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SpaceX launches starship Mega-Rocket and catches its booster in midair on first try.
(www.smithsonianmag.com)
this post was submitted on 15 Oct 2024
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No, that's not really right at all. With this last flight they brought the starship above 200km (100km is generally considered the point at which you're in space), so they definitely went much higher than they needed. In low earth orbit, the velocity needed to hold that orbit is about 28000 KM/H, they kept their velocity below 27000 KM/H for safety/responsibility reasons. That way, if something failed and they couldn't relight their engines, it would naturally come down anyway in a predictable manner. The closer you get to actual orbital speeds, the less predictable the re-entry and impact location will be, so 27000 KM/H is really as high as you want to go if you want to ensure predictable re-entry. It looks like they maxed out at 26750 kmh.
Also, after they reached 95% of orbital speeds, we know they still had lots of fuel in the tank because it had enough to slow down and land exactly where they wanted it to. And then... it still had enough to explode in a huge fireball, so clearly the rocket could have gone further. Or to look at it differently, all the propellant mass that got used up in that huge explosion at the end, that could have been payload mass. So clearly it has the capacity to put up a payload as well. I think the reason they haven't yet is that mastering the reusability aspects are just a higher priority than the payload bays, I think we all trust they can design a payload bay when it comes time for that.
So what you're saying is that SpaceX deliberatly doesn't let Starship orbit, to keep reentry predictable. Which is what Lichtblitz@discuss.tchncs.de said; they don't actually orbit.
Also note that 100km is the minimum height to be "in space", not the minimum height for achieving orbit.
Finally, I disagree with the note that having "enough fuel" to reach orbit means they have demonstrated such capability; I believe they easily could achieve this, but they haven't actually demonstrated it yet.
That doesn't really mean anything. You could achieve an orbit at a lower altitude if you wanted to, it would decay faster, but you could do it. The 100km karman line is an arbitrary thing, there is no solid line where on one side you can orbit and on the other side you can't.
Well this seems like a bad semantic argument to me. I guess the question is, what does it mean to you to "demonstrate capability". Like, for you, what would be the difference between demonstrating a capability to do something and actually doing that thing? How would those two things look different? Or in this specific case, how could they have demonstrated that capability without putting their rocket into a stable orbit (because it would be negligent to do that with this prototype rocket)?
Given what they have done, is there any reason to doubt they could have gone a little bit further? And conversely, was there a good reason to stop where they were, or do you think they would have gone further if they could have?
I agree; the comment I was replying to seemed to imply that there was a minimum height requirement, or height by itself equaled orbit. But that's just my interpretation of it.
Maybe it is, but personally I prefer to see the result 100% finished. I am very impressed by the booster catch, and the non-stop camera feed on Starship was awesome, but I would like to see a full mission before saying that they reached orbit. And to me, demonstrating capability usually means doing it.