Khoren Sahagian

Khoren Sahagian
Materials Scientist

Editorial August 2012

Rocket propulsion has progressed in the over 40 years of space travel. On October 4th 1957 the Soviet Union launched the first artificial earth satellite. The feat was achieved using a 2 stage R-7 ICBM rocket weighing 170 tons. The solid rocket fuel needed to be held at cryogenic temperatures. Although today’s rockets are a lot more high tech most of the fundamental principles of propulsion still persist. Mainly the modern rocket typically utilizes solid rocket fuel. High altitudes are reached through multi-stage systems whereby the burned-out stage drops away relieving cumbersome mass from taxi of the final payload. Surprisingly the velocity with which space is traversed has not appreciably changed since the year 1962. This time of travel is arguably the biggest impedance to human exploration of the solar system. Second is that fact that once the rocket is ignited there is no turning it off; the fuel must be burned to completion. This is sort of suggestive of a one way trip. There is however a new generation of rocket propulsion beyond the horizon. The concept is named Variable Specific Impulse Magnetoplasma rocket or VASIMR.


The VASIMR is a plasma based propulsion system. Radio Frequency electric field ionizes the fuel into a plasma. Magnetic field then directs the hot accelerating gas out of the engine generating thrust. Even though the PTS and Plasmatreat organization utilize plasma for a different purpose, there are a couple of parallels that can be drawn. For starters one may envision mission specific gas mixture selection balancing metrics such as thrust, efficiency, and weight. Furthermore a plasma process may start or stop, its intensity regulated, and the gases employed are usually prevalent throughout the solar system. Efficient plasma impulse is ideal in the vacuum of space. There is great appeal in possibly being able to refuel a plasma propulsion system using gases present in the atmosphere of a destination such as mars. To put it in another perspective contemporary space shuttles exhausts propellant at about 6,000 m/s. An RF plasma would potentially expel mass in the range of 30,000 – 300,000 m/s. Here on Earth plasma has enabled myriad industrial and technological possibilities. I will finally conclude with an appropriate adage, “to the moon and beyond.” I am excited to see the field of plasma opportunity expanding into the stars.

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15. August, 2012 20:56

Good analysis. I’m glad you mentioned that the velocity with which space is traversed has not appreciably changed since the year 1962. I would really like to see Moore’s law more rigorously applied to space travel.

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