Author Topic: Why a RS-68B based SHLV is more likely to be picked than a SSME based SHLV  (Read 103368 times)

Offline Namechange User

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Your tag line at the bottom is "if it ain't broke, don't fix it".  Why front load a new HLV with more development, where major problems can always arise, if not necessary?  We have the tooling for an 8.4 meter core now.  We have SSME's where it has been studied for years on how to make expendable versions.  We have all the infrastructure in place to accomodate that configurationm, etc. 

So use 5 segment boosters someday if necessary, fine and that gives you a little more performance.  However, those are not ready and we have 4 segments today.  The simple fact is there is no reason to throw the baby out with the bath water and fund MSFC for a decade to maybe eventually field a new mega booster that will not be cost effective when complete just because MSFC employees *think* we need it.  This is about power at their center and their center alone.  Don't fool yourself that it is anything else. 

I agree with that, but politics being what they are, it may be necessary to throw MSFC a "bone."

I think we should go right to the 8.4m SSME design just for the reasons you state. I don't even think it would take the 8-9 years for the development if we went that way.

Mr. Obama however, being a man of consensus building, might be willing to sacrifice that design.

The president is not a rocket scientist and therefore will not be doing any design from the oval office. 

MSFC will get a bone by being the lead agency on the launch vehicle, as they always have been historically.  In other words, the project office will be based there as it always has been.  What needs to be stopped from happening by the Program office and the HQ level, is caving and allowing that project office to cram their mega booster down everyone's throat at the expense of cost and schedule to only add technical risk. 
Enjoying viewing the forum a little better now by filtering certain users.

Offline raketen

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A few reasons:

1. Whoever ever took a look into the Augustine report (just review page 87...) should know that a 5 RS-68B Ares V Lite based SHLV received a ringing endorsement by the report over any SSME-based SDLV.

2. NASA likes the concept. They want as big an HLV (with growth option) as they can get. A 5 RS-68B, 5-segment SRB Ares V Lite provides 145mt to LEO AND still offers 20% in growth at a later stage.

3. The RS-68B development effort just has a bigger lobby (at MSFC, at Rocketdyne, at NASA headquarters, in other industry lobbyists) behind it vs. an RS-25e development effort.

This is my opinion. If Ares I is canceled and an SHLV only is developed, it will be a RS-68 based, 5-segment, J-2x rocket.

IMHO, it is 95% certainty that the simplest Shuttle-Derived system will be developed initially - SSME, 4-segment SRB, ET core diameter.  It will be either side-mount or in-line.  But politics trumps engineering in the end.

Offline dad2059

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The president is not a rocket scientist and therefore will not be doing any design from the oval office.
 
True. But that's why they hire shmuck advisors.  ;)

Quote
MSFC will get a bone by being the lead agency on the launch vehicle, as they always have been historically.  In other words, the project office will be based there as it always has been.  What needs to be stopped from happening by the Program office and the HQ level, is caving and allowing that project office to cram their mega booster down everyone's throat at the expense of cost and schedule to only add technical risk. 

Agreed.
NASA needs some good ol' fashioned 'singularity tech'

Offline clongton

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ares-mojo;
RS-68 Regen is a $1 billion dollar development program. In these economic times it is nothing short of an act of blind hope to believe that we will spend that kind of money to replace an engine that we already have that can already do the job required. The civilian space program does not and will not have that kind of money to spend on unnecessary engine development and the US Air Force will not share development costs for it because they simply have no need of it.

Your earlier statement dismissing the better efficiency of the SSME over the higher thrust of the RS-68 just demonstrates that you do not understand such fundamental things as the rocket equation. The object is not to lift the most tonnage off the pad, but to send the most tonnage on its way to the target. While the RS-68 has higher thrust to get things off the pad, it also requires much more propellant. That means that a major percentage of what it's lifting off the pad is propellant for the engine, not useful payload. That simple fact seems to have escaped you.

