Ion engines are light, efficient means of propulsion, and recent NASA missions have proven that they’re capable of getting spacecraft to other planets. Are they going to be the key to landing the first human explorers on Mars?

Getting a spacecraft out of Earth’s atmosphere into orbit and beyond is a daunting task. Hoisting mass into space requires an immense amount of energy and fuel, and refilling the tank at a rest stop isn’t exactly an option. NASA plans to power a future Mars voyage with technology that can run clean and won’t burden the spacecraft with any more weight than necessary. When it costs ten thousand dollars to get every pound of payload into orbit, you need to pack light.

There’s no escaping the need for chemical propulsion – rocket fuel – in giving spacecraft enough thrust to counter the pull of Earth’s gravity and get into space.  But once a Mars mission leaves the ground, it’s going to need a different, more efficient, propulsion system to carry it along the 34-million-mile, months-long journey to the red planet. That’s where ion propulsion systems come in.

Plasma-powered spacecraft

An ion propulsion engine works by accelerating charged plasma ions via electrostatic or electromagnetic force. When ejected from the engine, the acceleration of the ions gives the ship a reciprocal push in the opposite direction. An ion thruster doesn’t create very much thrust: NASA’s Deep Space 1, the first spacecraft to use an ion engine, was only able to produce thrust equal to the weight of a piece of paper. In space, where there are no air molecules to impede a spacecraft’s movement, that small amount of thrust can create significant slow acceleration.

NASA has been conducting research on ion propulsion systems for years in order to improve their efficiency while working towards their use in crewed missions. The Dawn spacecraft, currently in orbit around the dwarf planet Ceres in the asteroid belt beyond Mars, is also powered by an ion propulsion system, both for acceleration and for course and position adjustments.

Improvements in thrust and efficiency

In December 2009, a five-year test of NASA’s Evolutionary Xenon Thruster (NEXT) project was completed at the Glenn Research Center in Ohio. After five years of continuous operation, the engine showed no signs of degradation, and proved itself three times as powerful as its predecessors on the Dawn and Deep Space missions.

NEXT engine in operation

In a press release in 2013, NASA reported:

“During the endurance test performed in a high vacuum test chamber at Glenn, the engine consumed about 1,918 pounds (870 kilograms) of xenon propellant, providing an amount of total impulse that would take more than 22,000 (10,000 kilograms) of conventional rocket propellant for comparable applications.”

With excellent performance at one-tenth the weight of conventional fuels, there’s little wonder that NASA is banking heavily on ion propulsion for its future exploration. While a crewed mission to Mars is still a vague future possibility, NASA plans to use the NEXT engine in an upcoming Discovery Program mission, which would launch in 2021. Candidates for that mission include a trip to Saturn’s moon Enceladus, or to the tiny Martian moons Phobos and Deimos. One small step for man into the red sands of Mars can’t be far behind.

Image credits NASA via Wikimedia commons

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