Author Topic: All-Cryo, Stage and a Half SLS  (Read 39477 times)

Offline simonbp

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All-Cryo, Stage and a Half SLS
« on: 11/07/2010 08:58 pm »
Over on the All-Liquid SLS thread, there has been considerable discussion of an all-cryo stage-and-a-half concept. To keep things tidy, I thought I would create a separate thread for this concept.

The basic premise is to have a universal first stage based on Shuttle ET tooling, and only slightly longer, but with 6 SSMEs on the base. Midway into the flight, four of those SSMEs (and associated thrust structure) would be ejected, leaving two to finish the burn. This is same basic idea as the old Atlas rockets, but on a larger scale.

The beauty of this concept is that it allows for a very large, very efficient first stage capable of carrying a wide variety of second stages. Without any upper stage, it has similar performance to a Delta IV Heavy (useful for testing as ISS missions). With a standard Delta IV upper stage, it can almost reach the first Congressional target of 70 short tons to LEO. With a much larger stage using either a J-2X or cluster of RL-10s, and running the SSMEs at 104% thrust at liftoff, it can launch the second Congressional target of 130 short tons to LEO. All with the same first stage, all existing American engines, Shuttle-heritage construction, and no SRB infrastructure to support.

Below I've attached some basic calculations for performance. All masses are in metric tonnes (=1000 kg). Delta V for LEO is considered to be 9.4 km/s and to TLI, 12.6 km/s. This isn't terribly exact, but it gives some idea of the performance possible.

Offline kraisee

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Re: All-Cryo, Stage and a Half SLS
« Reply #1 on: 11/07/2010 09:32 pm »
As one who has 'been there and done that', trust me when I say that ATK will be your #1 threat.

Be under no illusion that they will bring the entire political clout of their whole defense contractor organization (covering 28 states) down upon you, with the sole intent of wiping this option off the face of the Earth before it ever gets any traction.   Why?   Because they don't get their share -- and they have politicians who will fight for them.

This threat makes all of your technical challenges look easy by comparison (and no, they aren't easy either).   But no matter how good your technical solutions are, you need to win the politics over (IMHO, 10 times harder than developing rockets) or your project will never get funded.

Assuming this isn't just a 'mental exercise' project (you should decide that soon, and state it publicly), you need to be fully prepared to defend -- HARD -- against such attacks.

Ross.
« Last Edit: 11/07/2010 09:36 pm by kraisee »
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Offline simonbp

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Re: All-Cryo, Stage and a Half SLS
« Reply #2 on: 11/07/2010 10:11 pm »
Well, it's not really any of us that would actually have to fight for such a concept, but rather HEFT (and similar within NASA).

That said, this system has two aces up its sleeve in the form of All-American engines (putting it over Atlas Phase II or Ajax in the minds of lawmakers), and simple cost reduction by consolidation. The latter is weapon that CBO and/or OMB could wield if they so please...
« Last Edit: 11/07/2010 10:13 pm by simonbp »

Offline Patchouli

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Re: All-Cryo, Stage and a Half SLS
« Reply #3 on: 11/07/2010 10:51 pm »
After seeing the numbers for a 50% stretched Delta IV US I think I might have a change of heart over this configuration as that meets the minimum 70T LEO and 25T TLI needed to do something interesting.

Even the standard Delta IV US version should be able to lift station module or allow Orion to do some useful science missions.

ATK will be the biggest problem outside of figuring out optimum spacing for the first stage engines.

Though maybe they can be thrown a bone and supply monolithic SRBs for the cargo variant.

Also any options for recovery of the booster SSMEs which probably would pay for it's self the first few missions?

Another configuration to check might be a standard core plus a Centaur for unmanned missions.

Though that might not outperform an EELV by too much probably but if it could allow a Cassini class mission to avoid gravitational sling shots it would be worth while.

Other tricks how about TAN with kerosene on the SSME or optimizing the nozzles for better sea level performance?




« Last Edit: 11/07/2010 10:58 pm by Patchouli »

Offline simonbp

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Re: All-Cryo, Stage and a Half SLS
« Reply #4 on: 11/08/2010 05:30 am »
With a Centaur V2, the performance is about 53 tonnes to LEO, 15 tonnes to TLI (as Centaur is smaller with a lower ISP). Delta IV upper stage is larger, and easier to stretch, so I think it's a better choice.

Recovery or TAN or other mods may be nice, but they are unnecessary and distract from the actual goal. The whole point is that there is a single "new" system (stage and a half), and thus it's plausible to get flying by 2016 in limited budget conditions.

Offline FinalFrontier

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Re: All-Cryo, Stage and a Half SLS
« Reply #5 on: 11/08/2010 05:48 am »
Fascinating concept. Would like to get into preliminary concepts for the thrust structure (since this design involves dropping the primary engines in order to turn stage one into stage two). Believe this is where the technical challenge will be.

Also, what shall we name this concept?

Ideas for a name: 1. SLS core experimental: SLSCX
2. Jupiter Core Experimental: JCX
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Re: All-Cryo, Stage and a Half SLS
« Reply #6 on: 11/08/2010 05:52 am »
I'll second this suggestion:

Also this concept is good enough to justify a name (better than "all-cryo-SLS-that-looks-like-NLS"). I'll go with Hyperion as 1) it's an awesome-sounding name, 2) goes with the whole tradition of big rockets named after Titans, 3) Hyperion was in later Greek mythology the first to understand the motion of the heavens, which is appropriate, and 4) it's an awesome-sounding name.

EDIT: Added image, also repeated from simonbp.
« Last Edit: 11/08/2010 05:55 am by sdsds »
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Offline simonbp

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Re: All-Cryo, Stage and a Half SLS
« Reply #7 on: 11/08/2010 05:57 am »
To keep it simple, let's just called it Cryo-SLS.

The thrust structure is complex, but not that complex. Relative to 5-6 years of SRB life-support, it's dirt cheap.

Offline Lars_J

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Re: All-Cryo, Stage and a Half SLS
« Reply #8 on: 11/08/2010 06:21 am »
I'm still not sold on this stage-and-a-half concept... After all, once you drop the 4 engines and supporting structure (the extra dead weight), you still have dead weight in the form of a tank that is now mostly empty.

So what do you get when you remove engines, thrust structure, and tank mass... Well if you put it together, you actually have pieces for a separate stage. :)

So why not just make fully staged LV to begin with? Is this all because you think we are lacking a suitable high-thrust 2nd stage engine for something that will stage lower?

But the J-2X is not that far off, even if its performance will fall short of initial goals. They can probably make it work. The other option is of course a vacuum-optimized SSME propelled 2nd stage. Perhaps we can gain some extra efficiency/ISP from the SSME by changing it from its "one size fits all" bell shape (from sea level to vacuum) and instead have a SSMEs optimized for their respective environments. Just a thought.

I'm not trying to derail the thread... I guess I am just engaged in some devils advocate thinking here, trying to figure out what would work best in a LV.

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Re: All-Cryo, Stage and a Half SLS
« Reply #9 on: 11/08/2010 06:59 am »
So why not just make fully staged LV to begin with?

It looks like stage and a half designs provide more ascent flexibility because the point at which the engines are dropped can be different (e.g. when flying with or without an upper stage) without changing the size of the tanks.

I would like to see a performance comparison with a triple-body, propellant cross-feed design using the same six SSME.  If the side boosters were shorter than the core, they could be dropped at the same point where the other vehicle dropped its engines....
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Offline notsorandom

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Re: All-Cryo, Stage and a Half SLS
« Reply #10 on: 11/08/2010 09:28 am »
Without the upper stage the rocket would be able to lift about the same mass as a Delta IV Heavy. However, it would be more expensive then the Delta IV. About the only advantage I can see is that it would be that it would be human rated. Am I missing something?

Offline MATTBLAK

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Re: All-Cryo, Stage and a Half SLS
« Reply #11 on: 11/08/2010 09:44 am »
So why not just make fully staged LV to begin with?

It looks like stage and a half designs provide more ascent flexibility because the point at which the engines are dropped can be different (e.g. when flying with or without an upper stage) without changing the size of the tanks.

I would like to see a performance comparison with a triple-body, propellant cross-feed design using the same six SSME.  If the side boosters were shorter than the core, they could be dropped at the same point where the other vehicle dropped its engines....

A triple-barrel version of this with an upper stage could probably get 150 tons into L.E.O. And unless the ejectable 4x engine module was recoverable in some way (see the Not-Shuttle C animation) I can't see the point of ejecting the outer 4 engines, just to squeeze a few more tons into orbit: Adds design complexity, too. Also -- which thrust setting would be optimum: 109% percent, or would more thrust start to sacrifice Isp?
« Last Edit: 11/08/2010 09:46 am by MATTBLAK »
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Offline simonbp

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Re: All-Cryo, Stage and a Half SLS
« Reply #12 on: 11/08/2010 02:50 pm »
Without the upper stage the rocket would be able to lift about the same mass as a Delta IV Heavy. However, it would be more expensive then the Delta IV. About the only advantage I can see is that it would be that it would be human rated. Am I missing something?

