Quote
"Investigating a catastrophic crash, e.g. around a crater, would be extremely hazardous. An urban crash even more so."

First of all my apologies for the spelling of "nuclear" in my original message . . . .
What do you mean "crash around a crater" and "An urban crash" ?

These scenarios :-
https://cimg5.ibsrv.net/gimg/pprune....02373697f7.jpg
https://cimg7.ibsrv.net/gimg/pprune....419558e2e0.jpg

EXSimGuy. Nice to hear the word "Thorium" used. As you say, a much better fuel for reactors, but any research/development seems to be very low key

There's a company (British I think?) already building a first test installation out in the far east ("big countries" have too much paperwork, much aimed at uranium systems).

I've had zero luck finding information on these operators who are already using electric aircraft for passenger service - do you have any links or company names?

NIL BY MOUTH -- Those pics look suspiciously like aviation incidents rather than nuclear, As an "aviation person" I'm sure you are aware that one is far more likely to be in an accident on a highway taking you to an airport than on the flight you are about to take. in the same way, you are far more likely to be injured on that flight than from living near a nuke power station.You remember the incident in the Fukushima Nuclear Power Plant ? The number of casualties from there can be counted on the fingures of one hand.
Do you remember the newspaper reports about the nuclear American warship that exploded? No? That's because it has never happened :ok:
I used to be quite "anti nuke, but mainly because of the "thousand year trail" of the so-called" "spent" fuel. However with Thorium as a fuel the efficiency is much higher and the waste iis only dangerous for a few tens of years.l

Apologies if I misunderstood your post, I thought that you were hypothesising that a nuclear reactor could power an aircraft!
My reply was merely pointing out the inherent danger of an airborne nuclear reactor impacting the ground or a city at a high velocity.

Apart from the "electric flying-boat" mentioned a couple of posts earlier, I'm almost convinced that a short haul company in northern Europe was already taking pax distances of a couple of hundred by electrics, but I guess I had that wrong as a bit more searching today has brought up 4 "May 2022 — Textron paid $235 million for Pipistrel, which produced the world's first electric-powered aircraft to be internationally certified as being safe for passenger flight" (19-seater)
Here in Europe, EasyJet’s partnership with U.S. startup Wright Electric has led to development plans for the Wright 1, an all-electric, 186-seat commercial passenger jet with an 800-mile range that’s targeted to enter service around 2030. Up sooner still, Wright Electric additionally announced in November plans for an electric 100-seater, the Wright Spirit, due out in 2026

“ Targeted to”, “ Have plans for” . I guarantee their plans require a huge increase in battery technology they just assume someone else will achieve. Till someone does, they can plan and target all they want, but we won’t see an actual aircraft on the tarmac.

And, err, pipestrel has a 19 seater? Well, no. They have a certified TWO seat aircraft that has a safe endurance of about an hour.

have a read of the following, it details the nuclear powered bomber that the Russians actually flew.

https://interestingengineering.com/t...ded-in-failure

Except that, according to your link, it didn't fly while nuclear-powered.

The US had a test reactor working inflight on an airplane however it did not power this airplane.

Thanks for the amendments -- Seems there's been a bit of twisting with the electric aircraft stories. There have been a lot of improvements in batteries for electric cars, and a lot more just in "lab final analysts". Obviously this is largely driven by the car market, but oneoff those lab experiments could, maybe, emerge with a bayyery that could be used in bugger passenger loads of longer tange . . .
However, if I was a gamblng man, I'd still place my bet on a hydrogen system for bigger aircraft and significantly longer range.

I'd say you bet is correct, but with a LOOONNNGGG wait time. Battery development is concentrating on cost and charge time, as they are important in land vehicles, while energy density, which is what would be needed to make transport aircraft practical, has largely plateaued.

And the punch per pound improvements required for aviation would be like 40 times better or similar, far from getting available soon.

That's interesting. Why would the battery change weight?

Because, for instance, it's a lithium-air battery that captures oxygen from the air and it increases its anode+cathode weight with about the ratio (16+7)/7 = 3.29
(oxygen+lithium)/lithium
The end product of the redox reaction in lithium-air reaction is Li2O2.

I very much doubt that any electric plane based on lithium-ion battery technology will be a commercial success.

I believe that the first such success will be based on Lithium-Sulfur battery technology and will start in 3-5 years time.
Recent research breakthroughs around monoclinic gamma-phase sulfur appear to ease the main stumbling block of Lithium-Sulfur battery development (generation of polysulfides).
https://www.researchgate.net/publica...Li-S_batteries
And I believe that the distant future winner will be Lithium-air battery technology.

To put things in perspective, the raw specific energy of fossil fuels is as high as 12 kWh/kg.
But only a fraction of this energy can be used to propel an airplane because of the thermic engine efficiency limitation, the propeller efficiency limitation, the weight of the engine, fuel tanks and hoses,
If we aim at comparing apples to apples, we should consider the usable mechanical power applied to the propeller shaft divided by the total weight of the propulsive system including the fuel weight.

If I take a modern turboprop engine like the PT6A-140A, for instance on a Cessna C208B (the aircraft doesn't have to be aerodynamically efficient for the sake of this comparison ;-) ),
the engine has a max cruise ESHP of 911 hp or 680 kW for an EFSC of 0.566 lb/ESHP/hr.
So, a flight of 3 hours at max cruise settings will consume 0.566 * 911 * 3 lb = 1547 lb of Jet A1 or 702 kg of fuel producing 2040 kWh of mechanical energy.
If we assume a propulsive system weight of 385 lbs + 143 lbs + 15 lbs + 15 lbs + 1547 lbs = 2105 lbs or 955 kg.
(engine_with_std_equipment + propeller + empty_tanks + other + fuel)
The useful mechanical energy divided by the total weight is 2040 kWh / 955 kg = 2.14 kWh/kg
So, we are just at 18% of the theoritical specific energy of Jet A1 and the PT6A-140A is one of the most efficient propulsive system for small airplanes.

