SpaceX News

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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TDPerk
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Re: SpaceX News

Post by TDPerk »

Why facepalm?

Do you have any link purporting to show Russian engines are characteristically good at turning potential ISP into into ISP?
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erblo
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Re: SpaceX News

Post by erblo »

That article is referring to the AJ26-58 (aka NK-33) used on the first stage of the Antares. Which happens to be considered by many as the best LOX/RP-1 engine ever made... It has about 20 sec higher ISP than the SpaceX Merlin 1D, which uses a GG-cycle. They might be designed in the 60´s and more expensive, but they are definitely not less fuel-efficient.

mvanwink5
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Re: SpaceX News

Post by mvanwink5 »

SpaceX has pointed out that fuel cost is a very small cost fraction of a space launch. The rocket itself is the big dog. Musk thinks strategically, and that is in terms of $'s. Only academics think without $'s, so they think efficiency is important.
Near term, cheap, dark horse fusion hits the air waves, GF - TED, LM - Announcement. The race is on.

93143
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Re: SpaceX News

Post by 93143 »

The size of the whole rocket and its manufacturing, transportation, and launch infrastructure are proportional the mass of propellant required, which is proportional to exp(1/efficiency). The costs associated with the hardware and infrastructure tend to correlate fairly well with their size.

It's only people who for some reason don't realize this that talk about propellant cost like that. Nobody cares about propellant cost; it's everything else that kills you.

Of course efficiency isn't the only criterion, but SpaceX is hardly the first to realize that. For example, the Merlin 1 can be considered a descendant of Fastrac, a NASA engine design project intended to produce a relatively small, inexpensive kerosene engine that was still decently efficient. In other words, NASA was doing exactly what SpaceX did, only several years earlier...

Look at Sea Dragon. Or OTRAG. It's called "minimum-cost design", and it's not a new concept. The extremes of it do tend to have significant disadvantages that may or may not show up on the balance sheet, which is probably part of why SpaceX has toned it down quite a bit...

JLawson
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Re: SpaceX News

Post by JLawson »

93143 wrote:In other words, NASA was doing exactly what SpaceX did, only several years earlier..."
Only SpaceX decided it was a usable concept and ran with it, while NASA seemed to be using it as a 'Well, we've got budget without much to spend it on, so let's make something to use it' sort of thing. 48 test firings, and it was dropped well over a decade ago.

It's not enough to go "Hey, that's kind of neat..." and put it on the shelf. You've got to actually do something with it.

(Wouldn't it be funny if somewhere on an unremembered shelf in a long-disused NASA warehouse is a functioning antigravity device from the '60s, cancelled because (a) it wasn't noisy enough, (b) didn't create a massive spectacle as it rose on massive columns of flame and (c) didn't require an extremely expensive massive nationwide manufacturing infrastructure? After all, you've got to uphold the image, right?)
When opinion and reality conflict - guess which one is going to win in the long run.

mvanwink5
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Re: SpaceX News

Post by mvanwink5 »

d) not in the policy manual.
Near term, cheap, dark horse fusion hits the air waves, GF - TED, LM - Announcement. The race is on.

93143
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Re: SpaceX News

Post by 93143 »

The problem is that NASA keeps getting jerked around by a fickle government and hobbled by dysfunctional management.

Fastrac was roughly the same era as SLI, and for roughly the same reasons. SLI was part of a sustained (and repeatedly frustrated) effort by NASA to lower the cost of launch to orbit (what, you thought they gave up after X-33?), and was canned in the wake of STS-107 by the Bush administration, when NASA was massively reoriented towards manned exploration by the VSE, and... let's just leave it there.

Thing is, without NASA's work over the past decades (as well as their direct support), SpaceX would never have been started, never mind actually gotten anywhere. This includes lessons learned from failed programs as well as the heritage of success. Newton himself acknowledged that he was standing on the shoulders of giants, but some people seem to think that SpaceX or someone like them would have brought us sci-fi utopia decades ago if NASA hadn't gotten in the way...

mvanwink5
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Re: SpaceX News

Post by mvanwink5 »

It is a part of the government, what could go wrong?
Near term, cheap, dark horse fusion hits the air waves, GF - TED, LM - Announcement. The race is on.

