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That's incorrect -- the reason NASA chose Starship is because it was the most capable lander for the lowest possible projected upfront cost. Government contract

by kunai 3y ago

That's incorrect -- the reason NASA chose Starship is because it was the most capable lander for the lowest possible projected upfront cost. Government contracts always attempt to maximize economic utility while meeting objectives -- any other advantages are ancillary to this. > Symmetrically, almost all problems can be solved by increasing the mass budget: more fuel to loiter longer, redundant systems, etc...Starship is so hilariously large that there's enough mass budget to solve almost any problem. Also incorrect. Mass budget does not change fundamental Newtonian physics, nor does it alter the issue of instability caused by a high center of mass. The engineers at SpaceX are very smart and I'm sure they're hard at work trying to engineer out this solution, but it's a bit like saying that you can prevent a car from rolling over if you make it heavy and powerful enough. Sure, but that causes problems and challenges of its own. It would have been easier to engineer the car to have a lower center of mass, i.e. it would be easier to land on the moon with a lander that had its mass spread out over a larger surface area and didn't have an angular moment of inertia significant enough to where topple was a concern -- like the Dynetics or BO proposals.

mr_toad 3y ago
> Also incorrect. Mass budget does not change fundamental Newtonian physics, nor does it alter the issue of instability caused by a high center of mass. The size of the ship solves some problems. Illustrations depict landing gear taller than a person, which means small rocks and holes are less of an issue.
- kevin_thibedeau 3y ago
  Landing on a sloped surface will be an issue. Apollo 15 was close to disaster on its tilted landing and Apollo 12 had a bobble when setting down. Starship is unlikely to survive the same.
  - wongarsu 3y ago
    Starship will have spare fuel and relightable engines. It could just take off when it starts tipping and go for a second landing attempt on a more even surface. The low gravity is a real pain for landing, but it makes it really easy to abort a landing too, even after touch down.
    - kevin_thibedeau 3y ago
      Except they have no depth of experience doing a non-hoverslam landing (0 on dirt) and there is a serious risk of damage from flying debris. Apollo only had 2s max to perform an abort on a known good engine. Expecting a restart to work reliably with minimal delay is ambitious.
    - matheusmoreira 3y ago
      > It could just take off when it starts tipping and go for a second landing attempt on a more even surface. ... A surprisingly kerbal solution. Wouldn't the engines be firing to control the vertical speed though? Otherwise it'll end up lithobraking at hundreds of meters per second instead of gently touching down at 1 or 2 m/s. At least that's what happens to me if I don't burn retrograde.
panick21_ 3y ago
> Government contracts always attempt to maximize economic utility while meeting objectives Lets not go overboard with the claims we make about government contracting. > instability caused by a high center of mass The center of mass is low as the engines are by far the heavies part of the rocket.
- dkbrk 3y ago
  > Lets not go overboard with the claims we make about government contracting. That's more or less true though? There's no need to debate semantics when the criteria NASA used are very clearly laid out in the source selection statement [0]. It is plain that SpaceX was selected because it met the technical requirements, provided the best value for the government, and fit within NASA's budget for the program (indeed, was the only proposal that did so). There's also the GAO report which more or less says the same thing with more detail and confirms NASA's judgement [1]. And, I'm no expert on contracting, but it is my understanding that "meeting requirements" and "achieving the best value" are criteria that are supposed to underpin all government contracts, not something unique to that particular contract. [0]: https://www.nasa.gov/wp-content/uploads/2019/04/option-a-source-selection-statement-final.pdf https://www.nasa.gov/wp-content/uploads/2019/04/option-a-sou... [1]: https://www.gao.gov/assets/b-419783.pdf https://www.gao.gov/assets/b-419783.pdf
  - panick21_ 3y ago
    > That's more or less true though? No it isn't. It was done correctly in this case. But if you study the history of NASA and DoD contracting the idea that they always perfectly evaluate is nonsense. Literally during the very selection process you talk about, a NASA employ was fired because he tried to give Boeing an unfair advantage. How many times in history was this not caught? Often the selection documents aren't public. The idea that lobbying and politics have no influence of government selection is just being naive. Just recently in commercial Crew Starliner was selected over Dreamchaser. Despite Dreamchaser being considerably cheaper, and offering much more utility. NASA just assumed that Starliner would be done fast because it was Boeing. The reality many believe without Boeing CommercialCrew would have failed. We can go threw history, as far back as you like. The Supersonic transport, you basically had Boeing proposing an absurdly complex incredibly ambitious design, despite being the company with the least amount of experience. They were selected despite the other projects being much more reasonable and much cheaper.

