Actually, 39 days to get to mars, presumably 39 days to get back, two days to goof off...

Well, I thought it was funny.

(PhysOrg.com) -- Last Wednesday, the Ad Astra Rocket Company tested what is currently the most powerful plasma rocket in the world. As the Webster, Texas, company announced, the VASIMR VX-200 engine ran at 201 kilowatts in a vacuum chamber, passing the 200-kilowatt mark for the first time. The test also marks the first time that a small-scale prototype of the company's VASIMR (Variable Specific Impulse Magnetoplasma Rocket) rocket engine has been demonstrated at full power.

Oooh, wow! 200 kW works out to 268 HP (electric). That's a little less than the power of a late-model Beechcraft Bonanza, a single-engine light aircraft.

Dr. Bussard was hoping for multiple gigawatts. I worked out a single main engine of the space shuttle as just about 6 GW, based on the energy released from burning the hydrogen and oxygen at the average rate used on a launch.

Tom Ligon wrote:Oooh, wow! 200 kW works out to 268 HP (electric). That's a little less than the power of a late-model Beechcraft Bonanza, a single-engine light aircraft.

Dr. Bussard was hoping for multiple gigawatts. I worked out a single main engine of the space shuttle as just about 6 GW, based on the energy released from burning the hydrogen and oxygen at the average rate used on a launch.

(20 dy)*(200 kW)/(6 GW) = 1 min, so we are in the right ballpark, as far as the energy goes. (Though I am sweeping a lot of details swept under the rug,) It's OK for space, but don't try to use it to get off the ground.

I thought there were going to make a multiple magawatt version for longer distance traveling. The 200 kw version is only for keeping the station in orbit.

Just how much thrust can a VASMIR engine provide? See an example below.
In the example given, 190.5 m/s speed after one day of thrust would = ~685 km/hr

"VASIMR Thrust
A plasma drive like VASIMR can develop one newton of thrust per 100 kilowatts. One newton equals about 0.225 pounds. A one thousand ton Mars/Venus clipper with a 100 ton VCR generating 200 MWe will get about 450 pounds of thrust from a VASIMR drive. This will allow an acceleration of 0.0022 meters per second per second. In one hour the ship will speed up by 7.94 meters per second. In one day 190.5 m/s and in one week 1333 m/s or 1.33 kps. In four weeks 5.33 kps and in eight weeks 10.66 kps. Constant low thrust can lead to high speeds. VASIMR can be operated at higher power levels than electrostatic ion drives. "

A Polywell reactor- QED engine or Polywell reactor-VASMIR engine operating at similar efficiencies, but with ~ 6 GW of power, would in this example provide ~ 20,000 km/ hr speed after one day of thrust.

This is a lot less than I would guess, based on a vague recollection that ~ 2000 watts can generate ~ 1 pound of thrust in an ideal ion engine.
[EDIT]Perhaps a badly flawed memory. This link shows a Hall thruster with ~ 1 newton of thrust for ~ 20 kw of power. Still that is ~ 5 times more energy efficient than the number quoted for the VASMIR rocket above.

With ion engines all is hugely dependent on reaction mass flow. If the presumption is that the electrical power source requires almost no fuel mass compared to the reaction flow mass, you have the option of using reaction mass quickly to achieve high thrust for a short time (and low specific impulse or Isp), or low thrust for a long time (and high Isp).

Dr. Bussard tended to aim for short high-thrust burns at Isp in the range of a few thousand seconds for Mars trips, but stretch to very high Isp and anemic thrust for Saturn and beyond. Isp values in the low thousands of seconds are fairly typical of present ion engine designs.