For the first time, Blue Origin successfully fired up its BE-4 rocket engine, a crucial piece of hardware the company has been working on for the last six years. Blue Origin tweeted out a video today of the test, known as a “hot fire,” which was conducted at the company’s test facility in Texas. It’s a major stepping stone in the development of the engine, which is slated to play a key role in Blue Origin’s economic future.

The BE-4 is slated to play a key role in Blue Origin’s future

Without the BE-4, Blue Origin’s future rocket wouldn’t fly. Currently, the company is developing a new reusable orbital rocket, called New Glenn, which is meant to be powered by seven main BE-4 engines at its base. Together, the engines will create a total of 3.85 million pounds of thrust at liftoff, allowing New Glenn to loft 100,000 pounds of cargo to lower Earth Orbit. Blue Origin hopes to fly New Glenn for the first time before the end of the decade, and having working engines is critical for achieving that goal.

First hotfire of our BE-4 engine is a success #GradatimFerociter pic.twitter.com/xuotdzfDjF — Blue Origin (@blueorigin) October 19, 2017

But Blue Origin wants the BE-4 to do more than just power New Glenn. The company is hoping to offer the engine to another company, the United Launch Alliance, which is a creating a new rocket of its own called Vulcan. For the last decade, ULA has been relying on Russian-made rocket engines to power its main rocket, the Atlas V. But that has put the company into some political hot water following the Ukraine crisis, since ULA is a primary launch provider for US national security satellites. To solve this problem, ULA decided to create an entirely new rocket that relies on American-made engines instead, and Blue Origin’s BE-4 served as an attractive replacement. In 2014 both companies agreed to jointly fund the development of the BE-4, so that it could power the Vulcan someday.

Blue Origin wants the BE-4 to do more than just power New Glenn

However, the BE-4’s use in Vulcan hasn’t been a done deal. Blue Origin is a fairly new company, founded in 2000, and it has much less experience with making rocket engines than other seasoned manufacturers. While ULA has always maintained a strong partnership with Blue Origin, the launch provider has also been maintaining a partnership with manufacturer Aerojet Rocketdyne. The company, which made the Space Shuttle’s main engines, has been developing another engine called the AR-1, which could be used to power the Vulcan too. And Aerojet has been very vocal about its desire for the AR-1 to fly on the vehicle.

ULA has made it clear, though: the first choice for the Vulcan is the BE-4. But there’s been a lot of political pressure on ULA to choose the more experienced Aerojet. Plus, ULA wants to have the Vulcan ready for flight in 2019, so that it can continue launching satellites for the US military without any gaps in access to space. Both Blue Origin and Aerojet Rocketdyne say their engines will be ready by then, but ULA has been keeping Aerojet around as a bit of a backup just in case the BE-4’s development doesn’t work out.

And Blue Origin has experienced a few hiccups along the way. In May, the company said it had lost some key hardware of the engine in a testing accident. The company has seemingly recovered from the incident, and Blue Origin seems to be farther along in the BE-4’s development than Aerojet Rocketdyne is with the AR-1. Plus, Blue Origin’s potential customer seems to be very pleased.