No, you're right, the single-stage version isn't all that useful, except for testing and possibly MPCV flights to ISS. I listed the single-stage version, however, to show the progression. By just changing the upper stage (and initial throttle levels), you cover the full range of payload mass from the largest rocket today to the largest rocket ever made. This allows you to go ahead and develop the common first stage, and then decide on the upper stages later, as you know what the missions will need. The missions will drive the rocket's performance, not the other way around.

Basically, it allows NASA to have its cake and eat it too. They get to develop the first stage over the next few years, while deferring the decision on an upper stage until the mission is actually decided. Then, they have a rocket (or set of rockets) that are perfectly suited to what they are doing, without having to wait for a full development cycle.
« Last Edit: 11/08/2010 02:51 pm by simonbp »

Offline simonbp

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Re: All-Cryo, Stage and a Half SLS
« Reply #13 on: 11/08/2010 03:07 pm »
So what do you get when you remove engines, thrust structure, and tank mass... Well if you put it together, you actually have pieces for a separate stage. :)

So why not just make fully staged LV to begin with? Is this all because you think we are lacking a suitable high-thrust 2nd stage engine for something that will stage lower?

Cost and complexity.

For one, two separate stages would weigh more than stage-and-a-half, and so do not provide that much of an advantage (loose more mass, but carry more to begin with). Plus, in addition to the extra engines on the second stage, you'd likely have to add 1-2 more SSMEs on the first stage to account for the higher overall GLOW. So, stage-and-a-half allows you to have fewer engines, fewer types of engines (no need for J-2X or airstart SSME for all but the largest versions), and fewer number of stages to develop and support. All that should (fingers crossed) lead to a lower overall cost per given performance.

SSME is a remarkable engine, and it is designed to one thing very well: start at sea level and still have very good efficiency in vacuum. Both stage-and-a-half and SRB-based concepts are designed to take full advantage of this fact. But only stage-and-a-half allows you to take advantage of it without support the entire SRB infrastructure.

Offline jongoff

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Re: All-Cryo, Stage and a Half SLS
« Reply #14 on: 11/08/2010 03:35 pm »
Simon,
I posted this on the other thread and was curious about what you had to say.  I figure it's relevant for either thread.  I don't *yet* have the software needed to really put ideas like this through their paces, but may soon be in a position to:

******
Ed,
Here's a crazy thought, what about using 3x RS-68As as the "boosters" and a single SSME core as the Sustainer?  I'm not necessarily a huge fan of using two different booster engines, but:

1-The lower initial Isp would be balanced by lower gravity losses (the less efficient engines lighten the stage faster getting up to speed quicker)

2-You shed more of the weight during the separation event, which means that the second half of the stage-and-a-half part has a better mass ratio

3-RS-68s are cheaper than SSMEs, so you wouldn't run out of the current batch as quick, overall cost would be lower, and you wouldn't need anywhere near as big of a production line for the SSMEs as you would with a 6-engine version.

My guess is you'd probably lose a bit of net performance, but save a lot on cost.  And the engines are still all American, existing, etc, etc.

Not sure if it's a good idea, just wanted to toss it out for discussion.

~Jon

Offline Patchouli

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Re: All-Cryo, Stage and a Half SLS
« Reply #15 on: 11/08/2010 03:55 pm »
Simon,
I posted this on the other thread and was curious about what you had to say.  I figure it's relevant for either thread.  I don't *yet* have the software needed to really put ideas like this through their paces, but may soon be in a position to:

******
Ed,
Here's a crazy thought, what about using 3x RS-68As as the "boosters" and a single SSME core as the Sustainer?  I'm not necessarily a huge fan of using two different booster engines, but:

1-The lower initial Isp would be balanced by lower gravity losses (the less efficient engines lighten the stage faster getting up to speed quicker)

2-You shed more of the weight during the separation event, which means that the second half of the stage-and-a-half part has a better mass ratio

3-RS-68s are cheaper than SSMEs, so you wouldn't run out of the current batch as quick, overall cost would be lower, and you wouldn't need anywhere near as big of a production line for the SSMEs as you would with a 6-engine version.

My guess is you'd probably lose a bit of net performance, but save a lot on cost.  And the engines are still all American, existing, etc, etc.

Not sure if it's a good idea, just wanted to toss it out for discussion.

~Jon

Lower gravity losses and being able to vac optimize the sustainer might offset the lower ISP.
The RS-68 actually has a slightly better sealevel ISP then the SSME.

I'd still like to see what two F9 cores adding 1.1Mlbs of thrust to the stack would do.
You'd probably have to pull 2 SSMEs or on the RS-68 remove one of them.

A rough estimate two kerolox boosters puts it in the 50T range but a Delta US also gets this.

Though with a J2-X stage it might be possible to get away with all RS-68s in the first stage but you loose stage and a half to orbit.

Not a big loss as there is no requirement for an optimized crew transport CCDev does that.
« Last Edit: 11/08/2010 04:19 pm by Patchouli »

Offline simonbp

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Re: All-Cryo, Stage and a Half SLS
« Reply #16 on: 11/08/2010 07:00 pm »
Yeah, my biggest worry would also be the mixed-engine aspect of it, as well as the question of "man-rating" and what that would cost (SSME neatly side-steps that issue). On the other hand, having a 3xRS-68 booster section for the initial versions, and the possibility of a compatible 4xRS-68 booster section for heavy payloads it very intriguing...

I'll run some numbers tonight (again with simple dV-fitting), and see what I get...

Offline kraisee

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Re: All-Cryo, Stage and a Half SLS
« Reply #17 on: 11/08/2010 07:07 pm »
WRT RS-68 -- Base Heating will be a problem.   Guaranteed.

Do not make the mistake of thinking it is the SRB plume interaction which causes this issue -- it is not.

Also it is not just an issue for inboard engines either.   Outboard engines still have at least half their structure facing inwards, so are subject to exactly the same problems.

If you wish to use RS-68, you should budget for a minimum $2+ billion/6+ year development effort to make the RS-68 Regen-HR.

Ross.
« Last Edit: 11/08/2010 07:10 pm by kraisee »
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Offline jongoff

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Re: All-Cryo, Stage and a Half SLS
« Reply #18 on: 11/08/2010 07:21 pm »
WRT RS-68 -- Base Heating will be a problem.   Guaranteed.

Do not make the mistake of thinking it is the SRB plume interaction which causes this issue -- it is not.

I'm skeptical about this.  After all, the DIV-H uses multiple RS-68s and seems to do just fine.  The non-SRB engines all have much less luminous flames which should decrease radiation heat transfer.  And I can't help but think that if recirculation in the back end is such a big worry that you couldn't spend a little bit of money on shaping the boattail to minimize the effect.  I can believe with huge, high-luminosity exhaust SRBs that things would get tricky, but I have a hard time believing that somehow SSMEs which are far more complex, run at higher pressures on lower margins are somehow going to be magically cheaper than just solving the airflow at the back of the engines, or adding some external insulation to the nozzle bells.  Maybe I'm completely wrong, but this smells like the "EELV black-zone" kind of FUD. 

~Jon

Offline simonbp

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Re: All-Cryo, Stage and a Half SLS
« Reply #19 on: 11/08/2010 07:25 pm »
WRT RS-68 -- Base Heating will be a problem.   Guaranteed.

Yeah, I can well believe it; Delta IV-H always looks like it's caught on fire on liftoff...

What separation did you find was the minimum for SSMEs? Eyeballing the Orbiters, I was giving them about 1.5 meters between the center of each engine, but it would be reassuring to know what they really should be...

Offline MATTBLAK

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Re: All-Cryo, Stage and a Half SLS
« Reply #20 on: 11/08/2010 07:32 pm »
In answer to Jonoff: There is significant seperation between the Delta IV-H's engines.
« Last Edit: 11/08/2010 07:32 pm by MATTBLAK »
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Offline Patchouli

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Re: All-Cryo, Stage and a Half SLS
« Reply #21 on: 11/08/2010 07:42 pm »
WRT RS-68 -- Base Heating will be a problem.   Guaranteed.

Yeah, I can well believe it; Delta IV-H always looks like it's caught on fire on liftoff...

What separation did you find was the minimum for SSMEs? Eyeballing the Orbiters, I was giving them about 1.5 meters between the center of each engine, but it would be reassuring to know what they really should be...

There might be two solutions to that problem.

First there is the relatively speaking cooler turbopump exhaust that could be use to keep the hotter chamber gasses from recirculating under the vehicle.

A second solution would be to borrow a trick from the Soviet N1 and use air argumentation to cool the engines which also should net a little more thrust.
An all cryogenic vehicle can use every last bit of sea level thrust it can get.

