Author Topic: DIRECT v2.0 - Thread 3  (Read 447766 times)

Offline MP99

Re: DIRECT v2.0 - Thread 3
« Reply #2320 on: 03/28/2009 09:27 AM »
Do you have LOC\LOM number for new J-246?

Sorry forgot to mention...

LOM/LOC numbers are pretty artificial. If I was sitting on top of a launch vehicle I would want:-

1) Engines that demonstrably fail very infrequently
2) ...and fail benignly when they do fail.
3) A vehicle that has margin to cope with a failed engine
4) ...and pushes as few new technological boundaries as possible.

Regardless of numbers, that's the vehicle that's least likely to kill a crew on the first dozen flights (IMO).



Quote
Is the Direct team not leading themselves open if they switch to the J-246, like NASA that they keep on refining their plans?  All good, PM know that Planning is good, and there will be refinement as you know more but at some point you have to implement.  Is the Direct team basically saying that the Constellation team really needs to revaluate the whole program due to the wrong assumptions that they made in the ESAS study.  That would take a strong leader at NASA to say, we may have made a mistake in the ESAS study.

As I understand, DIRECT have always kept their vehicle as similar as possible to Ares-V. When Ares chose RS-68, DIRECT were "stuck with it" (and J2-X), too. (Not that it doesn't perform fine).

DIRECT's decision to look again at SSME was driven by news that ablative RS-68 probably won't work with Ares, and by implication may be marginal at best with Jupiter. Apparently Ares baseline has switched to SSME, but this has not been announced externally.

This came out of NASA research that is way beyond DIRECT's ability to fund. It validates DIRECT's policy of keeping their designs "as close as possible", since that research is directly applicable. Most issues that Ares-V suffers will be present to some degree with Jupiter, but usually scaled back to around the levels with which the Shuttle design & components already cope. And that's the whole rationale behind "Shuttle Derived Launch Vehicle" - reuse of mature technology.

cheers, Martin

Offline MP99

Re: DIRECT v2.0 - Thread 3
« Reply #2321 on: 03/28/2009 09:54 AM »
Would SSME Jupiter be v3.0?


Probably not even V2.1 - more likely v2.0, with Jupiter LV40.


Don't forget that v2.0 refers to DIRECT (the overall mission plan), not the Jupiter launch vehicle (which has the LVnn version numbers).

V1.0 of DIRECT was a sort of 1.5 architecture (J-232 + J-120, I think), and comprehensively dismissed by NASA.

V2.0 of DIRECT is a 2.0 architecture (EDS CaLV, Altair + Orion CLV). To a large extent, the details of the Jupiter launcher are irrelevant to the architecture, so I'm not convinced that a mere engine swapout justifies even a point difference. It slightly adjusts the IMLEO & EDS burnout figures, and that's about it.

cheers, Martin

PS I recently suggested changing DIRECT to Crasher + Altair (CaLV), Orion + EDS (CLV). That's the sort of thing that would justify a revision to the DIRECT version number (2.1, maybe).

Offline marsavian

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Re: DIRECT v2.0 - Thread 3
« Reply #2322 on: 03/28/2009 11:24 AM »
I disagree, changing to SSME (and RL10/RL60)) would be a far more radical change in design than going from regen RS-68 Direct V1 to RS-68B Direct V2. It clearly is a version 3 and more than that if you get rid of the J2-X too you are following the DIRECT guiding principle completely, no new engine development ! It also gives NASA the PR cover to use the concept, add the J2-X and still allow them to say it is not DIRECT ;).
« Last Edit: 03/28/2009 12:23 PM by marsavian »

Offline kraisee

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Re: DIRECT v2.0 - Thread 3
« Reply #2323 on: 03/28/2009 12:20 PM »
I am pleased to announce that by almost unanimous vote of both our engineering team and our public team together, we have decided to break with the Constellation Program's baseline choices and DIRECT is officially moving to a position of baselining the Space Shuttle Main Engine as our primary Main Propulsion System for the Jupiter launchers.

The provisional plan for Jupiter is to utilize older flown SSME's during the testing phase of the program and some early IOC flights, to build some new SSME's and then at some yet-to-be-determined point in the future to fund a new development program intended to reduce the production costs of the SSME.

