GalFisk

GalFisk t1_j6hd9yt wrote

Ever used a cooling spray, or sprayed yourself with liquid butane while filling a lighter? The evaporating liquid carries away a lot of heat, so it feels cold.

Refrigerators do the same thing essentially, but in a closed tube, and then they recompress the evaporated gas to squeeze the heat out (this happens in the warm tubes you'll find on the outside rear of the fridge), so that it can go around and work as a cooling spray again.

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GalFisk t1_j0yetpn wrote

Radioactive cesium chloride can sometimes glow blue in the dark. https://en.wikipedia.org/wiki/Goi%C3%A2nia_accident#Opening_the_capsule

Plutonium RTG sources don't glow, but they have attracted fatal attention by being hot: https://en.wikipedia.org/wiki/Lia_radiological_accident#The_accident

If alien biology is present, I think bioaccumulation of radioactive substances, as suggested in another post, is an interesting direction to take.

People frequently survive radiological accidents. If you want to make it realistic, read up on the above accidents and others, decide source type and strength, exposure time and technology level of medical treatment, and wrap your drama around that.

Have you read "The Martian" by Andy Weir? >!He wanted to include a radiological accident with an RTG, but couldn't find a way to make it realistic without killing the protagonist.!< He does his best at making the science realistic, and I think his stories, and especially the world-building, are all the better for it.

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GalFisk t1_iyc1079 wrote

They all use frequency hopping, in addition to encryption and such. This means that they automatically retune to a new frequency many times per second. A simple tuner can only stay on one frequency. Even if you have one that can hop, it needs to know the pattern to follow in order to track the signal, and the agreement on a pattern between the sender and receiver is kept secret by encryption. The common way to intercept cellphone communications is to have your own device that acts like a cellphone tower, trick the phone into connecting to that, and read off the data after it has been received, while transparently forwarding it to the real cellphone network.

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GalFisk t1_iy31wog wrote

Every time an exhaust valve opens in a cylinder, the residual pressure of the exhaust gases is suddenly expelled thorugh the exhaust, causing a loud "pop". In most engines, the pops are regularly spaced, creating a regular "tone". In the V arrangement, two pops happen close after one another, and then there's a longer delay before the next two. This causes the characteristic noise.

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