British-built spacecraft BepiColombo to blast off to reach Mercury

A British-built spacecraft is set to blast off from Earth to map the surface of Mercury, the closest planet to the sun in our solar system.

BepiColombo, the European Space Agency’s (Esa) first mission to Mercury, will be the first spacecraft to use electrical ion thrusters to travel to another planet.

The mission will perform a comprehensive study of the smallest and innermost planet in the Solar System.

It will examine its magnetosphere, interior structure and surface.

The four-tonne spacecraft will be launched into orbit by Esa’s rocket Ariane 5 from the European spaceport at Kourou, French Guinea, on 20 October.

Its arrival on Mercury is planned for December 2025 after 5.2bn mile (8.5bn km) journey.

Once landed, the spacecraft will deploy the Mercury Planetary Orbiter (MPO) built by satellite-maker Airbus Space and Defence at its assembly centre in Stevenage, Herts, to study the planet’s surface and composition.

The second probe, the Japanese Mercury Magnetospheric Orbiter (MMO), constructed in Japan, is set to look at the electromagnetic environment surrounding the planet.

BepiColombo carries a futuristic ion electric propulsion drive, built in the UK, unlike any other interplanetary spacecraft in history.

Four T6 ion engines supplied by British defence and technology company QinetiQ are fitted to the craft's power unit, the Mercury Transfer Module (MTM).

They work by "ionising" inert xenon gas - knocking an electron off the gas atoms to give them a positive charge.

The resulting "plasma" is attracted by electrostatic forces to a grid with an opposite negative charge and fired out of the thruster at 90,000mph.Although the force produced is tiny, it can be maintained with high efficiency over a long period of time.

Dr Jerry Bolter, project manager at Airbus Defence and Space in Stevenage, where the MTM was assembled, said: "We recognised very early on that for BepiColumbo to do what we wanted it to do and get from here to Mercury we needed to have a very efficient propulsion system.

“If we relied on chemical propulsion then we'd need 17 tonnes of propellant.

"The ion drive needs just 581 kilograms of propellant and does the equivalent of 17.8 million miles to the gallon."

He added that the drive unit was "very complicated" involving a lot of intricate computer-controlled electronics to control fuel rates and pressure.

Two spacecraft have visited Mercury – Nasa’s Mariner 10 flew by in 1974 and 1975, and Messenger, launched in 2004, orbited the planet over 4,000 times before exhausting its fuel and crashing into the planet’s surface in 2015.