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Space X CR6 First stage landing

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Re: Space X CR6 First stage landing

#91
post #76
post #56

Elon says it's in slow motion too "High resolution, color corrected, slow motion rocket landing video https://youtu.be/BhMSzC1crr0" https://twitter.com/elonmusk/status/588463193070022656

If it's slow motion, I suggest changing the YouTube setting to 1.25x and watching it at that speed. It seems quite natural actually. Edit: Or maybe 1.5 or 2x! I don't know..

[deleted]

Re: Space X CR6 First stage landing

#92
post #60
post #58

Earlier quoted context omitted.

The eventual goal is to land it on land, they're only doing water landings right now due to the high chance of failure. In the future, the first stage will land back at the rocket pad, which massively reduces the logistics for re-using it. There's a cool mock-up video of what that might look like: https://www.youtube.com/watch?v=4Ca6x4QbpoM

So you're saying the real cost-savings don't kick in until you're landing it back on the pad, hence salvage from sea is only important as far as perfecting the technology?

Yep. They're doing it at sea because they're in the late alpha stage of this reusable program.

Re: Space X CR6 First stage landing

#93
post #48

Question: Why don't they land into the water instead of a hard surface? (Wouldn't this give them more leeway in terms of impulse?) Edit: i.e. landing on a net stretched (under the lake/ocean-surface) by 3 or 4 ships - reel the net it in to raise stage out of the water, I'm pretty sure seawater is not significantly corrosive from 2-3 hours of exposure.

This how NASA recovered the SRBs. They landed upright, much like SpaceX's rocket. They were bouyant and floated vertically. The tender would approach the SRB, hook onto it, pump more water into it so it would sink. It would then carry it horizontally back to land.

Seawater is incredibly corrosive and as it evaporates it leaves behind a fine layer of sea salt. Since these were SRBs, they had few moving parts. They were completely disassembled and the individual components were inspected and recertified prior to the next launch.

Also, just to give you some scale of how crazy the Space Shuttle program was: the SRBs are the largest lift platform that was ever in use. ICBMs are fireworks compared to them. To land in the water, the SRBs needed not one but 3 of the largest parachutes ever produced.

Re: Space X CR6 First stage landing

#94
post #2

I can't help but feel bad for that one poor little RCS thruster doing its level best to keep the first stage upright, but ultimately running out of fuel.

Judging from the ensuing explosion there was still fuel left over.

The RCS thrusters are powered by compressed nitrogen, not the rocket fuel that powers the main engines.

Re: Space X CR6 First stage landing

#95
It's interesting to think that if you are building rockets, up til now you've never really gotten to take the rocket apart _after_ flying it - it's burnt up in the atmosphere or at the bottom of the ocean somewhere. I imagine there will be lots of interesting insights that come out of recovering, undamaged, a flown first stage and taking it apart to see what's experienced wear etc.

Re: Space X CR6 First stage landing

#97
It must be amazing working in a field where failure is almost as exciting as success.

What's the main obstacle to slowing down and stabilizing the rocket on its descent to the platform? Is it just a matter of speed or also the shape of the rocket and its center of gravity? Would a set of 3 parachutes might slow it down a little bit or at the very least straighten it before the rockets need to kick in saving some fuel?

Re: Space X CR6 First stage landing

#98
post #87

Earlier quoted context omitted.

How high did it get? Does it burn the whole way down (I assume it uses those little X-wings to 'fly down?) When does it start the descent burn? How fast is it going at this point? How much does it weigh, what sort of forces are we talking about? How hard is landing this puppy in terms of human achievement? Top 10% of tricky things humans have so far achieved? [edit] wouldn't it be easier to hover it a few meters abov…

It burns three times after the second stage detaches. The first is to get the landing zone closer to the takeoff, the second slows it down from 1300 m/s to about 250 m/s, the third slows it to (hopefully) 0 m/s on the landing pad. Here's a diagram: http://media2.s-nbcnews.com/i/newscms/2014_51/812491/141217-... If the 'x-wings' are what I think you're referring to, they're the landing legs. They are shaped like that…

Aah, grid fins were the things I was thinking of. That first burn must have some complex maths behind it. Do we know anything of their simulation software?

Re: Space X CR6 First stage landing

#99

It's interesting to think that if you are building rockets, up til now you've never really gotten to take the rocket apart _after_ flying it - it's burnt up in the atmosphere or at the bottom of the ocean somewhere. I imagine there will be lots of interesting insights that come out of recovering, undamaged, a flown first stage and taking it apart to see what's experienced wear etc.

NASA has been recovering their rockets from ocean landings for some time.

See: https://www.youtube.com/watch?v=Gbtulv0mnlU

Re: Space X CR6 First stage landing

#100
It was jaw dropping as-is, but when they finally do stick a landing I imagine the engineers will be running around like little kids screaming with the pure joy and exhilaration of it all. I hope they share the video at mission control as well when the day does come!

The sheer drama of how fast it comes down, the awesome power of the Merlin engine just blasting away delta-v... I wonder how many g's it takes on that final burn?

Would a drougue have simply added too much weight or too much complexity to deploy? I guess slowing down the freefall velocity before the burn just doesn't really help all that much?

Amazing that Falcon Heavy will have 27 Merlins on board.

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