As soon as the three cadets saw the change in armament, they knew they
were guarding something so secret that human life, if it interfered with
the project, would be disintegrated. Only once before, on a hunting trip
to Venus, had they ever used the blasters, but they knew the deadly
power of the weapons.

Nothing was said to them. Firehouse Tim had not posted any special
orders or given them any special instructions. Each man who worked
inside the hangar had to pass a simple but telling test of
identification. On a table at each entrance to the hangar was a small
box with a hole in the top. Each worker, guard, and person that entered
the hangar had to insert a key into the hole and it made contact with a
highly sensitive electronic device inside. The keys were issued only by
Major Connel or Captain Strong, and should anyone attempt to enter the
hangar without it, or should the key not make the proper contact,
lighting up a small bulb on the top of the box, Tom, Roger, and Astro
had simple instructions: Shoot to kill.

This form of identification had been employed for some time now, even
before the wire fence had been installed, but the really spectacular
change was in the heat blasters each guard carried. This, more than
anything else, impressed on everyone connected with the project, that to
move the wrong way, to say the wrong thing, or to act in any suspicious
manner might result in instant death.

It was a mark of trust that Tom, Roger, and Astro had been placed in
such a highly sensitive position. They could kill a man and simply
explain, "The light didn't go on!" and that would be the end of it.
Neither of them knew that Connel had specifically requested that they be
assigned to the day shift, when the hangar would be crowded with
workers, who, intent on their assigned jobs, might be careless and leave
themselves open to instant action on the part of the guards. Connel
reasoned that Tom, Roger, and Astro, aside from their occasional antics
in the Academy, would be more responsible than rough enlisted spacemen.
The orders were specific: shoot to kill, but there was almost always one
poor human being who would forget. In spite of the necessity for tight
security, Connel felt he had to allow for that one percent of human
failure. Secretly he was very happy that he had a crack unit like the
_Polaris_ to place in such a job. And the _Capella_ unit had been
entrusted with the same responsibility.

It was under su