From: nuny@bid.nes   
      
   On Thursday, July 21, 2016 at 3:45:31 PM UTC-7, MrAnderson wrote:   
   > The hammerhead design is interesting design, I will try this in my schemes (I   
   > make simple spaceship drawings by pencil, I will upload them on the   
   > deviantart in two weeks or so). In my current designs propulsion bus is   
   > cylindrical, with circular shield on top.   
      
     Damn. I forgot the interstellar dust shield. But I think a cone, rather than   
   a cylinder.   
      
     Something never mentioned about waterskiing starships- the exhaust plumes   
   will expand with distance from the engine. Most of the radiation hazard is   
   pions and whatnot that decay fairly quickly but the exhaust plasma is still   
   hot as hell and the engines    
   are basically great big X-ray floodlights. Putting the engines farther out on   
   booms as in a hammerhead or ring, creates a hollow conical "safe" volume that   
   narrows to a point where the plumes from all of the engines merge. The crew   
   module has to be at    
   but not outside the tip of that cone. I can't quite figure out how to   
   determine the cooling rate but a kilometer or two seems about right. You   
   definitely don't want to be in direct view of that X-ray glare even kilometers   
   away.   
       
   > About nanotubes and coating, you are right, I completely forgot about   
   > stretching. With these cables and stuff like that, I don't feel competent to   
   > say anything, I just don't know anything about them :D   
   > Need more studying.    
      
     I have an engineering background and a taste for failure analysis. I'm   
   always looking for ways that things might fail, hopefully *before* they fail.   
      
     I also try to keep reminding myself that there are no truly rigid materials,   
   and that *anything* will stretch, compress, and or bend *especially* when you   
   really didn't want it to.   
      
   > And yeah, it will be just like hard sf Hyperdrive Ring from Star Wars. This   
   > gives me idea, why not try with making propulsion bus a ring? I don't see   
   > real advantages for that, but the look can be nice :p   
      
     Hmm... not a bad idea at all.   
      
     A ring is the "figure of revolution" of a hammerhead rotated around the   
   thrust axis. With a literal hammerhead you'd have two thrusters affording   
   steering in one plane by way of differential thrust, and two more at right   
   angles in an X would give you    
   steering in three dimensions. More thrusters distributed on a ring does the   
   same, of course. It's more expensive to make several smaller engines than a   
   few large ones for a given total thrust but you also gain redundancy- you can   
   tolerate more individual    
   engine failures without mission failure.   
      
   > I'm starting to not understand how do you want spaceship to look, engine   
   > module with truss and warship attached and habitat for interstellar flight on   
   > cable? Let me know if I get it right. The railgun, or PBW could be nice, but   
   > I must understand where do you want to put this truss.   
      
     Hey, it's your ship- I'm just exploring options. The two examples you gave   
   weren't (overtly) warships so some adjustments are necessary. ;>)   
      
     Cables *and* a truss I hadn't considered...   
      
     Okay.  How about three main sections; the drive, the spine, and the towed   
   crew module. The whole ship tapers from the shield to the towed module.   
      
     The drive section is a stubby cylinder or a frustum of a cone, wide end   
   forward, with the exhausts jutting out of the cone. As you say, the bow of the   
   drive section is a round, thick shield of compacted dust and rubble mined out   
   of asteroids or    
   whatever as usual, sintered to keep it from crumbling. Right behind the shield   
   are the engines and the fuel tankage, pumps, and whatnot between them that   
   needs to be near the engines. (I'd want to keep fuel lines as short as   
   possible (fewer feet of pipe    
   means fewer places for failures).   
      
     The heat radiators (part of the drive module) of the Valkyrie stick out past   
   the dust shield. I don't like that because they're subject to erosion. I   
   prefer the "fountain" technique described elsewhere on the site- the liquid   
   metal coolant is sprayed    
   out of one or more nozzles that stick out of the dust shield in the direction   
   of travel, and "falls" back as it cools to the shield where it's collected for   
   filtering and reuse. The shield will therefore need to have bowl-shaped   
   depressions with drains    
   that lead to the filters. That way the spray provides shielding too. You won't   
   be changing course while it's running, naturally.   
      
     (Once the ship has decelerated to combat velocity the drive section would   
   separate from the rest and go find a gas giant to refuel from probably by   
   hovering at the cloud-top level and lowering a hose to suck up gases, and then   
   into solar orbit to    
   convert some of the mined gas into antimatter. The remaining part will need   
   some, but not much, built-in delta vee and maneuvering capacity. After all   
   it's not going to have to maneuver much. The drive section won't need much in   
   the way of armament    
   because nobody's going to bother attacking something designed to absorb the   
   equivalent of many megaton bombs per hour.)   
      
     "Below" the tankage is the attachment point to the main truss, a large   
   hollow lattice with the Big Gun (railgun, coilgun, whatever) running its full   
   length. Also running its length are power and data lines, elevators, and   
   assorted plumbing. On the    
   outside of the truss are cradles for the combat craft, enclosed workspaces for   
   maintenance and repair, heavily-armored magazine containers for missiles and   
   such for rearming the combat craft, point defense turrets, and whatever kinds   
   of reactors are    
   sensible to power the ship during combat operations while the drive section is   
   away. Thrusters for delta vee and RCS clusters at both ends.   
      
     The habitat will be at the extreme aft, including human consumables (air,   
   food and water and such) storage, recycling and other life support machinery,   
   and whatnot. I think you're assuming some kind of suspended animation so the   
   soldiers aren't    
   pensioners at arrival? That means all of that support machinery has to be   
   nearby as well. I assume such a ship must have an awake skeleton flight crew   
   while in flight, probably rotated out of hibernation for a few months or so   
   per "shift". Assuming the    
   hibernation gear provides additional radiation protection, the "freezer" can   
   be located closer to the engines than the awake crew module. Actually it would   
   probably make sense to attach the freezer to the aft end of the truss   
   permanently and only the    
   control module with the awake crew would be out on cables.   
      
      
   [continued in next message]   
      
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