Quote from: gospacex on 08/20/2013 07:11 pmQuote from: newpylong on 08/20/2013 06:35 pmI don't think you're getting it. Just because 9 150K lb, extremely light, and very small engines can fit close together - does not mean that a similar amount of 300-500K lb thrust engines can be clustered like that. There are weight issues, heat issues, among others. 5.5 M is not enough. I don't see significant heat issues for regen cooled chambers and nozzles. It's not RS-68 F9 is 3.66 meter diameter.Merlin's nozzle is 1.676 m diameter.NK-33's nozzle is 2 m diameter (1.193 times wider than Merlin).If NK-33s are to be mounted exactly the same way as Merlins on F9 but with all dimensions scaled by 1.2, the stage needs to be about 4.4 meters in diameter for them to fit under it.Why do you think 5.5 m stage wouldn't be enough?If Aerojet proposes a 5.5m wide LRB for SLS that uses four AJ-1E6's, then that's 8 nozzles in 4 pairs. Dunno if 9 would fit, but 8 will have to fit unless Aerojet goes with only 3 engines for 6 nozzles.
Quote from: newpylong on 08/20/2013 06:35 pmI don't think you're getting it. Just because 9 150K lb, extremely light, and very small engines can fit close together - does not mean that a similar amount of 300-500K lb thrust engines can be clustered like that. There are weight issues, heat issues, among others. 5.5 M is not enough. I don't see significant heat issues for regen cooled chambers and nozzles. It's not RS-68 F9 is 3.66 meter diameter.Merlin's nozzle is 1.676 m diameter.NK-33's nozzle is 2 m diameter (1.193 times wider than Merlin).If NK-33s are to be mounted exactly the same way as Merlins on F9 but with all dimensions scaled by 1.2, the stage needs to be about 4.4 meters in diameter for them to fit under it.Why do you think 5.5 m stage wouldn't be enough?
I don't think you're getting it. Just because 9 150K lb, extremely light, and very small engines can fit close together - does not mean that a similar amount of 300-500K lb thrust engines can be clustered like that. There are weight issues, heat issues, among others. 5.5 M is not enough.
All very exciting.....but 5 nozzles might turn out a better design.
Quote from: Prober on 08/21/2013 01:46 pm All very exciting.....but 5 nozzles might turn out a better design.Assuming you mean five AJ-500's, that would only be 2500klbs of thrust, a full 1000klbs less than the 5-seg booster and Dynetics booster. There's an older spec sheet for SLS Block II with advanced liquid booster calling out three 1 Mlb " ORSC NHE"'s which I took to mean "Oxygen Rich Staged Combustion New Hydrocarbon Engines". So not sure if less thrust than that would work. So give AJ-500's might not be enough thrust. Even with the greater ISP, it still has to get off the pad with the NASA required minimum T/W ratio. That Block II also had the extra thrust of a 5th RS-25, so the booster might even need to be a little more thrust if SLS sticks with just four on the core in a Block 2B path.But that could be outdated information too, so not for sure...
So is that 3 engines per booster, and they have 1 or 2 chambers per engine?
Quote from: Lars_J on 09/02/2013 11:50 pmSo is that 3 engines per booster, and they have 1 or 2 chambers per engine?They say 2 x 550klbf chambers per engine. That's 3.3Mlbf per booster, with at least 297s of SL isp and 331s isp. That must give some amazing numbers.
