13.

Mr. Cleator is the author of the article, "The Possibilities of Interplanetary Travel," which appeared in Chambers s Journal for January, 1933, and of numerous other contributions. By his visit to Germany in January, 1933, when he made a tour of the Raketen-flugplatz, Berlin, and other German centres of rocketry, he acquired valuable first-hand knowledge of the practical progress already made.

Among the names of the Fellows of the British Interplanetary Society are Herr Willy Ley (Germanj), Robert Esnault-Pelterie (France), Ing. Guido Pirquet (Austria), and Dr. Jakow Perlmann (Russia), whose names have already been mentioned under their respective countries.

In Holland the first rocket organization was formed in 1934 under the title of "De Nederlandsche Raketen-bouw."

All told, in Europe and America, there are to-day several thousand enthusiasts belonging to the various societies, who contribute regularly to the cost of the experiments at more than a score of experimental stations.

Each of the countries above referred to is engaged on essentially the same programme.

Their first aim is to build an altitude rocket which will travel to the extreme limits of the earth's atmosphere — a distance of probably 200 miles or more. These rockets will be driven by powerful liquid fuels, contain scientific instruments only, and after their flights will return safely to earth by parachute.

Once successful in this direction, the next stage will be the construction of rockets for the conveyance of mails and commercial traffic between the capitals of Europe. Such rockets would be under control from start to finish, and travel at enormous speeds.

These in turn would be followed by transatlantic rockets designed for a similar purpose, and then by rockets capable of crossing any ocean, or even encircling the world.

But long before this latter stage has been reached, the single-passenger-carrying rocket will have been evolved, and by degrees the size of these will be increased until, finally, huge strato-liners will connect even the most distant parts of the globe by journeys of a few hours.

Such is the dream of the astronautist. We will now see what practical reasons there are for anticipating such a revolution in terrestrial travel.

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Here it may be stated that it is one of the great assets of flight by reaction propulsion that the rate of acceleration can be regulated to any required degree, just as one controls the speed of a petrol engine.

Having outlined in Chapter III a method of propulsion which is operative in space, or in a vacuum, and having shown in this chapter that, even at the rate of acceleration of a racing car, enormous speeds can be quickly attained, and once attained can be endured without discomfort, we will now proceed to learn something about the medium through which space flight is to be carried out.

Obviously, however, there must be a limit to the speed of flight through the earth's atmosphere, owing to the enormous heat generated by frictional resistance with the air. Hence, in order that we may see why reaction propulsion is, as previously stated, the only possible method of attaining the ultra-high speeds requisite for long distance terrestrial journeys of the future, we must now make an analysis of the depth and composition of the earth's atmosphere, and ascertain why this limitation in speed applies to all possible kinds of flight other than rocket flight.

We know that the earth is surrounded by an envelope of air which accompanies it in its journey through pure space — pure space meaning the region free from even the slightest trace of airy known form of atmosphere or gas.

This envelope of air is attracted to the earth by gravity, and just as the pressure of the ocean increases as one descends into its depths, so the pressure of air is greatest at the surface of the earth, which corresponds to the ocean bed. The higher we rise above the earth's surface, the less the pressure and density of the atmosphere become, and the less is the resistance offered to objects passing through it.

Fortunately, we can obtain fairly accurate data as to how far the earth's atmosphere extends, and also of its nature and composition, the former by its action on meteors, and the latter by the aid of observational balloons, containing merely registering apparatus and instruments of various kinds. Some additional information has also been obtained in this latter respect by recent investigations into the "skip effect" of wireless waves.

Shooting stars, or meteors, are known to be cold before they enter the earth's atmosphere, because they are invisible prior to doing so. But as soon as they strike the atmosphere the frictional resistance, at the enormous speeds at which they enter it (26 miles a second) is so great as to render them incandescent and therefore visible. In the majority of cases the heat thus caused is such as to consume entirely the rock or . matter of which they are composed, and all that remains of them is a fine dust.

By taking careful note of the height at which these meteors first become visible, it is possible to calculate how far they must have travelled through the atmosphere to have brought about incandescence. Hence, by adding this calculated distance to the actual height at which they were first observed, we can form a fair estimate of the total depth of the atmosphere surrounding the earth. Numerous observations have shown that meteors are rarely seen at a greater-height than 100 miles, and the total depth of the atmospheric envelope is usually accepted as being approximately 200 miles.

The invention of the passenger-carrying balloon in 1783, and its subsequent development, encouraged hardy explorers to venture higher and higher into the atmosphere, with a view to obtaining scientific data regarding its temperature, pressure, etc., but it was found that great risks were incurred by such attempts, and many lost their lives.

Until a very few years ago, the greatest height attained by any human being in a balloon was slightly under 7 miles. But at such great heights the outside pressure becomes so much less that blood often oozes from the ears, the eyeballs become frozen, and even though oxygen breathing is resorted to, the balloonists frequently lose consciousness.

So that these risks might be minimized, and even greater heights attained, small "sounding" balloons were invented. These were based on the principle that as the balloon rises the pressure outside diminishes, allowing the gas inside to expand. Hence, as the balloon rises it expands more and more, until ultimately it bursts, and in doing so releases a small parachute which brings back safely to earth the self-recording scientific instruments it carried. By the aid of "sounding" balloons of this type, definite data has been obtained of the earth's atmosphere at a height of over 23 miles.

We also know, from the principle of the barometer, that the weight of the air belt surrounding the earth is equivalent to a pressure of 14-7 lb. per square inch at sea level, and this provides another means of ascertaining the depth of the atmosphere.

From calculations based on the preceding and other data, it is estimated that the oxygen-nitrogen atmosphere, which we breathe, ceases at a height of 40 to 50 miles above the earth's surface.

Beyond this, for another 100 to 150 miles, is believed to exist a highly rarefied atmosphere, consisting of lighter gases, such as hydrogen and helium, and this extends until the ether of pure space begins.

The nature of the ether of space, in which the heavenly bodies swim, can be only vaguely conjectured. According to science, it is a substance finer than any known to our five senses, and it extends not only beyond the most distant star, but even penetrates the densest bodies here on earth.

A body once set in motion in this ether of pure space would, it is believed, travel on for ever, frictional retardation being non-existent. Such a body would, of course, be always subject to the pull or retardation of gravity, since the force of gravity is also supposed to extend to the utmost limits of space.

These gravitational effects may be sometimes compounded or even neutralized, according to the positions of the heavenly bodies in closest proximity. An everyday example of this compounding effect is evidenced by the action of the sun and moon on the waters of the earth producing tidal conditions. When these bodies are in conjunction spring tides result. When in opposition neap tides are produced.

Quite recently the atmosphere has been mapped out by scientists into five regions. These are as follows —

(a) The Troposphere — a zone of winds, clouds, and climatic changes, extending up to an approximate height of 7 miles. This zone also marks the limit of the breathable atmosphere.

(b) The Tropopause — a variable region of 2 to 3 miles above the Troposphere and separating it from the

(c) Stratosphere — a region consisting principally of nitrogen, and extending upward to a height variously estimated at 50 miles above the earth's surface. Next comes the

(d) Upper Stratosphere — believed to consist mainly of lighter gases, hydrogen and helium, and including the remainder of the gaseous envelope, until the ether of pure space begins. But overlapping (c) and (d) is the region known as the

(e) Kennelly-Heaviside layer — discovered as a result of wireless experiments, and thought to consist either of ionized gas or frozen hydrogen in minute particles.

Numerous calculations have been made with a view to ascertaining the density of the atmosphere. It is now generally accepted that the density decreases by one-half for each 3¹/₂ miles of altitude.

As each 3¹/₂ miles involves a power of 2, the density by this formula decreases at an amazingly rapid rate.

Thus, by using the above formula, the density at a height of 10¹/₂ miles — the "floor" of the Stratosphere-would be approximately 1/10th that at earth level, at 49 miles — the "ceiling" of the lower Stratosphere - it would be only 1/66,370th, and at 70 miles it would have decreased to such an amazing extent as to be less than one-millionth the density at sea level.

When in a later chapter we deal with the limitations of aeroplane flight, the importance of these figures will be appreciated.

