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Won't be much point in space war if LEO is filled with space debris before the war even begins. The Chinese constellations going up at 800-1200km altitude are m

by mapt 2y ago

Won't be much point in space war if LEO is filled with space debris before the war even begins. The Chinese constellations going up at 800-1200km altitude are more than sufficient to destroy safe access to space for centuries, before you even consider the fact that their upper stages appear to explode into thousands of pieces every single launch after releasing their payload. Every hundred kilometers of altitude increases orbital lifespan by about a factor of ten. AFAICT Elon voluntarily reduced his proposed orbital altitudes, apparently without any pressure from regulators, when it was recognized that debris from 20-year-old SpaceX satellites would likely destroy 1-year-old SpaceX satellites reliably enough to cost SpaceX debilitating amounts of money. Even at ~550km, the concerns are significant for a 10^5 satellite swarm. Conversely, if we load up on SEP and fly a billion satellites (with a B) at 300km altitude, shooting each other with buckshot, it's safe to fly again in a very short period. If we can't get some kind of international agreement on restricting mega-constellations to very low altitudes, with a quickness, and with a consensus strong enough to hold during wartime and in the face of competing profit interests, then the game is lost before we even begin. Mid to Upper LEO is uniquely uncompromising to a race that refuses to cooperate with each other; A war up there would have qualities of MAD, but even a peacetime competition is sufficient to lock us out.

marssaxman 2y ago
What is SEP? Presumably unrelated to "simplified employee pension", which was the only thing a search turned up...
- mapt 2y ago
  Solar electric propulsion. If you want to be really safe, you need to fly so low that you have to exert a few millinewtons of steady thrust to overcome inertia lost to atmospheric drag. The natural orbital lifespan is less millennia or centuries, and more months or weeks; this is what keeps debris out of your path and out of having significant figures in any exponential growth equations. Ion thrusters can now do this continuously for a decade from quite small, inexpensive argon propellant tanks, and that sort of thing now flies on every Starlink satellite already for orbital adjustments, albeit with undersized propellant tanks. Do this right, low enough, and you can run something like a global cellular network with a million nodes without even having to think about avoidance maneuvers. Fly too high with too many satellites, and no amount of avoidance maneuvers per day will be enough. If you want to be conservative about human spaceflight, ban all large constellations above or at ISS altitude (or some arbitrary safety altitude); It's virtually impossible for debris to go higher, while all high debris will ultimately decay into lower debris.

by mapt 2y ago

marssaxman 2y ago

What is SEP? Presumably unrelated to "simplified employee pension", which was the only thing a search turned up...

mapt 2y ago
Solar electric propulsion. If you want to be really safe, you need to fly so low that you have to exert a few millinewtons of steady thrust to overcome inertia lost to atmospheric drag. The natural orbital lifespan is less millennia or centuries, and more months or weeks; this is what keeps debris out of your path and out of having significant figures in any exponential growth equations. Ion thrusters can now do this continuously for a decade from quite small, inexpensive argon propellant tanks, and that sort of thing now flies on every Starlink satellite already for orbital adjustments, albeit with undersized propellant tanks. Do this right, low enough, and you can run something like a global cellular network with a million nodes without even having to think about avoidance maneuvers. Fly too high with too many satellites, and no amount of avoidance maneuvers per day will be enough. If you want to be conservative about human spaceflight, ban all large constellations above or at ISS altitude (or some arbitrary safety altitude); It's virtually impossible for debris to go higher, while all high debris will ultimately decay into lower debris.