Antonio wrote:
Afterburning is not the point: overall engine-airframe efficiency is.
Let’s just say the thermodynamics of afterburning are really unfavorable. While you’re technically correct, an afterburner starts with such a design disadvantage that it’s unlikely to beat at efficiency an engine more suited to extract the same power with the help of a turbine.
Antonio wrote:
Which one is more efficient?
Without compensating for weight (and especially pax capacity), the comparison is not very relevant.
Antonio wrote:
Afterburning is not the point: overall engine-airframe efficiency is.
I hear you and of course you are right. The discussion I was referring to was Concorde vs the TU144. Both had similar speeds but the TU needed the afterburners on all the time while Concorde did not, giving it the transatlantic range it had. I recall talking to Chris Orlebar (whose Concorde book is quite well known) about this and of course the factor with those two planes was that they were cruising at similar speeds, but the TU is significantly bigger. So yes, it is the overall engine-airframe combination which does the job. This does not change the fact though that in this case, the afterburning the TU needed, also because it’s engines were most probably not strong enough to keep the TU flying without them, caused a massively higher fuel flow.
Antonio wrote:
even on your Mooney, you may have the best engine efficiency at WOT, but depending on altitude and weight, WOT will not be the most efficient power setting of the airframe-powerplant combination.
Absolutely right. To figure out range/efficiency sweetspots for any airframe is something which is a pretty hard work but usually yields very unexpected results :) And WOT hardly ever plays into that where range is concerned, but almost always when speed is. It depends what you are looking for.
Antonio wrote:
Which one is more efficient?
I would say it will depend on which airframe they are fitted on :)
I have to say the Hermeus project looks quite interesting. Scram jet operation is not exactly new, but it also has a lot of potential. I will be watching out for them.
