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Not-So-Brilliant Pebbles

Gravel Missile Defense
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As the recent destruction of an obsolete communications satellite by a Chinese missile has shown, even a tiny amount of widely distributed debris can be catastrophic to space vehicles. Since the trajectory of ballistic missiles takes them into space, an effective ballistic missile defense could be constructed of a cloud of particles through which the warheads would have to pass in order to reach their target.

Pea-sized gravel at a very modest density would be sufficiently massive to destroy any warhead. A missile warhead, entering a cloud of Not-So-Brilliant Pebbles at ballistic speed would be, if not utterly destroyed, rendered completely inoperable upon striking even a single orbiting pea-sized rock. With a properly dispersed cloud, the chance of a warhead getting through without contacting a Not-So-Brilliant Pebble would be similar to the probability of running a marathon in the rain without getting wet.

Quartz (naturally occurring vitreous silica) pebbles would be an ideal material for Not-So-Brilliant Pebbles. It is non-metallic, highly non-reactive, has a compressive strength greater than 160,000 psi and is translucent to microwave transmission over a wide range of frequencies, making it friendly to communication satellites. The Not-So-Brilliant Pebbles could easily be distributed into a few specific orbital bands that would blanket the most common ballistic trajectories while leaving clear zones for spacecraft to navigate.

The material itself is dirt cheap and the technology for collecting, sizing, and transporting it is both mature and inexpensive. The largest cost of the Not-So-Brilliant Pebbles system is orbital placement. While NASA’s cost is running close to $20,000 US per pound to orbit, private contractors are estimating $1,400 per pound, and this price would drop significantly due to economy of scale if operations were ramped up as necessary to accomplish this program. At a cost of $1,000 per pound, the $60 billion budget projected by the Congressional Budget Office for a ‘limited’ national missile shield would fund the lofting of 30,000 tons of highly effective Not-So-Brilliant Pebbles.

There are no countermeasures against gravel. Mirroring, dummy warheads, multiple independent warheads, etc. would all be destroyed during reentry though what is effectively a gravel cloud. Armoring warheads heavily enough to survive reentry would make them too heavy to launch. Attempting to lob a warhead through a hole shot through the cloud of Not-So-Brilliant Pebbles with a one or more nuclear explosions would be ineffective as the orbital transit progressed and ‘new’ pebbles moved in to fill the void. Additionally, the blast effect of the ‘cloud clearing’ munitions would have negative consequences for trailing warheads, as has been demonstrated in nuclear testing.

A useful byproduct of Not-So-Brilliant Pebbles is filtering of sunlight, not enough to cause noticeable darkness but sufficient to reflect a portion of the sun's rays back into space, reducing solar gain and easing global warming.

nuclear hobo, Feb 18 2007

Orbital Debris http://www.discover.../rd/map-space-junk/
Map: Space Junk [nuclear hobo, Feb 18 2007]

Like picking up trash by the freeway, the work is never done Near_20Earth_20Orbi...ation_20Corporation
[normzone, Feb 18 2007]

Technovelgy: Debris Clouds in space http://www.technove...ews.asp?NewsNum=931
Oops, normzone, I didn't mean to chase you into withdrawing your comments. In lieu of an actual visit to a library, here's technovelgy claiming that "Science fiction authors have long been concerned about debris in space. " [jutta, Feb 19 2007]

Gravel antisatellite weapon. http://taylor.typep.../high_frontier.html
The third I found. [bungston, Feb 19 2007]

[link]






       Rock hit science.
imaginality, Feb 18 2007
  

       You do realize this will also destroy any legitimate spacecraft. Clever idea, but I don't think it's worth the end of the entire space program.
5th Earth, Feb 18 2007
  

       [comment withdrawn]
normzone, Feb 18 2007
  

       For those of us not up on our SF reading, could you give details?
jutta, Feb 18 2007
  

       I will withdraw my earlier comment rather than go to the library and pore through the tomes today.   

       This is an interesting time for data storage and reference. Perhaps when Google books is completed it will be easier to link to pieces of information that exist in print but have not yet made it to the web.   

       Having spent much of my earliest youth with my nose in science fiction books (and I mean real SF, not Space Opera) often the ideas I see here smack of rediscovery at best.   

