Ten years of hard work? The first manned flight of the Starliner spacecraft is delayed again

Boeing's Starliner spacecraft was originally scheduled to conduct its first manned test flight on July 21 this year. However, on June 1, NASA and Boeing jointly announced that the first manned test flight would be postponed due to two recently discovered technical problems with the spacecraft. It has been reported that the mission will be carried out no earlier than the end of 2023, and the possibility of Boeing abandoning the Starliner spacecraft is not ruled out. So why is the development process of the Starliner spacecraft so bumpy? What are its technical features? What are its future prospects?

"The rich and powerful" are expected to

The story of the Starliner manned spacecraft began in 2010. At that time, due to the high cost of operation and maintenance, and the two disasters of "Challenger" in 1986 and "Columbia" in 2003, the space shuttle had entered the countdown to retirement, and the United States was temporarily facing the loss of its independent manned spaceflight capability. American astronauts could only take Russian spacecraft to the International Space Station. However, after the space shuttle was officially retired in 2011, the ticket price of Russian spacecraft continued to rise, and the fee for transporting each Western astronaut soared from more than 20 million US dollars to more than 80 million US dollars in 2020.

Boeing's Starliner spacecraft in the Kennedy Space Center's final assembly and test facility

To deal with this embarrassing situation, NASA has, on the one hand, launched a project to develop the Orion spacecraft that can take into account both low-Earth orbit and deep space exploration missions, and on the other hand, promoted the development of the commercial manned program, hoping that private aerospace companies will take the lead and send American astronauts and cargo to the international space station more cheaply.

In September 2014, NASA announced that Boeing and SpaceX had each received contracts for manned launch services to the International Space Station, with the amounts being $4.2 billion and $2.6 billion respectively. Boeing has been involved in NASA's Commercial Crew Program from beginning to end, and has received more government funding than its competitors, making it the most trusted by the US government. Boeing is also full of confidence, declaring that it will prepare the Starliner spacecraft for commercial manned missions in 2015.

Boeing is qualified to be so confident. As one of the oldest aerospace manufacturers in the United States, it has achieved remarkable achievements since its establishment in 1916. Especially after World War II, Boeing raised funds on its own to enter the field of aerospace technology, overcome the difficulties of solid rocket engines, and won the contract for the Minuteman missile. It is still one of the main suppliers of strategic ballistic missiles in the United States. After that, Boeing continued to improve its technical strength in the aerospace field through mergers and acquisitions, becoming one of the major rocket manufacturers in the United States. The Delta 4 series of rockets it developed has been the most powerful rocket in the United States for a long time. It is also one of the major satellite manufacturers in the United States, and it has a pivotal position in both the military and commercial markets. Boeing has been an important participant in major American aerospace programs such as the Apollo Program, the Space Shuttle, and the International Space Station. It seems that it is not a problem to develop a safe and reliable manned spacecraft in low-Earth orbit.

Accidents frequently occurred during the development process

In fact, the US commercial manned program has not been smooth sailing. The unmanned test flights of the spacecraft have been repeatedly delayed. The earliest plan was to carry out in 2015, and then it was repeatedly postponed. It was not until March 2019 that SpaceX successfully completed the first unmanned test flight of the manned Dragon spacecraft.

The Starliner spacecraft was expected to fly earlier, but it uses multiple liquid rocket engines to implement the technical solution of escape. In addition to escape, the rocket engine is also used for vacuum trajectory change propulsion and re-entry process deceleration and braking. It must be able to be reused many times, so the technology is complex. During the emergency abort system test in 2018, Boeing discovered that the engine had a propellant leak problem and had to partially redesign the spacecraft propulsion system. This postponed the first unmanned test flight of the Starliner spacecraft to December 2019.

During the Starliner's first unmanned orbital test flight, a mission timer on the spacecraft failed, preventing the spacecraft from completing the orbital maneuver as planned after the separation of the rocket and the spacecraft. The failure consumed a large amount of propellant on the spacecraft, resulting in the remaining propellant being insufficient to meet the conditions for its safe docking with the International Space Station, so the docking mission had to be canceled and the spacecraft returned to Earth early.

