
when pressed, turning off all power and drifting "dead" in water or space. It is difficult to spot a small
dead object in space, for space is immense. There may still be uncharted planetoids orbiting the sun.
Consider how long it took for Earthly telescopes to identify our companion star, Nemesis. But in the
vicinity of an inhabited planet a sub's mere silence is not sufficient, for the space there is constantly
explored by radar. Nevertheless, subs often evade detection. To understand how this is possible, it is
necessary to grasp the general nature of radar and similar systems.
Radar is simply an electronic signal broadcast into space. When it encounters an object, it bounces back
to its source. A receiver notes that returning signal and calculates the distance by the time required for the
signal to return. This is normally a reliable procedure, except when the region is crowded with a confusing
number of objects, such as the particles of a planetary ring system. Even then, a properly programmed
computer can identify all of the natural and "friendly" objects in the vicinity and highlight the suspicious
ones. But the principle remains: The computer depends on the returning signals to spot the objects. If no
signal returns the machine assumes that region of space is clear. This seems reasonable enough.
But suppose you could evade or divert the signal, so that it did not bounce back? Reflect it to the side
instead of back? Or simply absorb it? That is what a sub does. It uses a special gravity shield to form a
black-hole effect that absorbs all incoming energy, including the radar signals. That makes it effectively
invisible to radar. Of course some care is necessary; if a sub passes between a person and the sun, it will
show up as a dark blot. It also blots out the light of any star it occludes. Parties watching for subs are
alert for this and pay close attention to what isn't visible, such as a particular star, as well as what is.
Again, a programmed computer can constantly verify the positions of all light sources and signal alarm
when any fail even momentarily. But a carefully maneuvered sub can avoid occluding any sufficiently
bright stars while it floats near a planet and so remain invisible—up to a point. Close to a planet there are
too many watching satellites, and the silhouette of the sub looms proportionately larger until concealment
is impossible.
So most subs remain deep enough in space to hide but as close to the target planet as feasible, covering
it with their deadly missiles. Jupiter subs surround Saturn, and Saturnine subs surround Jupiter. If war
should break out the planet-to-planet missiles might well be intercepted before scoring, but sub-to-planet
missiles could devastate any city on any planet. That is the true balance of terror. Subs, more than any
other factor, contribute to the general feeling of insecurity on every planet; no one can be sure that his city
would survive a third System war—and there is a general fear that such a war is inevitable. It makes
planetary populations edgy, in much the way that a man threatened with arbitrary execution might be
edgy. There are reasonably frequent flare-ups of protest and even violence scattered around the System,
but no one has found a way to diffuse the threat. Perhaps one of the major appeals of the difficult life in
the Belt is that the widely scattered settlements there would be most likely to survive a System war.
So I was in a sub. What was the significance of that? This was surely not a missile sub; those were too
precious for the mere torturing of mem-washed captives. But escape fromany sub was hopeless to then
th power. I couldn't flash a light out a porthole, for the signal-damping field would extinguish that.
Theoretically I might surprise someone, grab a weapon, and take over the ship, but that sort of heroic is
feasible only in fiction, and not the best fiction at that. In real life ships have safeguards, such as automatic
sleep gas released into the air when unauthorized personnel step onto the bridge, and secret codes for the
life systems support and drive computers. Only the regular personnel could operate this ship; I knew that
without needing verification. It was one of the advantages of my Navy experience: I knew what wasn't
practical. All I could do was try to steal a suit and escape the ship—and outside was only the void.
My presence here also meant that some military outfit was in charge, for civilians did not have subs of
any kind and neither did pirates. Only governments. That meant I was the captive of a nation. Was I a
hostage? Then why the mem-wash, degradation, and torture? That didn't seem to make a lot of sense. It
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