From: nuny@bid.nes   
      
   On Monday, August 8, 2016 at 2:50:42 PM UTC-7, MrAnderson wrote:   
   > I will just come back when I figure this quoting out :))))   
   > I don't even know what thunderbird is.   
      
     It's an e-mail, newsreader, and messaging program that runs in Windows, OS   
   X, and Linux.   
      
     I occasionally use T-bird but mostly just use the Google Groups HTML   
   interface on my laptop (Firefox, Win10) these days because lazy. Are you   
   posting from a phone or something?   
       
   > So, I will do stuff like that    
   >    
   > "I just put my cursor where I want to type something and hit "enter" three   
   > times to make space."   
   >    
   > Hope this looks good.   
      
     Works for me.   
      
   > "If it will help at all I'll upload it to Google Photos."   
   >    
   > Great idea, this would help a lot, post a link too. ;)    
      
     Okay, I'll try to find time. Like I said, it's ugly. I do much better with   
   pencil on paper.   
      
   > "Also the ship will be continuously moving *into* that exhaust plume but I'd   
   > guess (hope) that it would have cooled to the not-dangerous point by then."   
   >    
   > But isn't the exhaust moving at great speed away from our ship? I mean when   
   > it brakes, the plume moves at 0.7c or so relatively to the spaceship, so it   
   > can't "go back".   
      
     Yeah, once it gets turned around and is decelerating that's not going to be   
   much of a problem, but...   
      
     Right after tunaround the ship is still moving at a similar fraction of c   
   through the interstellar medium, which we're hoping is a very very thin gas of   
   mostly un-ionized hydrogen. It's kinda like taking a speedboat up to top   
   speed, killing the engine,    
   and somehow managing to spin the boat around so that it's facing backward   
   while still traveling at full speed. Also, it's moving faster than the speed   
   of sound in the ISM so there's a shock wave piled up in front of it and that's   
   going to create    
   turbulence as seen by the starship as it turns around. Granted, water is a   
   whole lot denser than the ISM, but that turbulent "breeze" will push back   
   against the exhaust trying to exit the nozzles when the engines relight. That   
   breeze will be fighting the    
   exhaust all the way creating even more turbulent flow all along the length of   
   the ship as the plumes grow until they reach the steady state of full thrust.   
   It's gonna be an exciting few minutes...   
      
     You know, the more I think about it, the less I like the idea of turning the   
   whole ship around.   
      
     Another thing; the fountain-style radiator *won't work* when the ship is   
   flying backward to decelerate because the molten metal coolant isn't going to   
   "fall back" to the dust shield- it'll just spray off into space and eventually   
   run out. If the ship    
   decelerates with the dust shield facing forward the spray will just go a   
   little farther before "falling back" (actually the ship runs into it).   
      
     It's starting to look to me like it would be better to have two drive   
   systems, one at each end of the ship, or better yet to have some way to rotate   
   the engines so they faced into the direction of flight for deceleration. I'd   
   still shut them down    
   before reorienting them. That keeps the dust shield facing forward for safety,   
   too. The main spine still has to go from tension into compression, but I think   
   that's doable.   
      
   > "One more thing- remember the engines are great big X-ray floodlights.   
   > They'll probably be detectable for many millions of miles. Also, the exhaust   
   > plume and whatever aleady-present gases you're running through will be   
   > fluorescing their asses off in the visible part of the spectrum. It will be a   
   > fearsome thing to see, getting bigger and brighter every day."   
   >    
   > Hm, so we have nice psychological - radiological weapon, fear the Mother   
   > Earth you Colonials ;p   
      
     Exactly! It also means there's no element of surprise, but so what? I'm   
   thinking that if you can send such a ship out in the first place you're not   
   worrying about stealth- the bolder you come in the better.   
      
   > Here comes also a problem of shooting at interstellar spaceship after it's   
   > detected, but I'm unsure how it would work out, because of how fast it moves   
   > and small reaction time.    
      
     Let's take Alpha Centauri-to-Earth (I'd do it the other way around but I   
   don't know how the planets there are arranged). As you mention below, space is   
   *big*. The ship has to start decelerating two-and-some-change light years out,   
   and therefore will be    
   visible from Earth two-and-some-change years from the moment the engines light   
   up, giving us whatever the deceleration time of the ship is to make plans (I'd   
   guess in the year and a half range). I don't suppose some random colony can   
   afford to send ships    
   out of its own system to attack the invader before it gets to their system, so   
   they have to let it get in-system.   
      
     If the target system is well-developed and can afford it, there might be   
   battles out between the stars but they'd be brief- weaponry would be large   
   dense objects designed to defeat the dust shield on the front of the ship.   
   Break that, the ship destroys    
   itself rapidly.   
      
     Anyway, when the ship gets to Sol system the main engines won't likely be   
   shut off until it gets to somewhere around Jupiter's orbit. That's about 7   
   light-hours away, but it will be traveling at most few thousand kps so it can   
   enter Earth orbit when it    
   gets here. That means if we shot at it with lasers it would be damn near to   
   Mars orbit by the time the laser beams got to it. And yes, we could see it   
   with the Hubble, Spitzer, or Webb orbital telescopes- that was established in   
   another thread.   
      
     If you don't want to wait for it to get up close and personal before   
   starting to fight, the smart thing to do would be to determine where it will   
   be at every moment for the next week or so from the time the engines shut   
   down, and launch missiles (or    
   whatever) to intercept it by the time the missiles can get to where it will   
   be, at the maximum speed the missiles can travel. That might sound impossible   
   to predict but remember that the closer it gets, the fewer trajectories it has   
   available to it to    
   get to Earth. It's kinda like it's running down a funnel pointing at Earth.   
      
     Also, maybe separating the ship into pieces isn't the best idea. If it came   
   into Earth orbit it would be most stable with its long axis extended through   
   the Earth; it could do so with the shield facing Earth to stop nuclear   
   missiles and whatnot.   
      
   > "On final thing- do you know the Kzinti Lesson?"   
   >    
      
   [continued in next message]   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)