On October 15, 2021, an unexpected incident occurred aboard the International Space Station (ISS) involving the Russian Soyuz MS-18 spacecraft. During a scheduled thruster firing test, the Soyuz spacecraft's thrusters continued firing beyond the planned duration, leading to a temporary loss of attitude control for the ISS. This event marked the second such incident in less than three months, following a similar occurrence in July 2021. Fortunately, the crew was unharmed, and the situation was promptly addressed by flight controllers.

Incident Details

At approximately 5:02 a.m. Eastern Daylight Time (EDT) on October 15, 2021, Russian flight controllers initiated a routine thruster firing test on the Soyuz MS-18 spacecraft, which was scheduled to return to Earth with three crew members aboard. The test was intended to assess the spacecraft's propulsion system in preparation for its upcoming departure. However, the thrusters continued firing beyond the designated test window, resulting in an unintended rotation of the ISS. By 5:13 a.m. EDT, the station had experienced a loss of attitude control, deviating from its intended orientation. Within 30 minutes, flight controllers regained control of the station, restoring it to a stable configuration. The crew was awake at the time of the event and was not in any danger. ([nasa.gov](

Cause and Response

The root cause of the unplanned thruster firing was identified as a procedural error in the instructions sent by mission control to Soyuz Commander Oleg Novitskiy ahead of the test. This error led to the thrusters firing beyond the planned duration. Fortunately, the Soyuz spacecraft's flight control system had a built-in limit for engine testing, which generated a cutoff command once the allocated propellant for the test was consumed. This safety feature ensured that the propellant reserves needed for landing remained intact. ([en.wikipedia.org](

In response to the incident, NASA and Roscosmos, the Russian space agency, collaborated to understand the root cause and implement corrective measures. The crew aboard the ISS followed established emergency procedures, and flight controllers on the ground worked swiftly to regain attitude control of the station. The incident underscored the importance of precise communication and procedural adherence in space operations. ([nasa.gov](

Historical Context

This incident was the second occurrence of unintended thruster firings affecting the ISS in a short period. The first occurred on July 29, 2021, when the Nauka multipurpose laboratory module, newly added to the Russian segment of the ISS, inadvertently fired its thrusters after docking. This unplanned firing caused the station to move out of orientation, but ground teams quickly regained control, and the crew was never in any danger. ([nasa.gov](

These events highlight the complexities and challenges associated with operating the ISS, particularly concerning the integration of new modules and spacecraft. Each incident provided valuable lessons that contributed to refining operational procedures and enhancing the safety protocols aboard the station. ([space.com](

Impact on ISS Operations

Despite the temporary loss of attitude control, the ISS continued its scientific research and daily operations without significant disruption. The crew remained vigilant, adhering to standard protocols to ensure their safety and the integrity of the station. The incident also prompted a review of communication and procedural protocols between mission control and spacecraft commanders to prevent similar occurrences in the future. ([nasa.gov](

In the aftermath, NASA and Roscosmos emphasized the importance of continuous training and simulation exercises to prepare for such anomalies. The collaboration between the two agencies was crucial in swiftly resolving the issue and maintaining the ISS's operational stability. ([sma.nasa.gov](

Conclusion

The Soyuz MS-18 thruster firing incident on October 15, 2021, served as a critical reminder of the complexities involved in operating the International Space Station. While the event temporarily affected the station's orientation, the prompt and coordinated response by the crew and ground controllers ensured the safety of all personnel and the continued success of the ISS's mission. Ongoing vigilance, thorough training, and effective communication remain essential to the safe and efficient operation of the ISS. ([nasa.gov](

Sources

  • NASA — Crew Work and Station Attitude Update Before Soyuz Crew Departure —
  • NASA — Space Station Stable After Earlier Unplanned MLM Thruster Firing —
  • NASA — Soyuz MS-18 —
  • NASA — Significant Incidents —
  • NASA — Soyuz MS-18 —