Issues with Apollo Command Modules during Reentry and Splashdown

Introduction

During the Apollo missions, several notable issues were encountered with the command modules, particularly during reentry and splashdown. This article delves into the details of these problems, their causes, and the measures taken to address them, highlighting the overall success and safety of these missions.

Reentry Issues with Apollo 15

On August 7, 1971, during the reentry of Apollo 15, the crew experienced an anomaly that was primarily attributed to the higher-than-expected temperatures experienced by the Command Module's heat shield. Despite these challenges, the reentry was successful, though the spacecraft exhibited more shaking than anticipated. This anomaly highlighted the vulnerabilities in the reentry process and the need for further investigation and improvements in future missions.

Splashdown Issues with Apollo 16

Splashdown Anomalies: On April 21, 1972, during the splashdown of Apollo 16, a minor issue was encountered. While this issue did not pose an immediate threat to the crew, it did present challenges that required close monitoring and intervention.

Propellant Venting Incident: In a closely related incident, Apollo 16 did not vent surplus propellant during descent as a precautionary measure following the reentry anomalies of Apollo 15. This decision was made to ensure the safety of the crew and the integrity of the spacecraft during the return to Earth. However, approximately three days later, while removing the unused propellant, an explosion occurred. This explosion was caused by overpressurization, resulting in 46 people having to make precautionary visits to the hospital.

The incident occurred at the San Diego Naval Air Station, where a tank cart was defueling the Apollo 16 command module after its return from the moon. The explosion was due to the incorrect ratio of neutralizer to oxidizer as a result of the extra oxidizer retained in the Command Module tanks. Due to safety protocols, the affected individuals were suspected of inhaling toxic fumes, but subsequent examinations revealed no symptoms of inhalation.

United States Senate Apollo Investigating Committee Report

The United States Senate Subcommittee on Manned Space Flight was tasked with investigating the incident aboard Apollo 16. The committee's investigation led to the publication of a comprehensive report in 1972. The report detailed the root causes of the explosion and recommended significant changes to ground support equipment and de-pressurization procedures to prevent similar incidents in the future. Key changes included ensuring the correct ratio of neutralizer to oxidizer during the de-pressurization process and updating the equipment to handle the residual oxidizer more safely.

Lesson Learned from Apollo-Soyuz Test Project

While not directly related to Apollo missions, the Apollo-Soyuz Test Project (ASTP) offers valuable insights into the potential hazards associated with reentry and the importance of meticulous precautions. During the descent of ASTP, the crew was accidentally exposed to toxic nitrogen tetroxide fumes caused by the reaction control system (RCS) venting from the spacecraft and re-entering the cabin air intake. The RCS was inadvertently left on during descent, causing the fumes to be sucked into the spacecraft as it drew in outside air. This incident, while not leading to any permanent damage or harm to the crew, resulted in all three astronauts being hospitalized for two weeks in Honolulu for precautionary reasons.

This event underscores the critical importance of thorough pre-launch and in-flight safety protocols and the need for quick and effective emergency responses in the event of an unexpected breach of safety measures.

Concluding Remarks

While these incidents presented significant challenges, they also served as crucial learning opportunities. The Apollo program's response to these issues demonstrated a commitment to continuous improvement and safety, ultimately ensuring the successful completion of reentry and splashdown phases for all Apollo missions. The lessons learned were instrumental in shaping the future of space exploration, setting a higher standard for safety and operational robustness in the years to come.