3 ms·

In this case, the context is "we face the same risk all the time, from asteroids we don't see." I'm not convinced that's reassuring. The Sagan paper concerns m

In this case, the context is "we face the same risk all the time, from asteroids we don't see." I'm not convinced that's reassuring. The Sagan paper concerns much larger asteroids, which are correspondingly more rare. For asteroids in the 8MT impact range, it doesn't make much military sense to launch deep space missions to divert them years in advance, rather than delivering nukes directly with ICBMs in minutes. Given any competent asteroid defense system, an asteroid diversion would be detected immediately and countered, and the perpetrators would face consequences. In fact, since we already have rockets that can reach asteroids, I'd say the possibility of malicious diversion makes a defense system more important.

perihelions 2y ago
- "The Sagan paper concerns much larger asteroids, which are correspondingly more rare." That's a fair distinction—the paper predates the modern telescope surveys that are discovering all the small ones. - "rather than delivering nukes directly with ICBMs in minutes" You'd still need multiple years for those nukes to have a useful effect. (The change in velocity is instant; the change in position is not). They wouldn't be ICBM's, either: we'd need a new type of deep-space delivery vehicle, far larger than a suborbital ICBM. That'd probably trigger a new type of nuclear arms race.
- DennisP 2y ago
  Sorry, what I mean is: why would I use my rocket and nuke to divert an asteroid years in advance, when I can drop an 8MT nuke on you directly in 30 minutes with much more accurate targeting? One possible reason is plausible deniability, but that goes away if we have a good asteroid defense system with an emphasis on early detection.
  - perihelions 2y ago
    Ah, I understand now. For one thing, you could weaponize asteroids as a second-strike response, if there's an imbalance where one superpower has asteroid deflection and one does not. Even if it's delayed by months, the certainty that the asteroid will eventually hit establishes a deterrent against attacking the asteroid-controlling country. If there's defenses against ballistic missiles, this circumvents those. For another, the asteroid-deflecting nukes are dual-use as weapons themselves. A nuclear warhead in deep space defeats conventional ballistic missile defenses. If that warhead is turned towards Earth, that (first-strike) attack's not visible to the adversary until a few seconds before impact—unlike an ICBM launch, which has tens of minutes of warning, enough to launch (conventional) interceptor missiles.
    - wing-_-nuts 2y ago
      Eh, we already have steath aircraft that could slip in past air defenses and drop a nuke with next to no warning. We probably have a stealthy hypersonic that can also do so. That doesn't negate a nations second strike ability. Part of the reason the US, Russia and China have vast land based missile fields is to visibly show the enemy that they're gonna have to wipe out huge swaths of land with hundreds of nukes (and THEN sink our boomers) to have a successful first strike.
      - perihelions 2y ago
        Right; but if the enemy thinks that's likely to happen, it'd only take them 15 minutes to nuke that one airbase that stores all the B-2's. Strategic bomber aircraft aren't very useful weapons for superpowers fighting each other (or else we'd have a lot more B-2's). Space-based weapons (which are banned by treaty) are more like submarine-basing, in that the enemy isn't necessarily sure where they are; but, in addition to that, they have potentially very short warning times before a strike. No one actually wants that unstable dynamic, with the short/no-warning; which is why all the nuclear powers have (so far) agreed by treaty not to build any. edit: But if someone were to build a civilian spaced-based asteroid defense, which involved sending nuclear weapons into space... that could get destabilizing fast. Whether or not Sagan can predict specifics, the big-picture idea of humans not trusting each other with apocalyptic weapons is not wrong. (Worth recalling the USSR genuinely mistook the civilian US Space Shuttle for a nuclear weapons platform).
        quesera 2y ago
        Forgive my naivete, but do we really have the precision measurements and kT payload calibration needed to alter an asteroid's trajectory and speed to the point that we can target specific (even very large) country landmasses as the Earth's rotation exposes them to the oncoming projectile?
        perihelions 2y ago
        No, nothing about asteroid deflection is precise; the physics are messy and we know little about them.
- wing-_-nuts 2y ago
  >we'd need a new type of deep-space delivery vehicle, far larger than a suborbital ICBM. Like...starship? > That'd probably trigger a new type of nuclear arms race. Why on earth would there be an arms race on something designed to deliver nuclear payloads to deep space? The only way I could see that happening is if we had nuclear armed deep space colonies? (See, the expanse)