The cost for the SSME, per unit, is higher than the RS-68, although it completely avoids all up-front development costs and schedule impacts, so overall it is a much faster and cheaper alternative in the short- to -mid-terms.   In the quantities which DIRECT plans to build the SSME's, their production costs significantly drop compared to current low-volume production runs used previously for the Shuttle Program.

When re-developed into a cheap alternative in the future, the cost profile is extremely competitive with the RS-68 Regen, yet offers significantly greater performance in the Jupiter configuration.

The RS-68 option does not completely 'disappear', but becomes the secondary option instead of the primary.


Switching to the SSME for our baseline does not imply any change at this time regarding using the J-2X verses the RL-10 or even an RL-60 option.   At this moment the J-2X remains our baseline, although discussions are on-going.

Ross.
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Offline robertross

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Re: DIRECT v2.0 - Thread 3
« Reply #2324 on: 03/28/2009 12:32 PM »
I am pleased to announce that by almost unanimous vote of both our engineering team and our public team together, we have decided to break with the Constellation Program's baseline choices and DIRECT is officially moving to a position of baselining the Space Shuttle Main Engine as our primary Main Propulsion System for the Jupiter launchers.

The provisional plan for Jupiter is to utilize older flown SSME's during the testing phase of the program and some early IOC flights, to build some new SSME's and then at some yet-to-be-determined point in the future to fund a new development program intended to reduce the production costs of the SSME.

The cost for the SSME, per unit, is higher than the RS-68, although it completely avoids all up-front development costs and schedule impacts, so overall it is a much faster and cheaper alternative in the short- to -mid-terms.   In the quantities which DIRECT plans to build the SSME's, their production costs significantly drop compared to current low-volume production runs used previously for the Shuttle Program.

When re-developed into a cheap alternative in the future, the cost profile is extremely competitive with the RS-68 Regen, yet offers significantly greater performance in the Jupiter configuration.

The RS-68 option does not completely 'disappear', but becomes the secondary option instead of the primary.


Switching to the SSME for our baseline does not imply any change at this time regarding using the J-2X verses the RL-10 or even an RL-60 option.   At this moment the J-2X remains our baseline, although discussions are on-going.

Ross.

Great news Ross. I'm really pleased your team made this decision to go with SSME. Again, another case when it JUST MAKES SENSE. I say this, due to the pressures of the timeline and the fairly accurate costing information you and others have provided us. It's an engine we have, no mods needed, and we can fly very quickly.

I'm still at odds over the J-2X, mainly due to the unknown issue. Maybe it's funding, maybe it's lack of expected performance, we don't know. That's a bit worrying. At least having RL-10 in the back pocket helps, but I would throw some many that way to help man-rate it anyways, just as a fall-back.

You guys continue to impress with great decision making. You need a new job: at NASA.  :)
RIP Justin Wilson

Offline kraisee

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Re: DIRECT v2.0 - Thread 3
« Reply #2325 on: 03/28/2009 12:51 PM »
Robert,
RL-10 already requires human-rating anyway, for the Altair LSAM.

In fact, the original RL-10's were designed to be human-flown back in the days of the 6-engine'd Saturn-1 S-IV stages.   But they were never flown with a crew -- so the heritage is already there, to a degree.

Ross.
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Online mmeijeri

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Re: DIRECT v2.0 - Thread 3
« Reply #2326 on: 03/28/2009 02:05 PM »
Sad to say, the "fall back" to RS-68 would be a little disappointing at this point!

Only if you want a new upper stage, not if you go with L1 rendez-vous. No new engines, no new upper stage, cheaper and fewer engines. But to be honest it's not so much the cost I care about (since you guys are paying), it is the impact on depots and international / commercial manned spaceflight.
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Offline PaulL

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Re: DIRECT v2.0 - Thread 3
« Reply #2327 on: 03/28/2009 03:04 PM »

Is there -any- advantage the J-2X would have in the Direct Architecture?


I can see three advantages of using the J-2X over the RL-10 engine for the Jupiter EDS:

1-Political advantage: It would be harder for NASA to switch to the Direct architecture if they have to say to the politicians that the all money spent on the J-2X engine development is now a total waste. 

2-Simpler EDS: One engine requires less piping/valves and interfaces than 6. Therefore, there is less chance of launching delays/propellant leaks.

3-Bigger "pure" LEO payload because of lower gravity losses.  This is not an issue for moon missions, which can be done with two J-246, but this would have an impact on future Mars missions. For example, a typical Mars mission requiring 5 J-241 would probably require 6 J-246 for the same overall payload.

