5 ms·
> 20 feet long, 1 foot in diameter tungsten rods I was curious about the price of this so I did some monster math (FYI complete arms layman, serious errors are
by millstone 8y ago
> 20 feet long, 1 foot in diameter tungsten rods
I was curious about the price of this so I did some monster math (FYI complete arms layman, serious errors are likely).
Raw materials: Volume is 15.7 cu ft = 444,574.5 cm3. Density is 19.3g/cm3 = 8,580 kg. Estimated price of $30.3k per metric ton [1] = $260k in tungsten. Cheap.
Now for launch price. SpaceX advertises $90 million for 8 metric tons launched into low-earth orbit [2]. Yowza.
A single Trident submarine based missile is in the order of $65-$100 million depending on various sources. So cost-wise these seem within the same order of magnitude as nukes.
1: https://www.metalary.com/tungsten-price/ https://www.metalary.com/tungsten-price/
2: https://spacenews.com/wp-content/uploads/2016/05/spacex-price.gif https://spacenews.com/wp-content/uploads/2016/05/spacex-pric...
- ChrisGranger 8y agoThat price per ton doesn't include making it in the desired shape, though, right? Tungsten is very tough to work with, so I imagine that'd add significantly to the price, though I've no idea how much.
- tgtweak 8y agoIt would be eclipsed by the price of getting it into orbit, making it a rounding error.
- ars 8y agoIt just needs to be more or less a rod. The exact shape doesn't matter much, so there's not going to be much working it, just melt it into a rod and done. (There are some ceramics that can handle the necessary temperature.) You can also sinter it, it doesn't need to be especially strong, just hold itself together while falling, and sintering can make it strong enough. The strength plays no part at all when it impacts. At the energy involved it might as well be a noodle. It just needs to handle the heat and resistance of reentry. Mainly heat.
- taneq 8y ago> The strength plays no part at all when it impacts. At the energy involved it might as well be a noodle. It just needs to handle the heat and resistance of reentry. So why tungsten, rather than a tungsten skin on a lead bar?
- Someone 8y agowhen it impacts. You want your missile to reach the ground in one part, and you want it to have low air resistance, so that most potential energy goes into the kinetic energy at impact, rather than say, heating or melting your projectile or the air. Also, the density of tungsten is about 75% larger than that of lead. Iridium and osmium are about 15% heavier still, at about twice the density of lead (osmium is heavier, but by only 0.12%)
- mrighele 8y agoThe shape matters because you want to maximize the impact speed which means minimizing resistance of reentry. A simple rod will not keep its orientation while falling down, it needs either fins or a different shape.
- baybal2 8y agoYou actually have to decelerate rapidly, so you warheads fall at a steep angle. Gliding reentry is inaccurate
- manicdee 8y agoAt which point there’s no reason putting this thing in orbit instead of launching it as a regular ballistic missile. To hit one target on the ground you are going to need thousands of rods in orbit to ensure that one is available to use on the target. This is necessary because things in orbit will only be able to de-orbit on top of things that are close to their orbital plane.
- jacquesm 8y agoIt'd be funny if someone would try to cast it in shape by melting it.
- scrollaway 8y agoSpaceX is trying to reduce launch costs though. The closer they get to their goal of 10 million / launch, the cheaper this thing gets.