NASA's leadership has acknowledged the possibility of exploring alternatives to Boeing's Starliner spacecraft to bring back a pair of astronauts from the International Space Station (ISS). The Starliner has been in space for 36 days while NASA and Boeing conduct further testing to address propulsion system issues before approving the spacecraft for the return journey.

Currently, the Starliner remains the primary option for returning crew members to Earth, but NASA is considering contingency plans due to the extended stay of its astronauts on the ISS. The Starliner capsule, named "Calypso," could potentially return by the end of July, pending the outcome of the ongoing testing on its faulty propulsion system.

This mission marks the first time the Starliner is carrying astronauts, NASA's Butch Wilmore and Suni Williams. During a press conference, Steve Stich, NASA's Commercial Crew manager, emphasized that the first choice was to return the astronauts on the Starliner and that there was no current need to utilize the agency's alternative transportation option, which would be SpaceX's Crew Dragon.

Although contingency plans involving a SpaceX capsule have been considered, Stich stated that there has been no discussion regarding sending another Crew Dragon to rescue the Starliner crew at present.

Boeing and NASA initiated ground testing of the Starliner's thruster technology at White Sands, New Mexico on July 3. The objective is to replicate an issue which caused up to five of Calypso's thrusters to shut down during the spacecraft's maneuvering to dock with the ISS. Stich expressed the need to ensure that the thruster system remains undamaged despite the intense heat and testing, and he remained hopeful for a return of the Starliner by the end of July.

Boeing and NASA teams in White Sands are currently inspecting the test thruster, aiming to replicate the flight temperatures that were observed. Mark Nappi, Vice President of the Starliner program at Boeing, explained that the testing is crucial to ascertain the performance of the thrusters and to determine the appropriate course of action if any damage is detected.

Both Wilmore and Williams, speaking from the ISS, have expressed confidence in the Starliner's capabilities and trust in the ongoing testing procedures. Despite previous setbacks and delays, such as slipping into a secondary position when compared to SpaceX's Dragon, the Starliner's crew flight test represents a significant milestone towards NASA certifying Boeing for operational, six-month missions starting as early as February.

As the testing continues, NASA remains optimistic about the Starliner's return from the ISS, while also considering potential alternatives to ensure the safe return of its astronauts.