6 ms·

How much do rockets pollute?

82 points by dpifke 7y ago

ecoled_ame 7y ago
something that tends to annoy me about hydrogen fuels - people emphasize that the combustion product is water. okay .. so that step is clean. but how was the hydrogen in the fuel cell produced in the first place? i guess it’s an energy consuming process that produces a decent level of pollution, whether it’s by electrolysis, heating of a chemical in the presence of a catalyst, etc.
- namibj 7y ago
  Fuel hydrogen is typically produced via steam reforming [0] and subsequent distillation/liquification. [0]: https://en.wikipedia.org/wiki/Steam_reforming https://en.wikipedia.org/wiki/Steam_reforming
  - vbezhenar 7y ago
    CH4 + H2O ⇌ CO + 3 H2 CO + H2O ⇌ CO2 + H2 For every tonne of hydrogen produced this way, 9 tonnes of CO2 is also produced.
    - seventh-chord 7y ago
      Isnt the ratio closer to ~6 tons of CO2 per ton of H2? You get CO2 + 4 H2, which weigh 44 and 4*2 respectively. Also, isnt this a non-issue, because (at least in theory) the reaction is contained in your converter plant, where you can collect the CO2?
      - vbezhenar 7y ago
        That's quote from wikipedia. I think you're right with your calculations, so I don't really know where this number came from. What're you going to do with that collected CO2 other than releasing it to the atmosphere?
        namibj 7y ago
        Separating from other gasses, followed by sequestering.
        vbezhenar 7y ago
        I guess that it would cost a lot. Technically you can do that with traditional coal plants.
        namibj 7y ago
        Those don't produce fuel. They produce electricity.
- willis936 7y ago
  Electrolysis does not produce pollution. If you are suggesting a mechanism by which it does, I would love to hear it. https://en.wikipedia.org/wiki/Electrolysis_of_water https://en.wikipedia.org/wiki/Electrolysis_of_water https://en.wikipedia.org/wiki/Water_splitting https://en.wikipedia.org/wiki/Water_splitting
  - mac01021 7y ago
    The power generation mechanism you use to get the electric current for electrolysis may or may not be clean.
    - willis936 7y ago
      That’s entirely the point of hydrogen fuel. The process of producing or using hydrogen does not pollute. You have decoupled pollution from energy storage. Hydrocarbons pollute by their very nature. In order to have a carbon neutral hydrocarbon cycle you need an impractical number of CO2 capture facilities.
      - TeMPOraL 7y ago
        And to add to your comment, spelling it out in case it isn't obvious: you can also decouple pollution from energy production using photovoltaics, wind or hydro - and suddenly most of your power chain is clean (what remains dirty is manufacturing the power generator and power storage).
      - TheSpiceIsLife 7y ago
        > The process of producing or using hydrogen does not pollute. There’s no way this can be correct. You can’t use hydrogen to produce the electricity used in hydrogen electrolysis, because that’s not permitted in this universe.[1] Therefore the electricity has to come from some other source, which all generate life-cycle carbon emissions.[2] 1. https://en.wikipedia.org/wiki/Second_law_of_thermodynamics https://en.wikipedia.org/wiki/Second_law_of_thermodynamics 2. https://en.wikipedia.org/wiki/Life-cycle_greenhouse-gas_emissions_of_energy_sources https://en.wikipedia.org/wiki/Life-cycle_greenhouse-gas_emis...
- pfdietz 7y ago
  The water itself is also a problem, in the stratosphere. I think this places an ultimate limit on the number of rocket launches at about 1 million Starship launches per year.
redis_mlc 7y ago
Injecting combustion products into the upper atmosphere is something we really need to study more. I supported the Ozone Hole studies in the mid 80's, and we found CFCs destroyed a protective part of our atmosphere. That recovered over time, but there are some rogue manufacturers using CFCs again, and leaking massive quantities. We know airborne nuclei like soot cause localized precipitation, so that does change weather (it's called cloud seeding.) We really need to know more about the effect of rockets at high altitudes, and airliner jet engines at 30,000'. I have a strong feeling airliners have a significant effect due to the volume of air traffic and how dirty burning jet fuel is. To see how jet engines could have a significant effect, there are around 10,000 airliners worldwide, which are in the air more than 12 hours each per day typically. The break in air travel due do corona virus is an excellent time to compare atmospheric samples before and after the pause.
- MaxBarraclough 7y ago
  > there are some rogue manufacturers using CFCs again, and leaking massive quantities Is it practical to track down the culprits? I presume it would mean prison time.
  - dmos62 7y ago
    Sorry to be the pessimist, but big business and prison time don't fit into the same sentence.
  - baq 7y ago
    If the factory is in China, possible outcomes range from nothing to permanent disappearance. Finding emitters should be easy from satellites.
- t0mas88 7y ago
  The data does not support the common opinion that airplanes are terrible for the environment. Their total contribution to for example CO2 is tiny compared to industry and electricity generation. Somehow the climate activists have decided to make a lot of noise about flying but it's mostly unfounded. They go as far as using very old models of planes in their calculations (e.g. a 737-400 model) and claiming that's the amount of CO2 per passenger of all air travel. While that model is out of use by the airline for at least 15 years already. It was designed in 1985. So beware of the data and tricks like this when you're told flying is so bad for the environment.
bryanlarsen 7y ago
Elon Musk plans on refueling his rockets on Mars using locally produced methane. Using solar power, he'll create methane and liquid oxygen from CO2 and water. If he then burns the methane and liquid oxygen in a rocket engine you get your CO2 and water back. Thus the process is carbon neutral. Before he does it on Mars he'll have to perfect it on Earth first. I hope he does more than that and starts using carbon neutral methane for all his Starship flights on Earth.
- DennisP 7y ago
  Yep, the article talks about that.
DennisP 7y ago
I was pretty surprised to see that Starship flying point-to-point is only about twice as bad on emissions per passenger as a 747.
- mrfusion 7y ago
  Zero drag for 99% of your trip is pretty awesome.
- mr_toad 7y ago
  In theory, methane generation, and thus metholox rockets could be made carbon neutral. https://en.wikipedia.org/wiki/Sabatier_reaction https://en.wikipedia.org/wiki/Sabatier_reaction
orbital-decay 7y ago
The article implies that rockets burn 100% of their fuel, which is an oversimplification for most thrusters. There's also a fair amount of residual fuel and oxidizer in the piping, at least part of which is dumped into the environment. While it isn't that scary for something like kerolox, it's a concern for hypergolics.
- efreak 7y ago
  Actually, this is mentioned in the article, in the "HOW MUCH DO DIFFERENT ROCKETS EMIT?" section, and gets more into it in the linked raptor article[1] > Although all rocket engines do run fuel rich for the right balance of heat management and performance, so there is likely going to be unburnt fuel expelled regardless of the cycle type, but much more when it is an open cycle engine. 1: https://everydayastronaut.com/raptor-engine/ https://everydayastronaut.com/raptor-engine/

