5 ms·

Even if it landed perfectly how is it going to be rapidly reusable with all those tiles breaking and needing repair? Then if that problem was magically engineer

Even if it landed perfectly how is it going to be rapidly reusable with all those tiles breaking and needing repair? Then if that problem was magically engineered-away through some sort of materials science breakthrough, it still makes more sense to me to keep your big ships in a space staging area and your smaller ones as atmospheric gophers.

s1artibartfast 4mo ago
Small ships are less efficient, especially leaving the gravity well. Thats the whole point
- JPLeRouzic 4mo ago
  Could you tell me more? I suppose a heavy two-stage rocket is not optimized from the point of view of the rocket equation, but I know nothing about this field.
  - s1artibartfast 4mo ago
    In short, the more stages the better to discard mass once it isnt necessary, and the larger to the better to improve the ratio of (ship+payload) to fuel. Here is a decent summary. https://gemini.google.com/share/121466b300c1 https://gemini.google.com/share/121466b300c1
    - kibwen 4mo ago
      This is only true to an extent. Yes, a larger rocket means a better mass:payload ratio, but a larger rocket also means more mass in absolute terms, and more mass means more fuel, and more fuel means more mass, and more mass means more fuel, and more fuel means more mass, and so on. This is "the tyranny of the rocket equation", and it places an upper bound on the size of rockets that need to carry their own fuel for a given gravity well. And because the larger absolute mass of a larger rocket means more fuel, which means more cost, it relies on actually being able to find enough paying customers to fill out that payload capacity every single time. This is why, for example, despite the existence of jumbo jets (which have a better mass:payload ration than smaller planes), most passenger flights are not on jumbo jets, because there's just not enough demand on most routes.
      - murderfs 4mo ago
        > This is why, for example, despite the existence of jumbo jets (which have a better mass:payload ration than smaller planes), most passenger flights are not on jumbo jets, because there's just not enough demand on most routes. Airlines used to use a hub and spoke model where it would make sense to have larger planes between hubs and smaller ones to get to and from the hubs, but consumers strongly preferred direct routing, so it didn't work out. For orbital payloads, most payloads probably do not mind too much if it takes a month or more to boost/deboost themselves to their intended orbits.
      - NetMageSCW 4mo ago
        No it doesn’t matter if the payload is full or not. If they succeed in full reuse, flying on a mostly empty Starship will be ten times cheaper than flying on an F9 and that means everything will switch eventually. If a jumbo jet was ten times more efficient than a smaller plane, they would go everywhere. If a giant pickup truck got a 100MPG, why would you take a 30MPG economy sedan anywhere?
      - s1artibartfast 4mo ago
        You fundamentally misunderstand the implications of the rocket equation. It does not put and upper limit on rocket size for a given gravity. Smaller rockets would not be successful where larger fail. Due to strucrually efficiency, larger ones suceede where smaller fail due to higher m0/mf ratio
laughing_man 4mo ago
All what tiles breaking and needing repair? There was remarkably little visible damage this time around compared with previous flights. There's no materials science breakthrough needed -- the shuttle used ceramic tiles successfully its entire service life. What's needed is engineering work, and that's what SpaceX has been doing.
- fooblaster 4mo ago
  You know a whole the size of a quarter can wreck the entire spacecraft and make it effectively throw away? Also, you'd want to use this many times. Making a system robust while not requiring months of refurbishment is really really hard.
  - ceejayoz 4mo ago
    The Space Shuttle had that problem because it was aluminum with a much lower melting point. It’s one of the reasons they’re using steel. We’ve seen much larger holes than that in previous tests. Some of the control fins burned completely through.
  - GuB-42 4mo ago
    For some of the tests, they removed a few tiles before launch, presumably to test that. Starship did fine.
    - fooblaster 4mo ago
      coming back in one piece, and being good enough to use for 5 more missions are two very different things. For example, all existing reentry vehicles come back "fine" but they need to be completely remade to go up again.
      - ceejayoz 4mo ago
        I remember this being the same argument used against the Falcon 9 when it first stuck its landings. "Oh, they'll need to do it 10x to be profitable!" Now they do, as a matter of course.
NetMageSCW 4mo ago
They’ve already demonstrated they can replace all the tiles in a couple of days - even if they continue to have some fall off it won’t be an issue.