Up to the year 1931 the greatest height attained by man was slightly over 8 miles, but on 27th May of that year Professor Auguste Piccard, of the University of Brussels, and Herr Kipfer, ascended by balloon from Augsburg, Bavaria, and reached a height of 15-5 kilometres (9-6 miles).

Realizing and anticipating the very great risk of exposing themselves, in the open, to the intense cold and greatly reduced pressure known to exist at great heights, these intrepid balloonists enclosed themselves in a hermetically sealed aluminium ball, and by this means they survived the ascent without appreciable physical suffering. They demonstrated most decisively that, when suitably protected in this manner, it was possible and practicable to explore the hitherto unattainable region known as the Stratosphere.

Professor Piccard repeated his ascent the following year, rising still higher than at his first attempt. His second ascent was made on 17th August, 1932, and he was accompanied by M. Cosyns. They ascended from the Dubendorf Aerodrome near Zurich, and whils over the Engadine they reached an altitude of 16,700 metres (10T2 miles).

On 30th September, 1933, Professor Piccard's record was beaten by the Soviet balloon "U.S.S.R.," which reached a height of llf miles and returned safely to earth. In January of 1934 a further attempt by a Soviet stratosphere balloon " Osoaviakhim " ("Sirius"), ended in disaster, after setting up the still unbroken record of nearly 14 miles.

The next attempt was made by the American Army Air Corps Stratosphere Expedition, in the balloon "Explorer" on 27th July, 1934, Major William E. Kepner acting as pilot. It reached a height of 11 miles and then split up, the occupants safely landing by parachute.

A few months later, on 22nd October, Professor Jean Piccard, twin brother of Professor Auguste Piccard, took off from Fort Airport, Detroit, and after an ascent of 10 miles landed safely at Cadiz, Ohio, 200 miles away. He was accompanied by his wife, Mrs. Jeannette Piccard, the first woman to make an ascent into the stratosphere.

On 26th June, 1935, a Soviet balloon, ascending from Moscow aerodrome, made a successful stratosphere flight, soaring nearly 10 miles. The remarkable feature of this balloon was that in the event of an accident the envelope would be converted into a gigantic parachute, capable of landing the gondola and its occupants safely from enormous heights.

Hoping to retrieve the failure of Jufy last year, the United States Army staged another stratosphere ascent for the 12th July in the world'-s largest balloon "Explorer II," but owing to some cause, not yet revealed, the balloon burst during inflation. The ascent was to have been made from Rapid City, South Dakota,, with Capt. Albert W. Stevens in command, and it was hoped that an altitude of 15 miles would have been attained.

Several stratosphere ascents during 1936 are now being planned, including one of 19 miles by Professor Auguste Piccard, the first human being to explore the lower regions of the Stratosphere — a region with which astronautics is vitally concerned.

In view of the widespread interest which his daring exploits aroused, and the definite information he brought back, we will give in the next chapter some further details of the scientific value of his journeys before we proceed to discuss the limitations of aeroplane flight.

As a matter of fact the startling scientific significance of Professor Piccard's ascents into the Stratosphere have been largely obscured by the common knowledge that new altitude records had been achieved. Altitude records are all very interesting in their way. but it is obviously absurd to imagine that the everyday life of the human race would be in any way affected by the fact that Professor Piccard had succeeded in flying over 2 miles higher than any other human being.

It was primarily a desire to study the behaviour of the mysterious cosmic rays emanating from interstellar space that prompted Professor Piccard to undertake his epoch-making ascents into the Stratosphere. A short description of what is known regarding these mysterious rays is therefore necessary to appreciate the value of his investigations.

Without going into technicalities as to how these rays were first discovered, scientists to-day seem to be agreed upon just one point, namely, that the rays come from somewhere outside the earth and do not originate within the earth itself.

No one knows exactly what cosmic rays are. There are three schools of thought: (1) that of Professor Millikan, their original discoverer, who claims that they are "hard," fast rays of the gamma sort, given off in the disintegration of radium; (2) that of the great German investigators, Bothe and Kolhorster, who claim they are fast corpuscles, like electrons; and (3) that of Professor Compton, who advances the view that they may be protons, or bullets of light.

The remarkable fact regarding these emanations is that they are hundreds, probably thousands, of times more powerful than X-rays, and that they are found everywhere. A couple of inches of lead are sufficient protection for radium rays, but cosmic rays pass with ease through 18 solid feet! They are found hundreds of feet beneath the surface of a lake, and on mountain tops. And what is even more remarkable, the radiations, which appear to come from the sky, come from all directions at once.

It was thought for a time — since water at great depth stops the radiation, and the earth's atmosphere absorbs them measurably- — that the higher skyward one went the stronger the effect would become.

But Professor Piccard, having risen to a height of over 10 miles into the stratosphere, expecting the rays to increase in intensity as he rose higher and higher, found neither a greater nor a constant increase in their intensity, and there was no noticeable directional effect.

As a result, the scientists are now more confused than ever. It is definitely known that there is such a thing as a cosmic radiation of powerful rays, but where they come from, and from what direction, whether from other stars or from within our own planetary system, is still an unsolved mystery.

The importance of definite information in regard to these questions cannot be too greatly emphasized, for most scientists now agree that these rays provide the power which breaks down the atoms of various elements on the earth.

If this be true, and the cosmic rays could be harnessed and trapped, not only would the transmutation of elements be achieved, but the almost inconceivable stored-up energy contained in the atom might also be released and used for power purposes. A fuller description of the wonders of atomic energy, with special reference to its application to astronautics, appears in a later chapter.

As an indication of the colossal power which might thus be released for the benefit of mankind, it is calculated that there is sufficient atomic energy stored up in a cup of water to drive a modern liner across the Atlantic!

In this connection, too, it is interesting to note that Sir James Jeans's theory that the whole universe is running down is based on his belief, now largely disproved by Piccard, that cosmic rays owe their origin to the annihilation of matter.

Another important scientific discovery made by Professor Piccard was that of the extreme variations in temperature in the Stratosphere, again due, it is thought, to cosmic ray action. Piccard is of the opinion that our atmosphere, being a dense medium, acts as a transforming agent, and that the cosmic bombardment may be of an entirely different nature from any with which we are acquainted. We know that the earth and the sun are separated by a vast vacuum, and that heat cannot be transferred directly through a vacuum. In other words, the sun's rays are not hot in themselves — they are not "heat rays" — but depend for their effect on some unknown transforming action of the atmosphere, whereby they are converted into heat.

In the aluminium gondola in which Professor Pic-card's journey was made, an inside temperature of 104 degrees above zero Fahrenheit was at one time observed, with an outside temperature of 76 degrees below. This tremendous extreme in temperature suggests a source of thermal power which may one day be harnessed for the service of man.

But the more immediate practical advantage to be gamed from a knowledge of the Stratosphere lies in its use as a stratoplane highway. Stratosphere planes, that is, aeroplanes specially constructed for flight above a minimum altitude of 10 miles, have already been constructed at Dessau, Germany, under the auspices of the German Scientific Union, aided by the German Ministry of Transportation, and- also in France. These stratoplanes will have variable pitch propellers, supercharged motors, and hermetically sealed cabins, as well as a far larger wing-spread and greater power than ordinary planes. At low levels huge wing-spreads are impracticable on account of the resistance of the denser air. consequently telescopic wings are necessary so that they can be extended to a large area in the Stratosphere, and retracted when travelling at ordinary levels.

The advantages to be gained from travelling in the Stratosphere will be very great.

Transatlantic fliers, to-day, for example, have to contend with variable treacherous winds, rising at •* times to gale and hurricane force, fog, sleet, ciouds, lightning, and formation of ice on the planes. It must be obvious that a constant reliable service under these conditions can never be attained.

The Stratosphere flier will escape all these troubles, and because of the low frictional resistance in the Stratosphere (one-tenth that at ground level), it will be easier for him to attain speeds of 300-400 miles per hour than one-third of these rates in lower levels.

