Word: pulls
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Dates: during 1950-1959
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Near the rim of the earth's gravitational pit is a much smaller pit belonging to the moon. An object shot away from the earth at 24,800 m.p.h. will reach the boundary, about 34,000 miles short of the moon, where the moon's pull is as strong as the earth's. If it reaches this point with a small velocity, it will fall on the moon. If it crosses the line at good speed, it will shoot past the moon, its course merely deflected. This is what happened to the Lunik...
...orbit (see chart). His ship must have a speed of only 870 m.p.h. over escape velocity. The excess speed is added to the earth's orbital speed (66,600 m.p.h.) that the spaceship had before it was launched. This is enough to offset the sun's gravitational pull, allows the ship to swing outward in an ellipse. If the timing is right, it makes a rendezvous with Mars on its orbit...
...days to Venus, 260 days to Mars), but only slightly more speed than is needed to go to the moon, which is only 230,000 miles away. This is because space between the planets is comparatively smooth. It is only slightly affected by planetary gravitation, and the great pull of the sun is countered by the orbital speed that a spaceship inherits from its home planet...
Interstellar Escape. Full escape from the gravitational pull of the sun would be tougher. Starting from the earth's surface, a ship would need 36,800 m.p.h. Soaring past Mars, Jupiter, Saturn, Uranus, Neptune and Pluto, it would reach the outer limits of the solar system with almost no speed left. Then, like a chip on a glassy lake, it could drift for millions of years before it approached the nearest star, Proxima Centauri, which is 25 trillion miles away from the sun. Man's spaceships can probably reach interstellar escape velocity in a generation, but there will...
...success would be to pass around the moon and return to earth. If the Russians were trying to do this, they did not know their own strength. When Lunik passed the moon, it was going so fast (5,500 m.p.h.) that the moon's feeble gravitation could not pull it back...