Nuclear Powered Helicopters

[All Seeing Eye]

Hear me out will ya.

If you ever watched Captain Scarlet or Doctor who they both have these sort of like flying fortresses. Well in reality they would be impossible mainly because of the level of fuel consumption required to just keep them in the air.

Then I got to thinking, the rotary blades needed for it to keep it in the air only need electrical current to power them and electrical current does not need to be generated by fossil fuel but can instead be generated by nuclear power.

Obviously should there be any accident then nuclear fuel would explode everywhere but that does not need to be the case. If the reactor is kept in a protective shield the reactor would fall to the ground and no nuclear fuel or waste would go everywhere.

Also as a military vessel it could be designed so it does leak fuel and waste everywhere if it ever blew up as this would mean it could fly into an enemy country and they would not dare attack it for fear of a nuclear catastrophe over their own land.

Thoughts? Comments?

How high can helicopter style rotary blades go? Imagine an aircraft carrier tha'st instead in the air!

 

[Lindley]

There is actually a push towards all-electric aircraft at the moment. In fact, the first "eternal" solar-powered UAV which never needs to land just had its proof-of-capability flight recently.

However, such aircraft still have significant weight limitations. Even getting something the size of an aircraft carrier into the sky would be a challenge, much less doing so with purely electrical power.

 

[Robert Maxwell]

I think the biggest problem with an airborne nuclear plant would be the fact that it has to heft its own weight plus the rest of the structure. Nuclear plants are big and heavy.

If I am thinking about this correctly, you'd need to generate 9.8 watts per kilogram per second just to counteract the force of gravity. I checked around and it looks like the largest capacity of any nuclear plant is 1.6GW. This means the largest mass you could even cause to hover would be about 163 million kilograms.

I'm having a hard time finding numbers to put that in perspective. Anyone have any idea how much a full nuclear plant weighs?

 

[Lindley]

Well, for perspective, one website said that a Nimitz-class aircraft carrier weights 97000 long tons, or about 98.5 million kilograms.

Keep in mind, though, that the "largest capacity" is probably much more than a typical carrier boasts, and that some of that power needs to go to other ship's systems.

 

[Robert Maxwell]

Wow. Yeah, sounds like hefting any kind of permanent structure into the sky is completely untenable from an energy standpoint, unless we develop antigravity or something.

 

[Ablative_Oberth]

Nuclear aircraft flew in the 1950s. They weren't practical then.

Couple of points to consider: There are direct cycles that avoid the whole steam-and-condenser shabang. They weren't developed much past experimental stages. More or less you heat a gas in the core, drive your turbines with it, and pump the cool gas back into the core. Back in the 1960s when the technology was explored there were issues with material corrosion and other problems... water/steam cycles won out the development

Also there are direct thermoelectric conversion options, like the ones that power deep space probes like Voyager.

Then think about recent advances in shielding: Shields need not be bulk lead and concrete anymore.


Such a beast could be built and flown but until we as a society get over our collective "Nuclear is Bad" mentality we're stuck.

 

[scotpens]

There is actually a push towards all-electric aircraft at the moment. In fact, the first "eternal" solar-powered UAV which never needs to land just had its proof-of-capability flight recently.

However, such aircraft still have significant weight limitations. Even getting something the size of an aircraft carrier into the sky would be a challenge, much less doing so with purely electrical power.

Aren't electric motors heavier than piston or turbine engines of equivalent horsepower?

Nuclear aircraft flew in the 1950s.

In what alternate reality did that happen?

There were several proposals for nuclear-powered aircraft in the 1950s. None of them got past the drawing-board stage.

Convair Atomic-Powered Bomber Concept

 

[hyzmarca]

If you want to build a huge air vehicle you're better off with an airship. An airship's lifting capacity is proportional to its volume and volume is a cubed value. Proportionantly, gigantic airships lift better than smaller ones. The same is not true of helicopters.

There is, however, little point. Helicarriers and other flying fortresses defeat the point of air power and are nothing but big flying targets.

 

[scotpens]

^ Which is why the Navy doesn't use blimps anymore.

 

[Ablative_Oberth]

Nuclear aircraft flew in the 1950s.

In what alternate reality did that happen?

There were several proposals for nuclear-powered aircraft in the 1950s. None of them got past the drawing-board stage.

Convair Atomic-Powered Bomber Concept

We flew a B-36 with a working nuclear reactor aboard it, twice.

The Russians went so far as to actually build and fly a nuclear airplane, which fried it's crew.

 

[RedShirt]

In what alternate reality did that happen?

There were several proposals for nuclear-powered aircraft in the 1950s. None of them got past the drawing-board stage.

Convair Atomic-Powered Bomber Concept

We flew a B-36 with a working nuclear reactor aboard it, twice.

Yes the reactor was operational but it was not used to power any aircraft system. It was just a tested to see how the aircraft responded to radiation.
The reactor had 1MW output and was air cooled.
47 flights were made between 1955 and 1957.

http://en.wikipedia.org/wiki/Convair_B-36#Experiments
(I know, I know... not the end all, be all of sources)

 

[scotpens]

The Russians went so far as to actually build and fly a nuclear airplane, which fried it's crew.

Can you cite a source for the statement that it “fried its crew”?

Like the U.S., the Soviets only got as far as building a nuclear test-bed aircraft, the Tupolev Tu-95LAL. They never flew a plane with actual working nuclear-powered engines.

