4 ms·

"Only slightly more seriously, it would be very impressive if they could pull it off, but having seen the deployment of Iridium (66), GPS (32), GLONASS

"Only slightly more seriously, it would be very impressive if they could pull it off, but having seen the deployment of Iridium (66), GPS (32), GLONASS (24) , and Galileo (30) it doesn't seem like we have a non-nation state that is up to the challenge of putting 600(!) satellites into orbit all at once." It looks like these satellites will be a lot smaller than Iridium ones -- from the BBC article, about 150 kg each, vs. ~689 kg [0] for Iridiums. The total orbiting mass is only twice that of the Iridium constellation. 600 * 150 kg = 90,000 kg 66 * 689 kg = 45,474 kg Naively, they could lift everything in maybe five Ariane V (ECA) launches, for ~$1 billion at market pricing [1]. That'd mean packing over a hundred microsats in one payload fairing. I'm not sure how close this is to reality: I'd guess there'd need to be a lot of structure overhead too. [0] https://en.wikipedia.org/wiki/Iridium_satellite_constellation https://en.wikipedia.org/wiki/Iridium_satellite_constellatio... [1] http://www.spaceflight101.com/ariane-5-eca.html http://www.spaceflight101.com/ariane-5-eca.html ($200 MM/launch, 21,000 kg payload to LEO)

ChuckMcM 11y ago
Well for one the satellites wouldn't have enough fuel on board to do orbital plane changes, to at a minimum its going to be 20 launches if they want to hit 20 different orbital planes. I have yet to find out how they expect to do station keeping with that low mass.
- Dylan16807 11y ago
  Shouldn't station-keeping be nearly independent of mass? Devote the same percentage to the fuel tank and use the tiniest working thruster available.
  - TheLoneWolfling 11y ago
    Unfortunately, small thrusters are less efficient than large ones, overgeneralizing of course. There are a number of components that cannot be scaled down indefinitely. Although there are other potential options (EDTs, etc, etc) that don't have as much difficulty with scaling.
    - mapt 11y ago
      Not true. You can still get ~300s Isp all the way down to a ~1kg thruster: http://cs.astrium.eads.net/sp/spacecraft-propulsion/bipropellant-thrusters/10n-thruster.html http://cs.astrium.eads.net/sp/spacecraft-propulsion/bipropel... That's not what they'll be using, though. They'll be using Hall Effect thrusters.
      - TheLoneWolfling 11y ago
        Except that you'd still only need that same 1kg thruster on a 500kg satellite that you'd need on a 10kg satellite. Which is what I was talking about. With satellites and chemical thrusters, it's pretty much "the lightest possible". Thrust to mass ratio is almost irrelevant. Almost any thruster will have the thrust required. And I'm kind of surprised by the ion thrusters. I wouldn't assume that they had the thrust required to stationkeep in LEO - the drag in LEO being as high as it is.
        mapt 11y ago
        First, this is extremely high for LEO, ~1200km. Drag is negligible, decay will take thousands of years. At around ~800km, solar sails start to become practical because aerodynamic drag drops below photon pressure. Ion thrusters and photovoltaics are COTS techs which are vastly more powerful than solar sails, which exist only at the prototype/demo stage. Ion thrusters are practical to fight drag down to around ~200km given the right design, or are perfectly happy at 300-350 given a typical suboptimal design. GOCE managed it down to ~230km, after performing a multiyear mission at ~260km: http://www.spaceflight101.com/goce-re-entry.html http://www.spaceflight101.com/goce-re-entry.html
        TheLoneWolfling 11y ago
        Good to know, thanks. And interesting. Always nice to see hard numbers.
        Dylan16807 11y ago
        >Except that you'd still only need that same 1kg thruster on a 500kg satellite that you'd need on a 10kg satellite. It might be bad for truly tiny sats, but we're talking about 150kg vs. 700kg. 1kg is perfectly fine for those.
- deleted 11y ago
  [deleted]

ChuckMcM 11y ago

Well for one the satellites wouldn't have enough fuel on board to do orbital plane changes, to at a minimum its going to be 20 launches if they want to hit 20 different orbital planes. I have yet to find out how they expect to do station keeping with that low mass.

Dylan16807 11y ago
Shouldn't station-keeping be nearly independent of mass? Devote the same percentage to the fuel tank and use the tiniest working thruster available.
- TheLoneWolfling 11y ago
  Unfortunately, small thrusters are less efficient than large ones, overgeneralizing of course. There are a number of components that cannot be scaled down indefinitely. Although there are other potential options (EDTs, etc, etc) that don't have as much difficulty with scaling.
  - mapt 11y ago
    Not true. You can still get ~300s Isp all the way down to a ~1kg thruster: http://cs.astrium.eads.net/sp/spacecraft-propulsion/bipropellant-thrusters/10n-thruster.html http://cs.astrium.eads.net/sp/spacecraft-propulsion/bipropel... That's not what they'll be using, though. They'll be using Hall Effect thrusters.
    - TheLoneWolfling 11y ago
      Except that you'd still only need that same 1kg thruster on a 500kg satellite that you'd need on a 10kg satellite. Which is what I was talking about. With satellites and chemical thrusters, it's pretty much "the lightest possible". Thrust to mass ratio is almost irrelevant. Almost any thruster will have the thrust required. And I'm kind of surprised by the ion thrusters. I wouldn't assume that they had the thrust required to stationkeep in LEO - the drag in LEO being as high as it is.
      - mapt 11y ago
        First, this is extremely high for LEO, ~1200km. Drag is negligible, decay will take thousands of years. At around ~800km, solar sails start to become practical because aerodynamic drag drops below photon pressure. Ion thrusters and photovoltaics are COTS techs which are vastly more powerful than solar sails, which exist only at the prototype/demo stage. Ion thrusters are practical to fight drag down to around ~200km given the right design, or are perfectly happy at 300-350 given a typical suboptimal design. GOCE managed it down to ~230km, after performing a multiyear mission at ~260km: http://www.spaceflight101.com/goce-re-entry.html http://www.spaceflight101.com/goce-re-entry.html
        TheLoneWolfling 11y ago
        Good to know, thanks. And interesting. Always nice to see hard numbers.
      - Dylan16807 11y ago
        >Except that you'd still only need that same 1kg thruster on a 500kg satellite that you'd need on a 10kg satellite. It might be bad for truly tiny sats, but we're talking about 150kg vs. 700kg. 1kg is perfectly fine for those.
deleted 11y ago
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