[Spaceships] Getting A Few Thousand Extra MPS

[hal]

Entering Space, Pg 190, gives a formula of

Departure Velocity squared = Max Velocity squared - Escape Velocity squared.

The idea being, to use a gravity assist with our sun, attaining a closest approach of 40,000 km of the sun with a fall from Jupiter allowing the craft to attain 600 km/s at 40,000 km at closest approach. The author points out that the max velocity one can attain is 10 km per second due to twice exhaust velocity of chemical rockets, a ship could leave with a final velocity of 110 k/s.

But, what if you can use a two stage rocket to accelerate towards the sun, separate at 40,000 km above the sun, and then use a mag sail away from the surface of the sun? The single stage vessel after separation would have 1/3 rd the original mass, gain free acceleration via mag sail, and perhaps gain more than the original +10 k/s boost given in Robert Zubrin's scenario?

Could the max bonus be equal to the average delta V gained at 40,000/149,597,871,000 AU and say 1AU? Not sure what the Max velocity is for a mag sail, but I'd guess it to be higher than 10 k/s of chemical exhaust velocity.

Addenda: Max velocity for a mag sail seems to be 375 m/s - making it useless while using a gravity assist or so it would appear.