Diesel in NASA's hydrogen fuel cell plane

[freebeard]

I find the airframe more interesting than the powerplant[s].

Once the X-57 gains altitude and velocity, the 12 lift motors shut down and the propellers fold back into a more aerodynamic position.

Nice if you can make that work reliably. They should be shaped like whale tubercles to help with span-wise flow when they're off.

That's a sweet all-flying elevator.

[cRiPpLe_rOoStEr]

Originally Posted by jamesqf

I've sometimes thought that fuel cells running on sugar would be a better solution, as it skips the whole conversion to ethanol step.

Not sure if that would be so easy, since a liquid would flow more effectively. Maybe molasses?

[jamesqf]

Originally Posted by cRiPpLe_rOoStEr

Not sure if that would be so easy, since a liquid would flow more effectively.

Obviously you'd have a sugar solution. Molasses probably not, because of all the impurities that give it its flavor. Maybe high fructose corn syrup, though.

[cRiPpLe_rOoStEr]

Originally Posted by jamesqf

Maybe high fructose corn syrup, though.

That would be interesting to say the least, but due to the lower viscosity (and therefore an easier flowing) I'd still believe ethanol to be more commercially viable as a fuel.

[freebeard]

The first diesel motorcycle I ever saw claimed you could run it on bottles of vegetable oil from the supermarket.

[cRiPpLe_rOoStEr]

Originally Posted by freebeard

The first diesel motorcycle I ever saw claimed you could run it on bottles of vegetable oil from the supermarket.

That military one from Hayes or some random custom built? Indirect injection is more suitable to use veg oil as fuel, and surprisingly it actually gets more fuel-efficiency than running on regular Diesel fuel.

[freebeard]

I don't recall. It was maybe in the last century, but it was billed as a world first commercial diesel motorcycle at the time.

[cRiPpLe_rOoStEr]

There had been at least one variant of the Royal Enfield fitted with a locally-developed Diesel engine (not sure if designed in-house or outsourced to Greaves Cotton, the largest independent engine supplier in India), but I'm not sure about its suitability to straight vegetable oil usage.

[Xist]

NASA allegedly designed a super-efficient plane with one giant engine behind the plane. But wait! There is more! To power the engine, they put generators on the wings!

Windmills don't work that way?
NASA's New Plane Design Could Save Fuel and Money

[freebeard]

The engineers also added generators to the wing-mounted turbofans, and the electricity generated by these engines is used to power the tail-mounted one. This means that the rear turbofan that provides much of the plane's thrust doesn't require any fuel to operate.

I think it's unfortunate wording. The tail location may have some advantage over the usual stuck-in-the-rudder solution. It may rely on new carbon-fiber fuselages that have less attached turbulence.

But starting at a high altitude, at high speed, there is a lot of energy to be regeneratively captured descending to rest. Which can be reused by the efficient tail engine back at cruise, after the extra wing engines idle back after the climb.