How You’ll Fly to the MOON (Mar, 1947)
How You’ll Fly to the MOON
THE days of dreaming about a trip to the moon are over. The research destined to make that trip an actuality is already well under way.
Next May the first step on the long, long trail into space may be made: Man hopes to send something up that will never come down again (see “Going Up for Keeps,” p. 66). In the words of Dr. Fritz Zwicky, the California Institute of Technology physicist who suggested the May satellite-making experiment, “We first throw a little something into the skies. Then a little more, then a shipload of instrumentsâ€”then ourselves.”
And other scientists agree. Dr. James A. Van Allen, of the Johns Hopkins University Applied Physics Laboratory, anticipates sending a rocket to the moon (one way, no crew) within 15 years. “A conservative estimate,” he says. Maj. P. C. Calhoun, chief of the AAF’s guided-missile branch, expects to travel to the moon and back in his lifetime. And the University of California at Los Angeles already offers a course in rocket navigation!
How the journey will be made is even now known in considerable detail. Rocket experts at Johns Hopkins and Caltech report that the space ship will look like this: A number of separate rocket motors (probably between three and five), each with its own fuel tanks. and controls, make up the power plant. The first motor, or stage, pushes the ship up a few hundred miles, when, its fuel exhausted, it is dropped off. The second stage then starts automatically and accelerates the ship until it uses up its fuel and is jettisoned. This process continues, each stage adding more speed, until the last stage completes the job of getting the 22,000-m.p.h. velocity needed to escape from the earth’s gravitational pull. Once free of the earth, the space ship can coast to the moon (there would be no air resistance). Only a little power would be needed for steering.
The multistage system eliminates the dead weight of big, almost-empty fuel tanks and seems to offer the most economical method of securing extremely long range. Tests of one of the first practical rockets of this type have already been made.
This rocket, the Tiamat, developed by the National Advisory Committee on Aeronautics, has two stages. One of its most important features is an accurate control system that permits it to be flown through fairly complicated maneuvers. Although quite smallâ€”less than 15 feet long and weighing about 600 poundsâ€”it is probably a good indication of the design of the moon rocket of the future.
The jump from the Tiamat’s 600-m.p.h. speed to the 22,000 m.p.h. needed for a trip to the moon is a big one, but not impossible. Twenty-two thousand miles an hour is not as fantastic a speed as it seems. The single-stage V-2 already gives 3,500 m.p.h., and succeeding stages would have the big advantages of reduced gravitation and complete absence of air resistanceâ€” both important factors.
Not that you can ride to the moon by hitching three V-2s together. If a multistage rocket uses a V-2 for the first stage (that, essentially, is the satellite-making rocket to be fired during May) the pay load in the final stage is a steel fragment smaller than a dime. Engineers can also calculate how big a ship able to reach the moon would be if its final stage were a V-2. Alfred Africano, pioneer in rocket development and now project engineer for the Curtiss-Wright Corporation, did the arithmetic. The answer is 5,500,000 tons.
But these calculations are based on the motor and fuels employed in the V-2. Although this power plant is the most efficient now known to be in use, it still needs nine tons of liquid oxygen and alcohol and four tons of motor and airframe to lift a one-ton pay load. Much higher efficiencies are re-, ported to be possible with fuel and motor combinations already being tested by the rocket researchers.
Better fuelsâ€”that is, hotter fuelsâ€”have been available for a long time. Rockets run on heat. The hotter the gases in the combustion chamber, the greater their pressure, the higher their speed as they shoot out the nozzle, and the faster the rocket is pushed ahead.
On that basis, hydrogen and oxygen would make the most effective fuels. When these two elements combine to form water, the reaction releases more heat per pound than any other now known. The best rocket would actually be a steam engine! Using hydrogen and oxygen as fuels, a moon rocket would need only five stages, according to the calculations of Martin Summerfield, of California Institute of Technology, a leading American authority on rockets. It would be 72 feet long and would weigh about 25 tons, about twice the size of the V-2.
Yet the tremendous heat available in oxygen and hydrogenâ€”the characteristic that makes them so desirableâ€”is the very reason they are not used. No lightweight motor can stand that temperature.
Present rocket motors are cooled by double-walled jackets through which one of the fuels is pumped. The fuel takes heat away from the motor and at the same time is warmed up itself for easier burning in the chamber. Ethyl alcohol, the V-2 fuel, works very well; its rate of burning (which determines how fast it is pumped through the cooling jacket) is about the same as its rate of heat absorption. For hydrogen, this is not true. It absorbs less heat per pound and must therefore be pumped through the cooling jacket, and burned, faster. The result is an inefficient flameâ€”or else the motor burns out.
