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Comment by linsomniac | Hacker News Reader

Slightly related: I wasn't aware of this until last year, but at one point nuclear-powered jet aircraft were a thing. Think cold-war jets, always ready to counter if the other side strikes, that could stay aloft for a month or more.

The issue is that weight is the enemy of flight, and nuclear shielding is heavy. The US was working on distributed shielding: instead of being centralized around the reactor, messing with the CG, it was spread out.

https://en.wikipedia.org/wiki/Nuclear-powered_aircraft

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Ah, my favorite topic. There was a $1B (1950s dollars) program in the 1950s to make these. It led to vast nuclear development. Some good reading and pictures on it are in this huge report [1]. I particularly like this image: https://whatisnuclear.com/img/nuclear_rocket.jpg

Another fun fact, if you've heard of molten salt reactors (MSR) or the associated thorium fuel cycle, you should know that almost all of the tech development related to those projects came from the program to develop nuclear-powered aircraft. The first MSR was called the Aircraft Reactor Experiment (ARE) [2]. The second one, the famed MSRE, was built in the building that had been entirely funded and built for the air force project, using mostly parts and certainly the expertise built by it.

[1] https://www.osti.gov/biblio/1048124-comprehensive-technical-...

[2] https://en.wikipedia.org/wiki/Aircraft_Reactor_Experiment

> https://whatisnuclear.com/img/nuclear_rocket.jpg

That looks like some sort of bio-mechanical abomination descended from Cthulhu.

Funny you should mention it. A similar hypothetical weapons system is deployed against Cthulhu in the excellent short story A Colder War by Charles Stross.

See http://www.infinityplus.co.uk/stories/colderwar.htm

You can visit the two test reactors/engines, sitting in a parking lot in Arco, ID. Here's some pics I took about a decade ago:

https://www.flickr.com/photos/lhoriman/3763287997/in/album-7...

https://www.flickr.com/photos/lhoriman/3763298693/in/album-7...

The lead-lined railroad locomotive was pretty cool too:

https://www.flickr.com/photos/lhoriman/3763363831/in/album-7...

(there's a few more if you click through to the album)

Indeed! Those HTREs in the lot were prototypes for this particular engine. The parking lot is for the Experimental Breeder Reactor I, the first reactor in the world to make electricity. It was cooled with sodium-potassium eutectic liquid metal. Really amazing museum now.

Don't forget Project Pluto - a nuclear powered ramjet on a cruise missile would have circled close to ground level irradiating huge areas after flattening them with supersonic shock waves.

There's some revisionism in the Wikipedia article, but you can still make out the outline intent.

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

Shades of Boris Artzybasheff.

https://i0.wp.com/farm4.static.flickr.com/3314/4554374811_dc...

I presume you have Weinberg's book?

Yeah it's my favorite.

>https://en.wikipedia.org/wiki/Nuclear-powered_aircraft

Tupolev Tu-119 ... had two conventional turboprop engines and two direct-cycle nuclear jet engines, and got around the shielding weight issue by simply not including it.

This made my day.

Ruined some people's day though - next paragraph: "We had all been irradiated, but we ignored it. Of the two crews, only three men survived- a young navigator, a military navigator and me. The first to go, a young technician, took only three years to die".

Funny how someone who is not a radiologist can blurt out nonsense and nobody questions it. If you follow the link to the main article:

"...radiation shielding, which was one of the main concerns for the engineers. Liquid sodium, beryllium oxide, cadmium, paraffin wax and steel plates were used for protection."

Clearly, the Soviets weren't suicidal. They were obviously looking for lightweight ways to shield the neutron radiation, which is very damaging to both humans and electronics. The gamma radiation would still reach the crew, but attenuated by the distance. Gamma isn't too bad, because little of it is absorbed.

> a young technician, took only three years to die

Well, that wasn't radiation poisoning (it kills within days or not at all), and it wasn't cancer (that takes longer to develop). What was it? Ethanol poisoning?

The DOE land on which ORNL sits has a massive stand that they used for testing of this idea. They'd suspend a reactor to test shielding effectiveness. You can see it from a few spots on I-40/I-75 and on Highway 95 going by the lab's west entrance.

It was called the Tower Shielding Facility. Pretty glorious. Small writeup here: https://www.ornl.gov/blog/ornl-reporter/lofty-ambitions

I wonder what the feasability would be like for an unmanned version nowadays - no need for shielding during flight (although you're basically flying a dirty bomb around).

The Russians claim to have made such a system. They also claim nuclear powered torpedoes. It is not 100% clear how far they really are. However, there was detectable accidents, so they are at least really trying. It ain't all bluff.

Years ago, I read decent alternate-history piece of fiction, set in a world where nuclear-powered bombers were put in service by the United States Air Force:Steambird

https://www.fantasticfiction.com/s/hilbert-schenck/steam-bir...

If I were Airbus or Boeing, I'd have a group working on something like this as a solution to CO2 emissions from commercial aircraft.

Also, how do you keep the crew alive for months without allowing for all the weight of those supplies?

Theoretically you could replace the crew/restock in midair

Wow, that's dark. No need for shielding if you can just replace the crew as they die from radiation poisoning every few days?

He means rotate the crew.

I think he means swap people out (because working for 48hr+ straight tends to lower job performance) and restock supplies like food/water

Just because you can stay airborne indefinitely doesn't mean that you're not going to ever land.

I'm wondering how you'd do laundry.

no need to wear clothing if you are warm and dry

By not having a crew?

It's written about extensively in this chapter: "Human Factors of Nuclear-Powered Aircraft." [1]

[1] https://babel.hathitrust.org/cgi/pt?id=mdp.39015001555146&vi...

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