s1artibartfast 4mo ago

Small ships are less efficient, especially leaving the gravity well. Thats the whole point

JPLeRouzic 4mo ago
Could you tell me more? I suppose a heavy two-stage rocket is not optimized from the point of view of the rocket equation, but I know nothing about this field.
- s1artibartfast 4mo ago
  In short, the more stages the better to discard mass once it isnt necessary, and the larger to the better to improve the ratio of (ship+payload) to fuel. Here is a decent summary. https://gemini.google.com/share/121466b300c1 https://gemini.google.com/share/121466b300c1
  - kibwen 4mo ago
    This is only true to an extent. Yes, a larger rocket means a better mass:payload ratio, but a larger rocket also means more mass in absolute terms, and more mass means more fuel, and more fuel means more mass, and more mass means more fuel, and more fuel means more mass, and so on. This is "the tyranny of the rocket equation", and it places an upper bound on the size of rockets that need to carry their own fuel for a given gravity well. And because the larger absolute mass of a larger rocket means more fuel, which means more cost, it relies on actually being able to find enough paying customers to fill out that payload capacity every single time. This is why, for example, despite the existence of jumbo jets (which have a better mass:payload ration than smaller planes), most passenger flights are not on jumbo jets, because there's just not enough demand on most routes.
    - murderfs 4mo ago
      > This is why, for example, despite the existence of jumbo jets (which have a better mass:payload ration than smaller planes), most passenger flights are not on jumbo jets, because there's just not enough demand on most routes. Airlines used to use a hub and spoke model where it would make sense to have larger planes between hubs and smaller ones to get to and from the hubs, but consumers strongly preferred direct routing, so it didn't work out. For orbital payloads, most payloads probably do not mind too much if it takes a month or more to boost/deboost themselves to their intended orbits.
    - NetMageSCW 4mo ago
      No it doesn’t matter if the payload is full or not. If they succeed in full reuse, flying on a mostly empty Starship will be ten times cheaper than flying on an F9 and that means everything will switch eventually. If a jumbo jet was ten times more efficient than a smaller plane, they would go everywhere. If a giant pickup truck got a 100MPG, why would you take a 30MPG economy sedan anywhere?
    - s1artibartfast 4mo ago
      You fundamentally misunderstand the implications of the rocket equation. It does not put and upper limit on rocket size for a given gravity. Smaller rockets would not be successful where larger fail. Due to strucrually efficiency, larger ones suceede where smaller fail due to higher m0/mf ratio

laughing_man 4mo ago

All what tiles breaking and needing repair? There was remarkably little visible damage this time around compared with previous flights. There's no materials science breakthrough needed -- the shuttle used ceramic tiles successfully its entire service life. What's needed is engineering work, and that's what SpaceX has been doing.

fooblaster 4mo ago
You know a whole the size of a quarter can wreck the entire spacecraft and make it effectively throw away? Also, you'd want to use this many times. Making a system robust while not requiring months of refurbishment is really really hard.
- ceejayoz 4mo ago
  The Space Shuttle had that problem because it was aluminum with a much lower melting point. It’s one of the reasons they’re using steel. We’ve seen much larger holes than that in previous tests. Some of the control fins burned completely through.
- GuB-42 4mo ago
  For some of the tests, they removed a few tiles before launch, presumably to test that. Starship did fine.
  - fooblaster 4mo ago
    coming back in one piece, and being good enough to use for 5 more missions are two very different things. For example, all existing reentry vehicles come back "fine" but they need to be completely remade to go up again.
    - ceejayoz 4mo ago
      I remember this being the same argument used against the Falcon 9 when it first stuck its landings. "Oh, they'll need to do it 10x to be profitable!" Now they do, as a matter of course.

NetMageSCW 4mo ago

They’ve already demonstrated they can replace all the tiles in a couple of days - even if they continue to have some fall off it won’t be an issue.