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Unmanned U.S. Air Force space plane lands after secret, two-year mission

reuters.com

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Re: Unmanned U.S. Air Force space plane lands after secret, two-year mission

#171

Post by ethbro »

nradov wrote: post #152
daemin wrote: post #141

Earlier quoted context omitted.

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).

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.

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?"

Re: Unmanned U.S. Air Force space plane lands after secret, two-year mission

#172

Post by nradov »

ethbro wrote: post #171
nradov wrote: post #152

Earlier quoted context omitted.

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.

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,…

Orbital velocity is no asset. In fact rather the opposite. You can't just start aerobraking. There isn't enough air in orbit for parachutes or wings to have any noticable effect. The only practical way to get out of orbit using current technology is to conduct a de-orbit burn with chemical rockets.

Of course that's all pointless because a ballistic missile launched from Earth could accomplish the same mission at a far lower cost with greater reliability and survivability.

Re: Unmanned U.S. Air Force space plane lands after secret, two-year mission

#173

Post by ethbro »

nradov wrote: post #172
ethbro wrote: post #171

Earlier quoted context omitted.

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,…

Orbital velocity is no asset. In fact rather the opposite. You can't just start aerobraking. There isn't enough air in orbit for parachutes or wings to have any noticable effect. The only practical way to get out of orbit using current technology is to conduct a de-orbit burn with chemical rockets. Of course that's all pointless because a ballistic missile launched from Earth could accomplish the same mission at a fa…

You absolutely can just start aerobraking if you have maneuverability on the launch vehicle (because it's small, packed with fuel, and limited duration).

Regardless of what orbit you start from, you dip into the atmosphere, deploy your payload from there, voila.

Now anything you dropped has to deal with a furnace of superheated air, and the question of whether it's possible to have control in those conditions, but it's definitely going to de-orbit.

And the atmosphere is going to supply most of the energy, rather than direct retro burns from the delivery vehicle.

Re: Unmanned U.S. Air Force space plane lands after secret, two-year mission

#174

Post by roryisok »

killjoywashere wrote: post #165
roryisok wrote: post #128

Earlier quoted context omitted.

Re-arm with what? Bad advice?

Kinetic weapons? Power supply for electronic warfare sources?

> Kinetic Weapons?

If the US has kinetic weapons in space, I very much doubt they would plan to use them against North Korea. NK is decades behind in military technology, and the US/SK forces would have air supremacy over NK in a matter of hours, with the capability to pummel anywhere in the country with conventional weapons with relative impunity.

If they have them, using them would almost certainly tip their hand to Russia / China etc, and lose them a significant strategic advantage in any future conflict. Trump and his cronies have been talking tough about China (Bannon literally said 'We're going to war in the South China Sea ... no doubt') and while it is a) doubtful that this will happen, given the recent warming of relations with China (mmmm... chocolate cake) and b) in the event it does happen, unlikely to escalate to the use of previously undisclosed super-weapons, it still makes sense to keep this hypothetical weapon secret from larger, more-powerful potential adversaries, just in case.

Also, if they're rearming with Kinetic Weapons it suggests they've already fired a few

> Power supply for electronic warfare sources?

Since you mention a power supply, I'm going to assume you don't mean dropping EMP bombs, which, even if they exist would be more easily dropped from high altitude aircraft, and would likely be less effective against such an outdated military.

I'm going to assume instead you mean some kind of cyber-weapon. The alleged cyberwarfare campaign against NK's ICBM programme most likely takes the form of malware (like stuxnet) introduced through conventional hacking methods or even on-site deployment. Sure, you can send someone a phishing email from space, but it's not any more effective than sending it from an office somewhere.

Re: Unmanned U.S. Air Force space plane lands after secret, two-year mission

#175

Post by pavement »

nradov wrote: post #169
pavement wrote: post #167

Earlier quoted context omitted.

Prove to me that a rocket simply MUST be burnt, to set an orbiting mass in motion. Propellant is a conventional means, but certainly not the sole means. Magnetic induction could eject a slug from an orbiting platform, or inert gases could jettison to induce motion. Burnt fuel isn't a requirement. You insist on a rocket motor. But you just resist the idea of this form of orbital weaponry. A large enough asteroid could…

You are still 100% wrong. Magnetic induction wouldn't be be practical because it would disrupt the satellite's orbit. Inert gasses are too heavy to be practical for the amount of delta V needed. You're just making things up and missing basic physics concepts.

You're imposing constraints where there are none, and declaring physical law as an insurmountable barrier, because you are sourcing all materials involved as terrestrial in origin, and insisting on reusability.

Magnetic induction would also apply opposing forces to the launch satellite, but that doesn't matter if the launch satellite is just as disposable as the slugs that destroy the target.

Inert gases are too heavy, only if the weapons program tries to collect them on the ground and launch them into orbit.

I'm obviously making things up, because this is a system open to invention, given that it doesn't actually exist yet. This concept is less practical, if you operate within existing constraints, using only rocket propellant to boost objects into orbit, and then subsequently de-orbit them.

Game changers emerge, when new ways of operating in space appear. Even if this is "less practical" right now, after the introduction of adjacent technologies, as an existing concept it could suddenly become practical. For example, with the introduction of a space elevator, boosting such a weapons system into orbit is less costly. Then, more of its components become readily disposal at practical values.

I'm not required to operate within existing economic constraints, to consider ideas that are not actually limited by physical laws.

Re: Unmanned U.S. Air Force space plane lands after secret, two-year mission

#176

Post by killjoywashere »

roryisok wrote: post #174
killjoywashere wrote: post #165

Earlier quoted context omitted.

Kinetic weapons? Power supply for electronic warfare sources?

> Kinetic Weapons? If the US has kinetic weapons in space, I very much doubt they would plan to use them against North Korea. NK is decades behind in military technology, and the US/SK forces would have air supremacy over NK in a matter of hours, with the capability to pummel anywhere in the country with conventional weapons with relative impunity. If they have them, using them would almost certainly tip their hand t…

> Also, if they're rearming with Kinetic Weapons it suggests they've already fired a few

That was my point, yes. I'm not sure "fire" is the right word. You can just drop them.

> I'm going to assume instead you mean some kind of cyber-weapon

Cyber? What? If you know some operating frequencies of internal systems or control bands, you can use targeted energy instead of broad-spectrum EMP.

Re: Unmanned U.S. Air Force space plane lands after secret, two-year mission

#177

Post by roryisok »

killjoywashere wrote: post #176
roryisok wrote: post #174

Earlier quoted context omitted.

> Kinetic Weapons? If the US has kinetic weapons in space, I very much doubt they would plan to use them against North Korea. NK is decades behind in military technology, and the US/SK forces would have air supremacy over NK in a matter of hours, with the capability to pummel anywhere in the country with conventional weapons with relative impunity. If they have them, using them would almost certainly tip their hand t…

> Also, if they're rearming with Kinetic Weapons it suggests they've already fired a few That was my point, yes. I'm not sure "fire" is the right word. You can just drop them. > I'm going to assume instead you mean some kind of cyber-weapon Cyber? What? If you know some operating frequencies of internal systems or control bands, you can use targeted energy instead of broad-spectrum EMP.

OK, you obviously know more than me about electronic warfare. But regarding the kinetic, when and where might they have "dropped" them already?
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