5 ms·

All terrestrial transport ideas from SpaceX I've seen involved Starship, not Falcon 9/Dragon. I don't know how that compares with a typical airliner in terms o

by avian 5y ago

All terrestrial transport ideas from SpaceX I've seen involved Starship, not Falcon 9/Dragon. I don't know how that compares with a typical airliner in terms of miles per gallon (probably not much better than Dragon). However Starship runs on methane and that should in theory be easy to produce from atmospheric CO2 and electricity from renewable sources. In any case, I don't think many people took the idea of using Starship as a terrestrial passenger transport seriously.

immmmmm 5y ago
be it methane or RP1 you're subjected to the laws of thermodynamics. namely converting CO2 to any of those will require more energy than delivered by your rocket or car. also rocket engines are already some of the most efficient thermal engines available/possible, starship won't change that.
- xoa 5y ago
  None of which has anything whatsoever to do with the issue of AGW though. For the purposes of warming the planet, direct energy usage and emission by humanity is irrelevant (utterly swamped by solar insolation for starters). What's driving it is our changing the net levels of greenhouse gases and in turn the amount of energy retained vs radiated into space. So what matters for dealing with climate disruption is making sure our activities are greenhouse neutral (and for a while we should go carbon negative), all debates of "efficiency" or "luxury" or whatever are extremely foolish distractions. If everything is greenhouse neutral with associated prices becoming clear than people can figure the rest out from there about where they wish to allocate their extra resources. SpaceX intends to develop direct atmospheric methane generation from CO2, which they have to do anyway for their Mars plans because that's the only way to do in-situ refueling there (plenty of CO2 in the atmosphere, not exactly a lot of natural gas fields). Taking into account any methane leaks and correcting for its few decades of enhance greenhouse effect before it decomposes to CO2, they certainly could make Starship carbon neutral and if they do it doesn't matter how much "energy" in the abstract it uses beyond price. Solar and wind power have plenty positive power factors. Worth noting that in principle nothing is special about Starship here, carbon neutral RP1 could be made as well (at a further hit to conversion efficiency and thus price). In practice though green methane is more practical and will amortize better given its use elsewhere in the solar system.
  - leoedin 5y ago
    Generating rocket fuels with renewables will only be carbon neutral when we have an excess of renewable energy. Until then, either the solar panels would be better used to replace fossil fuel generation on the grid, or the synthesised methane would be better used to replace a more necessary use of fossil methane. It's hard to argue that a method of transport so incredibly energy inefficient will be a good thing until we're swimming in so much excess energy that we've got nothing better to do with it. Even with the massive improvements in renewables over the last few decades, we're a long, long way from that point.
    - immmmmm 5y ago
      thanks making my point clearer. presently 80% of our energy comes from fossil fuels, we need to peak emissions in 4 years max and do -50% in nine years. putting tourists in space doesn't seems like a priority.
    - xoa 5y ago
      >Generating rocket fuels with renewables will only be carbon neutral when we have an excess of renewable energy Absolutely wrong. It is not a zero sum game. In terms of raw money and capability, we could have gone carbon neutral in the developed world at least decades ago. We could be aiming for that universally right now, the US alone has dumped trillions and trillions into war and pandemic response over just the last 10 years. It hasn't happened because "we" collectively have not chosen to make it happen. SpaceX, or anyone else, making themselves carbon neutral when they are under no external compulsion too is pure gain. They don't need to solve all the problems on the fucking planet first. That has always been one of the most irritating fallacies in the whole AGW discussion. >It's hard to argue that a method of transport so incredibly energy inefficient will be a good thing until we're swimming in so much excess energy that we've got nothing better to do with it. No, it isn't. It's trivial to argue: if it's greenhouse neutral and all the externalities are built-in then if anyone wants to pay for it by definition it is a good thing. In fact at that point it'd be a BETTER thing than traditional "more efficient" methods of transport which aren't greenhouse neutral! You're coming up with this silly subjective morality things when the only morality involved is externalized harm. If that is eliminated and people still consider the service worth it when they can see the true price then that's all that matters.
immmmmm 5y ago
i heard that it's basically 1000 worst than an airplane
- jve 5y ago
  Ehh, someone has already done the calculation: https://everydayastronaut.com/rocket-pollution/ https://everydayastronaut.com/rocket-pollution/ It may be order-of-magnitude worse, but not 3 orders of magnitude (If you look forward to using starship for human transportation)

by avian 5y ago

immmmmm 5y ago

be it methane or RP1 you're subjected to the laws of thermodynamics. namely converting CO2 to any of those will require more energy than delivered by your rocket or car. also rocket engines are already some of the most efficient thermal engines available/possible, starship won't change that.

