Yesterday NASA held the first briefing on the results of tests of the ground maneuvering engines of the Boeing Starliner spacecraft. Five of them were turned off during an attempt to dock the ship with the ISS on June 5. In order to safely return the spacecraft to the ground, NASA engineers began to re-analyze the situation with the engines during the bench tests. As it turned out, the maneuvering engines are heating up more than the calculated indicators.

The maneuvering engines for Starliner suddenly stopped working for the first time. That was the case during the device’s previous unmanned flight to the ISS. And it happened again when it attempted to dock with the station during its first manned test mission. The ground crew then lowered four of them into the water, allowing the ship to dock safely a day later than planned.

Recent ground tests have shown that the orbital correction engines in the service module are running hotter than expected. This is likely due to the tight confines of the service bay and the heating from sunlight. During ground tests, engineers exposed the engines to this extreme heat to replicate the conditions that led to the failure.

In general, the trimmers are almost not involved in the process of lifting the ship from orbit. For this, Starliner uses more powerful stern engines. However, during the docking and maneuvering phase near the ISS, the ship still relies on the work of the trimmers, which have 28 pieces.

NASA is also investigating an anomaly caused by leaky connections in the helium transport system. For the agency, this is an unexpected problem, the causes of which are not yet clear. Engineers believe that this effect could be caused by blockage of the connections or excess oil in the oil seals. Experts do not rule out that the design of the connections will need to be changed to something else in the future.

In general, NASA is inclined to believe that the Boeing Starliner could be returned to Earth by the end of July. In mid-August, another shift of astronauts will fly to the ISS on the SpaceX Dragon Crew ship, and the docking bay occupied by the Boeing ship will have to be vacated. As an alternative measure, as a last resort, the agency will first return to Earth the previous shift, which is not normally done (the crew will transfer the shift to each other on the station), which will make room for the ship.

The Starliner crew, “stranded” on the ISS, have voiced some words of support for the ship. Barry Wilmore and Sunita Williams say the Starliner is a valuable vessel, but they have been slow to recommend it for regular flights.