Seems slow, but keep in mind it's getting there by matching orbit, not by flying straight there.. orbital mechanics are counter intuitive, if you increase your speed you move out to a larger orbit and lag behind your target, or if you decrease speed you move to a lower orbit and overtake your target. It's very confusing to try and do in a simulator.
And the faster it goes the sooner it would have to turn around and start breaking to slow down enough to be captured and orbit the asteroid, so there's a question of fuel and efficiency and time and all that. Getting there faster requires more propellant, which increases mass, which requires more propellant to accelerate, etc..
And it's 300m/s relative to Vesta, but Vesta is orbiting at 18000m/s so Dawn's already going at close to that speed.
|