Scotty - 13/1/2007 7:40 PMAbout the existing RS68 engine.Is or is not the following statement true?The hydrogen now enters the combustion chamber from the fuel injectors about 20 degrees R colder than originally predicted.This colder than expected hydrogen then negatively impacts the "C sub star" portion of the Isp equation.Thus the lower than expected Isp for the existing RS68 engine.A regenerative nozzel would add heat to the hydrogen, greatly improving the C sub star portion of the Isp equation.I totally agree an Isp of 450, as many have stated as possible with an evolved RS-68, is flatly impossible.But it sure looks like 430 to 435 is possible.
Scotty - 13/1/2007 8:34 PMThe basis for my statement is many long conversations with one of the fellows who did design work on the RS68's pumps and injectors.
SMetch - 13/1/2007 7:14 PMFirst Question:Did you run a 4xRS-68Regen, 4 Seg SRB under a 8.4 meter core with an optimized upper stage?Second Question:Your “Maximum” Tank numbers for a 8.4m “is” the current SSTS tank capacity. You could add about +60,000kg to tank by extending the LH2 tank down and LO2 tank up and still have room for the RS-68’s and Thrust structure.
JRThro - 13/1/2007 7:25 PMI'm not knowledgeable enough to ask an intelligent question, but I have to say that I appreciate Dr. Stanley's candor and his willingness to discuss DIRECT and the Ares program in this public forum.Well, I will ask a question about what Dr. Stanley said in the following text bite, about the Orion's ability to circularize the orbit, etc.:"Appropriate performance was transferred from Ares to Orion so that the spacecraft was not penalized. Performing multiple OMS types burns is commonplace on STS today and does not increase risk. Also, Orion does not have to do a burn to reach -30x100nmi - Ares places it in that orbit. Orion carries 1,000 ft/s to perform all orbital maneuvers, including transferring from -30X100 to 160 circ, and on to 220 for ISS, rendezvous, prox ops and docking, and deorbit."Dr. Stanley, does this mean that the Service Module engine, or the amount of fuel carried onboard the Orion, have been modified in order to transfer the needed performance to Orion? Can you expand somewhat on this point?Thank you for your time.-John Thro-Houston, TX
Scotty - 13/1/2007 8:34 PMThe basis for my statement is many long conversations with one of the fellows who did design work on the RS68's pumps and injectors.Until I (and he) see and review the analysis data (that I feel will never happen), I have to go with what he has shown me in dry hard math.
Generic Username - 13/1/2007 8:41 PMI know you said you diodn't want to get into costs, but I can't help myself. Recently there have been claims that the CLV first stage -1st stage, not whole vehicle - is going to cost $5billion to develop. How accurate, or inaccurate, is this number?
Doug Stanley - 13/1/2007 8:02 PMIf you are talking about just the development of the first stage...
that is significantly inaccurate!! Where did you get that number??
Doug Stanley - 13/1/2007 4:53 PM Despite assertions to the contrary the Direct core vehicle or the ESAS 24/25 core vehicles are almost completely new hardware developments with little STS ET heritage other than materials and diameter because of the different load paths. The development time was also found to be over 2 years longer (using detailed apples to apples schedules). The schedule driver now is actually the available budget...not technical considerations. NASA wanted to close the gap as quickly as possible and wanted a system to go to the ISS with high safety (the ESAS CLV is significantly higher LOC than a HLLV).