J-2S vs RLX vs RS-68r+

PurduesUSAFguy · 2006-01-24 09:28:12

With NASAs problems developing an airstartable and simplified RS-24 there has been talk (I don't know if there is official word yet or not) on developing the stick with a five segment SRB instead of the existing four and using a dual J-2S upper stage.

The five segment SRB doesn't worry me; it has been studied in internal ATK studies for several years and is simply a new assembly of existing components that are in production, simple, and at least in aerospace terms, cheap.

What worries me is the choice of the J-2S, an engine that while developed, has not ever been in production, not to mention was designed in the late sixties and early 70s. I don't know if a modern J-2S rolling off the Rocketdyne assembly lines would have improved performance or not but, as is the twin J-2s lack 6% the thrust of the single RS-25 and is likely what prompted the downsizing of the CEV to a 5M diameter.

As far as safety is concerned I know that expander cycle engines are significantly safer then turbopump fed ones as there are far less catastrophic failure modes, but that being said I think that the one benefit of the J-2S over the SSME is likely counteracted by having two engines, twice the parts that can fail, and if you have one failure you have to deal with off axis thrust to such a degree I'm not sure if gimballing on those engines could handle it.

So that got me wondering, are there any engines existing or near existence that might foot the bill for the upper stage of the crew launcher?

The RLX was an engine that was at a significant development level when it was canceled when SLI went under. It had problems for its SLI application because of being a split expander engine, which isn't great for ground launch. Essentially though, it's modernized and enlarged RL10 with provisions for reusability from what I understand. If developed as an expendable engine it would be even more similar to the RL10 and simpler. The RLX has the potential to significantly out perform the modernized J-2S. How much more time consuming/expensive would it be to revive the RLX vs. the J-2S?

For that matter the existing RS-68 is an engine that has high thrust then the SSME and is currently in production. As is the RS-68 is unsuitable for this use since it has a significantly lower ISP then the SSME and is heavy. I suspect that a lot of that weight is associated with it's current ablative nozzle, which if replaced with a regenerativly cooled one (I think) would allow for a high ISP as well as weight savings. What else could be done to tweak the RS-68?

I'm just spitballing, it seems like there aren't really any options that don't involve some engine development, but my question is, is reviving an Apollo era engine really our best bet here?

Also how does this affect the Cargo launcher? Are the problems associated with air start or with streamlining the engine for a cheaper unit cost for expendable use?

GCNRevenger · 2006-01-24 11:34:11

The good ol' SSME is a real (expensive too) beast, and NASA is rightly concerned that they can't build them. The J-2 was a good enough engine in its day, and is slated for use on the big CaLV EDS stage since it can be restarted while SSME (nor RS-68) can't be restarted. Making the SSME fire repeatedly would require too much of a change. Its quite possible that reviving J-2 for TheStick might be easier then modifying SSME, and NASA is going to do it anyway... You are right, that reliability is a concern, but NASA absolutely has to get the Moon program, not just the CEV, started as soon as possible to avoid cancelation by the next administration. It might be worth a slightly reduced reliability.

The trouble with the RS-68 is that a regenerative nozzle would probobly not be any lighter (carbon versus metal), and the engine itself operates at a much lower pressure then SSME does. So, its not likly that the RS-68 can be modified to have similar Isp to the SSME. It also isn't anywhere near man-rated like the J-2 is.

The five-segment SRB is not just like the four segment, because ATK calls for using a different fuel mixture, probobly to slow down the burn rate to keep thrust from getting out of hand. NASA needs the CEV sooner rather then later, which is why they picked the regular four-segment engine. I agree that the five-segment engine is a better deal, but it would take time that Griffin doesn't think he has.

