Conventional rockets are great and have gotten us far, but they have their limitations. These rockets also work on the basis of thrust: The engine burns fuel, creating a high pressure gas that gets forced out of the rocket nozzle at high speed and the rocket gets propelled in the opposite direction [source: Brain]. Rocket fuel, however is very heavy and super-inefficient. It cannot provide enough power to get places fast. The rocket fuel is burned up in the effort to get off the earth and into orbit, and then the spaceship basically is forced to just coast [source: Verhovek].
A plasma rocket, on the other hand, uses a lot less fuel than these conventional engines – 100 million times less fuel, in fact [source: Science Alert]. It's so fuel-efficient that you can go from Earth's orbit to the moon's orbit with just about 30 gallons (113 liters) of gas [source: Charles]. Plasma rockets accelerate gradually and can reach a maximum speed of 34 miles (55 kilometers) per second over 23 days, which is four times faster than any chemical rocket [source: Verhovek]. Less time spent traveling means less risk of the ship experiencing mechanical failures and astronauts being exposed to solar radiation, bone loss and muscle atrophy. With VASIMR, propulsion will also theoretically be available throughout the entirety of the trip, meaning that changes in direction could be possible at any time.
To be realistic, at this point, travel to Mars in a short time is still a long way off. Reaching these types of extreme distances will require a lot of power. Most Hall thrusters and gridded ion engines run on about 5 kilowatts of power. To get to the levels of power you'd need to reach Mars in about 40 days, you'd need at least 200 times that amount [source: Walker]. The most viable source of energy to generate this amount of power while in outer space is nuclear power sources built into the engine. At this time, however, putting a nuclear power source on a rocket ship that we blast from earth into space poses too much threat of radiation exposure in the case of a crash.
So the power source to reach those distances remains a major challenge. Not to mention the uncertainty of how the human body would react to travelling 34 miles (54 kilometers) per second (as opposed to the 4.7 miles or 7.5 kilometers per second astronauts travel to get to lower earth orbit in conventional rockets) [sources: Verhovek, Northwestern University Qualitative Reasoning Group]. But in theory, given enough power, these engines have the capabilities of reaching Mars in about 40 days, a feat we wouldn't have dared dream possible just 50 years ago.
Author's Note: How Plasma Rockets Work
First I read "The Martian," and now I've written this article. I've never been so jazzed about Mars! I'm not sure I'd want to go there myself, but more power to the astronauts who may one day walk upon the red planet!
More Great Links
- Allain, Rhett. "What's So Special About Low Earth Orbit?" Wired. Sept. 15, 2015. (Aug. 25, 2016) http://www.wired.com/2015/09/whats-special-low-earth-orbit/
- Brain, Marshall. "How Rocket Engines Work." HowStuffWorks.com. April 1, 2000. (Aug. 25, 2016) https://science.howstuffworks.com/rocket.htm
- Charles, Christine. "The fourth state of matter – plasma." TEDx-Canberra. Nov. 3, 2014. (Aug 24, 2016) https://www.youtube.com/watch?v=n-17xqfF4FU
- Harris, Tom. "How Plasma Displays Work." HowStuffWorks.com March 19, 2002. (Sept. 9, 2016) https://electronics.howstuffworks.com/plasma-display.htm
- Nadis, Steve. "The Revolutionary Rocket That Could Shuttle Humans to Mars." Discover Magazine. April 18, 2014. (Aug. 24, 2016) http://discovermagazine.com/2014/may/12-rocketman
- NASA. "Overview of Hall Thrusters." (Aug. 30, 2016) http://www.grc.nasa.gov/WWW/hall/overview/overview.htm
- NASA. "Three Classes of Orbit." (Aug. 25, 2016) http://earthobservatory.nasa.gov/Features/OrbitsCatalog/page2.php
- Northwestern University Qualitative Reasoning Group. "How fast can conventional rockets go?" (Sept. 9, 2016) http://www.qrg.northwestern.edu/projects/vss/docs/propulsion/2-how-fast-conventional.html
- Science Alert. "This plasma engine could get humans to Mars on 100 million times less fuel." Oct. 28, 2015. (Aug. 25, 2016) http://www.sciencealert.com/this-plasma-engine-could-get-humans-to-mars-on-100-million-times-less-fuel
- St. Fleur, Nicholas. "A Close Encounter for Earth and Mars." New York Times. May 30, 2016. (Sept. 9, 2016) http://www.nytimes.com/2016/05/31/science/mars-earth-closest-approach.html?_r=0
- Verhovek, Sam Howe. "The 123,000 MPH Plasma Engine That Could Finally Take Astronauts to Mars." Popular Science. Oct. 13, 2010. (Aug. 24, 2016) http://www.popsci.com/technology/article/2010-10/123000-mph-plasma-engine-could-finally-take-astronauts-mars
- Walker, Mitchell. Associate Professor of Aerospace Engineering, Georgia Institute of Technology. Personal Interview. Aug. 25, 2016.
- Zyga, Lisa. "Plasma Rocket Could Travel to Mars in 39 Days." Phys.org. Oct. 6, 2009. (Aug. 24, 2016) http://phys.org/news/2009-10-plasma-rocket-mars-days.html