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To me this seems extremely risky. There are so many things that still need to be solved on Starship such as in LEO refueling. I hope NASA knows what they are d

To me this seems extremely risky. There are so many things that still need to be solved on Starship such as in LEO refueling. I hope NASA knows what they are doing.

thaeli 6y ago
It _is_ very risky, but the source selection statement lays out in great detail how both other bids were much worse.
toomuchtodo 6y ago
SpaceX needs to solve this to go to Mars, NASA is simply paying them to learn (similar to how full fare launches allowed them to learn to reuse the first stage and keep it for themselves).
HPsquared 6y ago
I don't want to sound too cavalier, but launching and landing are objectively hard - need a combination of power and finesse. Isn't refuelling just connecting a pipe and an ullage motor?
- the-dude 6y ago
  For example, the internet is just a bunch of pipes. How hard can it be?
  - HPsquared 6y ago
    The propellant depot is just a big truck, not a series of tubes.
- ceejayoz 6y ago
  https://en.wikipedia.org/wiki/Propellant_depot#Engineering_design_issues https://en.wikipedia.org/wiki/Propellant_depot#Engineering_d... has a pretty good list of concerns.
  - JulianMorrison 6y ago
    Starship's idea of (1) you send the fuel up in another Starship and (2) you refuel by bumping uglies and then accelerating in a direction that makes the fuel simply fall into the empty vehicle, together solves a lot of problems that imply a static depot.
bryanlarsen 6y ago
Dynetics also required refueling and the National Team required assembly in NHRO. SpaceX was seen as less risky than the other two because their refueling was in low Earth orbit and was done prior to human launch.
bpodgursky 6y ago
There would be many other core unsolved technical challenges if they had gone with a traditional system like the SLS. For example: - Standing it upright - Fueling it - Launching - Building it End of the day, Starship is a new and not-fully-proven design, but (parts of it) _have_ launched, and NASA knows that SpaceX is committed to the vision either way. Much better than a contractor design which exists only on paper and only to win a bid.
themgt 6y ago
Worth noting orbital refueling may not actually be that difficult, it was strongly rumored that Senate Launch System backers put the kibosh on refueling because it would jeopardize the SLS jobs program if it worked: "We had released a series of papers showing how a depot/refueling architecture would enable a human exploration program using existing (at the time) commercial rockets," Sowers tweeted on Wednesday. "Boeing became furious and tried to get me fired. Kudos to my CEO for protecting me. But we were banned from even saying the 'd' word out loud. Sad part is that ULA did a lot of pathfinding work in that area and could have owned the refueling/depot market, enriching Boeing (and Lockheed) in the process. But it was shut down because it threatened SLS." https://arstechnica.com/science/2019/08/rocket-scientist-says-that-boeing-squelched-work-on-propellant-depots/ https://arstechnica.com/science/2019/08/rocket-scientist-say...
avmich 6y ago
Orbital refueling is done for decades; e.g. Progresses supplied Soviet space stations with fuel to maintain the orbit. What's trickier is orbital refueling of cryogenic liquids - LOX, liquid methane. It still looks easier than refueling with LH2, and ULA did a lot of work with that (search for "propellant depot"). Active cooling might be required; humanity had experience storing cryogenics in space for long time (e.g. Buran, which used LOX for RCS, was able to store it for a month on orbit), but we still might want a better solution (the one which actively turns vapors back into the liquid phase using onboard energy and radiators). Yet there is little which seems too complex in the refueling idea.
- m4rtink 6y ago
  IIRC ULA had a plan to run an internal combustion engine off the hydrogen/oxygen boil off, providing power for stage systems and or cooling/recondenser in their ACCESS upper stage concept. Of course ideally you don't want to loose any propelants to boil off but it still seems like a nice idea.
spaetzleesser 6y ago
I hope they will go back to pushing the limits more again. Since the Space Shuttle and now the SLS they got stuck in a rut and iterated very slowly. It’s unbelievable how long the SLS, which basically repeats what has been done 50 years ago, is taking and how much it costs. Better put that money into several programs that have a chance of failing but will also deliver new technology.
- unchocked 6y ago
  Yup. Break the tyranny of mission assurance.
2OEH8eoCRo0 6y ago
I had it the other way around. I was worried about SpaceX overselling their actual capabilities until NASA gave them the contract.
mlindner 6y ago
NASA rated SpaceX's approach equal or better in technical areas and management areas than the competitors, and it was the cheapest.
spfzero 6y ago
Much more need to be solved for the other two options, so the choice seems logical. Whether the best option is a good enough option, is a different question.
itslennysfault 6y ago
They should also solve for that whole explosion thing it's been doing. (This is mostly a joke I'm sure they will)

To me this seems extremely risky. There are so many things that still need to be solved on Starship such as in LEO refueling. I hope NASA knows what they are doing.

thaeli 6y ago

It _is_ very risky, but the source selection statement lays out in great detail how both other bids were much worse.

toomuchtodo 6y ago

SpaceX needs to solve this to go to Mars, NASA is simply paying them to learn (similar to how full fare launches allowed them to learn to reuse the first stage and keep it for themselves).