PurduesUSAFguy · 2006-01-24 17:43:18

The good ol' SSME is a real (expensive too) beast, and NASA is rightly concerned that they can't build them. The J-2 was a good enough engine in its day, and is slated for use on the big CaLV EDS stage since it can be restarted while SSME (nor RS-68) can't be restarted. Making the SSME fire repeatedly would require too much of a change. Its quite possible that reviving J-2 for TheStick might be easier then modifying SSME, and NASA is going to do it anyway... You are right, that reliability is a concern, but NASA absolutely has to get the Moon program, not just the CEV, started as soon as possible to avoid cancelation by the next administration. It might be worth a slightly reduced reliability.
The trouble with the RS-68 is that a regenerative nozzle would probobly not be any lighter (carbon versus metal), and the engine itself operates at a much lower pressure then SSME does. So, its not likly that the RS-68 can be modified to have similar Isp to the SSME. It also isn't anywhere near man-rated like the J-2 is.
The five-segment SRB is not just like the four segment, because ATK calls for using a different fuel mixture, probobly to slow down the burn rate to keep thrust from getting out of hand. NASA needs the CEV sooner rather then later, which is why they picked the regular four-segment engine. I agree that the five-segment engine is a better deal, but it would take time that Griffin doesn't think he has.

I didn't know that NASA was planning on using the J-2S on the Earth Departure Stage, that actually makes alot of sense to use as many of the same engines as possible.

I still am worried about the RS-25s cost for the Cargo launcher though, is that what they are still planning on?

GCNRevenger · 2006-01-24 18:27:33

Oh I agree, that using five SSMEs may be ruinously expensive (we're talking $200-250M versus $60M for four standard RS-68s if they can't make a "discount" model), but the financial cost isn't the only consideration here (obviously), since if the SSME shop was closed down then the Stennis Space Center would cease to exsist, and so the political cost might be too high. The lower Isp of the RS-68 would reduce maximum payload by a little too.

NASA came to the conclusion that modifying the SSME for multiple firings was probobly harder then just building one for air-start/high-altitude use and reviving the old J-2, so the HLLV will likly have two or three on the EDS stage. The SSME really is a monsterously complex beast.

Edit: About the only way that SSME makes sense is if you could reuse those five engines, but an engine pod contraption is going to be a whole lot of trouble. I really can't see why NASA is going for it instead of a quartet of RS-68 other then politics. "But its reuseable!" has been a deception since the beginning.

PurduesUSAFguy · 2006-01-24 19:58:00

Oh I agree, that using five SSMEs may be ruinously expensive (we're talking $200-250M versus $60M for four standard RS-68s if they can't make a "discount" model), but the financial cost isn't the only consideration here (obviously), since if the SSME shop was closed down then the Stennis Space Center would cease to exsist, and so the political cost might be too high. The lower Isp of the RS-68 would reduce maximum payload by a little too.
NASA came to the conclusion that modifying the SSME for multiple firings was probobly harder then just building one for air-start/high-altitude use and reviving the old J-2, so the HLLV will likly have two or three on the EDS stage. The SSME really is a monsterously complex beast.
Edit: About the only way that SSME makes sense is if you could reuse those five engines, but an engine pod contraption is going to be a whole lot of trouble. I really can't see why NASA is going for it instead of a quartet of RS-68 other then politics. "But its reuseable!" has been a deception since the beginning.

How much aerospace evil has been justified by 'reuseablity'? The Shuttle, X-30, X-33, SLI....I have my doubts that I'll see as you put it a 'no kidding' reusable launcher before I have grandkids. (I'm 20)

Commodore · 2006-01-24 20:12:47

Getting a EDS-class rocket to do a couple dozen burns over the course of a year in space is far more usefull than one that can reenter.

GCNRevenger · 2006-01-24 20:24:11

Answer: A whole lot

No orbital space vehicle in the world has ever bennefited from reuseability to this day...... but that said, the promise they offer is still the only way that we will ever (ever) really establish mankind anywhere other then Earth... Barring the invention of a space elevator, anti-gravity drive, or teleportation of course. Due to the energies, materials, and engineering expendable rockets are never ever be cheap enough for true colonization.