xoa 5y ago
None of which has anything whatsoever to do with the issue of AGW though. For the purposes of warming the planet, direct energy usage and emission by humanity is irrelevant (utterly swamped by solar insolation for starters). What's driving it is our changing the net levels of greenhouse gases and in turn the amount of energy retained vs radiated into space. So what matters for dealing with climate disruption is making sure our activities are greenhouse neutral (and for a while we should go carbon negative), all debates of "efficiency" or "luxury" or whatever are extremely foolish distractions. If everything is greenhouse neutral with associated prices becoming clear than people can figure the rest out from there about where they wish to allocate their extra resources. SpaceX intends to develop direct atmospheric methane generation from CO2, which they have to do anyway for their Mars plans because that's the only way to do in-situ refueling there (plenty of CO2 in the atmosphere, not exactly a lot of natural gas fields). Taking into account any methane leaks and correcting for its few decades of enhance greenhouse effect before it decomposes to CO2, they certainly could make Starship carbon neutral and if they do it doesn't matter how much "energy" in the abstract it uses beyond price. Solar and wind power have plenty positive power factors. Worth noting that in principle nothing is special about Starship here, carbon neutral RP1 could be made as well (at a further hit to conversion efficiency and thus price). In practice though green methane is more practical and will amortize better given its use elsewhere in the solar system.
- leoedin 5y ago
  Generating rocket fuels with renewables will only be carbon neutral when we have an excess of renewable energy. Until then, either the solar panels would be better used to replace fossil fuel generation on the grid, or the synthesised methane would be better used to replace a more necessary use of fossil methane. It's hard to argue that a method of transport so incredibly energy inefficient will be a good thing until we're swimming in so much excess energy that we've got nothing better to do with it. Even with the massive improvements in renewables over the last few decades, we're a long, long way from that point.
  - immmmmm 5y ago
    thanks making my point clearer. presently 80% of our energy comes from fossil fuels, we need to peak emissions in 4 years max and do -50% in nine years. putting tourists in space doesn't seems like a priority.
  - xoa 5y ago
    >Generating rocket fuels with renewables will only be carbon neutral when we have an excess of renewable energy Absolutely wrong. It is not a zero sum game. In terms of raw money and capability, we could have gone carbon neutral in the developed world at least decades ago. We could be aiming for that universally right now, the US alone has dumped trillions and trillions into war and pandemic response over just the last 10 years. It hasn't happened because "we" collectively have not chosen to make it happen. SpaceX, or anyone else, making themselves carbon neutral when they are under no external compulsion too is pure gain. They don't need to solve all the problems on the fucking planet first. That has always been one of the most irritating fallacies in the whole AGW discussion. >It's hard to argue that a method of transport so incredibly energy inefficient will be a good thing until we're swimming in so much excess energy that we've got nothing better to do with it. No, it isn't. It's trivial to argue: if it's greenhouse neutral and all the externalities are built-in then if anyone wants to pay for it by definition it is a good thing. In fact at that point it'd be a BETTER thing than traditional "more efficient" methods of transport which aren't greenhouse neutral! You're coming up with this silly subjective morality things when the only morality involved is externalized harm. If that is eliminated and people still consider the service worth it when they can see the true price then that's all that matters.

immmmmm 5y ago

i heard that it's basically 1000 worst than an airplane

jve 5y ago
Ehh, someone has already done the calculation: https://everydayastronaut.com/rocket-pollution/ https://everydayastronaut.com/rocket-pollution/ It may be order-of-magnitude worse, but not 3 orders of magnitude (If you look forward to using starship for human transportation)