FF for Jet Engines?

[Breakable]

The units are wrong – it’s 6.4 kj not mj. See the “how_will_we_get_there_from_here” doc. Also, I think in Eric’s google tech talk, he mentioned 330 hz.

Nothing seems to add up
6.4 kj * 330 hz = 2.112 MW
Lets just say the generator will produce from a few kilowatts to a few gigawatt’s. I fully understand that there can be great uncertainty ATM.
Probably much will be cleared up at the end of this year or next when unity is achieved.

[Breakable]

Tulse wrote: Commercial aircraft operate between extremely well-equipped points, so there is really no reason that they have to carry their power generation actually on board — they could more easily be run on batteries that are swapped out between flights, or (as has been pointed out before), powered with conventional jet engines using synthetically-produced fuel. Successful and cheap FF will be a game changer, but it doesn’t have to be directly used to have that effect — no one is going to drive a FF-powered car, and there’s no real reason to use FF in jets. (It makes far more sense for vehicles like ships and submarines, where travel times are very long, and space, where refueling isn’t really much of an option.)

Short term (5-10 years) – probably you are right.
But for long term (10-50 years) I don’t see why such a cool idea as a plane that needs no refueling would be passed out.
Maybe we are solving a problem that does not exist, but in a resource unconstrained world that might be a habit.

[vansig]

Aeronaut wrote: Can several FF cores share the same shielding envelope? I believe this is the 5th time I’ve asked.

Yes, I believe so. A shot is on the order of about a microsecond, total time. AFAIK, the only thing preventing 100,000 shots/second or more is thermal management. Sharing the same onion and the same water and other shielding, and even the same capacitors, could well enable the reactor’s total mass to scale up sub-linearly.

[vansig]

vansig wrote: A 5MW Focus fusion generator, operating at 50% efficiency, will generate 5MW heat. Use that in your “jet” engine.

By the way, a nuclear powered ramjet engine was invented in 1957. The only thing i don’t like about it, is that fission can melt down and make a mess.

http://en.wikipedia.org/wiki/Project_Pluto

[vansig]

Breakable wrote:

The units are wrong – it’s 6.4 kj not mj. See the “how_will_we_get_there_from_here” doc. Also, I think in Eric’s google tech talk, he mentioned 330 hz.

Nothing seems to add up
6.4 kj * 330 hz = 2.112 MW
Lets just say the generator will produce from a few kilowatts to a few gigawatt’s. I fully understand that there can be great uncertainty ATM.
Probably much will be cleared up at the end of this year or next when unity is achieved.

5 MWe / 50% efficiency = 10MW(e+t); divide by ~300 shots/second = 33.3 kJ / shot. (this is the 33 kJ Eric mentions).
Note that this is what we get after some otherwise usable electrical energy was carved off to fire up the next shot, which costs 70 kJ. (that’s 100 kJ from the capacitor bank, 70 kJ consumed, 30 kJ recovered in the mirror bank). So really, there’s 70+33=103 kJ in a shot.

The 6.4 kJ above is a part of the picture, that ignores the onion. It is very sensitive to actual recovery efficiencies.

[zapkitty]

So let’s go by the standard FF number of 5 MWe usable output… that’s 5 MJ per second… divided by 330 Hz is 15151.51 joules usable per pinch…

[zapkitty]

Walking before running…. let’s start with known electrically-powered aircraft and see what they can do with the limited resources available pre-fusion…

http://en.wikipedia.org/wiki/Electric_aircraft

… yes, the FF is much heavier than any other power source currently flying… but the power level is amazing for an electric aircraft and the range, of course, is unlimited…

… then begin looking not at “jet engine substitutes” but at industrial air-moving products that operate in the multi-megawatt range we need for FF-powered flight. These industrial units won’t be designed flightweight but that’s just engineering 🙂 and the figures you get will make sense…

[Breakable]

zapkitty wrote: Walking before running…. let’s start with known electrically-powered aircraft and see what they can do with the limited resources available pre-fusion…

http://en.wikipedia.org/wiki/Electric_aircraft

… yes, the FF is much heavier than any other power source currently flying… but the power level is amazing for an electric aircraft and the range, of course, is unlimited…

… then begin looking not at “jet engine substitutes” but at industrial air-moving products that operate in the multi-megawatt range we need for FF-powered flight. These industrial units won’t be designed flightweight but that’s just engineering 🙂 and the figures you get will make sense…

The important part is not weight, but weight divided by power output.
The solar aircraft (Centurion) weight is 862 kg,
power output 31 kw.
If FF output is 5 MW
then the weight of aircraft it should carry with similar limitations is about 139 tons.
Comparably 747 is 442 tons
Where Cesna is 0.658 ton
so basically something in between should work on the lighter side if we want more speed.

[nemmart]

Okay — let’s dream for a minute. Suppose FF works… (all posts should start with that).

Think about ports:
– there are limited places for ports – requires a coast and deep water
– shipping is damn slow
– the busy ports often have long unload queues
– a lot of freight just passing through the port — only because there is not a direct route from source to destination.

Imagine a different world:
– all major freight transport goes by air — because it’s fast and the fuel is free
– airports to handle freight get built everywhere
– trucks are only used to get the goods from the local airport to the final destination
– use a point to point air traffic control system, handled locally by each plane instead of the centrally managed mess
– imagine instead of all these truckers having a truck they were all pilots, owning their own freighter and controlling their own route

So what would this enable?
– much shorter supply chains (that’s a huge huge win right there)
– it completely changes food distribution, you’d actually get fresh produce that was out of season 😉
– you could probably reduce the amount of highway maintenance and rail maintenance dramatically, you just wouldn’t need it
– it’s really decentalized, a bit like PCs replacing mainframes.