If hotter fuels are to be used, new heat-defying motors must be made. Research in that direction has already been quite successful.
One group of materials that can withstand almost any temperature is ceramicsâ€”basically the same thing as dinner china. A ceramic motor, or motor lining, would never burn up. The problem is to make it strong enough. And recent advances in the ancient art of pottery making promise ceramics that will hold together under thousands of pounds of gas pressure.
Another possibility is powdered metal-finely ground metal dust that is solidified under terrific heat and pressure. Powdered-metal parts are hard, strong and porous. In a powdered-metal rocket motor, the tiny holes would permit much of the heat to escape outside to empty space.
A rocket with a ceramic or powdered-metal motor, using the most powerful chemical fuels and constructed with extremely light, strong materials, seems certain to be able to make a one-way trip to the moon. This is the feat scientists foresee before 1962â€”and maybe in 1948. But a one-way rocket could carry no men.
Building a true space shipâ€”one that could take a crew up and backâ€”is far more difficult because the pay load necessary is many times greater. To the weight of the men themselves must be added the weight of the things needed to keep them alive: a strong, airtight cabin; air, food and water supplies; some kind of cooling system to keep them from baking to death under the direct blaze of the sun, which would no longer be impeded by the blanket of air protecting the earth; and perhaps equipment to safeguard them against cosmic rays, too. Most important, however, is the weight of fuel for the return flight and braking during landings. Even with the best chemical fuels, operating at 100 percent efficiency, a round-trip rocket would be unreasonably large.
The fuel that can do the job is plutonium or uranium. About five pounds of uranium are enough for a round trip to the moon with a one-ton pay load. Only one stage is necessary.
In an atomic rocket a new feature, the “working fluid,” would be added. The fuel â€”uraniumâ€”would not be ejected itself, as in a chemical rocket, but would heat up the working fluid which would then be shot out of the base of the rocket to furnish the propelling power. The working fluid is required because a nuclear motor gives off energy in all directionsâ€”half the fission particles would fire out of the nozzles to push the space ship up, but the other half of the radioactive fragments would fly forward and heat up the fuselage. In fact, they would heat it up to about 28 million degrees! The working fluid traps all this energy, more than doubling the efficiency of the rocket, as well as preventing the passengers from burning up. Hydrogen, the lightest element, promises to be the best working fluid. Few scientific obstacles stand in the way of an atomic-powered space ship. The one big task remaining is the design of a small, lightweight “pile” capable of releasing large, controllable amounts of power.
And recent statements by leading physicists associated with the atomic-energy project indicate that such a power plant can be expected soon, perhaps within 10 years. Then the Buck Rogers boys will really take over.
To the first crew, the ride would be uncomfortable, at the very least. The cabin would have to be small, with food and water supplies extremely limited. The acceleration during the start would push the men down into their seats with a force equal to five times the pull of gravityâ€”about the same thing the pilot of a fast fighter plane feels in a tight turn.
As for danger, there would be plenty of it. The foreseeable risksâ€”such as running out of fuel, getting lost, breakdown of the air-conditioning system, etc.â€”are probably minor compared to the hazards we won’t know anything about until after a trip is actually made. The harm to be expected from cosmic rays, those high-speed particles so plentiful in the upper atmosphere, is already being measured by instruments carried in V-2s. The danger of running into a stray meteor can be forgotten; the chances are a million to one against it.
These first space travelers will find their itinerary all set, and complete with road maps. The astronomers, already well acquainted with at least one side of the moon, want to know what lies under the dense clouds that completely obscure the planet Venus; what is on Saturn, always hidden by its big rings of satellites; and what is the meaning of those strange lines on Marsâ€” the so-called “canals.”
But our old, friendly moon would probably be the first stop on any space route. First of all, it’s close. The 240,000-mile trip could be made in about 12 hours by a rocket traveling 22,000 m.p.h., the final speed needed to shake free from the earth.
And we already know a great deal about the moonâ€”more than we know about some parts of the earth, in fact. Its geography has been fairly accurately mapped (but only on the side facing the earth; the other side is a complete mystery). Its temperature has been recorded. It has little or no atmosphere.
The moon’s small size, which gives it a gravitational pull one-fifth that of the earth, is another advantage. Less power would be needed to get away for the return trip.
But all these plans must wait for the two basic elements: more powerful, lighter fuels; and motors to withstand their heat and pressure. So don’t rush to your travel agent. You won’t be able to buy a ticket for the moon tomorrow, or even the next day. But the day after that…