MG23
And SABRE is the Skylon engine.
Yes, I am aware of this. I was pointing out that this kind of technology wasn't relegated only to SSTO's, but hypersonic air-breathing aircraft as well.
balsa model
Absolutely! If it cost less to produce a new expandable one than to recover and overhaul a reusable one that carries the same payload, then Yes!
And this goes to show why obsessing on economics is not always the best course of action. If we followed our lives strictly by economics, old people, sick people, and mental ill people would probably be euthanized -- after all it costs a lot of money to keep these people alive and take care of them
they sure seem to be pushing the edges of where airbreathing engines can go.
They are very advanced concepts. If I recall correctly, McDonnell/McDonnell-Douglas did some research with some kind of engine-precooling back in the 1960's. It had to do with cooling the airflow to keep the turbine temperatures within limits, and maximizing ram-compression by cooling and densifying the air. I don't know the exact details but a professor who worked for McDonnell/McDonnell-Douglas named Paul Czysz did make mention of such a proposal and remarked that it was similar to Skylon (though I don't know exactly how similar -- figurative or literal)
IIUC, hellium is used as a heat circulation fluid: it moves the heat from the intake air to the cold "sink" of LH2. It won't boil until you get the whole content of the LH2 tank above its boiling point.
Okay, I thought the heat would be transferred into the fuel heading towards the engine's combustion chamber (On this note, could you use a pre-cooler using liquid-helium, transfer the heat into LH2 heading towards the engine, vaporize the LH2, and use the expansion of the H2 to drive an expansion turbine?)
I like their attempt at forecasting of costs, on their web page. There is an estimated R&D cost and eventual passenger ticket prices.
How much would the R&D cost run, and how would the passenger ticket process compare to the Concorde?