Electric "scram" jet

[Idobox]

From what I understand, one of the major difficulties with building a scramjet is that it is very difficult to mix and burn the fuel properly without slowing down the air too much. Also, the simple fact that the fuel has mass and needs to be accelerated is an issue.

Now, if you get something that looks a lot like a scramjet, but use an electric arc to heat the flow, you don't have all these pesky mixing issues, and you can even get limited magnetoplsmadynamic thrust (extremely efficient at low pressures, works like a thermal arcjet at higher pressures).

Spontaneously, it looks like you could get better performance, and the weight of a microwave receptor should be comparable to the fuel tanks you don't need anymore. But nobody seems to be actively working on it, why?

[Aghanim]

There isn't any compact electric energy source, yet. And no, real life microwave receiver doesn't work like in KSPI. Delivering several megawatts of power without using focused beam requires large receive array, which well, is too large to fit at the aircraft

[Idobox]

A megawatt rectenna with a large gain (over 30dB) could fit easily in a small rocket, but you would need a very large emitting antenna to get a decent transfer efficiency.

An antenna array of 1m² working with 1mm signal can have a gain up to 62dB.

A 10x10m emitter antenna would have a gain up to 82dB, at a 50km distance, you would have a .5% transmission efficiency, so you would need to emit 500MW to receive 1MW. Taiwan has a radar 30m in diameter, and there are commercially available multi-MW klystrons.