In the future any point on earth will be able to be destroyed by satellites. Having any unit on the ground is suicide.
A satellite will be able to pinpoint and destroy any target on the face of the planet. Satellites will also have to be built to protect each other from satellites built to destroy other satellites, or ground based attacks.
Anything you put into space that can shoot the ground can also be shot at by things on the ground. Anti-satellite rockets already exist (see: Chinese & American ASAT tests a few years back), and in the future, large laser arrays will be able to kill them dead.
Laser satellites vs ground based laser installations put the ground at an advantage, because in space there's no atmosphere to cool you down, so you have to use expensive (and limited) specialized coolant to keep firing, or you have to wait for hours with big radiators exposed to enemy fire in order to passively cool down. Additionally, something on the ground didn't have to be launched into space, so it's innately cheaper, and for the same price, you can get a significantly larger and more powerful array. Things on the ground that are mobile can preserve uncertainty of location. One good platform for this is a submarine the size of one of the large SSBN's, but with it's guts replaced with a big solid state laser. Satellites can never know where it is, but it can simply surface and fire it's own weapons at them, then retreat underwater to evade counter-fire.
The ground is swarming with things that aren't military targets, making identifying the enemy somewhat challenging depending on its exact location. In space not-so, the ONLY things in earth-orbit are the moon (easy to pick...) and man-made satellites. You have a database of the positions of friendly satellites, so you know which ones are valid targets. Satellites are easily predictable because they move in orbits, so...
In conclusion, YES, orbital weapons are viable, however ground-based ASAT weapons are at an advantage, and military assets on the ground are not going to be "obsoleted" by them.
To be honest, i think I'll see GDR being a effective military weapon way before satellites even having a chance.
Naw, Satellites are expensive but at least feasible, whereas GDR is something that has no meaningful advantages over the competition, is VERY expensive and is a significantly larger target.
Rods From Gods is a low-tech way to get orbital bombardment down-pat, and would be quite terrifying for whatever is being targeted by it. Essentially, it's a multi-tonne tungsten rod the size of a telephone pole that simply reenters the atmosphere and crashes into your target.
E(k) = 1/2 m v^2, so they deliver a LOT of energy.
As far as "the next big upgrade" what will trump tanks in future combat, well their is only so many options and I can gaurentee one of them is not "just more tanks, no technology will ever trump a tank"
It's not that current tanks are the best thing ever, it's that tank chassis are the optimal shape for armored fighting vehicles. Their armor and weapon will change in the future, but their general form will not, ergo they will still be considered "Tanks", even if they're shooting lasers and railguns.
The attack helicopter has already "trumped the tank", as far back as the 1970's. But tanks are still highly effective once you have gained air superiority, because enemy infantry and light vehicles cannot easily deal with them.
- Androids/Cyborgs, man sized combat robots or combat chasis for an infantry soldier, heavy support infantry if you will, who needs large tanks when a man sized robot with a mini-gun/cannon/rocket launcher can do it all.
Rocket launchers can and are already carried by infantry, but that didn't make the tank useless. Androids / Cyborgs are going to step out into the open and get plastered by the 120mm smoothbore gun or any one of the three machineguns that an M1 Abrams mounts.
Man-sized robots are not intrinstically a bad idea, they just aren't tank-killers. They are good for killing INFANTRY, since they are in the same role as infantry but have superior arms and armor.
- Walkers, e.g the GDR these beomoths will be capable of great firepower, from bi-pedal mechs to tripod walkers to insect like 8 legged beasts, perhaps the future will be on large legs to cover ground quickly as apposed to wheels.
Have you been reading this thread?
- Hover Technology, while some may argue wheels are better than legs, why go back to legs, I can assure you hover technology will be better than both, why touch the ground at all when your infantry/tanks can float off the ground allowing them to travel over any terrain at the speed. Hover Tanks would be a good replacement for the modern tank, however current technology makes flubber like flying cars a bit hard to achieve
You're trying to propose plausible future alternatives to GDR and you come out with hover-tanks, something that have no grounding in science what-so-ever?