PaulL


Online mmeijeri

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Re: DIRECT v2.0 - Thread 3
« Reply #2328 on: 03/28/2009 03:12 PM »
I can see three advantages of using the J-2X over the RL-10 engine for the Jupiter EDS:

Is there any way the EELV's could benefit from using a J-2X in the future?
May Decatur do to SLS what Decatur did to the USS Philadelphia.

Offline yinzer

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Re: DIRECT v2.0 - Thread 3
« Reply #2329 on: 03/28/2009 03:31 PM »
The J-2X is a very large engine. The nozzle is roughly the same size as the nozzle on the F-1. It's much bigger than would be needed on an EELV, unless you wanted to triple their payload to LEO or something.
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Offline TrueBlueWitt

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Re: DIRECT v2.0 - Thread 3
« Reply #2330 on: 03/28/2009 04:16 PM »
The J-2X is a very large engine. The nozzle is roughly the same size as the nozzle on the F-1. It's much bigger than would be needed on an EELV, unless you wanted to triple their payload to LEO or something.

J-2X Powered Upper stage on a Delta IV heavy? 

How much Could that lift to LEO?  TLI?
Cargo only perhaps.. max G's would have to be high at 100% thrust.

Could you even get it off the pad with enough fuel in the US to do you any good?

Offline Ben the Space Brit

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Re: DIRECT v2.0 - Thread 3
« Reply #2331 on: 03/28/2009 04:51 PM »
J-2X Powered Upper stage on a Delta IV heavy? 

How much Could that lift to LEO?  TLI?
Cargo only perhaps.. max G's would have to be high at 100% thrust.

Could you even get it off the pad with enough fuel in the US to do you any good?

You might want to talk to EdKyle about that.  He proposed a version of  the D-IVH with the J-2X-powered AIUS in place of the normal upper stage.  The numbers, when crunched, indicated that the vehicle would need to launch with only partly-filled tanks because of weight issues, but that the overall design improved payload and trajectory.  I think that the performance was good enough that the posters thought that the US could act as an EDS for lunar flyby missions.
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Offline yinzer

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Re: DIRECT v2.0 - Thread 3
« Reply #2332 on: 03/28/2009 05:02 PM »
The J-2X is a very large engine. The nozzle is roughly the same size as the nozzle on the F-1. It's much bigger than would be needed on an EELV, unless you wanted to triple their payload to LEO or something.

J-2X Powered Upper stage on a Delta IV heavy? 

How much Could that lift to LEO?  TLI?
Cargo only perhaps.. max G's would have to be high at 100% thrust.

Could you even get it off the pad with enough fuel in the US to do you any good?

No.  The J-2X is only going to be useful if you are trying to lift very heavy payloads, fifty tons or more.  The EELV lower stages are not big enough for such payloads.  The only reason J-2X could be used on Ares I was because the SRB was so undersized.

It's also worth noting that going to the J-2X was instrumental in the imminent downfall of the Ares I.  Putting paper engines squarely in the critical path of your new launch vehicle when you don't have to is not wise.
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Offline HIP2BSQRE

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Re: DIRECT v2.0 - Thread 3
« Reply #2333 on: 03/28/2009 05:45 PM »
The J-2X is a very large engine. The nozzle is roughly the same size as the nozzle on the F-1. It's much bigger than would be needed on an EELV, unless you wanted to triple their payload to LEO or something.

J-2X Powered Upper stage on a Delta IV heavy? 

How much Could that lift to LEO?  TLI?
Cargo only perhaps.. max G's would have to be high at 100% thrust.

Could you even get it off the pad with enough fuel in the US to do you any good?

No.  The J-2X is only going to be useful if you are trying to lift very heavy payloads, fifty tons or more.  The EELV lower stages are not big enough for such payloads.  The only reason J-2X could be used on Ares I was because the SRB was so undersized.

It's also worth noting that going to the J-2X was instrumental in the imminent downfall of the Ares I.  Putting paper engines squarely in the critical path of your new launch vehicle when you don't have to is not wise.

I agree totally with you.  Why invent the wheel/j-2X if you don't have to?   

