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UN Bans Mercury Satellite Propellants Under New Minamata Treaty Provisions

122 points by aaronbrethorst 5y ago

phendrenad2 5y ago
As an alternative, what's the heaviest element they could use that is safe for the environment?
- adrian_b 5y ago
  Xenon is easy to use for this purpose, but it is expensive and it requires much larger and much heavier containers for the same mass, because it must be compressed and liquefied. Iodine has almost the same atomic mass as xenon, but it is much easier to store than xenon (it is solid, but much less dense than mercury), even if it is corrosive. The elements with a closer atomic mass to mercury are difficult to vaporize. It would not be impossible to use any of them in an ionic thruster, but it would be extremely difficult to obtain a high enough ionic flux and a long enough lifetime of the engine.
  - somebodynew 5y ago
    Bismuth might be in a decent spot for optimizing price/density/boiling point/safety if the thruster can be made of molybdenum. I'm not sure if there are more delicate components required to withstand the boiling point of the mass source that can't be made of structural metal.
  - _joel 5y ago
    Krypton is cheaper.
    - adrian_b 5y ago
      It is also much lighter. The question was which are the heaviest usable elements, and those are iodine and xenon. Iodine is also cheap. However the fact that it is not an inert gas like krypton and xenon creates some difficulties, even if those are balanced by its easier storage.
deleted 5y ago
[deleted]
Gravityloss 5y ago
There are a lot of potential solutions for in-space electric propulsion. Just that iterating technology in space is slow and expensive. That's a reason why they're potential solutions - they haven't been tried out! For example you could have water thrusters. Or evaporated plastics.
henearkr 5y ago
Could we use iron ions, and thus maybe seed the oceans when it falls back on Earth?
- simonh 5y ago
  It's easiest to use a gas or vapour. Mercury is easy to evaporate and the most common alternatives are heavy gases like Xenon or Krypton.
chipsa 5y ago
How much mercury would actually filter down? Ion engines are extremely high isp (1000-8000 seconds). Literature suggests that 3000s was demonstrated back in the 70s. This implies an exhaust velocity of ~30km/s, while Earth escape velocity is 11km/s (depending on altitude) It appears that PEER assumes that the ACE engine would be used against the direction of travel (retrograde), but almost all station keeping burns are prograde, in order to keep the satellite up against ionospheric or exospheric drag. And they assume a lower isp than has previously been demonstrated with mercury fueled engines.
hirundo 5y ago
I guess plutonium is right out then. I hope they make exceptions for sufficiently safe launch vehicles that put their payloads beyond Earth orbit.
- eesmith 5y ago
  The article mentions an exception to allow mercury use: “The Minamata Convention on Mercury seeks to eliminate all mercury uses where technically-achievable non-mercury alternatives are available,” By comparison, plutonium is not particularly toxic. I see no reason a similar treaty wouldn't have a similar exception.
  - deleted 5y ago
    [deleted]
- db48x 5y ago
  Plutonium is not a propellant.
  - hirundo 5y ago
    See e.g. Project Orion: https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...
    - db48x 5y ago
      It’s still not a propellant, and use of nuclear explosives in the atmosphere or near earth orbit is already covered by other treaties.
      - skykooler 5y ago
        It's technically a propellant - the reaction mass is the spent fragments of each explosion.
      - abracadaniel 5y ago
kyleblarson 5y ago
Does the UN actually have the power to ban anything?
- arlort 5y ago
  When someone says "the UN did X" what really happened 90% of the time is that countries meeting at a convention which has been organized by the UN (and I do just mean organized, the decision to have the convention in the first place was again 90% taken by countries at another event and so on) decided that they'll do X The UN doesn't really have any power to do anything, it's just a way to organize countries working on a series of topics in such a way that the staff and infrastructure needed to facilitate meetings are already in place instead of every new thing requiring a whole set up phase
- bawolff 5y ago
  They have quite a bit of soft power. People say that the UN is ineffectual, but they have managed to nag countries into better behaviour with a shocking amount of success. Whether that's "power" or not is debatable, but the end result is stuff getting done.
- AnimalMuppet 5y ago
  Well, those who sign the treaty are choosing not to use it themselves. Those who don't sign the treaty... no the UN doesn't have any such power. They can kind of catalyze global pressure, though.
Aachen 5y ago
Didn't know this was a thing or why it's bad. The article does a pretty shoddy job at giving that information but one can puzzle it together: It seems to be specifically about emissions in low Earth orbit from maneuvering thrusters, such as in satellite constellations, because that will fall back into the upper atmosphere. Is there a climate change issue then, ozone layer, anything? No it just seems to be falling down that's the issue, this is mentioned further down: > The environmental and human health implications of such releases have not been evaluated. Using an atmospheric chemical transport model, we simulate global deposition of mercury released from satellite propulsion systems. We estimate that 75% of the mercury falling back to Earth will be deposited in the world’s oceans, with potentially negative implications for commercial fish and other marine life. So have or haven't environmental implications been evaluated? It seems to me this very paragraph does just that. And wasn't it not about propulsion in general but about OMS instead? Well, anyway, that's what mercury emissions are about.
- KarlKemp 5y ago
  Mercury is just straight up nasty stuff. It causes cancer. It makes you stupid. It is one leading hypothesis as the reason violent crime happened at 2x or 3x the rate just 50 years ago. The collapse of the Roman Empire probably wasn’t caused by Mercury poisoning. But just being considered a legitimate contender for that role is impressively scary.
  - rsynnott 5y ago
    The main concern for Romans was lead, not mercury. Not due to pipes, as commonly believed, so much as due to the fact that they _used lead salts to flavor food_. This also, of course, didn't cause the fall of the empire.
    - JumpCrisscross 5y ago
      > so much as due to the fact that they _used lead salts to flavor food_ I believe it was also common to sweeten wine by leaving it in lead carafes.
  - 5y ago
jmpman 5y ago
How much Mercury does satellite propellant contribute to global airborne mercury, compared to coal fired power plant emissions? My first thought is that this is about 7 orders of magnitude less, and thus a ridiculous thing for these technocrats to focus on… but I’m happy to be educated. Or is there some other concern about mercury in satellite propellant?
- haukem 5y ago
  Coal plants are emitting a lot of unhealthy stuff. The coal plant Jänschwalde in Germany emitted 672kg mercury, 1780kg lead and 208 kg arsenic in 2017 according to the European Pollutant Release and Transfer Register. https://de.wikipedia.org/wiki/Kraftwerk_J%C3%A4nschwalde#Emission https://de.wikipedia.org/wiki/Kraftwerk_J%C3%A4nschwalde#Emi... This is the worst coal plant in Germany, but the others are not so much better.
- rsynnott 5y ago
  The US emits 52 tonnes/year into the air, apparently. The article claims _hundreds_ of tonnes for one constellation. Which does seem concerning if correct.
  - daniel-cussen 5y ago
    Sounds pretty low actually, I'm sure it's much much more. 52 tons is more in line with the amount of gold in that coal. And hundreds of tons for one constellation? How do they get it up there in the first place?
    - rsynnott 5y ago
      These are big constellations of LEO satellites. Starlink, for instance, has 1500 satellites today, with a goal of 30,000. If we assume 10kg of propellant per satellite, then that's 300 tonnes for the finished constellation (Starlink satellites use a noble gas, I believe, but anyone using mercury for a similar scheme would hit that). The whole _world_'s atmospheric emissions only seem to be about 250 tonnes per year.
jpm_sd 5y ago
I guess Apollo Fusion is lucky they got acquired by Astra before this went through? https://hakaimagazine.com/news/what-goes-up-must-come-down/ https://hakaimagazine.com/news/what-goes-up-must-come-down/