That said, I think that a true RLV is ways off: how far depends on what you could use it (or something like it) for besides colonization.
-Mining the Moon for Platinum/He3?
-Military space bomber?
-Civilian space hotel tender?
-Orbital manufacture of zero-G only substance/device?

If colonization is the only "customer" for such a craft, I expect it will be at least 35-45 years until the first flight of such a vehicle, if NASA is the only one supplying the majority of the funding (if they get the go ahead for colonization at all). If there is another use for such a vehicle, or a vehicle like it, then we might see it come sooner. If colonization doesn't happen, we might not see such a vehicle for a very very long time.

Private funding sources using derivitives of military technology maybe... although that would take the entire life savings of all the colonists and then some to make that happen.

SpaceNut · 2006-01-24 22:07:47

I am wondering about how Nasa is using the Stennis Space Center and the United Space Alliance for the making of engines for the Shuttle. Since no new shuttles have been made and no engines replaced, then the center is only rebuilding and testing them for each shuttle to use them.

As far as the RS-83,84 and others that were part of the Space Launch Initative(SLI) these all got the axe when the vision was anounced even before anyone had really given any thought about what could be used to carry out the vision.

GCNRevenger · 2006-01-24 22:14:39

The USAF has spent a little bit continuing research on a sucessor to SSME, but thats a looong way down the road, if memory serves. Integrated powerhead engine or something like that.

Stennis is mainly around to try and keep the SSMEs going and build new ones as needed now and then. It takes a huge amount of work to take one apart and refurbish it.

SpaceNut · 2006-01-24 22:42:20

Have poaked around a little bit more on engines that were part of pad abort an other projects that were stopped such as the RS-88 Boeing Successfully Tests New Engine for NASA Program

The 50,000-pound-thrust engine was designed and built by Boeing for use on Lockheed Martin's Pad Abort Demonstration (PAD) vehicle, scheduled for launch in late 2005. The vehicle will carry four RS-88 engines.

The RS-68 engine liquid hydrogen / liquid oxygen fueled producing a thrust of 650,000 lbf (2.9 MN) at sea level and 745,000 lbf (3.3 MN) in a vacuum; to compare a Space Shuttle Main Engine (SSME) produces 1.8 MN at sea level. If used, only three RS-68 engines would be used instead of the five SSME engines needed for launch. But this would be for the HLV not the CLV.

Austin Stanley · 2006-01-25 04:22:16

I've been wondering about this for some time. One the main points of the SSME concept was that it was an at least semi-reusable engine. Other engines of course can be restarted for multiple firings if necessary, but they were still disposable. The SSME was the first (as far as I know) engine that was designed to be recovered and reused considerably. They take the things back to Stenis, give them a look over, test fire them, and then remount them on the shuttle. I think they are good for 20 or so firings. The fact that this is possible at all should seem to bode well for their re-start in vacume. I just wonder why this is (apparently) not the case.

But it also occurs to me that using a SSME as an upper stage engine realy is sub-optimal. Unlike some other more general purpose, rocket engines, they truely were designed for their role in the shuttle. As a first stage recoverable engine, they realy are first class, high ISP, hight thrust, proven reliability, and reusability. So if at all possible, this is the role in which they should be used. There high cost does make throwing them away rather wastefull. On the other hand, their high cost and complexity are probably at least partialy due to their high performance characteristics. I wonder how much cost a "mass produced" SSME or scaled up J-2 would cost in comparision.

So they should be used on the first stage of our HLLV, they are more expensive, but they are undoubtably the best at what they do. The requirments are very similar to those for which they were initialy designed after all. No other engine comes close in terms of Thrust and ISP. There cost means they should not be thrown away if possible. I know GCRN's objections to an "engine pod" with the things, but I wonder if such a concept might be worthwhile in the end anyways. The HLV is going to be around for quite a while (hopefully) so maybe some investment in this now makes some sense.