Quote from: baldusi on 09/03/2013 02:06 amQuote from: Lars_J on 09/02/2013 11:50 pmSo is that 3 engines per booster, and they have 1 or 2 chambers per engine?They say 2 x 550klbf chambers per engine. That's 3.3Mlbf per booster, with at least 297s of SL isp and 331s isp. That must give some amazing numbers.2x "big, dumb, lower pressure" F1s vs 3x high-pressure "first time the US has done ORSC" engines. And 6x thrust chambers.I could see NASA coming back with "yeah, but do we want to use that on a launcher with astronauts?" NASA's LOM calculations (EG see full version of the ESAS appendixes) ratchet up pretty mercilessly as you add more engines, and those engines have worse failure modes.I wonder how 2x 1E6 would perform, just to try to keep the complexity down?cheers, Martin
Quote from: MP99 on 09/03/2013 07:12 amQuote from: baldusi on 09/03/2013 02:06 amQuote from: Lars_J on 09/02/2013 11:50 pmSo is that 3 engines per booster, and they have 1 or 2 chambers per engine?They say 2 x 550klbf chambers per engine. That's 3.3Mlbf per booster, with at least 297s of SL isp and 331s isp. That must give some amazing numbers.2x "big, dumb, lower pressure" F1s vs 3x high-pressure "first time the US has done ORSC" engines. And 6x thrust chambers.I could see NASA coming back with "yeah, but do we want to use that on a launcher with astronauts?" NASA's LOM calculations (EG see full version of the ESAS appendixes) ratchet up pretty mercilessly as you add more engines, and those engines have worse failure modes.I wonder how 2x 1E6 would perform, just to try to keep the complexity down?cheers, MartinI've seen those appendixes and I thought those were part of the thumbs in the scale of Griffin. If they keep applying those numbers, AJ should not even bother to present their bid. Which I find quite ridiculous since even a catastrophic TP failure (think of a Zenith-2 Tselina-2 #8 type of failure), wouldn't really be that different from other failure modes on the SLS stack. LOM and almost nil chances of LOC.Which is funny because when you let the commercial side chose a vehicle multiple chambered high pressure cycle or huge amount of engines doesn't seem to be a problem, apparently. In fact, the only GG cycle on the US fleet is not even considered.
Quote from: baldusi on 09/03/2013 02:06 amQuote from: Lars_J on 09/02/2013 11:50 pmSo is that 3 engines per booster, and they have 1 or 2 chambers per engine?They say 2 x 550klbf chambers per engine. That's 3.3Mlbf per booster, with at least 297s of SL isp and 331s isp. That must give some amazing numbers.Even with 600lbf less thrust than an F-1B LRB-powered SLS, the Isp jump is big enough the AJ-1-E6 LRBs ought to crush them in performance. I would bet, judging from the jump in SL Isp, that the performance jump might be 10% or more over their LRB competitor, depending on how big they make the LRBs. Alternatively they could make the LRBs shorter, but that seems like a waste. If you're going to offer the most complicated option and most advanced engine, I think it would pay to maximize performance to give yourself more of an edge.
Quote from: Hyperion5 on 09/03/2013 06:30 amQuote from: baldusi on 09/03/2013 02:06 amQuote from: Lars_J on 09/02/2013 11:50 pmSo is that 3 engines per booster, and they have 1 or 2 chambers per engine?They say 2 x 550klbf chambers per engine. That's 3.3Mlbf per booster, with at least 297s of SL isp and 331s isp. That must give some amazing numbers.Even with 600lbf less thrust than an F-1B LRB-powered SLS, the Isp jump is big enough the AJ-1-E6 LRBs ought to crush them in performance. I would bet, judging from the jump in SL Isp, that the performance jump might be 10% or more over their LRB competitor, depending on how big they make the LRBs. Alternatively they could make the LRBs shorter, but that seems like a waste. If you're going to offer the most complicated option and most advanced engine, I think it would pay to maximize performance to give yourself more of an edge. Well, if it has three engines, if there -was- a stand alone LV version of it (not saying there's a financial case for that), and if the AJ-1E6 could throttle down as low as the RD-180 (down to about 30% of maximum thrust...not sure if it can, but they are of fairly similar design, so maybe they can), then although they have limited fuel because they are an SLS booster and don't need a very long burn time, they could be throttled down shortly after lift off, and continue to be throttled down during ascent as applicable (to not pull too many g's, otherwise an overpowered booster like this would accelerate like crazy when not hauling up SLS's bulk). Which could mean those 3 AJ-1E6's could burn for quite a bit longer, and maybe get enough first stage performance to not need too big of an upper stage.
How much will the better impulse over the steel casing 5 segs effect performance? The 5 casings are 3.6 millions lbs/thrust - more than any advanced booster proposals I have seen.
