[World Building] A Future History of Space Force

[Varyon]

Originally Posted by Polydamas

(did those missions have crew with specific qualifications?)

I believe most astronauts had Secret or even Top Secret security clearance or similar, as by necessity they had access to national secrets involving the technology in their craft. Having that level of clearance automatically means you've been vetted as someone who won't spill the beans about the secrets you learn as a result of it, and thus can be similarly relied upon to not tell anyone that you dropped off half a dozen spy satellites during your mission. That seems like the only qualification required to undertake such a mission that might not have been required to be on any mission involving the deployment of satellites.

Originally Posted by Verjigorm

Unguided projectiles are not going to be very effective past very short distances and very close relative speeds. Rendezvous in orbit is not easy, not by a long shot, and it gets harder if the target is capable of counter maneuver. Muzzle velocity for chemical slug throwers is pretty low, around 1 to 1.5km/sec in terms of deltaV, which isn't a lot of budget to close with the target. Even something like a 120mm cannon is only pushing around 1.75 km/sec.

At around 2.7ish km/sec, kinetic energy of a mass is essentially equivalent to the detonation of an equal mass of high explosive. A shipkiller projectile just has to be a solid, inert mass, moving at several kilometers a second. So a missile that's capable of mid course correction *and* a final boost to kill phase is going to out perform guns by substantial margin.

I think the idea is to have a wide cone of effect. An impactor needs to directly hit the target to do anything. Something that explodes shortly before hitting the target will instead spread out into a cone of smaller high-velocity impactors, increasing the chance of a hit (the individual hits won't be as powerful as the original impactor hitting, but you don't need many of them to take out a typical spacecraft/station/satellite). In theory, something with a turret-mounted slugthrower or thirty could instead spit out a much wider cone of bullets than the proximity-detonated missile could. I'm not certain it actually would be able to do so effectively, however, and any energy added on from firing these guns would probably be less than what you'd impart to ~half of the fragments by using the mass needed for the guns and their ammunition for an explosive instead.

[Anthony]

Originally Posted by Varyon

In theory, something with a turret-mounted slugthrower or thirty could instead spit out a much wider cone of bullets than the proximity-detonated missile could.

I can't think of any situation in which that is an asset. There's an upper limit on useful cone size, beyond which you are reducing hit probability rather than increasing, and a missile can hit that limit easily.

[Varyon]

Originally Posted by Anthony

I can't think of any situation in which that is an asset. There's an upper limit on useful cone size, beyond which you are reducing hit probability rather than increasing, and a missile can hit that limit easily.

Yeah, hence my note that I'm not certain it actually would be able to accomplish this effectively (by "effectively" I meant "give a wider cone that isn't spread so thin as to make hits less likely"). Guns on a reusable drone might be feasible, but I think it would be safer to assume that anything that gets close enough to actually use conventional guns is unlikely to survive the event.

[Anthony]

The core problem with reusable is that you need several times the delta-V to make a missile reusable. A single-shot missile just needs to accelerate. A reusable platform needs to accelerate, then decelerate if it misses, then have enough left over to return to the parent.

That's also the problem with sending a spaceship in the first place -- if all you need to do is deliver a payload, a bus missile is much smaller and cheaper than a warship.

[Polydamas]

Originally Posted by Verjigorm

Unguided projectiles are not going to be very effective past very short distances and very close relative speeds. Rendezvous in orbit is not easy, not by a long shot, and it gets harder if the target is capable of counter maneuver.

If the battle is in Earth orbit, then any space-based weapons will be overwhelmed by missiles launched from earth as soon as a belligerent rotates into the right position and its missiles reach orbit. At least one nation has destroyed an object in Earth orbit with an anti-satellite missile whereas everyone's anti-satellite satellites, drones, and ROVs are secret and untested.

Lots of discussions of the likely merits of various weapons in space with a lot more evidence, thought, and math than in this thread, just saying (eg. Children of a Dead Earth, Attack Vector: Tactical, Project Rho).

[Anthony]

Originally Posted by Polydamas

If the battle is in Earth orbit, then any space-based weapons will be overwhelmed by missiles launched from earth as soon as a belligerent rotates into the right position and its missiles reach orbit.

That's not clearly true; launch systems may have fairly limited throughput, even if total storage is far higher.

[Verjigorm]

Originally Posted by Polydamas

If the battle is in Earth orbit, then any space-based weapons will be overwhelmed by missiles launched from earth as soon as a belligerent rotates into the right position and its missiles reach orbit. At least one nation has destroyed an object in Earth orbit with an anti-satellite missile whereas everyone's anti-satellite satellites, drones, and ROVs are secret and untested.

Lots of discussions of the likely merits of various weapons in space with a lot more evidence, thought, and math than in this thread, just saying (eg. Children of a Dead Earth, Attack Vector: Tactical, Project Rho).

