A solar powered lunar tug concept using two VASIMR engines. (Ad Astra Photo)

What is Plasma Rocket Engine that Takes 39 Days to Reach Mars?

NASA has zeroed in on the Ad Astra Rocket Company for its future space rocket engine that can shorten the travel to Mars from 9 months to 39 days, with its new revolutionary plasma rocket engine.

Franklin Chang-Diaz, CEO of the Ad Astra Rocket Company from Texas, says,”This is like no other rocket that you may have seen in the past. It is a plasma rocket. The Vasimr (Variable Specific Impulse Magnetoplasma Rocket) rocket is not used for launching things. It is used for things already there, which we call ‘in space propulsion'”.

In a Vasimr engine, gas such as argon, xenon, or hydrogen is injected into a tube surrounded by a magnet and a series of two radio wave (RF) couplers, which turn cold gas into superheated plasma. The rocket’s magnetic nozzle then converts the plasma thermal motion into a directed jet giving it the powerful thrust to propel the engine at extreme speeds.

NASA has offered a grant of $10 million to the Ad Astra Rocket Company as part of its 12 Next Space Technologies for Exploration Partnerships (NextStep) programme to make the Vasimr engine “into its technology readiness level (TRL) greater than 5 — a step closer to space flight,” said the company in a statement.

Ad Astra claims that the plasma rocket engine can save thousands of gallons of rocket fuel amounting to around $20 million every year.

NASA has been scouting for engines, launching vehicles and other paraphernalia for its much-touted 2022 manned mission to Mars as part of the Next Space Technologies for Exploration Partnerships (NextSTEP).

Under the program, three companies — Ad Astra Rocket, Aeroject Rocketdyne and MSNW LLC — have been given grant for further development of rocket engines with outputs of 50kW to 300kW, a big jump from its current 5kW capacity engines.

Ad Astra hopes to put its Vasimr for a 100-hour functional test having completed 10,000 rounds of short firing sequences.

While the Orion spacecraft is already under improvements to make it capable to transport humans to Mars, Vasimr can enhance the mission capability by shortening the period to reach Mars and return, if design permits.

How Plasma Engine Works?

Ad Astra's plasma engine

Ad Astra’s plasma engine

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) engine turns gas such as argon, xenon, or hydrogen in a tube surrounded by a magnet and two radio wave (RF) couplers to superheat plasma that is converted by the rocket’s magnetic nozzle into a jet thrust.

While the first RF coupler is a helicon section that can ionize gas by launching helical waves. Helicon couplers are a common method of generating plasma.

After the helicon section, the gas is now “cold plasma”, though its temperature is greater than the surface of the Sun (5800 K). The plasma is a mixture of electrons and ions (the atoms they were stripped from). The newly formed electrons and ions carry charge and may then be contained by a magnetic field shielding the rocket core from the plasma.

The second coupler, called the Ion Cyclotron Heating (ICH) section, is a technique used in fusion experiments to heat plasma to temperatures of those in the Sun’s core (10 million K). The ICH waves push only on the ions as they orbit around the magnetic field lines resulting in accelerated motion and higher temperature, according to the Ad Astra.

Thermal motion of ions around the magnetic field lines is mostly perpendicular to the rocket’s direction of travel and must be converted into directed flow to produce thrust. The rocket uses a magnetic nozzle to convert the ions orbital motion into useful linear momentum resulting in ion speeds of 180,000 km/hr (112,000 mph).

The VASIMR technology is highly scalable, meaning that higher power versions can be easily designed, making human missions powered by electric propulsion a reality, says the company.

It is currently pondering two ower sources — solar and nuclear. A VASIMR propelled, nuclear-electric powered spacecraft promises to be the fastest possible option to make human missions a reality, says the company.

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