I've also been thinking that since the HLV is going to have an upper stage which performs it's circulisation burn as well as injection burn, it might be possible to launch the engines on a balistic path which eliminates the need for some sort of OMS to facilitate their re-entery.

Politicaly speaking, Stenis is probably still going to be around as a engine test sight if nothing else. But continuing SSME production would also be a nice bone to throw them. I also think it's a shame to have developed such a wonderful engine and then just throw it away.

GCNRevenger · 2006-01-25 07:39:57

The SSME startup procedure, since it operates at such extremely high pressure and temperature, is very complex; many valves must be opened and closed in a particular sequence at exactly the right time for the engine to properly ignite. You would need to carry an additional Helium bottle for tank pressurization, and you would need some kind of small thruster to effect propellant settling. The big reason is though it was never intended to be fired in the icy vacuum of space nor more then once between careful inspection and refurbishing. Just look at the thing, does it look like its going to be easy to make a "cheap" version or modify it to ignite in the freezing vacuum after hours or days of the initial firing with minimal fuel "weight" versus sunny Florida at 1G? Even if it were reliable enough to fire repeatedly between overhauls, which its not.

SSME

The SSME as an upper stage makes great sense if your lower stage is under-powerd (CLV), or you have a really big payload (HLLV). There is just that niggling issue of getting it to air start and/or fire more then once per mission. Trouble is, this performance comes at too high a complexity.

NASA needs the CEV, and it needs it now, and so whichever engine is used for the upper stage needs to be as closely based off the SSME or J-2S as is practical. Scaling up the J-2 isn't happening, it would be nice if you could squeeze a few more percent of thrust out of it, but no serious alterations to it are nessesarry or desireable. Perhaps NASA ought to focus on taking the current "luxury model" SSME and just make it work first, and then make a simplified model later.

The SSME has fantastic Isp for a first stage, but only at altitude. During the first minute or two of acent, the air pressure is high compared to how much the propellant gasses expand, and so actually the RS-68 is dead even for Isp until getting up high. Then there are the gravitational losses to consider, and a quartet of RS-68s would have 16% more thrust then a quintet of SSMEs, and so using them instead should not cost as much payload as simple calculations indicate.

The only thing "wonderful" about the SSME is its high Isp at altitude and above-average reliability, thats it, thats all, period, end quote. In every other respect, its a terrible piece of equipment, and its especially a joke given its design purpose of reuseability. Due to its very high complexity, the thing cost tripple at least what expendable engines (RS-68, RD-0120) do per-thrust.

Now lets not start this engine pod debate again, we've been over this before. Even with a self-righting ballistic reentry, you still:
-Need a heat shield at least 8m wide, and if it must be bigger then this, it will stick out the edges of the main tank.
-Need power, communications, tracking, and mission control for it
-Route fuel lines, structural connections, and wiring through the heat shield
-Airbags, parachutes, altimiters, airspeed indicator, accelerometers, etc
-Must resist impacts greater then designed for (soft Shuttle landing)
-Must not be damaged by plasma wake during reentry or hypersonic air

Just as importantly though, if you lose the thing, you are in big trouble. How long does it take to build a new one? How much does that cost? If you have a time-sensitive launch (say, a Mars departure window) and your engine pod burns up then you can't put it on the next one. So how much does multiple backup pods cost? Or what if there is a snafu durring refurbishing/recovery?

Then there is the development... how much is THAT going to cost? Four RS-68s cost about $60-80M a flight, so unless recovery, refurbishing, and amoratizing construction costs anywhere close to this then I'm sure the development cost will wipe out any real cost advantage. Which you will have traded for having a proven, easy, fast arrangement that reduces the risk NASA will "run out of steam" politically before ever getting the HLLV off the ground if development drags on.

The SSME is a bad deal for the first stage

Apollo · 2006-01-25 15:52:44

hello anyone on?