HPsquared 6y ago

I don't want to sound too cavalier, but launching and landing are objectively hard - need a combination of power and finesse. Isn't refuelling just connecting a pipe and an ullage motor?

the-dude 6y ago
For example, the internet is just a bunch of pipes. How hard can it be?
- HPsquared 6y ago
  The propellant depot is just a big truck, not a series of tubes.
ceejayoz 6y ago
https://en.wikipedia.org/wiki/Propellant_depot#Engineering_design_issues https://en.wikipedia.org/wiki/Propellant_depot#Engineering_d... has a pretty good list of concerns.
- JulianMorrison 6y ago
  Starship's idea of (1) you send the fuel up in another Starship and (2) you refuel by bumping uglies and then accelerating in a direction that makes the fuel simply fall into the empty vehicle, together solves a lot of problems that imply a static depot.

bryanlarsen 6y ago

Dynetics also required refueling and the National Team required assembly in NHRO. SpaceX was seen as less risky than the other two because their refueling was in low Earth orbit and was done prior to human launch.

bpodgursky 6y ago

There would be many other core unsolved technical challenges if they had gone with a traditional system like the SLS. For example: - Standing it upright - Fueling it - Launching - Building it End of the day, Starship is a new and not-fully-proven design, but (parts of it) _have_ launched, and NASA knows that SpaceX is committed to the vision either way. Much better than a contractor design which exists only on paper and only to win a bid.

themgt 6y ago

Worth noting orbital refueling may not actually be that difficult, it was strongly rumored that Senate Launch System backers put the kibosh on refueling because it would jeopardize the SLS jobs program if it worked: "We had released a series of papers showing how a depot/refueling architecture would enable a human exploration program using existing (at the time) commercial rockets," Sowers tweeted on Wednesday. "Boeing became furious and tried to get me fired. Kudos to my CEO for protecting me. But we were banned from even saying the 'd' word out loud. Sad part is that ULA did a lot of pathfinding work in that area and could have owned the refueling/depot market, enriching Boeing (and Lockheed) in the process. But it was shut down because it threatened SLS." https://arstechnica.com/science/2019/08/rocket-scientist-says-that-boeing-squelched-work-on-propellant-depots/ https://arstechnica.com/science/2019/08/rocket-scientist-say...

avmich 6y ago

Orbital refueling is done for decades; e.g. Progresses supplied Soviet space stations with fuel to maintain the orbit. What's trickier is orbital refueling of cryogenic liquids - LOX, liquid methane. It still looks easier than refueling with LH2, and ULA did a lot of work with that (search for "propellant depot"). Active cooling might be required; humanity had experience storing cryogenics in space for long time (e.g. Buran, which used LOX for RCS, was able to store it for a month on orbit), but we still might want a better solution (the one which actively turns vapors back into the liquid phase using onboard energy and radiators). Yet there is little which seems too complex in the refueling idea.

m4rtink 6y ago
IIRC ULA had a plan to run an internal combustion engine off the hydrogen/oxygen boil off, providing power for stage systems and or cooling/recondenser in their ACCESS upper stage concept. Of course ideally you don't want to loose any propelants to boil off but it still seems like a nice idea.

spaetzleesser 6y ago

I hope they will go back to pushing the limits more again. Since the Space Shuttle and now the SLS they got stuck in a rut and iterated very slowly. It’s unbelievable how long the SLS, which basically repeats what has been done 50 years ago, is taking and how much it costs. Better put that money into several programs that have a chance of failing but will also deliver new technology.

unchocked 6y ago
Yup. Break the tyranny of mission assurance.

2OEH8eoCRo0 6y ago

I had it the other way around. I was worried about SpaceX overselling their actual capabilities until NASA gave them the contract.

mlindner 6y ago

NASA rated SpaceX's approach equal or better in technical areas and management areas than the competitors, and it was the cheapest.

spfzero 6y ago

Much more need to be solved for the other two options, so the choice seems logical. Whether the best option is a good enough option, is a different question.

itslennysfault 6y ago

They should also solve for that whole explosion thing it's been doing. (This is mostly a joke I'm sure they will)