Saturday, December 27, 2008

Early plans for a lunar mission

"Design of the British Interplanetary Society's BIS Spaceship began in 1937 and was published in January and July 1939. The purpose of the exercise was to prove that a manned lunar expedition could be designed using existing powder rocket technology. The design was reformulated in 1947 based on information on German advances with liquid propellant rockets.

Available British rocket technology then consisting only of powder rockets, the booster consisted of 2,490 such rockets, which were shed as soon as they were exhausted. Thus a kind of 'infinite' staging was used to compensate for the very low specific impulse of the motors. The hexagonal booster was 6 meters in diameter and 32 meters long, with a lift-off mass of 1112 metric tons. Launch was from a flooded caisson in a high-altitude lake near the equator. The one metric ton spacecraft delivered a crew of three to the lunar surface, landing on gear very similar to those used for the Apollo Lunar Module sixty years later. Following re-entry in the earth's atmosphere, a parachute was used for final descent. Oddly, heating during ascent through the atmosphere was seen as a real problem, while re-entry on return was considered trivial ("accomplished in easy stages" via aerobraking). Therefore a jettisonable ceramic shield protected the spacecraft from heating expected to reach 1500 deg C during ascent, while no heat shield was considered necessary for return.

J Happian Edwards led the design team, which included H Bramhill (draftsman), Arthur C Clarke (astronomer), A V Cleaver (aircraft engineer), M K Hanson (mathematician), Arthur Hanser (chemist), S Klemantski (biologist), HE Ross (electrical engineer), and R A Smith (turbine engineer)."

The ideas here are essentially sound, if highly optimistic. The spacecraft mass would have to be probably an order of magnitude more massive, and the capsule would need heavy shielding for reentry rather than exit of the the atmosphere. Further, it is unlikely that people could survive reentry without a lifting body entry craft, because a direct entry from the moon results in huge G forces like 15 or more Gs.

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