He will not be endangered by the formation of ice on the planes, notwithstanding the intense cold, since there is not sufficient water vapour in the Stratosphere to cause a deposit on the metal. He is above all clouds, and even though it may be impossible for him to see the earth below, the heavens above, by which he can navigate, will always be clear and unobscured. In the thin air of the Stratosphere the sun will be visible at all times between rising and setting. The principal stars and planets will also always be visible to the naked eye, and there need be no fear of getting off his course at any time of the day or night. The horizon, too, will always be visible, and with suitable radio-landing beacons there should be no difficulty in finding any desired airport. "Blind flying" will prevail only during ascent and descent, and the course, once the Stratosphere level is attained, will be set by the heavenly bodies.

Prior to Piccard's flight it was always believed that a wind constantly blowing to the east existed at high levels, owing to the earth's rotation. Piccard found this was not the case, and that at different levels different strata of winds in various directions were to be found. He is of opinion that in the Stratosphere high-speed winds of constant velocity will always be found, and that the pilot will be able to select with certainty, and at all times, the altitude and wind most suitable for his particular journey from beginning to end.

Summing up, we see that the much discussed Stratosphere is the region of the atmosphere above the 10 mile level. That it is free from clouds, storms, snow and ice, with no seasons or climatic change, and has a constant temperature for a given locality throughout the year. As such it is the ideal medium for aerial traffic, and it is safe to predict that within a very few years it will become the world's highway for passenger-carrying stratoplanes, with regular twelve hour services connecting the continents of the world.

Later on the rocket plane, taking one hour to journey from America to Europe, and three hours from America to Asia, will take the place of these stratoplanes, but for the immediate future the task of aero-engineers and aviators will be the conquest of the Stratosphere for purposes of aeroplane flight.

In justification of the first part of this statement we will now proceed to ascertain the limitations of aeroplane travel in the Stratosphere or at any level.

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Like most inventors, however, he was handicapped for funds, and in 1924 he tried to finance his researches by the publication of a book on the subject. It was not until four years later, however, that he managed to build his "rocket-propelled car," and in April of that year it made its first run, which turned out to be a success.

In the next month he sent it careering round the famous Avus motor-track to the astonishment of thousands of Berlin residents who had gathered to witness the experiment.

The vehicle was driven at terrific speeds by the explosion, at regular intervals, of rockets built into the back of the machine. The acceleration powers, too, were amazing.

Herr Max Valier afterwards applied his invention to boats, sledges, and aircraft, and to minimize danger used a petroleum mixture for the rockets' explosive instead of gunpowder.

It was while further improving on the type of rocket that the inventor met his death in 1930, being fatally injured at a Berlin chemical works following the explosion of the rocket with which he was experimenting.

Another distinguished German experimenter and enthusiast in rocketry is Fritz von Opel. At Frankfort, in 1928 von Opel fitted a racing car with 12 ejection tubes on the rear of the vehicle, and within 2 seconds of the start attained a sj)eed of 62 miles per hour!

Among other scientists experimenting with this new method of propulsion was Herr Reinhold Tiling, who constructed his first rocket plane in April, 1931, and subsequently achieved remarkable results with scale models of the craft. But as in the case of Herr Valier, death again intervened in the experimental work, and in October, 1933, Herr Tiling's laboratory blew up, killing the inventor and his assistants, Fraulein Buddenbohmer and Friedrich Kuhr.

In 1932, in America, the only rocket car in the world built to take curves, and to compete with motor-driven racing cars appeared on the track at Wichita, Kansas.

This car being built of aluminium, was surprisingly light, only 1600 lb. in weight, and was propelled entirely by explosive rockets. The rockets were set off in groups according to the speed required and consisted of 32 in all. The explosions took place in tubes of the strongest steel, ordinary storage batteries furnishing the current to fire the ignition fuses. The rockets were discharged in series of 2, 4, and 10, and were situated on the sides, underneath, and at the rear of the machine in the form of a cross, the stem of which contained 12 tubes and the arms 4 each.

The machine was designed to use 2 lb. rockets, but in the exhibition race referred to only 1 lb. rockets OOOOOOOOO were used. Even so, the car travelled round the course at a speed of nearly 50 miles per hour. With full power, a speed of 115 miles per hour was attained. The rockets were charged with gunpowder mixed with five other chemicals.

It must be realized that whilst these experiments are valuable in developing rocket propulsion in its early

Fig. 3. Rocket Plank
Courtesy : "Science and Invention"

In the first place, the rocket, for full efficiency, must be applied to a vehicle designed to travel at least 600 miles per hour or more; and, secondly, the exhausts from the rockets would project (say) 10 or 12 ft. from the rear of the vehicle, and these gases, even if they were not of a poisonous nature, would, nevertheless, be ¦ dangerously hot and inflammable to anything touched. They would in fact be comparable, if the fuel used were oxy-hydrogen, to a jet of superheated steam!

The application of rocket propulsion to ordinary type aeroplanes offers much greater potentialities, both as regards providing a valuable means of future highspeed travel, and also as an auxiliary and preliminary to space flight proper.

In 1928, the Rhon Rossittengesellschaft constructed a rocket glider which successfully flew for a distance of about a mile. Some little time later the Raab-Katzenstein Aviation Company, Berlin, built a rocket plane but the attempt proved unsuccessful and further efforts in this direction were abandoned. These attempts were made with powder fuels, the use of which, at that time, wras undergoing severe criticism on account of instability. At the present time Russia has made very great progress in this form of development of rocket propulsion, by using liquid fuels, and according to recent announcements from Moscow it is expected the first passenger-carrying rocket plane will make its appearance towards the end of this year (1935).

A simple illustration of the shape and form of the first rocket plane is shown in Fig. 3. The novelty of the design is apparent, as it would appear to consist of an aeroplane of ordinary shape driven in the reverse direction!

It yet remains to be proved whether such machines will actually fly, and great credit will certainly be due to the aviators bold enough to undertake the first trial flights.

Nevertheless, this form of air flight opens up very great possibilities, especially for war purposes, as will bo described later on. when we consider the uses to which reaction propulsion could be put for military purposes.

Another development of reaction propulsion which opens up big possibilities for the future consists in its application to a new kind of mono-rail train.

With gravity start and stop similar to scenic railways, an almost immediate speed of 100 miles an hour is obtained by the gravity start alone, and this speed is afterwards accelerated by continuous or intermittent rocket motors to any desired speed compatible with safety. Speeds up to 600 miles per hour would be thus obtained within three minutes of the start, and neutralized at the end of the journey by ordinary braking methods supplemented by the climb against gravity at the terminal station, which would be elevated to the height of a modern "sky-scraper."

The objections applicable to motor-cars would not apply to a rocket mono-rail train, since the rocket motors being situated in the last carriage of the train would have an unimpeded outlet for their blazing exhaust, and the public would not have access to the rail track. A journey from London to Brighton by rocket monorail would occupy 12 minutes !

In experimenting with rocket motors using liquid fuels, whether for use with land vehicles or for the passenger or mail-carrying rocket, one of the principal difficulties met with is the tremendous rate of acceleration which such fuels give at the start. It will be recollected, for example, that von Opel's rocket car attained a speed of 62 miles an hour within 2 seconds of the start. It will be agreed that a start of this kind is far too rapid to be comfortable!

In the case of the rocket proper, the difficulty can be largely surmounted by using a catapult for the start,

Fig. 4. Obebth Two-stage Rocket
Courtesy : "Wonder Stories"

The first method consists of a rocket built in two or more stages, the first stage being a relatively low-power engine for use in the lower parts of the earth's atmosphere, and the second stage, or subsequent multiple stages, of increased power for use in the higher and more rarefied regions.

The above diagram shows a model Oberth two-stage, high altitude rocket, designed to overcome the difficulty of a too rapid acceleration at the start.

As will be seen from the diagram, this rocket consists of two parts. The lower part, which is set off first, uses a relatively low-power fuel, consisting of alcohol and oxygen. The upper part, on the other hand, uses one of the most powerful fuels known to rocketry, viz., a mixture of oxygen and hydrogen. The nozzles shown are the exhaust nozzles of the used fuels.

The second method, invented and patented by Professor Goddard in 1931, consists of a mechanism combining the principles of the rocket and the turbine, and is known as a turbine rocket.

For speeds of 600 miles per hour or more, the rocket engine is the most efficient form of propulsion known to science, but for lower speeds than this, and in dense atmosphere, the ordinary aeroplane propeller is highly efficient but soon loses its efficiency as the air becomes more and more rarefied.

