As We Teeter into August Where's Starliner?

As we collect ourselves to stumble into August, Starliner Crewed Flight Test 1 with Butch Wilmore and Suni Williams goes into day #51 of its 8 day mission to the ISS. Yesterday, NASA and Boeing representatives held a press conference to bring everyone up to date on the mission status, but it honestly didn't offer much new content.  

As a short refresher, there are two main problems; possibly related, possibly just coincidental. The spacecraft's reaction control thrusters overheated, and some of them shut off as Starliner approached the space station back on June 6. The other problem involves helium leaks in the craft's propulsion system that have been known about since before launch. 

We're not supposed to say that Starliner is stuck at the ISS or that the crew is marooned in space with no way home. Stephen Green, the Vodkapundit at PJ Media, openly wonders when it becomes acceptable to say these things. 

On Thursday, NASA and Boeing managers said they still plan to bring Wilmore and Williams home on the Starliner spacecraft. In the last few weeks, ground teams completed testing of a thruster on a test stand at White Sands, New Mexico. This weekend, Boeing and NASA plan to fire the spacecraft's thrusters in orbit to check their performance while docked at the space station.

“I think we’re starting to close in on those final pieces of flight rationale to make sure that we can come home safely, and that’s our primary focus right now," Stich said.

Stich acknowledges there is talk about bringing the crew home on a Crew Dragon, since there's one on the station at the moment (Crew 8) and another that will going up to the ISS in the next couple of weeks (Crew 9) but still says their goal is to complete the mission as intended, bringing Wilmore and Williams home on Starliner. 

They just don't know when that will be. You'll recall that the original 45 day rating the mission had was based on some degree of battery recharging, which was then allowed to double to being a 90 day mission. That means this mission can keep going to around the end of August.  

The most important of these tests was a series of test-firings of a Starliner thruster on the ground. This thruster was taken from a set of hardware slated to fly on a future Starlink mission, and engineers put it through a stress test, firing it numerous times to replicate the sequence of pulses it would see in flight. The testing simulated two sequences of flying up to the space station, and five sequences the thruster would execute during undocking and a deorbit burn for return to Earth.

"This thruster has seen quite a bit of pulses, maybe even more than what we would anticipate we would see during a flight, and more aggressive in terms of two uphills and five downhills," Stich said. “What we did see in the thruster is the same kind of thrust degradation that we're seeing on orbit. In a number of the thrusters (on Starliner), we're seeing reduced thrust, which is important.”

The thruster tested on the ground at White Sands Missile Range showed a similar degradation to that seen while trying to dock with the ISS - that's progress. The thruster that showed degraded thrust displayed bulging in a Teflon seal in an oxidizer's poppet valve when it was inspected.  The bulging was considered able to restrict the flow of nitrogen tetroxide propellant. 

"That poppet has a Teflon seal at the end of it," Nappi said. "Through the heating and natural vacuum that occurs with the thruster firing, that poppet seal was deformed and actually bulged out a little bit."

Stich said engineers are evaluating the integrity of the Teflon seal to determine if it could remain intact through the undocking and deorbit burn of the Starliner spacecraft. The thrusters aren't needed while Starliner is attached to the space station. 

More hot-fire testing is being set up for this weekend with the Starliner docked to the space station. 

"It’s a very important set of tests over the weekend that we’ll do," Stich said. "The hot-fire test this weekend will give us confidence in all the thrusters," Stich said.

Assuming good results this weekend, NASA managers could convene a flight readiness review at the end of next week to discuss the health of the Starliner spacecraft. If NASA's leadership signs off on the plan, Starliner could be cleared to return to Earth with Wilmore and Williams as soon as early August. NASA would like to have the spacecraft back on the ground before the launch of SpaceX's next Crew Dragon mission, currently slated for no earlier than August 18.

Time exposure of Starliner on orbit while docked to the Space Station. NASA photo

Unsurprisingly, this extension of the mission and these difficult problems will impact missions further out in the schedule. NASA had hoped the next Starliner flight, would be the Crew 10 mission carrying four astronauts on a six-month expedition at the space station, and would be ready for liftoff in February. Stich ruled that out in a press conference on Friday. The Crew 10 mission has been bumped onto a Crew Dragon, leaving the earliest possible crewed mission for Starliner looking to be six months later, or one year from now.