Thank you for looking into this in depth! My apologies, I have only skimmed the report so far, but I have a few questions:
(1) Suppose someone used 100 starship launches to put optimal debris into orbit. Suppose someone else had capacity for 1000 starship launches. Could they just… Put armor on their spaceships/satellites &/or build them with redundant structures so they can take a hit or two? This would increase the weight of course but maybe that’s fine since there’s plenty of launch capacity?
(2) My understanding is that if you orbit closer to earth, atmospheric drag becomes a problem. But it is less of a problem for objects with lower surface area to mass ratios, which inherently advantages larger objects. So… Couldn’t you just have fewer, bigger, armored satellites that orbit closer to earth where the little debris can’t go?
(3) Another strategy of course would be to boost out to a high orbit away from all the debris. It seems you considered this strategy and calculated that with e.g. 40 starships of debris it wouldn’t work. What’s the difference in difficulty between trying to block boosts to normal orbits like LEO vs trying to block something going into a very high orbit or escaping orbit entirely? Does it take e.g. an OOM less debris to block the former vs. the latter? Five OOMs?
I think the considerations for shielding vs redundancy are very different. Redundancy quickly becomes non-viable because the amount of redundant launches you need blows up with the amount of debris.[1] But yeah, I think shielding probably helps a lot, and it’s a big reason I’m not very worried that a decently well-resourced actor would be locked out of space after 100 Starships of debris get released into orbit.
Yep that’s right. One thought is that debris eventually has to pass through those altitudes as it de-orbits, so there would be less of it (because it’s more transient) but maybe still enough to make no lower orbits much more viable. Also my impression is that sats are already sitting about as low-orbit as they can go before (below ~500km) it quickly becomes a lot more expensive to operate them because you need to overcome drag. As you say it might make more sense to sit at higher altitudes. In either case I do think the most likely outcome (especially from ‘accidental’ Kessler syndrome) is that operating sats just becomes a lot more expensive.
The two big considerations here are the amount of time you have to spend passing through different altitudes, and the amount of debris at different altitudes. Launches spend about 10 mins passing through LEO. Satellites in LEO spend… as long as you want to operate them. To make launching through orbit non-viable, vs making it non-viable to operate a satellites in LEO for a year, I think you need about 500x more debris. You could place sats at higher orbits and I think that would help a lot, though it would suck a bit because e.g. higher latencies. If the adversary is still on the loose, they could place debris at whatever altitude you picked, and at higher altitudes it would not de-orbit naturally for centuries or more. I don’t know how much more debris that would take vs sats in LEO, but it’s upper-bounded at 500x. 5–100x?
I guess an overall vibe I should convey a bit more is: before investigating deliberate space debris, it seemed like it could be a very big deal for macrostrategy. Having investigated it, I think it’s much less of a big deal (but still probably underrated by the world). I also think there could be much better launch-blocking strategies which don’t involve debris.
If one rocket collides with 7 bits of debris on average (and collisions are always catastrophic and Poisson distributed), you need to send about 1,000 launches for >50% chance at least one makes it. But after roughly doubling the amount of debris, so one rocket collides with 15 bits of debris on average, you need more than 2 million launches.
Here’s a possible launch-blocking strategy: Orbital lasers and/or kinetic interceptors.
You have a dense grid of laser satellites in orbit. Those on earth trying to get up into space face some disadvantages:
If they stay down on earth and shoot up at your satellites, while your satellites shoot back at them e.g. with lasers and kinetic interceptors, the gravity well gives you an inherent disadvantage. Your stuff has to climb out of the gravity well to hit the satellites whilst their stuff just has to fall down at the right angle. Plus also, the atmosphere and day-night cycle makes your solar panels much less efficient than theirs, so in a war of lasers they might just be able to outproduce you, plus the atmosphere makes the lasers inefficient anyway.
If they try to power up into space to fight you there using rockets, well, a big rocket can be blown up by a small bullet or laser burst as it exits the atmosphere and tries to accelerate to orbital velocity. Very vulnerable. If you try to armor it, you need to armor not just the payload but the rocket itself, which will be like an OOM bigger than the payload, plus the armor might weigh the thing down a lot reducing payload size.
A counterpoint is that you have to spread out your satellites in a grid whereas they can launch their entire fleet all at once in a single location to try to break through the grid. But yeah.
