[windsurfer]

With the satellite megaconstellations being launched it seems important to ban it before it becomes common. Mercury-based fuels are cheaper than alternatives.

Coal as being burned for electricity has an industry standard of scrubbing 90% of mercury emissions, but is moving towards 99% using newer technologies.

[dotancohen]

So, it will be four orders of magnitude more for coal than for mega constellations. Seven minus one order of magnitude for better scrubbing and two orders of magnitude for the size of the constellations. Still a ridiculous thing to focus on.

If they would focus on reducing atmospheric mercury and direct their efforts against all offenders, I would completely agree. But singling out satellites or deliberately ignoring coal hints that they have a different agenda, and "atmospheric mercury" is their parallel construction.

[simonh]

Efforts are being directed against all offenders, that's why coal is moving to 99% scrubbing instead of 90% as mentioned up thread. As a species and civilization I think we can manage 'focusing' on more than one thing at a time.

Apart from anything else we should at least be consistent, right? If Mercury can reasonably be avoided in any form of polluting usage, it should be.

[dotancohen]

  > coal is moving to 99% scrubbing instead of 90%

Yes, but that resolves only one order of magnitude difference between the coal plant and the satellite constellations. Another two orders of magnitude are accounted for in the increasing size of the megaconstellations.

So even after those issues are addressed, earth-based coal is four orders of magnitude more problematic. Sure, focus on multiple targets. But don't pick a target 1000 times less significant to "diversify focus".

[simonh]

I think even if 1,000 people are getting cancer a year from a particular cause, that doesn't mean we can ignore this other cause that's only killing 1 person a year.

Should we also exclude small coal plants that only emit <1% of global emissions? What other cost effectively preventable emissions of mercury should we allow? Where do we draw the line? We should be consistent, especially since the costs of compliance don't seem to be all that great.

[dotancohen]

I hate to belittle a point, but this group is addressing the cause that is metaphorically killing 1 person per year while ignoring the cause that is killing 1,000 people per year.

In fact, I would go so far as to say that this cause is deflecting energy from any anti-coal movement by offering an new, shiny, space-age target for activists to concentrate on.

[simonh]

I have already addressed that point in this thread. The emissions from coal plants are being addressed with a 10x reduction already in the works. It is not being ignored, at all.

On the contrary, every effort to minimise mercury emissions and highlight their danger is worthwhile and raises awareness. The only reason we are talking about coal emissions now is because of this effort. If anything, consciously choosing not to address this specific issue and applying mercury emissions controls inconsistently would weaken the case for cracking down on other sources of emissions. It would smack of exceptionalism and preferential treatment. If you can carve out an exception for this source, why not others? Why do high tech rich world projects like a satellite fleet get a pass, but not a specific coal plant in a third world country with the same emissions?

[HPsquared]

It's a smaller problem, but also easier to solve. The costs of a few suppliers changing their satellite propellants are orders of magnitude less than ending global coal usage (though both would be nice, of course).

[cinntaile]

It is simply easier to ban mercury propellants than it is to ban coal plant mercury emissions. A lot more people are dependent on the coal plants so the time and energy it takes to make changes there is just way bigger. Of course work is being done there as well, it just takes way longer.

[simulate-me]

What is your argument exactly? That as long as coal power plants emit airborne mercury, then anyone else can emit mercury as well as long as they emit less? This is just a form of whataboutism. We don't have ready, scalable alternatives to coal power at the moment, or don't have the will / money to bring alternatives into service. We do have alternatives to mercury-based space fuels.

[danuker]

> a different agenda

I'll bite: fossil fuel is running the show?

[dotancohen]

That would seem an obvious agenda, possibly. If you've ever seen the slander against electric vehicles or Tesla, you'll believe that the fossil fuel companies are promoting an agenda.

[_joel]

The megaconstellations use reaction mass wheels and hall effect thrusters (Krypton in Starlink). I'm not sure any use mercury as a fuel.

[onion2k]

You must have missed the "before it becomes common" part of the post you've replied to. No one is suggesting it's being used a lot. The ban is to stop it before it does.

[_joel]

But it's not even in use now, when, if it could be used as a cheaper fuel, it would.

Becoming common still needs for there to be some usage, even before it becomes common.

[simonh]

Apollo Constellation Engine designed their propulsion systems for mega constellations to use mercury, which is what got PEER involved in this. Popular Mechanics also reported on their plans. Even if Apollo changed their minds since, that's a pretty significant 'near miss'.

https://ecfsapi.fcc.gov/file/111998371507/11_19_18_FCC_compl...

https://www.popularmechanics.com/space/rockets/a25242578/apo...