Hacker News Reader

Comment by adzm | Hacker News Reader

That article mentions them dangling a wrist watch over the space ball to see if it was radioactive. How would this work?

View on HN

It wouldn't.

edit: It's obvious the quoted person had no idea what they were doing -- even a few seconds at arms' length from a fresh nuclear reactor core would be fatal. And quite a few satellites in that era were nuclear-powered.

It's not as if accurate knowledge of radiation was readily available, in the 1970's.

They didn't shoot nuclear reactor cores into space. RTGs are still dangerous but people do stand next to them.

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

Some of the Russian satellites had full-on liquid cooled nuclear reactors, not RTGs.

https://en.m.wikipedia.org/wiki/TOPAZ_nuclear_reactor

The flight profile did indeed have the reactor core being ejected into a graveyard orbit before deorbiting the satellite:

https://en.m.wikipedia.org/wiki/Kosmos_954

The US ran a couple of experiments but otherwise didn't officially use them:

https://en.m.wikipedia.org/wiki/SNAP-10A

Believe it or not, lots of nuclear fission satellites in the 1960's-70's.

https://en.wikipedia.org/wiki/Nuclear_power_in_space#Fission...

You're right, I didn't realize they fired quite that many (31?!) BES-5s into space and those are really the only non-experimental ones. Still, the chances of one of those falling out of orbit as a functioning reactor are about nil.

The posterior probability, given that you've already found a very rare piece of space debris, would have been high.

https://xkcd.com/795/

(By the way, there's an documented instance [0] mentioned in the sibling comments. The hazard is much worse than you'd think: the space reactor didn't simply fall in one piece, but left a trail of fragments 600 km long, some of which were lethally radioactive. It's pretty lucky this one happened in an uninhabited wasteland).

[0] https://en.wikipedia.org/wiki/Kosmos_954

Yes but those dangers are the dangers of radioactive material - it's naturally 'hot', much of it also chemically toxic, etc. It's not core-at-criticality-that-murders-you-as-you-stand-next-to-it type of dangerous. I think that's still an essentially hypothetical danger of nuclear space junk.

As a general rule, it's not reactors functioning inside design parameters that are cause for concern, but rather failed reactors that have spew their guts and stopped working. Those are the reactors that will fuck you up.

If it's a digital / quartz watch, it might stop working if the electronics got too much radiation.

They probably thought the dial paint would fluoresce brightly when exposed to radiation, like some florescent substances glow when exposed to UV. Would it work for alpha or gamma radiation? ¯\_(ツ)_/¯

Whatever the case, sure, it's certainly not a reliable safety test. But it was wise to keep this thing away from people. RTG's do have highly dangerous materials like polonium or strontium and there have been accidents.

Perhaps tritium in the watch hands.

Tritium is itself radioactive and used in watches to make a luminescent material glow. I think zinc sulphide was common and it would probably glow if lit up enough. Not sure you want to be near something that makes your watch dial markings glow visibly more than the radium or tritium that's in the paint, though.

The tritium interacts with a phosphor through beta decay, so presumably if you hung a watch near it the phosphor would glow brighter with higher concentration of beta decay. Basically a sort of visual Geiger counter.

Zinc sulphide, from brief googling, seems like it would glow in anything so if this was a thing, it probably makes most sense for gamma radiation since the 'detector' isn't being massively lit up by that internally already.

Sure, but run the inverse-square law on the difference between a ~100 micron paint layer and a source that's ~1 meter away.

That’s what I was thinking when I read it. I have no idea if tritium emits more radioluminescence near a source though.

Reply on news.ycombinator.com