From: johnhare@tampabay.rr.com   
      
   "Henry Spencer"  wrote in message   
   news:Hs2ps1.CIG@spsystems.net...   
   > In article <58866faa.0401250836.4e153886@posting.google.com>,   
   > Zoltan Szakaly  wrote:   
   > >But there is a region between standstill and about mach 6 where air   
   > >breathing propulsion is very attractive. Simple calculations show that   
   > >you can achieve a factor of 10 savings in fuel consumption if you use   
   > >ramjet like engines.   
   >   
   > Unfortunately, that's much more attractive for cruising missions than for   
   > accelerating ones, because the price is much heavier engines.  Even at   
   > modest altitudes, the oxygen content of air is *four orders of magnitude*   
   > less, per unit volume, than that of LOX.  So you inevitably need big heavy   
   > machinery to handle air.   
      
   What is the maximum possible T/W you see from a turbine based   
   air breathing engine. How inevitable is the question. Do you see   
   a fundamental T/W limit at 100, 40, 15, or some other number?   
      
   At what T/W do air breathing engines become performance   
   competative with the lower stage rocket thrust they replace?   
   Competative does not necessarily mean desirable in this case,   
   just not a penalty.   
      
   During a previous discussion I accepted that 120/M seemed to   
   be a reasonable break even for an air breather that supplies all   
   the acceleration  from the ground. I suggested a few weeks ago   
   that for a VTVL SSTO, 28 to 43 might be a reasonable requirement   
   for units designed for the landing mass only, not operating supersonic at   
   all during launch phase. Would you agree with these requirements   
   for break even performance? How much better would they have to   
   get to be desirable as opposed to break even?   
      
   What is the performance requirement for an ICH tee shirt?  :-)   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)