RobertDyck · 2006-01-26 08:36:03

Use RD-0120 for the upper stage of The Stick. It has the same thrust, engine mass, and slightly higher specific impulse as SSME. SSME has 453 in vacuum, RD-0120 has 455 in vacuum. RD-0120 is available and cheaper. The only catch is it can't be reused, it's a single launch engine. If that's the application for The Stick, we have a perfect match.

The scheduled upgrade for SSME is a copy of RD-0120 technology: replace the welded expanding tubes of the exhaust cone with a cone made of two sheets: inner is smooth metal, outer has flow channels pressed into it. It's only welded at the top and bottom, it's brazed between the channels by applying brazing compound before assembly then baking it in an oven to complete the braze. The result is fewer welds, fewer leaks, greater reliability, and chaper to make.

It also has only 1 preburner and 1 turbine. The LOX and LH2 turbo-pumps are connected on a single shaft to that single turbine. That means fewer parts than SSME; again cheaper and more reliable. It also means the complex control system to balance LOX with LH2 is replaced by a simple drive shaft.

Remember, I'm the one who contacted KBKhA to ask if it's available. It is, they just need a new CNC milling machine; they kept all plans and jigs. Most importantly, they're willing to swallow the cost of re-tooling on the condition they get a solid order.

A cheap, single use version of SSME is already available, why re-invent the wheel? Concentrate on developing something new, and most importantly "Get your ass to Mars."

SpaceNut · 2006-01-26 11:38:21

Sounds like after a little research that the RD-120 engine would be a good sub for the SME. The added fact that testing and some modificational work for other propellants makes for the possible use in othe designs.
A couple of versions were for Methane while the Lox/ LH2 was capable of being throllted back. The final version was a tri-propellant design of kerosene, LH2 and LOX..

GCNRevenger · 2006-01-26 14:09:03

Use RD-0120 for the upper stage of The Stick. It has the same thrust, engine mass, and slightly higher specific impulse as SSME. SSME has 453 in vacuum, RD-0120 has 455 in vacuum. RD-0120 is available and cheaper. The only catch is it can't be reused, it's a single launch engine. If that's the application for The Stick, we have a perfect match.
The scheduled upgrade for SSME is a copy of RD-0120 technology: replace the welded expanding tubes of the exhaust cone with a cone made of two sheets: inner is smooth metal, outer has flow channels pressed into it. It's only welded at the top and bottom, it's brazed between the channels by applying brazing compound before assembly then baking it in an oven to complete the braze. The result is fewer welds, fewer leaks, greater reliability, and chaper to make.
It also has only 1 preburner and 1 turbine. The LOX and LH2 turbo-pumps are connected on a single shaft to that single turbine. That means fewer parts than SSME; again cheaper and more reliable. It also means the complex control system to balance LOX with LH2 is replaced by a simple drive shaft.
Remember, I'm the one who contacted KBKhA to ask if it's available. It is, they just need a new CNC milling machine; they kept all plans and jigs. Most importantly, they're willing to swallow the cost of re-tooling on the condition they get a solid order.
A cheap, single use version of SSME is already available, why re-invent the wheel? Concentrate on developing something new, and most importantly "Get your ass to Mars."

Why not the RD-0120? Since it isn't made here.

-Russia could hold veto over the American space program, just say "oop, no more engines," which leaves us stuck with space vehicle designs that don't work

-I think its very likly that the Russians lied to you, Robert. They lie about lots of things, and suddenly being able to build engines again sounds pretty unlikly to me. The Russians have lied and stabbed NASA in the back over the ISS, and just hold up shipments while blackmailing us. "At least its cheaper then SSME, heh heh" etc.

-It won't be American, NASA doesn't have to consider the political cost of buying Russian engines versus the financial of not simply going to an alternative to SSME, but to outsource VSE booster engine procurement to another country. Congressmen seeing money not shift states, but leave the country entirely.

