From: nuny@bid.nes   
      
   On Friday, March 31, 2017 at 3:03:46 PM UTC-7, MrAnderson wrote:   
   > Welcome to discussion Els! (is that's what I can call you?;)   
   > In the later part of discussion, we lowered the mass of projectile to 10 kg   
   > with speed at 50 km/s. What do you think, would that be more feasible? As for   
   > the Russian test, we don't know how exactly was the launcher built, what   
   > caused the coil to blow up. Maybe strong bracing would prevent that? As for   
   > energy storage, keep in mind it's future (or more accurately, completely   
   > diferrent world as you may have deduced from my other posts on the group), so   
   > some technological advance could get capacitors to more than this 20 kw/kg   
   and   
   > 33%. Also, how effective could the flywheels be here? Or how could room   
   > temperature superconductors affect capacitor and coil technology?   
   > For now, I am in a designing phase for the ship, and, the coilgun barrel is   
   > around 25 meter long. This coupled with 50 km/s and 10 kg's seem to be a bit   
   > too impossible huh? Anyway, it's still a design phase.   
      
     First, about the Russian coilgun blowing itself up.   
      
     Coils don't like to carry really high current bursts for two reasons-   
   heating, and the mechanical stress. Heat can be handwaved away with liquid   
   (pick a gas) cooling, but the mechanical stress is the hard part. Basically,   
   run a bunch of current through    
   a coil and the magnetic field tries to uncoil it and straighten it out. That's   
   the basic principle of railguns- the slug is a short across the rails making a   
   single-turn coil out of it. Apply current and the rails try to push themselves   
   apart but they're    
   braced so they can't move- the only part that can move is the slug. Same with   
   a coilgun- the harder you want to throw the projectile the more the coil wants   
   to destroy itself.   
      
     You can brace the hell out of it but it's still going to deform after a   
   while, so it will need to be swapped out. That's not a deal-breaker because   
   existing gun barrels have a lifetime measured in seconds, each millisecond or   
   so firing adding up over    
   the gun's useful lifetime. So, really fat coils with heavy bracing means a   
   massive gun.   
      
     Another option is to design it so that it destroys itself with each shot and   
   is replaced for the next shot. That means each slug comes with its own   
   sacrificial coil wrapped around it that makes contact with the power supply   
   when it's loaded and the    
   coil is allowed to fragment, or better vaporize, when the gun is fired, and   
   subsequent non-sacrificial coils embedded in the "barrel" accelerate it   
   further. Or just make the coil longer and don't pulse it as hard with more   
   coils farther down the barrel    
   so none of them are stressed beyond their ability to survive.   
      
     Now, about power storage. Technomagic supercapacitors are an option (you can   
   talk about the "old-fashioned" graphene or whatever real-world gee-whiz tech   
   that the Ardans abandoned long ago).   
      
     There's this thing called a compulsator which is basically a low-mass   
   high-strength flywheel designed for 30k (thirty thousand!) rpms with   
   alternator windings that's spun up by acting like an ordinary induction motor,   
   then all the energy stored in it    
   is dumped rapidly. It's still the storage solution of choice for the Navy's   
   railguns. Current designs aren't superconducting but there's no obvious reason   
   they couldn't be. Hard to find efficiency info on it but Google for it.   
      
     Anyway, 25 meters long sounds a lot more reasonable, but again it ain't   
   gonna slew quickly. A 10 kg slug doing 50 kps carries what, 12 GJ (if I didn't   
   drop a decimal point) which sounds adequately destructive. That amount of   
   energy is also a lot less    
   impossible to generate, store and deliver rapidly.   
      
   > Okay, now more to Mr Fergerson.    
   > I am drawing the ship, it has 600 m long and around 700 m with some fancy   
   > looking antennae/sensor/whatever on front (I am probably gonna change this   
   > part of project). Shape from the back to front: a 100 m diameter cylinder   
   that   
   > is like 170 m long, that's the engine + fuel and big part of propellant;   
      
     Plus armor for interstellar dust and other crap during ferry phase, right?   
   Remember that stuff will erode the shit out of your antennas and sensors.   
   Expect to carry several replacements. Or, tuck them in for most of the long   
   trip and only deploy them    
   after decelerating into the target system where they won't get torn up.   
      
   > then a smaller and much shorter cylinder, that's the reactor and next batch   
   of   
   > propellant;   
      
     Coolant pumps, dedicated engine control computers, stuff like that...   
      
   > then the "weapon ring" octagonal 100 m wide section with 2 edges with coilgun   
   > turrets, 2 with PBWs   
      
     What are the particle beams for? I mean, what kinds of target are they   
   intended to damage/destroy that the other weaponry can't handle?   
      
   > and 4 with lasers; then we reach 300 meters of the ship,   
      
     So all of this is left away from the expected battle zone, and it's armed   
   simply for self-defense so the actual battleship has something to come back   
   to, right?   
      
   > and then starts the   
   > "brick", 100 m tall and 50 m wide, divided into hangars, cargo bays, crew   
   > quarters,   
      
     Have you decided if the crew will be awake for the whole trip or will they   
   be in cold or warm sleep until it's time to fight? If they're awake the   
   life-support resources go up dramatically.   
      
   > and propellant tanks. On frontal part the steer and portside walls,   
      
     "Ster and portside"? Port and starboard?   
      
   > there are next two coilgun turrets. Also in these walls are missile silos   
   with   
   > missile magazines and armor covers. On the thrust axis, there is an option to   
   > mount a spinal coilgun, that could launch quite big projectiles, like these    
   > 100 kg's ones. It's "caliber" is around 2 meters.   
      
     Hm. Optional giant spinal gun. If the High Command doesn't think it will be   
   needed for a given mission because there are no targets in a given upcoming   
   battle for it to hit, what other optional weapons or systems might fit into   
   that slot? Fighter    
   launcher?   
      
   > When it will be near completing, I will post it on Flickr, for now it's a   
   > rough draft in A4 sketchbook.   
      
     Cool. I'll be waiting.   
      
      
     Mark L. Fergerson   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)