I know there is already a thread about the Hale plane, but this doesn’t imply the propulsion system:
Here I found a very interesting paper on the engine and especially the turbocharging concept:
The key factor for ultra-high altitude engines is the specific air consumption, that’s the main reason why they decided to choose an Otto engine over a Diesel, despite the higher fuel consumption. This paper was written in 1991, Diesel technology and also turbocharging has very much improved since then. For less extreme height (see the Otto Celera) a Diesel engine would be surly the better choice. I don’t agree with them in the point, that Diesel engines have higher cooling heat, this is definitely not the case (only about 15 %). Maybe they used pre chamber Diesels as reference which were still the norm in smaller engines these days.
Turboprops have been ruled out because of the much higher air consumption, something which has been discussd allready in this thread:
Interestingly they choosed a two-stage design for much higher flight heights than the Otto Celera.
Here I found a very interesting paper on the engine and especially the turbocharging concept:
The key factor for ultra-high altitude engines is the specific air consumption, that’s the main reason why they decided to choose an Otto engine over a Diesel, despite the higher fuel consumption. This paper was written in 1991, Diesel technology and also turbocharging has very much improved since then. For less extreme height (see the Otto Celera) a Diesel engine would be surly the better choice. I don’t agree with them in the point, that Diesel engines have higher cooling heat, this is definitely not the case (only about 15 %). Maybe they used pre chamber Diesels as reference which were still the norm in smaller engines these days.
Turboprops have been ruled out because of the much higher air consumption, something which has been discussd allready in this thread:
Interestingly they choosed a two-stage design for much higher flight heights than the Otto Celera.
