I work with turbines on a daily basis. Most of them being in the 200,000 hp and up power range. It is critical what speed this machine operates at. If the output is AC, then it would need to be some multiple of 1800, 3600 RPM... For a four pole or two pole generator to get 60 HZ. Otherwise, you would need a reduction gear to get the proper speed to supply a generator. (Most of these smaller units that I have seen run in the 5,000 rpm range). This is done all the time on the smaller heavy duty industrial turbine/generator sets. However, if this genset provides DC power, then turbine speed will control the generator voltage output (Lenz's Law states that the speed at which the magnetic lines of flux are cut, are directly proportional to the voltage induced). So, this VDC could power an inverter with DC input for AC output. Typically, these small turbines are designed to run at a fixed speed as they do not have variable inlet guide vanes for surge protection. Lots of complicated reasons normally associated to the limitations on proper compressor flow in such a manner that the compressor is not "surged" (a compressor back flow condition that is rather distractive, and that liberates blades). Keep in mind that turbines have a very large, multi stage compressor, with only 2 or 3 turbine stages that actually produce the power. The compressor part of the turbine will consume no less than 50% of the turbine power output.
While in college, way back in the early 70's, I had the opportunity to work with a bit of old military equipment that all ran on 400 HZ power, this stuff was mainly com, or radar gear. Most of these sets are made to provide output power to a shaft, so trying to use it strictly for thrust may be a problem with exhaust gas temperature (1000 deg F +). Used on a motor vehicle, this would toast the person's vehicle who is tailgating you.