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You raise a few good points. Falcon 9 launches could be 30% cheaper if fully reusable but that only reduces a launch cost down to $25M. I am skeptical of the c
by barbegal 5y ago
You raise a few good points. Falcon 9 launches could be 30% cheaper if fully reusable but that only reduces a launch cost down to $25M.
I am skeptical of the claim that they will just be able to refuel and go. Every reusable space vehicle has had that goal and always cost more than expected to refurbish for the next launch. Yes, we may get there eventually but not in the next few decades, the risks of a catastrophic component failure are too high to do no refurbishment.
The starship and super heavy are certainly cheaper to construct but that has more to do with fabrication techniques than the material cost.
Methane is less dense than kerosene so needs larger tanks but it does have more energy per unit mass. The overheads of using cryogenic fuel are reduced on a larger rocket but the performance gain is probably only 10% or so.
I am not aware of any significant insulation between tanks on the Falcon 9 and it certainly isn't a major cost factor.
- Robotbeat 5y ago> Every reusable space vehicle has had that goal and always cost more than expected to refurbish for the next launch. There have only been 2 reusable launch vehicles ever, and both were only partially reusable. Shuttle and Falcon 9. Falcon 9 has already made massive strides in reducing any refurb costs between missions. there is no reason that you couldn’t build one that requires no maintenance in between flights for the same reason that there’s no reason you can’t make an upper stage that can do multiple firings per flight without any maintenance in between. Upper stage reuse will be trickier, but ultimately there’s no fundamental reason why refurb has to be done in between every flight.
- rbanffy 5y agoUpper stage reuse doesn’t require a landing. If you could refuel an upper stage in space, you could use it for deep space exploration. Do they deliberately deorbit the Falcon second stage? Would be interesting if we could keep a couple parked in LEO and refuel them for different missions.
- bryanlarsen 5y agoBut then you need a different vehicle to refuel the original one. If you're doing that, why not just use that second vehicle for the mission and forget about reuse? Reusing second stages in space only really makes sense once you are making your fuel in space.
- rbanffy 5y agoMaking fuel on the Moon or on Mars is more or less the plan for any sustainable development of the solar system. Unless we get sci-fi grade engines, it’s just unfeasible to send fuel from Earth.
- bryanlarsen 5y agoThat's a chicken and egg problem. Making fuel off of Earth is going to require so much mass for infrastructure that it won't be feasible until we have fully reusable vehicles.
- Robotbeat 5y agoAn acquaintance of mine who works in the industry (not at SpaceX) called Raptor a “scifi engine.” For a lot of purposes, Starship should make it extremely cheap to send propellant from Earth. $10/kg in LEO. Cheaper than any lunar mining proposal I’ve seen. That said, I hope we do make propellant off-Earth eventually.
- SEJeff 5y agoYeah if I remember correctly, I read that the solar panels required to ISRU make enough methane on Mars for a starship return flight would be two football fields worth and it would take them a few years to do it.
- Robotbeat 5y agoArea is just not a huge problem on Mars or in space in general. It’s not really a relevant figure of merit, unlike mass and pre-deployed volume