Between the two I think the base heating issue with the RS-68A can be eliminated.
« Last Edit: 11/08/2010 07:44 pm by Patchouli »

Offline kraisee

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Re: All-Cryo, Stage and a Half SLS
« Reply #22 on: 11/08/2010 07:51 pm »
What separation did you find was the minimum for SSMEs? Eyeballing the Orbiters, I was giving them about 1.5 meters between the center of each engine, but it would be reassuring to know what they really should be...

I believe its about 114".   My understanding is that this distance is a bad compromise they had no choice, but to accept, on Shuttle.

They had to accept & waive a significant failure mode -- that of a hard-over TVC failure could force the 'dead' nozzle to impinge on another nozzle and thereby cause a Cat-A vehicle control failure and Loss of Vehicle/Crew.   You probably want a little more space.

Ross.
« Last Edit: 11/08/2010 07:51 pm by kraisee »
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Offline kraisee

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Re: All-Cryo, Stage and a Half SLS
« Reply #23 on: 11/08/2010 07:52 pm »
Between the two I think the base heating issue with the RS-68A can be eliminated.

After many, many months of analysis, both MSFC and Boeing have independently assessed the approach and both have concluded that it is a bad option.

I wish you the best of luck solving something they can't.

Ross.
« Last Edit: 11/08/2010 07:54 pm by kraisee »
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Re: All-Cryo, Stage and a Half SLS
« Reply #24 on: 11/08/2010 07:57 pm »
the question of "man-rating" and what that would cost (SSME neatly side-steps that issue).

Is your concern political or technical?  Politically, RS-68 human-rating is certainly a can of worms.  But the technical case is fairly easily made that RS-68 (with some minor engine health monitoring) presents no credible threat to crew safety.

The reasoning is:

- With health monitoring, RS-68 failures would with very high probability lead to non-destructive engine shutdown.

- There's only one plausible scenario where an RS-68 shutdown leads to an abort.  That's when the failure occurs near lift-off, since shortly after that sufficient thrust is available from the other engines.  (And they're all feeding from the same tanks, so no propellant is lost.)

- Even in the abort case, the launch vehicle is still able to create conditions ideally suited for safe utilization of the launch escape system.

Thus isn't the RS-68 human-rating concern essentially political hog-wash?
« Last Edit: 11/08/2010 07:58 pm by sdsds »
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Offline Patchouli

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Re: All-Cryo, Stage and a Half SLS
« Reply #25 on: 11/08/2010 08:34 pm »
Between the two I think the base heating issue with the RS-68A can be eliminated.

After many, many months of analysis, both MSFC and Boeing have independently assessed the approach and both have concluded that it is a bad option.

I wish you the best of luck solving something they can't.

Ross.

They also were trying to make it work with the extra heat input of two massive SRBs which are not present on the all cryogenic core.

Those things are so hot they even end up cooking the bottom of the ET on the shuttle.

The problem may be significantly easier to solve without the SRBs.
I don't think the Delta IV core would work with two Titian SRMs as their heat input would be too much.

The SSME still has the advantage of being already man rated but it also is expensive and a little low on thrust for an unargumented first stage.

« Last Edit: 11/08/2010 08:42 pm by Patchouli »

Offline kraisee

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Re: All-Cryo, Stage and a Half SLS
« Reply #26 on: 11/08/2010 08:38 pm »
The problem may be significantly easier to solve without the SRBs.

That's what I was saying above -- that is a mistaken assumption.

My information says its still a very big problem post-SRB jettison, too.

Ross.
« Last Edit: 11/08/2010 08:39 pm by kraisee »
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Offline kraisee

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Re: All-Cryo, Stage and a Half SLS
« Reply #27 on: 11/08/2010 08:41 pm »
Thus isn't the RS-68 human-rating concern essentially political hog-wash?

I wouldn't try telling that to NASA's S&MA folks.   They'd be likely to lynch you :)

Ross.
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Re: All-Cryo, Stage and a Half SLS
« Reply #28 on: 11/08/2010 08:42 pm »
The problem may be significantly easier to solve without the SRBs.

That's what I was saying above -- that is a mistaken assumption.

My information says its still a very big problem post-SRB jettison, too.

Ross.

As I said, color me skeptical.  We know that there are configurations where multiple RS-68s are flight-proven to work fine.  When we're talking about a cost difference of over $100M per flight, I'm *sure* that another configuration can be found that routes air in a way that makes it not be a big issue.  The black zones for EELVs were supposed to be a show-stopper too.

~Jon

Offline Patchouli

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Re: All-Cryo, Stage and a Half SLS
« Reply #29 on: 11/08/2010 08:52 pm »
The problem may be significantly easier to solve without the SRBs.

That's what I was saying above -- that is a mistaken assumption.

My information says its still a very big problem post-SRB jettison, too.

Ross.

As I said, color me skeptical.  We know that there are configurations where multiple RS-68s are flight-proven to work fine.  When we're talking about a cost difference of over $100M per flight, I'm *sure* that another configuration can be found that routes air in a way that makes it not be a big issue.  The black zones for EELVs were supposed to be a show-stopper too.

~Jon

The issue seems to be heat soaking though the nozzle wall and causing delamination of the ablative insert.

I wonder if something as simple as wrapping the engine in FRCI or adding a heat shield with cool gas ducted between the shield and the engine may be enough to prevent it.

« Last Edit: 11/08/2010 08:56 pm by Patchouli »

Offline simonbp

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Re: All-Cryo, Stage and a Half SLS
« Reply #30 on: 11/08/2010 09:00 pm »
What Ross is implying may be a situation like below, where the gas generator exhaust in the lee of near-vacuum hypersonic flow builds up and creates a huge stagnant plasma cloud around the engines. S-IC required some pretty large airscoops and thermal insulation to get around this.

http://upload.wikimedia.org/wikipedia/commons/2/2a/Saturn_V_in_flight.jpg

This isn't as huge an issue for Delta IV Heavy, as it has almost open flow around each engine. It would, however, be an an issue with any close cluster of RS-68s. And with the much hotter exhaust temps of LOX/LH2, the Saturn V measures may not be enough.

SSME, with a staged-combustion (i.e. closed) cycle, would not be nearly as bad at base heating. This, plus the manrating issues (solvable or not), have me agreeing with Ross that SSME (or rather, RS-25E) would be the best choice at this point.

Offline FinalFrontier

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Re: All-Cryo, Stage and a Half SLS
« Reply #31 on: 11/09/2010 04:11 am »
WRT RS-68 -- Base Heating will be a problem.   Guaranteed.

Yeah, I can well believe it; Delta IV-H always looks like it's caught on fire on liftoff...

What separation did you find was the minimum for SSMEs? Eyeballing the Orbiters, I was giving them about 1.5 meters between the center of each engine, but it would be reassuring to know what they really should be...

There might be two solutions to that problem.

First there is the relatively speaking cooler turbopump exhaust that could be use to keep the hotter chamber gasses from recirculating under the vehicle.

A second solution would be to borrow a trick from the Soviet N1 and use air argumentation to cool the engines which also should net a little more thrust.
An all cryogenic vehicle can use every last bit of sea level thrust it can get.

Between the two I think the base heating issue with the RS-68A can be eliminated.

N1. As in the giant soviet moon rocket that exploded 4 out of 4 trys? If thats correct, as I think it is, Please don't reference an utterly failed design as something credible. As far as I am concerned nothing about that thing was workable. Energia is a far better example.
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Offline kraisee

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Re: All-Cryo, Stage and a Half SLS
« Reply #32 on: 11/09/2010 04:16 am »
N-1 used NK-33's to power it -- and they were regen cooled nozzles.   That's why base heating was not a problem (although other things were).

You really need a regen if you're going to punch a large 8m+ hole through the air and then have your nozzles in the low pressure area immediately following that.

SSME is regen.   RS-68 is not.   And adding a regen nozzle is NOT a simple upgrade.

Ross.
« Last Edit: 11/09/2010 04:18 am by kraisee »
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Offline Patchouli

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Re: All-Cryo, Stage and a Half SLS
« Reply #33 on: 11/09/2010 04:36 am »

N1. As in the giant soviet moon rocket that exploded 4 out of 4 trys? If thats correct, as I think it is, Please don't reference an utterly failed design as something credible. As far as I am concerned nothing about that thing was workable. Energia is a far better example.

Not all ideas in it were bad the NK-33 probably is a good engine the biggest problem with the N-1 was not the vehicle but how the program was run.

They never built a static test stand as it was deemed too costly.

The Saturn V probably would have ended up like the N-1 without static testing.

Still the second Saturn V to fly almost did not make it to orbit.
http://www.moonrace2001.org/sv_history.shtml

The N-1 only flew with the NK-15 as the program was canceled before the NK-33 could enter service.

