There's been various desktop-grade plans regarding use of nuclear rockets, both in the atmosphere and not. Never underestimate what engineers can come up with.

I think what they were trying to argue is that the mercury emitted would be no worse than the mercury already emitted as a byproduct of power plants.

Most rocket operators/manufacturers run on razor thin margins or at a loss, sustained by state subsidies or wishful venture capitalists.

It's an ion thruster, not a rocket per say. You cannot use it in lower atmosphere at all (well you can but it doesn't do much), unfortunately some of the propellant would still find its way to the atmosphere.

The market of small thrusters for steering satellites is much larger than building actual rockets that take those satellites to orbit.

Launching rockets is a competitive market? TIL, I thought there were only a handful of companies operating with very generous margins

Oh, it is definitely a competitive market at the moment, there are dozens of space startups with new rocket ideas trying to replace the old rocket companies. And many of these companies are seeing some great success, there's SpaceX and rocketlab of course, but firefly aerospace is also doing great, Stoke aerospace has the most innovative design I've seen in a while and may have a viable design for a fully reusable rocket. But there are many many more companies building rockets right now.

I've never heard of mercury propellent though, that sounds like a supremely terrible idea. And they would certainly need more than that to be competitive. Today, reusability and efficient construction techniques are the key to competitiveness, not novel propellants.

Actually susprised that it's even viable to use a byproduct of burning something else as a fuel

Isn't charcoal that?

But we don't need regulation /s

Mercury would be a denser propellant than xenon/other Nobel gasses used for ion thrusters in orbit. There’s been a ton of other insane fuel types proposed over the years which thankfully haven’t been used (although a lot of rockets have and still use toxic hypergolic fuels like hydrazine)

Good vid going over some of these fuels: https://youtu.be/_wLk2j7_KB0