[binarycoffee]

This is correct but incomplete: Vasimr may have a higher power density (be it power per thruster mass or per thruster volume) than ion thrusters but I am pretty sure it has lower power density than a Hall thruster, while being also much more complex.

The main (and not yet verified) claim of Vasimr compared to existing and proven tech like Hall thrusters is the ability to greatly vary the specific impulse.

[jandrese]

That's what the article claims. That you can run in a less efficient mode that produces more total thrust when you're climbing out of a gravity well, then switch to the lower thrust higher efficiency mode for the long haul.

[ethbro]

I thought one of the issues with Hall thrusters was that, in engineering-practical terms, getting enough total thrust out of them was impossible. Or would they scale effectively?