From: chakatfirepaw@gmail.com   
      
   On Thu, 15 Sep 2016 08:57:18 -0700, Mikkel Haaheim wrote:   
      
   You did notice that this discussion was a month and a half ago, right?   
      
   Or are you playing the "necro to get the last word" game?   
      
   > Le dimanche 31 juillet 2016 00:17:35 UTC+2, Rick Pikul/Chakat Firepaw a   
   > écrit :   
   >>   
   >>   
   >> Solar sails are only restricted in that they can't do radial-in burns,   
   >> they are just fine with pro/retrograde, (anti)normal and radial-out.   
   >> As it so happens, any radial-out burn can be reversed by another   
   >> radial-out burn at the other point the initial and final orbits   
   >> intersect.   
   >   
   > If I understand correctly what you have written, this is not quite   
   > accurate. The radial out burn at the opposing orbital point does not   
   > reverse the previou radial out burn. Rather, it circularises the higher   
   > orbit.   
      
   You do not understand because I never said anything about the opposing   
   orbital point:  "...the other point the initial and final orbits   
   intersect."   
      
   >> Not really, hitting the platforms involves firing shots that saturate a   
   >> target area at least one hundred _million_ square kilometres in size.   
   >> Cheap, unguided, shot means a minimum of about one 'pellet' per square   
   >> metre.   
   >   
   > This is not a problem. Yes, I have suggested 1 pellet/m^2, but you   
   > actually only need 1 pellet per sensor. The sensors will have to be   
   > large in order to obtain useful info. 1 pellet/10m^2 would likely be   
   > more than sufficient.   
   > Furthermore, pellets can be small. The impact of even a single gram will   
   > likely sufficiently damage the sensors.   
      
   And what will be the total mass of those pellets?   
      
   10,000,000 km^2 = 1e14 m^2   
      
   For a 1g pellet every 10 m^2 that's:   
      
   1e14 m^2 * 0.1 g/m^2 = 1e13g   
      
   That's ten _million_ _TONNES_.  For a shot that isn't even certain to   
   connect, (perfectly spaced they're 5.77m apart).   
      
   > You don't even need pellets...   
   > sensors are VERY sensitive to any kind of impact. Even high velocity   
   > dust will scour the collector dishes and optics, rendering them   
   > unusable. Given the size of the pellets or dust in question, the mass   
   > required to do sufficient damage, results in high arial coverage   
   > actually yielding fairly low actual masses or volumes.   
      
   You obviously either didn't do the math or made rather unrealistic   
   assumptions.   
      
   Or are you jumping around between units again:  Using one figure as the   
   radius of your shot cloud when claiming it will hit, then using the same   
   number as the area when claiming you can connect using a sane amount of   
   material.   
      
   >> And remember, these shot clouds are going to be coming back around to   
   >> intersect with the orbit of whatever you fired it from.   
   >   
   > Unlkely. The delta-v from a mass driver or coil/rail gun will easily   
   > place the shells in a parabolic, or even hyerbolic, escape trajectory.   
      
   Um, no.  You need on the order of 10km/s for escape trajectories, and   
   that's if you eject prograde from the body orbiting the sun.  For these   
   kinds of shots think 15-20km/at least.   
      
   > Also, dust and pellets will continue to disperse, leaving them no more a   
   > hazard than currently existing meteoroids.   
      
   Actually, they don't.  They just transform into a stream, meteor showers   
   are annual for a reason.   
      
   >> There is a critical difference:  In a space war you have to kill pretty   
   >> much _all_ of the 'radar stations', not just the ones around where you   
   >> want to act.   
   >   
   > Actually, you don't. I will explain shortly.   
      
   Actually, yes you do:  All of the stations can see almost everywhere, you   
   have no horizon to hide behind.   
      
   >> Remember that 'cold-running' means turning everything off, including   
   >> things like life support and any computer systems.  If you have   
   >> anything running you will have waste heat to get rid of.   
   >   
   > Incorrect. Cold running simply means that waste heat will have to be   
   > limited to what can be safely absorbed by the internal heat sink   
   > (cryogenic supply)   
      
   Which isn't that much, expect no more than a few months under ideal   
   conditions.   
      
   > or what can be emitted without allowing for detection.   
      
   Which also isn't that much   
      
   > Let's say you ere emitting 2.25 watts/s IR radiation.   
      
   So you are a tiny ship cooled to under 150K.   
      
   Even at a chilly 200K your hull is emitting 9 W/m^2, not the waste heat   
   from your systems, the hull itself, (and that's assuming you optimize for   
   minimal blackbody radiation).   
      
   (Psst:  W/s would be how fast your emissions are increasing, you simply   
   want W.)   
      
   > Much higher emissions could be   
   > undetectable if directed away from earth based receivers.   
      
   Multiple sensor platforms, remember?  Not simply orbiting a single   
   planet, remember?  Besides, controlling the direction your heat goes   
   takes energy and quickly becomes a Red Queen's race.   
      
   > Furthermore, although electronics can produce significant waste heat, as   
   > can human bodies, life support generally will not.   
      
   Life support means you have portions of your ship heated to 280K or more.   
      
   > Actually, much of the   
   > human and electronics generated waste heat will be absorbed in the   
   > processof bringing cryogenic oxygen supplies to usable temperatures.   
   > Properly handled, waste heat will actually be the sole source of   
   > environmental heating.   
      
   Think about why you need environmental heating.   
      
   >> Actually, those sensor platforms don't really exist.  At least not on   
   >> the scale we would be talking about in even a minimalist interplanetary   
   >> war scenario.  Putting a single satellite at the Earth-Sun L1 point was   
   >> a big deal.   
   >   
   > Platforms for searching for asteroids DO exist, but you are correct that   
   > there are very limited numbers of such platforms.   
      
   Congratulations, you managed to repeat the very caveat I made.   
      
   Describing that sensor platforms looking for interplanetary objects don't   
   really exist is as correct as saying that passenger aircraft didn't   
   really exist in 1914.   
      
   (FTR:  Four had been built by that time, with a total passenger capacity   
   of 30.)   
      
   > The cost of putting   
   > such platforms into space is rather the issue.   
      
   Right now it is, right now we aren't looking at even setting up the   
   preconditions of an interplanetary war being possible in the first place.   
      
   >> Putting sensor nets everywhere in the oceans has three problems:   
   >>   
   >> First, covering the whole thing would take a _lot_ of sensors,   
   >> (contrast with space, where you only need a few dozen at most).   
   >   
   > False assumption. Again, I will get to this later.   
      
   Nope, not false.  Your later simply shows that you still don't understand   
   how a sensor system like this would work.   
      
   (Hint:  Think about why radar dishes move and why they can get away with   
      
   [continued in next message]   
      
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