If we do a similar calculation with a propulsive system based on Lithium-ion batteries, we start with a theoritical specific energy of up to 0.295 kWh/kg (Tesla's 4680-type battery cell).
This is only 2.5 % of the theoritical specific energy of jet fuel.
But, as with a thermodynamic engine, what counts is the usable specific energy.
An efficient light-weight (and expensive) electrical engine of 680 kW weights about 100 kg and has an efficiency of 90%.
For a complete battery pack, with electronic controllers, I'll extend the best battery pack specific energy available in Tesla cars : 0.160 kWh/kg.
For 2040 kWh, the pack should weight (100/90) * (2040 kWh / 0.160 kWh/kg) = 14,170 kg (not sure it fits in the plane ;-) )
I'll use the same propeller as for the PT6A-140A at 143 lbs or 65 kg and I'll add 15 kg of cables.
The total propulsive system weight is 100 kg + 65 kg + 14170 kg + 15 kg = 14,350 kg
The useful mechanical energy divided by the total weight is 2040 kWh / 14350 kg = 0.142 kWh/kg
This is just slightly less (11%) than the battery pack specific energy.
We are now at 6.6 % of the useful mechanical specific energy of jet fuel.
The lame situation of electric energy compared with fossil fuel energy has improved by a factor 2.7 when leaving theoretical specific energy comparison for useful mechanical specific energy comparison.
The 6.6 % of electric compared to fossil fuel means that we can expect that, all other things being equal, we can expect that lithium-ion electric fuel brings a reduction of range and endurance that is only 6.6 % of fossil fuel range and endurance.

Let's evaluate the prospects of Lithium-sulfur batteries and Lithium-air batteries.
The theoritical specific energy of lithium-sulfur batteries is expected to be around 550 Wh/kg.
If we apply the same energy density decrease ratio as for Tesla battery packs, the battery pack specific energy should be around (0.160/0.295) * 0.55 kWh/kg = 0.30 kWh/kg
The weight of a 2040 kWh battery pack will be (100/90) * (2040 kWh / 0.30 kWh/kg) = 7560 kg (about half of a lithium-ion equivalent)
The weight of the propulsive system of my electric Cessna Caravan will become 100 kg + 65 kg + 7560 kg + 15 kg = 7740 kg
The useful mechanical energy divided by the total weight is 2040 kWh / 7740 kg = 0.264 kWh/kg.
We are now at 12.3 % of the useful mechanical specific energy of jet fuel and 12.3% of the fossil fuel range and endurance.

For lithium-air batteries, a prospective assessment is more difficult.
The theoritical energy density is somewhere between 5 and 11 kWh/kg, depending on the nature of the electrolyte and the nature of the catalysts present at the cathode.
The higher end of the range is very close to the theoritical energy density of fossil fuels; so this is promising.
But, actually, the cathode absorbs oxygen during the discharge and becomes heavier as Li is transformed in Li2O2. the weight increase of lithium is with a factor 3.29.
As the discharged weight of the battery is as important as the charged weight of it, this ratio impacts the potential energy density of the battery.
It is thus reduced to a range between 1.5 kWh/kg and 3.3 kWh/kg.
If we compute as above the useful mechanical specific energy, we have:
Battery pack specific energy : between 0.814 kWh/kg and 1.79 kWh/kg.
Weight of a 2040 kWh battery pack : between 2785 kg and 1265 kg.
Total propulsive system weight : between 2965 kg and 1445 kg.
The useful mechanical specific energy : between 0.688 kWh/kg and 1.41 kWh/kg.
Percentage of useful mechanical specific energy of jet fuel : between 32% and 66%, with an equivalent relative range and endurance reduction.

I believe that below 10% of the theoritical fossil fuel range and endurance, nothing is commercially viable.
The 12.3% of Lithium-sulfur is just above this threshold and could be viable for niche markets.
The 32% to 66% anticipated performance of lithium-air would make it viable on markets where it can compete with synthetic fuels, in a situation where fossil fuels are so expensive that synthetic fuels replace them for aviation.

The point of fuel made from biomass from algae rather than extracted from the ground is that the former is carbon neutral, while the latter is not. The algae consume atmospheric CO2 to grow, so that when burnt, an equal amount of CO2 is released back into the atmosphere, so no net increase in CO2 emissions. Burning fossil fuel releases sequestered CO2 into the atmosphere for a net increase in atmospheric CO2, which is a bad thing.

A quick note: I realised that the 18% I quoted above may look to be the energy efficiency of the PT6A-140A engine.
That's untrue; it's a ratio between apple and pears.
On one side, the useful mechanical energy per kg of the entire propulsive system and, on the other side, the chemical energy per kilogram of fuel.

The efficiency of the engine is actually hidden in the ESFC number.
0.566 lb/ESHP/hr is equivalent to 0.25673328 kg per 0,735499 kW per hour,.
That's 0,735499 kWh / 0.25673328 kg = 2.86 kWh/kg or 23.9% of the energy contained in the fuel that is converted in mechanical energy provided to the propeller shaft.
(Actually, ESFC is about mechanical energy to the shaft plus mechanical energy from the exhaust)
And 23.9% is damn good for a small engine.