FF for Jet Engines?

[JShell]

nemmart wrote: Why not just power the airplane with FF’s? Just checked some numbers. A 747 burns on average a gallon a second during flight. Jet A has roughly the same energy per weight as gasoline which has 121 MJ per gallon. Therefore a 747 uses 121 MW/hr, which means 20 FFs to produce the juice.

My second thought is that so many of these posts read like FF is an all but done deal. But we should all be a bit more realistic — it isn’t a done deal. So many things could go wrong – from the fusion physics, to the engineering to the economics.

Another aspect that particularly troubles to me: if FF was as close as it sometimes appears, I’d think funding would be pouring in. Think of it this way — what would be more beneficial, FF working or say a malaria vaccine? Organizations like the Gates foundation throw tons of money at long shot, big payoff efforts, like a malaria vaccine. So why hasn’t someone or some organization with deep pockets decided to fund this?

If you ask me, Focus Fusion is so far outside the norm of power generation that most people think its decades away from proving its feasibility, instead of years away . . . if rich folks act in a herd, they haven’t fully heard about Focus Fusion, or if they have, they don’t believe it’ll work. there have been too many cries of wolf regarding fusion in the past. My guess is that Google and other venture capitalists also stayed away because they got their “expert opinions” from pro-Tokamak physicists, who don’t think that FF is viable. Eric Lerner already made plenty of enemies in the academic establishment by publishing challenging the Big Bang theory, which is regarded to be almost unquestionable among many physics Ph.Ds . . . .if I’m not mistaken, one reason why the Hadron Collider was built was to try to detect certain kinds of “dark matter” that “haven’t been observed yet” because they are a mathematical necessity for the Big Bang theory to hold together in terms of universe expansion rates and redshift (ie, they need more gravity to slow the expansion of the universe if the universe expanded from a single point a certain amount of time ago) . . . yet Eric’s theory makes them unnecessary.

Thats my read at least. I’m sure Eric or others can do a better job of telling the story.

[Henning]

nemmart wrote: Also, I think in Eric’s google tech talk, he mentioned 330 hz.

No, that 330Hz is just a fantasy-value developed within this forum on the base that the American Electrical System (tm) has a cycle of 60Hz. The rest of the world uses 50Hz, therefore a rate of 300Hz or 350Hz would be correct for the World’s Electrical System (tm). It was introduced for eliminating output capacitors. Eric talks about a variable rate of up to 1kHz.

For embedded systems (ie. aeroplanes) without any external connection this requirement does not apply at all.

It is even benifitial to synchronise the shot frequency with rounds of the propeller.

[zapkitty]

Just had a thought about vansig’s jet analogue… heat won’t give you the torque electric will, but heat has advantages at speed and altitude… the early jets had trouble low and slow but were in their element high and fast… the modern turbofan is a compromise, really…

… but to be efficient props (and fans) need to be big… in some cases so big the landing gear couldn’t reach the ground 🙂

… so what if that 5 MWt from the standard FF were to become 10 MWt once the plane was airborne? Take vansig’s presumed flow-through FF module and slide a sheath of an appropriate x-ray opaque material between the core and the onion once in the air… the air flowing through gets twice the thermal whammy but would it make up for feathering the prop? … run it hybrid?… duct design would be everything…

[vansig]

zapkitty wrote:
… so what if that 5 MWt from the standard FF were to become 10 MWt once the plane was airborne? Take vansig’s presumed flow-through FF module and slide a sheath of an appropriate x-ray opaque material between the core and the onion once in the air… the air flowing through gets twice the thermal whammy but would it make up for feathering the prop? … run it hybrid?… duct design would be everything…

i like it. now, can we bring it up to hypersonic speeds?

[zapkitty]

vansig wrote:
i like it. now, can we bring it up to hypersonic speeds?

First it might be best to see if there’s any advantage at all to doing this… wouldn’t be much fun to get your craft up to a thousand meters and 300 kph, switch over to “10 MWt mode”… and fall out of the sky for lack of power…

But it’s something that came to mind and seems worth checking out.

[vansig]

The short-term goal is to create a delivery service: air-drop to any co-ordinates on the planet within 90 minutes, or it’s free.
The longer-term goal is to develop a craft capable of orbital insertion with minimal expenditure of propellant.

Ramjets tend to have quite different design parameters at supersonic vs hypersonic speeds.
A cleverly designed hybrid engine could, maybe, involve shape changes, that also becomes a rocket at very high altitudes, and rescue otherwise dead-weight.

Fuel bulk is one of the problems with existing designs. With fusion, that problem goes away

http://en.wikipedia.org/wiki/X-43A

[belbear]

The conventional approach for fusion-powered flight is to use a fusion-manufactured fuel like liquid H2, But apart from the CO2 issue and fuel cost, little would change.
So I like more the idea of a direct-fusion powered aircraft. That would revolutionize commercial flight as much as the transition from props to jets did.

Direct fusion powered flight may indeed need some radical fuselage design, totally departing from the classic tube-with-wings model.

Among the possibilities are:
A triple-hull design, with two side hulls for passengers and the center one for the power plant. Or the other way around. Or a double-hull.
A thick-wing design (a.k.a. “flying-wing”) a huge wing that houses all fusion technology inside, the reactors furthest from the passenger section.
A tandem-hull tandem-wing design (actually two planes in line, the rear one for the fusion plant)
A vertical double-hull (two separate hulls above each other)…

Some of these have been built before, but apart from some military experiments, never used commercially.

