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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

#201

Post by usrusr »

leecarraher wrote: post #168

Am i missing something, is the need to land vertically a requirement of a fragile fuselage? Seems wasteful to carry extra anything (in this case rocket propellant) to space, just to avoid having to re-right the rocket when you get it back on earth for a subsequent launch. Is extra fuel payload < landing gear or parachutes?

Lack of wings. (That's obviously for the landing gear part of the question)

But fragile fuselage is certainly spot on. Parachute-landings still have quite some impact velocity. Strengthening an object the size of a Falcon 9 first stage to survive that impact would require a much stronger and thus prohibitively heavy structure, even if the parachute itself was free. The nice thing about powered upright landing is that all the forces involved are pretty much the same as during launch so that there is little (if any) additional strengthening required.

Note also how the ULA plans for the use of parachutes to recover first stage engine blocks require the parachute to be caught in-flight by a helicopter to avoid any uncontrolled ground contact.

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

#202

Post by cjbprime »

bluthru wrote: post #122
neals wrote: post #28

I always try to watch the webcasts and I can't help but cringe so hard when they start chanting 'USA USA USA', every single time. What is up with that?

It'd be one thing if it was NASA, but a private company? What's the point?

Many of the employees have roots at NASA, so there's not such a hard boundary there.

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

#203

Post by mikeash »

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…

Now you've created a collision risk with all those pillars and cables sticking up. The rocket actually comes in from the side, because it initially aims next to the barge so that an engine failure doesn't cause it to crash into the barge. You'd have to change that approach, and your margin for error would become much smaller.

All that to solve a problem that doesn't seem to actually exist. A scheme like this might have saved the Jason-3 landing, where the rocket fell over due to a leg that didn't lock, but none of the other barge landing failures would have been helped by this.

I think there's a fundamental failure to understand the scale of this hardware, too. This is a massive machine (50 meters tall or so) built to weigh as little as possible, and therefore to only be strong where it's needed. It has approximately zero ability to withstand lateral forces from things like cables pulling it upright.

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

#204

Post by bane »

warrenmiller wrote: post #180
neals wrote: post #28

I always try to watch the webcasts and I can't help but cringe so hard when they start chanting 'USA USA USA', every single time. What is up with that?

Maybe they don't know their CEO is South African?

(nearly) All Americans are immigrants or children of immigrants.

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

#205

Post by lmm »

jacquesm wrote: post #117
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?

NASA landed a first stage on a barge to be re-used?

NASA reused every engine (not just the first stage) of an orbital payload delivery system, many times, 30 years ago. Runway rather than barge but that's not really an important difference.

(The exciting part will be much cheaper refurbishment than the STS. But SpaceX haven't actually delivered on that component yet)

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

#206

Post by kaendfinger »

neals wrote: post #28

I always try to watch the webcasts and I can't help but cringe so hard when they start chanting 'USA USA USA', every single time. What is up with that?

In my opinion, it may not necessarily be a national pride thing, as much as it's just an impulse. Because in sports, this happens often, I think it's more about showing how happy they are than crediting the United States for the accomplishments they made.

As an American (and specifically, a 16-year-old Software Engineer), growing up in the United States, this is normal, and is sometimes patriotic, sometimes an automatic response to excitement. I understand why some people might find it odd.

I don't really believe that the act of chanting "USA" is meant to alienate people. I guess you could equate it to the cultural oddities, sort of like when you travel to a different country. Some people bow, shake hands, etc for greetings, just the same way that Americans show excitement by chanting "USA", while other countries may not.

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

#207

Post by cjbprime »

Inconel wrote: post #84
neals wrote: post #55

Earlier quoted context omitted.

Because it makes the whole think look like a Trump rally. Have some class, show some dignity.

I find your insinuation that by simply chanting U-S-A an entire group of people can be described as classless and without dignity to be troubling. I work at SpaceX. I was not born in the US and although I now hold US citizenship and consider myself thoroughly American, I usually refrain from taking part in these chants. I do this not as a kind of silent protest against them, but because I simply don't like showing su…

You said you find this criticism troubling, but then you said you understand why people find these expressions of national pride troubling. I think you're supposed to pick one?

> despite the fact that I can see no way in which the U-S-A chants can possibly be misconstrued as denigrating of any other countries.

I think it's about context, right? Many countries feel some imperialist pressure coming from the USA, which makes a "USA, we're number one!" type of chant different to an "Iceland, we're number one!" chant or whatever.

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

#208

Post by Alex3917 »

dkbrk wrote: post #135
neals wrote: post #28

I always try to watch the webcasts and I can't help but cringe so hard when they start chanting 'USA USA USA', every single time. What is up with that?

It's tribalism, which is never good, no matter how common or accepted it might be in certain regions or cultures. Much the same as sports fans cheering for their teams or extreme nationalists at a political rally, chanting such as this is symtomatic of an "us versus them" and/or a "we are better than them" mentality. I feel pride in SpaceX accomplishments even though I have in no way contributed to their success beca…

> It's tribalism, which is never good, no matter how common or accepted it might be in certain regions or cultures.

If they were doing it out of tribalism they'd probably be chanting 'homegrown', which is common after a big win over competitors who recruit mostly foreigners as a way of sticking it to them.

Instead my guess is that they're doing this out of acknowledgement of the infrastructure and regulation that makes this possible.

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

#209

Post by sesutton »

mikeash wrote: post #179
LocaX wrote: post #171

Earlier quoted context omitted.

I attended a conference from the head of the CNES (Centre National d'Etudes Spatiales, ~ French NASA) in Paris a week ago and he talked about that. Ariane 6 is going to be built with a cost effective approach and trying to focus on market needs (3D printing of parts, reusability of the first stage, etc.) At first, concerning SpaceX, his group of experts told him that the design of the rocket wasn't going to work and…

I can't imagine how anyone with the slightest clue could conclude that the first stage would sink the barge. The scales are just too different; the barge outweighs the rocket by orders of magnitude. I hope this is one of those "lost in translation" things, because otherwise I fear for that group of supposed experts.

Pretty sure he means the barge would sink from the big hole he thought the rocket would put in it.

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

#210

Post by mikeash »

sesutton wrote: post #209
mikeash wrote: post #179

Earlier quoted context omitted.

I can't imagine how anyone with the slightest clue could conclude that the first stage would sink the barge. The scales are just too different; the barge outweighs the rocket by orders of magnitude. I hope this is one of those "lost in translation" things, because otherwise I fear for that group of supposed experts.

Pretty sure he means the barge would sink from the big hole he thought the rocket would put in it.

Of course, but my point is that the barge is so much more massive that the idea of punching a hole all the way through doesn't really make sense, and even if that were possible, such a small hole wouldn't sink it anyway.
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