6 ms·

I must have missed it, but can anyone explain why Orbcomm wants 11 satellites in the same orbit? The stage 2 engine isn't firing in between letting the satellit

• gregr401 11y ago
  Yes, it absolutely was firing continuously around 17,000 MPH. Doesn't take long at that speed to get some distance between sats.
  • mikeash 11y ago
    The satellites are moving at that speed too....
    • dgacmu 11y ago
      But they're not all moving at the same speed if the second stage was still firing between satellite releases.
      • mikeash 11y ago
        True but irrelevant, as the second stage engine cut off before satellite deployment.
  • vpribish 11y ago
    why do you think that? the second stage engine was off during deployment.
• jacquesm 11y ago
  Leo, they are so low they don't cover a whole lot of territory. The oribits may be at slightly different altitudes simply because of the inertia of the second stage, I really should have monitored that altitude indicator during the releases, were they identical?
  • cmsmith 11y ago
    Maybe there was a secondary thruster somewhere to provide some separation. I went back and recorded the release speed (km/hr), altitude (km) for each drop: 25960 626 25954 627 25950 628 25944 630 25937 632 25935 632 A circular orbit at that height is about 29000 km around; 25 km/hour of difference between release 1 and 6 would give them a separation of 6 degrees longitude/day, or ~50 days until the faster satellites 'lap' the slowest one. Not any sort of rocket scientist, but I gather the strategy with these kind of LEO satellites is to just throw a pile of them up there semi-randomly, and count on at least one being in the neighborhood when you want to talk to it. edit: Last paragraph is wrong. See my comment two levels down for the answer.
    • jacquesm 11y ago
      The satellites themselves usually have small thrusters but I'm not sure what kind of orbital change the can effect, usually they are there for detailed maneuvering and to boost the satellite to a slightly higher orbit as it decays. When it runs out of fuel it dies so you'd try to use as little of that as possible during launch.
      • cmsmith 11y ago
        >A hydrazine propulsion system is installed on the spacecraft for orbit adjustment maneuvers and orbit maintenance providing a delta-v budget of more than 100 meters per second for each satellite. >Because OG2 satellites are launched in groups of several spacecraft, they require propulsion systems to place the satellite into different nodal planes to begin operations. There's the answer, courtesy Orbcomm.
        • jacquesm 11y ago
          Neat :) So they do their own placement. Nasty stuff, hydrazine. F16's use it as emergency fuel.
          • TeMPOraL 11y ago
• arjunnarayan 11y ago
  The satellites have their own thrusters and will use that to reposition. Changing your position within a single orbit is fairly cheap - even if you just go a few m/s, with enough time you can space out quite far.
• marze 11y ago
  The satellites themselves can adjust their individual phasing within the same orbit with minimal propellant.