4 ms·

Rocket books are written by scientists, not economists or MBAs. Elon Musk's major innovation with SpaceX was to look at it from a business & economic angle rath

by sfifs 4y ago

Rocket books are written by scientists, not economists or MBAs. Elon Musk's major innovation with SpaceX was to look at it from a business & economic angle rather than the angle of scientists or millitary industrial complex which thrives on Cost Plus contracts. It turns out fuel cost rarely exceeds 10% of the cost of launch even with the tyranny of rocket equation. Traditional expendable rockets (including SLS) essentially throw away 90% of the cost of each launch - hence the push by SpaceX to some of the fuel to try and land the first stage.

matheusmoreira 4y ago
I initially thought rockets were not reusable because it was literally impossible to reuse them. I thought the launch and reentry damaged them beyond repair. Reentry modules require huge heat shields to protect the craft from being destroyed by atmospheric ablation. How is it possible for these things to launch into high altitudes and not only survive reentry but land safely? It does sound kind of stupid to just let the engines and stages free fall into the ocean now that you mentioned it. I'm not sure how advanced Musk's rockets are but if they can land safely after being staged then that's an amazing innovation. Why isn't NASA all over this if it's so revolutionary?
- sfifs 4y ago
  They are currently reusing the first stage which is sub orbital - ie. Much slower, less re-entry forces. Still a major economic benefit for overall rocket cost. That said, Starship is planned to land from orbit & be reusable - let's see. NASA is all over it from what I see - SpaceX has essentially captured virtually all of the commercial launch market and a good chunk of defence and science markets except for hyper specialized requirements or non-US defence launches. I however don't see how NASA could have developed it given the politics involved with its funding essentially incentives Project thinking over Product thinking - I actually use that as an example when I contrast Project vs Product at work. SpaceX had to blow a couple of dozen rockets AFAIK to get to a stage where they land reliably - doubt NASA could have justified that to the US Congress. NASA's funding incentives encourage a risk averse approach to engineering ever since the very high profile failures in space shuttle and the early Mars missions. Witness how the Mars helicopter was rated for a low single digit of missions and has now completed a few dozens.
  - pfdietz 4y ago
    > Much slower, less re-entry forces. I should point out it isn't forces that matter for entry from orbital speed, it's heating.
- themadturk 4y ago
  Spacecraft that require protection from re-entry are going far, far faster than first stages, so slowing them down using atmospheric friction creates a lot of heat. The Falcon first stage gets to about 8,000 kph and reaches over 100 km before it starts coming down, not high or fast enough to create the stresses an orbital re-rentry vehicle sees. The other key to reusability is having enough leftover fuel to land, control surfaces and restartable engines. Restartable engines weren't proven to work until the Gemini program in the mid-1960s, if I remember right; I'm sure the Saturn rockets was well into development by that time and the engineering costs to make major changes the lower stages were too great. Sometimes government gets set upon a course and it's very hard to redirect it; that's why innovators like Space-X are so valuable.
- m4rtink 4y ago
  There were quite a few proposals for how to reuse rockets stages - actually you can see more the farther you go. Certainly it could have been partially due to not yet having enough experience with many real world launches. But at the same time a lot of the funding was comming from ICBM programs that don't really care for reuse by design & from army and a high profile space race with USSR. That kinda favored the expensive get-it-done fast expensive MVP instead of a more complex reusable solution that could be much cheaper in the long run. And then the status quo took root & reusable rocket proponens were no longer taken seriously because - what were they thinkig, this is how we have always been doing it!
  - Throwawayaerlei 4y ago
    "And then the status quo took root & reusable rocket proponens were no longer taken seriously because - what were they thinkig, this is how we have always been doing it!" Disagree as someone who as a kid watched this happen in real time. The Saturn V follow on was always planed to be reusable, with a huge first stage booster that was something of a bigger brother of the stage that would make it to orbit. NASA was starved for capital after Apollo and this resulted in the horribly deadly and very expensive to operate kludge of the eventual Space Shuttle.

by sfifs 4y ago

matheusmoreira 4y ago

I initially thought rockets were not reusable because it was literally impossible to reuse them. I thought the launch and reentry damaged them beyond repair. Reentry modules require huge heat shields to protect the craft from being destroyed by atmospheric ablation. How is it possible for these things to launch into high altitudes and not only survive reentry but land safely? It does sound kind of stupid to just let the engines and stages free fall into the ocean now that you mentioned it. I'm not sure how advanced Musk's rockets are but if they can land safely after being staged then that's an amazing innovation. Why isn't NASA all over this if it's so revolutionary?

sfifs 4y ago
They are currently reusing the first stage which is sub orbital - ie. Much slower, less re-entry forces. Still a major economic benefit for overall rocket cost. That said, Starship is planned to land from orbit & be reusable - let's see. NASA is all over it from what I see - SpaceX has essentially captured virtually all of the commercial launch market and a good chunk of defence and science markets except for hyper specialized requirements or non-US defence launches. I however don't see how NASA could have developed it given the politics involved with its funding essentially incentives Project thinking over Product thinking - I actually use that as an example when I contrast Project vs Product at work. SpaceX had to blow a couple of dozen rockets AFAIK to get to a stage where they land reliably - doubt NASA could have justified that to the US Congress. NASA's funding incentives encourage a risk averse approach to engineering ever since the very high profile failures in space shuttle and the early Mars missions. Witness how the Mars helicopter was rated for a low single digit of missions and has now completed a few dozens.
- pfdietz 4y ago
  > Much slower, less re-entry forces. I should point out it isn't forces that matter for entry from orbital speed, it's heating.
themadturk 4y ago
Spacecraft that require protection from re-entry are going far, far faster than first stages, so slowing them down using atmospheric friction creates a lot of heat. The Falcon first stage gets to about 8,000 kph and reaches over 100 km before it starts coming down, not high or fast enough to create the stresses an orbital re-rentry vehicle sees. The other key to reusability is having enough leftover fuel to land, control surfaces and restartable engines. Restartable engines weren't proven to work until the Gemini program in the mid-1960s, if I remember right; I'm sure the Saturn rockets was well into development by that time and the engineering costs to make major changes the lower stages were too great. Sometimes government gets set upon a course and it's very hard to redirect it; that's why innovators like Space-X are so valuable.
m4rtink 4y ago
There were quite a few proposals for how to reuse rockets stages - actually you can see more the farther you go. Certainly it could have been partially due to not yet having enough experience with many real world launches. But at the same time a lot of the funding was comming from ICBM programs that don't really care for reuse by design & from army and a high profile space race with USSR. That kinda favored the expensive get-it-done fast expensive MVP instead of a more complex reusable solution that could be much cheaper in the long run. And then the status quo took root & reusable rocket proponens were no longer taken seriously because - what were they thinkig, this is how we have always been doing it!
- Throwawayaerlei 4y ago
  "And then the status quo took root & reusable rocket proponens were no longer taken seriously because - what were they thinkig, this is how we have always been doing it!" Disagree as someone who as a kid watched this happen in real time. The Saturn V follow on was always planed to be reusable, with a huge first stage booster that was something of a bigger brother of the stage that would make it to orbit. NASA was starved for capital after Apollo and this resulted in the horribly deadly and very expensive to operate kludge of the eventual Space Shuttle.