From: zenadsl6186@zen.co.uk   
      
   Andrew Nowicki wrote:   
      
   > David Summers wrote:   
      
   >> I think you are severely underestimating the problems you will have   
   >> with hypersonic flight and heating, but I don't really know of any good   
   >> references.   
   >   
   > A small rocket can be lifted above the   
   > dense part of the atmosphere with a balloon,   
   > so its shape does not have to be streamlined.   
   >   
   > A big rocket can be lifted above the dense   
   > part of the atmosphere with a big helicopter   
   > powered by hydrogen peroxide monopropellant.   
      
   The second stages are lifted enclosed inside the booster. "Bomb-bay" doors   
   open at 65 km, and seperation occurs at 80 km high. There are no aerodynamic   
   forces on the second stages on the way up.   
      
   The cargo stages do no re-enter: the people stages do, from orbit. I don't   
   think I am underestimating the difficulty of reentry. A rough mass budget   
   might look like this:   
      
   main engines, thrust structure                       1.5 tons   
   manoevering system, instruments and computers        0.6 tons   
   empty LOX tank                                       0.6 tons   
   2 crew, 15 passengers, hand baggage                  1.5 tons   
   seats, life support, safety gear                       2 tons *   
   cabin, thermal protection system                       2 tons *   
   wings, "tail"                                          1 tons *   
   wheels jets fuel                                     1.2 tons   
      
   spare                                                1.6 tons   
      
   total reentry mass                                  11.5 tons   
      
   items marked * are somewhat guesses, the rest should be reasonably accurate.   
      
   >> Powered landings (especially with wings) are very difficult because of   
   >> mass ratio requirements.  I think the real way to land a rocket is with   
   >> multiple fail-safe systems.  Personally, I think a rocket backed up by   
   >> a parachute (cannon deployed) is probably the best idea, considering   
   >> the mass ratio problems.   
   >   
   > I agree. Space shuttle solid rocket boosters   
   > have parachutes deployed by mortars.   
      
   They parachute into the sea. That's fine for things, but not for people.   
      
   When you seperate the missions - people and cargo - into two different types   
   of second stage, using a common first stage for economy, it makes a lot of   
   sense to use wings wheels and engines for people. The regulations, safety   
   expectations and record, technology and even the infrastructure are all in   
   place, and we can afford the mass.   
      
   For cargo it is probably better to use rockets and parachutes - as long as   
   you are not underneath them when they land!   
      
      
      
   --   
   Peter Fairbrother   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)