perihelions 2y ago

- "The Sagan paper concerns much larger asteroids, which are correspondingly more rare." That's a fair distinction—the paper predates the modern telescope surveys that are discovering all the small ones. - "rather than delivering nukes directly with ICBMs in minutes" You'd still need multiple years for those nukes to have a useful effect. (The change in velocity is instant; the change in position is not). They wouldn't be ICBM's, either: we'd need a new type of deep-space delivery vehicle, far larger than a suborbital ICBM. That'd probably trigger a new type of nuclear arms race.

DennisP 2y ago
Sorry, what I mean is: why would I use my rocket and nuke to divert an asteroid years in advance, when I can drop an 8MT nuke on you directly in 30 minutes with much more accurate targeting? One possible reason is plausible deniability, but that goes away if we have a good asteroid defense system with an emphasis on early detection.
- perihelions 2y ago
  Ah, I understand now. For one thing, you could weaponize asteroids as a second-strike response, if there's an imbalance where one superpower has asteroid deflection and one does not. Even if it's delayed by months, the certainty that the asteroid will eventually hit establishes a deterrent against attacking the asteroid-controlling country. If there's defenses against ballistic missiles, this circumvents those. For another, the asteroid-deflecting nukes are dual-use as weapons themselves. A nuclear warhead in deep space defeats conventional ballistic missile defenses. If that warhead is turned towards Earth, that (first-strike) attack's not visible to the adversary until a few seconds before impact—unlike an ICBM launch, which has tens of minutes of warning, enough to launch (conventional) interceptor missiles.
  - wing-_-nuts 2y ago
    Eh, we already have steath aircraft that could slip in past air defenses and drop a nuke with next to no warning. We probably have a stealthy hypersonic that can also do so. That doesn't negate a nations second strike ability. Part of the reason the US, Russia and China have vast land based missile fields is to visibly show the enemy that they're gonna have to wipe out huge swaths of land with hundreds of nukes (and THEN sink our boomers) to have a successful first strike.
    - perihelions 2y ago
      Right; but if the enemy thinks that's likely to happen, it'd only take them 15 minutes to nuke that one airbase that stores all the B-2's. Strategic bomber aircraft aren't very useful weapons for superpowers fighting each other (or else we'd have a lot more B-2's). Space-based weapons (which are banned by treaty) are more like submarine-basing, in that the enemy isn't necessarily sure where they are; but, in addition to that, they have potentially very short warning times before a strike. No one actually wants that unstable dynamic, with the short/no-warning; which is why all the nuclear powers have (so far) agreed by treaty not to build any. edit: But if someone were to build a civilian spaced-based asteroid defense, which involved sending nuclear weapons into space... that could get destabilizing fast. Whether or not Sagan can predict specifics, the big-picture idea of humans not trusting each other with apocalyptic weapons is not wrong. (Worth recalling the USSR genuinely mistook the civilian US Space Shuttle for a nuclear weapons platform).
      - quesera 2y ago
        Forgive my naivete, but do we really have the precision measurements and kT payload calibration needed to alter an asteroid's trajectory and speed to the point that we can target specific (even very large) country landmasses as the Earth's rotation exposes them to the oncoming projectile?
        perihelions 2y ago
        No, nothing about asteroid deflection is precise; the physics are messy and we know little about them.
wing-_-nuts 2y ago
>we'd need a new type of deep-space delivery vehicle, far larger than a suborbital ICBM. Like...starship? > That'd probably trigger a new type of nuclear arms race. Why on earth would there be an arms race on something designed to deliver nuclear payloads to deep space? The only way I could see that happening is if we had nuclear armed deep space colonies? (See, the expanse)