n in which it was urgently necessary for the space tug to go.
They could wait for two hours to take off, said Earth, or waste the time
and fuel they'd need to throw away to duplicate the effect of waiting.

"But we can't wait!" raged Joe. Then he snapped. "Look here! Suppose we
take off from here, dive at Earth, make a near-graze, and let its
gravity curve our course! Like a cometary path! Figure that! That's what
we've got to do!"

He kicked off his magnetic-soled shoes and went diving down to the
airlock. Over his shoulder he panted an order for the radar-duty man to
relay anything from Earth down to him there. He arrived to find Haney
and Mike in hot argument over whether it was possible to load on an
extra ton or two of mass. He stopped it. They would.

"Everything's loaded?" he demanded. "Okay! Space suits! All set? Let's
get out of this lock and start blasting!"

He drove them into the space tug. He climbed in himself. He closed the
entrance port. The plastic walls of the lock bulged out, pulled back
fast, and the steering rockets jetted. The space tug came out of the
lock. It spun about. It aimed for Earth and monstrous bursts of
rocket-trail spread out behind it. It dived.

Naturally! When a ship from the Platform wanted to reach Earth for
atmosphere-deceleration, it was more economical to head away from it.
Now that it was the most urgent of all possible necessities to get away
from Earth, in the opposite direction to the space tug's present motion,
it was logical to dive toward it. The ship would plunge toward Earth,
and Earth's gravity would help its rockets in the attainment of frenzied
speed. But the tug still possessed its orbital speed. So it would not
actually strike the Earth, but would be carried eastward past its disk,
even though aimed for Earth's mid-bulge. Yet Earth would continue to
pull. As the space tug skimmed past, its path would be curved by the
pull of gravity. At the nearest possible approach to Earth, the tug
would fire its heaviest rockets for maximum acceleration. And it would
swing around Earth's atmosphere perhaps no more than 500 miles
high--just barely beyond the measurable presence of air--and come out of
that crazy curve a good hour ahead of the Platform for a corresponding
position, and with a greater velocity than could be had in any other
way. Traced on paper, the course of the tug would be a tight parabola.

The ship dived. And it happened that it had left the Platform and