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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

#351

Post by mikeash »

ctthill wrote: post #347
mikeash wrote: post #305

Earlier quoted context omitted.

Second stage recovery is a whole different beast. Recovering the first stage on a flight like this is a delicate dance because margins are so small, so everything has to go exactly right. The previous attempt (SES-9) didn't quite go exactly right, and made a big boom, perhaps because the engine burns were slightly mistimed. Recovering the second stage is difficult because it's coming in from a much higher speed. The…

KE = 0.5mv^2, so the second stage would only have 16x the kinetic energy if the two stages had the same mass. The dry mass of the first stage is approximately 25,600kg. At 2km/s, its kinetic energy is 51.2 terajoules. The dry mass of the second stage is approximately 3,900kg. At 8km/s, its kinetic energy is 125 terajoules. So the KE of the second stage is actually about ~2.4x that of the first stage. Here is were I f…

I meant relative to the mass of the stage, since that's what's relevant to the challenge.

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

#353

Post by stcredzero »

d_theorist wrote: post #109
sandworm101 wrote: post #90

Earlier quoted context omitted.

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

I think you're trying to apply rules designed to govern shipping in general to a very specialised and controlled situation.

A lot of rules around shipping actually have to do with physics. See my other comment. Shifting cargo can be very bad news. It has caused a lot of deaths. It's probably not a big deal in this case, except that booster is worth about (I'm guessing) 20 million dollars, SpaceX's cost? It's tall, but the center of gravity is low and it's on a barge.

Engineering is conservative "just in case." So are a lot of practical activities that happen on the sea. In neither case, is this irrational or a waste of time.

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

#354

Post by cletusw »

samstave wrote: post #341
cloudwalking wrote: post #313

Earlier quoted context omitted.

In space it uses nitrogen thrusters to orient. Once in the atmosphere it uses grid fins to orient. The entire liftoff and return is piloted by Falcon's flight computers -- no humans involved.

Thank you - how does the barge communicate with the falcon? And what types of comminucations are they having. I assume the barge is stating its GPS location, but does it also communicate things like sea conditions - and its elevation (what is it called to describe the condition of the sea), as well as wind, north-south orientation, etc... I am impressed - but I want to know how this works.

Rumor is (https://www.reddit.com/r/spacex/comments/3b0stk/falcon_9_wha...) that the barge does not communicate any information to the booster. Instead, it uses GPS and some ingenious motors to maintain position and orientation, and the Falcon booster uses a radar altimeter to judge accurate vertical distance.

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

#355

Post by avmich »

api wrote: post #295
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'm kind of fascinated -- and not necessarily in a good sense -- with how unbelievably conservative the aerospace industry became right after its greatest moment of glory. That would have been Apollo in 1969. Seems like after the Moon landings everyone just said "welp, that's it, nothing else will ever be done."

You probably missed the orbital stations programs. :)

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

#356

Post by a-priori »

_dark_matter_ wrote: post #182
larrydag wrote: post #174

Earlier quoted context omitted.

Here's a reason why that guy answered it that way. Note these are my definitions but I've heard it before. Scientist: Studies and uncovers mysteries of the universe and natural world Engineer: Applies what scientists discovers

Eh, I think it's simpler than that: Scientist: Unknown outcome (e.g. hypothesis -> experimentation) Engineer: Known (or should be) outcome

"In science if you know what you are doing you should not be doing it. In engineering if you do not know what you are doing you should not be doing it. Of course, you seldom, if ever, see the pure state." - Richard Hamming

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

#357

Post by zardo »

SFJulie wrote: post #339
larrydag wrote: post #188

Earlier quoted context omitted.

As an Engineer I might be a little biased but I see this is a massive achievement. We are seeing a paradigm shift in space exploration with the rise of the influence of the private sector. Space exploration used to be the domain of government entities. That is gone now. I believe we are seeing a new age of exploration not seen since the 15th and 16th centuries of discovering the "new" world. These new space companies…

As an idiot, is is less expensive than asking the NASA or the ESA, or any other providers? And well, can the "materials" really be recycled without loss of security/quality? Is the metal more expensive than the carburant/comburant?

Compared to NASA, around a 10x cost reduction. That's before reusability.

>And well, can the "materials" really be recycled without loss of security/quality?

They aren't going to recycle rockets, they're going to refly them. They are aiming for around 100 flights per airframe.

>Is the metal more expensive than the carburant/comburant?

The cost of the metal isn't the major concern, it's the cost of shaping the metal into a working rocket. But yes, fuel costs are a couple hundred thousand, rockets are tens of millions.

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

#359

Post by stcredzero »

TeMPOraL wrote: post #66
kchoudhu wrote: post #35

Earlier quoted context omitted.

Or not, because the next best alternative is much more expensive than SpaceX's current pricing. We're dealing with a corporation -- I'm not sure we can count of them to "pass on the savings".

We're dealing with a group of people with strong ideas about space. They probably won't pass on much of the savings, but for a different reason - they need the budget for Mars project. That's the whole purpose this company exists in the first place.

If they're smart (and they are) they'll figure out ways to reduce the price of launch in the right way to maximize an increase in their margins. They could more than double the number of customers using secondary space in the "trunk" and cube-sats. The secondary customers will pay far less than the primary ones, but there will be many more of them.

If they're smart, they're figuring out ways they can own a big part of the infrastructure for an emerging market.

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

#360

Post by simonh »

deanCommie wrote: post #198
simonh wrote: post #159

Earlier quoted context omitted.

> you seem to have completely missed his finer point That's because I don't think there is a finer point. If the only way a chant like that could happen is if it's started by aggro-patriotic douchebags, which specifically was the contention, then the chanting only exists as a result of aggro-patriotic douchebaggery. That's a slur that taints everyone involved in it, and I don't accept that at all.

I should not have used that term to diminish my point, I regret that. My point was that Americans can claim all day and all night that "U-S-A" chants are not meant to insult or condescend to any other country. But ask around and I can tell you most other countries find it INCREDIBLY uncomfortable. Sporting events are a completely appropriate venue for the release of testosterone and patriotism. The very nature of the…

Well I'm not a country, only a citizen of one, so maybe my opinion doesn't count as much weight as theirs.
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