FF for Jet Engines?

[zapkitty]

Brian H wrote:

A wild-ass guess says that we’re looking at 400 MW or more in excess of primary power needs to enable a switch to jet-style propulsion.

that’s just 80 anodes, tessellating a spherical shell, cooled by 160 kg/s of helium in a closed cycle. hardly any challenge, at all 🙂
Yeah — 160 tons of FF, a ton or 10 of helium, and maybe 160 lbs. of fuel? No problemo! :cheese:

All we need to do is install all that gear into a clone of the Spruce Goose!

… more seriously…

… while FF, as it is currently described, is not power-dense enough to directly displace jet engines FF deployment can still make a huge impact in the world of aviation by directly slotting into the spaces currently occupied by subsonic carriers. FF can do this by using transports that have low maintenance and unlimited range…

…. which is a large advantage in a huge market.

One example: A Taiwanese chip fab receives an emergency order from the ITER installation for two dozen replacement chips for a blown heater control array.

ITER has to have the new chips as soon as possible or the reactor budget will implode and take the facility administrators with it.

An FF transport would not even be as fast as a 747… mach 0.72 as opposed to mach 0.85… but the transport gets the chips to ITER before any other commercial carrier could because it does not stop. Does not refuel. Does not have to transfer the package to another aircraft.

… that sort of tortoise and the hare stuff…

[Tulse]

zapkitty wrote: An FF transport would not even be as fast as a 747… mach 0.72 as opposed to mach 0.85… but the transport gets the chips to ITER before any other commercial carrier could because it does not stop. Does not refuel.

That’s a very good point — for long-haul flights the time saved avoiding landing for refueling could be significant.

Does not have to transfer the package to another aircraft.

And that’s an especially interesting point — FF might make it economical to fly cargo with smaller planes more directly to smaller airports, avoiding stopovers and the mess of larger airports, and the need to use long-distance ground transport.

So here’s the question: how small can a plane be and still use an FF powerplant? Does it have to be large passenger-jet sized, or could one make a smaller cargo plane using FF?

[Brian H]

zapkitty wrote:
…

An FF transport would not even be as fast as a 747… mach 0.72 as opposed to mach 0.85… but the transport gets the chips to ITER before any other commercial carrier could because it does not stop. Does not refuel. Does not have to transfer the package to another aircraft.

… that sort of tortoise and the hare stuff…

Reminds me of the advantage that ion engines and VASIMR have over chemical rockets. They have a had time getting off the ground on their own, and are slow to pick up speed, but they keep going faster, and faster, and faster ….

[vansig]

Brian H wrote:
Yeah — 160 tons of FF, a ton or 10 of helium, and maybe 160 lbs. of fuel? No problemo! :cheese:

nope. two capacitor banks, one vacuum chamber, 80 anodes x 20 kg each, and 80 shares of a bigger onion x20 kg each.
plus shielding, under twenty tonnes for the lot..

[JimmyT]

One factor working against a world wide focus fusion powered air distribution network is this: Conventional freight transport isn’t going to stand still either. Ships will be cheaper to operate and undoubtedly cruse faster, since fuel costs won’t be so important. Rail transport will experience some savings for the same reason (fuel costs, not speed). So there will be a new baseline to compete against.

I think upgraded rail and ports will probably make more sense.

[vansig]

zapkitty wrote:
An FF transport would not even be as fast as a 747… mach 0.72 as opposed to mach 0.85…

What I still don’t get is, why is Mach 0.72 an upper bound?

We’re not limited by mass; 80 anodes tesselating a sphere yields 20 tonnes, not 160 tonnes.

We’re not limited to propeller or turbo-prop configuration.

Fusion powered jet does not require a turbine; we don’t have to slow the airstream down or compress it, to heat it, as a ramjet does, since we don’t have to inject chemical fuels.

Scramjet configuration seems to be the simplest engine architecture. and it’s highly efficient, *if* we have a way to heat air with electricity. which we do: i propose to build a high-wattage infrared laser, emitting at a wavelength that air strongly absorbs, yet engine materials do not absorb.

What remains, that could keep this below high Mach numbers and altitudes of 35km or more?

[zapkitty]

vansig wrote:

An FF transport would not even be as fast as a 747… mach 0.72 as opposed to mach 0.85…

What I still don’t get is, why is Mach 0.72 an upper bound?

That was just me using “default” 5MWe FF boxes for aircraft concepts equivalent to current commercial turboprops. A “go anywhere at any time” electric aircraft.

Turboprops such as the Tu-95 have gone as high as Mach 0.92 in tests.

vansig wrote:
We’re not limited by mass; 80 anodes tesselating a sphere yields 20 tonnes, not 160 tonnes.

We’re not limited to propeller or turbo-prop configuration.

Fusion powered jet does not require a turbine; we don’t have to slow the airstream down or compress it, to heat it, as a ramjet does, since we don’t have to inject chemical fuels.

Scramjet configuration seems to be the simplest engine architecture. and it’s highly efficient, *if* we have a way to heat air with electricity. which we do: i propose to build a high-wattage infrared laser, emitting at a wavelength that air strongly absorbs, yet engine materials do not absorb.

What remains, that could keep this below high Mach numbers and altitudes of 35km or more?

And that brings us back to the question of whether using the excess alpha output for direct heating of air would be more efficient. Your design is for 400 MWe, right? Are you omitting the 640 MWt “waste” heat from your calculations? What if there was no “onion” and you tried to use the x-rays as a heat source as well?

[Aeronaut]

zapkitty wrote:

An FF transport would not even be as fast as a 747… mach 0.72 as opposed to mach 0.85…

What I still don’t get is, why is Mach 0.72 an upper bound?