BTW I do agree Enegia is better then the N-1 in fact I think it's better then the Saturn V due to it's flexibility.
If you consider it put a 100T payload Buran into a 51 degree orbit it actually was more powerful then the 2 stage Saturn V the INT-21.
It's the form I'd make SLS in if I had my way.
« Last Edit: 11/09/2010 04:59 am by Patchouli »

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Re: All-Cryo, Stage and a Half SLS
« Reply #34 on: 11/09/2010 05:01 am »
Regardless, N-1 is not a good case to compare, as it's totally different aerodynamically. Saturn V (or even Saturn I) is closer, but still not the same.

The result seems to be that you need a new regen, man-rated version of RS-68 to work in this concept. By that point, you basically have an underperforming, gas-generator version of SSME. Better just to start with SSME and evolve it latter as necessary.

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Re: All-Cryo, Stage and a Half SLS
« Reply #35 on: 11/09/2010 05:08 am »
What Ross is implying may be a situation like below, where the gas generator exhaust in the lee of near-vacuum hypersonic flow builds up and creates a huge stagnant plasma cloud around the engines. S-IC required some pretty large airscoops and thermal insulation to get around this.

http://upload.wikimedia.org/wikipedia/commons/2/2a/Saturn_V_in_flight.jpg

There's a more recent kerolox cluster LV example - The Falcon 9. They appear to have been able to cluster 9 engines very close to each other. it's hard to tell if it experienced the same recirculation effects as the Saturn V, but of course it is another example of a cluster engine LV with regen engines.

Sure, the F9 core is not very wide, but one has to wonder if the dense arrangement of engines actually ended up reducing the recirculation effect.

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Re: All-Cryo, Stage and a Half SLS
« Reply #36 on: 11/09/2010 05:27 am »
Here's a sketch of the engine layout.  This is all based on the NLS-2 concept from the late 1980s-early 1990s.  Plume recirculation effects were studied in depth for this design and found not to be a problem for the STME powered rocket, so no problem for SSME either. 

An RS-68 powered design would only have four engines for this payload capability.  As mentioned earlier, they could be spaced further apart on an "All-Liquid" SDHV than they already are on Delta 4 Heavy.  Heating would be an area of interesting development effort, but one that appears doable, in my opinion, without needing regen nozzle.

 - Ed Kyle

Offline simonbp

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Re: All-Cryo, Stage and a Half SLS
« Reply #37 on: 11/09/2010 05:36 am »
Sure, the F9 core is not very wide, but one has to wonder if the dense arrangement of engines actually ended up reducing the recirculation effect.

That's a good point; on Falcon 9 the engines are very close, and effectively cover the entire base area of the rocket, and so leave little area for stagnant flow to accumulate. Indeed, it's the opposite of N-1 in that respect.

Still, though, the spacing of either SSMEs or RS-68s on a single-stick SLS is such that there is plenty of room for stagnant flow to accumulate. So, we're back to either needing massive ram air scoops and thermal blankets or regen nozzles for RS-68 to keep from melting. Or, just go with SSMEs and avoid the whole mess...

Offline Patchouli

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Re: All-Cryo, Stage and a Half SLS
« Reply #38 on: 11/09/2010 05:38 am »
What Ross is implying may be a situation like below, where the gas generator exhaust in the lee of near-vacuum hypersonic flow builds up and creates a huge stagnant plasma cloud around the engines. S-IC required some pretty large airscoops and thermal insulation to get around this.

http://upload.wikimedia.org/wikipedia/commons/2/2a/Saturn_V_in_flight.jpg

There's a more recent kerolox cluster LV example - The Falcon 9. They appear to have been able to cluster 9 engines very close to each other. it's hard to tell if it experienced the same recirculation effects as the Saturn V, but of course it is another example of a cluster engine LV with regen engines.

Sure, the F9 core is not very wide, but one has to wonder if the dense arrangement of engines actually ended up reducing the recirculation effect.

I wonder if base heating is why Spacex ended up designing the Merlin 1C?

Merlin 1A probably would have had the same issues the RS-68 has.

Related I wonder if F9 core based strapons could eventually be used to upgrade the all cryo SLS.
Such reduce the cost of the low end variant ie make it fly with four or less SSME's and boost the six SSME RL-10 upper stage vehicle past 70T.

Have them as a block II upgraded.

« Last Edit: 11/09/2010 05:51 am by Patchouli »

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Re: All-Cryo, Stage and a Half SLS
« Reply #39 on: 11/09/2010 06:15 pm »
To save me reverse-engineering, would you mind posting a summary of the masses you're using for the two stage-and-a-half configurations?

6xSSME (4xSSME Drop)
Mprop = 693 tonnes
Mburnout = 53 tonnes
[...]
This all stands for some serious tweaking, of course.

Achieving this burnout mass looks like a challenge!  In comparison the J-130 core is over 63 tonnes dry.  Here's a pessimistic analysis of the all-cryo core burnout mass:

The core prop capacity is 94% that of J-130, but that doesn't imply the core will mass 94% of the J-130.  Using the (realistic?) estimate of 1% savings in dry mass for every 2% reduction in prop mass, the all-cryo dry core would be 97% of the J-130's 63,725 kg.  But this core also carries one fewer SSME, saving 3,177 kg, and needs to carry the thrust of two fewer SSMEs.  (J-130 core is designed for 4 SSME.)  If the mass of the thrust structure for an SSME was 20% of the SSME mass (wrong?) that saves another 1271 kg.

 (63,725 * 0.97) - 3,177 - 1,271 = 57,365

But that's just the dry mass.  The burnout mass includes propellant reserve and residuals.  What's the more optimistic reasoning that gets the burnout mass down to 53 tonnes?
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Re: All-Cryo, Stage and a Half SLS
« Reply #40 on: 11/09/2010 10:08 pm »
To save me reverse-engineering, would you mind posting a summary of the masses you're using for the two stage-and-a-half configurations?

6xSSME (4xSSME Drop)
Mprop = 693 tonnes
Mburnout = 53 tonnes
[...]
This all stands for some serious tweaking, of course.

Achieving this burnout mass looks like a challenge!  In comparison the J-130 core is over 63 tonnes dry.  Here's a pessimistic analysis of the all-cryo core burnout mass:

The core prop capacity is 94% that of J-130, but that doesn't imply the core will mass 94% of the J-130.  Using the (realistic?) estimate of 1% savings in dry mass for every 2% reduction in prop mass, the all-cryo dry core would be 97% of the J-130's 63,725 kg.  But this core also carries one fewer SSME, saving 3,177 kg, and needs to carry the thrust of two fewer SSMEs.  (J-130 core is designed for 4 SSME.)  If the mass of the thrust structure for an SSME was 20% of the SSME mass (wrong?) that saves another 1271 kg.

 (63,725 * 0.97) - 3,177 - 1,271 = 57,365

But that's just the dry mass.  The burnout mass includes propellant reserve and residuals.  What's the more optimistic reasoning that gets the burnout mass down to 53 tonnes?

Dropping the booster package, with four 3.2 tonne engines, their plumbing, and with a lot of structure used to 1)support the vehicle on the pad and 2)transfer forces from the four engines to the core structure, should allow the remaining 2-engine core to be lighter than a standard first stage.  That is how Atlas worked, and how NLS-2 (or was it NLS 1.5?) was planned to work.  The NLS core was only going to weigh about 7.4 % as much at burnout (including residuals) as the core plus booster package were going to weigh at launch.

 - Ed Kyle
« Last Edit: 11/09/2010 11:03 pm by edkyle99 »

Offline simonbp

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Re: All-Cryo, Stage and a Half SLS
« Reply #41 on: 11/09/2010 11:52 pm »
Considering how relevant NLS is to this concept, I'm going to start a list of NLS documents on NTRS:

Plume separation (1994): http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19970005118_1997004622.pdf

Martin structures presentations (1991): http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930007493_1993007493.pdf

Martin avionics and systems (1991): http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930013987_1993013987.pdf

Martin propulsion presentations (1991): http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930014526_1993014526.pdf

Rockwell reports (several of them, 1994): http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940028594_1994028594.pdf

Rockwell cost estimates (1994): http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940030406_1994030406.pdf

Base heating study (1992): http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930012823_1993012823.pdf

Wind tunnel testing of the 1.5 configuration (1994): http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940033066_1994033066.pdf

Rockwell base heating CFD (1993): http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940033066_1994033066.pdf

More wind tunnel testing (1994): http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19950005297_1995105297.pdf

1.5 stage aerodynamics (1994): http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19970002923_1996098982.pdf

Loads and models databook (1992): http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19920020972_1992020972.pdf

Feel free to add more as you find them!

Offline simonbp

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Re: All-Cryo, Stage and a Half SLS
« Reply #42 on: 11/10/2010 12:01 am »
Dropping the booster package, with four 3.2 tonne engines, their plumbing, and with a lot of structure used to 1)support the vehicle on the pad and 2)transfer forces from the four engines to the core structure, should allow the remaining 2-engine core to be lighter than a standard first stage.

