Future Plasma-Scramjet engines: If/how they could be used in the launching of spacecraft

Question

Recently I took a look at this paper:

“Electrically Driven Supersonic Combustion”, Energies 2018, 11, 1733; doi:10.3390/en11071733 https://www.mdpi.com/1996-1073/11/7/1733

It made me think about how this might be used as a stage for a rocket that could bring it to a very high velocity, and a sub orbital trajectory. From what I understand this could allow for a much smaller first stage as well as a second stage that could build up a good deal of velocity at a lower altitude without the need for oxidizer along with less propellant. (Please correct me on any misunderstandings or ignorance on that.)

If this Plasma Scramjet was capable of being used as a stage for a spacecraft what would it look like? For example, could a smaller booster be used to accelerate it up to its working velocity and altitude? after which the Plasma Scramjet would be able to add accelerate the craft to a higher speed at a shallower angle. If this was done; (Hypothetically, not necessarily if this is simpler or cheaper) how would the actual craft have to be designed differently from a conventional rocket?

On an extra note, if anyone wants to answer a related question. Does this engine have the potential to make sub-orbital high speed commercial flights financially viable? Could we expect to have access to high speed transcontinental flights in minutes rather than hours in the near future?

Answer 1

A number of the sub questions are answered across the air launch tag category - short version being for any useful rocket your lift aircraft is massive and very complex, some napkin math suggests a falcon 9 first stage equivalent aircraft being sports stadium sized with the details just changing 'which sport'.

Looking at what plasma ignition does, it is solving just one of many problems with hypersonic flight, allowing you to sustain stable combustion at higher speed/altitude combinations. It does NOT solve intake geometry, heat removal or low speed issues and it does so consuming massive amounts of energy. kW and MW are mentioned in the paper alongside 2 percent of combustion energy. This is both a 2% performance hit and a requirement to generate massive amounts of electrical energy in your rocket plane, possibly 100MW which is decent terrestrial power station. Worse this is into an aggressively varying load (it is arcing BY DESIGN) so a challenging design where most of your failure modes involve an explosion, either in the electrical system or the suddenly unstable scramjet.

So at time of writing it is an interesting method to confront one scramjet design challenge, but only one challenge of many so premature to talk design details of an actual vehicle using it.