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Starship is methane-powered. There are ways to generate methane sustainably (from C02 and water); that's even an essential part of the plan for Mars. I strongly

Starship is methane-powered. There are ways to generate methane sustainably (from C02 and water); that's even an essential part of the plan for Mars. I strongly suspect they'll want to test it on Earth before, and having an appliance on the platform that generates the needed propellant for passenger flight would be a very good test (developing something that works reliably with minimal / no human intervention).

sandworm101 6y ago
The fuels in the rocket. The fuels in the support vehicles. The fuels for the platform. The fuels in the helicopters. Even if all of them are produced from solar power, a 747 needs less than 1% of the same total fuel per passenger. No matter how it is fueled, a ballistic rocket needs orders of magnitude more energy than conventional flight. It is not an energy-efficient means of realworld transport.
- jackric 6y ago
  Then price in carbon neutral fuel production to the ticket. There will be passengers rich enough to pay it. If you've got a problem with that I imagine your real issues are about status envy not environmentalism.
  - sandworm101 6y ago
    Lol, I'm no communist but I do appreciate that market forces alone will never address the carbon/energy problem, let alone the wider problem of pollution overall. Just because someone has the money do to so doesn't mean that we should support them burning away the energy to light a small city simply to get to their vacation spot a few hours faster than on a private jet.
    - jackric 6y ago
      How about reaching a dying father a few hours faster? A middle class person might judge the extra $5-10k (from savings) worth it. If SpaceX/energy company deploys a new nuclear power plant (and one day fusion) to provide the energy, why should you care? It's a new energy source and not competing away your personal idea of worthwhile energy use.
- eyesee 6y ago
  Not sure where you're getting these figures. Here's an analysis which estimates CO2 emissions from Starship for E2E will be roughly similar to those from a 777 flight based on fuel consumption. Depending upon how the methane is generated it could be a carbon-neutral flight. This doesn't include support vehicles, but that would be quite speculative at this stage. https://www.nextbigfuture.com/2019/12/spacex-rocket-emissions-similar-to-large-jets-crossing-the-oceans.html https://www.nextbigfuture.com/2019/12/spacex-rocket-emission...
  - sandworm101 6y ago
    Look deeper at those numbers. Net fuel consumption/emissions is different than "rocket emissions". Rocket fuel isn't diesel. The emissions from the actual rocket in flight do not capture the total emissions generated in the creation/preparation/compression of rocket fuels. Some rockets produce literally zero carbon during flight (liquid hydrogen + liquid oxygen = water) but that doesn't mean plenty of coal/oil wasn't used in the creation of those fuels.
  - m4rtink 6y ago
    Yep - pushing air away for 12+ hours at high sub sonic speeds might indeed be less efficient than a sub orbital flight where you exit the atmosphere in a couple minutes and cover most of the distance without meaningful air resistance in the vacuum of space.
- sacred_numbers 6y ago
  Do you have any numbers to back that up? A 747 burns 10-11 tons of fuel per hour and carries about 360 passengers. For a 12 hour flight, that is about 350kg of fuel per passenger. Starship's tanks hold approximately 250 tons of fuel and 950 tons of liquid oxygen. In order to match the per passenger fuel efficiency of a 747 they would need to carry about 700 passengers. Starship has about 20% more internal volume as a 747, so it seems likely that they would be able to fit at least the same number of passengers. That puts them at about 50% of the fuel efficiency of a 747. In addition, methane combustion produces 2.75kg of CO2 per kg of fuel, while kerosene produces 3kg CO2 per kg of fuel. If they are able to fit 20% more passengers than a 747 due to the larger internal volume then they would be within about 66% efficiency on a CO2 emissions per passenger basis.
  - sandworm101 6y ago
    As I replied to others, rocket fuel is very different. The total carbon emissions include not just the fuel used by the rocket but the fuels used to create those fuels before the flight. Liquid oxygen is not carbon-free as creating liquid oxygen requires lots and lots of energy. So too methane which is heavily refined/compressed/cooled, processes that take more energy, create more emissions, than burning the fuel itself during flight. The fuel for a 747 is not nearly as energy/carbon-intensive to create.
aphextron 6y ago
> Starship is methane-powered. There are ways to generate methane sustainably (from C02 and water); It's not about the generation. Burning methane results in a 1:1 emission of CO2 [0]; literally the equivalent of just dumping pure carbon dioxide into the atmosphere. https://www.quora.com/What-are-the-products-of-methane-burned-in-oxygen?share=1 https://www.quora.com/What-are-the-products-of-methane-burne...
- jcims 6y ago
  In the process that would likely be used the CO2 would be sourced from the atmosphere. https://en.wikipedia.org/wiki/Sabatier_reaction https://en.wikipedia.org/wiki/Sabatier_reaction
  - sandworm101 6y ago
    Ya, but that isn't happening. Look at where liquid hydrogen for rockets is sourced. It could be made from water. In reality, it is made from hydrocarbons because that is cheaper. And even if CO2 is pulled from the air, a huge amount of energy is need to compress/store that rocket fuel, energy that could be put to far better uses. Instead of launching a passenger rocket to london, I'd rather divert that energy into shutting a coal-fired powerplant for a week or two. Once all those powerplants are shut, then we should look at passenger rocket services.
    - emilecantin 6y ago
      I don't doubt you're right for most existing rockets, but I think the main difference here is that SpaceX has every reason to test the hell out of their propellant-producing appliances here on Earth, even if it's not economical at the beginning. They depend on these appliances working perfectly on Mars for the return trip, so they need to be _very_ reliable.
    - ben_w 6y ago
      If these vehicles were from anyone besides a company whose explicit goal is to develop an interplanetary colony ship whose duty cycle will require the launch infrastructure on the other planet to convert atmospheric CO2 into methane using solar power, I’d agree — it hasn’t been done, it’s not economical to do it that way yet. But Musk needs this process to become economical so that Mars can become economical. (The same tech may, ironically given Tesla, compete with batteries for the energy storage PV calls for).

