Comments on: A power-to-weight ratio of 10 screams possibility

By: Jim

Jim — Wed, 16 Nov 2022 20:36:46 +0000

Let us wonder indeed!

By: Altitude Zero

Altitude Zero — Wed, 16 Nov 2022 19:41:04 +0000

“There were nuclear-powered aircraft in the fifties.

Are we to believe that there are briefcase nukes but not briefcase nuclear reactors?”

As I recall, back in the 1960′s NASA developed a desk-sized nuclear reactor for Project NERVA. I wonder what ever happened to it?

By: Michael van der Riet

Michael van der Riet — Wed, 16 Nov 2022 12:37:23 +0000

Another problem with the propellor is that the rotational airspeed of the blade increases exponentially from root to tip. Those unfortunate enough to live near military flying schools that operated the T-6 Texan will remember the terrific roar that the blade tips made as they broke the sound barrier, even at modest airspeeds for the aircraft as a whole. Nor was it a pleasant experience for the pilots.

By: Michael van der Riet

Michael van der Riet — Wed, 16 Nov 2022 12:25:50 +0000

@Wilbur Hassenfus, absolutely! If a humming-bird were scaled up to twice its size, it would be unable to fly. Humans scaled up two times would collapse under their own weight. Even the balsa-wood gliders that I played with as a child would as full-scale aircraft be far too heavy to take off.

By: Jim

Jim — Wed, 16 Nov 2022 06:10:42 +0000

There were nuclear-powered aircraft in the fifties.

Are we to believe that there are briefcase nukes but not briefcase nuclear reactors?

Are we to believe that the technology for nuclear-electric vehicles is not musting away on a TS/SCI basement shelf somewhere?

By: Lu An Li

Lu An Li — Tue, 15 Nov 2022 10:38:36 +0000

“The major disadvantage is that battery energy density is still, at best, about 50 times less than gasoline.”

And takes about 20X longer to charge those batteries to full capacity than fuel a conventional fueled aircraft.

Batteries unless tremendously improvement made and soon a no go. Why even try?

By: Wilbur Hassenfus

Wilbur Hassenfus — Tue, 15 Nov 2022 03:50:19 +0000

A quick Google search suggests that solid-fuel model rockets accelerate vertically at about 9 g.

Scale matters a lot. This is reddit-tier reasoning.

By: Gavin Longmuir

Gavin Longmuir — Mon, 14 Nov 2022 21:32:45 +0000

“a power-to-weight ratio of 10 screams possibility.”

One of the major possibilities is that this power-to-weight ratio ignores realities — such as the weight of the batteries the power source has to lug around.

Hey! I have a great idea for bringing down the cost of air travel. All we have to do is ignore the cost of the plane and the cost of the fuel.

By: Slumlord

Slumlord — Mon, 14 Nov 2022 20:35:08 +0000

Propeller efficiency drops rapidly as one approaches the speed of sound. i.e much of the power becomes devoted to generating shock waves and not propelling the aircraft forward.

By: Isegoria

Isegoria — Mon, 14 Nov 2022 19:25:05 +0000

NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA), believed that it was possible for propeller-driven aircraft to break the sound barrier:

In the 1940s, NACA invested heavily in new designs for propellers through a high-speed propeller research program. Over time, it was able to design propeller blades capable of reaching Mach 1.0. This was accomplished by shortening and thinning the blades, sharpening the leading edges, minimizing camber, and increasing the blades’ angles. While the change was an overall success, parts of the blade would reach supersonic speeds before others. This was problematic for two reasons — first, sonic waves are created when an object nears the speed of sound. Because the blades were reaching Mach 1.0 unevenly, they were creating pockets of sonic waves powerful enough to destroy the propeller. Second, another problem was noise. Propeller-driven aircraft are loud enough, but when those spinning blades reach supersonic speeds, the noise level generated becomes a threat to the structural integrity of the aircraft — and its pilot.