In the arrangement devised by Professor Goddard, the rocket blast at the beginning of the trip would be directed through turbine blades to propellers, the turbine rotor and propeller being combined in one unit.

This drive would be used for the start and also for travelling through the relatively dense atmosphere close to the earth.

Upon reaching the higher altitudes the propeller turbines would be separated, thereby allowing the propulsion blast to pass between them, and the rocket would be driven by direct reaction propulsion alone. In this way the two best known forms of air and space propulsion are used under conditions most favourable to each.

We will now review the progress actually made in the construction of flying machines driven by reaction propulsion alone. Such machines have hitherto taken the shape or form of a glorified rocket of cylindrical shape.

It will be recollected that at the commencement of this book it was stated that the efforts of rocketers all the world over were directed in orderly sequence as follows —

1. The construction of small altitude rockets to make trial flights in the upper reaches of the atmosphere with a view to obtaining scientific data of the conditions existing there.

2. The construction of rockets carrying mails and commercial traffic between the capitals of Europe, the rocket and its load landing by parachute.

3. The construction of a passenger-carrying rocket, whence in the normal course of scientific progress, the passenger-carrying rocket ship would ultimately be reached.

As regards (1) progress is as yet slow. Although rockets have actually ascended to a height of 6 miles, there is no record of a rocket reaching the Stratosphere.

The latest model produced is one invented by Heinrich Zucker of Berlin. It is 16 ft. in length, weighs 220 lb., and powered by 12 subsidiary rockets. It is designed to attain a sjjeed of 600 miles per hour, and to ascend to a height of 15 miles.

Toy models have actually flown distances of 3 to 5 miles, and the very considerable power they have developed have encouraged experimenters throughout the world to continue in their efforts to tame the giant that slumbers in the rocket.

Although the public demonstration of Stratosphere rockets may seem disappointing, it must be borne in mind that we are still in the very first stage of rocketry. Most of the experimental work already done, or in progress, is not made with actual rockets but on what technicians call the "proving stand" — a set-up, on which rocket motors can be tested as to "lift" and efficiency without going to the expense of building the entire rocket.

As a result of experiments of this kind it has been found that the proportions between the weight of the fuel and that of the rest of the rocket are so great that over 90 per cent of the available space is needed for fuel, leaving only 10 per cent for cargo. It is for this reason that no really big rockets have yet appeared in public, since such ventures would be obviously unprofitable.

The progress as regards (2) — mail carrying rockets — is more heartening.

The history of rocket mails begins in February, 1931, when an Austrian, Friedrich Schmiedl of Gratz, established the first scheduled rocket postal system between the Schockel and Radegund, near Gratz. Schmiedl employed powder mixtures varying their quantity so that the fuel would be exhausted when the rocket arrived over its destination. A parachute wras then automatically released which landed the mails safely, the whole journey taking as many minutes as it previously took hours by ordinary methods. The stamp (postmark) " Raketenf lugpost Schmiedl" is registered at Berne.

In April, 1933, a dirigible rocket, complete with "air mail," made its first appearance in public. The experiment, w7hich was conducted at Cuxhaven, ended dismally. The inventor of the rocket used on this occasion was Herr Zucker. It was to have flown to release a mailbag attached to a parachute, then to turn round, and return to its starting place. The initial programme was far too ambitious. Instead of doing any or all of these things it somersaulted in the air soon after the start and then crashed to earth!

In India experiments with mail-carrying rockets are being actively conducted by the Indian Air Mail Society, Calcutta. One of their recent trials took the form of an attempt to convey mails by rocket from a ship at sea to shore, and vice versa. Up to the present their efforts have not proved successful.

In England, the first public trial of a mail-carrying rocket was made in 1934. Full details of this trial appeared in the Daily Express, London, under date 6th June, 1934.

According to this report we learn that the inventor, Herr Gerhard Zucker, another German rocket experimenter, first attended the International Air Post Exhibition held in London in May, 1934, where he met Lord Londonderry and Sir Kingsley Wood, the Postmaster-General, both of whom showed considerable interest in his invention.

After negotiations with the Post Office the first trial flight was made at dawn on 6th June, 1934, when 1300 letters were conveyed nearly 2 miles in an aluminium rocket, and then taken out and handed over to the nearest Post Office for conveyance to their ultimate destinations.

A specimen letter sent by this rocket mail was franked with Air Post Exhibition stamps, overprinted with the words

Rocket Post — First British Flight

This trial was me nisi, ox a series piaimeu 10 uumimttte in regular mail rocket services in England, and although it will seem of little practical importance to many j)eople, it may, as a matter of fact, mark the beginning of a revolution in postal transport. Most epoch-making inventions have had to start from similarly crude and relatively trivial beginnings. In this respect Herr Zucker's programme bears a remarkable resemblance to the earliest experiments in wireless telegraphy.

His next rocket flight took place in July, 1934, between the Isle of Lewis and the Isle of Scarp off Western Scotland. About 50 letters were enclosed in the mail compartment, including one addressed to King George. Upon ignition the rocket exploded with great violence, destroying itself, the letters, and the launching rack. On 19th December, 1934, Herr Zucker made a further attempt between Lymington, Hants, and the Isle of Wight. The rocket, containing 600 letters, was turned by the wind, and fell about a mile and a half away. He next proposes rockets of larger and more powerful construction for a flight between the Channel Islands and France, and from England to France across the Straits of Dover.

As a preliminary to the Dover-France flight, the authority of the French Air Ministry was obtained in November, 1934, and it is anticipated that an early attempt will be made. On this occasion Herr Zucker expects to convey a mail consisting of 12,000 letters !

If successful in these demonstrations a British syndicate will be formed to obtain a licence for the conveyance of mails by rocket, and a regular rocket mail service will be inaugurated across the Straits of Dover between England and France, followed by a similar service between England and Ireland.

The extraordinary feature of these mail rocket services is the amazing saving m uansn wines ueuween a rocket service and services by the present method of conveyance by sea. Herr Zucker estimates the time of transit by his rocket mail to France across the Straits of Dover, a distance of 21 miles, at one minute, and from England to Ireland at three minutes!

It cannot be denied, in view of these remarkable estimates — reducing hours to minutes- — that this method of conveying mails has distinct possibilities of very great importance. And it seems reasonable to think that further progress to a practical conclusion is merely a matter of continued experiment and trial.

Finally, we come to (3) the successful construction of a passenger-carrying rocket.

We print in the next chapter a verbatim extract from a prominent London weekly newspaper, which gives details of the long awaited, epoch-making achievement so necessary to set the seal of reality and practicability upon the science of Astronautics.

Unfortunately, neither members of the Press nor scientists of repute were present at the amazing passenger-carrying flight described, so the authenticity of the account must be accepted with reserve. It should be mentioned that two London daily papers failed, a few days later, to obtain confirmation of the ascent, but this does not necessarily make the report unreliable, since the conditions of secrecy under which the report was in all probability obtained would account for any failure to obtain confirmation through the usual public channels.

In Germany all stratospheric rocket experiments are in charge of the head of the Department of Ballistics of the Armaments Section of the Reichswehr Ministry, and considerable secrecy is maintained regarding them. Everyone in Germany who makes any stratospheric rocket discovery of any importance and requires capital to exploit their ideas must first address themselves to this Department. Foreigners who make similar discoveries must report them to this section of the Reich-swehr, and may be granted German naturalization at once.

Not only are the details of the ascent given in the next chapter wonderfully realistic, but the times and distances quoted are mathematically correct according-to the general principles of Astronautics. It is extremely unlikely, if the flights were a work of "journalistic imagination," that the writer would have had the foresight and ability to avoid falling into a trap of this kind.

Several months later an American science magazine gave details of the same ascent, and backed it by giving the names of two prominent American rocketers who were able to confirm it. And in Nash's Magazine for May, 1935, in an article entitled "Space Explorers," the author not only confirms the flight but records a personal introduction to the flier !

On the whole the author is inclined to regard the report as accurate, but readers must form their own opinions. There is little doubt, even if the report is imaginary, that sooner or later man's conquest of aerial flight by rocket will be accomplished, and a first ascent of this kind will mark an epoch in Astronautics comparable with that made in " heavier-than-air flight" by Wilbur Wright in 1903.

