By now Starliner is back on the ground and on its way to Boeing Facilities in Florida for inspection and refurbishment. This comes after a successful undocking and reentry of the capsule and a landing at White Sands.
However, as revealed in the post-landing news conference, there were a few issues that arose during the return including multiple thruster failures and even a new problem that popped up with the navigation system. This puts the company in an even more difficult position as they decide what to do going forward.
Overheating Thrusters
On September 6th at 6:04 p.m. EDT, Boeing’s uncrewed Starliner spacecraft undocked from the International Space Station. Practically right away it began a number of different thruster firings apart of the Breakout Burn, which was meant to undock faster than normal. They had expressed prior to the undocking that one of the purposes of this was the fact that it put less stress on the thrusters.
Over the next few hours, the capsule traveled further from the station in preparation for its de-orbit burn. This was one of the areas leading up to the undocking that NASA officials were partially worried about and helped their decision to send the spacecraft back uncrewed. The thought process being, that this mission milestone in particular was one of the most demanding on the thrusters.
As somewhat predicted, they did run into higher temperatures than intended. In the post-landing news conference Steve Stich, the commercial crew program manager at NASA said, “We had a deorbit burn that executed on time at 11:17pm. It was about a 130m/s burn. We watched the burn, we saw a couple things, in the starboard doghouse we talked a little bit about the thruster temperatures there being a little higher. One of the thrusters S2A2 didn’t fail off, but it had a little higher temperature than expected, so we’ll look at that data after the flight. And then another thruster in the top dog house had a little higher temperature” he said.
He then mentioned, “We intentionally had planned to inhibit the software to let thrusters fail off during the deorbit burn and that worked fine, so we really need to go back and look at all that data” he said.
Despite these higher temperatures, the thrusters were able to complete the deorbit burn and send Starliner on its way toward landing. Only a few minutes after this burn the service module was jettisoned to burn up during Earth reentry. For context, that service module housed most of the thrusters that up until this point had been having issues. Unfortunately, another thruster issue occurred later in the flight with the crew module.
Here, Steve Stich said, “During entry, the vehicle performed great. The one thing we will have to go look at after the flight is when we hot-fired before we had the entry, on the crew module there are 12 thrusters, and one of the up-firing thrusters did not perform at all. We hot-fired it twice and we used two different methods to talk to it, two different parts of the avionics system, and we never saw any chamber pressure or any pulses there.”
He went on to say, “This is different from the service module thrusters, it’s what we call a monopropellant system. It’s very simple it has a valve that opens and then the propellant flows across that cat bed, and as it flows across that cat bed there’s a reaction and it causes thrust. And for some reason that thruster did not perform,” he said.
Thankfully, they were able to instead use a redundant thruster in order to compensate for that thruster malfunction. At this point in the mission, Starliner was on track and using its navigation system to ensure it ended up at the White Sands landing location.
This process however also ran into an anomaly. Steve Stich said, “It was a bullseye landing, great landing out at White Sands. The one thing we worked a little bit during entry was, for some reason when we came out of the plasma, the navigation system, we call it the Siggy3, kinda failed off temporarily, and then that system was brought back on and it was tracking just fine. Siggy2 also had a couple little hiccups during entry, we’ll have to go look at that” he said.
Despite these anomalies, the capsule deployed its parachutes and eventually made a safe landing at White Sands bringing the mission to an end. Teams then went over and ensured the vehicle was safe before performing a host of different objectives.
In a way, the mission isn’t over until both Butch and Suni are back on the ground but that won’t be until early next year. Currently, the SpaceX Crew-9 launch which will be the vehicle to return them is set to launch on September 24th in a few weeks.
Starliner’s Future
Based on recent events and Starliner’s history as a whole, it’s hard to picture what the vehicle’s future will look like. We’ve now heard from NASA multiple times that they intend to keep working with Boeing and pursue a crewed flight in the future however that’s not going to be easy.
It’s going to take both a significant amount of time and money to ensure this vehicle is ready for a full crew and ISS rotation. One of the main problems is the fact that nearly every launch a new set of issues pops up. For example, on this flight the helium leaks and overheating thrusters were far from ideal but they were thought to be the main issue and somewhat understood. Then during the return, we see anomalies with one of the crew module’s thrusters and even the navigation system.
While inconsequential to the overall landing, it joins a long list of little things that didn’t quite go right. When it comes to a vehicle carrying humans, the fewer surprises the better.
Either way, work has now begun to try and fix any issues and prepare the spacecraft for a future crewed mission. Stich explained that three different Boeing teams are working on different parts of the spacecraft. Specifically, he said “It’s really great to get the spacecraft back and then we’ll start the next steps. We’ve been talking to the Boeing team already about the next steps. We want to get into the spacecraft and start working on the helium system. We know we have a seal that we’ve got to go replace on the flanges on the RCS thrusters. We need to upgrade that material to make it hyperbolic compatible, and maybe a little bigger size will do that.”
“Boeings already formed teams to look at the changes that need to be made for Starliner-1. In terms of the thermal environment, can we do something different to make the doghouse less thermally severe for the OMAC burns and the thrusters. A second team is looking at the hot fire of the thrusters thats needed on the service module to complete the qualification and make sure we understand which pulses cause the Teflon seal on the oxide to swell. And then thirdly there’s a GNC team already formed to look and figure out how we go fly the vehicle differently. Can we change the dead bands, can we change the way it flies to not stress the thrusters. And so that work has already started and that’s really the path to Starliner-1” he said.
When he mentions Starliner-1, he’s referring to the official first crewed mission of the vehicle. In other words, the crewed flight we just watched was a certification mission with a partial crew to make sure the vehicle was capable. Had the mission been successful and the crew returned on Starliner, Starliner-1 would be the next mission. Now teams are trying to decide whether they go straight to Starliner-1 or require another test flight.
Based on what we’re hearing, it sounds more like if they do continue on with the vehicle, the next flight will be an official crewed mission rather than another test. That mission was originally scheduled for Feburary 2025 but was delayed to August 2025.
Another important aspect of the Starliner program as a whole involves the monetary charges against the vehicle. At this point, NASA has issued $1.6 billion in charges to Boeing and Starliner in particular due to delays and issues with the vehicle. This recent uncrewed return on a crewed flight is only expected to add to that total as they now work to fix a number of different issues and take more time. When talking about future flights Stich said, “We’re going to take our time to figure out what we need to do to go fly Starliner-1. It’s probably too early to think about what the next flight looks like.”
The last piece of information relative to the program and this mission has to do with Boeing’s representatives. After Starliner landed NASA held a nes conference where we could hear from both NASA and Boeing on the vehilce’s next steps. Before the event, a NASA advisory stated that two Boeing executives — John Shannon, vice president of Boeing Exploration Systems, and Mark Nappi, Boeing vice president and commercial crew program manager — would participate.
In reality, neither attended and only NASA officials were at the meeting.
Conclusion
After about 3 months in space, the Starliner capsule finally returned. Unfortunately for Boeing, this was without a crew after NASA determined that thruster issues among other complications added too much risk for a human return. Now the company is in an interesting position as they decide what the best future is for their spacecraft.