The first VASIMR experiment was conducted at MIT in 1983 on their magnetic mirror device plasma device, and in 1998 ASPL created the first VASIMR rocket, the VX-10. By 2005 the ASPL had created the VX-50, which was capable of up to 50kW of plasma discharge. So, what’s so significant about this design?
MARS IN 39 DAYS:
One of our most current missions to Mars is the Curiosity Rover, it used the current standard Atlas V chemical rocket as a launch vehicle. Curiosity traveled to Mars with the momentum remaining from the launch and the on-board cruise stage, a miniature propulsion system made up of eight thrusters buring hydrazine fuel. Using this method, the Curiosity Rover took 8 months and 11 days to land on Mars. This is because current chemical rockets and propulsion systems require large amounts of fuel and have a static rate of propulsion.
However, the design of VASIMR allows for continuous generation of propulsion. In other words (if it had a infinite supply of fuel and it didn’t fail mechanically) it could theoretically keep accelerating to near the speed of light.
Moreover, this could allow us to each Mars in a mere 39 days. The variables used to determine a 39 day trip included a engine operating at 60% efficiency and a required power of 200MW. It would take the rocket a total of approximately 18 days to reach full velocity, it would travel at that speed for roughly five days before it began to slow back down, finally reaching Mars another 16 days later. A 200MW engine would be able to make a round trip to Mars with a 600 metric tonne payload in approximately five months (cutting several months off the current travel time).
Currently the VASIMR engines are operating over 60% efficiency; however, we have hit a wall on how to power the unit while in space. To achieve the amounts of power required for such a powerful engine, we would need to design some form of nuclear reactor, fusion reactor, or matter-antimatter reactor as a supply of power in space. Theoretically, you could use large solar panels as well; however, the weight for such panels would pose an issue at launch.
HOW VASIMR WORKS:
VASIMR utilizes gasses such as Argon, Hydrogen, or Xenon as a propellent; however, the gas is not combusted directly as it would be with chemical rockets. First, the gas is injected into a tube, the interior of which is lined with superconducting magnets. The tube itself is surrounded by two radio wave couplers. The Helicon Coupler is designed to convert the gas into plasma by knocking a electron lose from each gas atom. Once the gas has passed through the helicon section it is known as “cold plasma” even though its temperature is approximately 5800 Kelvin (this is just slightly hotter than the surface of the Sun). The Ion Cyclotron Heating coupler uses a technique borrowed from fusion experiments to heat the plasma upwards of 10 million Kelvin, comparable to the core of our Sun.
Using a magnetic nozzle VASIMR can convert the plasma ions orbital motion into a useful linear motion that results in ion speeds of up to 180,000 km/h, this gives VASIMR an effective Specific Impulse of upwards of 18,000s. Current liquid and solid rockets and propulsion systems have a maximum S.I. of 500s, this means VASIMR has the potential to generate exponentially higher cruising speeds.
TESTING VASIMR ON THE SPACE STATION:
In 2008, NASA and Ad Astra signed a deal to test a VASIMR platform on the I.S.S.. Testing VASIMR on the I.S.S. will provide extremely valuable information because the station is in Low Earth Orbit, and is subjected to fairly high levels of atmospheric drag, this requires periodic altitude boosts which will be preformed by VASIMR.
The current technology for altitude correction on the I.S.S. is standard chemical rockets. If VASIMR proves to be up to the job, it would mean that we could keep the I.S.S in a stable orbit for 1/20th of the current cost, effectively cutting $210 million of chemical rocket fuel from the NASA budget. Currently, NASA is expecting to launch the VF-200 to the I.S.S. at some point in 2015; however, because the I.S.S does not have the 200kW needed to operate the VF-200, they will also be sending a battery booster system, which will be trickle charged from the I.S.S. power supply, and will allow for 15 minute pulses of thrust.
A few people have been skeptical towards Ad Astra’s claims of being able to travel to Mars in 39 days. A lot of this appears to arise because people think the 39 day journey claim is using the current VX-200 engine design; however, this is incorrect. The 39 day journey uses a theorized 200MW engine, not the current 200kW engine we have.
This difference in engines also touches on the other bit of controversy that people have been holding onto–VASIMR does not produce enough thrust to escape the Earth’s gravity. This is not a design flaw, but the intended method for the engine to run. Since ion engines work best in a vacuum, the VASIMR engine is suited for space travel only, any space craft the engine was adapted to would either need to be built in space, or would have to reach space via chemical rocket. This of course does not mean the project is a failure, in fact the notion that NASA is planning to use VASIMR on the space station instead of the HiPEP system NASA had funded 5 years before signing a deal with Ad Astra shows NASA is more than confident with the VASIMR engine.