Mission Boe-OFT: the Boeing CST-100 Starliner spacecraft has come back to Earth

Boeing's CST-100 Starliner spacecraft landing (Image NASA TV)
Boeing’s CST-100 Starliner spacecraft landing (Image NASA TV)

A little while ago Boeing’s CST-100 Starliner spacecraft landed at the White Sands Missile Range in New Mexico, ending its Boe-OFT (Boeing Orbital Flight Test) mission. Unlike the previous American spacecraft, this one doesn’t splash down in the ocean but lands on the ground. The ground staff intervened in an exercise of the assistance activity that will take place in manned missions.

This isn’t the conclusion of the Boe-OFT mission hoped for by Boeing and NASA since it occurred prematurely following the off-nominal orbit insertion that took place last Friday about half an hour after launch. This means that the mission is incomplete and in two days it was possible to achieve only some of the original objectives, missing the ones connected to the arrival at the International Space Station.

The analysis of the data about the Boe-OFT mission will continue to try to obtain final answers, but the preliminary one suggests that the failure to enter the correct orbit was due to a problem with what’s called Mission Elapsed Time (MET), the time elapsed since the start of the mission indicated by the clock on board the CST-100 Starliner spacecraft. According to the first reconstruction, that clock marked the wrong time for reasons that are to be clarified, with the consequence that the onboard computer believed it was in a different phase of the flight and began a series of maneuvers that were needed according to the calculations based on that time consuming a significant amount of propellant.

The flight of the CST-100 Starliner spacecraft was guided by the onboard computer, but from the mission control center they attempted to take control when they noticed the anomaly. Unfortunately, a delay in receiving those commands was caused by the fact that in those minutes the communications with the CST-100 Starliner were moving from one satellite of the TDRS constellation to another. A brief interruption in communications made all the difference because by the time mission control center took over the CST-100 Starliner, the remaining propellant was insufficient to insert it into the orbit needed to reach the International Space Station.

At Friday’s post-launch press conference, NASA administrator Jim Bridenstine tried to see the glass half full, stating that some of the goals could still be achieved. The Boeing astronauts who are supposed to be part of the crew on the first CST-100 Starliner manned mission explained that their presence would’ve allowed them to quickly take control of the spacecraft to manually insert it into the correct orbit.

Certainly something didn’t work properly in the automatic systems. NASA and Boeing are already working to ascertain the root of the problem to eliminate it and understand why it didn’t emerge in the simulations conducted during the development of the CST-100 Starliner spacecraft. There was an element of bad luck because satellite communications were interrupted at the worst time showing how sometimes automatic systems are unable to respond correctly in case of problems.

The results of the investigation and the analysis of the data collected during a very shortened mission will allow to decide if a second test of the CST-100 Starliner spacecraft unmanned will be needed. The docking with the International Space Station is one of the critical moments for the safety of the spacecraft and the Station’s crews, and the test aimed to verify that the docking system works correctly on both the hardware and software sides. It’s another case in which the presence of a crew onboard the CST-100 Starliner could remedy at least some problems of the automatic system with a manual docking like the ones that occasionally were carried out by the pilots of Russian spacecraft.

A difficult year for Boeing ended with a crippled space mission. Tests are carried out precisely to find possible problems that no simulation and ground tests could detect, but the Boe-OFT mission ended with various doubts. For the moment the priority is to understand if the first reconstruction of the events is correct and correct the problem. At that point NASA will decide how to proceed in the next mission of the CST-100 Starliner spacecraft.

The recovery team inspecting the CST-100 Starliner spacecraft (Image NASA TV)
The recovery team inspecting the CST-100 Starliner spacecraft (Image NASA TV)

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