phendrenad2 5y ago

As an alternative, what's the heaviest element they could use that is safe for the environment?

adrian_b 5y ago
Xenon is easy to use for this purpose, but it is expensive and it requires much larger and much heavier containers for the same mass, because it must be compressed and liquefied. Iodine has almost the same atomic mass as xenon, but it is much easier to store than xenon (it is solid, but much less dense than mercury), even if it is corrosive. The elements with a closer atomic mass to mercury are difficult to vaporize. It would not be impossible to use any of them in an ionic thruster, but it would be extremely difficult to obtain a high enough ionic flux and a long enough lifetime of the engine.
- somebodynew 5y ago
  Bismuth might be in a decent spot for optimizing price/density/boiling point/safety if the thruster can be made of molybdenum. I'm not sure if there are more delicate components required to withstand the boiling point of the mass source that can't be made of structural metal.
- _joel 5y ago
  Krypton is cheaper.
  - adrian_b 5y ago
    It is also much lighter. The question was which are the heaviest usable elements, and those are iodine and xenon. Iodine is also cheap. However the fact that it is not an inert gas like krypton and xenon creates some difficulties, even if those are balanced by its easier storage.

deleted 5y ago

[deleted]

Gravityloss 5y ago

There are a lot of potential solutions for in-space electric propulsion. Just that iterating technology in space is slow and expensive. That's a reason why they're potential solutions - they haven't been tried out! For example you could have water thrusters. Or evaporated plastics.

henearkr 5y ago

Could we use iron ions, and thus maybe seed the oceans when it falls back on Earth?

simonh 5y ago
It's easiest to use a gas or vapour. Mercury is easy to evaporate and the most common alternatives are heavy gases like Xenon or Krypton.

chipsa 5y ago

How much mercury would actually filter down? Ion engines are extremely high isp (1000-8000 seconds). Literature suggests that 3000s was demonstrated back in the 70s. This implies an exhaust velocity of ~30km/s, while Earth escape velocity is 11km/s (depending on altitude) It appears that PEER assumes that the ACE engine would be used against the direction of travel (retrograde), but almost all station keeping burns are prograde, in order to keep the satellite up against ionospheric or exospheric drag. And they assume a lower isp than has previously been demonstrated with mercury fueled engines.

hirundo 5y ago

I guess plutonium is right out then. I hope they make exceptions for sufficiently safe launch vehicles that put their payloads beyond Earth orbit.