Quote from: Lobo on 09/03/2013 06:07 pmQuote from: Hyperion5 on 09/03/2013 06:30 amQuote from: baldusi on 09/03/2013 02:06 amQuote from: Lars_J on 09/02/2013 11:50 pmSo is that 3 engines per booster, and they have 1 or 2 chambers per engine?They say 2 x 550klbf chambers per engine. That's 3.3Mlbf per booster, with at least 297s of SL isp and 331s isp. That must give some amazing numbers.Even with 600lbf less thrust than an F-1B LRB-powered SLS, the Isp jump is big enough the AJ-1-E6 LRBs ought to crush them in performance. I would bet, judging from the jump in SL Isp, that the performance jump might be 10% or more over their LRB competitor, depending on how big they make the LRBs. Alternatively they could make the LRBs shorter, but that seems like a waste. If you're going to offer the most complicated option and most advanced engine, I think it would pay to maximize performance to give yourself more of an edge. Well, if it has three engines, if there -was- a stand alone LV version of it (not saying there's a financial case for that), and if the AJ-1E6 could throttle down as low as the RD-180 (down to about 30% of maximum thrust...not sure if it can, but they are of fairly similar design, so maybe they can), then although they have limited fuel because they are an SLS booster and don't need a very long burn time, they could be throttled down shortly after lift off, and continue to be throttled down during ascent as applicable (to not pull too many g's, otherwise an overpowered booster like this would accelerate like crazy when not hauling up SLS's bulk). Which could mean those 3 AJ-1E6's could burn for quite a bit longer, and maybe get enough first stage performance to not need too big of an upper stage. I don't think we need to turn the SLS boosters into yet another LV. I think it would be enough to use the same engines as 2 other existing LVs (Atlas / Antares). Why split an already small volume of launches even further ?
Quote from: newpylong on 09/03/2013 06:13 pmHow much will the better impulse over the steel casing 5 segs effect performance? The 5 casings are 3.6 millions lbs/thrust - more than any advanced booster proposals I have seen.Thrust has very little bearing with performance. Specially when comparing solids vs liquids. First, you car about the whole stack T/W. And the compounded isp and propellant mass fraction.But just look at the proposals and the advanced solids proposal with 3.6Mlbf and composite casing and improved formula (excellent pmf and improved isp). And yet they can't quite reach 130tonnes without a 5th RS-25. Yet, the F-1B boosters have an expected performance of 150tonnes with 4 RS-25. And my guess is that AeroJet proposal will have even better performance.And the AJ-1E6 would solve the NK-33 stock problems and improve performance quite a bit on Antares. And could be a replacement on Atlas V if RD-180 was a problem. But considering that they've just extended the contract to 130 engines, unless the Russian bureaucrats do something really stupid, one SLS and Antares are real prospects.
However, I could even see a stronger case for a hydrolox booster powered by RS-68A...hypothetically. If SpaceX is able to start getting a piece of the government launch pie after 2015, then they may not need to pay ULA to maintain two EELV's. Since Delta IV is the LV which already has the 3-core heavy flying on both coasts, there's an argument that Atlas could be retired in favor of keeping Delta. SLS using a DCSS derived DUUS could lean in that direction too. So, ULA standardizes on just Delta IV with a 5m DCSS, perhaps upgrade to MB-60 on it. DUUS is DCSS derived with MB-60. SLS LRB's use boosters powered by 4-5 RS-68A's (2.86-3.6Mlbs at sea level respectively). Even with 5 RS-68's, that's one less nozzle than three AJ-1E6's.They seemed to think it was a feasible option in 2001 for an STS booster upgrade, and only 5.5m wide core. The MPS would probably have to be fatter though, but it can be because it won't need to fit through the VAB doors on the bottom.More Delta IV launches per year, and 10 more RS-68A's flying on every SLS launch would get that engine rate up, and as I understand, RS-68A is supposed to be pretty cheap at high volumes.And the US LV fleet is tightened up with hopefully some better economics of scale.
H2 is a horrendous fuel for a LEO booster. The tanks and the engines T/W is horrible. Look at the Delta IV LEO numbers. Specially the Medium. And the RS-68A is heavy even for an hydrogen engine. Plus, the ablative nozzle has very limited lifespan. But the main issue is that the boosters are volume limited. They can't be bigger than 5.5m, due to VAB size. So, you couldn't really put a booster much bigger than a Delta IV. You could put about 80% more propellant than a Delta IV core stage. And let's say that you add four engines (you can't fit more), that's 3Mlbf per booster. But you'd only have fuel for around 115s (back of the envelop calculation), that's even less than the SRB! I don't think you'd get much performance.
Now, if they had gone with an AJAX-like rocket, of course that the RS-68A boosters of the Heavy could have done wonders. With six cores I guess they'd had amazing performance. But that path was (regrettably) nor chosen.