What would a fusion powered airliner look like?

[Matt M]

http://www.aviationweek.com/aw/eventType2.do?eventName=imagining_future#

Select panel 6 for a picture.

[zapkitty]

Matt M wrote:

http://www.aviationweek.com/aw/eventType2.do?eventName=imagining_future#

Select panel 6 for a picture.

Nope. Not for an aneutronic Focus Fusion-powered aircraft… especially not with that huge radiation trefoil 🙂

Blended-wing turboelectric and distributed power designs already under study can be readily adapted for use with any sufficiently compact power source.

Even current tube-and-wing designs can be retrofitted if that’s cheaper, but the interior volume provided by blended-wing designs is awfully convenient…

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20100036222_2010039460.pdf

http://www.aviationweek.com/aw/blogs/aviation_week/on_space_and_technology/index.jsp?plckController=Blog&plckScript=blogScript&plckElementId=blogDest&plckBlogPage=BlogViewPost&plckPostId=Blog:a68cb417-3364-4fbf-a9dd-4feda680ec9cPost:ea7a1fa9-2129-4c67-a93c-52ca6bda8e81

[Steven Sesselmann]

I imagine a fusion powered flying machine would look something like the racing pods that were seen in Star Wars, with the engines suspended far ahead of the passengers, so as to create distance from the neutrons.

Flying would be a bit like waterskiing, you kind of hang on for your life at the end of a rope 🙂

Steven

Attached files

[zapkitty]

Steven Sesselmann wrote: I imagine a fusion powered flying machine would look something like the racing pods that were seen in Star Wars, with the engines suspended far ahead of the passengers, so as to create distance from the neutrons.

Flying would be a bit like waterskiing, you kind of hang on for your life at the end of a rope 🙂

Steven

…
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… … … … were you aware that the Focus Fusion goal is an aneutronic device? Few neutrons and no boiling water nor any steam turbines.

Approximately a meter of shielding would bring the radiation from an FF unit down to below background levels. No ropes.

But at this time various stresses are assumed to limit each core to about 5 MWe output and so while the energy density of any fusion fuel is beyond comparison to any chemical fuel the minimum volume required for an FF reactor and shielding means that the default size assumption of a “standard” 5 MWe FF module is about 3 meters x 2 m x 2 m sans cooling and auxiliary gear.

Now one such could be almost buried in the wing root of a 747 and you could add an extra core for an extra 2 meters to give you a 10 MWe module… but a 747 is huge and on takeoff needs 90+ megawatts of power and 65 MW for level flight.

Is it doable? And worth doing? I think so 🙂

And it does seem that FF units could easily dominate the mid-size subsonic passenger and cargo markets… which is by far the bulk of the total commercial aviation market.

[Steven Sesselmann]

zapkitty wrote: were you aware that the Focus Fusion goal is an aneutronic device?

Yes, fully aware of the ff goals, just not 100% convinced yet, the p+B11 fusion process needs to be demonstrated first.

You may or may not know that I am working on a new confinement method called F.I.C.S., (Fusion Induced Charge Separation), if it works the way I intend it to, it should convert fusion into electrical current and thrust.

The patent covers two designs, one for production of heat and electricity and the other a thrust engine, can’t say much more, but it is due for publication on January 6th., and then it can be discussed.

It is ideally suited to space travel, as it takes advantage of the vacuum of space.

Prototype in progress..

Steven

[zapkitty]

[em]”Space travel…. why do fusion conversations always come back to space travel?….”[/em] mutters the kitty whose first thread on the forum was on exactly that subject… and who is working up an FF power and cooling layout for a moonbase….

So, back to airliners 🙂

A crude approximation of a 747 retrofitted for FF fusion-electric flight. The 747 3ds model victimized here is from
http://artist-3d.com/free_3d_models/dnm/model_disp.php?uid=1004

Attached files

[annodomini2]

A 747 produces approximately 85,000 HP peak (Thrust doesn’t translate to HP linearly!)

Which is approximately 64MW, how big would a 64MW FF reactor be??

[zapkitty]

annodomini2 wrote: A 747 produces approximately 85,000 HP peak (Thrust doesn’t translate to HP linearly!)

Which is approximately 64MW, how big would a 64MW FF reactor be??

At 5 MWe per core that’d be 13 cores.

Each core needs a bank of capacitors or equivalents and a vacuum pump. When the onion is factored in the core needs a meter of shielding + onion to bring the radiation down below background levels… thus the “standard” default of a single core 5 MWe unit being 2 x 2 x 3 meters.

…. but would adjacent cores need that much shielding from each other? and couldn’t they share caps and pumps?

Thus there’s a slew of unanswered questions concerning how many cores can be fitted into one shielded area, one “unit”, without interfering with each other… or melting each other.

Some here in this forum have ventured concepts with dozens or even hundreds of cores arrayed together which, since each core is supposed to produce ~5 MWe at high voltage and ~7 MWt, would result in some [em]interesting[/em] issues to deal with 🙂

(… i won’t mention vansigs 1500 core concept… really, I won’t)

But while I usually play ultraconservative in my approximations here (really!) it would be silly to insist that each core must have all the cubic meters of volume associated with the “default” FF unit in all configurations for all applications… so I’d have no problem with a 2-core 10 MWe unit in a cylinder 2 meters wide and 5 meters long. It’d still be a conservative estimate.

