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Unfortunately, they can not reuse the second stage yet and they might never be able to with Falcon 9. I think Elon has already stated as much. The payload penal
by FrojoS 12y ago
Unfortunately, they can not reuse the second stage yet and they might never be able to with Falcon 9. I think Elon has already stated as much. The payload penalty due to the required heat shield, thrusters, fuel and legs for the second stage would be too much.
For arguments sake, lets assume that the second stage was 10% of the manufacturing cost and the first stage was 90%. You could argue, that the engines are what's most expensive and the first stage has nine times as many. Ignoring the cost for lunch, landing, refuelling etc. you could at best reduce the cost by 90%, a single order of magnitude.
Unfortunately, the first stage might be worth much more. I wouldn't be surprised if the cost distribution is closer to 50-50. The second stage has all the avionics, a special vacuum version of the Merlin engine and might be more weight optimised due to the larger effect on maximum payload.
Lets hope the Mars rocket (BFR) will allow full, low cost reusability. I'm sure SpaceX is working very hard on that.
- nickhalfasleep 12y agoI wonder if instead of letting the second stage burn up, they could dock them in space somewhere to serve as material and fluid storage. They might not work for long term cryogenic storage, but a ton of pure aluminum has to be worth something up there.
- Tuna-Fish 12y agoThey launch to specific orbits desired by the customers. It might well be extremely expensive to move the second stage from these orbits to some common one where could dock.
- toomuchtodo 12y agoYes, definitely cost prohibitive from a fuel perspective to change orbits, but the vehicle could be safed for future use. I do not have enough information as to whether though would be valuable unless Tesla as some way to produce fuel on-orbit for the waiting, safed second stages.
- TeMPOraL 12y agoWell, FWIW, it works in Kerbal Space Program. But as you said, this would require for the fuel to be brought from somewhere else than Earth's gravity well. Maybe Planetary Resources will find some kerosene on a near-Earth asteroid?
- lmm 12y agoNo it doesn't, not if you launch satellites where customers want them. Kerbal Space Program should really bring home the big fundamental about orbital mechanics: plane changes are really expensive.
- TeMPOraL 12y agoThere are ways to make plane changes cheap (do them high enough, use gravity assist, etc.) and they could be useful when shipping fuel higher from Earth's gravity well, but I admit, current space missions are nowhere near that complicated. Also, while expensive, plane changes are still cheaper delta-V-wise than punching through the soup our atmosphere is.
- NamTaf 12y agoYou'd have to keep boosting it where it is, which means it needs extra thrusters. Otherwise it'll just decay. Also, changing orbits is expensive. Remember you need to change both height and angle, and the delta-V is huge. Bringing them back down is almost certainly the easiest option.
- ansible 12y agoIf the 2nd stage at least had a small solar panel and magnetic tether, it could (slowly) change orbits into something useful. Not sure what the weight penalty for a minimally viable system would be. For the 2nd stage, every gram counts, much more so than for the 1st stage.
- stcredzero 12y agoIf we could fuel tugs with material from off-planet, then it wouldn't be nearly as expensive to do this.
- mikeash 12y agoI believe they've said that the second stage is about 25% of the total cost. Not cheap by any means, but just being able to reuse the first stage will be a huge boon. Even more so for Falcon Heavy, which still has a regular second stage, but has three first stage cores.