So you lose your upfront development costs?  And?  Those costs are sunk costs, you cannot get them back.  If I can build a new car with a good 'old' relieable engine, should i go out and spend another billion dollars to do the same thing, since I have already spent $200 million?  Nope. :-)  The new engine, in this case the J-2 has to build a better saftey/business/case on itself.  As Ross, pointed out, if the J-2 proves marinally more safe--is it really worth doing?  Most people don't do development just to do development, they do it because it fits a need.  If the requirements change and I can purchase a cheap commerical offshelf product, why go and build it?
« Last Edit: 03/28/2009 05:47 PM by HIP2BSQRE »

Offline MP99

Re: DIRECT v2.0 - Thread 3
« Reply #2334 on: 03/28/2009 07:45 PM »
Sad to say, the "fall back" to RS-68 would be a little disappointing at this point!

Only if you want a new upper stage, not if you go with L1 rendez-vous. No new engines, no new upper stage, cheaper and fewer engines. But to be honest it's not so much the cost I care about (since you guys are paying), it is the impact on depots and international / commercial manned spaceflight.


???

SSME J-130 can lift a lot more mass to orbit than RS-68 J-120 without developing an upper stage at all.

Add in a separate 55m/s circ burn post-ascent, and you're looking at 2:1 in favour of SSME (93mT+).

If you want an architecture without an upper stage, why would you prefer an RS-68-based core?

cheers, Martin

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Re: DIRECT v2.0 - Thread 3
« Reply #2335 on: 03/28/2009 07:54 PM »
???

SSME J-130 can lift a lot more mass to orbit than RS-68 J-120 without developing an upper stage at all.

Add in a separate 55m/s circ burn post-ascent, and you're looking at 2:1 in favour of SSME (93mT+).

I thought the numbers were 45 mT for an RS-68 J-120, 50 mT for an RS-68A J-120 and 60 mT for a J-130. And if you consider the cost per kg, the difference is small, with the RS-68A coming out best. In my spreadsheet anyway...

Quote
If you want an architecture without an upper stage, why would you prefer an RS-68-based core?

Strategic reason: with RS-68's and RL-10's they're gonna need propellant depots even with a new upper stage, so there would not be much reason to develop one. :) They'd also have more money for depots.

Other than that, commonality with Delta. Less of an issue if Delta IV is man-rated anyway.
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Offline MATTBLAK

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Re: DIRECT v2.0 - Thread 3
« Reply #2336 on: 03/28/2009 08:21 PM »
The RL-60 would have been the engine to go for -- at least with no Ares 1 around to need the J-2X's high thrust. And it would still be quicker to field than J-2X.
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Offline robertross

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Re: DIRECT v2.0 - Thread 3
« Reply #2337 on: 03/28/2009 10:51 PM »
We were always told Orion won't be ready before Ares-I.

Robert, I think you have been mis-informed.

Orion could always have been made ready before Ares-I.   CxP have restricted its budget so that it is designed to finish at the same time as it's launcher will, but that really is an artificial limitation.

The long-pole for the pair has always been the development schedule of the J-2X engine, followed by the schedule of the 5-segment booster.

Ross.

Well I'll be...egg on my face! Thanks Ross, and on the RL-10 man-rating clarification.
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Re: DIRECT v2.0 - Thread 3
« Reply #2338 on: 03/29/2009 12:32 AM »
Robert,
RL-10 already requires human-rating anyway, for the Altair LSAM.

Okay, I don't understand anymore where the CECE fits in.  Please help me out here.

Offline Patchouli

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Re: DIRECT v2.0 - Thread 3
« Reply #2339 on: 03/29/2009 02:07 AM »
CECE is derived from the RL-10 one probably could even call it an RL-10 variant but I think they completely reworked the injector design and turbo pump.

http://www.pratt-whitney.com/vgn-ext-templating/v/index.jsp?vgnextrefresh=1&vgnextoid=91380e78738ee010VgnVCM100000c45a529fRCRD

Altair uses four of them I think an EDS might use 6 to 8.

Interesting note the engine has potential for reusability with 50 restarts and 10,000 seconds of operation.

Also to my surprise a methane fuel option though I'd hate to see how many an ERV would need to get off Mars then again it can't be any worse then Falcon 9.

Too bad it's only 25,000lbs thrust otherwise an F9 with a CECE upper stage or even a small SSTO RLV using them could be really interesting.
« Last Edit: 03/29/2009 02:16 AM by Patchouli »

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