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I think you're forgetting a number of advantages. 1. Surprise. All land-based launch sites are actively monitored all the time, giving countries advance warni

I think you're forgetting a number of advantages. 1. Surprise. All land-based launch sites are actively monitored all the time, giving countries advance warning when a missile is launched. Submarine launches cut down this warning time, but still light up radar and thermal all over the place. A kinetic impactor falling from LEO can hit its target before the enemy even reports up the chain of command (we're talking single digit minutes). 2. Lack of radioactive fallout while still having larger destructive force than conventional munitions. If you need to destroy an entire air base far behind enemy lines, but don't want nearby population centers to be irradiated, you're looking at pretty bad options today, compared to a kinetic bombardment. 3. You can't really intercept a kinetic impactor. We have the technology right now to shoot small rockets right out of the sky, and at least a chance of intercepting ICBM payloads. With a kinetic rod, though, intercepting it wouldn't really do very much - it's just a big chunk of mass moving really fast. The best you could do is break it into smaller pieces that are still moving really fast.

nradov 10y ago
No that's all wrong. Firing a missile from orbit has less surprise value than firing from a submarine because satellites can't hide. There's no difference in kinetic effects; a non-nuclear ballistic missile can hit just as hard at a lower cost (do the math). A kinetic projectile launched from a satellite is no harder to intercept than a ballistic missile in the terminal phase, and satellites themselves are highly vulnerable. A big chunk of mass landing near a target won't have much effect. And the projectiles couldn't be just rods. Due to the variability in rockets used for de-orbit burns as well as atmospheric conditions they would need fragile and sensitive guidance packages.
- pavement 10y ago
  Kinetic impactors are not missiles. Repeat: Kinetic impactors are not missiles. https://en.wikipedia.org/wiki/Kinetic_bombardment https://en.wikipedia.org/wiki/Kinetic_bombardment These are not things that get fired. You don't launch them. They don't follow a trajectory. They might just travel straight down from a geostationary orbit, depending on implementation. Yes, a guidance package might be necessary (depending on target discrimination, and precision, which in warfare isn't always required). They aren't gliding like smart bombs though. At the speed of re-entry, and with possibly just 100 short miles to close, a defensive interceptor would be unwarned, have to acquire possibly many targets (one need not drop only one). Intercepting vehicles would have to close on a target in an arc representing a distance longer than the hypotenuse of the right triangle between the kinetic slug, the interceptor's launch site, and the defended target. The slug is simply released with no indication of ingress. From a geostationary orbit, it just starts getting closer very fast. Cover it with EM absorbant, non-reflective material, and there's even less hint of activity, until the re-entry burn at approximately 60 miles altitude. Unless the target itself is equipped with interceptors, and lots of them, it will be difficult to notice and recognize in time, and even harder to catch and defeat.
  - rocqua 10y ago
    > They don't follow a trajectory. They might just travel straight down from a geostationary orbit That's not how orbiting works. If you want your projectile to travel straight down, you need to cancel all it's orbital velocity. For geostationary orbit, that's 3km/s of delta V needed. Obviously, you can de-orbit with less delta-V, but then guidance starts becoming necessary. > The slug is simply released with no indication of ingress. From a geostationary orbit, it just starts getting closer very fast. Cover it with EM absorbant, non-reflective material, and there's even less hint of activity, until the re-entry burn at approximately 60 miles altitude. There is going to be some kind of burn to start de-orbit, you could simply monitor for that.
    - daemin 10y ago
      I am wondering, what kind of impact would the wind have on these projectiles? Or even on ballistic missiles? I would imagine a nuke having such a large explosion that missing the target by a kilometre won't matter too much. But with a kinetic projectile that kind of deviation would not be acceptable (unless we are talking about seriously big projectiles, like in Tunguska etc).
      - nradov 10y ago
        Wind and other transient atmospheric conditions have a major effect. That's why individual unguided projectiles can't reliably hit a target more than about 4 miles away, and even at that range you have to be really lucky. The range from LEO to surface is a lot longer.
        ethbro 10y ago
        If you were going to use this as a first or second strike kinetic weapon platform (and prepared to tap dance around the "no militarization of space" treaties by claiming it's an aircraft), then your biggest asset is orbital velocity. It's sitting up there doing 7-8 km/s. Obviously you don't want to do a powered de-orbit for reasons mentioned (you burn fuel & lose kinetic energy). However, if you're flying low enough, couldn't you aerobrake your projectiles after release and have them de-orbit themselves? For comparison, the X-41/51 scramjet programs appear to be aiming at the mach 5-9 region. So less than 1/2 as fast. As complicated as the materials science and guidance has to be for any X-71-based projectiles, slowing down and terminal guidance (ablative coatings and sacrificial control surfaces) seem like easier problems than boosting up to ridiculous velocities. As for tracking, you get the heat bloom as it aerobrakes, but if you manage to keep it coherent through re-entry then the ridiculous speed largely moots that. At 5 km/s, with a prograde orbit, you're from Istanbul to Beijing about 24 minutes (by my sleepy calculations?). The exercise seems more of a question of "How steep can you dive (aka how much heat can you handle)?" than anything else. PS: Well, and "How the hell do you communicate-with / sense-from a platform surrounded by air that hot?"

