FF for Jet Engines?

[Aeronaut]

dennisp wrote: Hmph. Ok maybe I should retract my “too bulky” comment.

How would the jet work? Propeller plane is easy, just electric motors, but we’ve got no burning fuel to inject into a jet engine.

Airliners and air freighters like 747s could substitute a 16 ton electric motor for the jet turbine. The fan is essentially a propeller, so it won’t go anywhere near mach speed. Not having to buy, store and lift ~220 tons of fuel can lead to some real pricing advantages. but I’d expect it to really catch on in new designs rather than retro-fits.

[vansig]

Breakable wrote:
Would be interesting if some reaction-less drive would come online
http://en.wikipedia.org/wiki/Reactionless_drive

According to that article,
“The underlying problem [with reactionless drives] is that breaking the law of conservation of momentum shatters the entire mathematical framework [of physics].” These devices by their very nature violate the law of conservation of momentum

Let’s propose a reactionless drive that does not break conservation of momentum. All we need to do is to find a way to make weakly-interacting particles interact a little more strongly, and then find, among them, a favoured direction.

[vansig]

dennisp wrote:
are you proposing heating via electric resistance? I think we just invented the flying toaster! 🙂

No. A 5MW Focus fusion generator, operating at 50% efficiency, will generate 5MW heat. Use that in your “jet” engine.

[Breakable]

vansig wrote:

are you proposing heating via electric resistance? I think we just invented the flying toaster! 🙂

No. A 5MW Focus fusion generator, operating at 50% efficiency, will generate 5MW heat. Use that in your “jet” engine.
If FF gets too efficient I think we can add microwave heating with oxygen or nitrogen resonant frequency.

[zapkitty]

Breakable wrote:
If FF gets too efficient I think we can add microwave heating with oxygen or nitrogen resonant frequency.

Arrgh! 🙂

Please let FF get more efficient… do you know what trying to jettison 5MW of low-temp waste heat in return for 5MW of electrical power gained does to spacecraft margins? It should be a crime… 🙁

[jamesr]

Microwaving air is a really bad idea – you end up with lots of nasty NOx compounds

[Will]

jamesr wrote: Microwaving air is a really bad idea – you end up with lots of nasty NOx compounds

Does it generate more NOx than a kerosene powered turbojet?

[dennisp]

These devices by their very nature violate the law of conservation of momentum

They only do that locally, while in the universe as a whole momentum is conserved.

The physics kinda intrigues me. He’s got an elegant explanation for inertia, based on relativity alone. The only other inertia theory brings quantum physics into it. And his theory is pretty similar to Cramer’s transactional interpretation of quantum mechanics. Maybe, contrary to the cartoon, the universe really is like that.

I admit I’m not exactly holding my breath for this one, but it seems worth the experiment. Given that it’s only evident under very contrived conditions, if it’s true it’s not something we would have noticed so far.

[zapkitty]

Will wrote:

Microwaving air is a really bad idea – you end up with lots of nasty NOx compounds

Does it generate more NOx than a kerosene powered turbojet?

While an interesting question in itself it seems pretty much moot. 5 MWt at 426 degrees C isn’t going to move much air by heating. Even times 20… assuming you could somehow duct the air past the FF cluster…

… but an FF-powered fanjet could have a sideline in de-icing runways while waiting for takeoff clearance… 🙂

[zapkitty]

… MWe = MWt…
We’re going to have to face it…
… no way around it…
… the primary application of FF to air travel will be…
…
… high-subsonic dirigibles carrying passengers and cargo… 😉

(dives into previously prepared foxhole)

[KeithPickering]

vansig wrote: or place the reactors in the tail section, then have just a single shield for the bunch

Misses the point. About half of the energy from FF derives from capture of the X-rays using the onion-skin. So the space issue is real, as each FF must have its own onion-skin. Twenty of those would easily fill a 747, leaving no room for payload.

Much easier to use FF as an energy source from which to create hydrocarbon fuel.

[Aeronaut]

But multiple cores can share the same shielding envelope, no? Say 4 cores in a container slightly larger than a single core’s shield. Remember, this is going to preferably be placed near the wing root’s center to help with trim while decreasing length of cable runs.

[zapkitty]

Aeronaut wrote: But multiple cores can share the same shielding envelope, no? Say 4 cores in a container slightly larger than a single core’s shield.

The fabled 20MW DPF box!

[vansig]

KeithPickering wrote: About half of the energy from FF derives from capture of the X-rays using the onion-skin. So the space issue is real, as each FF must have its own onion-skin. Twenty of those would easily fill a 747, leaving no room for payload.

and i thought the onion was about the size of a large pumpkin, say ~1 m diameter

[Breakable]

The first prototypes FF will be probably heavy and large, but with time miniaturization will probably run its course…

[Author]

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