Boeing's Starliner spacecraft, which recently carried astronauts Butch Wilmore and Suni Williams to the International Space Station (ISS), will not be ready to begin operational crew missions for another year, following ongoing problems with its propulsion system. The unexpected issues have extended the astronauts' stay in space, currently at 51 days, as engineers work to resolve the critical concerns with the spacecraft.

The first problem encountered by the Starliner involved the overheating of its reaction control thrusters during its approach to the ISS on June 6. Some of the thrusters shut off, causing a delay in the mission. Additionally, there have been helium leaks discovered in the craft's propulsion system, possibly related to the initial thruster malfunction.

Despite the setbacks, NASA and Boeing managers have affirmed their intention to bring Wilmore and Williams back to Earth aboard the Starliner spacecraft. In recent weeks, ground teams have conducted the testing of a thruster on a test stand in White Sands, New Mexico, to measure its performance. This weekend, Boeing and NASA plan to evaluate the performance of the spacecraft's thrusters while docked at the ISS.

Steve Stich, manager of NASA's commercial crew program, stated that while backup plans have been considered to return the astronauts on a SpaceX Crew Dragon spacecraft, their primary focus remains on completing the mission with the Starliner. Stich emphasized that Starliner was specifically designed to have a crew onboard and highlighted the importance of finishing the mission as planned.

The Starliner initially launched from Cape Canaveral Space Force Station in Florida on June 5, making Wilmore and Williams the first astronauts to fly into space using Boeing's commercial crew capsule. The current test flight aims to pave the way for future operational flights, allowing the rotation of four-person crews to and from the ISS. Once fully certified by NASA, the Starliner will provide an additional option for human-rated spaceships alongside SpaceX's Crew Dragon, which has been transporting astronauts since 2020.

To ensure the crew's safety and gain confidence in the Starliner's performance, NASA has extended the duration of the test flight. Engineers have been conducting extensive tests and data analysis to understand the root causes of the thruster overheating and helium leaks. These issues primarily arise in the service module of the Starliner, which is jettisoned and burns up in the atmosphere during reentry, leaving the crew module with the astronauts to parachute land on Earth.

Significant progress has been made in recent test-firings of a Starliner thruster on the ground. Engineers observed thrust degradation similar to what was experienced in orbit, indicating that the ground test was a good representation of the spacecraft's behavior. During inspections, a bulging Teflon seal in an oxidizer valve was discovered, which could restrict the flow of propellant. Further evaluation is underway to determine if the Teflon seal can withstand the remaining stages of the mission.

While it is unclear when the astronauts will be able to return to Earth, NASA and Boeing are diligently working to ensure a safe journey home. The focus remains on rectifying the propulsion system issues and completing the Starliner mission in line with its original objectives.