DARPA Research HQ: Orbital Applications Dept., 400 metres under the Sonora Desert. December 1989.
General Maxwell Sully: "So, my smarty-pants scientific researcher people. What crazy idea have you got for me today?"
Professor Janet Chu: "Moon rock, Sir."
General Maxwell Sully: "I can see that Chu. It's a big lump of rock. Is that REALLY best you can do?"
Professor Janet Chu: "Well Sir no, that's not all. Please watch the animation Sir."
[General Maxwell Sully starts to finger tap and clears throat with theatrical impatience.]
Professor Janet Chu: "Er, what's going on with the animation Eric?"
Doctor Eric Stickles: "...I don't know Jan, the Cray is just really slow this morning for some reason. I've keep trying to get through to I.T... Oh, hang on... here it comes!"
Professor Janet Chu: "Right Sir, so you know how our nukes keep getting taken out by flak or missiles well before they get close enough to the enemy satellites and installations to do any damage?"
General Maxwell Sully: "Well, yes, Chu. It was in fact me that gave you the briefing, remember?"
Professor Janet Chu: "Of course Sir, anyway we were thinking about shielding and but it's just so probititive to get anything with the right level of density up into orbit - so we thought, why not just blow out a chunk of moon rock, hollow it out, strap on a couple of big engines, fill the back end with fuel and put a few standard warheads in the front... And bingo! We're protected by a few metres of solid rock from any flanking attack, then we tack on a ballistic cannon up front to take out any forward attacks and we'll be able to get our nukes close in enough to be effective. Ka-boom Sir!"
Doctor Eric Stickles: "Jan, Jan, you forgot the best bit!"
Professor Janet Chu: "Ah, yes thank you Eric. So, we always leave one up the chute as it were, inside the hollow moon rock. Just in case our main nukes don't do the job, the rock keeps flying in, a big unstoppable mass, and as soon as it gets near the target, ka-boom again! The nuke goes off, sending thousands of tonnes of space rock shredding anything in its path like a giant grenade!"
Doctor Eric Stickles: "Double-big ka-boom, Sir."
General Maxwell Sully: "Yes, quite, Stickles. So what's the Pilot Module for?"
Professor Janet Chu: "Just initial guidance and setup Sir. The pilot'll bring it in close and perform a few evasive jinks and dummy manouvers to confuse the enemy defenses, then lines up the rock for final approach and detaches, returning to a safe orbit. The main thrusters could be detachable and recoverable too."
General Maxwell Sully: "Hmm. Interesting, Chu. For once, you might be on to something. Permission and funding for second stage design development granted. And move it. I want these things in production within six months!"