Your earlier statement:
Quote
That's like saying a 100hp gasoline based engine has less performance than an 80hp diesel based engine, just because the diesel engine is more fuel efficient.

further demonstrates your need to more carefully consider your statements because it depends on whether you are describing the performance of a muscle car or a launch vehicle, which looks at "performance" differently. In your example, the muscle car can move more mass off the start line than the diesel because it's more powerful. But because of its fuel consumption, what does that matter if it can't get the required mass to the finish line before it runs out of gas? That's where the efficiency of the diesel comes in because it wont run out of fuel until after it actually delivers that mass across the finish line. The object is to actually finish the job, not start it with the biggest bang. That's the difference.

There is a thread on this site which actually discusses all this stuff, in detail, with the math to actually explain it. May I suggest that you check it out? It would be well worth your time. It's "Basic Rocket Science Q&A", and is found here: http://forum.nasaspaceflight.com/index.php?topic=13543.new;topicseen#new
« Last Edit: 12/29/2009 02:45 pm by clongton »
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Offline wdobner

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The RS-68B would not be an option due to base heating. You would have to develop a regen version.

The RS-68B IS the Regen version of the RS-68 engine.

This does not seem to be consistent with what I can find.  The RS-68 wiki article, which has clearly been edited by an Ares V advocate recently, specifically states the RS-68B will incorporate the RS-68A's performance modifications with an improved ablative nozzle to hold up under the longer burn time.  The NASA documents the article references also point to the direct lineage of the RS-68B to the engine used in the Delta IV, and IMHO that is indicative of an ablative RS-68 variant. 

Do you have a specific source which indicates the RS-68B uses a regeneratively cooled nozzle as opposed to a redesigned ablative nozzle?

I think you ignore the potential to grow a SSME powered DSDLV into the RS-68 powered HLV you appear to have a Freudian facination for at a later point when we're not quite so pressed for time and money.  An SSME based booster at least opens up the prospect of a LEO HLV like the J130/J140SH family sometime in the 2014 timeframe.  Anything using a regenerative RS-68 is unlikely to fly before 2018 at the earliest. 

The infrastructure changes for the Ares V appear to have not yet been included in NASA's congressional outlay.  Thus  I would be willing to bet that in the face of billions of dollars in changes to the KSC facilities the few million dollars spent on non-EELV related RS-68 development will look like small potatoes and ripe for axing.  Shelby isn't going to argue to save a specific engine, especially when it will not be developed in his state.  Thus I would say the move to a SSME based booster is probably one of the safer swaps that can be made from a political and economic standpoint.

Offline dad2059

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ares-mojo;
RS-68 Regen is a $1 billion dollar development program. In these economic times it is nothing short of an act of blind hope to believe that we will spend that kind of money to replace an engine that we already have that can already do the job required. The civilian space program does not and will not have that kind of money to spend on unnecessary engine development and the US Air Force will not share development costs for it because they simply have no need of it.

Ouch! A billion smackers is still a lot of cabbage even in this day and age.

Side-mount carrier w/4 section solids and SSMEs probably would be the quickest and cheapest HLV if the politicos could be bribed to go that route, especially if it was stressed that it would be used for cargo only.

Even in-line shouldn't be much more costly, about Jupiter 130 size, especially if the 8.4m size is advocated.

That just could be the "simpler" Obama and Bolden want.

« Last Edit: 12/29/2009 03:26 pm by dad2059 »
NASA needs some good ol' fashioned 'singularity tech'

Offline MP99

Add to it that the Ares V Lite can only lift 145mT vs the Ares V Classic which could do 155mT, to start. 


