Elon Musk and SpaceX grab most of the headlines for private sector space projects, so it's easy to forget about the other well-known tech entrepreneur with an interest in commercial space ventures. That entrepreneur is Amazon's Jeff Bezos, and his aerospace/spaceflight company Blue Origin just successfully test fired its BE-4 rocket engine in West Texas.

The successful hot firing test is not only good news for Blue Origin, but also for United Launch Alliance (ULA) who signed an agreement with Blue Origin back in 2014. Under that agreement, the BE-4 will be used as a replacement for the Russian made RD-180 rocket as part of an upgraded Atlas V launch vehicle named Vulcan.

First hotfire of our BE-4 engine is a success. Huge kudos to the whole @BlueOrigin team for this important step! #GradatimFerociter pic.twitter.com/0gk6k6WuPx — Jeff Bezos (@JeffBezos) October 19, 2017

The Vulcan heavy-payload launch vehicle isn't expected to undertake its first launch until 2019, but ULA needed to be reassured the BE-4 engine was making progress. The alternative, according to GeekWire, is the AR1 engine offered by Aerojet Rocketdyne. However, with the BE-4 successful test fire that switch to AR1 now seems unlikely.

Beyond the agreement with ULA and Vulcan launch, Blue Origin is focused on a three-stage orbital launch vehicle called New Glenn, which will use seven BE-4 engines giving the launch vehicle a total of 3.9-million pounds of thrust (each BE-4 engine achieves 550,000 pounds of thrust). Once operational, New Glenn will be used for commercial satellite launches, but Bezos is also eyeing military contracts and NASA missions.

While Elon Musk and Jeff Bezos don't compete on Earth, they are set to be fierce rivals in space.