The UK’s new National Space Propulsion Facility has been declared open. ESA oversaw the design, assembly and commissioning of the facility – equipped to test-fire the most powerful classes of rocket engines used aboard spacecraft – which will now be managed by the UK Government’s Science and Technology Facilities Council. But it takes clever engineering to allow the sustained firing of rocket engines into a sealed-off chamber that is simulating space. Powerful mechanical pumps operate continuously to maintain vacuum conditions. They remove the hot, supersonic exhaust plume from the rocket engine after it is diffused and cooled. This prevents it venting into the surrounding atmospherein a noisy, explosive manner.