82 points by dpifke 7y ago

something that tends to annoy me about hydrogen fuels - people emphasize that the combustion product is water. okay .. so that step is clean. but how was the hydrogen in the fuel cell produced in the first place? i guess it’s an energy consuming process that produces a decent level of pollution, whether it’s by electrolysis, heating of a chemical in the presence of a catalyst, etc.

namibj 7y ago
Fuel hydrogen is typically produced via steam reforming [0] and subsequent distillation/liquification. [0]: https://en.wikipedia.org/wiki/Steam_reforming https://en.wikipedia.org/wiki/Steam_reforming
- vbezhenar 7y ago
  CH4 + H2O ⇌ CO + 3 H2 CO + H2O ⇌ CO2 + H2 For every tonne of hydrogen produced this way, 9 tonnes of CO2 is also produced.
  - seventh-chord 7y ago
    Isnt the ratio closer to ~6 tons of CO2 per ton of H2? You get CO2 + 4 H2, which weigh 44 and 4*2 respectively. Also, isnt this a non-issue, because (at least in theory) the reaction is contained in your converter plant, where you can collect the CO2?
    - vbezhenar 7y ago
      That's quote from wikipedia. I think you're right with your calculations, so I don't really know where this number came from. What're you going to do with that collected CO2 other than releasing it to the atmosphere?
      - namibj 7y ago
        Separating from other gasses, followed by sequestering.
        vbezhenar 7y ago
        I guess that it would cost a lot. Technically you can do that with traditional coal plants.
        namibj 7y ago
        Those don't produce fuel. They produce electricity.
willis936 7y ago
Electrolysis does not produce pollution. If you are suggesting a mechanism by which it does, I would love to hear it. https://en.wikipedia.org/wiki/Electrolysis_of_water https://en.wikipedia.org/wiki/Electrolysis_of_water https://en.wikipedia.org/wiki/Water_splitting https://en.wikipedia.org/wiki/Water_splitting
- mac01021 7y ago
  The power generation mechanism you use to get the electric current for electrolysis may or may not be clean.
  - willis936 7y ago
    That’s entirely the point of hydrogen fuel. The process of producing or using hydrogen does not pollute. You have decoupled pollution from energy storage. Hydrocarbons pollute by their very nature. In order to have a carbon neutral hydrocarbon cycle you need an impractical number of CO2 capture facilities.
    - TeMPOraL 7y ago
      And to add to your comment, spelling it out in case it isn't obvious: you can also decouple pollution from energy production using photovoltaics, wind or hydro - and suddenly most of your power chain is clean (what remains dirty is manufacturing the power generator and power storage).
    - TheSpiceIsLife 7y ago
      > The process of producing or using hydrogen does not pollute. There’s no way this can be correct. You can’t use hydrogen to produce the electricity used in hydrogen electrolysis, because that’s not permitted in this universe.[1] Therefore the electricity has to come from some other source, which all generate life-cycle carbon emissions.[2] 1. https://en.wikipedia.org/wiki/Second_law_of_thermodynamics https://en.wikipedia.org/wiki/Second_law_of_thermodynamics 2. https://en.wikipedia.org/wiki/Life-cycle_greenhouse-gas_emissions_of_energy_sources https://en.wikipedia.org/wiki/Life-cycle_greenhouse-gas_emis...
pfdietz 7y ago
The water itself is also a problem, in the stratosphere. I think this places an ultimate limit on the number of rocket launches at about 1 million Starship launches per year.

