CFE - 10/5/2007 11:46 PMRegarding the issues of tank diameter and propellant load, I have to ask: are the tanks being milled thicker on the inner surface, as opposed to the outer surface? It seems to me that doing so (reducing the inner diameter) would lead to a small (but considerable) decrease in your propellant volume compared to the baseline ET. OTOH, if the inner diameter was kept constant and the outer skins were beefed up, it would force changes to the SRB attach struts in order to keep the pad footprint the same.
kraisee - 11/5/2007 9:50 AMJust to clarify, the engines are mounted in-line to keep maximum distance between them and the SRB's.While Chuck is correct that the center engine will not (probably) gimbal, it will actually still be an identical unit produced on the same production line as all the rest, only being a central engine, and will have the hardware allowing gimbal control, it simply isn't likely to be instructed to gimbal because the outboard engine pair offer greater control authority.As you point out, the interchangeable common cores can also be flown without the central engine in the smaller 120 configuration. The two outboard engines remain exactly where they are in either configuration. The electrical & plumbing connections to the central engine will simply be capped & closed out that way for such flights.Ross.
GncDude - 11/5/2007 12:10 PMQuotekraisee - 11/5/2007 9:50 AMJust to clarify, the engines are mounted in-line to keep maximum distance between them and the SRB's.While Chuck is correct that the center engine will not (probably) gimbal, it will actually still be an identical unit produced on the same production line as all the rest, only being a central engine, and will have the hardware allowing gimbal control, it simply isn't likely to be instructed to gimbal because the outboard engine pair offer greater control authority.As you point out, the interchangeable common cores can also be flown without the central engine in the smaller 120 configuration. The two outboard engines remain exactly where they are in either configuration. The electrical & plumbing connections to the central engine will simply be capped & closed out that way for such flights.Ross.A center engine has nearly the same control authority as the side engines for pitch and yaw. So, it adds you a nice extra margin if you want it, at the expense of having to develop two control algorithms for 2 vs. 3 engines. Actually scratch that, that's a negligible expense. You're better off by getting rid of all the gimbaling support, saving that weight.
clongton - 11/5/2007 12:20 PMQuoteGncDude - 11/5/2007 12:10 PMA center engine has nearly the same control authority as the side engines for pitch and yaw. So, it adds you a nice extra margin if you want it, at the expense of having to develop two control algorithms for 2 vs. 3 engines. Actually scratch that, that's a negligible expense. You're better off by getting rid of all the gimbaling support, saving that weight.From the point of view of commonality and interchangeability, we are better off leaving all three engines as identical. That makes everything easier. This launch vehicle has more than enough margin to allow the design to be simplified by commonality. That’s the beauty of fielding a launch vehicle that starts life with lots of margin vs. starting life already maxed out.
GncDude - 11/5/2007 12:10 PMA center engine has nearly the same control authority as the side engines for pitch and yaw. So, it adds you a nice extra margin if you want it, at the expense of having to develop two control algorithms for 2 vs. 3 engines. Actually scratch that, that's a negligible expense. You're better off by getting rid of all the gimbaling support, saving that weight.
veedriver22 - 11/5/2007 1:27 PMThat just makes it more complicated, more things to fail.
Lee Jay - 11/5/2007 1:33 PMWouldn't you want to gimbal the center engine in a side engine-out situation?
Ankle-bone12 - 10/5/2007 7:57 PMIm not a rocket scientist, in fact far from it, but I would assume that it could have something to do with the publics appeal to the flashy name of "Jupiter". It could also be viewed as a "next step up" from the Saturn family of rockets.
GncDude - 11/5/2007 2:26 PMQuoteLee Jay - 11/5/2007 1:33 PMWouldn't you want to gimbal the center engine in a side engine-out situation?Yes, but I think if this happens in DIRECT you lose the mission anyway. Right? I don't know if the 232's have engine out capability. Haven't looked.
zinfab - 11/5/2007 1:50 PMThanks for this update. I hope someone listens when it REALLY counts.
marsavian - 11/5/2007 12:03 PMQuotezinfab - 11/5/2007 1:50 PMThanks for this update. I hope someone listens when it REALLY counts.I think the Democrats will listen and if they win the Presidency they will probably install an Administrator to drop Ares I/V for DIRECT as it will allow them to beef up Science in Nasa whilst still keeping VSE going well even on a flat budget. I have reluctantly come round to Jim's way of thinking in believing that Griffin and Horowitz are so in bed with ATK they will persist with the current architecture come what may and they probably will return there to collect their rewards in 2008. This DIRECT proposal should be continued regardless to shine a light on the current architecture's failings for possible use when a different NASA power base is established.
marsavian - 11/5/2007 3:21 PMI think ATK want Ares I so they can use it commercially vs EELVs, that's the real reason I believe.