The European Space Agency’s test-fire of Ariane 6’s Vulcain 2.1 engine will start at 3:30PM ET, and will run for the full 470 seconds of the first stage of a real launch.

As Space notes, the Ariane 6 replaces the Ariane 5, which had a 27-year stint before going to pasture. Its first launch is planned for 2024 following years of delays.

The ESA livestream starts at 3PM ET.