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You're attacking a strawman. That quote makes sense in the context (basically the whole previous paragraph): The rocket as it performs ascent and then descent

You're attacking a strawman. That quote makes sense in the context (basically the whole previous paragraph): The rocket as it performs ascent and then descent undergoes some serious accelerations (way higher than a typical plane), while being built extremely delicately to minimize the mass (much tighter margins than an airliner). The rocket engine undergoes much higher stress than a jet engine. Hence all that stress can cause material fatigue and small malfunctions, while the margin for error on a rocket is extremely small. Hence if e.g. it turns out that the risk of mission failure on these reused boosters increases substantially after every use, all the anticipated savings from reusability may be quickly wiped out by one or two lost missions. And it should be noted, that the cargo that goes into space is often MUCH more expensive than the rocket itself.

avmich 8y ago
There are two problems with quoted text. First problem is "if". In "if e.g. it turns out that the risk of mission failure...". The problem is - what if not? What if those "much tighter margins" and "much higher stress" nevertheless don't translate into substantially higher - and unpredictable - mission failure risks? Then all those anticipated savings will just keep accumulating. Second problem is with costs of cargo. There are reasons why a lot of cargo going to space is expensive. A lot of those reasons are related to the incentive to make cargo working on the first try. You can't go and fix things, saying goes, so you have to make your payload reliable - on the first and often only attempt. That's a good recipe for raising costs. This is admittedly not the only reason. You can imagine unique enough telescope which would be as hard - relatively speaking - to build on Mauna Kea as it would be to launch to Sun-Earth L2. But even in those cases you could perhaps split the system, build pieces with some spares and assemble them - given that you could actually fly, repeatedly, there. And for all others less exclusive payloads, that's even more true. Now, the big reason why we usually don't consider that a viable option is because we used to think - over 60 years of Space Age - that Getting There Is Expensive. But the whole point of many efforts - of both SpaceX and their likely-minded colleagues elsewhere - is to make getting there cheaper. First somewhat cheaper, then seriously cheaper, and then commodity-level cheaper. Then we won't need to create so unique payloads - because we'll have the benefits of available extra mass, for fuel, for construction margins, for extra systems, for docking, for service flights etc. We'll do building systems more and more as we do it with orbital station - instead of building unique Skylab we launch more specialized ISS modules, and much less of them are so critical to the whole project that we need to spend so much efforts to get them right the first try. So this quote appears to me missing some important points.
Cogito 8y ago
The quote may make sense, but it's still moved the goalpost. > when one of the SpaceX boosters will have flown 100 times with between flights maintenance at an economical level, then it will be an actual success The hope is that the boosters will be able to be reused indefinitely (stated goal of 10+ for block 5 I think?) but they only need to be economical to refly once and they will be successful. There is some argument that they need to refly multiple times in order to recoup development costs, but the reality is that they are already cheaper than the competition on expendable flights. We know it's already economical, because as stated in parent they have flown reused boosters at a discount. The concern you quote above is that reused boosters are somehow more likely to fail, but the best indicator that a booster can fly is if it has already flown before. Recovering the boosters has allowed the effect of stresses during flight to be measured, and we have seen them make design modifications in response. It's plausible that this has already improved reliability of all boosters, but more importantly it means that the boosters that have been reflown (or ones like them) have been heavily investigated. Of course everyone knows that reused boosters need to be dependable, the fact that they're being reflown means that the engineers are at least reasonably confident that they're not going to blow up with the payload on top. Even if a reused booster blew up, you would need to identify that something about it being reused was at fault. If you did, and were not able to fix that issue for some reason, we still have the situation that the boosters are already cheaper in expendable mode than the competition.

avmich 8y ago

There are two problems with quoted text. First problem is "if". In "if e.g. it turns out that the risk of mission failure...". The problem is - what if not? What if those "much tighter margins" and "much higher stress" nevertheless don't translate into substantially higher - and unpredictable - mission failure risks? Then all those anticipated savings will just keep accumulating. Second problem is with costs of cargo. There are reasons why a lot of cargo going to space is expensive. A lot of those reasons are related to the incentive to make cargo working on the first try. You can't go and fix things, saying goes, so you have to make your payload reliable - on the first and often only attempt. That's a good recipe for raising costs. This is admittedly not the only reason. You can imagine unique enough telescope which would be as hard - relatively speaking - to build on Mauna Kea as it would be to launch to Sun-Earth L2. But even in those cases you could perhaps split the system, build pieces with some spares and assemble them - given that you could actually fly, repeatedly, there. And for all others less exclusive payloads, that's even more true. Now, the big reason why we usually don't consider that a viable option is because we used to think - over 60 years of Space Age - that Getting There Is Expensive. But the whole point of many efforts - of both SpaceX and their likely-minded colleagues elsewhere - is to make getting there cheaper. First somewhat cheaper, then seriously cheaper, and then commodity-level cheaper. Then we won't need to create so unique payloads - because we'll have the benefits of available extra mass, for fuel, for construction margins, for extra systems, for docking, for service flights etc. We'll do building systems more and more as we do it with orbital station - instead of building unique Skylab we launch more specialized ISS modules, and much less of them are so critical to the whole project that we need to spend so much efforts to get them right the first try. So this quote appears to me missing some important points.

Cogito 8y ago

The quote may make sense, but it's still moved the goalpost. > when one of the SpaceX boosters will have flown 100 times with between flights maintenance at an economical level, then it will be an actual success The hope is that the boosters will be able to be reused indefinitely (stated goal of 10+ for block 5 I think?) but they only need to be economical to refly once and they will be successful. There is some argument that they need to refly multiple times in order to recoup development costs, but the reality is that they are already cheaper than the competition on expendable flights. We know it's already economical, because as stated in parent they have flown reused boosters at a discount. The concern you quote above is that reused boosters are somehow more likely to fail, but the best indicator that a booster can fly is if it has already flown before. Recovering the boosters has allowed the effect of stresses during flight to be measured, and we have seen them make design modifications in response. It's plausible that this has already improved reliability of all boosters, but more importantly it means that the boosters that have been reflown (or ones like them) have been heavily investigated. Of course everyone knows that reused boosters need to be dependable, the fact that they're being reflown means that the engineers are at least reasonably confident that they're not going to blow up with the payload on top. Even if a reused booster blew up, you would need to identify that something about it being reused was at fault. If you did, and were not able to fix that issue for some reason, we still have the situation that the boosters are already cheaper in expendable mode than the competition.