Electromagnetic Launching as a Main Contribution to House-Flight (1950)

Lunar electromagnetic launch observe. Picture credit score: R. A. Smith/The British Interplanetary Society. 

Within the 1968 novel 2001: A House Odyssey, British creator Arthur C. Clarke invoked an previous spaceflight idea to start a voyage to the Moon. Dr. Heywood Floyd, an area company bureaucrat, boarded a winged, reusable Earth-to-orbit shuttle mounted horizontally atop a winged, reusable booster, which in flip was mounted horizontally on a “sled” driving on an electromagnetic observe. 

The observe used bodily rules first studied within the late 18th century. It will not be an excessive amount of of a stretch to consider it as a traditional rotary electrical motor laid out flat, in order that linear movement alongside a observe changed rotary movement a couple of shaft. The linear induction motor, as it’s usually recognized immediately, was first studied as a method of launching plane by the Westinghouse Company in 1945.

Clarke’s launch observe activated as his booster’s rocket motors ignited. The sled accelerated the booster/shuttle stack till the booster’s wings started to offer elevate. Because it grew to become airborne its rocket motors throttled up and the booster/shuttle stack started a fast climb towards low-Earth orbit (LEO). 

Fifty-one years earlier than the yr 2001, Clarke outlined the bounds of electromagnetic launching. In a paper within the November 1950 subject of the Journal of the British Interplanetary Society, he defined {that a} spacecraft couldn’t attain Earth escape velocity of 11.2 kilometers (seven miles) per second on an electromagnetic launch observe; because it gained pace, it might compress the air in entrance of it, subjecting it to aerodynamic heating enough to destroy it. He identified that the nostril of the German V-2 missile had turn out to be “red-hot” at a pace of simply 0.9 kilometers (0.6 miles) per second. 

Even when the thermal drawback could possibly be solved, launching a spacecraft bearing a crew on an electromagnetic observe was unlikely to be sensible. People can not stand up to excessive acceleration, so a piloted spacecraft would wish an extended launch observe. Even when acceleration equal to 10 occasions the pull of gravity on Earth’s floor have been deemed acceptable, the electromagnetic launch observe required to succeed in Earth escape velocity would should be a minimum of 600 kilometers (375 miles) lengthy. 

Clarke solved these issues by transferring the electromagnetic launch observe to the Moon, the place escape velocity is simply 2.3 kilometers (1.4 miles) per second and there’s no air. He additionally deserted any considered launching crews; his lunar electromagnetic launch observe can be used to launch tanks stuffed with rocket propellants manufactured from lunar floor materials.

In 1950, nobody knew the chemical composition of the lunar crust. Clarke assumed that the Moon may provide each hydrogen gas and oxygen oxidizer. Because it turned out, he was proper, although this truth was not confirmed till the presence of water ice in completely shadowed craters close to the lunar poles was confirmed within the late Nineteen Nineties. Water will be electrolyzed (break up utilizing electrical present) to yield hydrogen and oxygen.

The ability system for the electromagnetic launch observe would rely upon a flywheel that may be spun up regularly over hours or days utilizing an electrical motor pushed by a nuclear or photo voltaic electrical energy supply. Clarke calculated {that a} 50-metric-ton (55-ton) flywheel 4.4 meters (14.4 ft) in diameter spinning at 1200 rotations per minute may, if coupled to a correctly designed overload-tolerant generator, present a mean energy over two seconds of about a million kilowatts. This could be enough to speed up a one-metric-ton (1.1-ton) cargo to a velocity of two kilometers (1.25 miles) per second. 

When electrical energy was utilized to the observe, acceleration would leap from zero to a “very excessive worth” then lower to 50 Earth gravities in simply two seconds. This acceleration profile would dictate electromagnetic launch observe size: it might stretch about three kilometers (1.9 miles) throughout the lunar floor. The observe may be constructed on a degree if no obstacles stood in its launch path; alternately, it could possibly be constructed with a slight upward slope.

A propellant tank launched at two kilometers per second would gradual to 0.78 kilometers per second because it reached the 3020-kilometer (1875-mile) excessive level (apoapsis) of its elliptical orbit concerning the Moon 2.5 hours after launch. If no additional motion have been taken, it might attain the low level (periapsis) of its elliptical orbit 5 hours after launch touring at two kilometers (1.25 miles) per second. Periapsis would happen on the lunar floor; in different phrases, the track-launched tank would crash. 

Clarke calculated that firing a small rocket motor at apoapsis to speed up the propellant tank by 0.22 kilometers (0.14 miles) per second would end in a round lunar orbit at apoapsis altitude. He assumed that the rocket motor would expend propellants equal to solely 6% of the cargo weight, a amount he deemed “trivial.” A spacecraft may then rendezvous with the cargo and pump the propellants into its tanks.

An area station may corral propellant tanks after they arrived in round lunar orbit, maybe utilizing small auxiliary automobiles. Spacecraft touring in cislunar area may then rendezvous with the station to refuel. 

Alternately, the electromagnetic launch observe may speed up the tank to a barely increased velocity, boosting it into an elongated elliptical orbit with a interval of days. This would offer time for a spacecraft to rendezvous with its close to apoapsis, the place it might transfer very slowly. The empty propellant tank can be allowed to crash harmlessly on the lunar floor.

The electromagnetic launch observe may, Clarke identified, place propellants mined and refined on the Moon into LEO at the price of a 20% enhance in launch velocity and elevated steering system complexity. The previous could possibly be achieved by lengthening the observe and including a “booster” flywheel/generator close to its finish.

If launching propellants to LEO have been discovered to be possible, then a cislunar spacecraft may attain LEO with empty tanks, refuel at a station, journey to lunar orbit, refuel at a station earlier than touchdown, land, refuel on the lunar colony, climb to lunar orbit, refuel at a station, and depart lunar orbit for Earth orbit. Although operationally advanced, this strategy may simplify the design of cislunar spacecraft, since, as Clarke defined, none “want ever be designed for any mission tougher than entry of a round orbit around the Earth.” 

Clarke cautioned {that a} lunar colony would should be established and its “industrial potential” constructed up earlier than lunar sources could possibly be mined, refined, and long-established into an electromagnetic launch observe. “We’re,” he wrote, “reasonably within the place of attempting to run a trans-Atlantic airline when there isn’t any risk of refueling. . .till we’ve got drilled our personal oil wells and arrange our personal refineries!”  

The time wanted to determine a colony and industrial infrastructure on the Moon may, in actual fact, imply that technological breakthroughs would make launching propellants from the Moon utilizing an electromagnetic observe out of date earlier than it may start. Clarke argued, however, that “it’s. . .nicely to maintain the Moon-based electromagnetic launcher in reserve as an answer of the long-term issues of spaceflight.”

The picture on the high of this put up is Copyright © The British Interplanetary Society ( and is utilized by type permission.


“Electromagnetic Launching as a Main Contribution to House-Flight,” Arthur C. Clarke, Journal of the British Interplanetary Society, Vol. 9, No. 6, November 1950, pp. 261-267.

The Exploration of the Moon, Arthur C. Clarke & R. A. Smith, Harper & Brothers, 1954, pp. 102-103.

2001: A House Odyssey, Arthur C. Clarke, New American Library, 1999 (Millennial Version), pp. 35-40.

Extra Info

Moon Go well with: 1949

Apollo Purposes Program: Lunar Module Relay Experiment Laboratory (1966)

People on Mars in 1995! (1980-1981)

The Nineteen Eighties Lunar Revival: Lunar Oxygen (1983)

May the House Voyages within the Movie and Novel “2001: A House Odyssey” Actually Occur? (Half 1)

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