That was just me using “default” 5MWe FF boxes for aircraft concepts equivalent to current commercial turboprops. A “go anywhere at any time” electric aircraft.

Turboprops such as the Tu-95 have gone as high as Mach 0.92 in tests.

vansig wrote:
We’re not limited by mass; 80 anodes tesselating a sphere yields 20 tonnes, not 160 tonnes.

We’re not limited to propeller or turbo-prop configuration.

Fusion powered jet does not require a turbine; we don’t have to slow the airstream down or compress it, to heat it, as a ramjet does, since we don’t have to inject chemical fuels.

Scramjet configuration seems to be the simplest engine architecture. and it’s highly efficient, *if* we have a way to heat air with electricity. which we do: i propose to build a high-wattage infrared laser, emitting at a wavelength that air strongly absorbs, yet engine materials do not absorb.

What remains, that could keep this below high Mach numbers and altitudes of 35km or more?

And that brings us back to the question of whether using the excess alpha output for direct heating of air would be more efficient. Your design is for 400 MWe, right? Are you omitting the 640 MWt “waste” heat from your calculations? What if there was no “onion” and you tried to use the x-rays as a heat source as well?

This sounds like it’ll be optimized for electric output only, with some of the heat going to the cabin and hold. I’m wondering how you plan to heat the air to achieve the supersonic airflow, and what airspeed (if any) would be needed.

[vansig]

Air has a strong absorption line near 1.3THz (230 µm). The idea is to superheat the air with a narrow-band, coherent beam that reflects off container surfaces.

I doubt heating air with x-ray can be done. x-rays are hard to focus,
though we’d want to carry away waste heat by convection, or radiation if possible.

The engine design is so simple that i’m not really seeing a minimum speed for this.
Hot air simply flows out from one end of a large tube, while cooler air gets sucked in the other end.

[zapkitty]

vansig wrote: Air has a strong absorption line near 1.3THz (230 µm). The idea is to superheat the air with a narrow-band, coherent beam that reflects off container surfaces.

I doubt heating air with x-ray can be done. x-rays are hard to focus,
though we’d want to carry away waste heat by convection, or radiation if possible.

X-rays can, however, efficiently heat some materials. My vague idea was that you’d place such a material around the FF core assembly to catch the x-rays and then while the air is entrained in your various manipulations you’d pass it around the heated FF containment.

… and weren’t relativistic electron beams the first option of Lerner-hakase for heating air and propellant since they are best driven by the extremely high voltages that FFs are expected to produce?

Starting with that premise my other idea was to just skip the conversion step and use the alphas directly.

As for ensuring the efficient transfer of beam energy to air… the people working on microwave electrothermal thrusters have already solved this by using focused energy to create a small spot of plasma in the propellant flow. The plasma is pretty much guaranteed to be opaque to infrared, electrons, alpha particles, microwaves and suchlike that you might want to throw at the propellant as long as you maintain the hotspot.
(you wouldn’t try to use this with the x-rays because as you noted the spherical x-ray flux couldn’t be easily focused)

So I’ve no objections per se to an FF-powered jet aircraft… it’s just that the energy density and conversion problems immediately bring up the question of how you would like to do this 🙂

[vansig]

zapkitty wrote:
As for ensuring the efficient transfer of beam energy to air… the people working on microwave electrothermal thrusters have already solved this by using focused energy to create a small spot of plasma in the propellant flow.

Yeah, microwave electrothermal thrusters use a propellant, like water; in space we’d still need a propellant, but this is a jet. i’d prefer to avoid noxious exhaust products, so maybe not raise it to plasma temperature.

of course there’s science to do, to make this go. i dont have all the answers, but tuning and focusing the beam seems to be the key

[zapkitty]

vansig wrote:
Yeah, microwave electrothermal thrusters use a propellant, like water; in space we’d still need a propellant, but this is a jet. i’d prefer to avoid noxious exhaust products, so maybe not raise it to plasma temperature.

Well, for the effect to work only a small portion of the exhaust needs to reach plasma… but it seems this might all be mooted by the invention of the plasma window.

Not only can this “force field” contain a vacuum against atmosphere at the cost of a few kilowatts while allowing a particle beam to exit that vacuum without having to vent the system… but it can focus an ion beam that happens to pass through it.

And alpha particles don’t travel far in atmosphere before being stopped.

vansig wrote:
of course there’s science to do, to make this go. i dont have all the answers, but tuning and focusing the beam seems to be the key

Just remember that the aloha beam is hoped to be used to recharge the caps with some juice left over.

If that balance is to be altered then the energy to recharge the caps must come from somewhere else… like an onion. Which might be workable, just something else to keep in mind.

[vansig]

zapkitty wrote:

of course there’s science to do, to make this go. i dont have all the answers, but tuning and focusing the beam seems to be the key

Just remember that the aloha beam is hoped to be used to recharge the caps with some juice left over.

If that balance is to be altered then the energy to recharge the caps must come from somewhere else… like an onion. Which might be workable, just something else to keep in mind.

i meant the THz laser beam

[zapkitty]

vansig wrote:
i meant the THz laser beam

At what efficiency is the beam expected to operate?

[Aeronaut]

I’m having problems understanding the airflow without either a compressor or a minimum air speed (thinking along the lines of the SR-71 Blackbird’s variable ducting to put essentially 2 engines into 1 nacelle). Next up, of course, is the proposed scramjet’s use of hydrogen fuel- mainly storing enough liquid hydrogen. But if this can be made to work, it should be able to lead to a SSTO vehicle?

[Author]

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