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.
So why not just make fully staged LV to begin with?
Quote from: Lars_J on 11/08/2010 06:21 amSo 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....
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?
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?
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 ratio3-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
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.
WRT RS-68 -- Base Heating will be a problem. Guaranteed.
Quote from: kraisee on 11/08/2010 07:07 pmWRT 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...
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...
Between the two I think the base heating issue with the RS-68A can be eliminated.
the question of "man-rating" and what that would cost (SSME neatly side-steps that issue).
Quote from: Patchouli on 11/08/2010 07:42 pmBetween 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.
The problem may be significantly easier to solve without the SRBs.
Thus isn't the RS-68 human-rating concern essentially political hog-wash?
Quote from: Patchouli on 11/08/2010 08:34 pmThe 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.
Quote from: kraisee on 11/08/2010 08:38 pmQuote from: Patchouli on 11/08/2010 08:34 pmThe 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
Quote from: simonbp on 11/08/2010 07:25 pmQuote from: kraisee on 11/08/2010 07:07 pmWRT 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.
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
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.
Quote from: simonbp on 11/08/2010 09:00 pmWhat 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.jpgThere'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.
Quote from: simonbp on 11/07/2010 05:23 amTo 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 tonnesMburnout = 53 tonnes[...]This all stands for some serious tweaking, of course.
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?
Quote from: edkyle99 on 11/07/2010 05:56 amQuote from: simonbp on 11/07/2010 05:23 amTo 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 tonnesMburnout = 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 = 57,365But 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.
Quote from: edkyle99 on 11/09/2010 10:08 pmDropping 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...
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?
Quote from: sdsds on 11/10/2010 04:53 amTowards 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. ...
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.
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.
Quote from: Jim on 11/10/2010 11:21 amJettisoning 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 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.
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.
Note a TAN SSME discussion at "Re: All-Liquid SDLV options"Quote from: Downix on 11/10/2010 08:38 pmJust 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!
For a 6xRL10A-4-3 upper stage, the breakdown is as followsStg 16xSSME (4xSSME Drop)T(s/l) = 1,134 tonnesISP = 363 sec (SL)/455 sec (vac)Mtotal = 755 tonnesMprop = 693 tonnesMbeforedrop = 260 tonnesMafterdrop = 244 tonnesMburnout = 53 tonnes...PLF = 5 tonnesPL = 70 tonnes
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...
Quote from: edkyle99 on 11/07/2010 05:56 amFor a 6xRL10A-4-3 upper stage, the breakdown is as followsStg 16xSSME (4xSSME Drop)T(s/l) = 1,134 tonnesISP = 363 sec (SL)/455 sec (vac)Mtotal = 755 tonnesMprop = 693 tonnesMbeforedrop = 260 tonnesMafterdrop = 244 tonnesMburnout = 53 tonnes...PLF = 5 tonnesPL = 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
Quote from: HappyMartian on 11/11/2010 12:58 pmNote a TAN SSME discussion at "Re: All-Liquid SDLV options"Quote from: Downix on 11/10/2010 08:38 pmJust 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
Quote from: Patchouli on 11/14/2010 06:45 pmThe 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.htmThe 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...
A fully-exploited TAN SSME could do 1.2Mlbf
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.
Quote from: butters on 11/14/2010 04:27 amA fully-exploited TAN SSME could do 1.2MlbfWhere 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.
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?
Quote from: gin455res on 11/14/2010 10:44 pmIf 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.
Quote from: butters on 11/14/2010 04:27 amA fully-exploited TAN SSME could do 1.2MlbfWhere 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.
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
No offense, but I don't think you fully understand the capabilities you can get out of TAN.
Quote from: jongoff on 11/15/2010 04:40 pmNo 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.
But while interesting, the whole TAN discussion probably belongs somewhere else.
Quote from: kraisee on 11/15/2010 06:53 pmQuote from: jongoff on 11/15/2010 04:40 pmNo 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
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.
Quote from: clongton on 11/15/2010 08:01 pmMaybe. 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...
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.