From: root@mauve.demon.co.uk   
      
   Josh Gigantino  wrote:   
   > Ian Stirling  wrote in message news:...   
   >> Josh Gigantino  wrote:   
   >> > Hello All,   
   >> >   
   >> > I'm trying to spec out a capsule-based launch system for some stories   
   >> > I've been writing. One of my goals with this project is to be as   
   >> > technically realistic as possible.   
   >>   
   >> Generally a good plan, when it doesn't utterly wreck the plot.   
   >> I'm assuming glaring errors are glaring errors just in case.   
   >   
   > Exactly! I'm striving to write the hardest science fiction ever.   
      
   Got some competition out there.   
      
   > I posted about using a toroid+skirt ballute to achieve some kind of   
   > lift and cross range. Do you have any ideas for achievable shapes with   
   > "controlled" ballutes or ways to make a capsule have a fairly gentle   
   > (3G max) reentry?   
      
   Why are you picking 3G?   
      
   A ballute has the problem that it's got to sustain really high   
   temperatures.   
   By the time you get to lower temperatures, reentry is over, and you   
   want something much larger to slow down the rest of the way.   
      
   I think I'd strongly consider deleting it.   
      
   Soyuz nominally gets around 4G.   
   Sheznou (sp?) the chinese variant of this claims to get a bit less   
   by using more lift.   
      
      
   >> If the paraglider is deployed at 10Km, this gives you some 30Km of   
   >> crossrange, which isn't great.   
   >> Especially if you'r coming down by ballute, you'd need the crew to   
   >> be able to survive at sea.   
   >   
   > Is 30km of crossrange enough to land in a pond (with several others   
   > downrange) when deorbitting using rocket thrust?   
      
   Probably, yes.   
      
   You'll want to add the capability to land on land, in case something   
   goes just a little bit wrong.   
   Ideally, you should be able to sustain the passengers for around   
   a week, landing on water, sea, or land.   
   Consider a navigation or life-support emergency that demands   
   immediate reentry.   
      
   >> A ballute can help somewhat, on a ballistic trajectory, by making the   
   >> decelleration happen in two halves, by effectively changing the sectional   
   >> density of the vehicle. (assuming that the ballute can survive).   
   >> On a lifting one, you jettison it as soon as you can.   
   >> A lifting trajectory can also give some crossrange.   
   >   
   > Can a Soyuz-type capsule perform a lifting trajectory, or do you mean   
      
   Yes.   
   It does in fact.   
   The AOA is altered so that it keeps high enough to slow down a bit   
   more gradually.   
      
   > a lifting body hull? I thought they skimmed the atmosphere at   
   > something around a 3 degree angle, slowly angling deeper in. The   
   > emergency ballistic descent that was experienced by the recent ISS   
   > crew was the direct 8G variety.   
      
   This was caused by the failure of the autopilot, so it reverted to   
   a ballistic trajectory.   
      
      
   > I've been planning on an axi-symetric blunt end design, with as many   
   > saftey features as possible for ensuring deorbit. Ideally it would be   
   > able to do an emergency deorbit without relying on the ballute (or   
   > paraglider) for survival.   
   >   
   > What would be realistic methods of making a capsule safe throughout   
   > flight, long lasting onorbit and fairly gentle on the way down?   
      
   What do you mean by long-lasting?   
   A day, or a week?   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)