A twenty-four hour orbit would have been more advantageous from the point of view of communications, except for the interference that would have been occasioned by the vast flood of electrons encircling Earth in the outer Van Allen belt. These electrons, trapped by Earth's magnetic field from the solar wind of charged particles escaping the sun, unfortunately occupied the twenty-four hour orbit, and, as their orbit expanded and contracted under the influence of the shifting magnetic field and solar flares, could produce tremendous havoc even in automatic equipment, so that it had been deemed economically impractical to set up the originally-postulated three satellites in stationary twenty-four orbits as communications terminals.
As the next best choice, the thirty-six-hour orbit had been selected. It gave a slow rate of angular displacement, since the satellite itself moved ten degrees an hour, while Earth moved 15°, for a differential rate of only five degrees an hour, making fairly easy tracking for the various Earth terminals of the communications net; and making possible a leisurely view of more than ninety per cent of Earth's surface every seventy-two hours.
The other two power and communications stations which led and lagged Space Lab One by 120° each, would combine to command a complete view of Earth, lacking only a circle within the arctic regions, so that they could provide power and communications for the entire world—a fact which had been the political carrot which had united Earth in the effort to create the labs with their combined technologies.
The danger of such powerful instruments as Hot Rod, concentrating megawatt beams of solar energy for relay to earth, and which could also be one of man's greatest weapons if it fell into unscrupulous hands, had been carefully played down, and also carefully countered in the screening by the Security Forces of U.N. of the personnel board.
T minus three and counting.
On the zero signal Mike in the engineer's quarters would change the now idly-bubbling air jets in the rim-rivers over to the fully-directional drive jets necessary to spin the fluid in counter-rotation through the rim tanks.
The suiting-up and strapping down were probably unnecessary, Mike thought, but in space you don't take chances.
"T minus two and counting." Bessie's voice rang over the com circuit in officially clipped clarity.
From the physics lab came a rather oddly pitched echo. "Allee allee in free fallee! Hold it, please, as Confusion would say! Paul forgot to secure the electrolite for the ECM equipment. Can't have these five-gallon bottles bouncing around!"