Throwing Rocks

Really Big Rocks

By MXSavant 08/04/05

Recently I’ve been playing around with some Silent Death rules for towing things that can’t move by themselves. This would be a good thing to have for situations involving open salvage, rescue scenarios, and moving larger pre-fabricated platforms or satellites into positions, and so on. But there is also the idea of using towing offensively. Explanations follow. A good example of this idea is in the novel Footfall by Larry Niven and Jerry Pournelle. In this invaders-from-beyond page-turner, malevolent aliens beat the earth into submission by bombarding it with asteroids.

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A NASA image of the asteroid Gaspra.

Earth has been hit many times by asteroids and comets throughout its history. The number of impacts is probably in the hundreds. This has only been discovered relatively recently because the earth’s active erosion and plate tectonics tend to eradicate all but the more subtle evidence of asteroid impacts. So this isn’t exactly science fiction. But using them as weapons for planetary bombardment is another matter.

I know, I know. Silent Death is a game. One can get carried away trying to play the “realism” thing. But for me, that’s part of the fun. The really good games get you thinking at least a little. So bear with me.

The mysterious Tunguska blast of 1908 in Siberia is thought to have been caused by the impact of an asteroid or comet. The result was an air burst as the body exploded in the atmosphere, releasing a few-odd megatons worth of energy. The body thought to have caused the explosion is estimated to have been roughly 100 meters in diameter. A sphere of dense rock (about 3,000 kg/m^3) that size would weigh about 1.57 million metric tons. Let’s use that as our benchmark for a planetary bombardment projectile.

Let’s further imagine that you’re trying to move one of these things using some kind of towing or drive mechanism attached to the asteroid. Consider that you’re trying to move the equivalent mass of about 157 10,000-ton warhounds. Too big for towing. But maybe one can deflect an asteroid that’s already moving onto the path you want. That means latching your tow ship on to the correct face, and applying maximum thrust for however long it takes to nudge its trajectory to where you want it. In fact, most of the ideas NASA is kicking around about how to protect earth from future asteroid impacts have nothing to do with implanted H-Bombs or Bruce Willis. They use much subtler technologies that will tweak a rouge asteroid’s trajectory just enough to deflect it into missing the earth.

So, here’s an idea for a scenario. You start with a couple of warhounds with towing grapples mounted on their front ends (Use your imagination. Someday we hope to have such goodies or their equivalent available). The ships move up to a drifting asteroid (use the optional drift rules) at one end of the mat, set themselves up on two faces as shown in figure 2, and apply full drive for, say, four turns. That’s their objective. By the end of the four turns, you decide where the asteroid should be at that time, when the ships can disengage. Of course, the ships have to maintain full drive, for the whole time, and they can’t maneuver. This creates some interesting tactical problems, especially for a defending force that knows all they have to do to save the presumed target of the asteroid is to interrupt the push. Add more asteroids to the mix, and it’ll get even more interesting.

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Can the two Warhounds apply full thrust for enough turns to turn this
asteroid into a cosmic sling-stone?

I’d like to hear from anyone who tries this scenario. Tell me how it goes. What size of defending force makes this impractical for two warhounds to accomplish without the aid of a covering force?