Even with the decision already made and the crew no longer returning on Starliner, teams are still busy testing the spacecraft in preparation for an upcoming undocking. One major hurdle is the fact that the main thruster complications have been going on within the spacecraft’s service module. This will be jettisoned and burn up upon reentry meaning the next week is some of the last time available to test and gather data.
There also are concerns as to whether or not the vehicle will survive reentry which, no matter how small, is the reason it will be uncrewed. Here I will go more in-depth into the return date and time, final spacecraft testing, reentry concerns, and more.
Go For Undocking
Yesterday NASA released a statement confirming the date and time of Starliner’s undocking along with some of the final preparations underway. Here they were quoted saying, “NASA and Boeing concluded a detailed Delta-Flight Test Readiness Review on Thursday, polling “go” to proceed with undocking of the uncrewed Starliner spacecraft no earlier than 6:04 p.m. EDT on Friday, Sept. 6, from the International Space Station, pending weather and operational readiness.”
With an initial launch occurring back on June 5th, this would bring the spacecraft’s total mission duration to right around 3 months. Assuming the undocking does happen on the 6th, Starliner will take about six hours to reach the landing zone at White Sands Space Harbor in New Mexico. If everything goes according to plan, the spacecraft will touch down at about 12:03 a.m. on Saturday, Sept. 7, descending under parachutes and with inflated airbags to cushion the impact. NASA noted that “Recovery teams at the landing zone will safe and prepare the spacecraft for a return to Boeing’s Starliner factory at NASA’s Kennedy Space Center in Florida.”
For Boeing’s future Starliner operations, it’s crucial that this spacecraft comes back and is recovered in a relatively good condition. They already have expressed their intention to continue flying the spacecraft in the future. A loss of this vehicle, even with it being uncrewed, would be the worst-case scenario for Boeing and be devastating for the program.
Interestingly, NASA and Boeing are planning to alter the undocking in a few different ways. Ken Bowersox, the associate administrator at NASA said, “We’re changing the separation sequence that we planned, and we’ll review those aspects at the readiness review. We’re going to go with the simplified separation technique to get away from the station a little more quickly. We’ll get to the deorbit burn and execute that nominally” he said. These changes are aimed at protecting both the crew and the vehicle.
After the recent decision to return without a crew, NASA pointed out that mission managers and flight controllers updated elements of the Starliner systems with specific information for this mission that will allow the spacecraft to execute the return.” Specifically, “The uncrewed Starliner spacecraft will perform a fully autonomous return with flight controllers at Starliner Mission Control in Houston and at Boeing Mission Control Center in Florida. Teams on the ground are able to remotely command the spacecraft if needed through the necessary maneuvers for a safe undocking, re-entry, and parachute-assisted landing in the southwest United States.”
Starliner is designed to operate autonomously and previously completed two uncrewed flights, one of which was undocked from the ISS. As far as why the spacecraft is leaving the station practically right away instead of staying for even more testing, it has to do with the docking port availability. In this case, Starliner must return to Earth before the Crew-9 mission launches to ensure a docking port is available on the station. The Crew 9 launch is scheduled for September 24th.
The NASA Administrator Bill Nelson was quoted saying, “Spaceflight is risky, even at its safest and most routine. A test flight, by nature, is neither safe, nor routine. The decision to keep Butch and Suni aboard the International Space Station and bring Boeing’s Starliner home uncrewed is the result of our commitment to safety: our core value and our North Star” he said.
At the same time as teams prepare for Starliner’s undocking, NASA works with the Crew-9 astronauts to alter plans and seats. They just announced the two astronauts who will no longer be flying on the mission in order to provide seats for Butch and Suni to return. The NASA Chief astronaut said in a statement, “While we’ve changed crew before for a variety of reasons, downsizing crew for this flight was another tough decision to adjust to given that the crew has trained as a crew of four.”
The Reentry Process
Normally, after undocking, the next flight test objective would be to assess the manual piloting of Starliner before switching back to autonomous operations. However, for this specific return, there will be a few changes.