If you think Congressmen have a hard time swallowing VSE pricetags now, just wait until you tell them that a good chunk of it is going to pay Russia. This is different then buying Soyuz/Progress, which is a temporary arrangement, but rather the vehicles we will be using for the next thirty years or more.

-Time: who is to say that Russian can restart production in a timely fasion? If NASA had to, they could go ahead and build full Shuttle-class SSME engines for the CEV and worry about making a simplified expendable version or use RS-68 later for the HLLV.

And frankly, it offends my sense of patriotism that the US would have to stoop to buying a dead Russian engine since we can't modify ours thats in production or that we're gonna build anyway (J-2, RS-68).

RobertDyck · 2006-01-26 18:14:44

So instead NASA and American contractors will piss around talking about modifying SSME, but never will, until finally they give up and The Stick gets cancelled. Yet another program that never got completed.

It's time to give the "not invented here" crap a break. Invent something new and let someone else who has something to sell do so. LET'S GET ON WITH IT!

By the way, the party I worked for in the Canadian federal election lost. I got my candidate to support the idea of a Canadian built fully reusable space taxi. You know, that 4 astronaut thing I've been talking about for years: SSTO, RLV, HTHL. This party is the one that built the Avro Arrow in the 1950s, the other party cancelled it. Now the other party is in power again. :cry: They want more military, stop repaying the debt, and nickel-and-dime tax cuts. They promised to decrease the GST from 7% to 6%, then further to 5% after 5 years. Of course that 5 years means they would have to be re-elected. Those small tax cuts mean no chance of paying off the debt. If the debt was gone we could eliminate the GST all together; but no, they won't do that. Their idea of a child care program is give every parent $25 per week for a year then cancel the whole thing. They want a free vote to cancel same-sex mariage, and are even talking about getting rid of abortion (Canadian laws are now pro-choice). Does this sound like any party you know? So much for increased funding to the Canadian Space Agency.

GCNRevenger · 2006-01-26 19:14:03

As far as the politics: free market economics works, and for sluggish economies even a little tax reliefe can yeild big dividends for society as a whole. Excessive welfare almost never helps. And having laws based on the will of the people about abortion and gay marriage are preferable to ones handed down from on high by judicial edict or as unwanted relics from past governments out of favor. Anyway, thats not the topic of conversation...

By your line of reasoning Robert, lots of other VSE componets could be outsourced to Russia, France/Germany, and whatnot, and then it won't really be an "American" space program that America is spending all that tens of billions of American money on. This is not like a business, this is large amounts of US government money that is funding a US government project, simply because another country can supply parts cheaper is not the only factor here.

But really, if NASA can't make this work, what do you think their chances of making VSE work are? Without VSE, NASA has no future beyond ten years from now. This is a test for NASA, that they will do one of two things:

1: Make it work, and modify the SSME engine and make it air-start and/or make it cheap enough to throw away ~20 of them a year sometime or another.

2: Make the hard choice and tell Congress that this is the way its going to be, that SSME is out of the picture and the money associated is essential for VSE, and if they want to retain the SSME shop then they have to pony up for some make-work project.

If NASA can't accomplish either the technical or the political solution to this signifigant but fairly small technical (SSME already works, its a modification of exsisting hardware) or political (SSME employs ~500-1000 workers, 3-6% of the STS Army) aspect of VSE, then chances are that NASA isn't ever going to make VSE work.

Given the desire for Congressmen to retain as many American engineers as possible, and Russian control over the American space program by supplying componets we can't, buying Russian engines is not going to happen. Giving Russia control of our $300Bn (for the next 19 years until we're ready to think about Mars) space program is out of the question.