Thank you for looking into this in depth! My apologies, I have only skimmed the report so far, but I have a few questions:
(1) Suppose someone used 100 starship launches to put optimal debris into orbit. Suppose someone else had capacity for 1000 starship launches. Could they just… Put armor on their spaceships/satellites &/or build them with redundant structures so they can take a hit or two? This would increase the weight of course but maybe that’s fine since there’s plenty of launch capacity?
(2) My understanding is that if you orbit closer to earth, atmospheric drag becomes a problem. But it is less of a problem for objects with lower surface area to mass ratios, which inherently advantages larger objects. So… Couldn’t you just have fewer, bigger, armored satellites that orbit closer to earth where the little debris can’t go?
(3) Another strategy of course would be to boost out to a high orbit away from all the debris. It seems you considered this strategy and calculated that with e.g. 40 starships of debris it wouldn’t work. What’s the difference in difficulty between trying to block boosts to normal orbits like LEO vs trying to block something going into a very high orbit or escaping orbit entirely? Does it take e.g. an OOM less debris to block the former vs. the latter? Five OOMs?
Thanks for the qs!
I think the considerations for shielding vs redundancy are very different. Redundancy quickly becomes non-viable because the amount of redundant launches you need blows up with the amount of debris.[1] But yeah, I think shielding probably helps a lot, and it’s a big reason I’m not very worried that a decently well-resourced actor would be locked out of space after 100 Starships of debris get released into orbit.
Yep that’s right. One thought is that debris eventually has to pass through those altitudes as it de-orbits, so there would be less of it (because it’s more transient) but maybe still enough to make no lower orbits much more viable. Also my impression is that sats are already sitting about as low-orbit as they can go before (below ~500km) it quickly becomes a lot more expensive to operate them because you need to overcome drag. As you say it might make more sense to sit at higher altitudes. In either case I do think the most likely outcome (especially from ‘accidental’ Kessler syndrome) is that operating sats just becomes a lot more expensive.
The two big considerations here are the amount of time you have to spend passing through different altitudes, and the amount of debris at different altitudes. Launches spend about 10 mins passing through LEO. Satellites in LEO spend… as long as you want to operate them. To make launching through orbit non-viable, vs making it non-viable to operate a satellites in LEO for a year, I think you need about 500x more debris. You could place sats at higher orbits and I think that would help a lot, though it would suck a bit because e.g. higher latencies. If the adversary is still on the loose, they could place debris at whatever altitude you picked, and at higher altitudes it would not de-orbit naturally for centuries or more. I don’t know how much more debris that would take vs sats in LEO, but it’s upper-bounded at 500x. 5–100x?
I guess an overall vibe I should convey a bit more is: before investigating deliberate space debris, it seemed like it could be a very big deal for macrostrategy. Having investigated it, I think it’s much less of a big deal (but still probably underrated by the world). I also think there could be much better launch-blocking strategies which don’t involve debris.
If one rocket collides with 7 bits of debris on average (and collisions are always catastrophic and Poisson distributed), you need to send about 1,000 launches for >50% chance at least one makes it. But after roughly doubling the amount of debris, so one rocket collides with 15 bits of debris on average, you need more than 2 million launches.
Here’s a possible launch-blocking strategy: Orbital lasers and/or kinetic interceptors.
You have a dense grid of laser satellites in orbit. Those on earth trying to get up into space face some disadvantages:
If they stay down on earth and shoot up at your satellites, while your satellites shoot back at them e.g. with lasers and kinetic interceptors, the gravity well gives you an inherent disadvantage. Your stuff has to climb out of the gravity well to hit the satellites whilst their stuff just has to fall down at the right angle. Plus also, the atmosphere and day-night cycle makes your solar panels much less efficient than theirs, so in a war of lasers they might just be able to outproduce you, plus the atmosphere makes the lasers inefficient anyway.
If they try to power up into space to fight you there using rockets, well, a big rocket can be blown up by a small bullet or laser burst as it exits the atmosphere and tries to accelerate to orbital velocity. Very vulnerable. If you try to armor it, you need to armor not just the payload but the rocket itself, which will be like an OOM bigger than the payload, plus the armor might weigh the thing down a lot reducing payload size.
A counterpoint is that you have to spread out your satellites in a grid whereas they can launch their entire fleet all at once in a single location to try to break through the grid. But yeah.