Orbital Lasers

[Flyndaran]

Your initial post was about TL 9 not TL 9/10^.

Once you start invoking superscience for the aliens, you might as well invoke it for the primitive humans, right?

What interesting advantages could a TL 8^ Earth have?

[AlexanderHowl]

I merely mentioned in the first post orbital lasers are possible at TL9, meaning that any TL9+ civilization (or TL9^+ civilization) would have them. Humans do not have superscience in this scenario because we do not have superscience, but the same would not apply to aliens.

Interstellar travel without superscience would be highly unlikely before TL12, and humans would not have any chance against a species with TL12 biological sciences. They would only need to drop a few dozen plague metamorphic viruses to transform humanity into nonsapient animals. Paradoxically, humans need aliens to have superscience to have any chance of survival.

[malloyd]

Originally Posted by Rupert

ICBMs don't have the reach to get to geosynchronous orbit altitude, so far as I can tell.

Maybe. The 10.3 km/s you need to throw something as high as synchronous orbit is higher than the 7.9 km/s you need for a grazing orbit that will let you hit something exactly opposite you on the planet, so it's theoretically overkill for an ICBM. But then ICBMs will presumably be designed with enough extra to cope with drag and their own gravity losses, and often have multiple warheads you could remove all but one of if you goal is just throw something as high as you can.

It's not implausible some high end ICBMs could hit something in synchronous orbit. Especially since by now everybody who can build ICBMs *has* to have done some sort of analysis of how they would kill somebody else's satellites if they absolutely had to.

[AlexanderHowl]

ICBMs lack sufficient delta-v to maintain LEO, so they could never reach GSO (the best ICBMS can reach a ballistic height of 1,000 km, GSO is over 30,000 km distant). Now, there are some rockets that can reach GSO, but they require weeks of preparation, and they would tend to have only enough delta-v to make up the difference between LEO and GSO (4.33 km/s). It would take around two hours for the warhead to get to GSO, assuming that the orbital spacecraft does not blast the launch cite, giving it plenty of time to get out of its ballistic path (if it has a 1g acceleration from a reactionless engine, it can just move to another orbit without any trouble).

Honestly, I think the best policy would be to appear inoffensive and submissive when the aliens are in GSO. If the aliens do not think that humanity is a threat, they might just take out the satellites and leave after the construction of their mining platforms and military base. Since humanity would now know that reactionless engines and FTL were possible, it could try to replicate the process from first principles. Of course, it would need to adapt to existing without satellites until it was capable of making reactionless engines, but it could adapt.

[Rupert]

Originally Posted by AlexanderHowl

ICBMs lack sufficient delta-v to maintain LEO, so they could never reach GSO (the best ICBMS can reach a ballistic height of 1,000 km, GSO is over 30,000 km distant).

Actually, some ICBMs can put warhead busses into LEO, and repurposed ICBMs have often been used to launch satellites. I suspect some of the biggest ICBMs, of which the Russians still have a few in service, could reach GSO altitudes with a reduced payload. However, they'd be moving so slowly that frying them as they approach would be fairly trivial.

Assuming the attacking spaceship is properly hardened against EMP and so on in GSO it should be quite safe from any attempt we could make.

Which is another thing - with such a ship in orbit we'd lose all satellites whenever they felt like removing them. They could use their lasers if they wanted to remove only a few, or just fire a few nukes set to detonate 1000km or so up, so the radiation and EMP will fry everything (with a side effect of frying everything on the ground as well).

[Anthony]

The fact that we can theoretically get stuff to geostationary orbit does not mean we'd have any realistic chance of killing an orbital laser, since it's perfectly capable of shooting down missiles and also can probably move. In practice, unless you can trick the aliens into carrying a bomb up with them, you just treat it the way you treat any sort of air superiority -- you hide from it.

[Daigoro]

Originally Posted by malloyd

Maybe. The 10.3 km/s you need to throw something as high as synchronous orbit is higher than the 7.9 km/s you need for a grazing orbit that will let you hit something exactly opposite you on the planet, so it's theoretically overkill for an ICBM.

What kind of delta V do recent hypersonic missiles have?

[Rupert]

Originally Posted by Daigoro

What kind of delta V do recent hypersonic missiles have?

A couple of kilometres a second.

[AlexanderHowl]

Most of them actually use powered down orbital rockets (allowing them to increase the payload). The ones that the Russians have been bragging about use thirty year old repurposed rocket technology, which is why the Pentagon is not worried, as they would have poor accuracy compared to Russian ICBMs The reason why the US has not seriously invested in the technology is that ICBMs are already quite capable of hypersonic delivery of nuclear weapons.

[Rupert]

The US expects to have air supremacy, and thus be able to use conventional aircraft and/or cruise missiles to bomb or nuke anything it pleases. The Russians have never had this luxury, and thus have always built faster and longer ranged 'cruise' missiles than the US has.


We aren't really looking at missiles that would replace ICBMs, but ones that fill the medium/intermediate range slot, for theatre and anti-task force use. The Russians are waving them around because of suggestions of ABM systems being moved into Europe. It's Pershing IIs vs. SS-20s over again.