[Thaeris]

This is on Page 40 of the latest issue of PopSci:

FAST LANE TO MARS:
     A new ion engine could slice the time it takes to get to the Red Planet

Six Europeans recently wrapped up 105 days in an isolation chamber with no TV, no showers, and lots of pre-cooked food, to test the stresses of a journey to Mars. Real Marstronauts might not have to suffer through all that. A new ion engine, which shoots charged particles to create thrust, could get them o the Red Planet in just 39 days.

In theory, there's no better way of getting between planets than an ion engine. The engine in NASA's asteroid probe Dawn fires electrons at xenon gas to convert those atoms into positive ions, which fall onto a positively charged screen that repels the ions out of the engine.

The problem is power. For example, Dawn runs on three ion engines, each of which puts out a steady, but measly, one-third of an ounce of thrust. (Each engine on a Boeing 777 churns out about 100,000 pounds of thrust.) This is great for long, unmanned missions - it took about 16 months to propel the probe to Mars - but it's not ideal for humans looking to spend as little time in transit as possible. NASA is retooling its engine for triple the thrust, which could get a probe to Mars faster, but it's still too slow for a large spaceship heavy with crew and gear. If a little more thrust is good, a lot more is better. The Texas-based aerospace company Ad Astra's VASIMR engine creates a thicker ion stream by shooting radio waves, rather than electrons, at argon gas. Then, the engine's superconducting magnets fling the ions to generate 50 times as much thrust.

In July the company demonstrated the ion-making step, and next month it will fire up the 200-kilowatt machine at full power - almost strong enough that four such engines could drive a manned moon voyage. Running on solar power, that trip would take six months, but Ad Astra has a plan for speeding the engine up for Mars: nukes. Unlike NASA's current engine designs, which cannot handle megawatts of power, Ad Astra could scale up VASIMR to run on a 200-megawatt nuclear reactor. That, says Tim Glover, the company's director of development, gives VASIMR an edge: "Would you rather pull a trailer with a couple of bicycles or with a car?"

-Carina Storrs for Popular Science Magazine

Popular Science is by no means the most authoritative source, but I thought it was a fairly intriguing article. She (Storrs) could work on being just a bit more clear and precise in her writing, though...

[MR_T3D]

i recall reading something on such engines/watching a tube video of a test-fire.
definitely makes the prospect of journey to mars seem more reasonable, but i think the key would be picking people whom could tolerate the long journey, unlike certain TV 

[General Battuta]

I posted a link to this in the '50 years of space exploration' thread a couple days back.

[Liberator]

First promising news for space travel in months.  Except how are you going to talk the eco/anti-nuke whackjobs that you need a reactor that big in orbit.

[Scotty]

OMG!  ITZ TEH NUKEZ, but now deyz IN SPACE!

[General Battuta]

First promising news for space travel in months.  Except how are you going to talk the eco/anti-nuke whackjobs that you need a reactor that big in orbit.

Ignore them?

Worked for Cassini's little pile.

[FUBAR-BDHR]

Didn't we already use such an engine for a survey of Mercury? 

[Kosh]

First promising news for space travel in months.  Except how are you going to talk the eco/anti-nuke whackjobs that you need a reactor that big in orbit.

Ignore them?

Worked for Cassini's little pile.

Cassini didn't have an actual reactor, it iwas a radio thermal generator. And yeah, there was a huge uproar about that when it was being launched.

[headdie]

how much does a fission reactor of the size needed weigh? and what is the current launch capacity?

[Kosh]

The VASIMIR isn't capable of putting anything into orbit.

[Liberator]

Well, you wouldn't haul a full assembled reactor into orbit, I wouldn't think.

To properly construct a ship capable of using the size drives and reactors they're talking about you'd have to have an all new space station crewed by a lot more than 3 people to build it.

I mean even if it can make the trip to Mars in 40 days or whatever that's 80 days both ways plus the time in orbit while to do the science and wait for the return window to open up.  So you're gonna need a ship with life support capable of keeping the crew alive that long.  Which is a complicated prospect.  Some of the stuff they've been cooking up long this line looks overly complex, which as a wise Scottish engineer once said, "The more they tech up the plumbing, the easier it is to stop up the drain."  Or more correctly to quote Kelly Johnson, "Keep it simple, stupid".

[General Battuta]

First promising news for space travel in months.  Except how are you going to talk the eco/anti-nuke whackjobs that you need a reactor that big in orbit.

Ignore them?

Worked for Cassini's little pile.

Cassini didn't have an actual reactor, it iwas a radio thermal generator. And yeah, there was a huge uproar about that when it was being launched.

That's what I said.

Thus 'little pile'.

Thus 'ignore them'.