From: egruf_usenet@cox.net   
      
   On Tue, 05 Apr 2005 13:04:57 GMT, in sci.space.tech Craig Fink   
    wrote:   
      
   >Another example of Military vs Civilian requirements differences would be   
   >the recent Scramjet test. Someone at NASA allowed the Military to drive   
   >the requirements, probably claiming some sort of "Dual Use" requirement.   
   >But, to me, it looked more like the design point was a "Military"   
   >requirement, not a "Civilian" requirement. This Scramjet was operating at   
   >a dynamic pressure of over 1000 psf. That's a really high equivalent   
   >velocity Ve, that no sane person would really want to fly commercially at.   
   >Not a nice environment, high loads, high temperatures. It's probably   
   >better to describe it as a missile engine test, not a civilian passenger   
   >aircraft engine test.   
   >   
   >A scramjet test driven by "Civilian" requirements would have looked much   
   >different. It would have been flown higher at a much lower dynamic   
   >pressure (or equivalent velocity). Since the atmospheric density is lower,   
   >it probably would have had larger lifting surfaces, and the engine might   
   >have been quite a bit bigger. Totally "Civilian" requirements most likely   
   >would have concluded that the economics of such an aircraft were not even   
   >viable for sustained atmospheric flight in this region. That the scramjet   
   >test is really and acceleration mission, not sustained flight. So, a   
   >"Civilian" design point driven by "Civilian" requirement would have been   
   >much different. It would have been flown much higher, at a much lower   
   >dynamic pressure, with more emphasis on acceleration rather than sustained   
   >flight.   
      
    I believe you need to look at how one designs and operates a scramjet   
   before you make such statements. 1000psf trajectories are on the low end,   
   but are required to have sufficient pressure at the combustor entrance   
   without excessively high inlet internal contraction ratios.  One can easily   
   find a requirement in the open literature for a half an atm at the   
   combustor entrance. What inlet design do you propose to achieve this at   
   your proposed alt? The acceleration requirement is driven by the access to   
   space reqmt to get this technology funded within NASA.   
   ----------   
   Ed Ruf    Lifetime AMA# 344007 (Usenet@EdwardG.Ruf.com)   
   http://EdwardGRuf.com   
      
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