From: zenadsl6186@zen.co.uk   
      
   David Summers wrote:   
      
      
   > 1. What happens if the "bombbay" doors fail, and the passenger ship   
   > can't detach?  LOV?   
      
   Nope. Nothing exciting happens at all.   
      
   The booster reenters heavy. Whether the doors are closed or not doesn't   
   matter much for reentry [156a], and like some but not all real bombers doors   
   they are designed for subsonic aerodynamic flight and landing even if they   
   get stuck open.   
      
   Procedure after reentry in that case is to loiter on jets, trying first to   
   dump the contents of the second stage LOX tank, and if they can do that they   
   try and dump the second stage LH2 - but if needed they can land heavy while   
   both are still filled.   
      
   Landing heavy isn't that serious, the booster is designed for it; but even   
   so it may not be necessary. The empty booster weighs 100 tons, and the   
   normal landing weight is up to 120 tons (the extra is 20 tons of go-around   
   and loiter fuel, which they can dump if needed). The fuelled second stage   
   weighs 60 tons, so even at 180 tons landing weight it's not that different   
   to landing normally, and if they dump the second stage LOX tank contents and   
   the go-around fuel then landing is at close to the normal weight of 120   
   tons.   
      
      
   [156a] The doors are on top, and the second stage is cradled in mechanically   
   strong foam cryogenic insulation (which is attached to the booster, not to   
   the second stage), so it won't matter during reentry or landing if eg the   
   locking clamps have failed, the second stage won't fall out or thrash about.   
      
   A half ejected people carrier second stage could be a flight and/or landing   
   problem. If so, the procedure depends on which end is out, and whether the   
   bulky LH2 tank can be jettisoned.   
      
   If the tank end is out and it can be jettisoned safely then the booster just   
   jettisons, flies back and lands slowly and carefully. I have some ideas   
   about what to do if it can't, but the design isn't that far advanced (ie, it   
   depends ... but even allowing the filled LH2 tank to break up and burn need   
   not be catastrophic, the surfaces to be protected are already re-entry   
   capable, and there should be no 500 mph impacts if it's done right).   
      
   If the capsule orbiter end is out, then it just seperates and lands   
   seperately. The booster pilots may or may not try and land the booster,   
   depending on the position of the tank.   
      
   > 2. What happens is something "goes wrong" during first stage boost?   
   > With the second stage internal, wouldn't that mean LOV?   
      
   The first stage is a modified  piloted jet airliner (it could even start   
   life as an actual 747) with rockets added. It flies to 30,000 feet on jet   
   engines, then ignites it's rockets. If the rockets fail in a   
   non-catastrophic way (or even in most ways normally considered catastrophic:   
   the engines and fuel tanks are physically isolated by distance and by   
   structures, so most even catastrophic engine failures won't involve the fuel   
   tanks and end with LOV) it just flies back and lands.   
      
   It has 20 tons of jet fuel at rocket ignition, and 80 tons of RP-1 rocket   
   kerosene which it can use as jet fuel if the rocket engines simply fail eg   
   to ignite, so it can loiter for several hours while dumping lox etc..   
      
   If the first stage can't land safely the second stage can discard it's LH2   
   tank, dump it's LOX, seperate and land (at the moment the second stage LOX   
   tank is in the reentry vehicle, and the LH2 tank is seperate, but I may   
   change that, the lander is getting a bit too fluffy for aerodynamic flight   
   in difficult weather, though it's fine for reentry either way). The booster   
   pilots can then fly to a safe crash site and parachute out.   
      
      
   BTW If the second stage rockets fail after seperation, they dump the LH2   
   tank and contents, reenter, dump the LOX while loitering on jets, and land.   
   If they aren't near a major runway it doesn't matter too much, as a few 100m   
   of road or even a large field will do, and they have 20+ minutes of loiter   
   time - at the moment landing speed is too slow, I should make it faster,   
   hence the possible LOX tank repositioning to make the lander less fluffy.   
      
      
      
      
   As far as I can tell the main non-airliner-type LOV scenarios are a   
   particularly bad catastrophic failure of the rocket engines, or a reentry   
   failure. The first would have to be very bad as the vehicle is designed to   
   survive most types of catastrophic engine failure.   
      
   Reentry failure should be minimisable by good and simple design - the people   
   carrier presents as a capsule on reentry, which is about the simplest and   
   most rugged reentry shape I can think of. Everything that reenters is doubly   
   protected against reentry, once reuseably, and once single-shot-ablative if   
   the reuseable system fails (see my recent "inferno" post for some details).   
      
   The booster pilot's life is still slightly more dangerous than the second   
   stage pilot's/passenger's (and less glamourous (sp!?) too) tho  :(   
      
   but only slightly. And we give him a parachute.   
      
      
   --   
   Peter Fairbrother   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)