My KSP-fu is failing me here... how is it possible to match Mars' circular solar orbit at a slower velocity? Wouldn't a different velocity imply a different orbital distance from the sun?
> My KSP-fu is failing me here... how is it possible to match Mars' circular solar orbit at a slower velocity?
You aren't actually trying to match it; as I understand this kind of orbit is a slightly slower (so slightly closer, on average) orbit that the vessel achieves somewhat ahead of Mars, so that when Mars passes it, Mars' gravity is enough to capture the vessel. In essence, some of the energy to match the orbit comes from Mars itself (slowing down Mars, but for any realistic spacecraft this is completely negligible because of the enormous mass ratio between the planet and the craft.)
Sounds like it's that thing in KSP where you time your insertion to The Mun's sphere of influence just right so you don't have to burn retro to achieve Munar orbit. Basically hit it so that you do gravity-assisted deceleration, and end up in orbit around it—typically badly elliptical orbit, but that's cheap to correct.
Mars' orbit is not circular, and spacecraft's would not be, either. They would be in slightly different (and intersecting, or nearly so) elliptical orbits, which would allow Mars to gravitationally capture the spacecraft when it approached closely enough.
Is performing a second burn to circularize a craft's orbit to near-sync with Martian orbit really cheaper than a deceleration burn? In fact, that would just be a complete Hohmann transfer.
I'd guess the target orbit for a craft performing this maneuver would still have a periapsis in the neighborhood of Earth's orbit, meaning it'd still be very unlike Mars' orbit until the craft was captured by Martian gravity.
(googles a bit)
It looks like these exploit Lagrange points somehow[1]. Precision maneuvers and weird, long routes to the target body. I'm not quite following how this works with only two bodies (Sun and Mars), versus the Sun-Earth-Moon trio. Wikipedia claims the Mars Orbiter Mission used a low-energy transfer at some point, but I can't figure out whether that was for the insertion into Martian orbit or some earlier maneuver it performed.
