Dilandu wrote:jvilnis wrote:How do yoou defeat a race of Aliens who control high orbit and can throw rocks at you down the gravity well?
Unless you can somehow get up to defeat their ships you are always going to be at a enormous disadvantage.
Er... I could have a VERY, really VERY BIG laser array on the planet, and some collapsible re-targeting mirrors could be launched on rockets to focus the beams after they left the atmosphere.
Good thing about planetary artillery - it could be of any possible size, energy requirements and could generate as much heat as it needed. We have oceans to cool it, mountains to cover it, and a lot of space for power generators.
Of course, it wouldn't help against long-range ballistic attacks (albeit if they aren't relativistic, the planetary laser could still be useful in diverting projectiles by ablation), but the ships on high orbits would be a perfect melting points)
Reminds me of a thought I had a few years ago.
Back during the 1st underground US nuke test, the test nuke was placed at the bottom of a deep (200m?) vertical shaft and covered by what was essentially a massive manhole cover. when the test occured, the manhole cover was caught midair atop a pillar of flames in 1 frame of highspeed film, and it's wreckage was never found. Disagreements among the project scientists and specialists raged over what happened to the cover, with some believing it was turned to plasma in the fireball - others that it had been imparted escape velocity and had left earth forever.
In the last 70s, after spacetrack radar had been turned on, an un-accounted for object in a fairly high orbit was "tentatively identified" as the cover, but only because it is the rough size of the cover, and no other known space trash fit the trajectory.
And that was an accidental by-product of the test.
It would be an exercise in math, but it would be possible to build single use "launchers" in a cluster, designed to smack a capitol ship in orbit. Use "hardened" launch tubes and specially designed covers to maximize success.
Unfortunately, you couldn't test the system, unless it was built before the attackers arrived, and the whole concept might be a 1 shot wonder, as after the 1st launch, the attackers may have sensors capable of detecting additional launch tubes, no matter how well disguised.