WASHINGTON — The European Space Agency will ask its 22 member states next month to fund an additional two to eight Prometheus reusable engines so that the agency can further the engine’s development.

ESA, with prime contractor ArianeGroup, has two Prometheus engines being built today, leveraging funds granted at its 2016 ministerial, plus earlier work supported by the French Space Agency CNES.

Jérôme Breteau, ESA’s head of future space transportation, said Oct. 21 at the 70th International Astronautical Congress here that those two engines are on track for test firings in late 2020 at the German Space Agency DLR’s Lampoldshausen facility. ESA will continue engine tests into 2021, but what follows “is the subject of our proposal to the Space19+ ministerial,” he said.

ESA’s tri-annual ministerial conferences are where the agency and its members allocate funds for future space programs. ESA is seeking 12.5 billion euros ($13.9 billion) at its next ministerial, dubbed Space19+, Nov. 27 -28 in Seville, Spain.

Breteau said ESA needs to know the outcome of the ministerial before it can lay out the next steps for Prometheus. The agency has “very ambitious” plans for the liquid-oxygen and methane engine, he said.

ESA’s goal with Prometheus is to manufacture the engine for 1 million euros ($1.1 million) each — a tenth the price of the Vulcain engine used on the first stage of Europe’s Ariane 5 rocket. Prometheus is also designed to be reusable.

Breteau said Lampoldshausen’s hydrogen engine test bench, used for Ariane 6’s Vulcain 2.1 engine, will need upgrades to support the methane needed for Prometheus.

Breteau said Prometheus is so far in line with its cost target and its performance target of 1,000 kilonewtons in thrust. He said it is difficult to have a set mass target for Prometheus because that requires knowing what vehicle the engine will support.

Work on Prometheus has been done with the expectation that it would be used on a launch vehicle in the 2030s, but ArianeGroup has mused using it on the Ariane 6 rocket, which debuts in 2020.

Breteau wouldn’t go so far as to name a launcher that might use Prometheus.

“System engineering on the target launcher configuration is ongoing,” he said. ESA has what Breteau described as “more than a notional idea” of how to cluster Prometheus engines together on a launcher, a detail he said gives an “idea of the maturity of the system activities.”