3 ms·

Reusable is 8000kg to GTO, not LEO. LEO performance in fully reusable configurations is 30+ tons.

DennisP 8y ago
So assuming 32 tonnes it's $668/kg for the hardware (assuming full payloads). Probably also have to build in enough slack for occasional failed landings, but we don't know yet what the failure rate will be after the kinks are worked out.
- JshWright 8y ago
  You'd be hard pressed to fit 32 tons inside Falcon Heavy's fairing. It's far more likely to be volume constrained than mass constrained when flying to LEO.
  - grey-area 8y ago
    That could bring satellite costs down a lot though - if launches are cheap and not weight limited a cheap steel frame satellite with heavy solar panels becomes feasible - all the old rules about building to optimise weight and not price go out the window. I wouldn’t be surprised if spacex also enter the satellite building business after mass producing starlink.
    - stcredzero 8y ago
      What if SpaceX could combine cheap satellites with some form of reusable propellant-less or super high ISP propulsion? I'm thinking of solar sail or solar-ion drive tugs.
    - DennisP 8y ago
      And that makes solar power satellites more feasible, especially with the BFR. Musk has expressed skepticism, famously asking "what's the conversion rate?" The answer is that microwave transmission is 40% efficient with today's technology. This isn't bad considering that average daily sunlight in geosynch is five times higher than on the ground,[1] and you don't need much storage or backup. The early SPS designs were hugely expensive monolithic beasts, but current designs use lots of identical parts (of several varieties) that self-assemble in orbit, so you get economies of scale with factory production. A year ago I read the book The Case for Space Solar Power [2], which broke down the costs in detail. With pre-SpaceX launch costs they got 15 cents/kWh, including manufacturing and ground stations. I plugged in the BFR cost Musk was claiming (I think I used $50/lb) and got about 4 cents/kWh. [1] https://en.wikipedia.org/wiki/Solar_irradiance#Irradiance_on_Earth's_surface https://en.wikipedia.org/wiki/Solar_irradiance#Irradiance_on... [2] https://www.amazon.com/Case-Space-Solar-Power-ebook/dp/B00HNZ0Z96 https://www.amazon.com/Case-Space-Solar-Power-ebook/dp/B00HN...
      - nostrademons 8y ago
        Hmm, what's the cost to put solar panels in heliocentric orbit? Dyson spheres anyone?
    - darkpuma 8y ago
      Light weight satellite construction will still be a very high priority because making the structure of the satellite lighter extends its operational lifespan. The reason is attitude control. Reaction wheels can be used to orient the satellite, but eventually reaction wheels get saturated. At that point you need to use thrusters to cancel out the reaction wheel saturation. Those thrusters require propellant, e.g. something to push against. The greater the ratio between propellant mass and structural mass the satellite has, the longer it can remain operational before the propellant runs out and your reaction wheels finally saturate, leaving your satellite tumbling useless without attitude control.
      - grey-area 8y ago
        That's a good point, though can add more propellant too if you're not mass constrained. It will be interesting to see if Falcon Heavy, and more likely starship, have a significant impact on what sort of satellites are built, and the way they are built. If they do it will probably take years before we see any changes, however spacex is ideally positioned to cash in on a transition to more mass-produced satellites if that does happen.

So assuming 32 tonnes it's $668/kg for the hardware (assuming full payloads). Probably also have to build in enough slack for occasional failed landings, but we don't know yet what the failure rate will be after the kinks are worked out.

JshWright 8y ago
You'd be hard pressed to fit 32 tons inside Falcon Heavy's fairing. It's far more likely to be volume constrained than mass constrained when flying to LEO.
- grey-area 8y ago
  That could bring satellite costs down a lot though - if launches are cheap and not weight limited a cheap steel frame satellite with heavy solar panels becomes feasible - all the old rules about building to optimise weight and not price go out the window. I wouldn’t be surprised if spacex also enter the satellite building business after mass producing starlink.
  - stcredzero 8y ago
    What if SpaceX could combine cheap satellites with some form of reusable propellant-less or super high ISP propulsion? I'm thinking of solar sail or solar-ion drive tugs.
  - DennisP 8y ago
    And that makes solar power satellites more feasible, especially with the BFR. Musk has expressed skepticism, famously asking "what's the conversion rate?" The answer is that microwave transmission is 40% efficient with today's technology. This isn't bad considering that average daily sunlight in geosynch is five times higher than on the ground,[1] and you don't need much storage or backup. The early SPS designs were hugely expensive monolithic beasts, but current designs use lots of identical parts (of several varieties) that self-assemble in orbit, so you get economies of scale with factory production. A year ago I read the book The Case for Space Solar Power [2], which broke down the costs in detail. With pre-SpaceX launch costs they got 15 cents/kWh, including manufacturing and ground stations. I plugged in the BFR cost Musk was claiming (I think I used $50/lb) and got about 4 cents/kWh. [1] https://en.wikipedia.org/wiki/Solar_irradiance#Irradiance_on_Earth's_surface https://en.wikipedia.org/wiki/Solar_irradiance#Irradiance_on... [2] https://www.amazon.com/Case-Space-Solar-Power-ebook/dp/B00HNZ0Z96 https://www.amazon.com/Case-Space-Solar-Power-ebook/dp/B00HN...
    - nostrademons 8y ago
      Hmm, what's the cost to put solar panels in heliocentric orbit? Dyson spheres anyone?
  - darkpuma 8y ago
    Light weight satellite construction will still be a very high priority because making the structure of the satellite lighter extends its operational lifespan. The reason is attitude control. Reaction wheels can be used to orient the satellite, but eventually reaction wheels get saturated. At that point you need to use thrusters to cancel out the reaction wheel saturation. Those thrusters require propellant, e.g. something to push against. The greater the ratio between propellant mass and structural mass the satellite has, the longer it can remain operational before the propellant runs out and your reaction wheels finally saturate, leaving your satellite tumbling useless without attitude control.
    - grey-area 8y ago
      That's a good point, though can add more propellant too if you're not mass constrained. It will be interesting to see if Falcon Heavy, and more likely starship, have a significant impact on what sort of satellites are built, and the way they are built. If they do it will probably take years before we see any changes, however spacex is ideally positioned to cash in on a transition to more mass-produced satellites if that does happen.