Also, the Direct core stage has to deal with the (not insignificant) loads of the SRBs, which go through an entirely separate load path to the main engines, and which are significantly modulated by SRB thrust oscillations. Indeed, there seems to be considerable debate in the contractor literature as to whether it was worth it or not to have a common first/core stage between the 1.5 stage (NLS-2) and SRB  (NLS-1, proto-Direct) versions, as the NLS-1 core weighed so much more...
« Last Edit: 11/10/2010 12:01 am by simonbp »

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Re: All-Cryo, Stage and a Half SLS
« Reply #43 on: 11/10/2010 04:53 am »
Dropping the booster package, with four 3.2 tonne engines, their plumbing, and with a lot of structure used to 1)support the vehicle on the pad and 2)transfer forces from the four engines to the core structure, should allow the remaining 2-engine core to be lighter than a standard first stage.

Also, the Direct core stage has to deal with the (not insignificant) loads of the SRBs, which go through an entirely separate load path to the main engines, and which are significantly modulated by SRB thrust oscillations. Indeed, there seems to be considerable debate in the contractor literature as to whether it was worth it or not to have a common first/core stage between the 1.5 stage (NLS-2) and SRB  (NLS-1, proto-Direct) versions, as the NLS-1 core weighed so much more...

This is a truly remarkable design!  Indeed it is nearly incredible, and therein lies the rub.  Because it does not require ATK SRBs its credibility will be challenged.  The NLS cycle 0 documents referenced above obviously help immensely on this front!  In particular they show the concept (instantiated in the NLS-2 vehicle) could get 50,000 lbs (22.68 metric tons) to LEO even suffering with the added mass burden imposed by a "common core stage" shared with the NLS-1 vehicle.

The challenge though is to show that without that burden (and with SSME rather than STME) this design will take a full lunar Orion to orbit with full LAS protection and with a hefty margin.

Towards that end, attached is an analysis from the first post on this thread.  It says, "LAS ejected at booster separation."  What reasoning supports that timing?  Why doesn't the LAS need to be carried further?
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Offline simonbp

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Re: All-Cryo, Stage and a Half SLS
« Reply #44 on: 11/10/2010 06:08 am »
Towards that end, attached is an analysis from the first post on this thread.  It says, "LAS ejected at booster separation."  What reasoning supports that timing?  Why doesn't the LAS need to be carried further?

'Cause I was lazy.

But seriously, main reasoning was that after the boosters are gotten rid of, the acceleration of the vehicle is sufficiently low that the SM could perform an abort. That's why Apollo lost the tower after S-IC separation, and IIRC, the Ares I profile called for tower jettison after AIUS ignition. The fact that making the tower sep and booster sep events simultaneous simplified the math didn't hurt...

Also, on the non-LAS flights, note that I carried the faring/payload adaptor all the way to LEO/TLI. That's not realistic (faring would be lost around second stage ignition), but since I didn't want to guess at the relative masses of the faring and adaptor, I just erred on the side of caution...

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Re: All-Cryo, Stage and a Half SLS
« Reply #45 on: 11/10/2010 07:16 am »
Towards that end, attached is an analysis from the first post on this thread.  It says, "LAS ejected at booster separation."  What reasoning supports that timing?  Why doesn't the LAS need to be carried further?

'Cause I was lazy.

But seriously, main reasoning was that after the boosters are gotten rid of, the acceleration of the vehicle is sufficiently low that the SM could perform an abort. ...

I don't think the SM would perform an abort under any kind of thrust from the stage it sits on. The ideea was, IIRC, that the thrust from liquid fueled engines would be first terminated, and only after that the CM+SM would separate from the stack and perform the rest of the launch abort.

Now, wrt timing of LAS jettison (nominal flight): the stack acceleration must not be to high. The CxP LAS jettison motor is required to accelerate the LAS at 1g relative to the main stack, for a duration of a few seconds. The CxP wants to eject the LAS in the first 30 seconds after the u.s. engine ignition. Wait to long and you need a larger jettison motor - and impose a LAS weight penalty.

What is the acceleration of the proposed all-cryo launcher (no u.s.) at the time of dropping the booster engines ?


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Re: All-Cryo, Stage and a Half SLS
« Reply #46 on: 11/10/2010 11:21 am »
Jettisoning of the LAS is not determined by the vehicle acceleration but by the speed and strength of any blast wave.   The LAS is jettisoned a time after upperstage ignition after vehicle rates have settled down.  Upperstage ignition is the last "major" vehicle state change that has a higher change of causing a explosion.  Vehicles usually don't explode during steady state and if they did or were to, the SM engines are enough to out run the blast wave.

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Re: All-Cryo, Stage and a Half SLS
« Reply #47 on: 11/10/2010 02:15 pm »
Jettisoning of the LAS is not determined by the vehicle acceleration but by the speed and strength of any blast wave.   The LAS is jettisoned a time after upperstage ignition after vehicle rates have settled down.  Upperstage ignition is the last "major" vehicle state change that has a higher change of causing a explosion.  Vehicles usually don't explode during steady state and if they did or were to, the SM engines are enough to out run the blast wave.

Ah! Thanks Jim, I hadn't thought about that way. Though, it does seem to conflict with the Saturn V launch sequence, which jettisoned the LES right after S-IC/S-II interstage separation, with the initial S-IVB ignition still to go. Is that because the acceleration of the S-IVB was low enough to allow for abort with the SM?

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Re: All-Cryo, Stage and a Half SLS
« Reply #48 on: 11/11/2010 12:58 pm »
Note a TAN SSME discussion at "Re: All-Liquid SDLV options"


Just went over it.  TAN only improved it by 100%, rather than the 130% I was estimating.  Ok, so we're looking at 800k lbs of thrust.


800,000 lbs of thrust from a TAN SSME might be nice for a later upgraded version of this "All-Cryo, Stage and a Half SLS".

Cheers!
« Last Edit: 11/12/2010 11:54 pm by HappyMartian »
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Re: All-Cryo, Stage and a Half SLS
« Reply #49 on: 11/11/2010 01:24 pm »
Jettisoning of the LAS is not determined by the vehicle acceleration but by the speed and strength of any blast wave.   The LAS is jettisoned a time after upperstage ignition after vehicle rates have settled down.  Upperstage ignition is the last "major" vehicle state change that has a higher change of causing a explosion.  Vehicles usually don't explode during steady state and if they did or were to, the SM engines are enough to out run the blast wave.

Ah! Thanks Jim, I hadn't thought about that way. Though, it does seem to conflict with the Saturn V launch sequence, which jettisoned the LES right after S-IC/S-II interstage separation, with the initial S-IVB ignition still to go. Is that because the acceleration of the S-IVB was low enough to allow for abort with the SM?

 I forgot to add that air density/pressure at altitude is a major factor also.  No air, no pressure wave to propagate.  That is a large player in determining LAS jettison and where the SM can take over.

Remember that LV engines shutdown in aborts (whether vehicle, crew or range safety initiated)  and so stage acceleration is not a factor, unlike SRM's. 
 
I shouldn't have said last "major".  I believe that there were some scenarios (my memory is fuzzy on this) that the SM could get into orbit during a  portion of the S-IVB burn or the S-IVB could cover a large portion of the S-II burn.

« Last Edit: 11/11/2010 01:30 pm by Jim »

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Re: All-Cryo, Stage and a Half SLS
« Reply #50 on: 11/11/2010 01:31 pm »
I believe that there were some scenarios (my memory is fuzzy on this) that the SM could get into orbit during a  portion of the S-IVB burn or the S-IVB could cover a large portion of the S-II burn.

It's not a primary source, but the Wikipedia article on Apollo abort modes confirms the S-IVB and SM aborts.  (It includes some original documents, but I'm to lazy to peruse them).

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Re: All-Cryo, Stage and a Half SLS
« Reply #51 on: 11/11/2010 06:24 pm »
I forgot to add that air density/pressure at altitude is a major factor also.  No air, no pressure wave to propagate.  That is a large player in determining LAS jettison and where the SM can take over.

I'll need to look it up now, but IIRC the NLS-2 staging point was after the gravity turn, and so at fairly high altitude/low pressure. Meaning it still sounds reasonable to assume a LAS jettison around the time the booster engines are ejected.

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Re: All-Cryo, Stage and a Half SLS
« Reply #52 on: 11/13/2010 02:06 am »
I'll need to look it up now, but IIRC the NLS-2 staging point was after the gravity turn, and so at fairly high altitude/low pressure. Meaning it still sounds reasonable to assume a LAS jettison around the time the booster engines are ejected.

My notes have one design jettisoning its booster package (or whatever they called it) at T+161.5 seconds, or 2 minutes 41.5 seconds, but that was with STMEs.  An SSME design would probably stage quite a bit later (due to lower propellant burn rate and better "gas mileage").  My model has booster drop at (EDITED:) T+185 seconds or later.     