It is difficult to realize, nowadays, now that the miracle of aeroplane flight is so much a part of our daily life, the disbelief, often amounting to downright ridicule and contempt, which the general public had for " heavier-than-air flight" prior to the first successful flight.

Only nine days before Wilbur Wright succeeded, another aeroplane inventor, Professor Langley, made an attempt and failed badly. The Press of the day jibed without mercy at the unfortunate inventor, stigmatizing his attempt as "Langley's Folly" — an expression which lives to this day.

Little did the Press, or general public, dream that Wilbur Wright's first flight of only 852 ft. would lead

Fig. 5. Experimental Rocket
Courtesy : " Popular Science Monthly."

In comparison with Wilbur Wright's success the flight of a passenger-carrying rocket skywards for a distance of 6 miles, over a period of 10 minutes 26 seconds, described in the next chapter, would appear to be an achievement relatively far greater, since rocket flight offers such infinitely greater possibilities to mankind.

On page 77 is a drawing of an experimental type of rocket as used for test flights. The liquid oxygen tank is in the nose, and the gasoline in the tube at the side. The fuel feeds at the bottom, and burns near the centre of the chamber, the gases escaping at the rear.

"A sensational secret demonstration of the practicability of the rocket principle applied to flight was made here last Sunday, when Herr Otto Fischer was shot 6 miles into the air within a 24 ft. steel rocket and returned to earth safe and sound, though shaken.

"The pilot who risked his life in this experiment is brother of the designer and constructor of the rocket, Herr Bruno Fischer.

"Owing to the disastrous result of a similar experiment made on Rugen in the spring of last year, when the oriqinal inventor was killed, the demonstration was made under the cover of absolute secrecy , under the auspices of the Reichswehr, the German War Ministry.

"The inhabitants of the island knew nothing of the proposed experiment, and no members of the Press were called in to witness it.

"For some months the two brothers had been working day and night in Barmbeck, a small village near Hamburg, to complete the rocket, Bruno Fischer having been an assistant in the building of the first projectile.

"When the rocket was completed it was transported to Rugen with the greatest secrecy.

"On Sunday morning at 6 o'clock, Otto Fischer shook hands with his brother and the small group of Reichswehr officials present to witness the experiment, and crawled through the small steel door.

"Bruno Fischer and the three officials then retired to a small hollow in the ground about two hundred yards away, and Fischer closed the switch that sent the rocket on its journey.

" There was a blinding flash and a deafening explosion, and the slim torpedo-shaped body was gone from the steel framework in which it had rested.

"A few minutes later it came into sight again, floating nose upwards from a large parachute that had automatically been released when it had begun to descend.

"As it drifted nearer, the steel fins on the outside of the body could be seen moving as its pilot manipulated the rocket so that it would land on the island.

"A few seconds later it came to rest on the sands a few yards away, and Fischer crawled through the door of the rocket, white and shaken, but smiling triumphantly. The journey through space had lasted 10 minutes 26 seconds.

" 'It was a tremendous sensation,' he said to the men wno naa rusnea torwarci to congratulate him.

"'When the rocket left the ground I was conscious of a deafening roar, and an unbearable weight seemed to be crushing me against the floor of the rocket. Then I lost consciousness for a moment, due to the tremendous acceleration, which drained the blood from my head.'

"'When I came to my senses and looked at the altimeter before my face it flickered at 32,000 ft. — a fraction over 6 miles — and then began to drop rapidly. I had completed my climb and was descending.'

"'Peering through the little glass window in the side of the compartment, I could just see the tip of the parachute billowing above me.'

'"The next thing that occupied my attention was the tremendous heat of the asbestos floor on which I was standing. The reason was that the rocket had merely been propelled about two hundred feet by the initial explosion, and had been driven the remainder of the distance by the rockets in its tail, which had been released automatically at timed intervals.'

'"The manoeuvring of the rocket to land on the desired spot was a ticklish business. This was mainly accomplished by slanting the fins to the wind and pulling the parachute ropes that ran into my cabin so that the rocket would sideslip towards the landing spot.'

'"Needless to say,' Fischer concluded with a wan smile, 'I'm very glad to get back safely.'

"Although it was hoped that the rocket would reach a height of over 10 miles, the brothers are completely satisfied with the result of the experiment, and further experiments will be conducted by the German War Ministry, who have purchased the complete plans of the rocket."

Marshal Foch is said to have prophesied that in the next war "the whole nation will find itself on the firing line !" It is possible that this remark was grounded on the exploits of Big Bertha in the last war, since the problem of modern warfare has now resolved itself into that of destruction at the greatest distance. And as a means for an attack on a distant foe the rocket stands out as having the most far-reaching potentiality.

For the rocket carries its own fuel, and its motion continues until that fuel is exhausted and its momentum is lost.

And if to the rocket motor there is attached a nose filled with high explosive, gas, disease germs, or anything deadly that modern science can create, we get a self-propelling shell whose trajectory vastly exceeds the wildest dreams of the ballistician.

Figure 6 shows a cross-section of a type of rocket adapted for warfare, upon which experiments are being made. The larger portion of its bulk is taken up with fuel, consisting of liquid oxygen and gasoline. This mixture gives a very high pressure, and, consequently, high velocity of propulsion. Fins are provided to keep the rocket on its course, but some form of gyroscopic control could no doubt also be incorporated.

Such a rocket would not only propel shells to distances utterly impossible by any form of artillery, but

Fig.6. Rocket Shell
Courtesy : "Science and Mechanics"

Hitherto long range artillery has been used principally against opposing armies at distances of 5 to 25 miles.

The rocket shell, catapulted in the first instance for launching, would rise, gaining headway at each second, and descend at any distance from 500 miles onwards!

As a consequence, London would be in range from both the German and French capitals, Paris from the German border, and Berlin from the Rhine, whilst Switzerland might find herself arched with a mutual bombardment between France and Italy!

The assailants would fire upon known objectives by map, just as modern long range artillery is directed upon invisible targets.

Batteries shooting rocket shells into the heart of an enemy country could be built by the thousand and fired with the rapidity of small calibre artillery. For rocket shells of this kind would be gun and shell in one, and wTould not require any heavy ordnance to shoot them.

Originally it was intended to control and direct these rocket shells by gyroscopic means, so that they should carry themselves unerringly to their objective, but in view of the enormous strides made in wireless the latest designs embody wireless control. Ultra short radio weaves would be employed to control and operate elevating and directional fins forming part of the rocket. The principal difficulty of ascertaining the position of the rocket once it had vanished from view has now been solved by fitting each rocket with a small transmitting apparatus, the constant waves from which at a predetermined frequency can be received by radiogoniometric stations installed in the vicinity of the firing point. By triangulation or other methods these stations would be able second by second to determine the exact position in space of the rockets whilst in flight, and by the aid of their transmitters so to control and direct them as to cause them to fall at any desired locality in the enemy's country.

As is already known this principle of radio control has already been tried with battleships, submarines, and aeroplanes, and it is equally suitable for rocket control.

Another equally appalling factor in the "next wrar" would be the adaptation of rocket propulsion as an auxiliary means of propulsion to a bombing aeroplane.

Rising to their normal "ceiling," such planes, known as rocket stratoplanes, wrould, by the aid of the rockets with which they would be fitted, then "shoot" themselves to a height of 30 miles or more. At this great height, where the air resistance is almost non-existent, speeds of 3000 miles per hour could be attained, and they would be not only immune from attack by opposing planes not using auxiliary rocket propulsion, but beyond the range of audibility and visibility from land observers.

Flashing thus invisibly over the enemy's country at inconceivable speed, they would at the critical moment switch off their motors and swoop suddenly and silently down from the skies upon an unsuspecting city, loose their loads of deadly projectiles, and escape just as swiftly as they came.

Cruisers and other battleships could be also quickly and readily converted into "rocket ships " by fitting trough-like catapults on the backs of the existing guns. Against an invading fleet so armed with long range rocket shells, the heaviest of coast defence guns and naval guns would be as useless as clubs and spears.

