There was a long and breathless wait.
"Up ship!" shouted the speaker.
Matt felt himself pressed into the padding.
Terra Space Station and the school ship Randolph He in a circular orbit 22,300 miles above the surface of the Earth, where they circle the Earth in exactly twenty-four hours, the natural period of a body at that distance.
Since the Earth's rotation exactly matches their period, they face always one side of the Earth-the ninetieth western meridian, to be exact. Their orbit lies in the ecliptic, the plane of the Earth's orbit around the Sun, rather than in the plane of the Earth's equator. This results in them swinging north and south each day as seen from the earth. When it is noon in the Middle West, Terra Station and the Ran-
dolph lie over the Gulf of Mexico; at midnight they lie over the South Pacific.
The state of Colorado moves eastward about 830 miles per hour. Terra Station and the Randolph also move eastward nearly 7000 miles per hour- 1.93 miles per second, to be finicky. The pilot of the Bolivar had to arrive at the Randolph precisely matched in course and speed. To do this he must break his ship away from our heavy planet, throw her into an elliptical orbit just tangent to the circular orbit of the Randolph and with that tangency so exactly placed that, when he matched speeds, the two ships would lie relatively motionless although plunging ahead at two miles per second. This last maneuver was no easy matter like jockeying a copter over a landing platform, as the two speeds, unadjusted, would differ by 3000 miles an hour.
Getting the Bolivar from Colorado to the Randolph, and all other problems of journeying between the planets, are subject to precise and elegant mathematical solution under four laws formulated by the saintly, absent- minded Sir Isaac Newton nearly four centuries earlier than this flight of the Bolivar-the three Laws of Motion and the Law of Gravitation. These laws are simple; their application in space to get from where you are to where you want to be, at the correct time with the correct course and speed, is a nightmare of complicated, fussy computation.
The "weight" pressing Matt into the padding was four gravities-Matt weighed nearly six hundred pounds. He lay there, breathing with difficulty, while the ship punched its way through the thick soup of air and out into free space. The heavy weight bound down the cadets while the Bolivar attained a speed of some six miles per second and climbed to an altitude of 900 miles.
At the end of five minutes and a few odd seconds the drive stopped.