 - Ed Kyle
« Last Edit: 11/14/2010 02:21 am by edkyle99 »

Offline simonbp

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Re: All-Cryo, Stage and a Half SLS
« Reply #53 on: 11/14/2010 02:19 am »
Here's a rough draft of a comparison between the two designs. The renderings are low-res placeholders, as is most of the text. Suggestions encouraged!

Note that I went with a common first/core stage, and changed the booster pack to RS-68Bs on the Block II version. This addresses the T/W issues (allowing a really big upper stage) and the timeline for RS-68B. So you only have to develop RS-68B if you want the big rocket. But if you do develop it, you can keep the same first/core stage...

EDIT: Fixed spelling...
« Last Edit: 11/14/2010 03:37 am by simonbp »

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Re: All-Cryo, Stage and a Half SLS
« Reply #54 on: 11/14/2010 04:27 am »
Note a TAN SSME discussion at "Re: All-Liquid SDLV options"
Just went over it.  TAN only improved it by 100%, rather than the 130% I was estimating.  Ok, so we're looking at 800k lbs of thrust.
800,000 lbs of thrust from a TAN SSME might be nice for a later upgraded version of this "All-Cryo, Stage and a Half SLS".

Cheers!

TAN requires fairly extensive modifications to the turbopumps, hot gas manifold, etc. in order to increase propellant flow rate and to get the proper pressure ratio between the main injector and the TAN injector.  It's almost a completely new engine, but for some reason the Aerojet study doesn't increase the nozzle area ratio to boost the maximum liftoff thrust and vacuum Isp. 

A fully-exploited TAN SSME could do 1.2Mlbf and completely eliminate the booster engine jettison package in this design.  Just two TAN SSMEs for a true heavy-lift SSTO.  Yeah, it would be one heck of an engine development program, but the performance potential can be honestly described as game-changing.  Add TPS, aerosurfaces, and landing gear, and you're pretty close to the holy grail...

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Re: All-Cryo, Stage and a Half SLS
« Reply #55 on: 11/14/2010 06:30 am »
For a 6xRL10A-4-3 upper stage, the breakdown is as follows
Stg 1
6xSSME (4xSSME Drop)
T(s/l) = 1,134 tonnes
ISP = 363 sec (SL)/455 sec (vac)
Mtotal = 755 tonnes
Mprop = 693 tonnes
Mbeforedrop = 260 tonnes
Mafterdrop = 244 tonnes
Mburnout = 53 tonnes
...
PLF = 5 tonnes
PL = 70 tonnes

   These are exciting performance figures, but how do you get the core dry stage mass of Mtotal - Mprop = 755 - 693 = 62mT?
 
A J-130 core is ~64mT:
  - add 3xSSME @ 3.2mT = 74mT. Then,
  - add reinforcement of the thrust structure and more complicated plumbing (for 2-3 more SSME, plus inefficiency of having two thrust structures) (? mT)
  - add the separation interfaces, perhaps derived from the MPS disconnects (? mT) and conventional staging hardware (? mT)
  - subtract the unneeded intertank thrust beam (somewhere in the AJAX threads, not that much) (? mT)
  - subtract a little for less tankage (Mprop = 693 vs. 735 in J-130) (few mT?)

   Back when I looked at the 5xSSME 0-LRB-AJAX (unstaging) core, I assumed (fairly crudely) a dry mass of 70mT. What am I missing?
    -Alex

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Re: All-Cryo, Stage and a Half SLS
« Reply #56 on: 11/14/2010 09:24 am »
Here's a rough draft of a comparison between the two designs. The renderings are low-res placeholders, as is most of the text. Suggestions encouraged!

Note that I went with a common first/core stage, and changed the booster pack to RS-68Bs on the Block II version. This addresses the T/W issues (allowing a really big upper stage) and the timeline for RS-68B. So you only have to develop RS-68B if you want the big rocket. But if you do develop it, you can keep the same first/core stage...

EDIT: Fixed spelling...
Just an idea: Maybe you could add liquid rocket boosters as a 'Block II'. Then you don't have to develop regen RS-68. Block I = 'Stage and a halve'. Block II = AJAX
« Last Edit: 11/14/2010 09:26 am by Chris611 »

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Re: All-Cryo, Stage and a Half SLS
« Reply #57 on: 11/14/2010 06:06 pm »
For a 6xRL10A-4-3 upper stage, the breakdown is as follows
Stg 1
6xSSME (4xSSME Drop)
T(s/l) = 1,134 tonnes
ISP = 363 sec (SL)/455 sec (vac)
Mtotal = 755 tonnes
Mprop = 693 tonnes
Mbeforedrop = 260 tonnes
Mafterdrop = 244 tonnes
Mburnout = 53 tonnes
...
PLF = 5 tonnes
PL = 70 tonnes

   These are exciting performance figures, but how do you get the core dry stage mass of Mtotal - Mprop = 755 - 693 = 62mT?
 
A J-130 core is ~64mT:
  - add 3xSSME @ 3.2mT = 74mT. Then,
  - add reinforcement of the thrust structure and more complicated plumbing (for 2-3 more SSME, plus inefficiency of having two thrust structures) (? mT)
  - add the separation interfaces, perhaps derived from the MPS disconnects (? mT) and conventional staging hardware (? mT)
  - subtract the unneeded intertank thrust beam (somewhere in the AJAX threads, not that much) (? mT)
  - subtract a little for less tankage (Mprop = 693 vs. 735 in J-130) (few mT?)

   Back when I looked at the 5xSSME 0-LRB-AJAX (unstaging) core, I assumed (fairly crudely) a dry mass of 70mT. What am I missing?
    -Alex

One part of the difference is that this core stage is smaller than most ET-based core stage designs.  It should weigh less for that reason alone.  On the other hand, I did start with the Boeing numbers.  Those do seem to be a bit optimistic for this application.  On the other-other hand, I appear to have underestimated the booster pack mass, which actually hurt my payload estimate (since a too-light estimate left my remaining core stage heavier than it should have been).

Adding more dry mass would take away a bit of LEO capability from the 2.5 stage design, but would cause a more serious reduction on the 1.5 stage rocket, probably rendering it untenable (if it ever was) in comparison to EELV Heavy. 

 - Ed Kyle

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Re: All-Cryo, Stage and a Half SLS
« Reply #58 on: 11/14/2010 06:37 pm »
Yeah, it's probably best to sell it as a cheap way to get to 70 tons, with the CLV 1.5 stage as an optional bonus.

You might be able to bump the CLV capacity if you use the SM as a kick stage, like for Ares I...

Offline Patchouli

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Re: All-Cryo, Stage and a Half SLS
« Reply #59 on: 11/14/2010 06:45 pm »
Note a TAN SSME discussion at "Re: All-Liquid SDLV options"
Just went over it.  TAN only improved it by 100%, rather than the 130% I was estimating.  Ok, so we're looking at 800k lbs of thrust.
800,000 lbs of thrust from a TAN SSME might be nice for a later upgraded version of this "All-Cryo, Stage and a Half SLS".

Cheers!

TAN requires fairly extensive modifications to the turbopumps, hot gas manifold, etc. in order to increase propellant flow rate and to get the proper pressure ratio between the main injector and the TAN injector.  It's almost a completely new engine, but for some reason the Aerojet study doesn't increase the nozzle area ratio to boost the maximum liftoff thrust and vacuum Isp. 

A fully-exploited TAN SSME could do 1.2Mlbf and completely eliminate the booster engine jettison package in this design.  Just two TAN SSMEs for a true heavy-lift SSTO.  Yeah, it would be one heck of an engine development program, but the performance potential can be honestly described as game-changing.  Add TPS, aerosurfaces, and landing gear, and you're pretty close to the holy grail...

The money saved by not having to maintain the SRB infrastructure and having CCDev handle ISS could pay for evolving the SSME into a tripropellant engine like the RD-701.
http://www.buran.ru/htm/rd-701.htm
More on it including description of a successful test article.
http://www.astronautix.com/engines/rd701.htm
Eventually this engine could be used in a new RLV.
DCY or the X33 both would be a lot easier with such as an engine.
This way SLS in a way becomes a road to the future something Ares was not.
« Last Edit: 11/14/2010 06:55 pm by Patchouli »

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Re: All-Cryo, Stage and a Half SLS
« Reply #60 on: 11/14/2010 06:51 pm »
The money saved by not having to maintain the SRB infrastructure and having CCDev handle ISS could pay for evolving the SSME into a tripropellant engine like the RD-701.
http://www.buran.ru/htm/rd-701.htm

The money saved by not having the SRB infrastructure to support will allow SLS to fly in the first place, with little left over for TAN, triprop, and/or other expensive and complex concepts.

