Human Space Flight Mishaps and Incidents: An Overview
Human spaceflight mishaps and incidents pertain to crew and spacecraft threats and events that can occur in all phases of spaceflight, from prelaunch to ascent, through in-flight mission activities, to reentry and post-landing.
Human spaceflight is extremely risky. Threats to crew health have occurred during every phase of a mission, including prelaunch, launch and ascent, on-orbit, reentry and landing, and post-landing. Spaceflight-related human health threats include the space environment (microgravity, vacuum, and radiation), spacecraft environment (noise, closed life support), and mission (circadian disruption, sleep deprivation) effects. Humans exhibit considerable adaptive responses, such as neurovestibular, musculoskeletal, and cardiovascular changes to microgravity. The spacecraft environment as well can expose crew to toxins and other hazardous materials. Confinement, isolation, and intense workload have created psychosocial adaptation issues.
Thermal protection system failure
Loss of trajectory control
Insufficient electrical power
Avionics system failure
Life-support system failure
Failure to dock/undock
Micrometeoroid orbital debris
Parachute/landing system failure
Training and ground checkout are risky, and three Russian and seven US fatalities have occurred while preparing for space operations. An additional four Russian fatalities related to space operations have occurred upon reentry and landing, and 15 US fatalities, of which seven on ascent (Space Shuttle Challenger) and eight, including one X-15 pilot (X-15 flight 191) who qualified for astronaut wings, on reentry (Space Shuttle Columbia) have occurred (Hall and Shayler 2003).
Human spaceflight became reality on 12 April 1961 when Soviet Air Force Lieutenant Yuri A. Gagarin launched on a modified R-7 booster from Baikonur Cosmodrome and successfully completed a one orbit, 108 min flight in the Vostok I. All six of the manned Vostok series of spacecraft used an ejection seat and personal parachute to land the cosmonaut safely to Earth, rather than landing in the capsule. The Vostok cosmonauts also wore a protective pressure suit in case of depressurization.
Launch Pad Aborts
Explosion , blast overpressure, flying debris, toxic fumes, cryogenic fluids, fire, falls, and noise are among the more important dangers that threaten crew and personnel at the launch pad. To overcome these threats, a launch escape system is used to separate rapidly a crew from the hazard. The launch escape system must be able to pull the crew capsule from an exploding launch vehicle during prelaunch and launch ascent; separate the launch escape system from the crew capsule once free of the catastrophic environment; provide survivable parameters for the crew while considering dynamic pressure, Mach number, and flight path angle; and provide an appropriate crew capsule attitude for entry and parachute deployment. A pad explosion and the associated fireball require that an escape system to be able to protect the crew from heat, overpressure, and an unstable launch platform.
A launch pad abort with activation of a launch escape system occurred on 26 September 1983 at the Baikonur Cosmodrome. A minute and a half before the liftoff of Soyuz T-10A carrying two cosmonauts, a fuel valve failed and leaked fuel onto the launch pad. A fire ensued at the base of the rocket. The launch control team fired the launch escape system, carrying the capsule several miles away for a parachute landing. The crew experienced over 15 G when the escape rocket fired.
On 12 December 1965, an attempted launch of Gemini VI occurred which aborted on the launch pad after main engine ignition. After one and half seconds, the engines abruptly shut down when an electric plug disconnected prematurely. The launch clock started, and as there was no vehicle liftoff, mission rules dictated that the crew initiate the ejection seats to carry the crew away from the fueled booster. The crew elected not to initiate ejection, and the vehicle was safed 40 min later. The correct actions by the crew allowed the mission to be turned around, and they launched successfully on 15 December. This concept was captured eloquently by Shuttle Commander Hoot Gibson in a statement to a rookie astronaut “There are only two things that will get you in trouble flying in space, 1) Not following the rules, 2) Following the rules. The secret is to know the difference.”
One of the most serious US launch aborts occurred on STS-41D (STS 12) Space Shuttle Discovery on 26 June 1984 when a launch pad engine fire occurred. Sensors detected out-of-sequence start of Space Shuttle Main Engine (SSME) which resulted in abort shutdown 4 s before solid rocket booster (SRB) ignition. After the abort, a hydrogen fire occurred near the starboard body flap for about 12 min. Tense moments occurred in the Launch Control Center, and the shuttle crew, in deciding the appropriate crew action, stay in place or conduct an unaided pad egress (Mode 1 Abort). The aft base heat shield water deluge system was repeatedly activated, and the crew remained in the vehicle. Five other shuttle pad aborts occurred after the liquid fuel main engines shut down after ignition but just prior to the solid rocket motor ignition. These were due to redundant sequence launch sequencer failure and happened on STS 41D, STS 51F, STS 55, STS 51, and STS 68.
