Why not just use the simple solution? Shoot a gun at the sky! I oversimplify, as it's obvious that a regular handgun round won't go into deep space, but all you need is a device that will shoot large aerodynamic projectiles at a high speed. This would be relatively cheap (quite a bit cheaper than massive laser arrays), and there wouldn't be much they could do about it, short of starting to throw rocks at it. But if you make enough of those installations, in a matter of minutes, at least one will hit the enemy ship hard enough to cause a hull breach. This velocity doesn't have to be very high, especially if an explosive is mounted on the projectile, or just a sharp, durable tip.

The only major concern about this is that they may start to bomb out the installations on the ground, but, as mentioned by Jim2B, there's enough clutter on Earth to hide the installations, until the moment of firing. In fact, the entire acceleration mechanism could be kept deep underground, with only a small bit poking out. This would be effectively invisible from space.

Why not just use the simple solution? Shoot a gun at the sky! I oversimplify, as it's obvious that a regular handgun round won't go into orbital height, but all you need is a device that will shoot large aerodynamic projectiles at a high speed. This would be relatively cheap (quite a bit cheaper than massive laser arrays), and there wouldn't be much they could do about it, short of starting to throw rocks at it. But if you make enough of those installations, in a matter of minutes, at least one will hit the enemy ship hard enough to cause a hull breach. This velocity doesn't have to be very high, especially if an explosive is mounted on the projectile, or just a sharp, durable tip.

The only major concern about this is that they may start to bomb out the installations on the ground, but, as mentioned by Jim2B, there's enough clutter on Earth to hide the installations, until the moment of firing. In fact, the entire acceleration mechanism could be kept deep underground, with only a small bit poking out. This would be effectively invisible from space.

Furthermore, you have to consider the "rock-paper-scissors" of aerial warfare:

Ground anti-aircraft installations beat fighters (usually, or at least are armored enough that fighters can't do much about them)

Bombers can reliably destroy ground installations, assuming you have enough so that a few can come close enough that if they are shot down, the explosion of their contents once it hits the ground it is still close enough to assure destruction of the target.

Fighters can reliably destroy bombers, as bombers are meant to be anti-facility, not anti-plane, and fighters are designed to be anti-plane.

Thus, a small force of fighter jets, even available by today's technology (though it depends how high they are) should be able to make it high enough to attack the "bombers", as fighters CAN make it to orbital height (they just need to get enough speed and then pull up). All you need is one or two fighters to make it within firing range, and then they fire everything they have at the bomber, which probably would be enough to breach the airtight hull. If that fails, ramming the ship at full speed while simultaneously detonating all the on board missiles would almost certainly be enough.