If we didn't already have SSME, the motivation would be higher to do more engine development. But a high-thrust, high Isp, staged combustion LOX/LH2 engine is just too good not to use...
« Last Edit: 11/14/2010 06:53 pm by simonbp »

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Re: All-Cryo, Stage and a Half SLS
« Reply #61 on: 11/14/2010 07:11 pm »
The money saved by not having to maintain the SRB infrastructure and having CCDev handle ISS could pay for evolving the SSME into a tripropellant engine like the RD-701.
http://www.buran.ru/htm/rd-701.htm

The money saved by not having the SRB infrastructure to support will allow SLS to fly in the first place, with little left over for TAN, triprop, and/or other expensive and complex concepts.

If we didn't already have SSME, the motivation would be higher to do more engine development. But a high-thrust, high Isp, staged combustion LOX/LH2 engine is just too good not to use...

Kinda make me wish we could have back all the money wasted on CxP.

But then it just proves my theory right that any knee jerk type response in policy that is not reviewed as soon as people come back to their senses is usually more destructive over the long term then the event that provoked said response.

« Last Edit: 11/14/2010 07:17 pm by Patchouli »

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Re: All-Cryo, Stage and a Half SLS
« Reply #62 on: 11/14/2010 08:18 pm »
A fully-exploited TAN SSME could do 1.2Mlbf

Where on earth are you getting that number from?

If you used maximum 100% LH2/LOX TAN system (i.e. 100% additional propellant requirement for that engine, used for TAN), with LH2 you will only get a return of about 72% additional thrust.   Given that SSME produces 490,850lb Vac thrust  at 104.5% throttle, a 72% increase would result in 844,262lb Vac thrust, not 1.2 million lb Vac thrust.

You could potentially use RP-1 instead of LH2 (with additional tanking & plumbing) and push that percentage up to a maximum of 150%, but that results in only an 81% increase in thrust, which would be to 888,439lb Vac thrust -- still a long way shy of your claim.

And note that when you increase the thrust by 72% or 81%, yet increase propellant flow by 100% or 150% respectively, go examine what that does to your overall system Isp...   Lets just say "ouch".

TAN is a very useful invention, essentially an "afterburner" for a rocket engine, but TAN is no panacea.

If you want a new SSME to produce 1.2m lb thrust, TAN won't do it.   Period.   You're really talking about developing a brand-new engine.

Ross.
« Last Edit: 11/14/2010 08:25 pm by kraisee »
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Offline Lars_J

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Re: All-Cryo, Stage and a Half SLS
« Reply #63 on: 11/14/2010 10:36 pm »
The TAN hype from many is starting to sound like the aerospike hype of the early X-33 days. TAN will have its uses, but it does not cure cancer. :)

The RD-701 engine (brought up by another poster) is interesting - Was that just a fuel switching engine, or a TAN engine before the TAN term was coined? Of course it never flew, so who knows how close it was to production.
« Last Edit: 11/14/2010 10:39 pm by Lars_J »

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Re: All-Cryo, Stage and a Half SLS
« Reply #64 on: 11/14/2010 10:44 pm »
If the initial t/w ratio is 1.2 and you increase thrust by 70% does that not mean the t/w is  now 1.7 * 1.2, approx 2.00 ie gravity losses go from 5/6 to 1/2 and your effective isp has gone from 1/6 your unaugmented isp to 1/2 your augmented isp? So unless the augmented isp drops to a 1/3 of the unaugmented isp, AT LIFT OFF, this is a huge win? Or is this too simplistic?

Offline Patchouli

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Re: All-Cryo, Stage and a Half SLS
« Reply #65 on: 11/14/2010 11:19 pm »
The TAN hype from many is starting to sound like the aerospike hype of the early X-33 days. TAN will have its uses, but it does not cure cancer. :)

Just gravity losses and or the requirement for more stages.

Quote
The RD-701 engine (brought up by another poster) is interesting - Was that just a fuel switching engine, or a TAN engine before the TAN term was coined? Of course it never flew, so who knows how close it was to production.

I don't know the details but I sure would like to as it seems to be a very impressive piece of hardware but I suspect it's just has a second injector manifold for hydrocarbon fuel.
I supect it ran on three fuels then as the kerosene stored in the wings of the MAKS space plane was used up it cut the lox flow down and then ran as a pure hydrogen engine.
In a way the shuttle's use of SRBs is a crude implementation of tripropellant.

Offline kraisee

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Re: All-Cryo, Stage and a Half SLS
« Reply #66 on: 11/15/2010 12:01 am »
TAN will run with either fuel/oxidizer combination -- and it doesn't have to be the same one as the rest of the engine uses.

For example, you could theoretically have an LH2/LOX engine, fitted with an RP-1/LOX TAN system.   You just need is the appropriate tanking, plumbing, valves and pumps to handle the chosen combination.

Ross.
« Last Edit: 11/15/2010 12:02 am by kraisee »
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Offline simonbp

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Re: All-Cryo, Stage and a Half SLS
« Reply #67 on: 11/15/2010 12:49 am »
Except triprop that adds a whole extra set of engine hardware that could go wrong and which has ZERO flight heritage. In many ways it's worse than aerospike, in that it's two engines pretending to be one (rather than one really finicky aerospike engine).

Either way, that's the whole point of 1.5 staging. It allows you to get away with using existing engines but not SRBs. Anything else is going to be so expensive/complex that you might as well just use SRBs.
« Last Edit: 11/15/2010 12:52 am by simonbp »

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Re: All-Cryo, Stage and a Half SLS
« Reply #68 on: 11/15/2010 03:06 am »
A fully-exploited TAN SSME could do 1.2Mlbf

Where on earth are you getting that number from?

If you want a new SSME to produce 1.2m lb thrust, TAN won't do it.   Period.   You're really talking about developing a brand-new engine.

Ross.

I got that number from Jon Goff, who says that TAN can increase thrust by 100-300% depending on the design.  The 1.2Mlbf number is about 200% of the SSME sea-level thrust.  I said that this would require extensive modifications to the turbopumps and that's it's almost a completely new engine.

I was considering a biprop TAN with hydrogen (or hydrolox?) augmentation.  It's my understanding that cold gas hydrogen monoprop can have a vacuum Isp of 390s, so depending on the mixture ratios and pressure ratios, the augmented sea-level Isp might not be so bad, especially considering the substantial T/W advantage.

I'm not exactly clear on whether the main injector can be substantially oxidizer-rich at sea level to optimize hydrogen augmentation or if that would pose metallurgical difficulties...

But in any case I openly admit that I'm talking about an extensively redesigned engine rather than any trivial adaptation of the SSME.  The design could be heavily informed by SSME, RS-68, or perhaps even the Integrated Powerhead Demonstrator, but it's mostly a new engine.  Unless this has recently changed, I believe that NASA will be funded for advanced booster engine development, and this would surely fit the bill at least in my view.

If two such engines could replace six ordinary SSMEs (four of them jettisoned) in this booster concept, then this may be a cost-effective development path to pursue for block II or whatever.  That is, if there is sufficient demand for super-heavy launch vehicles...

Offline clongton

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Re: All-Cryo, Stage and a Half SLS
« Reply #69 on: 11/15/2010 12:05 pm »
If the initial t/w ratio is 1.2 and you increase thrust by 70% does that not mean the t/w is  now 1.7 * 1.2, approx 2.00 ie gravity losses go from 5/6 to 1/2 and your effective isp has gone from 1/6 your unaugmented isp to 1/2 your augmented isp? So unless the augmented isp drops to a 1/3 of the unaugmented isp, AT LIFT OFF, this is a huge win? Or is this too simplistic?

That's the wrong way to compute it. Don't adjust the initial T/W resulting figures by some factor because that will very quickly lead you down the yellow brick road. Instead recompute the actual ratio from the beginning by using all new inputs. It's simple enough to do. The correct T/W ratio is going to be the (total thrust of the engines) / (the total mass of the LV at T-0). The LV total mass is going to be the original LV mass plus the mass of the TAN propellants and the tankage and hardware required to support/contain those propellants.
« Last Edit: 11/15/2010 12:07 pm by clongton »
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Offline gin455res

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Re: All-Cryo, Stage and a Half SLS
« Reply #70 on: 11/15/2010 02:39 pm »
If the initial t/w ratio is 1.2 and you increase thrust by 70% does that not mean the t/w is  now 1.7 * 1.2, approx 2.00 ie gravity losses go from 5/6 to 1/2 and your effective isp has gone from 1/6 your unaugmented isp to 1/2 your augmented isp? So unless the augmented isp drops to a 1/3 of the unaugmented isp, AT LIFT OFF, this is a huge win? Or is this too simplistic?

That's the wrong way to compute it. Don't adjust the initial T/W resulting figures by some factor because that will very quickly lead you down the yellow brick road. Instead recompute the actual ratio from the beginning by using all new inputs. It's simple enough to do. The correct T/W ratio is going to be the (total thrust of the engines) / (the total mass of the LV at T-0). The LV total mass is going to be the original LV mass plus the mass of the TAN propellants and the tankage and hardware required to support/contain those propellants.


I was toying with adding this caveate(sp?), when I posted. But I think I sometimes suffer from sounding a little convoluted when I post. So I decided to keep it super simple.