If NASA builds an SSME vehicle today, it will use Shuttle-style (steel-cased PBAN) SRB's, rather than the filament-wound HTPB versions from AVC. Performance will be somewhat lower.

cheers, Martin

Offline Patchouli

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I beg to differ the SSME just has too many performance advantages over an RS-68 based design.
As far as cost a disposable SSME would not be much more expensive then the RS-68B.
It really would depends on flight rates on which will be cheaper $1B could buy a lot of SSMEs.
But the biggest advantage as MP99 put it we have the SSME today which means the vehicle can fly soon.
It might even be able to fly concurrently with STS eliminating any gap.
Plus it keeps the experience of the SSME alive and leaves more future RLV options open.
« Last Edit: 12/29/2009 04:00 pm by Patchouli »

Offline kraisee

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The 10m Core would cost over $1bn in higher costs at MAF compared to the 8.4m Cre and a further $3bn at KSC to modify the facilities there too (VAB, MLP, Propellant Storage facilities etc).

Because of those extra costs, the Bolden HLLV Study found that option was unaffordable.   That option has already been removed from the remaining considered options list.   To use NASA-Speak:   10m Tanking is no longer in the Active Trade Space.

If you aren't going with 10m tanking, SSME is the far, far better option -- especially given the $1bn costs involved in making the RS-68 engines compatible (Regen nozzle) with the Base Heating environment on these much larger vehicles.

Keep dreaming if you choose to.   But reality is moving on without you.

Ross.
« Last Edit: 12/29/2009 04:06 pm by kraisee »
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Offline dad2059

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The 10m Core would cost over $1bn in higher costs at MAF compared to the 8.4m Cre and a further $3bn at KSC to modify the facilities there too (VAB, MLP, Propellant Storage facilities etc).

Because of those extra costs, the Bolden HLLV Study found that option was unaffordable.   That option has already been removed from the remaining considered options list.   To use NASA-Speak:   10m Tanking is no longer in the Active Trade Space.

If you aren't going with 10m tanking, SSME is the far, far better option -- especially given the $1bn costs involved in making the RS-68 engines compatible (Regen nozzle) with the Base Heating environment on these much larger vehicles.

Keep dreaming if you choose to.   But reality is moving on without you.

Ross.

So, if MSFC gets a bone, it's gonna have an 8.4m core, eh?  ;D

That means Ares V is dead, right?
NASA needs some good ol' fashioned 'singularity tech'

Offline FinalFrontier

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The 10m Core would cost over $1bn in higher costs at MAF compared to the 8.4m Cre and a further $3bn at KSC to modify the facilities there too (VAB, MLP, Propellant Storage facilities etc).

Because of those extra costs, the Bolden HLLV Study found that option was unaffordable.   That option has already been removed from the remaining considered options list.   To use NASA-Speak:   10m Tanking is no longer in the Active Trade Space.

If you aren't going with 10m tanking, SSME is the far, far better option -- especially given the $1bn costs involved in making the RS-68 engines compatible (Regen nozzle) with the Base Heating environment on these much larger vehicles.

Keep dreaming if you choose to.   But reality is moving on without you.

Ross.
That is EXACTLY what I am saying. :D :D Thank you ross.
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Offline lem3spider9

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Interesting discussion.  As a non-technical guy, I'd like to see ares-mojo respond to OV-106's comment about being "Huntsville-centric" and some of OV's other comments.  He seems to have hit the nail on the head.
« Last Edit: 12/29/2009 04:30 pm by lem3spider9 »

Offline Analyst

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Folks seem to have the (big) rocket in mind only, not the mission (spacecraft, payloads) it just supports for a few minutes. "What I can see is important, everything else does not matter much."

Analyst

Offline kraisee

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100% Agreed Analyst.

The Rocket is only the 'enabler' for the important bit -- the spacecraft.   Even that is only the 'enabler' for the actual mission.

Every dollar you don't spend on the rocket is another dollar which can be spent on the mission -- and that's the bit which gets you results.

Ross.
« Last Edit: 12/29/2009 04:49 pm by kraisee »
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Offline marsavian

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The 10m Core would cost over $1bn in higher costs at MAF compared to the 8.4m Cre and a further $3bn at KSC to modify the facilities there too (VAB, MLP, Propellant Storage facilities etc).

