Quote from: Will on 01/14/2009 01:20 amFor the Jupiter 232 design to close, the ultralightweight upper stage has to meet the ambitious goals set by the Direct team and their anonymous engineers.It doesn't get any more anonymous than Bernard Kutter, Manager of Advanced Programs at ULA - Lockheed-Martin publicly saying the JUS is verging on conservative, does it?I suppose that once you make up your mind about something, no amount of authority in the field will convince you otherwise. You wouldn't be forgetting this point that was brought up to you earlier otherwise. Sure, believe Steve Cook, he's an expert on cryo upper stages.
For the Jupiter 232 design to close, the ultralightweight upper stage has to meet the ambitious goals set by the Direct team and their anonymous engineers.
I have a question about the EDS.It will have been sitting in orbit for a while when LSAM / CEV comes to dock with it. Is there any possibility that it will be tumbling by this point?If so, how does the EDS stablise itself to allow docking to proceed? I don't see any thrusters in the EDS diagrams, nor any mass allocation (eg in figure 36 of http://www.launchcomplexmodels.com/Direct/documents/AIAA-2007-6231-LowRes.pdf).cheers, Martin
Well it's still very new news. Up until a couple of days ago I would have sided with Will on this one- I was very worried about the JUS numbers. So give him a chance to change his mind based on new evidence...
Quote from: MP99 on 01/14/2009 09:41 amI have a question about the EDS.It will have been sitting in orbit for a while when LSAM / CEV comes to dock with it. Is there any possibility that it will be tumbling by this point?If so, how does the EDS stablise itself to allow docking to proceed? I don't see any thrusters in the EDS diagrams, nor any mass allocation (eg in figure 36 of http://www.launchcomplexmodels.com/Direct/documents/AIAA-2007-6231-LowRes.pdf).cheers, MartinAFAIK there will be an RCS on the stage. It would be impossible to achieve a docking without it. The same will apply for the Ares EDS.
I'd have to go look it up to be certain, but I'm pretty sure J-2X uses a 5.5 : 1 mixture ratio.Ross.
Quote from: Lampyridae on 01/14/2009 05:50 amQuote from: Lee Jay on 01/14/2009 01:14 amQuote from: robertross on 01/14/2009 01:09 amLack of fuel destroys engines, which is why they run fuel rich.I thought they also ran fuel rich to reduce the average molecular weight of the exhaust, which increases ISP.Yes and no. Running stoichiometric (burn everything equally) means maximum energy is extracted from the chemical reaction. Running fuel or oxidiser rich means you are chucking more mass overboard for less chemical energy per unit mass... hence a lower collective exhaust velocity. However, it also means that the thermal energy is more efficiently distributed amongst molecules. It's easier to plunk thermal energy into H2 because it has one bond. H2O has 3 bonds so it gets squished out in the interactions. (Real rocket engineers please feel free to correct me wherever I foul up).I think you are wrong. Energy is not important, impulse (speed) is. Running LOX/LH non-stoichiometric gives you free H2 in the exhaust, which has highest possible speed of all gases at any given temperature. Thus, even though energy per kg of exhaust is not maximized, impulse (Isp) is.IIRC Isp-optimal ratio for LOX/LH is 4:1 by mass, IOW, to use twice as much hydrogen compared to stoichiometric (which would be 8:1). Due to LH tankage inefficiencies, in practice ratios close to 6:1 are used.
Quote from: Lee Jay on 01/14/2009 01:14 amQuote from: robertross on 01/14/2009 01:09 amLack of fuel destroys engines, which is why they run fuel rich.I thought they also ran fuel rich to reduce the average molecular weight of the exhaust, which increases ISP.Yes and no. Running stoichiometric (burn everything equally) means maximum energy is extracted from the chemical reaction. Running fuel or oxidiser rich means you are chucking more mass overboard for less chemical energy per unit mass... hence a lower collective exhaust velocity. However, it also means that the thermal energy is more efficiently distributed amongst molecules. It's easier to plunk thermal energy into H2 because it has one bond. H2O has 3 bonds so it gets squished out in the interactions. (Real rocket engineers please feel free to correct me wherever I foul up).
Quote from: robertross on 01/14/2009 01:09 amLack of fuel destroys engines, which is why they run fuel rich.I thought they also ran fuel rich to reduce the average molecular weight of the exhaust, which increases ISP.
Lack of fuel destroys engines, which is why they run fuel rich.