nradov 10y ago

No that's all wrong. Firing a missile from orbit has less surprise value than firing from a submarine because satellites can't hide. There's no difference in kinetic effects; a non-nuclear ballistic missile can hit just as hard at a lower cost (do the math). A kinetic projectile launched from a satellite is no harder to intercept than a ballistic missile in the terminal phase, and satellites themselves are highly vulnerable. A big chunk of mass landing near a target won't have much effect. And the projectiles couldn't be just rods. Due to the variability in rockets used for de-orbit burns as well as atmospheric conditions they would need fragile and sensitive guidance packages.

pavement 10y ago
Kinetic impactors are not missiles. Repeat: Kinetic impactors are not missiles. https://en.wikipedia.org/wiki/Kinetic_bombardment https://en.wikipedia.org/wiki/Kinetic_bombardment These are not things that get fired. You don't launch them. They don't follow a trajectory. They might just travel straight down from a geostationary orbit, depending on implementation. Yes, a guidance package might be necessary (depending on target discrimination, and precision, which in warfare isn't always required). They aren't gliding like smart bombs though. At the speed of re-entry, and with possibly just 100 short miles to close, a defensive interceptor would be unwarned, have to acquire possibly many targets (one need not drop only one). Intercepting vehicles would have to close on a target in an arc representing a distance longer than the hypotenuse of the right triangle between the kinetic slug, the interceptor's launch site, and the defended target. The slug is simply released with no indication of ingress. From a geostationary orbit, it just starts getting closer very fast. Cover it with EM absorbant, non-reflective material, and there's even less hint of activity, until the re-entry burn at approximately 60 miles altitude. Unless the target itself is equipped with interceptors, and lots of them, it will be difficult to notice and recognize in time, and even harder to catch and defeat.
- rocqua 10y ago
  > They don't follow a trajectory. They might just travel straight down from a geostationary orbit That's not how orbiting works. If you want your projectile to travel straight down, you need to cancel all it's orbital velocity. For geostationary orbit, that's 3km/s of delta V needed. Obviously, you can de-orbit with less delta-V, but then guidance starts becoming necessary. > The slug is simply released with no indication of ingress. From a geostationary orbit, it just starts getting closer very fast. Cover it with EM absorbant, non-reflective material, and there's even less hint of activity, until the re-entry burn at approximately 60 miles altitude. There is going to be some kind of burn to start de-orbit, you could simply monitor for that.
  - daemin 10y ago
    I am wondering, what kind of impact would the wind have on these projectiles? Or even on ballistic missiles? I would imagine a nuke having such a large explosion that missing the target by a kilometre won't matter too much. But with a kinetic projectile that kind of deviation would not be acceptable (unless we are talking about seriously big projectiles, like in Tunguska etc).
    - nradov 10y ago
      Wind and other transient atmospheric conditions have a major effect. That's why individual unguided projectiles can't reliably hit a target more than about 4 miles away, and even at that range you have to be really lucky. The range from LEO to surface is a lot longer.
      - ethbro 10y ago
        If you were going to use this as a first or second strike kinetic weapon platform (and prepared to tap dance around the "no militarization of space" treaties by claiming it's an aircraft), then your biggest asset is orbital velocity. It's sitting up there doing 7-8 km/s. Obviously you don't want to do a powered de-orbit for reasons mentioned (you burn fuel & lose kinetic energy). However, if you're flying low enough, couldn't you aerobrake your projectiles after release and have them de-orbit themselves? For comparison, the X-41/51 scramjet programs appear to be aiming at the mach 5-9 region. So less than 1/2 as fast. As complicated as the materials science and guidance has to be for any X-71-based projectiles, slowing down and terminal guidance (ablative coatings and sacrificial control surfaces) seem like easier problems than boosting up to ridiculous velocities. As for tracking, you get the heat bloom as it aerobrakes, but if you manage to keep it coherent through re-entry then the ridiculous speed largely moots that. At 5 km/s, with a prograde orbit, you're from Istanbul to Beijing about 24 minutes (by my sleepy calculations?). The exercise seems more of a question of "How steep can you dive (aka how much heat can you handle)?" than anything else. PS: Well, and "How the hell do you communicate-with / sense-from a platform surrounded by air that hot?"