When it is time to return, Starliner will be packed, powered up, and prepared for departure. Then, the docking mechanism disengages, letting Starliner drift away from the space station. After a flyaround inspection, Starliner conducts a series of burns to take it away and position it for deorbit. After exiting the approach ellipsoid, Starliner will begin lowering its orbit and targeting its designated landing zone. It will then execute a tail-sun maneuver to orient its solar arrays sunward to top off its batteries, and then it will set up for deorbit and reentry.
As the Starliner is flying over the Pacific Ocean, it will point the bottom of the vehicle toward the horizon in the direction the spacecraft is moving and commence the deorbit burn, firing four of its 12 aft-facing OMAC thrusters for approximately one minute. For context, these OMAC thrusters are located within the service module and were one of the main areas of concern for a safe return. Basically, the thought process was that various thrusters on the vehicle that are needed for a safe reentry of the capsule are not always operating as intended.
While they likely will perform successfully during the actual return, the margin of error was enough to move the crew to a SpaceX Crew Dragon instead. Either way, when the vehicle does undock, this mission milestone will be watched carefully. In the last teleconference, Steve Stich said, “The bottom line relative to bringing Starliner back is it was just too much uncertainty in the prediction of the thrusters.”
Focusing back on the return, it will then orient itself to safely detach and dispose the service module before the crew module thrusters reorient the spacecraft in the proper re-entry attitude for the entry interface. Meanwhile, the service module will conduct a disposal burn, safely burning up over the Pacific Ocean.
Finally, about 16 minutes before touchdown, Starliner will begin entering Earth’s atmosphere, experiencing temperatures reaching roughly 3,000 degrees Fahrenheit. Once through most of the atmosphere and having shed most of its velocity, Starliner will begin its parachute and landing system deployment sequences at roughly 30,000 feet above the ground. First, two smaller parachutes will deploy and pull off the forward heat shield, exposing the rest of the parachute system. Then, two drogue parachutes will deploy, followed by three pilot chutes that will pull out the three main parachutes. Starliner will spend the rest of its journey to Earth under those three main parachutes, and at approximately 3,000 feet, the base heat shield will jettison, revealing the landing airbags. The six airbags around the perimeter of the spacecraft will inflate, allowing for a safe, soft landing on dry land.
At that point, had the crew been aboard as originally planned, they would have been responsible for jettisoning the parachutes, initiating spacecraft power down, and conducting a satellite phone call with the mission control landing and recovery teams. That all has changed with teams working to prepare for a different mission profile. Importantly, this was a certification mission after all with the goal of flying Starliner much more frequently. In an official statement from before the launch NASA was quoted saying, “Following a landing and successful recovery, NASA will complete work to certify the spacecraft as an operational crew system for long-duration rotation missions to the space station, beginning with NASA’s Boeing Starliner-1 expected to launch in 2025.”
Unfortunately for Boeing, instead there will likely be quite a bit of work to do before the vehicle is cleared for frequent crewed missions. However, both the company and NASA have faith in the spacecraft’s future. Steve Stich said, “Starliner is a very capable spacecraft and, ultimately, this comes down to needing a higher level of certainty to perform a crewed return. The NASA and Boeing teams have completed a tremendous amount of testing and analysis, and this flight test is providing critical information on Starliner’s performance in space. Our efforts will help prepare for the uncrewed return and will greatly benefit future corrective actions for the spacecraft” he said.
Despite the complications, in a recent post, NASA said, “NASA’s Commercial Crew Program requires spacecraft fly a crewed test flight to prove the system is ready for regular flights to and from the space station. Following Starliner’s return, the agency will review all mission-related data to inform what additional actions are required to meet NASA’s certification requirements.” Before that, the undocking and reentry process need to go smoothly, and then NASA can decide what the next steps are for this spacecraft considering its unique flight history.
Conclusion
Boeing’s Starliner spacecraft is officially scheduled to return on September 6th without a crew. Soon after it will attempt a few key thruster firings and mission milestones that need to go perfectly in order for a successful reentry and landing. Once the mission is finally complete, both NASA and Boeing have a lot of work ahead of them as they continue to work on Starliner and its future.