Discussed extensively in the old thread. But arguments for/against the feasibility of the Jupiter Upper Stage are as follows:For:- Less ambitious than ET mass fraction- LM Centaur engineer says it is possible, even conservative (see Popular Mechanics article) (this pretty much convinces me )Against:- more ambitious than SII, SIVB, or Ares-V EDS- NASA are squeezing more performance from Ares-V yet have not suggested such a high-performance upper stage as part of this- Steve Cooke says it isn't possible.
NASA Science News for January 14, 2009NASA's next great Moon rocket promises to do more than land astronauts on the Moon. In its spare time, it could revolutionize the science of astronomy.FULL STORY athttp://science.nasa.gov/headlines/y2009/14jan_rocketastronomy.htm?list77474
That's the Achilles' heel of the Direct proposal. Ares now has a three year head start, and the gap is widening every day. A two launch solution was a fairly attractive option three years ago. Now, changing horses in midstream is a lot more expensive.
For the Jupiter 232 design to close, the ultralightweight upper stage has to meet the ambitious goals set by the Direct team and their anonymous engineers. ... That's the Achilles' heel of the Direct proposal.
Lastly, to one of you guys who have all the numbers at your finger tips, could there be even a scaled down version of Jupiter 120 for launching Orion and the SM to the ISS?What I mean by that is could you actually forgo the SRB's for a core with 3 RS68's? Would they even produce enough thrust to get off the ground?
Just wondering, would it be possible to provide the image that is currently the background at directlauncher.com?Really great image.
[snip] It's easier to plunk thermal energy into H2 because it has one bond. H2O has 3 bonds so it gets squished out in the interactions.
I think we all just want to know why the tech used in the JUS isn't used in the Ares-V vehicle and if it was then what would the performance of the Ares-V be? NASA does consult with Boeing & Lockheed regularly so the tech cannot be unknown to them.
[...]The guys at NASA that claim the JUS doesn't work have NEVER successfully designed a cryo upper stage in their lives. [...]
Quote from: Will on 01/14/2009 01:20 amFor the Jupiter 232 design to close, the ultralightweight upper stage has to meet the ambitious goals set by the Direct team and their anonymous engineers. ... That's the Achilles' heel of the Direct proposal.Will, did you not read the PM article, specifically p57 4th and 5th paragraphs from the bottom?The engineering team that advised on the JUS design and analyzed the final product is not anonymous. Please stop saying they are. With ULA Lockheed-Martin permission, the manager of the Atlas Advanced Systems team, Barnard Kutter, has opened the window on their involvement. The man is among the most respected upper stage designers in the world! The Achilles heel no longer exists.
Quote from: clongton on 01/14/2009 12:30 pmQuote from: Will on 01/14/2009 01:20 amFor the Jupiter 232 design to close, the ultralightweight upper stage has to meet the ambitious goals set by the Direct team and their anonymous engineers. ... That's the Achilles' heel of the Direct proposal.Will, did you not read the PM article, specifically p57 4th and 5th paragraphs from the bottom?The engineering team that advised on the JUS design and analyzed the final product is not anonymous. Please stop saying they are. With ULA Lockheed-Martin permission, the manager of the Atlas Advanced Systems team, Barnard Kutter, has opened the window on their involvement. The man is among the most respected upper stage designers in the world! The Achilles heel no longer exists. Is Bernard Kutter willing to state on the record that the JUS design will not require pressurization during assembly, transport, stacking or rollout?
Quote from: Will on 01/14/2009 02:01 pmQuote from: clongton on 01/14/2009 12:30 pmQuote from: Will on 01/14/2009 01:20 amFor the Jupiter 232 design to close, the ultralightweight upper stage has to meet the ambitious goals set by the Direct team and their anonymous engineers. ... That's the Achilles' heel of the Direct proposal.Will, did you not read the PM article, specifically p57 4th and 5th paragraphs from the bottom?The engineering team that advised on the JUS design and analyzed the final product is not anonymous. Please stop saying they are. With ULA Lockheed-Martin permission, the manager of the Atlas Advanced Systems team, Barnard Kutter, has opened the window on their involvement. The man is among the most respected upper stage designers in the world! The Achilles heel no longer exists. Is Bernard Kutter willing to state on the record that the JUS design will not require pressurization during assembly, transport, stacking or rollout?What's the difference?
It has implications for ground processing. Pressure stabilization is an important ingredient of current and past Centaur stages. If he believes and will state that the JUS can achieve Centaur-like mass fraction without any use of pressure stabilization in ground handling, that's important information for a layman evaluating the practicality of the design.If he is assuming that there *will* be some use of pressurization, that's important information as well.