Future Mars outposts or colonies may seem more distant than ever with NASA's exploration plans in flux, but the rocket technology that could someday propel a human mission to the red planet in as little as 40 days may already exist.

A company founded by former NASA astronaut Franklin Chang-Diaz has been developing a new rocket engine that draws upon electric power and magnetic fields to channel superheated plasma out the back. That stream of plasma generates steady, efficient thrust that uses low amounts of propellant and builds up speed over time.

"People have known for a long time, even back in the '50s, that electric propulsion would be needed for serious exploration of Mars," said Tim Glover, director of development at the Ad Astra Rocket Company.

The rocket technology could drastically cut down the amount of time a spacecraft needs to send astronauts onMars missions. Instead of half a year, a spacecraft could make the trip in just over a month using the engine and a large enough power source, according to an Ad Astra mission study.

NASA's recent course change has freed up some funding for new propulsion technologies. And the U.S. space agency has not lost sight of the red planet, NASA administrator Charles Bolden told Congress as he presented a new budget last month.

"While we cannot provide a date certain for the first human visit, with Mars as a key long-term destination we can identify missing capabilities needed for such a mission and use this to help define many of the goals for our emerging technology development," Bolden said.

Familiar chemical rockets that burn solid or liquid chemical propellants won't get humans to Mars fast because they would require too much propellant. They can create a huge boost for several minutes at the cost of huge inefficiency — not unlike a speed demon with poor gas mileage.