So I was reading this latest post over at Selenian Boondocks on lunar base economics, and in comments, someone put forth the hypothetical prize of fifty billion for a private lunar base.

I think that’s too much money, for too nebulous a goal, to be politically practicable. The real problem with all these prizes is that the government can’t be counted on to not renege. But what if there were a way to assure the winner that he’d get the money if he accomplished the goal? I think that I’ve mentioned this before, and it was actually originally suggested by someone in sci.space.policy who is generally an idiot, but perhaps a savant one, because he came up with this brilliant idea.

Drop a billion dollars worth of bullion on the lunar surface. Whoever can get up there, and bring it back, gets it. There’d be no way to pull the prize money off the table with such a scheme.

The question is, how much would it cost to implement it?

The problem is the weight.

Well, at the current price of gold, it turns out that a billion dollars is about a hundred thousand pounds. In fact, the cost of the gold that the Shuttle could launch would be roughly the cost of a Shuttle launch (about half a billion dollars). (This sort of calculation is the source of the oft-noted critique of space manufacturing: that if you had some way of alchemically converting lead to gold in LEO, it still wouldn’t be worth the money). And of course, that only gets it to LEO–it would take more pounds of stage and propellant to get it to the moon.

Would it have to be soft landed? If not, then the job’s a lot easier. You could do a grazing lithobraking maneuver with it that would save a lot of propellant, though it would leave a long and (to purists) ugly gash in the regolith that would hang around for a very long time before it was cratered over. If you just dropped it in vertically, it would just make a new (big) crater, but it would also probably make excavating for it a challenge.

But for a soft landing, let’s say (without doing any calculations) that it takes five pounds in LEO to get a pound on the surface (or subsurface). That means a half a million pounds of launch requirement. Say ten Atlas launches (again, roughly). Or about a billion bucks. So it would cost two billion dollars for the prize (ignoring development costs for the lunar descent system)–a billion for the payload and prize itself, and a billion or so to deliver it to the moon.

Clearly, we need something that has a higher dollar density than gold.

Well, there’s cold hard cash.

Of course, if it’s going to be cash, it would have to be unmarked, unserialized bills (otherwise the government could retroactively come up with a way to make them worthless). That could be done easily enough (well, not trivially, but it’s certainly doable). How much would it weigh?

According to the mint, a currency note weighs about a gram. That’s a little less than five hundred to a pound. If we use Benjamins, that means that a billion bucks would be about twenty-two thousand pounds. And unfortunately, that’s the largest note that’s made today.

There’s another problem with currency. It’s not that durable, if there’s a landing accident on the moon. Metals are better.

What are the other possibilities?

Well, there are other precious metals. For instance, the gold/platinum ratio is currently 0.55, so we could roughly halve the mission costs by using that metal instead. Rhodium would be even better. The rhodium/gold ratio is about eight right now (rhodium is just north of $5000 an ounce on the New York spot market right now), so we could reduce the lunar payload down to about ten thousand pounds with that. Of course, is there even a billion dollars worth of it available for the purpose? And how stable would its price be?

But are there things that have even higher dollar densities? Yes. Some drugs, microchips, etc. The problem is coming up with one that will hold its value. Shipping off a bunch of the latest fastest dual-core Intel processors, or eight gigabyte memory chips, would be sinking a lot of money in the project that would be almost worthless by the time someone got to them, given Moore’s inevitable Law.

Well, I’ve wasted enough time on this little trade study. Anyone have any other ideas?