Subsequent investigations found that the time point for the timer initialization was incorrect, resulting in an 11-hour timing deviation. During the subsequent on-orbit inspection, the Boeing development team discovered that the spacecraft had a "valve mapping error", so they carried out emergency troubleshooting and sent a revised flight control code about 3 hours before the spacecraft landed.

After the unsuccessful first test flight of Starliner, NASA proposed a large number of rectification suggestions and required Boeing to conduct another unmanned test flight for safety reasons. Boeing had to pay $410 million of its own money to conduct the second unmanned orbital test flight.

In August 2021, Starliner was once again pushed to the launch pad, but during the pre-launch inspection, it was discovered that 13 propellant valves were in abnormal condition, and Boeing once again embarked on a long road of troubleshooting.

After investigation, it was found that the main reason for the valve "stuck" was the interaction between the propellant and the atmospheric moisture, which caused corrosion to the valve material. However, the problem was not completely solved. Instead, the corrosion was alleviated by purifying the system and sealing the connectors to prevent water vapor from invading the propulsion system valves. To this end, Boeing also set a restrictive window period to reduce propellant corrosion, that is, the spacecraft must be launched within 60 days after the propellant is loaded into the service module.

In May 2022, the Starliner spacecraft carried out its second unmanned orbital test flight and docked with the International Space Station for the first time. However, during the orbital entry phase, one engine shut down due to a fault only one second after the spacecraft ignited, and the backup engine started by the flight control also shut down for unknown reasons after only 25 seconds of operation. Fortunately, the spacecraft started another set of engines for maneuvers and finally completed the orbital entry.

Industry insiders believe that the mission was successful and the Starliner spacecraft can launch subsequent manned missions. However, on May 26 this year, NASA said that two new worrying problems had been discovered, which led to another delay in the spacecraft's first manned test flight.

Boeing's Starliner spacecraft docks with the International Space Station on the OFT-2 mission

Unpredictable project prospects

Two days before Boeing announced the postponement of the test flight, it happened to be the third anniversary of SpaceX's manned flight. So far, the manned Dragon spacecraft has performed missions for the US government and commercial customers, sending a total of 38 people into space for 10 manned missions. NASA still said that it expects Boeing to put the "Starliner" into use and become the second supplier to provide project redundancy, which was originally the "internally scheduled mission" of the manned Dragon spacecraft.

Next, the Starliner spacecraft project team faces great pressure. Take the two problems announced this time as an example. One is that the load limit of the parachute soft connection assembly is lower than expected. When a main parachute fails, it will bring additional load to the other two parachutes, reducing the overall safety factor of the parachute system. The other is the flammability of the tape wrapped around the spacecraft harness. In the event of "multiple failures" in other parts of the spacecraft, the tape may burn, bringing greater potential risks. It is not difficult to find that these two problems do not involve too advanced technology, but are more like the consequences of poor management.

Looking ahead, the future of Interstellar can be described as “clouded.”

First, there is the issue of cost. In November 2019, NASA first released estimates of the cost of seats for both spacecraft: $55 million for the Crew Dragon and $90 million for the Starliner. Boeing received $287.2 million in additional compensation beyond the fixed-price contract, and then adjusted the seat cost to about $70 million by loading additional cargo in the Starliner crew capsule, but it is still higher than the price of the Crew Dragon before it carried more crew members.

The second issue is the launch vehicle. The Starliner spacecraft was originally to be launched by the Atlas V series rocket, but this type of rocket is about to be phased out, and the scheduled replacement, the Vulcan rocket, has had its first flight delayed, adding to the complexity and uncertainty of the mission.

Finally, there is the issue of the retirement of the International Space Station. In September 2022, the US government purchased five more Crew Dragon spacecraft transportation services to the International Space Station, which is expected to support the retirement of the International Space Station. Even if the "Starliner" is successfully put into service, it is expected to only fly once a year, which undoubtedly makes its prospects bleak. (Author: Yu Yuanhang, review expert: Jiang Fan, deputy director of the Science and Technology Committee of China Aerospace Science and Technology Corporation)