Mercury Transfer Module electric propulsion thruster steering test
Video showing a test of the mechanisms steering the four solar electric propulsion thrusters on BepiColombo's Mercury Transfer Module (MTM), speeded up by 20 times.
The module will use a combination of electric propulsion and multiple gravity assists at Earth, Venus and Mercury to carry BepiColombo's two scientific orbiters – ESA's Mercury Planetary Orbiter (MPO) and Japan's Mercury Magnetospheric Orbiter (MMO) – to the innermost planet in our Solar System.
The test is designed to demonstrate that the mechanisms can reach their full steering range. The thruster mechanisms control the steering of the composite spacecraft stack (MTM, MPO and MMO) during the long thrust arcs of the 7.2 year cruise to Mercury and as such are used for navigation, attitude control, and reaction wheel off-loading. Together with the onboard software, the mechanisms will update the direction of the thrust vector every five minutes relative to the spacecraft's evolving centre of gravity. The thrusters will be fired for several months at a time between the gravity assist flybys. This particular test was conducted in April 2017, before the spacecraft was put into the composite stack configuration. The same test will be repeated again later in the year to verify performance after the stack level vibration test campaign.