Prometheus (rocket engine)

The Prometheus rocket engine is an ongoing European Space Agency (ESA) development effort begun in 2017 to create a reusable methane-fueled rocket engine for use on the Themis reusable rocket demonstrator, Ariane Next, the successor to Ariane 6, possibly a version of Ariane 6 itself, and the Maia reusable launch vehicle. Prometheus is a backronym from the original French project designation PROMETHEE, standing for "Precursor Reusable Oxygen Methane cost Effective propulsion System", and for the Titan Prometheus, from Greek mythology, creator of humanity, and god of fire, known for giving fire to humanity in defiance of the gods.

Source: Wikipedia — Prometheus (rocket engine) (CC BY-SA 4.0)