3 ms·

Unfortunately, small thrusters are less efficient than large ones, overgeneralizing of course. There are a number of components that cannot be scaled down indef

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.

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.