Good to know, thanks!
Robert E. Howard was still using lights powered by “radium” in stories like Almuric into the 1930s. “Radium” was just a magical material that continued to give off energy for a long, long time – about the only thing fictional radium had inn common with the Real Thing.
Ages ago I read Iron Coffins, the memoir of a U-boat skipper. He mentioned when they surfaced after being underwater a while they’d start the diesels with the engine room induction valves closed but the conning tower hatch open. The air in the boat would exchanged in moments.
Yup, the only problem is that sometimes the wind shifts and you end up sucking in diesel exhaust. 
This always goes well with rolling on the surface.
(Note that nuclear-powered subs also have a diesel engine in the form of an emergency diesel generator.)
On SSNs, the diesel engine is primarily for emergencies, but is still run regularly for proficiency/training. Whenever it was running the whole boat would smell faintly of diesel smoke, and I never got over the slight feeling of nausea it would induce.
I would have had trouble serving on an old diesel boat.
Agree with all of this. And whenever we were on an extended deployment and went into a port after an extended period of being submerged, the A-gangers would inevitably decide that was the time to fire up the diesel since it hadn’t been run in a while.
I remember driving in on the surface to Tromsø, Norway doing 15 degree rolls with the boat full of diesel fumes. I rarely got motion sick when I was younger, but that was one time I felt nauseous to point of almost being incapacitated.
Back to the thread topic (more or less) 
, on the submarines I was on, the periscopes were optical devices using mirrors and lenses. The newer ones are completely electronic “photonics masts,” so they can put the image up on a large screen very much like in Star Trek.
This isn’t surprising. Periscopes had been used as far back as the mid-19th century on subs (true!), but they were incredibly impractical, which is probably why Jules Verne didn’t put one on the Nautilus (despite his using the latest developments in underwater tech in his book).
Pereiscopes require sets of complex relay lenses to convey the image down to eyes inside the sub (otherwise you’re looking through a long tube, and you’ll only see a small dot of vision at the center of the dark walls of the periscope tube. Try looking down a pipe sometime). It also needs to be structurally sound enough to resist bending when the sub is underway. And the optics inside that tube will tend to mist over if any moisture gets inside (so you better have dessicants packed in there).
Altogether a long working periscope is a masterpiece of optical and mechanical engineering. It’s much easier, though, to simply mount a camera on a stick, which is in essence what a Photonics Mast is.
You would also have severe trouble working on any underground mine, but especially a trackless mine. The air was noticeably blue.
Are you saying that miners cuss as much as sailors? 
Sometimes I am sorry for a hijack I caused. Not this time, this has been fascinating, and even informative.
A rifle needing air to fire.
Ironically, that was Whedon trying to be scientifically accurate. To be fair, you can also see that scene as the characters thinking the rifle needed an atmosphere. The characters who know guns aren’t very scientifically literate, and the characters who are scientifically literate don’t know anything about guns.
To be even more scrupulously fair, while many of the firearms seem to be common 20th century firearms (which doesn’t really make sense in-universe, but that’s another thread), some are clearly fictional weapons, and we see at least one laser weapon, so we don’t really know for sure what “Vera’s” firing mechanism is.
It is very easy to fanwank a reason why a high-tech gun might need an atmosphere. For example, it could have sensors that detect pressure and humidity, in order to correct the aim. In a vcuum, which it was never designed for, the sensors go screwy amd the gun shuts down and won’t fire.
Also, where did this multiple star system idea come from? Firefly had a perfectly consistend and scientifically accurate ‘verse’, with a star system consisting of a hot blue star and lots of planets. Why complicate things? A blue star is perfect: They have a huge habitable zone, and they don’t last for billions of years so there would be no indigenous complex life. Perfect for terraforming. You could have lots of planets and dozens of habitable moons after terraforming.
But Firefly did screw up the science on numerous occasions. For example, in ‘Out of Gas’, when the engines go off line Serenity is described as ‘not moving’ and being ‘dead in the water’.
The scale of space was also vastly underestimted. Ships are crossing each other’s paths within visual distance in deep space all the time. I understand you want this for storytelljng purposes, but in real life it would not happen. Every transfer orbit between moving bodies is different. There are no ‘space lanes’ crowded with ships.
Well again, a lot of that is shorthand. I remember the big issue during that episode was that specifically plotted a course that would take a long time to get anywhere, and then the engine failed killing the life support. So they were essentially dead in the water because they had no way to get anywhere safe before they all died.
There was a bad guy with a LASER. I felt that (I hate making excuses for Sci Fi other than Trek, but I digress.) either beam weapons were outlawed for the average guy, like taxes on automatic weapons today. Perhaps that was all the average guy could afford. Of course, it fell in line with the “Cowboys in Space” theme. Weedon (sp?) said that he thought a gun needed air to fire.
But the laser was an unreliable rich-person’s toy.
They were quite specific.
The imagery of Serenity from outside was also evocative of a ship floating dead in the water, listing slightly.
And since we are on that episode, The idea that they would asphyxiate so quickly after life support fails is ridiculous. Even given the fire that used up most of the oxygen, the sheer volume of air around them, and the fact that they aren’t showing any signs of hypoxia or carbon monoxide poisoning means that they had days or weeks of air, not hours.
The same goes for freezing to death, Space is a gorram big insulator, and generally the problem with anything that generates internal heat is getting rid of it. They still had electricity and internal power, so they were generating heat. And the ship would be well insulated since it flies in the inner system as well where the sun is baking it.
I’m pretty sure they mentioned that the reason he had a laser was because he was a rich douchebag with a weapons fetish, and bought weapons other people couldn’t afford. Inara also had a laser pistol as her personal weapon. But then, she was a rich person from the inner planets, whereas the people with plain old guns tend to be poor people from the outer worlds.
Also, the tech to make bullets and powder is low and inexpensive. Perhaps maintaining laser pistols is just something the outer worlds can’t manage. It’s also why they ride horses instead of the rich guy’s ground effects vehicle: Vehicles need maintenance and replacement parts. Horses just need food.and make their own replacements.
It’s the same thing. If in a sci-fi world where you travel via Direct Burn ala The Expanse not accelerating is functionally the same as not moving. It’s like if your sail fell off your boat. You’re still technically moving, but no one would quibble with “dead in the water.”