In the following attachments you’ll find 13 cores in 13 units as cylinders, 12 cores in 6 units with one left over :), and the 6 units in the wings with the ground crew getting ready to install the 13th core into the fuselage.

In all these concepts the NASA turbo-electric distributed studies show that the FF units and superconducting electric fans weigh less than the standard turbofans [em]and fuel load[/em] that they would replace.

Instead of doing double-duty for lift and fuel tanks the wings do double duty for lift and air-cooled radiators… which works out well since most turbo-electruc designs have the fans close above and aft of the wing or wing-body.

Attached files

[delt0r]

There is another problem. A FF using p+11B reaction will produce some high energy gammas. About .1% of the energy output or so, ie about 6kW of gamma in the MeV range. Even if the rate is less by a factor of 10 that is still a lot of radiation. These will need far more than a 1 meter of shielding. Even a meter is too much for the weight of an aircraft.

I can’t see p+11B flying. It makes more sense to use a big power station to create jet fuel out of air and water.

[zapkitty]

delt0r wrote: There is another problem. A FF using p+11B reaction will produce some high energy gammas. About .1% of the energy output or so, ie about 6kW of gamma in the MeV range. Even if the rate is less by a factor of 10 that is still a lot of radiation. These will need far more than a 1 meter of shielding.

This comes up occasionally. Lerner says it will not be a problem.
https://focusfusion.org/index.php/forums/viewreply/728/

delt0r wrote: Even a meter is too much for the weight of an aircraft.

You need to factor in that the shielding surrounds a very small volume (operational FF cores will be much smaller than what you see in the current setup) and that the shielding is mostly water.

Even a conservative estimate only gets you 4.3 tons shielding per core… less if you use multi-core units as described above. That’s less than the weight of the jet fuel that you won’t be needing anymore.

delt0r wrote:
I can’t see p+11B flying. It makes more sense to use a big power station to create jet fuel out of air and water.

It’ll work fine structurally. The one serious drawback is that a crash will pose a risk of releasing carbon-11… which will decay back into B11 in 9 hours but would be used to freak people out.

[delt0r]

It is a easy calculation and you need a lot more than a meter for that kind of power. Even 1J on the outside is going to be a problem for passages on a 1+ hour flight, there are some quite high energy gammas (much higher than 1MeV). Its easy to deal with on the ground, not for flight. Gammas are a real PITA to shield against without some serious 1/r^2 “shielding” or in a pit etc. Water is not very good at dealing with gammas, dense materials do much better.

[zapkitty]

delt0r wrote: It is a easy calculation and you need a lot more than a meter for that kind of power.

Sorry, I spaced out and conflated the question with the shielding stuff and answered something you didn’t ask. Gomen!

The following really is what Lerner had to say about primary gammas:

https://focusfusion.org/index.php/forums/viewreply/6932/

That reaction occurs only at energies above 7Mev and even at 14 Mev is about a million times less likely than the tri-alpha one is at 600 keV.

[delt0r]

Not what i was talking about. The reaction is p+11B-> 12C* -> 8Be*+alpha -> 3alpha +gamma. These gammas are below the 7MeV range IIRC. These gammas are quite rare (not that rare however, it is why the energy distribution of the resultant alphas are the way they are) but that does not change the fact that even .1W of gammas is a *lot*, and you are talking about 60MW or more, so even these quite small background levels are still on the order of kW and then you need a lot of shield to get than down to levels that are safe for humans to not worry about. Even the low level of background neutrons will matter at these power levels for something that is suppose to be flight weight.

The problem is that 1W out of 60MW is only much less than 1ppm, but still very bad for human health, and gammas are really hard to stop.

I am not claiming they are hard to deal with generally. I am claiming they are hard to deal with for something that needs to be flight weight. Power density in aircraft is critical.

[zapkitty]

delt0r wrote: Not what i was talking about. The reaction is p+11B-> 12C* -> 8Be*+alpha -> 3alpha +gamma. These gammas are below the 7MeV range IIRC. These gammas are quite rare (not that rare however, it is why the energy distribution of the resultant alphas are the way they are) but that does not change the fact that even .1W of gammas is a *lot*, and you are talking about 60MW or more, so even these quite small background levels are still on the order of kW and then you need a lot of shield to get than down to levels that are safe for humans to not worry about. Even the low level of background neutrons will matter at these power levels for something that is suppose to be flight weight.

The problem is that 1W out of 60MW is only much less than 1ppm, but still very bad for human health, and gammas are really hard to stop.

I am not claiming they are hard to deal with generally. I am claiming they are hard to deal with for something that needs to be flight weight. Power density in aircraft is critical.

… this would seem to somewhat contradict the “less than background” that Lerner speaks of so it would be good to have clarification and details. An overly excited 8Be decays into 2 alphas and a gamma?

The neutrons are also supposed to be less than background which would make an FF unit a bit of a neutron sink… but massing the units would increase the neutron count?

[vansig]

the 1m thickness of water + boron handles the neutrons; and a few inches thick of lead outside that should be able to deal with the occasional gamma

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