3 ms·

100 tons of payload. Rockets are typically about 2% payload so 5000 tons fully fuelled. Fuel and oxidizer combine to H2O, OH, CO and CO2. So, not all the exhaus

100 tons of payload. Rockets are typically about 2% payload so 5000 tons fully fuelled. Fuel and oxidizer combine to H2O, OH, CO and CO2. So, not all the exhaust product is CO2. But some of the CO released is combined with atmospheric oxygen to CO2, so that increases the mass of CO2 besides direct propellant mass. We could as first guess say that it's about 5000 tons of CO2 per launch. So 1000 launches would be 5 million tons. US CO2 emissions per capita are about 16 tons per year, so it would be equivalent to the yearly emissions of 300,000 Americans or one thousandth of the country's yearly emissions. 10,000 launches would be 1% of US total emissions.

moralestapia 5y ago
Except it's not 10,000 launches, it's 170,000 (see other comments here). So that's 850M tons, about a 10% increase (on top of the 2nd most polluting country in the world), so yeah, not happening. I would personally rally against the govt. (and everything that allowed that to happen) if Elon gets a free pass on that.
- garmaine 5y ago
  The plan is to use atmospheric processing to produce methane and LOX on-site using renewable power. So it’d be net-zero carbon emissions.
- Gravityloss 5y ago
  Ok, I'm not that familiar with the plans with starship. I think the premise of the article is wrong anyway. I think no matter what the system is like, it still makes sense to optimize for mass in a reasonable way. That means, not sending dead weight to high delta vee. Leave big tanks or engines behind. It's a bit like you don't transport your car with the airplane. It would be madness. Exponentials are unintuitive. The total mass of all fuel in all stages is directly proportional to the mass that needs to be sent to the highest delta vee. So for example (to take a few shortcuts) if your moon ascent stage is 1% heavier, everything has to be 1% heavier, including the first stage of the launcher. So 1 kg in the ascent stage might not look like much but it grows the first stage at something like 1000 kg. That's why I'm really skeptical of the architecture of landing atmospheric stages to the surface. They are just unnecessarily heavy. You have maybe quadrupled your total launch amount from the surface (haven't done an analysis). Early Apollo planning had direct landing because docking in orbit had not been demonstrated. Gemini validated that. Orbital docking works fine and Apollo could continue with muchh more efficient architectures. Actually, docking has gotten a lot better, we did have Apollo, yes, and we have robotic tugs routinely flying to ISS. Engines haven't made significant progress since the sixties, not enough to warrant really big architectural changes towards less mass efficiency. If anything, the improved docking and automation that has already been demonstrated would swing the architectural plans for moon or Mars to have even more docking, berthing, refueling and staging! Direct landing might only make sense with something like nuclear propulsion...
  - garmaine 5y ago
    > That's why I'm really skeptical of the architecture of landing atmospheric stages to the surface. They are just unnecessarily heavy. You have maybe quadrupled your total launch amount from the surface (haven't done an analysis). Lunar starship is not an atmospheric stage.
    - Gravityloss 5y ago
      In the fine article, in Casey Handmer's plan, Starship is landed to the surface and returns directly to LEO or even to Earth surface. So yes the heat shield goes all the way down to the lunar surface and back. https://caseyhandmer.files.wordpress.com/2021/03/artemisspacex.png?w=540&zoom=2 https://caseyhandmer.files.wordpress.com/2021/03/artemisspac...
      - garmaine 5y ago
        The Starship actually being built by SpaceX under the HLS contract for NASA has no heat shield or atmospheric engines. It is meant to be expendable, or for reuse only in space without servicing.
        Gravityloss 5y ago
        Yes, which the fine article was criticizing.

moralestapia 5y ago

Except it's not 10,000 launches, it's 170,000 (see other comments here). So that's 850M tons, about a 10% increase (on top of the 2nd most polluting country in the world), so yeah, not happening. I would personally rally against the govt. (and everything that allowed that to happen) if Elon gets a free pass on that.

garmaine 5y ago
The plan is to use atmospheric processing to produce methane and LOX on-site using renewable power. So it’d be net-zero carbon emissions.
Gravityloss 5y ago
Ok, I'm not that familiar with the plans with starship. I think the premise of the article is wrong anyway. I think no matter what the system is like, it still makes sense to optimize for mass in a reasonable way. That means, not sending dead weight to high delta vee. Leave big tanks or engines behind. It's a bit like you don't transport your car with the airplane. It would be madness. Exponentials are unintuitive. The total mass of all fuel in all stages is directly proportional to the mass that needs to be sent to the highest delta vee. So for example (to take a few shortcuts) if your moon ascent stage is 1% heavier, everything has to be 1% heavier, including the first stage of the launcher. So 1 kg in the ascent stage might not look like much but it grows the first stage at something like 1000 kg. That's why I'm really skeptical of the architecture of landing atmospheric stages to the surface. They are just unnecessarily heavy. You have maybe quadrupled your total launch amount from the surface (haven't done an analysis). Early Apollo planning had direct landing because docking in orbit had not been demonstrated. Gemini validated that. Orbital docking works fine and Apollo could continue with muchh more efficient architectures. Actually, docking has gotten a lot better, we did have Apollo, yes, and we have robotic tugs routinely flying to ISS. Engines haven't made significant progress since the sixties, not enough to warrant really big architectural changes towards less mass efficiency. If anything, the improved docking and automation that has already been demonstrated would swing the architectural plans for moon or Mars to have even more docking, berthing, refueling and staging! Direct landing might only make sense with something like nuclear propulsion...
- garmaine 5y ago
  > That's why I'm really skeptical of the architecture of landing atmospheric stages to the surface. They are just unnecessarily heavy. You have maybe quadrupled your total launch amount from the surface (haven't done an analysis). Lunar starship is not an atmospheric stage.
  - Gravityloss 5y ago
    In the fine article, in Casey Handmer's plan, Starship is landed to the surface and returns directly to LEO or even to Earth surface. So yes the heat shield goes all the way down to the lunar surface and back. https://caseyhandmer.files.wordpress.com/2021/03/artemisspacex.png?w=540&zoom=2 https://caseyhandmer.files.wordpress.com/2021/03/artemisspac...
    - garmaine 5y ago
      The Starship actually being built by SpaceX under the HLS contract for NASA has no heat shield or atmospheric engines. It is meant to be expendable, or for reuse only in space without servicing.
      - Gravityloss 5y ago
        Yes, which the fine article was criticizing.