747400sp From United States of America, joined Aug 2003, 4147 posts, RR: 2 Posted (8 years 2 weeks 5 hours ago) and read 8709 times:
On the cover of Feb. 2008 Popular Science, shows a new jetliner call the A2, the A2 is Hydrogen Hyper-jet airliner design to carry 300 passengers at the speed of Mach 5. The A2 do not have any windows due to it speed, also due to it's four Scimitar engines it is a clean burning jet. As written in Popular Science, For takeoff, landing and subsonic flight, the A2's Scimitar engines sends intake air through a bypass duct and into a turbine, like a standard jet engine. After reaching supersonic speed, though, the engine redirects air from the bypass duct through the engine core for flight up to Mach 5. Like a ram jet, the Scimitar works by taking in air from the atmosphere at high speeds and funneling (or " ramming") it until it's intensely compressed. At this point, the extremely hot air mixes with fuel and causes ignition. But the Scimitar one-up traditional ramjet design by adding a turbine that compresses the incoming air even further. Ramjets usually can't use turbines because the incoming air is so hot that it will melt the turbine blades. The Scimitar solves that problem by first cooling the air in a heat exchanger using gaseous helium.
So, could the A2 work, and if yes , do you think passengers would want to trade in windows to make a 22 hour flight only 4 hours?
Tdscanuck From Canada, joined Jan 2006, 12710 posts, RR: 80
Reply 2, posted (8 years 2 weeks 1 hour ago) and read 8671 times:
Quoting 747400sp (Thread starter): But the Scimitar one-up traditional ramjet design by adding a turbine that compresses the incoming air even further.
Strictly speaking, that would be a compressor, not a turbine.
Quoting 747400sp (Thread starter): Ramjets usually can't use turbines because the incoming air is so hot that it will melt the turbine blades.
This doesn't sound right to me...the highest temperature in any engine is downstream of the combustor. If the engine can tolerate that temperature there's no reason that the incoming air temperature should be a problem (it just requires that you use turbine materials for the compressor...pricey but possible).
Quoting 747400sp (Thread starter): So, could the A2 work, and if yes , do you think passengers would want to trade in windows to make a 22 hour flight only 4 hours?
In principal, yes, but you're talking about an *enormous* fuel burn, which implies a hydrogen and helium infrastructure that just doesn't exist today as well as significant energy cost. If I had that kind of money I think I'd rather spend 22 hours on my comfy private jet rather than 4 hours on a windowless commercial jet.