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SpaceX lands rocket at sea second time after satellite launch

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Re: SpaceX lands rocket at sea second time after satellite launch

#121

Post by taneq »

ohitsdom wrote: post #98
SagelyGuru wrote: post #94

Good work! I still think that they should have some grippers on the barge, or a net, ready to spring and grasp the rocket on landing, instead of carrying flimsy legs all the way to space and back.

The current legs aren't flimsy, and they seem way less complicated than a gripper system would have to be. How would a gripper system handle off-centered landings? It would have to catch the falling rocket very quickly because there's not much fuel left in the tank to hover. Your proposed system would add a lot of complexity, all for the small decrease in launch mass.

I'm still surprised there's no active system on the barge to secure the rocket. Even now they seem to be able to stick the landing with some reliability, it's always nice to have belt and suspenders.

I'm thinking a system with a pillar at each corner of the barge, pairs of cables between opposite pillars, and puller cables to open out the main cables into an iris-type aperture which can be rapidly closed on the rocket after it lands to keep it upright. Do that at 2-3 heights above the barge and it'll cradle the rocket even in heavy seas.

Re: SpaceX lands rocket at sea second time after satellite launch

#123

Post by taneq »

throwaway2016a wrote: post #118
mabbo wrote: post #99

Earlier quoted context omitted.

I suppose this is why people say "it's not rocket science".

Slightly off topic but I was watching a television show the other day and someone said they worked at NASA. The host then said "So you're literally a rocket scientist?" And the guy said emphatically "Rocket engineer, there is a big difference" I'm sure this particular task probably was a little bit of both. After all, they had to run several real world experiments to prove their calculations.

It's important to know the difference: https://i.imgur.com/r6oEhvS.jpg?1

The most interesting work is right in the intersection of the two disciplines, though. :)

Re: SpaceX lands rocket at sea second time after satellite launch

#124

Post by JshWright »

taneq wrote: post #121
ohitsdom wrote: post #98

Earlier quoted context omitted.

The current legs aren't flimsy, and they seem way less complicated than a gripper system would have to be. How would a gripper system handle off-centered landings? It would have to catch the falling rocket very quickly because there's not much fuel left in the tank to hover. Your proposed system would add a lot of complexity, all for the small decrease in launch mass.

I'm still surprised there's no active system on the barge to secure the rocket. Even now they seem to be able to stick the landing with some reliability, it's always nice to have belt and suspenders. I'm thinking a system with a pillar at each corner of the barge, pairs of cables between opposite pillars, and puller cables to open out the main cables into an iris-type aperture which can be rapidly closed on the rocke…

The center of mass of the rocket is _very_ low. According to Elon, the CRS-8 core was very stable (it needed even less stabilization than they thought it did).

They may add some means to secure it if it needs to travel through rough seas on the way home, but if the conditions are calm enough to land, they're calm enough for the stage to be stable. Watch the CRS-8 landing and look at how much the barge is rolling while the stage is parked on it...

Re: SpaceX lands rocket at sea second time after satellite launch

#125

Post by sylvinus »

sandworm101 wrote: post #90
d_theorist wrote: post #88

Earlier quoted context omitted.

Somehow I suspect they have run the numbers.

What numbers? Unsecured cargo is unsecured cargo. A metal object sitting on a flat metal deck gets tied/braced/chained.

They mentioned multiple times that because the stage is empty, its center of gravity is much lower than what you'd expect.

Re: SpaceX lands rocket at sea second time after satellite launch

#126

Post by [deleted] »

Inconel wrote: post #116
TeMPOraL wrote: post #87

Earlier quoted context omitted.

I don't see how chanting for a group, without any implicit or explicit diminishment of other groups compares to hate speech against sexual minorities. Also, chants are not a company policy, it's what employees spontaneously do in their own private space, which you saw on their own private broadcast. (If we're bringing SJW approach into this, then I think you're advocating the minority (SpaceX employees) should adapt…

I too find it hard to see how so many have conflated chanting for a group, in this case the USA, as being equivalent to actively admonishing another group. The employees at SpaceX aren't burning the flags of foreign countries or otherwise disrespecting or mocking them, they are simply expressing pride in the nation that many of us view as playing an instrumental part in our success. I also don't know what could be do…

[deleted]

Re: SpaceX lands rocket at sea second time after satellite launch

#127

Post by chipaca »

robbiemitchell wrote: post #113
manaskarekar wrote: post #100

Hosted webcast: https://youtu.be/L0bMeDj76ig Landing at 38:18mins https://youtu.be/L0bMeDj76ig#t=38m18s Great info on the thrusters on the first stage at 19:37. https://youtu.be/L0bMeDj76ig#t=19m37s Edit: Thank you and sorry about the time stamp link, I posted quickly from my phone. Hopefully it works on shortlinks.

You link directly a specific place by adding this to the URL: #t=38m18s

you can also make it a query parameter, which often works better. E.g. https://youtu.be/L0bMeDj76ig?t=38m18s

Re: SpaceX lands rocket at sea second time after satellite launch

#128

Post by fixermark »

geon wrote: post #112
ohitsdom wrote: post #98

Earlier quoted context omitted.

The current legs aren't flimsy, and they seem way less complicated than a gripper system would have to be. How would a gripper system handle off-centered landings? It would have to catch the falling rocket very quickly because there's not much fuel left in the tank to hover. Your proposed system would add a lot of complexity, all for the small decrease in launch mass.

> because there's not much fuel left in the tank to hover They can't hover at all, since the throttle doesn't go low enough. They need to do the landing perfectly, on a single try.

Interesting. That's a change from the Grasshopper testing platform? If I recall correctly, it was able to hover.

Re: SpaceX lands rocket at sea second time after satellite launch

#129

Post by wolf550e »

Artemis2 wrote: post #119
zupreme wrote: post #115

I remain confused about why SpaceX is getting so much fanfare and praise. What have they accomplished that NASA didn't already accomplish during the Apollo missions? I know SpaceX is doing it all more cost effectively, because we have better technology, but have they actually accomplished anything tangible that NASA didn't a generation ago?

Did NASA land anything else than the Space Shuttle?

Closest NASA got to this (besides the STS) was DC-X.

Re: SpaceX lands rocket at sea second time after satellite launch

#130

Post by fixermark »

zupreme wrote: post #115

I remain confused about why SpaceX is getting so much fanfare and praise. What have they accomplished that NASA didn't already accomplish during the Apollo missions? I know SpaceX is doing it all more cost effectively, because we have better technology, but have they actually accomplished anything tangible that NASA didn't a generation ago?

Unfortunately, it's worth noting that while NASA's achievements were extremely laudable, it's an open question whether they could reproduce the results in a short timeframe. Some of the technologies of the Apollo era have been misplaced (either within NASA's large body of hard-copy material or never transferred from private contractors who have gone away).

SpaceX is exciting because they're doing launches and landings right now, reliably and successfully.

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