Engineers from Boeing and NASA have spent much of the last month running ground tests on a Starliner Reaction Control System (RCS) thruster to get a better idea of what went wrong during the active Starliner’s flight in early June, and they finally wrapped up this past week. In its latest update, Boeing said the teams were able to replicate the thrust degradation Starliner experienced and are now reviewing all the data. But the date of astronauts Butch Wilmore and Suni Williams’ return is still uncertain — NASA and Boeing said only that they’ll be making the trip “in the coming weeks.”

In the tests at the White Sands Test Facility in New Mexico, the teams simulated the conditions from Starliner’s recent flight, putting the control system thruster “through one of the most stressing launch-to-docking firing sequences with over 1,000 pulses to simulate CFT [Crew Flight Test] conditions,” according to Boeing. They also tested undocking and deorbit burn scenarios, which Starliner will experience on its way home. After collecting terabytes of data from those tests, the teams ran additional, more aggressive tests to “see if we could more closely simulate the higher thermal conditions the thrusters experienced in-flight,” said Dan Niedermaier, Boeing’s engineer for the thruster testing.

The engineers are in the process of doing “engine tear downs and inspections” NASA’s Commercial Crew Program manager, Steve Stich, said on Thursday. Following their analyses, NASA says there will be an Agency Flight Test Readiness Review to determine whether Starliner is in good shape to bring the astronauts back. NASA and Boeing said they will release more information in a conference in the coming days.

This article originally appeared on Engadget at https://www.engadget.com/boeing-and-nasa-engineers-have-wrapped-up-ground-tests-on-the-starliner-thruster-180027494.html?src=rss