Elon Musk’s SpaceX completed two test firings of the engines on its Starship 20 prototype on Thursday, as the company prepares for the rocket’s first orbital launch while the Federal Aviation Administration reviews its license request.

SpaceX installed a Raptor vacuum engine – essentially a version of the engine that is optimized for use in space – and fired it up for the first time while connected to a Starship rocket. The rocket at the company’s facility in southern Texas was held down during the test in a process known as a static fire. The engine fired for just a few seconds.

Later the same evening, SpaceX performed a second short static fire test. This time it used two engines: a standard or “sea level optimized” Raptor engine, and the vacuum engine.

Musk, in a series of tweets, explained that SpaceX continues to work on improving its Raptor engines. He said that Raptor is “currently at ~270 bar, but working on upgrades to get it over 300 bar.” Musk referenced the amount of chamber pressure within the engine, which effectively measures its performance.

Starship is the massive, next-generation rocket SpaceX is developing to launch cargo and people on missions to the moon and Mars. The company is testing prototypes at a facility in southern Texas and has flown multiple short test flights.

SpaceX wants Starship to be fully reusable, with both the rocket and its booster capable of landing after a launch to be recovered for future flights. SpaceX’s Falcon 9 rockets are partially reusable. The company can regularly land and re-launch the boosters but not the upper portion, or stage, of the rocket.

Earlier this week, Musk emphasized that “full & rapid reusability is the holy grail of orbital rocketry.” He was responding to a report that small rocket builder Rocket Lab is making advancements in recovering and reusing its Electron vehicles.

SpaceX’s next major step in testing Starship is launching to orbit. First, the company needs a launch license from the FAA for the mission.

The FAA is performing an environmental assessment of SpaceX’s facilities and operations in Boca Chica, Texas. Earlier this week, it held two public virtual hearings for members of the public to give feedback on the process. SpaceX has rapidly expanded its facility, which it calls Starbase, since development work on Starship began in earnest in early 2019.

The public hearings featured a wide dichotomy of testimonies, with 120 speakers in total. Commenters included those expressing whole-hearted support of Musk and the Starship project, with many calling in from out of state. Criticism came from representatives of local environmental groups.

Less than half of the commenters stated that they lived locally near SpaceX’s facilities. The final comment of the first hearing came from Brownsville city commissioner Jessica Tetreau, who said she has been working with SpaceX for the last 10 years and noted the company employs more than 2,000 people in the region.

“I don’t just ask you, I beg you to give them that permit. There are so many people here in the Brownsville area who have benefited from this project coming to our area,” Tetreau said.

The FAA is at step four of eight in its review.

It will evaluate public comments on its draft assessment, incorporate the feedback into its assessment and publish the final assessment. The FAA will then decide whether to issue a “finding of no significant impact” (FONSI) or give notice that it will begin a more in-depth review, known as an environmental impact statement (EIS). The latter would put any further Starship launches on hold until the review is complete.

SpaceX’s Starship proposal to the FAA includes up to 20 suborbital launches per year and up to 5 orbital launches per year.

Morgan Stanley, after CNBC reported SpaceX has reached a $100 billion valuation, found in a survey of institutional investors and industry experts that Musk’s space company is expected to become even more valuable than Tesla. Musk’s automaker currently commands a market value more than eight times higher than SpaceX’s valuation.

“Investors are beginning to appreciate the potentially wide-ranging use-cases for SpaceX’s reusable launch architecture across communications, transportation, earth observation and other space-related domains,” Morgan Stanley analyst Adam Jonas wrote in a note on Tuesday.