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Aviation History
1964
1964 - 0285.PDF
182 FLIGHT International, 30 January Missiles and Spaceflight Artist's impression of Apollo lunar excursion module (LEM) about to touch down on the lunar surface, the nature of which is discussed in this article SETTING FOOT ON THE MOON SOME time towards the end of this decade, the residents ofsouthern Florida will cup hands over their ears to protectear-drums from the deafening roar emanating from NASA's Cape Kennedy launch complex. Within seconds a gigantic Saturn V booster will begin to rise slowly off its launch pad, and three Apollo astronauts will begin an historic journey towards the Moon. Many hours and several booster-stagings later the combination of the Apollo command service module (CSM) and the lunar excursion module (LEM) will approach the Moon and, with appropriate reverse thrusting, will enter into a circular orbit some 80 nautical miles above the lunar surface. When the LEM and CSM (still travelling alongside one another) arrive at a point which is approximately 104° ahead of the preselected landing site, the LEM descent engine will be ignited. Burning will continue until the LEM achieves a descending, eliptical orbit whose psricynthion (closest point of approach to the lunar suface) is 50,000ft. The advantage of this particular orbit, according to Paul Munter in his AIAA treatise The LEM Mission is that, if the mission' had to be aborted, the LEM would continue in this orbit until it intercepted the CSM, which would have remained in its 80-mile circular orbit. Presuming normal conditions, however, the descent stage engine would be re-ignited at the pericynthion point. A gradual rotation of the thrust vector would be commanded until a point was reached approximately five miles from the projected landing site. Thrust would next be reduced until the LEM reached a further check-point 1,000ft above and some 3,000ft distant from the landing site. Up until this point all manoeuvres would be automatically controlled, but at this time the astronauts would take over control and com- plete a manual descent on to the lunar surface. A "hover-to-land" trajectory would be pursued as some effort was made to determine the exact nature of the surface, but finally the thrust will be cut with the LEM some 10ft above the surface. The LEM will then drop on to—on to what? Much has been written and been said about the nature of the lunar surface. Speculation has ranged from a covering of dust, millimetres to metres thick, through a variety of hard or semi-hard surfaces. The latest views on the lunar surface were presented to a gathering of interested engineers on Long Island recently by Dr Thomas Gold of Cornell. Scientists now know much more about the lunar surface than was believed possible five or six years ago, Dr Gold said. Analyses of optical, thermal and radar data had yielded a consistent theory and if, as was generally accepted, the Moon was made of some kind of rock, then it was certain that the satellite was covered by a crunchy rock structure of about one-sixth to one-tenth the density of terrestrial rock. The key question, he said, was the depth of this material, which could be likened to a fluff or "cookie crunch" and would clearly be incapable (without further compacting) of sustaining the pressure of a human foot. Dr Gold's conclusion was that the crunchy structure covering the lunar surface was several metres thick. As the speaker had suggested on previous occasions, astronauts might step on to this and disappear as if they had stepped on to a deep snowdrift. Outlining the basis for this conclusion, Dr Gold said that few informed people believed that the Moon was constructed of any- thing other than a rocky material or that the nature of the surface had been determined by anything other than impacts by large and infinitesimally small meteorites. If this conjecture were true, the lunar lowlands, where no large craters were visible, must have been filled by something. Early theories had suggested a lava flow, but optical analyses had indicated a preferential back-scatter of light which was extraordinarily uniform over the entire lunar surface (including craters, lowlands and highlands), and this uniformity ruled out the concept of lava flow. This uniformity also verified that the surface was the result of external rather than internal forces, since no internal lunar action could produce a surface which was consistently the same over every square kilometre. Many hundreds of laboratory tests had been conducted to determine what material or combination of materials could produce the identical back-scattering characteristic. It was proven beyond any reasonable doubt that the surface must be constructed of opaque particles only a few microns in size. These small particles were compacted in a most unusual form, which was the result of countless bombardments by meteorites. As each meteorite or micrometeorite struck, it threw up small clouds of dust which resettled in a mathematically predictable form. Each particle contacted its neighbour at a single point, and the surface effects of the particles far outweighed the effects of inertia and gravity. Stepping out of the LEM on to the Moon, the Apollo astronaut will look like this. Shown recently at NASA's Manned Spacecraft Center, Houston, this advanced-model Apollo suit is designed to keep the astronaut com- fortable on the lunar surface—or in space—for periods up to four hours. The back-pack supplies oxygen and ventilation, controls temperature and humidity, and removes respiratory and body contaminents inside the suit
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