XPost: misc.misc   
   From: bondage@frontiernet.net   
      
   Kent Paul Dolan wrote:   
   >   
   > I'm guessing this has been discussed before, but   
   > with the new initiatives on solar sails and ion   
   > propulsion drives, humor me anyway.   
      
      
      At least once that I remember. I've seen such a notion in the letters   
   page of Aviation Week earlier this year, too.   
      
      
   > As opposed to trying to orbit and proof an entire   
   > new Mars mission from scratch, what would be the   
   > benefits and disbenefits of adding stuff to the ISS,   
      
      Testing and qualifying all that 'stuff...'   
      
   > dragging it all off to Mars using a continuous   
   > propulsion system of one sort or other   
      
      
      Reaching escape velocity with low-thrust engines means spiraling   
   slowly out from LEO, spending way too much time in the VanAllen belts.   
   Higher thrust departures cut across them more quickly and directly.   
      
      
   > (or perhaps   
   > several), and using it like the lunar orbiter as a   
   > staging base to and from the Mars surface?   
   >   
   > The main advantages I can see is that it is already a   
   > known-to-be-functional long time habitat for humans,   
   > and that it is a huge amount of mass already much of   
   > the way out of the gravity Earth's well.   
      
      
      There's mass, and there's mass. The fact that it's not suited to such   
   use more than counterbalances the fact that it's already in LEO.   
      
      
   > But, is it strong enough to survive being shoved?   
      
      
      Nope. If you *had* a high-thrust propulsion system (say a solid-core,   
   nuclear thermal rocket), pushing that hard on any part of it, it would   
   break apart modules, and tear off solar arrays (Which would be   
   delivering reduced power out toward Mars, even if you somehow got away   
   with it.)   
      
      
   > Is it reliable enough not to need the possibility of   
   > a quick rescue everytime someone miscalculates the   
   > inhabitant's appetites?   
      
      
      Probably not. The assumption of relatively frequent re-supply is part   
   of the design. Certainly thermal control is. It was also built on the   
   assumption that it would spend almost half of its time in Earth's   
   shadow. On the way to Mars, you're in full Sun for months. (Not   
   insurmountable as Apollo proves, but ISS just doesn't have it.)   
      
      Then there are the Solar radiation issues that the original engineers   
   wern't planning on, once you leave the magnetosphere....   
      
      
   > Consider also building up from the present   
   > capability to include such needed stuff as   
   > self-sufficient hydroponics and full waste   
   > recycling, with a long term _intention_ of shoving   
   > the whole mess, once it can serve, as a planet to   
   > planet "wanderer" (pun very much intended).   
      
      
      Better off building something like that properly, from the start.   
   (Which is not to say that some of that technology can't be *tested* on   
   ISS.)   
      
      
   > Mars need not be the final destination, either, it   
   > could just be a staging and fuel / propulsive mass   
   > replenishing waystation to Europa or Titan, say, or   
   > a dropoff point for one research staff of several,   
   > with eventual pickup and return intended for all.   
      
      
       Cool. But not with ISS.   
      
       If you had *really* high-performance propulsion (say, a *gas* core   
   NTR), a slightly better argument could've been made for modifying Skylab   
   for a Mars-orbit mission and return. You could perform it inside the   
   known single-mission times, and it was designed for high thrusting on   
   its long axis. (A necessity, to have been launched on a Saturn 5.)   
      
      But those power issues don't go away. Even Skylab had a folded solar   
   array come off at launch. Once deployed, it was as fragile as ISS. You'd   
   need some small nuclear power source (Could the engine be tapped? It was   
   proposed for solid NTRs.) to replace that, too.   
      
      
   --   
      
      You know what to remove, to reply....   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)