by kunai 3y ago

mr_toad 3y ago

> Also incorrect. Mass budget does not change fundamental Newtonian physics, nor does it alter the issue of instability caused by a high center of mass. The size of the ship solves some problems. Illustrations depict landing gear taller than a person, which means small rocks and holes are less of an issue.

kevin_thibedeau 3y ago
Landing on a sloped surface will be an issue. Apollo 15 was close to disaster on its tilted landing and Apollo 12 had a bobble when setting down. Starship is unlikely to survive the same.
- wongarsu 3y ago
  Starship will have spare fuel and relightable engines. It could just take off when it starts tipping and go for a second landing attempt on a more even surface. The low gravity is a real pain for landing, but it makes it really easy to abort a landing too, even after touch down.
  - kevin_thibedeau 3y ago
    Except they have no depth of experience doing a non-hoverslam landing (0 on dirt) and there is a serious risk of damage from flying debris. Apollo only had 2s max to perform an abort on a known good engine. Expecting a restart to work reliably with minimal delay is ambitious.
  - matheusmoreira 3y ago
    > It could just take off when it starts tipping and go for a second landing attempt on a more even surface. ... A surprisingly kerbal solution. Wouldn't the engines be firing to control the vertical speed though? Otherwise it'll end up lithobraking at hundreds of meters per second instead of gently touching down at 1 or 2 m/s. At least that's what happens to me if I don't burn retrograde.

panick21_ 3y ago

> Government contracts always attempt to maximize economic utility while meeting objectives Lets not go overboard with the claims we make about government contracting. > instability caused by a high center of mass The center of mass is low as the engines are by far the heavies part of the rocket.

dkbrk 3y ago
> Lets not go overboard with the claims we make about government contracting. That's more or less true though? There's no need to debate semantics when the criteria NASA used are very clearly laid out in the source selection statement [0]. It is plain that SpaceX was selected because it met the technical requirements, provided the best value for the government, and fit within NASA's budget for the program (indeed, was the only proposal that did so). There's also the GAO report which more or less says the same thing with more detail and confirms NASA's judgement [1]. And, I'm no expert on contracting, but it is my understanding that "meeting requirements" and "achieving the best value" are criteria that are supposed to underpin all government contracts, not something unique to that particular contract. [0]: https://www.nasa.gov/wp-content/uploads/2019/04/option-a-source-selection-statement-final.pdf https://www.nasa.gov/wp-content/uploads/2019/04/option-a-sou... [1]: https://www.gao.gov/assets/b-419783.pdf https://www.gao.gov/assets/b-419783.pdf
- panick21_ 3y ago
  > That's more or less true though? No it isn't. It was done correctly in this case. But if you study the history of NASA and DoD contracting the idea that they always perfectly evaluate is nonsense. Literally during the very selection process you talk about, a NASA employ was fired because he tried to give Boeing an unfair advantage. How many times in history was this not caught? Often the selection documents aren't public. The idea that lobbying and politics have no influence of government selection is just being naive. Just recently in commercial Crew Starliner was selected over Dreamchaser. Despite Dreamchaser being considerably cheaper, and offering much more utility. NASA just assumed that Starliner would be done fast because it was Boeing. The reality many believe without Boeing CommercialCrew would have failed. We can go threw history, as far back as you like. The Supersonic transport, you basically had Boeing proposing an absurdly complex incredibly ambitious design, despite being the company with the least amount of experience. They were selected despite the other projects being much more reasonable and much cheaper.