Electrical Engines.

[Sky Captain]

I think there was no shielding on Pluto missile, that certainly helped to have great performance. If you had a fighter designed around the same engine you would have to add tons of shielding or pilot would not survive sitting near naked reactor. You would probably end up with very expensive, difficult to maintain fighter with mediocre performance after adding shielding.

[Zixinus]

I think they ended up unable to do it, hence one of the reasons Project Pluto was eventually abandoned. You could make a nuclear-thermal exhaust engine that relied on heat exchange though, namely NERVA. But that used the reactor heat's direct, rather than gaining it from electrical generation.

[Imperial528]

Pluto's engine operated through direct thermal exchange, and the test engines worked as intended by their design. Pluto was cancelled because of advances in rocketry/avionics making ICBMs feasible and from fears that it would inspire the Soviets to build one as well.

[Imperial Overlord]

Pluto's engine operated through direct thermal exchange, and the test engines worked as intended by their design. Pluto was cancelled because of advances in rocketry/avionics making ICBMs feasible and from fears that it would inspire the Soviets to build one as well.

Pluto also got canned because building and testing prototypes meant meant flying and very possibly crashing a nuclear rocket over friendly territory multiple times.

[Sea Skimmer]

Thanks, that's very interesting. So essentially a ducted fan electric aircraft would be useful in short to mid range passenger and cargo flights where performance penalty of having no weight loss during flight may be acceptable, but high performance military and long range comercial planes would best remain using conventional jet engines.

Pretty much, and Airbus and a few other companies are seriously considering electric short haul airliners, 300nm range and 30 seats appears feasible with present-near future technology. But more or less, this is an order of magnitude less performance then we had no trouble pulling out of 1970s dirt burning technology. In the further future ~100-200 seat electric short haul planes may be feasible, but this relies on favorable developments of capacitor and battery technology capable of being used as part of the aircraft structure, and the intended range is still only a few hundred miles. Such as London to Paris, totally realistic, but even so much as London to Berlin not really.

Military aircraft are also interested in structural composite capacitors, because this way you could say have a laser equipped fighter using its own wing as the power buffer to make the laser work in very high power bursts. High Power Microwave weapons on small air frames could also benefit.

Seems that if development of nuclear aircraft would continued during Cold War engineers would faced similar problems of heavy engines, reactors, shielding and performance penalty of having no weight loss in flight ruling out high performance aircraft.

Nuclear power operates on a different basis; very high speed-range performance is possible but the minimal empty weight of a viable manned aircraft will be very very high, and higher still if you also want a very large payload It would also be tremendously expensive, and unlike an electric plane you won't save any money in operating costs.

In this one case I'm not sure it would matter; remember that Project Pluto was intended to develop a cruise missile powered by a nuclear ramjet. The proposed mission profile included a low-level supersonic dash towards the target, which I think qualifies it for "high performance". The reactor would have produced so much power — potentially, for months — that any sort of conventional performance penalty calculation was sort of irrelevant.

It couldn't fly for months, the reactor would self destruct in flight slowly, and the electronics on board would progressively degrade from lack of full radiation shielding.

To a certain point varying reactor power would extend range/endurance time; actually maximum power and speed were limited by how hot the atmospheric air being sucked in were, the colder the better, which is why you seed anything from mach 3+ to mach 4.2 given as the top speed, it would in fact vary by that much depending on the air temp. Mach 4.2 IIRC assumed -100F air, which was plausibly at high altitude above the north pole heading for communism.

Its also worth point out that in missile terms Pluto was huge, 60,000lb missile with 10,000lb payload. But unlike a conventional powered missile it would have been very difficult to scale down the Pluto concept to a much smaller payload and thus way more affordable missile. Even in purely military terms the 'sense window' of Pluto was limited.

I think there was no shielding on Pluto missile, that certainly helped to have great performance. If you had a fighter designed around the same engine you would have to add tons of shielding or pilot would not survive sitting near naked reactor. You would probably end up with very expensive, difficult to maintain fighter with mediocre performance after adding shielding.

