From: chakatfirepaw@gmail.com   
      
   On Tue, 04 Oct 2016 07:25:07 -0700, Mikkel Haaheim wrote:   
      
   > Le lundi 26 septembre 2016 01:19:13 UTC+2, Rick Pikul/Chakat Firepaw a   
   > écrit :   
   >   
   > Okay, getting back to you...   
   >   
   >> > Still, I have demonstrated that the mass can be significantly reduced   
   >> > for more reasonable strikes. You can even decrease the mass below 1g,   
   >> > especially if you decide to use an explosive shell or armour piercing   
   >> > design.   
   >>   
   >> Um, no.  First of all, at the speeds we are talking non-nuclear   
   >> warheads are nothing but a sub-munition distribution technique due to   
   >> the 1st law of space combat, (at 3 km/s you pack your own mass in   
   >> blam).   
   >   
   > I also wanted to say on this first point that you are actually making   
   > the job easier for me. The fact that just a little mass has so much   
   > destructive energy supports my statement that the total mass required   
   > can continue to be reduced.   
      
   It doesn't help if you can't hit.   
      
   > Furthermore, although you are quite correct about armour peircing shells   
   > not being a requirement, I had a slightly different intent in mind for   
   > the use of the explosive shell, which I should have made more explicite.   
   > Detonating the shell just before contact sends a splatter of shrapnel,   
   > which is quite effective at scouring detectors, rendering them unusable.   
   > This also takes care of those gap issues we were discussing.   
      
   To have something like that you need larger shells.  That means either   
   more mass, a narrower area of attack or larger gaps between your shells   
   than you would have had between the shot.   
      
   > Second, you   
   >> have to drop the mass/area by multiple orders of magnitude, (using my   
   >> earlier, wrong, calculation:  To get to 'only' a kilotonne of stuff you   
   >> need to get down to 10 _micrograms_ per square metre).   
   >   
   > Or decrease the target area. Yes.   
      
   Which is something you can't afford to do.  Consider, in a 1AU orbit a   
   normal burn that shifts things by a single arc second means a difference   
   of ~750km in three months.   
      
   Now consider something that is doing that once a month and you have a   
   time in flight of 3-4 months.   
      
   >> > In war, "sane" amounts of material is quite subjective.   
   >>   
   >> Masses measured in Zg are almost never sane.   
   >   
   > Depends upon the amount of waste material being excavated with the   
   > usable material.   
      
   Getting it isn't so hard, it's getting it up to 10,000m/s or so.   
      
   > Also depends upon the energy available. If we are   
   > dealing with colonies that can afford building their own space navies,   
   > the availablity of both will likely be extremely high.   
      
   You don't quite grok the energy needed.   
      
   We're talking an exajoule per shot, before losses.  Let's make a few   
   assumptions:  Start with an accelerator that is 40% efficient when all is   
   said and done, (loading systems, dealing with recoil, ancillary systems,   
   etc. as well as simple losses).   
      
   so 1EJ / 40% = 2.5EJ   
      
   Now, to determine power, we need to figure how long we have to collect   
   that much energy.  Let's go with a day for now but we can look at longer   
   times later.   
      
   2.5EJ / (24hr * 3600 s/hr) = 29TW   
      
   Generating that is going to be fun, lets try doing it with solar.  We'll   
   place this in the asteroid belt, (there really isn't anywhere closer to   
   the sun that works), so we have ~250 W/m^2 of light, (it's 1400 W/m^2 at   
   Earth, and we're out around 2.5AU).  So we need the light from:   
      
   29TW / 250 W/m^2 = 1.16e11 m^2  Or a square 340km on a side.   
      
   But that's for magical 100% efficient solar collectors.  Let's assume 50%   
   efficiency, so double the area.   
      
   2.31e11 m^2, or a 480km square   
      
   There are other possibilities, such as nuclear.  However, at those power   
   levels you aren't going to be able to hide the reactors so you would end   
   up with one of two situations:  Either you create something that says   
   "look at me!" all the time if it's a fission system or something that   
   screams "I'm about to do something big!" the instant a fusion system   
   powers up.   
      
   Using multiple launchers and a slower rate of fire will help, but to get   
   it down to something that isn't spotted instantly would mean having what   
   amounts to a single-shot system.  (Better hope nothing ever happens with   
   your energy storage system, if you think a cellphone battery failure is   
   nasty....)   
      
   >> Except that you aren't launching 100 of them, you are launching   
   >> trillions of them.   
   >   
   > Probably. But this is a benchmark from existing tech. Using existing   
   > tech, it gives you an idea of how much energy will be required (yes, it   
   > is phenomenal, but militaries are often ready to use "phenomenal"   
   > resources in times of war.   
      
   You don't get quite how phenomenal the numbers involved are.   
      
   To give you a modern benchmark, each of these shots contains as much   
   energy as Earth's entire electricity output for ten days.   
      
   >> Um, that figure I used was for launching from Ceres, (it's actually   
   >> ~7.5 km/s, but I was only claiming an order of magnitude).  To get down   
   >> to ~3 km/s you need to be out past Saturn.   
   >   
   > Sorry, I did not have the data for Ceres at the time. I was using a   
   > guestimate from inside of Jupiter's orbit. I believe your figure from   
   > Saturn includes escape velocity requirements. From a shared orbit with   
   > Jupiter, but NOT in its SOI, the figure I get from a number of different   
   > sources confirms a required Delta-V of about 2.5 km/s (rounding up to 3   
   > km/s gave me that guestimate value from somewhere inside Jupiter's   
   > orbit.   
      
   Funny, I just checked a couple and got values of ~24-26 km/s needed in   
   total when you are at 2.5-3AU, less the orbital velocities of ~17-19 km/s   
   means you need a deltaV of somewhere around 7 km/s or so.   
      
   >> All of which are in line to hit your launching facility.  Further, you   
   >> have already defined them as something that can damage space hardware   
   >> as opposed to the tiny dust of a comet's tail.   
   >   
   > First, you are assuming that these are failing to achieve escape   
   > velocity. Once again, providing them with sufficient delta-V to escape   
   > the solar system is not difficult.   
      
   It's possible, but not as easy as you think.   
      
   > Second, the orbits are going to be out of phase. Yes, if they fail to   
   > leave solar orbit, they might return to where they were launched from...   
   > but it will likely be thousands of years before the disperse orbits are   
   > in-synch again.   
      
   That will depend on the trajectories involved.  Note that the stream will   
   continue to spread out lengthwise, you won't need to be perfectly synced   
   up to be in trouble.   
      
   >> > If you scan, yes. However, if you scan, you leave open large windows   
   >> > where you can sneak manoeuvres in.   
   >>   
      
   [continued in next message]   
      
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