[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…

[zapkitty]

vansig wrote:

A cartridge that sits in the vacuum side of the system and can be inserted
through an external hatch in the module without ever being brought into a
hab… that would go over well despite the extra expense involved…

i see no good reason for any of such a system to be in the hab.
it should be protected by a whipple shield, but otherwise entirely external

For the “let’s get acquainted with this gear in zero g” part of the development cycle it will be somewhat useful to be able to pressurize the power module on demand for access and repair work…

… and it’s highly likely that such access will be needed before you’re ready to turn station power over to the module 🙂

… after all these years spacewalks are still hazardous endeavors to be avoided wherever possible.

[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…

[zapkitty]

vansig wrote: also, at 5 pinches/second, anode life would be 66 times longer than it is at 330 pinches/s.
a 90-day maintenance schedule would be extended to 16 years

All that remains is handling the fuel.

If it’s still decaborane then there will be contamination control issues. Not the
NIMBY FUD discussed elsewhere but the simple fact that the ISS ecosystem
extends exactly just as far as the air revitalizer in the next module over from
yours. Contamination by any neurotoxin, however minute the traces, can not
and will not be allowed.

If the reactor can be refueled by a cartridge that is isolated from the module
air system and offers no chance of blowback either when changing cartridges
or in case of cartridge failure… that would be a big help.

A cartridge that sits in the vacuum side of the system and can be inserted
through an external hatch in the module without ever being brought into a
hab… that would go over well despite the extra expense involved…

[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…

[zapkitty]

So, as I said over on the FF jet engines thread, the standard FF setup would be
giving 15151.51 joules of net power per pinch.

At 5 Hz that would be 75,757.55 watts… 75.75 kWe is plenty to run ISS on with
ample margins for growth.

(Those huge solar arrays spend a lot of power during the “daylight” portion of
each orbit charging up some very large battery packs for the “night” portion of
each orbit)

So a test unit that could take ISS from proof-of-concept to current power levels
to 5 MWe as the tech is proven, radiators are developed, and a backup
module installed.

All without the overhead and upkeep of said same huge solar arrays, their rotating
joints, and the MMOD erosion that inevitably afflicts them.

[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]

Breakable wrote:

Eric stated in the Google Talks video that the core cools down to background radiation levels in 13 hours, citing a half-life of something like 20 minutes. He compares the starting radiation level to a room full of school kids- not much compared to fission plants

I think it should depend on how long you run it.

Why should it?

To simplify it a bit… if the reactor is creating radioactive byproducts with a certain (short) half-life then those products will decay regardless of whether the reactor is operating or not. Thus the most recent byproduct made is what will govern the length of the elevated radiation level in the FF casing.

In other words if you started a standard fission reactor and ran it for only a day you’d still be dealing with radioactive byproducts with a half-life measured in centuries… byproducts that can only be called nuclear waste as they will outlast the lifetime of the reactor that created them many times over.

[zapkitty]

Breakable wrote:
I think the first prototypes as well as first generation units will be low frequency to reduce complexity of radiation and thermal management.

… apparently there is a caveat brought up by vansig of capacitor leakage rates.

Such leakage rates tend to climb quickly when the capacitors are running at full charge.

I don’t have any details on the FFX caps and so I don’t know at what frequency this becomes a problem for those particular caps…

… but it’s certainly theoretically possible to run at such a low frequency that the caps leak just a little too much between shots to fire the next pinch.

But is this a problem for these particular caps at 100 hz? 10 hz? 1 hz? Once per fortnight?

I guess the solution to this “throttling” limit would be to use bigger caps so you aren’t running them at full charge.

Are the FFX caps going to be running near max to achieve the desired goals? Could be. If so then in that case running at a lower frequency could be more of a problem than a solution.

But to have an FF unit able to run efficiently at less than a megawatt would be very useful in space applications. To have one that could run at less than 100 kilowatts would enable plug-and-play adaptation to current large spacecraft designs 🙂

[zapkitty]

vansig wrote:

I can haz sub-MW FFs?

the lower bound is about capacitor leakage rate; the upper bound, about cooling.

… which gets very particular about the exact specs and application of the capacitors
in question. Anyone got a part number for the FFX caps? 🙂

[zapkitty]

… dirigibles… dirigibles with FF units providing the power to achieve 600 mph airspeeds at altitude and with the waste heat from the FFs applied to the helium to provide extra lift… dirigibles that can then reduce lift without venting helium and land vertically under power in any crosswinds that a jet can handle… come to the dark side… it is your destiny… 8D

[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!

[zapkitty]

So if FFs can be run at say… 75kWe… without issues then that would make
integration into current spacecraft architectures much, much easier… and yet
would still give ample opportunity for expansion and growth if designed with
such growth in mind…

I can haz sub-MW FFs?

[zapkitty]

vansig wrote:
do remember that focus fusion power is entirely dispatchable: there need be no excess power, at all,
since you can adjust number of pinches/second as demand requires.

I thought there was an efficiency hit when running at less than 330hz?

vansig wrote: so, really, the question becomes
whether it is cheaper, or safer, to deliver a fusion generator, and install it, than to distribute power to a needy neighbour over wires.

… and at the beginning of deployment you will have both the demand for any
excess power that you can spare and you will have the means to distribute it.

So again… the situation will resolve itself.

That is, unless we let our lords and masters deliberately screw us over in their
inevitable attempts to enrich themselves at our expense.

[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)

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