TDPerk
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Re: SpaceX News

Post by TDPerk »

I'm not sure the Russians having one engine which may be best in class, makes it true Russian engines generally are best in class. In fact, I recall most Russian launches as being far smokier than American ones (when the liftoff is good, failures aren't counted here).

"That article is referring to the AJ26-58 (aka NK-33) used on the first stage of the Antares."

I think instead they are referring to Russians engines generally at that point.
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93143
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Re: SpaceX News

Post by 93143 »

Tom Agan wrote:Another similar space venture is still using fuel-inefficient surplus Russian rocket engines built in the 1960's that cost more to run and maintain over time.
No, he's definitely talking about Orbital's Antares and "AJ-26", unless there's another new venture using '60s-vintage Russian engines that I haven't heard of...

And yes, Russian kerolox rocket engines are best-in-class. NK-33, RD-180, RD-170... all high-pressure oxidizer-rich staged combustion designs that trounce any American kerolox engine soundly in the efficiency arena (with the debatable exception of the RS-84). The latter two get about the same performance at sea level as the Merlin 1D does in vacuum. The NK-33's Isp doesn't quite match theirs (though it still walks all over the Merlin 1D), but its T/W is nearly as high as the Merlin's, which is very impressive for a staged-combustion design, especially one built in the '60s... (Hell, the RD-107/108 - the Soyuz main engine, and the exception to the efficiency rule - was designed in the '50s, and it roughly matches the Merlin 1D's vacuum Isp despite operating at a little over half its chamber pressure...)

This is just another example of somebody assuming facts not in evidence based on a general bias. He was trying to talk up the Merlin, so he slagged off the NK without checking to see whether his description was actually true. SpaceX may have come up with a better balance of efficiency, T/W, manufacturability, and maintainability (not saying anything about reliability yet), but as far as straight efficiency is concerned? Nope.

Also, what's with "cost more to run and maintain over time"? Neither company has demonstrated stage recovery and reuse yet, and only SpaceX is even trying... It may well be true in principle, but I doubt this guy knows that; I suspect this comment came from the same place as the "fuel-inefficient" one...

(The RD-0124 seems to have the same Isp at sea level as the NK-33 gets in vacuum. I didn't know a kerolox engine could do that. Russian kerolox engines are the shit...)

jcoady
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Re: SpaceX News

Post by jcoady »


TDPerk
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Re: SpaceX News

Post by TDPerk »

"No, he's definitely talking about Orbital's Antares and "AJ-26""

No, that's what the Antares uses. The Nk33 is not all Russian engines, or even all the LOX/RP1 engines.
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93143
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Re: SpaceX News

Post by 93143 »

I'm afraid your post comes across to me as a compound reading comprehension fail. Not counting the fact that you apparently didn't read past the first sentence of my post.

JLawson
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Re: SpaceX News

Post by JLawson »

93143 wrote:The problem is that NASA keeps getting jerked around by a fickle government and hobbled by dysfunctional management.
Very much so. Fund (x), then two years later pull it, then four years later restore funding, then two years later cut it again, and then point at their lack of consistent progress as proof they're a mess. Managers can only do so much when they don't have any real constancy in the income stream. Hell of a way to run a railroad.

And their management... well, I've got to admit, where's the incentive to do a good job? If you actually manage to conserve resources so you're not badly affected by budget swings - you're likely to get your budget cut under the old 'use it or lose it' method of government planning. And you can't be ambitious, because once you get up to speed you're likely to get your financing yanked. Talk about a 'worst of both worlds' sort of mess.
93143 wrote:Thing is, without NASA's work over the past decades (as well as their direct support), SpaceX would never have been started, never mind actually gotten anywhere. This includes lessons learned from failed programs as well as the heritage of success. Newton himself acknowledged that he was standing on the shoulders of giants, but some people seem to think that SpaceX or someone like them would have brought us sci-fi utopia decades ago if NASA hadn't gotten in the way...
Actually, I'm grateful to NASA for the work they've done, even handicapped as they are.


If SpaceX had been funded the same way NASA has been over the last decade or two, I don't think there'd be much of a record of success. As the saying went in the movie "The Right Stuff" - 'No bucks, no Buck Rogers'

A consistent level of funding is more important for the long run than anything else, I think.
When opinion and reality conflict - guess which one is going to win in the long run.

polyill
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Re: SpaceX News

Post by polyill »


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