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The testing vacuum chamber, containing the 50kW VASIMR. (NASA)

VASIMR: Still Hot

The future of rocket propulsion

Late in 2014, a radically different type of rocket propulsion is set to show up on the International Space station for a period of experimentation.

The technology is called the Variable Specific Impulse Magnetoplasma Rocket (VASIMR). It's a rocket engine that uses electricity to ionize a gas such as argon, xenon, or hydrogen. Ionizing means that an electron gets knocked off of each atom in the gas, creating a plasma, which then gets energized in another section of the engine by radio wave antennas. This superheats the plasma until it is 200 times hotter than the surface of the sun. The plasma shoots out the back of the rocket through a system of magnets that align it properly to create highly efficient thrust. Read more about it here.

While not able to provide the explosive power of a chemical rocket for getting loads off the launch pad, VASIMR can create a steady stream of thrust for days or weeks and continually accelerate a spaceship away from Earth. It still looks plenty explosive in this 2009 max-power test.

The company that created it, Ad Astra, was founded by 7-time space shuttle astronaut Franklin Chang Díaz. He claims that VASIMR could get astronauts to Mars in 39 days instead of the six-to-nine months needed with chemical rockets. Ad Astra is located in Webster, Texas, not far from NASA's Johnson Space Center. A VASIMR rocket on the ISS would have many uses, one of which would be to reboost the station to higher altitudes. With the looming retirement of the space shuttle, which used to handle that job, NASA likes the idea. Ad Astra claims that a VASIMR rocket could do this work for about 1/10th the current cost of $210 million a year. Other tasks that VASIMR could eventually handle include propulsion to enable satellite refueling, repair, and disposal, payload delivery to the moon, Earth departure stages for deep space probes, and various uses as a space tug for future vehicles in Earth orbit or beyond.

So how's the VASIMR going to get up there? Chang Díaz writes to us that he never intended for it to actually go to the station on the shuttle. "I knew that program would soon end," he says. "We always planned to go on one of the CRS vehicles, Falcon or Taurus II. We are still on that plan and do not have to down select the carrier until next year, so we are carefully watching the evolution of the CRS program." When the engine finally gets there, it will be the culmination of literally decades of work.

Chang Díaz is excited about the outlook for VASIMR. In March he signed his fourth support agreement with NASA to collaborate on research, analysis and development tasks on space-based cryogenic magnetic operations and electric propulsion systems. In particular, the support agreement means that Ad Astra will provide NASA with an assessment of VASIMR's high-power, low-thrust trajectories over a number of mission scenarios ranging from near Earth to deep space, while NASA will support Ad Astra's efforts to mature the design of their 200-kilowatt VF-200 demonstration engine planned for the ISS, including use of specialized NASA facilities and equipment for the testing.

Chang Díaz emailed us from the country of his birth, Costa Rica, where Ad Astra has a second location, and said he was headed to Europe. "There is a strong current of interest in VASIMR developing in the old world as well, mainly Germany and Italy," he says.

Here's a neat video of a VASIMR payload delivery to the moon, which shows the advantages of the technology over traditional, chemical rockets.


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