Soviet Experimentation with Nuclear Powered Bombers

 

[STR]

^Probably a myth, but given how Hotel, Echo and November Class nuclear subs irradiated the crew with fatal levels of gamma radiation. Rather than decommissioning the subs, they would keep the entire back area of the sub (nearest to the reactor, which is generally 3/4 of the way from the bow) empty as much as possible.

If I am thinking about this correctly, you'd need to generate 9.8 watts per kilogram per second just to counteract the force of gravity. I checked around and it looks like the largest capacity of any nuclear plant is 1.6GW. This means the largest mass you could even cause to hover would be about 163 million kilograms.

I'm having a hard time finding numbers to put that in perspective. Anyone have any idea how much a full nuclear plant weighs?

All nuclear plants are extremely small given their power output. The core (pile) of the reactor you describe would fit in your living room, the steam turbines take up vastly more space. However, that doesn't include safety systems and radiation shielding. Plus, if you're going to lift it into the air, you need to crash proof it with a very strong containment vessel. I wouldn't be surpised if the whole system for a 1.6GW reactor is in the area of 20,000 tons, which of course isn't mobile. Mobile reactors top out at the 200MW level of the A4W and A1G reactors used in Nimitz Class aircraft Carriers. This are much smaller (the whole thing will fit in a two bedroom home and weight just a thousand tons, less if you drop the output to less than 100MW), but their trade off is that they run on weapons grade uranium (90% U235) vs commercial grade (4% U235).

 

[constovich]

Going to such a enrichment provides two benefits for a mobile reactor 1) you are not carrying around the effectively dead weight of U-238. 2) you can run your reactors for years between refuels.

On Nimitz and other modern nuclear powered vessels, they are built, tested and ran for 40 years then decommissioned. There is no refueling. Because you do not have to open the core for reload, it also supports making the reactor pod self-contained for accident reasons.

Also, 90% still isn't "weapons grade" because it is still not enriched enough to allow for a run-away fission chain reaction. That doesn't occur until 95-98% enrichment.

 

[trekkiedane]

Then I got to thinking, the rotary blades needed for it to keep it in the air only need electrical current to power them and electrical current does not need to be generated by fossil fuel but can instead be generated by nuclear power.

While it might be possible to build an electric motor, the added complications and weight makes it very impractical, I've never heard of any suggestion (apart from yours) to do so.

In the 1950s, interest in the development of nuclear-powered aircraft led GE to experiment with two nuclear-powered gas turbine designs, one based on the J47, and another new and much larger engine called the X211.

The design based on the J47 became the X39 program. This system consisted of two modified J47 engines which, instead of combusting jet fuel, received their heated, compressed air from a heat exchanger that was part of the Heat Transfer Reactor Experiment (HTRE) reactor. The X-39 was successfully operated in conjunction with three different reactors, the HTRE-1, HTRE-2 and HTRE-3. Had the program not been cancelled, these engines would have been used to power the proposed Convair X-6.

linky
But, of course, Ablative_Oberth already posted about this.

 

[STR]

Going to such a enrichment provides two benefits for a mobile reactor 1) you are not carrying around the effectively dead weight of U-238. 2) you can run your reactors for years between refuels.

On Nimitz and other modern nuclear powered vessels, they are built, tested and ran for 40 years then decommissioned. There is no refueling. Because you do not have to open the core for reload, it also supports making the reactor pod self-contained for accident reasons.

Also, 90% still isn't "weapons grade" because it is still not enriched enough to allow for a run-away fission chain reaction. That doesn't occur until 95-98% enrichment.

1) CVN reactors are refueled once in the ships lifetime, aside from Enterprise which has been refueled more than once. Nimitz herself went in for Refeuling and Complex OverHaul (RCOH) in the late 90's. Currently, there are no carriers undergoing RCOH, but the Roosevelt is due next year. Ohio class SSBN's also get refuelings, as did most of the nuclear powered cruisers (aside from the Virginia's, but they were victims of bad timing). It's only the attack subs that aren't worth the cost of refueling.

2) Given the mass and energy involved, the cost of hauling around a couple of extra tons on U238 is not worth the cost of separating it out completely. Natural uranium is only 0.7% U235, which makes it an extremely rare commodity compared to natural or depleted uranium. It is also not entirely dead weight as some of the remaining U238 absorbs neutrons and becomes fissionable Pu239.

3) The exact level of refinement for both naval reactors and nuclear weapons are classified and vary depending on the specific model. Enterprise's A2W reactors are "above 93%" U235. If it makes you happy, I'll change my term to "near weapons grade."

 

[All Seeing Eye]

Nuclear powered Hexacopters. Hexacopters would be exceptionally safe.

 

[Trekker4747]

Nuclear powered Hexacopters. Hexacopters would be exceptionally safe.

About as safe as an AMC Gremlin that is.

 

[JustAFriend]

Aren't electric motors heavier than piston or turbine engines of equivalent horsepower?

Nope.

I fly electric radio-controlled planes and for the same power output they are now lighter than equivalent gas power planes.

Fastest one I've personally seen so far is an electric jet (ducted fan) that goes over 200mph.

Biggest electric prop plane I've seen so far had a wingspan near 25feet with motors putting out 10,000watts.

There are electric helicopters of all sizes, too.

Here's a giant-scale P-51

 

[sojourner]

^It's not the motors that weigh a lot, it's the batteries. How long can those planes fly compared to petrol powered aircraft?