Goal

Can anyone think of a good way to use ground based lasers to increase a rocket motors output?

I found some stuff about vasimer I using radio frequency to accelerate plasma. Could a ground based laser strike a solid target to generate plasma and another beam of coherent radio to accelerate the plasma?

Sigma, i suspect you've meant this. practically dead conception:
1. laser beam is significantly violated by Atmosphere.
2. thrust decreases with altitude.
3. problems to stabilize motions of spacecraft.
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Yes, trajectory could be stabilized with axial rotation, but, frankly to say, it reduces acceleration.

With Micro mirror arrays and the same tech used to fry people via a giant 747
mounted laser cannon and distort the beam so.the atmosphere focuses it on target.

By using a propellent that can be enhanced via laser rather then atmosphere via ground based power and mems you could leave much of your weight on earth.

Sigma, if you even could get powerful enough laser, what about problem to not damage rocket, huh??? laser has to be focused very precisely, but Atmosphere makes it being too hard + angular velocity gone wild

You don't use the laser or whatever to directly "push" the vehicle. That was what was found to not work back in the 80s-90s. Far to many detail problems. Instead you are transmitting power to the vehicle which then transfers the energy to your propellant. Either by electric drive or thermal heating. Millimeter wavelength EM is more efficient for this purpose than laser. Still lots of detail technical problems that make it impractical today.

James, ye're hella right: off-ground start needs the power source about 1-10MW 4 winged vehicle with total weight up to 200 metric tonnes. at nowdays, these parameters can be gotten with nuclear reactor + mp-ramjets. furthermore, reactor could be even lesser than MW-class bcoz mp-ramjets need the lowest Isp's, really trashed ones