Biggest problem is the cost of development. Most current aircraft technology was developed for the military with extensive funding during the cold war and its aerospace race: Jet engines, lightweight alloys, radar, inertial and satellite navigation….

With sufficient clearance between reactor and occupants, less neutron shielding is necessary.
Shielding may only be required toward the passenger and crew, not away from them since a lot of free air is also an excellent shielding.
A more lightweight and efficient material than tons of water may also be used.

The water can even be used for more than just shielding: Injecting some of it in a hot jet exhaust increases power the way an after-burner does. Handy for take-off, punching the sound barrier or emergency situations.
When freed from the burden of fuel consumption, supersonic commercial flight will again become a possibility. Cheap, this time.
Now a 747 does only one quarter-globe flight per day, often necessitating two crews on board. A Mach-3 plane could do 2 or 3 of those with one crew, multiplying revenue. And fly a half-globe in one convenient 5-hour trip. And why stop at Mach 3?

With direct fusion power, adding extra weight for shielding is not really a problem, since you can add more engine power, multiple engine configurations and lifting surface without needing to add more tons of fuel. As long as the current airports and runways can take it, it’s okay.

Scientifically this may all be safe and sane, but alas, we’re still living in the post-Chernobyl era. If the media blurt out that flying in nuclear planes will make your dick fall off, few passengers will board them. Even if you have a 1st class seating space for an economy ticket.

[Tulse]

belbear wrote: The conventional approach for fusion-powered flight is to use a fusion-manufactured fuel like liquid H2, But apart from the CO2 issue and fuel cost, little would change.
So I like more the idea of a direct-fusion powered aircraft. That would revolutionize commercial flight as much as the transition from props to jets did.

I’m not convinced the economics and engineering involving in putting FF directly on planes makes a lot of sense. There are a lot of numbers tossed around here, but I’m doubtful that any of them indicate it is better to fly directly with FF rather than using it as a fuel source. Anyone have a convincing analysis (or have I missed a convincing analysis already presented)?

[vansig]

belbear wrote: Direct fusion powered flight may indeed need some radical fuselage design, totally departing from the classic tube-with-wings model.
[…]
With sufficient clearance between reactor and occupants, less neutron shielding is necessary.
Shielding may only be required toward the passenger and crew, not away from them since a lot of free air is also an excellent shielding.

seems to me, that these constraints lend themselves to longer tubes, with reactor and engines in the rear, except possibly in lenticular aircraft, where the pilot might be separated from everything else by a hemispherical shell of shielding.

[zapkitty]

Tulse wrote:
I’m not convinced the economics and engineering involving in putting FF directly on planes makes a lot of sense. There are a lot of numbers tossed around here, but I’m doubtful that any of them indicate it is better to fly directly with FF rather than using it as a fuel source. Anyone have a convincing analysis (or have I missed a convincing analysis already presented)?

You missed at least one because it’s at the center of your argument… fuel 🙂

What are the savings advantages that accrue to a transport that never has to refuel?

I did not develop the idea much because I was just interested in pointing out that there is indeed at least one set of viable real-world numbers to compare dpf with for fusion-powered flight.

But given the propfan-replacement transport concept (propfans are based on the fancy new propeller concepts that make the huge propeller diameters of the older high-power turboprops unecessary) other savings come to mind… electric engines based on superconductors are lighter and less maintenance intensive than non-sc motors, and motors that use frictionless magnetic bearings have greatly reduced wear and need even less maintenance than motors that use standard bearings.

And it would seem that this is pretty much a very large advance over the wear and subsequent maintenance costs incurred by jet turbines.

So… it doesn’t seem out of line to propose a transport that uses standard airport runways and facilities, that never needs refueling and is only taken out of service one day every 90 days for an electrode change and a general maintenance checkup and fuel top-off while the techs are waiting for the dpf to cool.

If it works then that looks like some very big savings for a standard air transport company.

[zapkitty]

… and, less pleasant to contemplate, but the fact that the transports aren’t stuffed with jet fuel even before transoceanic flights makes them much safer than jets in many regards…

[Brian H]

I wonder if MHD can be used for jet transport. FF seems like a natural for this; I’ve seen designs for SSTO spacecraft that use it in atmosphere, and ion drive thereafter.

[zapkitty]

Brian H wrote: I wonder if MHD can be used for jet transport. FF seems like a natural for this; I’ve seen designs for SSTO spacecraft that use it in atmosphere, and ion drive thereafter.

Still just not enough power, it seems. FF units, as currently described, are just too heavy

The currently proposed uses of MHD in aerospace propulsion are decelerating incoming air and using the power extracted from that to accelerate the outgoing exhaust (more of a power transfer than actual propulsion) and for external airflow control at supersonic and hypersonic speeds…

These uses alone have power overhead requirements measured in 10’s of MWs.

This would seem to indicate that MHD just can’t be used for primary propulsion at the notional ~50 MW power levels I’ve floated in this thread and that any MHD enhancements to the primary propulsion would eat the entire power supply… including the power that was budgeted for the primary propulsion.

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.

But once that raw power plateau has been reached (whatever the actual numbers may be) then the entire panoply of MHD tricks should be available and fusion-powered craft will occupy all niches of the aerospace ecology…

… and…

… and what everybody and their dog keeps insisting on jamming sideways into all fusion flight discussions…

…flying to orbit…

… becomes theoretically possible 🙂

[vansig]

zapkitty 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 🙂

[Brian H]

vansig 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:

[Author]

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