"Obviously the normal kinds are useless. Fragmentation shells would pelt the exterior of the hull with metallic rain—if and providing you could get them that close. Armor-piercing would work, possibly, but their damage would be negligible since hitting a spacecraft with a shell is impossible if the ship is moving at anything at all like the usual velocities. Detonation shells are a waste of energy, since there is no atmosphere to expand and contract. They'd blossom like roses and do as much damage as a tossed rose."
"No projectiles, then."
"If you could build a super-heavy fragmentation and detonation shell, and combine it with armor-piercing qualities, and could hit the ship, you might be able to stop them. You'd have to pierce the ship, and have the thing explode with a terrific blast. It would crack the ship because of the atmosphere trapped in the hull—and should be fast enough to exceed the compressibility of air. Also it should happen so fast that the air leaving the hole made would not have a chance to decrease the pressure. The detonation would crack the ship, and the fragmentation would mess up the insides to boot, giving two possibilities. But if both failed and the ship became airless, they would fear no more detonation shells. Fragments would always be dangerous, however."
"So now we must devise some sort of shell—"
"More than that. The meteor-circuits would intercept the incoming shell and it would never get there. What you'd need is a few hundred pounds of 'window.' You know, strips of tin foil cut to roughly a quarter-wave length of the meteor detecting radar. That'll completely foul up his directors and drive-couplers. Then the big one, coming in at terrific velocity."
"And speaking of velocity," said Walt Franks, "the projectile and the rifle are out. We can get better velocity with a constant-acceleration drive. I say torpedoes!"
"Naturally. But the aiming? Remember, even though we crank up the drive to fifty G, it takes time to get to several thousand miles per second. The integration of a course would be hard enough, but add to it the desire of men to evade torpedoes—and the aiming job is impossible."
"We may be able to aim them with a device similar to the one Chuck Thomas is working with. Murdoch said his hull was made with lithium?"
"Coated with," said Channing.
"Well. Set the alloy-selectivity disk to pure lithium, and use the output to steer the torpedo right down to the bitter end."