The extension of battle areas, both naval and military, would be also as revolutionary as that which followed the introduction of the modern rifle and aeroplane. Just as the much vaunted splendid "insularity" of England now no longer exists, and its frontier is the Rhine, so in the course of a very few years' development in rocket stratoplanes would the "insularity" of the United States be a thing of the past, and her frontier be Japan.

There is no possible doubt that militarists all over the world, with the possible exception of England, are fully alive to the tremendous possibilities of the rocket in modern warfare, and in the next war it will inevitably follow that rocket propulsion will be developed to the fullest extent of its destructive powers just as happened in the Great War with the aeroplane.

In this connection it may be mentioned that Professor Hermann Oberth, the world's greatest authority on the rocket, recently stated before a meeting of scientists in Vienna his belief that the War Offices of every nation of importance were already hard at work developing the rocket for military purposes.

In Germany, for example, German scientists are busily engaged in seeking a means of destroying cities hundreds of miles away by means of stratospheric rockets.

Nominally, the experiments have been made under the pretext of reaching Mars, or the moon, or for a rocket for rapid postal services. Nevertheless, all progress made in this direction has its specific aj)plication as a new weapon of war. For years past experiments under the direction of the Reichswehr Ministry have been made with stratospheric rockets at Meppen, where the first tests with "Big Bertha" were carried out, at Stolp on the Baltic coast, at Britz near Berlin, and at Munich.

It is almost beyond belief that in England to-day nothing is officially known about rockets. At least that is the inference to be gathered from a statement made by the Air Ministry only a few months ago, when in reply to a request to investigate and experiment with rocket propulsion the answer given wTas that "they saw no reason to regard the rocket motor as a serious competitor to the tractor screw!" Competitor, mark you! What earthly competitive chance, as a means of propulsion, has the tractor screw against a rocket in a Vacuum or in a highly-rarefied atmosphere ?

How many people in England to-day realize that far from enjoying a splendid insularity, the gap in the nation's defences is as wide as the heavens themselves ? Who with any gift of vision can fail to be filled with apprehension when they gaze up at the sky, dreading the day when it will be filled with aerial messengers of death with their resultant wholesale massacre of innocent women and children and non-combatants ?

These facts are unpleasant to face — especially for those who hope to see the rocket harnessed to peaceful vehicles that will annihilate distance and possibly achieve the exploration of interstellar space.

Whether mankind of the future will bitterly regret that the rocket has ever been invented remains to be seen. To the author it seems to be one of the creations of the human mind which will serve as a test of man's right to inherit the earth. For good or evil, its powers, like the principle upon which reaction propulsion is based, are "equal and opposite."

Twenty years from to-day we may be shooting across oceans and national borders rockets that hold passengers and articles of commerce, or deadly missiles containing poison gas, microbes, and other means for destroying human lives. Which it will be depends not upon rocket experimenters, nor upon militarists, but upon the people of the world who have to pay, fight, and suffer for all wars.

We will now leave the lugubrious subject of the use of rockets in warfare and, by way of relaxation, indulge in a "flight of imagination "• — to wit, an account of a journey by space ship from Berlin to New York.

We set out from Berlin for the rocket flying ground, a few miles outside the city. Entering the air port, our attention is at once focused on a gleaming silver metallic body, shaped like a gigantic "pear drop," which lies on the inclined plane of a large catapult worked by compressed air. This is the rocket plane "Portuna," and she is about to make her maiden trip to New York. An imaginary conception of what this ship will look like is given on page 90.

As we approach the ship preparatory to climbing up the side to an entrance lock, we note the short, stubby, retractable wings of the type already developed years before in aeroplanes designed to meet conditions of flight at different altitudes.

The extremely blunt nose of our ship terminates in an iris diaphragm arrangement, behind which is housed a propeller of the usual type, now invisible, because it will not be used until we descend at the end of our journey.

For the ascent and for the major part of the journey we require a perfectly smooth nose to our ship, but on the descent into the earth's atmosphere the iris diaphragm will be opened, thereby presenting a greater air resistance, and permitting the propeller to function so that our space ship will be able to plane down just like an ordinary air liner.

Completely encircling the propeller, in the nose of the ship, we see the tuyeres, or nozzles, of numerous rocket motors, and at the rear, we also observe other tuyeres similarly situated, but within a much smaller periphery.

Fig. 7. Space Ship of the Future
Courtesy : "Science and Mechanics"

The purpose of the stern rockets is to propel the ship ahead, and those in the bow of the ship, to retard, or slow down its forward motion. A few tubes are also to be seen on either side, the function of which is to alter the direction of flight, if necessary.

A few minutes before the start, the entrance ports are closed and hermetically sealed, and the passengers proceed to lie down in hammocks supported by heavy springs.

Then a bell rings, and we are off ! The machine leaps into the air at an angle of 60 to 70 degrees, and within 30 seconds of the start is out of sight to the numerous onlookers who have assembled to see the start.

Meanwhile the passengers are undergoing considerable discomfort. Their bodies now seem to weigh tons, and they are pressed with terrific weight against the hammocks, which give as the springs which support them elongate. A great weight seems to lie on their chests, and they experience considerable trouble in breathing. They find it almost impossible, too, to lift their arms, because of this feeling of heaviness.

Gradually, however, they become accustomed to this nasty feeling, and as the flight continues the weight gets less and less, until the time comes when they must actually cling to their hammocks to keep themselves from being bounced against the ceiling!

In about ten minutes from the start the rocket ship has attained its highest speed of nearly 4 miles a second, or some 14,000 miles per hour, and the fuel allotted for the start has now been consumed. But the rocket ship continues to rise, like a giant projectile, under the momentum it has acquired, requiring no further power.

Within half an hour it reaches the highest point of its curved path, or trajectory, at an altitude of 630 miles above the middle of the Atlantic Ocean, and now starts descending in a "free fall" towards its destination, its speed increasing in the same ratio as it was previously reduced by the pull of gravity during its upward flight.

Fig.8. Imaginary Flight - Berlin to New York
Courtesy : "Science and Mechanics"

When the machine is still 150 miles from its destination — its fall having been previously checked by the action of the bow rockets — the retractable wings, folded in the hull from the start, are extended to full span, and soon begin effectively to grip the thin atmosphere it is now entering.

Once again the passengers are pressed with tremendous force against their hammocks, because the flight of the machine is being strongly decelerated. Their bodies become heavy as lead, and breathing difficult.

At a suitable moment the retarding rockets are shut off, and the machine completes a long and graceful glide, by the aid of its wings, to NewT York, where a safe landing is as easily made as that of an ordinary air liner.

An imaginary conception of its flight is shown on page 92.

The entire journey, from start to finish, has taken less than one hour to accomplish, the distance, as the crow flies, being approximately 3960 miles!

A dream of the future ? Yes. But one which is quite within the bounds of present-day scientific knowledge, and perfectly feasible from an engineering standpoint. Thirty years of progress have brought heavier-than-air flight from a first trip of 852 ft. to "round-the-world" journeys. Who can say that thirty years of similar progress in the science of Astronautics will not conceivably make this dream of the future an accomplished fact ?

If so, I must again emphasize as strongly as possible, that it would be unfair and illogical to prejudge Astronautics or any other science at such an early stage of its development.

Usually, there are three stages in the birth and development of any revolutionary discovery or invention of this kind.

First. It is declared "impossible."

Second. When actual demonstration — often in an extremely crude and elementary fashion — is made, the leading orthodox experts declare that such an invention has no possible practical use.

Third. When number two has been proved false, the wiseacres say they knew all along that it could be done, but even now it has no commercial possibilities.

The telephone, electric lamp, wireless, and " heavier -than-air" flight have each gone through all the above stages.

Astronautics, or space flight, is only now emerging from the first stage of being declared "impossible" and entering the second stage.

Every astronautist will agree that much, very much, remains to be done, and that the amount of practical research to be carried out before even a single passenger-carrying-space vehicle is produced will be enormous.

But it should be remembered that at present the development of space flight is mainly concerned with the theoretical demonstration of its "possibility."

Where the principles involved are capable of mathematical treatment, they have already been exhaustively analysed by the best mathematicians of the day, and found to be sound.

Where, too, certain principles are capable of actual trial and proof, as in the case of parachute descents, etc., trials and experiments are constantly being made.