redis_mlc 7y ago

Injecting combustion products into the upper atmosphere is something we really need to study more. I supported the Ozone Hole studies in the mid 80's, and we found CFCs destroyed a protective part of our atmosphere. That recovered over time, but there are some rogue manufacturers using CFCs again, and leaking massive quantities. We know airborne nuclei like soot cause localized precipitation, so that does change weather (it's called cloud seeding.) We really need to know more about the effect of rockets at high altitudes, and airliner jet engines at 30,000'. I have a strong feeling airliners have a significant effect due to the volume of air traffic and how dirty burning jet fuel is. To see how jet engines could have a significant effect, there are around 10,000 airliners worldwide, which are in the air more than 12 hours each per day typically. The break in air travel due do corona virus is an excellent time to compare atmospheric samples before and after the pause.

MaxBarraclough 7y ago
> there are some rogue manufacturers using CFCs again, and leaking massive quantities Is it practical to track down the culprits? I presume it would mean prison time.
- dmos62 7y ago
  Sorry to be the pessimist, but big business and prison time don't fit into the same sentence.
- baq 7y ago
  If the factory is in China, possible outcomes range from nothing to permanent disappearance. Finding emitters should be easy from satellites.
t0mas88 7y ago
The data does not support the common opinion that airplanes are terrible for the environment. Their total contribution to for example CO2 is tiny compared to industry and electricity generation. Somehow the climate activists have decided to make a lot of noise about flying but it's mostly unfounded. They go as far as using very old models of planes in their calculations (e.g. a 737-400 model) and claiming that's the amount of CO2 per passenger of all air travel. While that model is out of use by the airline for at least 15 years already. It was designed in 1985. So beware of the data and tricks like this when you're told flying is so bad for the environment.

bryanlarsen 7y ago

Elon Musk plans on refueling his rockets on Mars using locally produced methane. Using solar power, he'll create methane and liquid oxygen from CO2 and water. If he then burns the methane and liquid oxygen in a rocket engine you get your CO2 and water back. Thus the process is carbon neutral. Before he does it on Mars he'll have to perfect it on Earth first. I hope he does more than that and starts using carbon neutral methane for all his Starship flights on Earth.

DennisP 7y ago
Yep, the article talks about that.

DennisP 7y ago

I was pretty surprised to see that Starship flying point-to-point is only about twice as bad on emissions per passenger as a 747.

mrfusion 7y ago
Zero drag for 99% of your trip is pretty awesome.
mr_toad 7y ago
In theory, methane generation, and thus metholox rockets could be made carbon neutral. https://en.wikipedia.org/wiki/Sabatier_reaction https://en.wikipedia.org/wiki/Sabatier_reaction

orbital-decay 7y ago

The article implies that rockets burn 100% of their fuel, which is an oversimplification for most thrusters. There's also a fair amount of residual fuel and oxidizer in the piping, at least part of which is dumped into the environment. While it isn't that scary for something like kerolox, it's a concern for hypergolics.

efreak 7y ago
Actually, this is mentioned in the article, in the "HOW MUCH DO DIFFERENT ROCKETS EMIT?" section, and gets more into it in the linked raptor article[1] > Although all rocket engines do run fuel rich for the right balance of heat management and performance, so there is likely going to be unburnt fuel expelled regardless of the cycle type, but much more when it is an open cycle engine. 1: https://everydayastronaut.com/raptor-engine/ https://everydayastronaut.com/raptor-engine/