Earth based missile systems work, but have the problem of needing to provide enough deltaV to get into orbit, and then intercept the target. They need to be pointed in the correct distance and be targeted. If a vessel maneuvers on the opposite side of earth from your land-based sensors, it could change it's orbit enough to approach from an unpredictable orbit, and it's missiles don't have to use nearly as much energy to get to the target.

A space based missile platform can target a lot of orbital infrastructure. Where an earth based missile would need around 8 to 9 mps to reach a GEO or EML1 target, a LEO based system can do that with three or less MPS. An excess of deltaV will be extremely useful for any sort of mission, whether you are attempting to get close to the target to interfere with it's comms or intercept it.

This is going to heavily influence the cost of the missile. Let's just use spaceships design as a rough benchmarking system: a missile with 18 fuel tank systems, 1 engine and 1 command center can have up to 6.75 mps of delta-v. This is enough to reach LEO and have a substantial amount of maneuver left over, but it can't reach higher or more distant orbits. A missile in LEO could target launch to *mars*(whether it is gonna survive the 9 month trip and be effective is a different story), as well as being able to intercept pretty much any target in cislunar space. To be able to target higher orbits, an earth based system would need to use staging, which increases the mass(and cost) of the missile substantially.

[Polydamas]

Originally Posted by Varyon

I believe most astronauts had Secret or even Top Secret security clearance or similar, as by necessity they had access to national secrets involving the technology in their craft. Having that level of clearance automatically means you've been vetted as someone who won't spill the beans about the secrets you learn as a result of it, and thus can be similarly relied upon to not tell anyone that you dropped off half a dozen spy satellites during your mission. That seems like the only qualification required to undertake such a mission that might not have been required to be on any mission involving the deployment of satellites.

My thinking is that since 1815, probably 1% of what oceangoing navies do is battling other oceangoing navies and land-based air forces. And battles in space are unlikely to make good stories. So maybe this thread should focus on what military personnel are doing in space that you could tell adventure stories about?

I think GURPS Spaceships assumes that chemical guns launch little missiles which can correct their course towards an evading target.

[Verjigorm]

Originally Posted by Anthony

The core problem with reusable is that you need several times the delta-V to make a missile reusable. A single-shot missile just needs to accelerate. A reusable platform needs to accelerate, then decelerate if it misses, then have enough left over to return to the parent.

That's also the problem with sending a spaceship in the first place -- if all you need to do is deliver a payload, a bus missile is much smaller and cheaper than a warship.

I imagine early "warships" in space will use smaller payloads that can perform missions, and the warship will largely be a transport system for those smaller payloads. Rather than strapping cannons and missiles to a Starship, I suspect we will see Starship deploy a swarm of smaller space craft that can intercept targets on their own.

I say intercept, because I suspect Kessler syndrome will be an operational constraint, just as modern military operations are constrained by collateral damage. The nations that have demonstrated ASAT capabilities also have substantial space assets, and clear intentions to expand those assets. Shooting a rival's satellite is great, but if the debris field from that ends up impacting your own orbital assets, that's a no bueno. So I strongly expect that newer generation anti-sat/anti-orbit weapon systems will attempt to intercept targets, grapple them, and then use their remaining fuel to alter their orbit. Again, I've mentioned this could be dual-use, used for targeting space-junk as well as rival space craft.

[Polydamas]

Originally Posted by Verjigorm

This is going to heavily influence the cost of the missile. Let's just use spaceships design as a rough benchmarking system: a missile with 18 fuel tank systems, 1 engine and 1 command center can have up to 6.75 mps of delta-v. This is enough to reach LEO and have a substantial amount of maneuver left over, but it can't reach higher or more distant orbits. A missile in LEO could target launch to *mars*(whether it is gonna survive the 9 month trip and be effective is a different story), as well as being able to intercept pretty much any target in cislunar space. To be able to target higher orbits, an earth based system would need to use staging, which increases the mass(and cost) of the missile substantially.

Someone already had to spend the delta-V to get the missile into orbit, the only question is whether you launch in advance (and keep it functioning and orbit-corrected for years or decades without maintenance) or during hostilities. Remember the orbiting bombs in Heinlein's Space Cadet? It turned out to be much more practical to keep the ICBMs on earth. These days there are treaties against militarizing space so keeping the weapons on the ground until someone breaks the treaty has diplomatic advantages.

I suspect there are a few dedicated weapons in orbit right now (or armed modules on satellites with other purposes) but that they would be greatly outmassed by ground-based missiles if a country with a space program started shooting at another country's satellites.

There is nothing stopping a launch vessel from releasing a smaller craft or swarm of craft which maneuver to intercept a target or targets in orbit using their full load of fuel.

Edit: Wikipedia https://en.wikipedia.org/wiki/Anti-satellite_weapon (list of known tests)
https://en.wikipedia.org/wiki/Outer_Space_Treaty (no WMDs in space, no testing weapons on bodies beyond earth, not sure what other laws and informal agreements exist but people have complained about ASAT tests because of the risk to other satellites)