Fundamentally, there are four basic facts proving that space flight at relatively enormous speeds is theoretically "possible," and they are clearly demonstrable, however imperfectly they may have been described herein, viz. —

1. There is no known reason or objection why man cannot physiologically stand the strain of almost unlimited speed — provided such speed is constant.

2. That a steady rate of acceleration, within perfectly reasonable limits would enable one to attain, in a very short space of time, speeds vastty greater than any present or proposed aeroplane speeds.

3. That such enormous speeds are only possible in the most highly rarefied regions of the atmosphere, or beyond it in the vacuum of outer space, where no conceivable form of aeroplane could travel, and

4. That reaction propulsion, as exemplified in the rocket, is the only possible method, so far as present knowledge goes, of travelling in the highly rarefied regions referred to.

Once these principles are firmly established and widely known, the resource and ingenuity of experimenters and physicists of all nations will, sooner or later, succeed in evolving the necessary practical means of successful space flight. And if the progress of the world is to be measured by the agencies which bring men closer together, then Astronautics will deserve to rank as one of the highest civilizing mediums ever known in the history of mankind.

Nevertheless, it must be borne in mind that so long as the necessary research work has to be carried out at the expense of a mere handful of enthusiastic supporters, progress must be painfully slow. At the best, space flight is to-day comparable to heavier-than-air flight prior to Wilbur Wright's first flight, and as such can only be termed an expensive hobby! Most great inventions have, however, had to go through a similar phase in their career, so there is no need for discouragement on this account.

The advent of this little book on Astronautics — the first of its kind published in England — is eloquent proof of the extreme infancy of this new science. The author feels and realizes that its publication may be, and probably is, premature, and that in a sense he is as a "voice crying in the wilderness," but the more progressive of his readers may think otherwise. It is interesting to note that the British Patent Office Library, supposed to contain the finest collection of books on technical subjects in the world, holds no work on Astronautics in English. It is true that a copy of Oberth's classical work is held, but it is as yet untranslated, and lies there tucked away among a group of books labelled "Fireworks !"

Although this would indicate that Astronautics is almost unknown to the English public, and that it is classed in terms of importance with "fireworks," the author is confident that the details of the principles of Astronautics given in this book will prove of considerable interest to many, and hopes that some at least will have the vision to realize that it is a science which has vast potentialities, for good — and also, alas ! for evil, and may one day affect the future of the whole human race.

Many years ago, Jules Verne, that great visionary of the future, many of whose dreams have since been realized, gave in one of his books exhaustive details of a voyage to the moon by means of a projectile-car fired from a 300 metre cannon. We know now that this method of space travel could never be of any practical use, because no human being could survive the shock of the enormous initial acceleration. Nevertheless, the problem of a journey to the moon is of real scientific interest, and we will now deal with the problem in the light of the principles of space flight herein described.

It seems fairly certain that as a preliminary to interplanetary travel the conquest of the moon will be first attempted.

This is not so much because the moon itself offers any great possibilities, either as regards rare metals or discoveries worth the risk of the journey, as it is that it will in all probability form the first jumping off place for a visit to Venus or Mars. The force of gravity on the surface of the moon is only -161 that of the earth's gravity, and for that reason it would enable space ships to leap off into space far more readily than from the earth's surface.

Since a space ship weighing 100 tons would weigh only 16'1 tons on the moon's surface, it is probable that the moon is destined to be the outer terminus for future interplanetary travel.

As is well known, the moon is one of the smallest of heavenly bodies, although superficially it seems the largest on account of its being so close to us — its distance from the earth averaging about 239,000 miles. An aeroplane travelling at 150 miles an hour would complete the journey in about two months.

The moon revolves around the earth in such a fashion as continually to present only one side for observation. Being so close, large telescopes clearly show its mountains, ravines, craters, and plains, all of which have been mapped so thoroughly that we know almost as much about its geography as if it formed part of the earth itself.

So far as observation goes, it is generally accepted that the moon has no water, or very little, and no atmosphere. It follows then that with nothing to breathe, and probably nothing to eat or drink, that life in any form, whether animal or plant, could not exist, This, however, refers solely to the side of the moon that comes under our observation. Nothing is known of the side that is perpetually turned away from us.

For two weeks the scorching sun produces a temperature equal to boiling point, then follows two weeks of continual darkness, during which period the temperature drops to 200 or even 400 degrees below zero. This period of four weeks forms one lunar day. As a "promised land," therefore, it must be said that the moon's attractions are practically nil.

We see, then, that the initial problem is to evolve a means of escaping from the earth's gravitation for a distance of 239,000 miles, or to be more exact, to the point of neutral attraction between the earth and the moon, a point in space some 220,000 miles distant from the earth. From this point onwards, the moon's "pull" would exceed that of the earth, and a space ship would fall towards the moon of its own accord.

When we consider that the force of gravity has so far only been overcome for a trifling distance of 35 miles — obtained by means of light observation balloons — the magnitude of the initial problem of interplanetary travel becomes obvious.

Fortunately, the force of gravity varies as the square of the distance, and this is a great help so far as the amount of power required, is concerned. The fact that our proposed journey has to be carried out through the partial vacuum of the ether of outer space is relatively of minor importance, since it merely entails a machine which must be hermetically sealed, and equipped to carry its own oxygen and other machinery to make air. This is, however, a problem already solved by submarine engineers.

To illustrate by way of example, the great reduction in weight which follows from the fact that the force of gravity varies as the square of the distance, a few facts and figures will be of assistance. If, for example, the pull of gravity on the earth's surface — approximately 4000 miles from its centre — be taken as 1, the pull 4000 miles away, or twice this distance, would be l/4th, at 8000 miles distant (or three times this distance) it will be l/9th, at 12,000 miles l/16th, and so on. This means that a man weighing on earth (say) 150 lb., would weigh only 37-| lb. at a distance of 4000 miles, 16-| lb. at 8000 miles, and so on, less and less, until at a distance of 48,000 miles (twelve times 4000) he would weigh only 1/144th of 1501b., or slightly over 1 lb.!

Again, it must be borne in mind that once clear of the earth's atmosphere (say 200 miles), there would be no frictional retardation and the only thing preventing a space ship from maintaining, without power, its present speed, would be the retardation of gravity in the proportions given above.

It would be as well, perhaps, if we here state an axiom of gravitational pull with which few people are acquainted. It is a popular fallacy, even among educated people who have no scientific knowledge, to imagine that the greater the height from which a body falls, the greater the velocity will be with which it reaches the ground. If this were true, one would only have to go far enough away into space and drop a body towards the earth, when it would, provided it did not encounter any obstacle en route, reach the earth's surface with a velocity greater than the speed of light — which modern science declares impossible.

As a matter of fact, the theory of gravity gives a definite denial to this idea, and it is possible to verify mathematically that such a body, "falling free" in space, could never reach the earth at a greater speed than 11,180 metres (7 miles) per second.

It is logical, therefore, to say, that if a body leaves the earth's surface at a speed greater than 7 miles per second it would, if free from the gravitational attraction of any other bodj, travel on for ever and ever, and so return to the infinite. In connection with the speed we have mentioned, it is interesting to note that mankind is already travelling over 18 miles per second — in our journey around the sun — and is not conscious of the fact!

We have seen that in a journey between the earth and the moon, the earth has a "pull" on the moon, just as the moon has a "pull" on the earth, such "pulls" varying directly in proportion to their masses, and inversely proportional as the squares of the distances. These "pulls" equal and neutralize each other at a distance approximately 220,000 miles distant from the earth, or 20,000 miles from the moon. At this point a man would have no weight at all, and space for him would have no "up" or "down!"

The initial critical speed of 7 miles per second, above referred to, is, of course, the speed of a projectile, as from a gun, and is at its maximum at the start. No human being could stand an immediate acceleration so great as this, and no conceivable form of cushioning could ever get over the difficulty. For this reason the travellers in the projectile-car proposed by Jules Verne would have been killed immediately.

It is one of the great assets of rocket space ship flight that the rate of acceleration can be regulated to any degree, just as the speed of a petrol engine is controlled. The power can be expended gradually, and in the case of the exponential rocket, the compartments get smaller and smaller, as the combustion goes on, so that this necessary minimum velocity of about 7 miles per second is not attained until a height of 1800 kilometres (1117 miles) is reached, which is well clear of the dangerous atmospheric zone of about 200 miles, and precludes any danger of burning up before it has been passed through.