Because of those extra costs, the Bolden HLLV Study found that option was unaffordable.   That option has already been removed from the remaining considered options list.   To use NASA-Speak:   10m Tanking is no longer in the Active Trade Space.

If you aren't going with 10m tanking, SSME is the far, far better option -- especially given the $1bn costs involved in making the RS-68 engines compatible (Regen nozzle) with the Base Heating environment on these much larger vehicles.

Keep dreaming if you choose to.   But reality is moving on without you.

Ross.

So, if MSFC gets a bone, it's gonna have an 8.4m core, eh?  ;D

That means Ares V is dead, right?

No because the original ESAS Ares V had 5 SSMEs in a 8.4m core. It is the leading candidate now but with PBAN SRBs and one J2-X. It is the most sensible heavy choice as you can have it relatively quickly and cheaply compared to any expensive regen RS-68 10m Ares V. Just use two launches if you want a heavy duty mission but just one launch will give you a bit more than what a Saturn V could do and that was a pretty useful lunar launcher if I remember ;). MSFC has to get real and deal with realities like cost, schedule and budget which their political masters are very concerned about but which they have just been providing lip service to up to now as they have envisaged even bigger, later and more expensive Ares V variants over the last few years. ESAS had the heavy launcher right from the beginning, now just build it already and stop messing around with unfundable and unrealistic mega launch designs.
« Last Edit: 12/29/2009 10:42 pm by marsavian »

Offline dad2059

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Quote
No because the original ESAS Ares V had 5 SSMEs in a 8.4m core. It is the leading candidate now but with PBAN SRBs and one J2-X.

Cool. Thanks marsavian, I didn't realize that.

It seems that OV is right and MSFC has to cut down on their wishful thinking somewhat.

The political sh*t-storm isn't going to be pretty to watch though.
NASA needs some good ol' fashioned 'singularity tech'

Offline MP99

So, if MSFC gets a bone, it's gonna have an 8.4m core, eh?  ;D

That means Ares V is dead, right?

"Ares is dead, long live Ares".

  • It's still two SRB's & four or five engines
  • It better meets the "shuttle-derived" mandate
  • It's presumably gonna be called Ares
  • It was NASA's original choice from ESAS (or a slightly cheaper version)
  • It demonstrates fiscal responsibility

  • Seems like a winner all round, if the alternative really is the fully commercial option.

    cheers, Martin
    « Last Edit: 12/29/2009 05:59 pm by MP99 »

    Offline kraisee

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    There is still room for NASA to make a smaller (most importantly: "cheaper") Shuttle-Derived HLLV.

    Chances are that they would keep the name for it, although the spec would change.

    Ross.
    "The meek shall inherit the Earth -- the rest of us will go to the stars"
    -Robert A. Heinlein

    Offline clongton

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    Folks seem to have the (big) rocket in mind only, not the mission (spacecraft, payloads) it just supports for a few minutes. "What I can see is important, everything else does not matter much."

    Analyst

    Totally correct Analyst. So many people make the mistake of wanting to look at the biggest baddest coolest "rocket" and completely forget about why we launch them in the first place. A rocket is just a means to an end, NOTHING MORE. Ultimately we have a mission in mind with a specific destination. We need to focus our resources on the mission spacecraft and then provide the rocket that will get the journey started. A rocket's entire lifespan is measured in minutes, while the mission spacecraft must protect a human crew for weeks or months from a much harsher environment with total perfection. The rocket has to be good, yes, but ultimately it is nothing more than a taxicab that takes you to the airport so you can get on with the real event.
    Chuck - DIRECT co-founder
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    Offline dad2059

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    Quote
    "Ares is dead, long live Ares".

    LOL!  ;D. I get it!

    Marsavian cleared that up for me already.

    Like all things government, Ares grew into a two-headed monster from the original ESAS. Everyone just had to have their fingers in the pork-pie!

    Well, it looks like diet time if NASA still wants to have an HLLV.
    NASA needs some good ol' fashioned 'singularity tech'

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