Quote from: toruonu on 11/13/2014 08:50 amCan someone point to a doc with regardsto how the new electric satellites work with regard to propulsion. Is it a form of ion drive with electricity providing the large momentum for the charged particles or is it using some magnetic fields to adjust itself and accelerate and what kind of limitations that has in usability at random points in the satellites orbits.http://en.wikipedia.org/wiki/Ion_thruster
Can someone point to a doc with regardsto how the new electric satellites work with regard to propulsion. Is it a form of ion drive with electricity providing the large momentum for the charged particles or is it using some magnetic fields to adjust itself and accelerate and what kind of limitations that has in usability at random points in the satellites orbits.
I expect these commercial electric satellite buses to also be used for planetary missions.
Ok, so it's as I expected an ion drive. That does mean that it's still got a limited lifetime depending on the total amount of gas that's packed for the thrusters, but it's nice to see the concept finally making it to real-life usage.
So they will go to near GTO and perigee raise/circularize themselves. Like I said, not "LEO."
No, not the same environment. It is a bad idea. See Mars Observer
Quote from: Jim on 11/13/2014 12:51 pmNo, not the same environment. It is a bad idea. See Mars ObserverAre you speaking just generally, as in "interplanetary isn't the same as GEO"? From JPL data, 10 year radiation dose in GEO is 100krad, while in Mars orbit it may only be 5krad. So anything rad hardened for GEO is good enough for a lot of the solar system.And Mars Observer failed due to a leaky valve in the hypergolic propulsion system which an all solar-electric craft doesn't have. But it seems that valve could have leaked just as easily in LEO as on its way to Mars.Is there something specific that rules the 702SP bus out for wider usage?
Quote from: TrevorMonty on 11/13/2014 08:24 amI expect these commercial electric satellite buses to also be used for planetary missions.No, not the same environment. It is a bad idea. See Mars Observer
But I don't think Mars Observer is a good model for this. As EP upscales, its thermal requirements and other issues for cruise are nothing like the hypers and the antique Tiros bus mentioned.
Quote from: Space Ghost 1962 on 11/13/2014 07:32 pmBut I don't think Mars Observer is a good model for this. As EP upscales, its thermal requirements and other issues for cruise are nothing like the hypers and the antique Tiros bus mentioned.It used a RCA Satcom bus, the appendage articulation was from the Tiros bus.
If I recall correctly, it was Tiros, then RELAY, then eventually Satcom, then the last series of Tiros was built on the Satcom bus.
I see. Read it wrong. Who writes space articles in Imperial units? Very annoying.
Quote from: Space Ghost 1962 on 11/13/2014 10:32 pmIf I recall correctly, it was Tiros, then RELAY, then eventually Satcom, then the last series of Tiros was built on the Satcom bus. TIROS as in DMSP and NOAA buses. http://space.skyrocket.de/doc_sat/lockheed_tiros-n.htmThe MO bus was the Satcom-K/LM4000 bushttp://www.skyrocket.de/space/doc_sat/lockheed_4000.htm
With an Isp of 3400s, the propellant estimates I had above are actually high; it's probably more like 300kg of Xe to do the GEO insertion at 6 km/s
I'm trying to reconcile that with the other stats for the 702SP, though: it advertises 3-8kW of power, yet 4 x 25cm XIPS would be 18kW. Either I'm misunderstanding something, or they're not running continuously and the bus has substantial energy storage capability. But batteries are heavy.