       But since I'm not willing to go do the research today to back up my earlier statement, statement withdrawn.
normzone, Feb 18 2007
  

       //You do realize this will also destroy any legitimate spacecraft.//   

       The gravel would be dispersed in specific orbital bands along the most likely ballistic missile trajectories. This would leave clear areas to allow a 'legitimate' space travel. Think of the rings of Saturn, though not necessairy in the same orientation.   

       Currently, space debris orbits randomly, presenting (as time goes on) and ever increasing threat to spacecraft. Not-So-Brilliant Pebbles, confined to orbital bands, would be easily mapped and navigated.
nuclear hobo, Feb 18 2007
  

       Just one more well-intentioned mess that the lane sweepers will have to deal with (link).
normzone, Feb 18 2007
  

       The main problem is that as time goes on, these "confined" orbital bands will become less, and less defined. Satellites require large supplies of pressurized gasses for use in station keeping. Even with these supplies, keeping a satellite in geosynchronous orbit longer than 15 years is a feat, and at the end of that time, the satellite must be safely "de-orbited" by causing it to burn up in the atmosphere, or crash into the ocean, by using the remaining attitude jets they can use.   

       Bits of gravel have no station keeping jets, and their random shapes and masses ensure that microgravity interactions off pebbles in a band will cause some to dispers, come together, impact, break apart, and otherwise spread about the orbital path, enter wider, and more dispersed orbits. While they would probably de-orbit eventually, and they should be small enough to do so safely, keeping track of where they go before that will be difficult.   

       It is this very concern that has led the chinese missile test to gain so much attention, because supposedly, they have spread enough debris (which will more or less follow orbits somewhere between those of the missile, and the orbiting body the missile hit) that these bits of debris will disable other satellites before they can be safely de-orbited. Many of the pieces are only a few inches in size, and are difficult to track from earth.   

       After a few million years, particles such as this may establish stable orbits, somewhat like the asteroid belt, but until gravitational resonance has an effect, there will be little control or predictability to the pattern.
ye_river_xiv, Feb 18 2007
  

       I have heard this idea before. A google for "korea gravel satellite" found many different iterations - linked is one that quotes a 2001 article from Military Review. That said, it is not a bad idea, and I do not think it has been on the halfbakery before now.
bungston, Feb 19 2007
  

       It occurs to me that if this antisatellite buckshot were made of ice, it would still pack a wallop but would then sublimate away, minimizing the subsequent "space junk" impact/
bungston, Feb 19 2007
  

       [bungston], you got me there. We may need some more physics here. Don't you need to have a couple of things to do that? Heat, and atmosphere? I know there's temperature fluctuations, but is there a media to carry it away? Is the fluctuation enough to affect the ice? [waves for the physics lifeguard)   

       Thanks, [jutta], but I can usually quote author, and most of the time edition. Relying on general knowledge, I didn't feel comfortable with my usual rallying cry of "preheated".
normzone, Feb 19 2007
  

       Ice will sublimate directly to vapor in a vacuum. Or not in a vacuum: for example, you may notice that on returning from vacation, your ice cubes are smaller. The lower the vapor pressure, the more tendency to sublimate. Vapor pressure is low in space.   

       As regards a media to carry it away, we both know that space is full of the all-pervading ether and that should suffice. The water vapor will dissociate down to molecules and float around in orbit with everything else, but hopefully harming nothing.
bungston, Feb 19 2007
  

       Certainly fully preheated in the "Traveller" rpg from the early 80's - one of the things you could have fitted to your vessel was a "sandcaster" - designed to lay down a field of sand/gravel in order to deflect/destroy incoming lasers, ordanance and high velocity ships.
zen_tom, Feb 22 2007
  

       This is the first anti-missile proposal I've ever heard that I think would actually work - and if I thought nuclear war using ballistic missiles was a real threat I'd gladly sacrifice the entire space program, communication satellites and everything for it.   

       However, there are much easier ways of delivering nuclear warheads than ballistic missiles - the obvious method, against which there is no realistic defence in the modern world, being in a standard shipping container - and I don't think anyone would be likely to bother with ballistic missile delivery. Ballistic missile development is purely machismo.
Cosh i Pi, Apr 11 2007
  
      
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