If NASA wanted to buy the RD-0120 design and make copies, that would still take alot of time and money and the engines still be pretty expensive since they're made with US labor. If they are made with current SSME staff, they won't be much cheaper per unit at all. Probobly only a little less trouble and expense then going through with SSME modifications, especially since they'll need to be validated just like "SSME-B." The political cost will be quite high however... if Russia will even let us have the design. If we're dumping SSME for locally made RD-0120 anyway and manage to cull the SSME shop staff to make them cheap enough, why not just go for J-2 on CEV and RS-68 on HLLV? RD-0120 isn't man-rated by NASA's standards either I bet.

Edit: Of the J-2S engine, a blurb I didn't see at the bottom before on the Astronautix page: "It was estimated by ATK Thiokol in 2005 that restarting the J-2S program, including engine fabrication, design and reliability verification, certification, and production, would require four years."

Just in time for CEV in 2012

RobertDyck · 2006-01-26 20:28:00

I created a new thread under "Free Chat" called "Canadian Politics". I'll leave political talk there.

NASA has had the problem that the extreme number of centers costs money. It's time to trim down. After hurricane Rita I suggested converting a building at KSC to manufacture ETs. Just move equipment over. Michoud is sized for 50 tanks per year, it isn't needed for the current launch rate. If stopping production of SSME results in closing Stenis, then that's another major cost reduction.

Yes, theoretically you could re-design SSME to be simplifiied. It would require going with the new exhaust cone, but also adopting Russia's idea of a single pre-burner and turbine. I've read that NASA doesn't have the math formulae to optimize turbopumps run on a single drive shaft. Fine, Russia is selling everything not nailed down; pay them to show NASA the formulae. But the big question is whether you can get Pratt & Whitney to keep costs down.

But I keep saying, why re-invent the wheel? Why try to do everything yourself? If you can't get it done yourself and partners are willing to participate, why not? Don't blame Russia for delays of ISS. How long has the Shuttle been grounded? The US is hardly in a position to point fingers.

Going to dual J-2S will probably result in The Stick being cancelled. If that's your intention, if you want The Stick replaced by something else, fine go for it. By the way, "J-2S" is an upgrade from J-2.

GCNRevenger · 2006-01-26 20:55:18

As I said in the previous post, your first paragraph is basically what I was meaning by the "political trouble" that NASA will have to learn to overcome. The question that P&W can build RD-0120 cheaply if Congress is ready to pitch a fit over Stennis is already answer: probobly not for much less then SSME-B, and then there is the political cost of getting the Russian design.

NASA needs to do as much work in the US as it can because its an American enterprise, you aren't listening Robert: NASA's political capital is just as scarce and vital as its financial, and for the quintecential non-military patriotic endeavour to throw its hands up in the air and "beg the Russkies for help" is just not happening. The political cost would be like if each RD-0120 cost $100M or something, perhaps possible but just not affordable. Perhaps its a bit harder to see if you are from your side of the border.

Why shouldn't we blame Russia for their lies and back stabbing dealing with the ISS? Don't you dare equate the Shuttle woes with that, the problems with Shuttle are genuine technical problems, and are not manufactured to wring money out of our partners. And do you think we should charge Russia some $300M-500M+ for Cosmonaut lift if Soyuz was broken and Shuttle were flying? Or even ~$200M for two or three seats on CEV?

But the crookedness of the lying and backstabbing Russia space agency is a secondary concern to the Russian government using our space program as a political weapon against us, which makes buying RD-0120 an extreme political cost. Just look at the Ukraine gas debacle, and since the US space program is comparitively small interest, think how much more willing Russia would be to use it against us? It would only cost them like ~$50M-100M a year ($2-3M per engine @ 20/yr) to completly stop our ~$17,000,000,000.00 space program cold.

I don't think that switching to J-2 will lead to the cancelation of The Stick. Why would it? We know the engine works pretty well, and its been used as recently as the X-33 project (eight of them make one linear aerospike array). Sure the "S-model" would be a little more trouble, but I don't think too much. The five-segment SRB has already been test fired, and should not be as hard to use as it would be to redo half the SSME workings.