The use of 'AT LIFT-OFF' was meant to signify that this was the instantaneous advantage you get for the initial dt, and was meant to be a starting point for not underestimating the effect I thought TAN probably had on gravity losses ( a little in the spirit of spherical cows, and no air resistance).

And I accept your point about TAN tankage mass, however, on the other hand, would you not also gain from reduced mass of the main propellant tankage and main propellant mass provided you switched off the TAN once the effective isp of the non-augmented state was higher than that of the augmented state? (Or is this cow dung reasoning, and precisely the yellow brick road you're alluding to?)

Again, as I stated early, I would be interested to see the equations for this argument as it's my layman's intuition (which may be totally wrong) that this is a very important period of the launch to optimise.

Anyone know of any online articles that address this issue?

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Re: All-Cryo, Stage and a Half SLS
« Reply #71 on: 11/15/2010 04:40 pm »
A fully-exploited TAN SSME could do 1.2Mlbf

Where on earth are you getting that number from?

If you used maximum 100% LH2/LOX TAN system (i.e. 100% additional propellant requirement for that engine, used for TAN), with LH2 you will only get a return of about 72% additional thrust.   Given that SSME produces 490,850lb Vac thrust  at 104.5% throttle, a 72% increase would result in 844,262lb Vac thrust, not 1.2 million lb Vac thrust.

You could potentially use RP-1 instead of LH2 (with additional tanking & plumbing) and push that percentage up to a maximum of 150%, but that results in only an 81% increase in thrust, which would be to 888,439lb Vac thrust -- still a long way shy of your claim.

And note that when you increase the thrust by 72% or 81%, yet increase propellant flow by 100% or 150% respectively, go examine what that does to your overall system Isp...   Lets just say "ouch".

TAN is a very useful invention, essentially an "afterburner" for a rocket engine, but TAN is no panacea.

If you want a new SSME to produce 1.2m lb thrust, TAN won't do it.   Period.   You're really talking about developing a brand-new engine.

Ross.

Um Ross...There's no magic limit for TAN of only a 100% mass increase.  The only hard limit is that you don't want to increase the back pressure inside the nozzle enough to unchoke the throat.  And you haven't even talked about options like increasing the expansion ratio of SSME now that you're dumping more propellants in.

No offense, but I don't think you fully understand the capabilities you can get out of TAN.  I'm not privy to everything either, not being an Aerojet employee.  But I've met with the inventors of the technology, exchanged many emails, and created some of my own models that match pretty well with what they're trying to do....

Sure a lot of the TAN amazing peoples out there also don't know what TAN's capabilities or limitations are.  But I think a lot of comments on here have been less-than-informed.

I'm pretty confident that taking SSME and turning it into a 1.2MLbf engine is perfectly achievable with TAN, especially if you go with the bigger expansion ratio that TAN really wants.  You'll get slightly worse SL Isp, but your vacuum Isp is better, your propellant mass fraction gets better, your max G's gets better, and your gravity losses go down.  etc.

That said, while I think TAN's a great idea--it's a better fit for RS-68.  More importantly it's not a great fit for this thread.  The all-cryo stage and a half design is actually pretty interesting in itself, without TAN.

~Jon

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Re: All-Cryo, Stage and a Half SLS
« Reply #72 on: 11/15/2010 06:45 pm »

I'm pretty confident that taking SSME and turning it into a 1.2MLbf engine is perfectly achievable with TAN, especially if you go with the bigger expansion ratio that TAN really wants.  You'll get slightly worse SL Isp, but your vacuum Isp is better, your propellant mass fraction gets better, your max G's gets better, and your gravity losses go down.  etc.

That said, while I think TAN's a great idea--it's a better fit for RS-68.  More importantly it's not a great fit for this thread.  The all-cryo stage and a half design is actually pretty interesting in itself, without TAN.

~Jon

I agree Jon
But what I have envisioned for TAN is actually a lengthen LOX tank and external RP-1 drop tanks. But I haven't spoken it here before because this thread is supposed to be all cryo, which RP-1 isn't. The increase in thrust is truly awesome and while the SL Isp does suffer, it is actually better in vacuum. Not to mention that isp isn't what one is looking for at liftoff – raw power is what you want and TAN will definitely give that to you – in spades.

As for your comment wrt RS-68 I think that depends on whether or not NASA is willing to expend the funds to develop a human rated engine from it or not. A HR RS-68 would be a different engine that what is flying now, with or without TAN and I'm not sure the USAF would go along with it. That's a big can of works that we cracked when we were doing DIRECT v2.0. The AF was *not* pleased with the suggestion.
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Offline kraisee

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Re: All-Cryo, Stage and a Half SLS
« Reply #73 on: 11/15/2010 06:53 pm »
No offense, but I don't think you fully understand the capabilities you can get out of TAN.

No offense taken Jon, none at all.   But with respect, I'm on an NDA with Aerojet regarding TAN.   I know a lot more about it than I am willing to talk about publicly, and my information simply doesn't align with yours.

Ross.
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Re: All-Cryo, Stage and a Half SLS
« Reply #74 on: 11/15/2010 07:24 pm »
No offense, but I don't think you fully understand the capabilities you can get out of TAN.

No offense taken Jon, none at all.   But with respect, I'm on an NDA with Aerojet regarding TAN.   I know a lot more about it than I am willing to talk about publicly, and my information simply doesn't align with yours.

Well...two could play on the "am on or was on an NDA with Aerojet regarding TAN" game...but I would think that the underlying physics of the technology, especially when you can independently get at it from first principles (and from publicly available information), shouldn't be an NDA issue. YMMV.

~Jon

Offline jongoff

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Re: All-Cryo, Stage and a Half SLS
« Reply #75 on: 11/15/2010 07:25 pm »
But while interesting, the whole TAN discussion probably belongs somewhere else.

Offline clongton

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Re: All-Cryo, Stage and a Half SLS
« Reply #76 on: 11/15/2010 08:01 pm »
But while interesting, the whole TAN discussion probably belongs somewhere else.

Maybe. But if the TAN propellants are cryogenic then it's not strictly OT, so long as it remains within the confines of this thread.
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Offline TrueBlueWitt

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Re: All-Cryo, Stage and a Half SLS
« Reply #77 on: 11/15/2010 08:04 pm »
No offense, but I don't think you fully understand the capabilities you can get out of TAN.

No offense taken Jon, none at all.   But with respect, I'm on an NDA with Aerojet regarding TAN.   I know a lot more about it than I am willing to talk about publicly, and my information simply doesn't align with yours.

Well...two could play on the "am on or was on an NDA with Aerojet regarding TAN" game...but I would think that the underlying physics of the technology, especially when you can independently get at it from first principles (and from publicly available information), shouldn't be an NDA issue. YMMV.

~Jon

I think you two are talking apples and oranges..  And both can and may be correct.

Ross's numbers seem to be for SSME with existing sized Nozzle.
And Jon seems to be talking SSME with a new larger expansion ratio Nozzle optimized for TAN.

Offline simonbp

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Re: All-Cryo, Stage and a Half SLS
« Reply #78 on: 11/15/2010 08:11 pm »
Maybe. But if the TAN propellants are cryogenic then it's not strictly OT, so long as it remains within the confines of this thread.

TAN is a sufficiently different concept that it deserves its own thread, if for no other reason than tidiness. Stage-and-a-half is a separate concept than that doesn't depend on TAN, and can achieve the congressional targets with SSME and RS-68B...

Offline clongton

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Re: All-Cryo, Stage and a Half SLS
« Reply #79 on: 11/15/2010 08:29 pm »
Maybe. But if the TAN propellants are cryogenic then it's not strictly OT, so long as it remains within the confines of this thread.

TAN is a sufficiently different concept that it deserves its own thread, if for no other reason than tidiness. Stage-and-a-half is a separate concept than that doesn't depend on TAN, and can achieve the congressional targets with SSME and RS-68B...

True, any TAN discussion should go to a different thread. I was just pointing out that if a TAN comment were made within the context of the thread that it would not be OT.
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Offline madscientist197

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Re: All-Cryo, Stage and a Half SLS
« Reply #80 on: 11/15/2010 08:53 pm »
No offense taken Jon, none at all.   But with respect, I'm on an NDA with Aerojet regarding TAN.   I know a lot more about it than I am willing to talk about publicly, and my information simply doesn't align with yours.

I guess you can't answer this, but several possibilities occur to me:
* Combustion stability issues with excessive TA (?)
* Issues with decreasing efficiency of TA not trading well against the extra mass, complexity and cost

My guess is that AJ has some empirical limits based on their previous testing as to where TA starts to become less worthwhile. That's not to say that it is necessarily a physical limit (as Jon Goff indicated with his first principles remark), it might be more of a practical limit with AJ's existing designs.
« Last Edit: 11/15/2010 08:54 pm by madscientist197 »
John

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