ON THE EVE OF SPACE TRAVEL

Press, Volume C, Issue 29513, 13 May 1961, Page 8

ON THE EVE OF SPACE TRAVEL

Memories And Theories Of A Rocket Pioneer

[By Professor HERMANIf OBKBTHJ LONDON, May 5. pROFESSOR Hermann Oberth has been called “the father of modern rocket engineering” because of his epoch-making contributions to rocket propulsion. In this exclusive series of articles he summarises the past and present of rocket engineering, including his own first steps in this field, and he finishes by setting down what in his belief will be the nearest future of space travel. Professor Oberth was born in 1894 in what was then Austro-Hungarian (later Rumanian) Transylvania, and in 1923 laid the foundation of modern rocket research by his book “The Rocket Into Interplanetary Space.” In 1930 he designed the first rocket engine for liquid oxygen, and the German V-2 rocket of World War II was based on his principles. Since the war he has participated in rocket research in the United States.

The motion or flight of a rocket is based on the reaction principle. For every force working in one direction, there is an equal counterforce, or reaction, working in the opposite direction. For instance, if we want to push a heavy object in front of us, our feet must push backward. A body uninfluenced by any external force—for instance flying in empty space far from earth with no gravitational drag or pull and with no atmosphere—will fly in a straight course in the same direction at uniform speed. Let us take the example of a beam travelling in space. Now let us imagine there is a space pilot on this beam who saws the beam into two parts, so that the rear part’s just as heavy —has the same mass—as the front part including his own weight. This done, he puts an explosive charge between the two and makes them blow apart. Obviously they will part from each other with the same velocity, and the front part of the beam which was already flying ahead at high speed, will get an increase of speed. When the pilot repeats the operation, his new front part will again receive an increase of speed. Naturally, if he repeats the operation a sufficient number of times, any speed may be reached. There is. however, a limit to continuing this division indefinitely. After one division, the front part (including himself) will have only one-half of the mass of the undivided beam, after two divisions one-quarter, after three one-eighth, etc. After 10 divisions the pilot will only have one-1024th part of the original mass at his disposal: and after 20 divisions not even one-mil-lionth part. A better result is obtained by economising with the material—that is, by blowing away much less than half at each division, but using greater force for each explosion. In a borderline case a relationship of 20,000:1 between original mass and final mass might give the same effect as a relationship of 1.000.000:1 as in the case described.

Force Of Reaction It is apparent from the example that the force of reaction is effective in empty space without atmosphere. In the early years of rocket research, the objection was often heard thrt the gases of the explosions would have no power if they had no air or other medium to push against. In reality, of course, it is of absolutely no importance whether the gases explode in air or in empty space. A gas consists of infinitesimal molecules, and each time a molecule is pushed out, the remaining mass of the system will receive a

push in the opposite direction. Rockets have been known for centuries. The Chinese used them at least 800 years ago. There is a first mention of them in a Chinese chronicle in 1232 A.D., but apparently they had been used for a very long time then. It was a favourite pastime of the Chinese at popular festivals to shoot burning arrows into the sky. In their wars they used such arrows to set fire to besieged cities and villages. As a firing charge they used resinimpregnated tow, to which they added charcoal and incense, and for their war arrows they also used pitch, asphalt, fat, naphtha and sulphur. Moreover, they kneaded saltpeter into this mass, for they had noticed that this would make the charge fire better. To keep the charge together they wound paper around it, or put it into paper tubes. These tubes were manufactured in exactly tire same manner as for modern fireworks. Glue was smeared on one side of a long paper strip, which was then wound around a staff. When the glue dried, the staff was removed, and there was the tube. “Fire Arrow” The powder-filled tubes were tied to arrows, ignited, and shot from bows. The Chinese discovered that an arrow would fly faster and higher if they set fire to the rear end of a charged tube, and from the Eleventh Century they also knew that it is not at all necessary to shoot such an arrow from a bow. It is enough just to set fire to the charge—and that was how the rocket was invented. It is significant that in the Chinese chronicle its called “a fire arrow.” From China, rockets reached Europe by way of Arabia in the thirteenth century. They were chiefly used at festivals, but sometimes also as fire missiles. As late as in 1807 the British set fire to Copenhagen using Congreve’s rockets. This type of war rocket fell into desuetude, however; cannon balls were preferred for their greater accuracy, longer range and smaller consumption of powder. The discovery of smokeless powder and the invention of rifle guns meant no change; by comparison rockets appeared even more inferior. But there were some other uses for rockets—the hail rocket, for instance, which is highly praised by Swiss farmers, even though scientists have not been able to ascertain whether it is indeed as effective as the farmers aver. Hail is formed like this, when air rises rapidly, it is cooled and any vapour of water contained in the air is precipitated in the form of tog or clouds. A thunder cloud may contain more water than could be trans-

ported by 100,000 goods trains. Under certain circumstances and if the cooling is very great, water may remain liquid below freezing point. If such water is shaken violently, or if an ice crystal passes through it, it will suddenly freeze. It is in this way that the front edges of aeroplane wings will be covered by ice, if the aeroplane flies into such a cloud. Now, if a raindrop ar ice crystal falling from greater altitudes passes through a cloud of such super-cooled water, there will form a shell of ice around it, and a hailstone is born. Without doubt the jolt caused by a rocket explosion in a cloud of super-cooled water will be enough to transform the drops into snow crystals which can cause no damage. They cannot form ice shells around raindrops falling from above, and in summer they will thaw before reaching the ground. Thus a violent explosion in a hail cloud would actually prevent the formation of hailstones. The headache for the physicists and meteorologists in explaining this assumed effect from a rocket explosion 'is that thunder and lightning must cause much greater jolts to super-cooled water clouds, yet thunder and lightning do not prevent hailstorms. New Use Found For Rockets During the 19th’ century other uses were found for rockets: for instance, to carry ropes from shore to ship or between ships. Often when a ship runs aground, other ships or their lifeboats cannot come near enough for assistance because of the breakers. In such cases a rocket shot across to the distressed ship can carry a line fastened to it. At the other end of the line will be a strong rope, and wheru the crew have pulled it aboard and made it fast, men and goods from the grounded ship can be hauled to safety 'along this rope. In the same manner, rockets can be used to carry wires across inaccessible canyons. At the end of last century an Austrian by name of Maul built rockets carrying photographic cameras. They were to be used for photographing enemy positions and to be brought back to the ground by parachutes. The coming of the airplane killed this idea before it found any wide use. Light-rockets were also an aid to military reconnaissance. Books By Jules Verne This was, more or less, the situation during the first quarter of this century. The rocket was there, but it resembled a bright but poor boy who has a modest job in a big firm. Having no great amount of education or training, he cannot do much qualified work, and because his performance is so modest, noone will devote great attention to him. This is where my contribution to rocket engineering started. In 1907 I read Jules Verne’s two books about moon flights. I soon realised that travelling to the moon would not be possible by just shooting a space ship from a giant cannon as Jules Verne suggested: and, looking for suitable ways of space travel, my attention was drawn more and more to rocket propulsion.— Express News and Services, London. (To be Continued.)

Life Membership— The New Zealand Educational Institute yesterday conferred life membership on Mr D. C. Pryor of Palmerston North, who becomes the sixth surviving life member. Only 14 life members have been appointed in the 78 years the institute has functioned.— (PA.)