I think the industry was thinking of having electric tugs or motors built into the plane to move passenger jets around on the ground to save the fuel used getting from the stand to the start of the runway.

"For a heat engine, thermal efficiency is the fraction of the energy added by heat (primary energy) that is converted to net work output (secondary energy)."

Does thermal efficiency = actual efficiency in the case of jet engines? I find that difficult to believe.

Propulsive efficiency is how good the engine is a converting this energy into thrust. The Concorde's engines were a type where all the propulsion was from the fast gasses exiting at the back, i.e. a turbojet. Efficiency is less than 100% as energy is taken from the gasses to power the engine and not all the gasses exiting the rear usefully push the aircraft forwards.

I don't have the exact number for the Concorde to hand but looking at [1] from my previous post, we can see it was typically around 60% in 1970, but these numbers are likely for (low bypass) turbo fans. These work in a slightly different way where they have more energy in the rotation of the shaft and less in the gasses going out the back. The energy in the shaft drives the big fan at the front which pushes a large volume of air more slowly out of the back. This is to address the problem of the gasses which exit the back but don't usefully push the aircraft forward.

To get the total efficiency of the jet you have to multiply the thermal efficiency by the propulsive efficiency.

edit: changed division to multiplication

Also need to consider combustion efficiency (i.e., the percentage of fuel turned into heat as an input to the heat engine), though for gas turbines this is typically ~99.9%.

Multiply surely? Otherwise reducing the propulsive efficiency would increase overall efficiency