British scientists have been given the green light to begin the development of the most advanced ion engines ever to be used in space travel history. Set for launch in 2013, the European/Japanese BepiColombo mission to Mercury will be propelled to the Solar System’s innermost planet by advanced ion engines, with an efficiency equivalent to 17.8 million miles per gallon. This is one very cheap spaceship to fly!
We are currently being dazzled and amazed at the sheer detail of the images being transmitted by NASA’s MESSENGER mission flyby of the tiny planet Mercury. While we watch and wait for MESSENGER to eventually establish an orbit (insertion should occur in the spring of 2011), UK scientists, working with the ESA and Astrium (Europe’s largest space contractor), are hard at work designing the engines for the next big mission to the inner Solar System: BepiColombo. The mission consists of two orbiters: the Mercury Planetary Orbiter (MPO), to carry out mapping tasks over the planet, and the Mercury Magnetospheric Orbiter (MMO), to characterize the planets mysterious magnetosphere. The two craft will travel as one for the 6 year journey to Mercury, but separate at orbital insertion.
Although BepiColombo will use the gravitational pull of the Moon, Earth, Venus and then Mercury to actually get it to its destination, a large amount of energy is required to slow the craft down, countering the Sun’s gravity. Without an engine to thrust against BepiColombo‘s decent into the huge gravitational pull of the Sun, the mission would be doomed to overshoot Mercury and fall to a fiery end. This is where the ion engines come in.
Ion engines have been used in space missions before (such as the SMART-1 mission to the Moon in 2003), but the new generation engines currently undergoing development for the next Mercury mission will be far more efficient while providing sufficient thrust. Better efficiency means less fuel. Less fuel means less mass and volume, saving on launch cost and allowing more room for scientific instrumentation.
Ion engines work by channeling electrically charged particles (ions) through an electric field. Doing this accelerates the ions to high velocities. Each particle has a mass (albeit tiny), so each particle also carries a momentum when fired from the engine. Shoot enough particles out of the engine and you produce a thrust the spacecraft can use to accelerate or (in the case of BepiColombo) slow down. Ion engines do have a drawback. Although they are fuel efficient, the thrust can be small, so missions can take longer to complete; time must be allowed for the long-term thrust to have an effect on the velocity of the spacecraft. However, this shortfall for ion propulsion won’t deter space scientists from using this new technology, as the pros definitely outweigh the cons.
So, we can nowÂ look forward toÂ over a decadeÂ of exploration of MercuryÂ by MESSENGER and BepiColombo, one of the most uncharted and mysterious planets to orbit the Sun.