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This will be so exciting to watch, maybe as much as the first booster landing, or even more than it, if it succeeds. What I wonder about is why they never test

This will be so exciting to watch, maybe as much as the first booster landing, or even more than it, if it succeeds. What I wonder about is why they never tested catching boosters with the ones they've been using all along. They know these boosters inside out, so it would be a good platform to gain experience with.

stainablesteel 2y ago
as for why they haven't done it yet i imagine its because you can easily over optimize for something out of order, they had bigger priorities with making the launch work in 100 other ways so until those hurdles were cleared even attempting to worry about catching wasn't worth their time and manpower yet
melodyogonna 2y ago
They've been trying to launch and land the rocket at a precise point without explosion
- deleted 2y ago
  [deleted]
xoa 2y ago
>What I wonder about is why they never tested catching boosters with the ones they've been using all along. They know these boosters inside out, so it would be a good platform to gain experience with. The Falcon 9 is incapable of hovering, because given the number of Merlins and their limited ability to throttle it cannot achieve a thrust/weight ratio (TWR) of 1 even on a single engine throttled to the lowest it can go. Rockets are almost entirely fuel by weight at launch, when empty they are very light. Since it has a TWR >1 when near-empty, lighting up an engine means F9 will want to go up again. So with F9 SpaceX must do a "hoverslam" to land, wherein the computer lights the engine at just the right point such that it hits relative velocity of zero right at the altitude of the landing pad (be it on ship or on land). That won't do for catching one however. With Starship all of this was considered from the start. Raptor has better throttling capability (itself an amazing technical achievement), and of course on Super Heavy there are lots of them which is another advantage of the "many, smaller engines" approach. It means that they can effectively throttle it to just 1/33*min-throttle of max thrust. And SH is also just plain heavier construction, for good reason in an economics designed big rocket but also helpful here. Combined it is actually capable of hovering when near empty.
magicalhippo 2y ago
Apparently they landed the SH booster within half a centimeter of the target position at the last attempt. So I'd say they definitely have carried over some important lessons from Falcon 9. The actual catching part might perhaps not have been very transferable, given how Falcon 9 can't roll using it's single engine unlike Starship booster, and the large difference in mass.
- mavhc 2y ago
  how do they even measure a half centimetre accuracy?
  - magicalhippo 2y ago
    I assume they have access to the full GPS resolution. They had a ship in the vicinity AFAIK, so could use that to improve accuracy through data augmentation.
- cubefox 2y ago
  It's more likely it was half a meter and he misspoke. Landing with half a centimeter accuracy seems highly improbable.

stainablesteel 2y ago

as for why they haven't done it yet i imagine its because you can easily over optimize for something out of order, they had bigger priorities with making the launch work in 100 other ways so until those hurdles were cleared even attempting to worry about catching wasn't worth their time and manpower yet

melodyogonna 2y ago

They've been trying to launch and land the rocket at a precise point without explosion

deleted 2y ago
[deleted]

xoa 2y ago

>What I wonder about is why they never tested catching boosters with the ones they've been using all along. They know these boosters inside out, so it would be a good platform to gain experience with. The Falcon 9 is incapable of hovering, because given the number of Merlins and their limited ability to throttle it cannot achieve a thrust/weight ratio (TWR) of 1 even on a single engine throttled to the lowest it can go. Rockets are almost entirely fuel by weight at launch, when empty they are very light. Since it has a TWR >1 when near-empty, lighting up an engine means F9 will want to go up again. So with F9 SpaceX must do a "hoverslam" to land, wherein the computer lights the engine at just the right point such that it hits relative velocity of zero right at the altitude of the landing pad (be it on ship or on land). That won't do for catching one however. With Starship all of this was considered from the start. Raptor has better throttling capability (itself an amazing technical achievement), and of course on Super Heavy there are lots of them which is another advantage of the "many, smaller engines" approach. It means that they can effectively throttle it to just 1/33*min-throttle of max thrust. And SH is also just plain heavier construction, for good reason in an economics designed big rocket but also helpful here. Combined it is actually capable of hovering when near empty.

magicalhippo 2y ago

Apparently they landed the SH booster within half a centimeter of the target position at the last attempt. So I'd say they definitely have carried over some important lessons from Falcon 9. The actual catching part might perhaps not have been very transferable, given how Falcon 9 can't roll using it's single engine unlike Starship booster, and the large difference in mass.

mavhc 2y ago
how do they even measure a half centimetre accuracy?
- magicalhippo 2y ago
  I assume they have access to the full GPS resolution. They had a ship in the vicinity AFAIK, so could use that to improve accuracy through data augmentation.
cubefox 2y ago
It's more likely it was half a meter and he misspoke. Landing with half a centimeter accuracy seems highly improbable.