I love it!

[Tulse]

That’s a lovely utopian scenario, nemmart, but I doubt FF would bring it about. While fuel costs are a significant part of the cost of airline operations, they are by no means the only costs involved — labour costs and capital outlays will always be there, and FF does nothing to address those. At best you might get a 30% reduction in the cost of air transportation, which is not small, but of course transportation is only a small part of the cost of transported goods, so that reduction will play a very small role in the final price of a product, and likely be washed out by other competitive factors.

If FF works it will indeed be fantastic, but I don’t think it’s enough to produce the radical changes you posit.

[zapkitty]

Oops… turns out there’s a much more directly equivalent analogue for the power levels we seek… turboprops.

And they’ve built some big ones…

Okay… I think I was a socialist last week so I guess I must be a communist this week… so, Comrade, let our example
be the Soviet People’s Tu-114 passenger liner!

aircraft stats:
length 54 meters
wingspan 51 m
height 15.5 m
wing area 311 m^2
mass empty 91 metric tons
mass maximum 171 t
mass fuel 50.2 t
mass payload 30 t
# of passengers 120 to 220 depending on shoehorn factor…

max level flight speed 870 km/h at 8000 meters (Mach 0.78)
cruise speed: 770 km/h at 9000 m (Mach 0.70)
ceiling 12000 m
range 6200 km at max load

engine stats
# of engines 4 int
type Kuznetsov NK-12MV
thrust per engine 11 MWe … ding!ding!ding!
…. two standard FFs running a little bit hot…

total thrust 44 MWe… a little under 9 FFs… or however you want to allocate caps and ‘trodes amongst the onions…

engine mass 1155 kg
total engine mass 4620 kg
total engine mass *plus fuel mass* 54820 kg…

… call it 54 tons allowed for propulsion…

Gonna be a bit of a pain with the narrow body of the Tu-114… but then it was the fastest propeller-driven passenger
aircraft ever built… 🙂

… maybe have some FFs internal and 4 slightly lesser shielded FF modules out with the propeller mounts on each
wing? Deactivate them for servicing and passenger loading purposes and to taxi… only activate them for takeoff,
flight, and landing?

Working up the big Airbus turboprop cargo lifter with similar results so far… unlike the Tu-114, which was an
ex-bomber, the A400M is designed as a freight hauler so handling the FFs is easier…

[Breakable]

Tulse wrote: That’s a lovely utopian scenario, nemmart, but I doubt FF would bring it about. While fuel costs are a significant part of the cost of airline operations, they are by no means the only costs involved — labour costs and capital outlays will always be there, and FF does nothing to address those. At best you might get a 30% reduction in the cost of air transportation, which is not small, but of course transportation is only a small part of the cost of transported goods, so that reduction will play a very small role in the final price of a product, and likely be washed out by other competitive factors.

If FF works it will indeed be fantastic, but I don’t think it’s enough to produce the radical changes you posit.

Labor costs can be reduced by robotization. Capital requirements will be reduced trough price drop in materials and manufacturing costs.
Imagine a standard small airport kit produced in a factory and assembled by robots on site. In case it is VTOL the cost could probably be less than a large house – nothing compared to current multi-billion airports. I can imagine that happening in 10-20 years in case we have FF now.

And btw flying cars don’t need airports, just a lawn.
http://www.brysonmeunier.com/assets/2008/8/11/flying-car-m400.jpg

[zapkitty]

Here’s the A400M turboprop cargo hauler for comparison…

aircraft stats:
length 45.1 meters
wingspan 42.4 m
height 14.7 m
wing area 221,5 m^2
mass empty 70 metric tons
mass maximum 141 t
mass max landing 122 t
mass fuel 50.5 t
mass payload 37 t
# passengers – a cargo carrier, Wiki says 116 troops with full gear
-or-
66 stretchers w/ 25 medics attending…
max level flight speed 780 km/h at 9000 meters (Mach 0.72)
cruise speed: 780 km/h at 9000 m (Mach 0.72)
ceiling 11300 m
range 3298 km at max load

engine stats
# of engines 4 int
type Rolls-Royce TP400-D6
thrust: 8.2 MWe
power-to-weight ratio: 4.41 kW/kg
total thrust 32.8 MWe…

… 6.5 FFs or however you want to allocate caps and ‘trodes amongst the onions…

engine length 3.5 meters
engine diameter 0.92 m
engine mass 1890 kg
total engine mass 7560 kg
total engine mass *plus fuel mass* 58060 kg…

…58 tons for propulsion…

oops… turns out the A400M actually has a fuselage diameter of approx 4 meters… close to the Tu-114
despite my impression to the contrary… but the A400M’s lesser power levels still make a straight
transition to FFs easier than with the Tu-114 layout…

[vansig]

the more i think about this, the more i believe, that in an aircraft engine, you want the highest air flow nearest the pinch, so that you can cool the anode and cause gases to expand, increasing thrust

[zapkitty]

vansig wrote: the more i think about this, the more i believe, that in an aircraft engine, you want the highest air flow nearest the pinch, so that you can cool the anode and cause gases to expand, increasing thrust

I don’t know…

one: the 5 MWt provided by the typical FF unit to the airstream is not going to generate the amount of thrust that the 5 MWe gets from the propeller.

two: the pinch is, perforce, insulated by a vacuum. You’ve got to get the helium out of the core and to a cold plate exposed to the airstream first…

Undoubtedly there will be optimized aircraft engines as people develop the tech after functional FFs are introduced. Things I couldn’t dream of now…

The point here being that, given the standard starting stats for the FF, right off the bat you’ve enabled a revolution in the air freight business and air passenger transport won’t be far behind…

[Author]

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