Basically if you want shielding and a man rating its going to turn into a bomber, nuclear aircraft tended to be at least 250,000lb-300,000lb MTOW kind of planes even on paper, and I suspect going much lower then that kind of size range would rapidly turn into an aircraft with no useful payload. Due to spectral hardening problems reactor shielding requirements are non linear, any amount of fisssion will require a very heavy shield, and while more reactor power does increase requirements after a point it's silly not to just design the frigging plane as big as frigging possible so you can carry a bigger fraction of your weight as weapons. Also physical distance does matter for shielding even when your talking about being in the same plane as an nuclear reactor, so again size just makes life easier.

That also makes it easier to integrate bunks for the crew so you can exploit your tremendous endurance. The big advantage of a nuclear powered bomber would have been you could scramble them to an alert, and then keep them on airborne alert for days or weeks even before they'd inevitable need maintenance.

...this eventually led to the LOGICAL idea of nuclear powered airships as bases for the MX misssile with shuttle aircraft to swap out the crewss without landing.

Though for LOL Boeing or someone, once designed a nuclear powered HELICOPTER that worked fine except that the pilot would get 50 rems per hour of radiation.

Pluto also got canned because building and testing prototypes meant meant flying and very possibly crashing a nuclear rocket over friendly territory multiple times.

Yeah that was a big killer. Even if we didn't give a damn about environmental problems the only way to test such a large ramjet was airborne flight tests. Building a supersonic wind tunnel on that scale that could sustain high mach airflow wasn't feasible, nor are supersonic wind tunnels ever full accurate models anyway. The huge amount of oil pipe used to store like ~3 minutes of air for the actual Tory-II test shows what a problem this is.

Full scale flight tests of whole expendable nuclear reactors would have been incredibly expensive, and been plagued by the constant problem of....this missile was also supposed to use some real bleeding edge guidance and control equipment including the first TERCOM ever (its own iffy point if that was gonna work well enough for the missile in that era, Tomahawk came much later, much slower, not exposed to radiation ect.... and required it to function over much shorter ranges) which means you could count on lots of flight tests failing for avionics reasons. Each one requires throwing away a nuclear reactor and an airframe that was literally gold plated internally for radiation and thermal shielding the air frame around the reactor.

[Sea Skimmer]

Hey for random, someone got the Tory-II test plan declassified
http://www.dtic.mil/dtic/tr/fulltext/u2/350533.pdf

So turn out the plan for trying to do more realistic ground test was to dig out giant underground chambers to store the compressed air and they'd gotten a far as drilling test wells to look for suitable rock (with it look like poor luck) by the time the project died. To give an idea of how much time it would take to compress all the air in the first place, the goal was to be able to run the reactor at simulated mach 3 for 90 minutes every 15 days! That' using a 4000hp diesel.

They've also got a diagram showing if the underground storage didn't work and they had to go with MOAR PIPES that the area covered by the pipe farm would be x10 bigger and cost.... 67 million dollars. That doesn't count the new test stand or the air compressor itself. Note this is when the most expensive fighter in the world was the F4 Phantom and it cost around 3.5 million each and the total Pluto cost by the time it was killed was 260 million.

[JI_Joe84]

Their is a company and research group called pipistrel that is now building a electric plane. Its only use because of the 1 hour range and incredible cost is as a trainer, avgas is 4.25 dollars and small planes use a lot of it.
Four seaters usually have around 100 gal. Fuel tanks.
They have a hybrid set up in testing using a electrical motor powered by a small gas engine as a primary power unit. Initially it looks good, though the FAA still has a rule on the books that says all small aircraft are to be powered by a reciprocating engine.
Siemens is the name of the research group.
Their is also hypersolar, a group working on making hydrogen from salt water and sunlight, efficiently.
I must say hydrogen is the way to go. Batteries are only about 1/10th the energy density of hydrocarbons. That's no joke. The newest designs will be in testing for a long time because if you want a long lived battery you have to test it for those time scales in order to prove its safety and performance. It will take too long to develop the batteries just to improve the tech to the next logical step for them to be any good at defeating climate change.