We see then that the problem has passed out of the hands of the ballisticians into the hands of the astro-nautists. For no matter what may be the longest range realized by the methods of modern artillery, or any conceivable range of the future, it is quite beyond the bounds of possibility that any human being could ever survive the shock of the initial critical minimum velocity of 7 miles per second, necessary to take a projectile space ship clear of the earth's attraction.

But the astronautist attains this velocity by easy stages, first leaving the earth at an initial velocity that calculations show can be safely borne, and then, gaining headway at each instant of time at a rate of acceleration of not more than 32 ft. per second per second, attains a speed equivalent to the desired minimum of 7 miles per second at the start in about 20 minutes.

For a journey to the moon it is not possible to apply the ordinary simple gravitational formulae S = ¹/₂ at and because the problem is complicated in various ways. Not only is the "pull" of gravity constantly varying, as the distance from the earth grows greater, but the weight of the space ship becomes less and less as the fuel is consumed. Also, the fric-tional resistance of the earth's atmosphere becomes less and less as the density becomes less, and there are variations in centrifugal action and other factors to be taken into consideration. The exact figures can, however, be worked out by the aid of higher mathematics, but the formulae would be out of place in a small book of this kind.

The following description of a trip to the moon is given by way of example, and is based on an exhaustive mathematical analysis of all the problems involved.

Let it be assumed that it is possible to impart to a vehicle weighing 1 ton, an acceleration of only one-tenth that of terrestrial gravity (in other words, the application of a constant force of 1100 kilograms).

Our imaginary space car will acquire a greatly accelerated rate of ascension, so much so, that at a distance of 5780 kilometres its speed will have risen to 8180 metres a second (over 5 miles per second). This result will have been attained in 24 minutes and 9 seconds from the start, and being well in excess of the requisite initial projectile starting velocity of 7 miles per second at the earth's surface, previously referred to, the propelling force can be shut off. and the voyage continued under the momentum of the velocity acquired.

Although we are now in a position to "coast" the remainder of the journey to the moon, it must be borne in mind that we are still subject to the earth's gravitational "pull," which, from now on, is acting as a constant brake, decreasing in effect as our distance from the earth grows greater. Our velocity is therefore steadily diminishing, and by the time we have reached the zone of equal attraction, approximately 220,000 miles from the earth, where the "pulls" of the earth and moon equal and neutralize each other, our speed will have been reduced to 2300 metres a second (about 1¹/₂ miles).

From now on, the moon's pull exceeding that of the earth, we are subject to a positive acceleration, and our velocity will rise to 3060 metres a second (about 1.9 miles). At this instant the rocket ship will reach the moon's surface, but as we have no desire to "crash" at this terrific speed, we must previously have taken steps to decelerate.

Owing to the fact that the moon has no atmosphere, a parachute is out of the question, so our only alternative is to use retarding rockets, fixed in the bow of the ship.

We know that similar rockets gave us a positive acceleration sufficient to overcome earth's gravity in 24 minutes and 9 seconds, and since the lunar attraction is seven times less intense, we must apply the braking action of our retarding rockets 3 minutes and 46 seconds prior to our estimated time of arrival, and this application must start at a distance of 250 kilometres (155¹/₄ miles) before reaching the moon. The entire journey has taken less than one day!

The foregoing example is intended merely as a simple illustration of the manner in which the theoretical foundations for space travel may be worked out. Those of my readers who are interested in the exact mathematical arguments, are recommended to read the principal textbook on the subject written by Monsieur Robert Esnault-Pelterie, entitled L'Astronautique. Monsieur Esnault-Pelterie is a famous French scientist and author, and has spent 25 years on experiments and investigations in aeronautics and astronautics. His work also covers all possible hypotheses relating to existing explosives for fuel, and calculations covering all forms of theoretical rockets.

Mathematically, the problem of earth-moon travel is already solved, but actually the difficulties yet to be overcome are enormous. Even the initial stage of building a rocket which will travel without cargo to the utmost limits of the earth's atmosphere has not yet been achieved, and it is still a far cry from this to a passenger-carrying vehicle.

We will, however, complete our analysis of the whole problem by a review of some of the principal obstacles and objections which have yet to be investigated and overcome.

But once it has been demonstrated mathematically that space flying is possible, it can be taken for granted that there is no obstacle in the way of interplanetary flight that cannot be overcome by the application of scientific methods, and normal progress in invention and discovery.

Sooner or later the day will arrive when rocket travel will become an accomplished fact, but the progress will be very gradual in the interim, and will in all probability proceed along the lines already mentioned, viz.: First, an altitude rocket, containing instruments only; second, small mail-carrying rockets, graduating to a transatlantic service; third, the first passenger-carrying rocket vehicle; fourth, the inter-terrestrial space ship; and lastly, the interplanetary ship.

The first and greatest obstacle to space flying is undoubtedly that of finding a suitable propellant fuel, and for interplanetary purposes, one that, for each pound of weight, will supply 20,000,000 foot lb. of energy for each pound consumed. The most powerful fuel yet known gives only 5,000,000 ft. pounds of energy per pound at 100 per cent efficiency.

It would appear evident, on the face of it, that the fuel could not even carry its own weight beyond the earth's attraction, leaving alone a space ship, passengers, and equipment. However, by the step rocket

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The books have been grouped under the respective languages in which they are written, and brief notes have been added as to the nature and extent of the subject matter.

Nikolai A. Rynin: Super-Aviation and Super-Artillery. This work consists of a scientific study of interplanetary intercommunication, as well as the development of reactive artillery for military purposes. There are chapter's on the apparatus necessary for respiration during flight, and on the navigation and propulsion of the rocket ship.

Jacques Perlman: Interplanetary Travel. Discusses the problems of rocket flight to other planets.

Interplanetary Voyageurs. Contains the elementary principles of astronautics.

By Rocket to the Moon. Written in popular vein for children.

Hermann Oberth: Die Rakete zu den Planetenraumen. Considered the greatest and most complete work on rocketry The third edition of this work, under the title Wege zгr Raumschtffahrt, was awarded the REP-Hirsch International Prize.

Werner Brugel: Manner der Rakete. Collection of biographies of famous rocket experimenters and astronauts.

Hermann Noordung: Das Problem der Befahrung des Weltraums. A discussion of the problems of space flight in general terms. Not too technical.

Dr. Vladimir Mandl. Die Rakete zur Hohenforschung. An account of rocketry by a Russian, written in German.

Willy Ley: Die Moglichkeit der Weltraumfahrt. The first comprehensive work on the possibilities of space travel. Also contains articles by Professor Oberth, Dr. Ing. W. Hohmann, Baron Guido von Pirquet, and other great authorities on rocketry. Mr. Ley is vice-president and secretary of the German Rocket Society.

Grundrisz einer Geschichle der Rakete. A very exhaustive history of Rockets and astronautics, arranged chronologically in skeleton form.

Dr. Eng. Eugen Sanger: Raketen Flugtechnik. One of the latest books on rocketry published at Munich in 1934, Dr. Sanger belongs to the Technical High School of Vienna, and this is the first book written so far, after a long series of experiments conducted by the author. It is also the only book that deals with the problem from the viewpoint of the constructing engineer.

Esnault-Pelterie: L'Astronautique. A gigantic monument of scientific research and planning, with an extensive mathematical and technical survey of the whole problem of interplanetary flight. A Supplement to this book has recently been published as a separate volume. It consists essentially of his most recent lecture made before the Societe des Ingenieurs Civils de France.

David Lasser: Conquest of Space. This, the first book on rockets in the English language, was published in New York about three years ago. Mr. Lasser was the first president of the American Rocket Society. It is an excellent general, non-technical work on rocketry, written by one who has a keen appreciation of rockets and their possibilities, both for success and disappointment.

Chas. G. Philp: Stratosphere and Rocket Flight. The most recent book on rocketry and astronautics, and the first ever published in England. It deals with the history, scientific principles, and development of space flight, and includes a section on the problems of interplanetary space navigation.