4 ms·

Also, my understanding is that initially there was supposed to be a corss-feed system that would increase the total delta-V considerably, but it isn't ready yet

by ilogik 9y ago

AshleyGrant 9y ago
That was initially the plan. It proved too complex and has since been dropped from the design. It won't be coming back. Which is too bad, because it would be really awesome if they had managed to make it work.
- garmaine 9y ago
  Do you have a source?
  - AshleyGrant 9y ago
    https://twitter.com/elonmusk/status/726561442636263425 https://twitter.com/elonmusk/status/726561442636263425
    - 0xffff2 9y ago
      That doesn't imply that cross-feed isn't coming back, only that it isn't needed for the capabilities Musk posted.
      - AshleyGrant 9y ago
        While that single statement might not imply that it's gone for good, everything Elon and SpaceX have publicly stated leads one to the conclusion that it isn't ever going to happen. Heck, Falcon Heavy has turned out to be a much larger engineering problem than originally thought even without asparagus staging (cross-feed) due to issues with reinforcing the center core to handle the loads from the side cores. Based on Musk's latest presentation regarding BFR, it seems that Falcon Heavy will be a somewhat short-lived launch platform. Then again, with SpaceX, plans change early and often...
- valuearb 9y ago
  SpaceX's genius has never been getting the absolute maximum possible thrust out of engines. It's been designing them so they can be mass produced inexpensively, and re-used. They've proven that is the far more important skill. So making the Falcon Heavy work as simply and well as possible is the important part. Getting another 10% by making crossfeed work, at the cost of making it more complex, harder to build and re-use, simply wouldn't be worth it.
  - hinkley 9y ago
    Reproducible results is a skill set unto itself.
  - nickik 9y ago
    I think it would be worth it if they were not already looking working on BFR. Falcon Heavy can fly for a couple of years now and it can handle current demands. They will open up to next level capability with a next level vehicle.
    - mikeytown2 9y ago
      I bet if Elon could turn back the clock he'd skip F9H and going straight to BFR. F9's Payload to LEO numbers have been going up; first design: 10,450 kg, current: 22,800 kg. On paper when Heavy was designed it was 25,000 kg to LEO.
      - nickik 9y ago
        I'm not sure. There are some things that the FH can do, military and space tourism and maybe a couple other things. Might be worth doing before the BFR, we will have to see how often i launches. We just don't have the numbers, I would love to see the internal accounting of these projects.
        samcat116 9y ago
        I'd argue that if they put the engineering effort into BFR that much earlier, we might have a vehicle by now that can meet those demands as well as be a much better mars vehicle.
- grondilu 9y ago
  > It proved too complex and has since been dropped from the design. It won't be coming back. SpaceX plans to do in-orbit refueling for its BFR, though. I may be oversimplifying, but it seems to me this is a fairly similar feat than cross-feeding. Couldn't the experience gained in this help for that?
  - trothamel 9y ago
    Not really. In orbit, you can transfer your fuel slowly, gently, and the receiving tank doesn't have to be under pressure. During launch, you need the receiving tanks to be at 50-100 PSI for the rocket to work, which probably means the fuel being pumped at a pressure that is much higher.
nbanks 9y ago
I wonder if they throttle back the central booster to ensure its fuel lasts longer than the two outside boosters. This is likely far easier than the cross-feed system though it would lower the total thrust.
- schiffern 9y ago
  Bingo! http://www.spacex.com/falcon-heavy http://www.spacex.com/falcon-heavy "Shortly after liftoff the center core engines are throttled down. After the side cores separate, the center core engines throttle back up to full thrust."

Also, my understanding is that initially there was supposed to be a corss-feed system that would increase the total delta-V considerably, but it isn't ready yet

by ilogik 9y ago

Also, my understanding is that initially there was supposed to be a corss-feed system that would increase the total delta-V considerably, but it isn't ready yet

AshleyGrant 9y ago

That was initially the plan. It proved too complex and has since been dropped from the design. It won't be coming back. Which is too bad, because it would be really awesome if they had managed to make it work.

garmaine 9y ago
Do you have a source?
- AshleyGrant 9y ago
  https://twitter.com/elonmusk/status/726561442636263425 https://twitter.com/elonmusk/status/726561442636263425
  - 0xffff2 9y ago
    That doesn't imply that cross-feed isn't coming back, only that it isn't needed for the capabilities Musk posted.
    - AshleyGrant 9y ago
      While that single statement might not imply that it's gone for good, everything Elon and SpaceX have publicly stated leads one to the conclusion that it isn't ever going to happen. Heck, Falcon Heavy has turned out to be a much larger engineering problem than originally thought even without asparagus staging (cross-feed) due to issues with reinforcing the center core to handle the loads from the side cores. Based on Musk's latest presentation regarding BFR, it seems that Falcon Heavy will be a somewhat short-lived launch platform. Then again, with SpaceX, plans change early and often...
valuearb 9y ago
SpaceX's genius has never been getting the absolute maximum possible thrust out of engines. It's been designing them so they can be mass produced inexpensively, and re-used. They've proven that is the far more important skill. So making the Falcon Heavy work as simply and well as possible is the important part. Getting another 10% by making crossfeed work, at the cost of making it more complex, harder to build and re-use, simply wouldn't be worth it.
- hinkley 9y ago
  Reproducible results is a skill set unto itself.
- nickik 9y ago
  I think it would be worth it if they were not already looking working on BFR. Falcon Heavy can fly for a couple of years now and it can handle current demands. They will open up to next level capability with a next level vehicle.
  - mikeytown2 9y ago
    I bet if Elon could turn back the clock he'd skip F9H and going straight to BFR. F9's Payload to LEO numbers have been going up; first design: 10,450 kg, current: 22,800 kg. On paper when Heavy was designed it was 25,000 kg to LEO.
    - nickik 9y ago
      I'm not sure. There are some things that the FH can do, military and space tourism and maybe a couple other things. Might be worth doing before the BFR, we will have to see how often i launches. We just don't have the numbers, I would love to see the internal accounting of these projects.
      - samcat116 9y ago
        I'd argue that if they put the engineering effort into BFR that much earlier, we might have a vehicle by now that can meet those demands as well as be a much better mars vehicle.
grondilu 9y ago
> It proved too complex and has since been dropped from the design. It won't be coming back. SpaceX plans to do in-orbit refueling for its BFR, though. I may be oversimplifying, but it seems to me this is a fairly similar feat than cross-feeding. Couldn't the experience gained in this help for that?
- trothamel 9y ago
  Not really. In orbit, you can transfer your fuel slowly, gently, and the receiving tank doesn't have to be under pressure. During launch, you need the receiving tanks to be at 50-100 PSI for the rocket to work, which probably means the fuel being pumped at a pressure that is much higher.

nbanks 9y ago

I wonder if they throttle back the central booster to ensure its fuel lasts longer than the two outside boosters. This is likely far easier than the cross-feed system though it would lower the total thrust.

schiffern 9y ago
Bingo! http://www.spacex.com/falcon-heavy http://www.spacex.com/falcon-heavy "Shortly after liftoff the center core engines are throttled down. After the side cores separate, the center core engines throttle back up to full thrust."