ause of Pluto, the American silver bloc had been broken at last.

The _Mordred_ was approaching turnover.

Now, with a gravito-inertial drive, there is really no need to turn a
ship over end-for-end as she approaches the mid-point of her
trajectory. Since there is no rocket jet to worry about, all that is
really necessary is to put the engine in reverse. In fact, the patrol
ships of the Interplanetary Police do just that.

But the IP has been trained to take up to five standard gees in an
end-to-end flip, and the ships are built to take the stress in both
directions. An ordinary cargo ship finds it a lot easier to simply
flip the ship over; that way, the stresses remain the same, and the
ceiling-floor relationship is constant.

The _Mordred_ had been having a little trouble with her Number Three
drive engine, so the drive was cut off at turnover, while the engineer
replaced a worn bearing. At the same time, the maintenance officer
decided he'd take a look at the meteor-bumper--the plastic outer hull.
Since the ship was in free fall, all he had to do was pull himself
along one of the beams that supported the meteor-bumper away from the
main hull. The end of one of the beams had cracked a part of the
bumper hull--fatigue from stress, nothing more, but the hull might as
well be patched while the drive was off.

It was a one-man job; the plastic was dense, but under null-gee
conditions it was easy to maneuver. The maintenance officer repaired
the slight crack easily, wiped the sticky pre-polymer from the fingers
of his spacesuit gloves, and tossed the gooey rag off into space. Then
he pushed himself back across the vacuum that separated the outer hull
from the inner, entered the air lock, and reported that the job was
finished. Five minutes later, the _Mordred_ began decelerating toward
the distant Asteroid Belt.

Forget the _Mordred_. The ship is no longer important. Keep your eyes
on that rag. It's a flimsy thing, composed of absorbent plastic and
gooed up with a little unpolymerized resin, weighing about fifty
grams. It is apparently floating harmlessly in space, just beyond the
orbit of Uranus, looking as innocuous as a rag can look. But it is
moving sunward at eight hundred million centimeters per second.

* * * * *

The _Persephone_ was approaching turnover. The ship's engineer
reported that the engines were humming along smoothly, so there was no
need to shut them off; the ship