eesmith 5y ago
The article mentions an exception to allow mercury use: “The Minamata Convention on Mercury seeks to eliminate all mercury uses where technically-achievable non-mercury alternatives are available,” By comparison, plutonium is not particularly toxic. I see no reason a similar treaty wouldn't have a similar exception.
- deleted 5y ago
  [deleted]
db48x 5y ago
Plutonium is not a propellant.
- hirundo 5y ago
  See e.g. Project Orion: https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...
  - db48x 5y ago
    It’s still not a propellant, and use of nuclear explosives in the atmosphere or near earth orbit is already covered by other treaties.
    - skykooler 5y ago
      It's technically a propellant - the reaction mass is the spent fragments of each explosion.
    - abracadaniel 5y ago

kyleblarson 5y ago

Does the UN actually have the power to ban anything?

arlort 5y ago
When someone says "the UN did X" what really happened 90% of the time is that countries meeting at a convention which has been organized by the UN (and I do just mean organized, the decision to have the convention in the first place was again 90% taken by countries at another event and so on) decided that they'll do X The UN doesn't really have any power to do anything, it's just a way to organize countries working on a series of topics in such a way that the staff and infrastructure needed to facilitate meetings are already in place instead of every new thing requiring a whole set up phase
bawolff 5y ago
They have quite a bit of soft power. People say that the UN is ineffectual, but they have managed to nag countries into better behaviour with a shocking amount of success. Whether that's "power" or not is debatable, but the end result is stuff getting done.
AnimalMuppet 5y ago
Well, those who sign the treaty are choosing not to use it themselves. Those who don't sign the treaty... no the UN doesn't have any such power. They can kind of catalyze global pressure, though.

Aachen 5y ago

Didn't know this was a thing or why it's bad. The article does a pretty shoddy job at giving that information but one can puzzle it together: It seems to be specifically about emissions in low Earth orbit from maneuvering thrusters, such as in satellite constellations, because that will fall back into the upper atmosphere. Is there a climate change issue then, ozone layer, anything? No it just seems to be falling down that's the issue, this is mentioned further down: > The environmental and human health implications of such releases have not been evaluated. Using an atmospheric chemical transport model, we simulate global deposition of mercury released from satellite propulsion systems. We estimate that 75% of the mercury falling back to Earth will be deposited in the world’s oceans, with potentially negative implications for commercial fish and other marine life. So have or haven't environmental implications been evaluated? It seems to me this very paragraph does just that. And wasn't it not about propulsion in general but about OMS instead? Well, anyway, that's what mercury emissions are about.

KarlKemp 5y ago
Mercury is just straight up nasty stuff. It causes cancer. It makes you stupid. It is one leading hypothesis as the reason violent crime happened at 2x or 3x the rate just 50 years ago. The collapse of the Roman Empire probably wasn’t caused by Mercury poisoning. But just being considered a legitimate contender for that role is impressively scary.
- rsynnott 5y ago
  The main concern for Romans was lead, not mercury. Not due to pipes, as commonly believed, so much as due to the fact that they _used lead salts to flavor food_. This also, of course, didn't cause the fall of the empire.
  - JumpCrisscross 5y ago
    > so much as due to the fact that they _used lead salts to flavor food_ I believe it was also common to sweeten wine by leaving it in lead carafes.
- 5y ago

jmpman 5y ago

How much Mercury does satellite propellant contribute to global airborne mercury, compared to coal fired power plant emissions? My first thought is that this is about 7 orders of magnitude less, and thus a ridiculous thing for these technocrats to focus on… but I’m happy to be educated. Or is there some other concern about mercury in satellite propellant?

haukem 5y ago
Coal plants are emitting a lot of unhealthy stuff. The coal plant Jänschwalde in Germany emitted 672kg mercury, 1780kg lead and 208 kg arsenic in 2017 according to the European Pollutant Release and Transfer Register. https://de.wikipedia.org/wiki/Kraftwerk_J%C3%A4nschwalde#Emission https://de.wikipedia.org/wiki/Kraftwerk_J%C3%A4nschwalde#Emi... This is the worst coal plant in Germany, but the others are not so much better.
rsynnott 5y ago
The US emits 52 tonnes/year into the air, apparently. The article claims _hundreds_ of tonnes for one constellation. Which does seem concerning if correct.
- daniel-cussen 5y ago
  Sounds pretty low actually, I'm sure it's much much more. 52 tons is more in line with the amount of gold in that coal. And hundreds of tons for one constellation? How do they get it up there in the first place?
  - rsynnott 5y ago
    These are big constellations of LEO satellites. Starlink, for instance, has 1500 satellites today, with a goal of 30,000. If we assume 10kg of propellant per satellite, then that's 300 tonnes for the finished constellation (Starlink satellites use a noble gas, I believe, but anyone using mercury for a similar scheme would hit that). The whole _world_'s atmospheric emissions only seem to be about 250 tonnes per year.

jpm_sd 5y ago

I guess Apollo Fusion is lucky they got acquired by Astra before this went through? https://hakaimagazine.com/news/what-goes-up-must-come-down/ https://hakaimagazine.com/news/what-goes-up-must-come-down/