Edit: And don't forget, NASA is going to use the J-2 for the big HLLV upper stage too since it can easily restart but SSME can't, and is already going to use the five-segment SRB instead of the four-segment on it too.

Edit again: A choice bit from the Astronautix site about the J-2S again: "The J-2S program consisted of six flight configuration engines tested at both sea level and vacuum conditions in 273 tests for a total operational experience of 30,858 seconds. At the completion of the program the engine was fully developed and ready to go into certification for flight operations."

Thats nine days of firing... and thats the S-model, not the old "vanilla" J-2. I would really prefer NASA go the J-2S & RS-68 route rather then SSME, particularly if it looks like SSME on CEV will take longer ther J-2S+new SRB.

Edit Edit Edit: I think I want to offically vote against using the SSME for anything VSE, the J-2S and RS-68 are too attractive. Didn't you say something about not reinventing the wheel?

John Creighton · 2006-01-26 21:43:04

If we to get past the not invented here Russia could contribute an engine in exchange for a seat on a moon mission. The problem is there is little trust between the untied states and Russia. Russia would not want to contribute the engine upfront and the United states would want the engine as soon as possible. Another possibility perhaps might be some kind of joint project to man rate on of those Russians engines. That way the united states could pay for Americans to do research and not pay for Russians. The Americans might find learning another engine technology in depth beneficial.

GCNRevenger · 2006-01-26 21:54:04

We're not going to get past the "NIH" problem, because:

-It will still be made in Russia, which would still have veto power over our space program as a weapon.

-It will still be a Russian engine, even if its built here, with the associated image & political damage to NASA.

-NASA needs the engine fast, Russia may not even be able to build them soon, much less be validated in time.

-If Congress permits NASA to abandon SSME, then NASA should just use J-2S and RS-68; forget RD-0120.

The J-2S engine coupled with the bigger five segment booster is a viable alternative to SSME for the CEV launcher, especially since NASA was planning on developing both engines later anyway. The RS-68, with its superior thrust and comperable Isp at sea level, will not cause a signifigant reduction in payload of the big HLLV either, and is available off-she-shelf, no modification required.

Edit: Looking more into how complicated the SSME is, I think abandoning it entirely is looking like a better deal by the minute.

SpaceNut · 2006-01-26 22:29:53

Yes being not able to produce the engine that is a Russian military product is a problem but serveral engines have been though the process to make them more american in nature. Lockheed and Pratt & whitney both have had some success an at least one not as good as america existing products from what I can find.

As for out sourcing of the building of parts for use in Nasa's rockets from this point forward, I agree that this is a private industry process but if no company ever does go this route than the best we will ever do will be with the dreamers of the alternate x investors.

GCNRevenger · 2006-01-26 22:37:55

I don't think you could say the RD-0120 is a Russian military part, I was using the term "weapon" in a purely metaphorical sense, that Russia could use the supply of these engines to apply political pressure against the US for relativly little cost to them.

Yes the Atlas-V uses Russian-made rocket engines, but the USAF stipulated that the US have the capacity to build their own copies of the engine if the Russian supply were cut off. This has incurred signifigant expense to Lockheed, and to a signifigant degree offset the cost bennefits.

NASA is not Lockheed, and since there is little chance of the USAF being gutted due to public indifference and other budget pressures, NASA has less political capital to spend. This lack of credibility, expendability, and NASA being a "great American endeavour" increasing the political cost, I don't think NASA can afford to beg Russia for their engine or its design.

Edit: If Russia pulled the plug on Atlas-V engine, the USAF would always have the Delta-IV to fall back on. NASA would be out of luck.

SpaceNut · 2006-01-26 22:53:17

Which sort of makes Boeings RS-68 or some form of it the best COT's product to make use of. Now that we think that we want to go with this engine for the upper stage but being that it is a little under power and that it would need the 5 segment srb. Would it not be a better design to use 2 slightly smaller diameter 4 segment srb's mounted side by side to get the added velocity before the upper stage would be fired.

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