[Starglider]

Initially it looks good, though the FAA still has a rule on the books that says all small aircraft are to be powered by a reciprocating engine.

What rule is this? There are lots of general aviation (light aircraft) turboprops.

[JI_Joe84]

Single engine Turbine aircraft almost always carry more than 4 passenger's they are in a class between the piston singles and Turbine ( they mean turbo-fan) engine's.
There was a rule stating that any small plane (back the 4-6 seats) would be powered by a continental engine and they were total dicks. Absolutely refused to update any thing, reason? SAFTY! They always said it was for safety.
Really pissed off some people but that meant less people they didn't like for their flying club.
Also it is possible to get a waver or special certification on a per aircraft basis to use a turbine engine in little planes, this is what pipistrel is counting on for their Hybrid power plant option on the Panthers.
They have some info on YouTube if you don't want to wade through the specs on their web site.
Now days a small plane is 2-6 seats and 130 mph to about 300mph indicated air speed. IAC is more handy for us than ground speed, it will differ.

[Starglider]

I don't know who you're talking about, but apparently it isn't the US Federal Aviation Administration.

[JI_Joe84]

I don't know who you're talking about, but apparently it isn't the US Federal Aviation Administration.

It is the US Federal Aviation Administration. I just can't remember the exact F.A.R. # it is under, it does still say that small planes will be powered by a reciprocating engine.
You might be confusing the Experimental class of aircraft with Certified Aircraft.
If a pilot registers their aircraft as an experimental then you can have it equipped how ever you want, the only string attached is you have to build it. You can not buy it from the factory equipped with unuproved equipment.

[Sky Captain]

If anything electrical plane should be more reliable than gas powered. There are only one moving part in electrical motor while reciprocating engine have pistons, valves, rods, crankshaft, fuel system, cooling system, all potential sources of breakdown. There is little that can go wrong with electric motor. It can burn out and if motor is very old bearings can fail and cause motor to stuck. Both of those failure modes can be easily prevented. Motor control electronics probably would be weak spot, but it should be possible to have two redundant controllers.

[JI_Joe84]

If anything electrical plane should be more reliable than gas powered. There are only one moving part in electrical motor while reciprocating engine have pistons, valves, rods, crankshaft, fuel system, cooling system, all potential sources of breakdown. There is little that can go wrong with electric motor. It can burn out and if motor is very old bearings can fail and cause motor to stuck. Both of those failure modes can be easily prevented. Motor control electronics probably would be weak spot, but it should be possible to have two redundant controllers.

I'm not saying its right, just saying its their excuse for giving a monopoly to continental. It also will make for legal hurdles for any one trying to get better engine's or completely different power plant technology's to market.
It's not impossible, Lycombing has developed electronic ignition and fuel injection for aviation piston engine's, so there is a president since the aviation admin. allowed it on the market as a certified engine technology.
The argument is with all these older commercial pilots going to retire soon we need to attract more young people into the pilot seat, in order to do that we need to update technology and make it easier for people to get the flight hours in.
You can not just go to a flight school pass the tests, do the flying test and go on to multi engine/complex rating, you must have lots of hours in a simple single engine plane before you can even apply. Once you do those other two endorsements you must be type certified for the commercial aircraft you are going to be flying and even then you are just a extra set of hands for the capt.
So it didn't make sense to all these young people that their first plane would be some ancient carburated thing.
That could be used to argue for electric motors in hybrid and batteries electric set ups. Its coming but its painfully slow and batteries are not going to cut it as they are right now so less incentive to get this done.

[Sky Captain]

One more application of electrical power when better batteries emerge are stealth aircraft. There is very little heat from electric motor while more than half of power output from jet or piston engine is waste heat. In theory electric plane would have tiny IR signature making it hard to spot with IR sensors,

[JI_Joe84]

True but with out a better way to store electrical energy the point is still moot.
How are we going to bridge this gap?