sandworm101 6y ago

The fuels in the rocket. The fuels in the support vehicles. The fuels for the platform. The fuels in the helicopters. Even if all of them are produced from solar power, a 747 needs less than 1% of the same total fuel per passenger. No matter how it is fueled, a ballistic rocket needs orders of magnitude more energy than conventional flight. It is not an energy-efficient means of realworld transport.

jackric 6y ago
Then price in carbon neutral fuel production to the ticket. There will be passengers rich enough to pay it. If you've got a problem with that I imagine your real issues are about status envy not environmentalism.
- sandworm101 6y ago
  Lol, I'm no communist but I do appreciate that market forces alone will never address the carbon/energy problem, let alone the wider problem of pollution overall. Just because someone has the money do to so doesn't mean that we should support them burning away the energy to light a small city simply to get to their vacation spot a few hours faster than on a private jet.
  - jackric 6y ago
    How about reaching a dying father a few hours faster? A middle class person might judge the extra $5-10k (from savings) worth it. If SpaceX/energy company deploys a new nuclear power plant (and one day fusion) to provide the energy, why should you care? It's a new energy source and not competing away your personal idea of worthwhile energy use.
eyesee 6y ago
Not sure where you're getting these figures. Here's an analysis which estimates CO2 emissions from Starship for E2E will be roughly similar to those from a 777 flight based on fuel consumption. Depending upon how the methane is generated it could be a carbon-neutral flight. This doesn't include support vehicles, but that would be quite speculative at this stage. https://www.nextbigfuture.com/2019/12/spacex-rocket-emissions-similar-to-large-jets-crossing-the-oceans.html https://www.nextbigfuture.com/2019/12/spacex-rocket-emission...
- sandworm101 6y ago
  Look deeper at those numbers. Net fuel consumption/emissions is different than "rocket emissions". Rocket fuel isn't diesel. The emissions from the actual rocket in flight do not capture the total emissions generated in the creation/preparation/compression of rocket fuels. Some rockets produce literally zero carbon during flight (liquid hydrogen + liquid oxygen = water) but that doesn't mean plenty of coal/oil wasn't used in the creation of those fuels.
- m4rtink 6y ago
  Yep - pushing air away for 12+ hours at high sub sonic speeds might indeed be less efficient than a sub orbital flight where you exit the atmosphere in a couple minutes and cover most of the distance without meaningful air resistance in the vacuum of space.
sacred_numbers 6y ago
Do you have any numbers to back that up? A 747 burns 10-11 tons of fuel per hour and carries about 360 passengers. For a 12 hour flight, that is about 350kg of fuel per passenger. Starship's tanks hold approximately 250 tons of fuel and 950 tons of liquid oxygen. In order to match the per passenger fuel efficiency of a 747 they would need to carry about 700 passengers. Starship has about 20% more internal volume as a 747, so it seems likely that they would be able to fit at least the same number of passengers. That puts them at about 50% of the fuel efficiency of a 747. In addition, methane combustion produces 2.75kg of CO2 per kg of fuel, while kerosene produces 3kg CO2 per kg of fuel. If they are able to fit 20% more passengers than a 747 due to the larger internal volume then they would be within about 66% efficiency on a CO2 emissions per passenger basis.
- sandworm101 6y ago
  As I replied to others, rocket fuel is very different. The total carbon emissions include not just the fuel used by the rocket but the fuels used to create those fuels before the flight. Liquid oxygen is not carbon-free as creating liquid oxygen requires lots and lots of energy. So too methane which is heavily refined/compressed/cooled, processes that take more energy, create more emissions, than burning the fuel itself during flight. The fuel for a 747 is not nearly as energy/carbon-intensive to create.

aphextron 6y ago

> Starship is methane-powered. There are ways to generate methane sustainably (from C02 and water); It's not about the generation. Burning methane results in a 1:1 emission of CO2 [0]; literally the equivalent of just dumping pure carbon dioxide into the atmosphere. https://www.quora.com/What-are-the-products-of-methane-burned-in-oxygen?share=1 https://www.quora.com/What-are-the-products-of-methane-burne...

jcims 6y ago
In the process that would likely be used the CO2 would be sourced from the atmosphere. https://en.wikipedia.org/wiki/Sabatier_reaction https://en.wikipedia.org/wiki/Sabatier_reaction
- sandworm101 6y ago
  Ya, but that isn't happening. Look at where liquid hydrogen for rockets is sourced. It could be made from water. In reality, it is made from hydrocarbons because that is cheaper. And even if CO2 is pulled from the air, a huge amount of energy is need to compress/store that rocket fuel, energy that could be put to far better uses. Instead of launching a passenger rocket to london, I'd rather divert that energy into shutting a coal-fired powerplant for a week or two. Once all those powerplants are shut, then we should look at passenger rocket services.
  - emilecantin 6y ago
    I don't doubt you're right for most existing rockets, but I think the main difference here is that SpaceX has every reason to test the hell out of their propellant-producing appliances here on Earth, even if it's not economical at the beginning. They depend on these appliances working perfectly on Mars for the return trip, so they need to be _very_ reliable.
  - ben_w 6y ago
    If these vehicles were from anyone besides a company whose explicit goal is to develop an interplanetary colony ship whose duty cycle will require the launch infrastructure on the other planet to convert atmospheric CO2 into methane using solar power, I’d agree — it hasn’t been done, it’s not economical to do it that way yet. But Musk needs this process to become economical so that Mars can become economical. (The same tech may, ironically given Tesla, compete with batteries for the energy storage PV calls for).