A new Boeing ...

[Mark Allen M]

http://video.boeing.com/services/player ... 1877361001

[wendovertom]

Interesting! Although I think that someone (Boeing) should bring back the XB-70 but as a passenger plane. It would take a little redesign to accomodate 200+ passengers but it could be done. The principle of 'compression lift' could be better utilized with modern high speed computers and IMHO if you built them for Pacific routes who would care about the sonic boom??

Tom P.

[daviemax]

Among the many technical questions is that of how the engines are properly aspirated at 65,000 feet. It isn't clear that normal turbocharging will be adequate.

[CAPFlyer]

According to several websites, it uses multiple turbochargers to both reduce IR signature and provide sufficient air.

Also, remember that most automotive engines tend to be more efficient via the use of electronic engine management and direct fuel injection, which greatly improves efficiency over the mechanical throttle body injection used by most "advanced" aviation piston engines.

[wendovertom]

Plus according to the video these are not 100LL engines - They are hydrogen fueled and I would imagine that the fuel makes a big difference in the performance.

Tom P..

[daviemax]

Hydrogen has an octane rating of 130 or higher - essentially equivalent to the best aviation gasoline - allowing for relatively high compression ratios. In addition, a Hydrogen-fueled engine can run at very lean mixtures - which theoretically contributes to range of the Phantom Eye but does also raise further the issue of charge air availability. Multiple turbochargers would of necessity require high exhaust gas energy to function. How Boeing balanced this equation is still a major question. Bear in mind that the air density at 65,000 feet is about 7% of that at sea level (source: Public Domain Aeronautical Software). Condensing the charge-air won't be a problem (due to the temperature at altitude) but creating the requisite volume of charge air will be. How Boeing did this must surely be a major part of their intellectual property.