Ascent failures have occurred due to module separation and engine failures or early engine shutdown during ascent. During the Apollo 13 ascent on 11 April 1970, the second-stage center engine shut down 2 min and 12 s early, possibly due to pogo oscillations. The mission continued by extending the other four engines’ burn time by 4 min. An ascent abort occurred on 5 April 1975, on Soyuz 18-1 with two crews aboard. The third stage ignited, but failed to separate from the second stage. With the launch vehicle gyrating wildly, mission control commanded separation. The crew sustained over 20 Gs on reentry. One crewmember sustained internal injuries, and neither flew in space again.
An abort to orbit (ATO) occurred on STS 51F (STS 19) Space Shuttle Challenger on 29 July 1985, due to multiple sensor failures of the Space Shuttle Main Engines (SSME) , resulting in a center engine shutdown. Three minutes and 31 s into the ascent, one of two center engine’s fuel turbopump temperature sensors failed followed 2 min and 12 s later by loss of the second sensor, resulting in center engine shutdown. 8 min into the flight and close to main engine cutoff, the same temperature sensor in the right engine failed, and the remaining right engine temperature sensor was near redline for engine shutdown. Booster Systems Flight Controller quickly commanded the crew to inhibit any further automatic SSME shutdowns, preventing the potential shutdown of a second engine and a possible abort mode that may have resulted in a crew bailout over the Atlantic. The failed SSME resulted in an abort to orbit (ATO) trajectory and a lower orbital altitude.
In-Flight Events and Emergencies
Spaceflight emergencies occurring on-orbit (Shayler 2000) have included cabin pressure loss (1997), fire (1971, 1977, 1988, and 1997), and a toxic environment (1997). Human factor errors in both space flyers and ground controllers have affected mission milestones, and these have come close to catastrophe.
Loss of vehicle control has occurred on ascent, on-orbit, and during reentry on the X-15 flight 191, Gemini VIII, Apollo 10 Lunar Module, Apollo 13 Command and Service Module, STS 25 (51-L), STS 32, Mir following the Progress M-34 collision, STS 107, and Space Ship One (the X Prize qualifying flight). Gemini VIII launched on 16 March 1966 and 7 h into the mission, after docking to the Agena Target Vehicle, went into a progressively increasing spin when it lost control due to a mechanical failure of an attitude control thruster that stuck open. The crew initiated separation which resulted in a rapidly increasing spin around the long access of the capsule, resulting in 50 rpm roll for 46 s. Max G force was estimated at +/−0.92 Gy and −0.89 Gz. Fortunately the crew was able to shut the errant thruster down 25 min later by pulling circuit breakers, but they noted they were close to their performance limit due to disorientation.
One of the most significant human factor events resulting in loss of vehicle control occurred during the Apollo 10 lunar module (LM) checkout of the ascent stage 47,000 feet above the lunar surface on 18 May 1969. Just prior to descent module separation from the ascent module, the vehicle lurched wildly in pitch and roll, and the crew felt like they had a stuck thruster like Gemini VIII. The LM continued its crazy gyrations, and a warning light indicated that the inertial measuring unit was about to reach its limits. The crew were testing the abort guidance system (AGS) for the first time instead of the primary navigation guidance system (PNGS) they had been using. The AGS had two basic control modes, “attitude hold” and “automatic.” In automatic, the computer would take guidance and start looking for the command module, which was not in range and not what the crew wanted to do. The commander switched the AGS to attitude hold, and then the LM pilot switched it to auto not realizing the commander’s action. In not realizing each other’s action, the crew had cycled the AGS switch, but put it in the wrong position, the automatic instead of attitude hold mode, resulting in frantic gyrations as it tried to find the Command/Service Module (CSM). The crew realized the error and reset the attitude control switches and vehicle motion finally ceased. In the 15 s the vehicle was out of control, it made eight rolls. In the investigation it was determined that two more seconds of loss of control would have resulted in failure to recover the vehicle and it would have impacted the lunar surface.
Docking anomalies have occurred numerous times and resulted in loss of mission for Soyuz 10, Soyuz 15, and Soyuz T-8. In particular, on 23 April 1971, the automatic docking system failed and manual docking of Soyuz 10 with the Salyut 1 space station was not achieved. Soyuz 15 failed to dock with Salyut 3 on 28 August 1974 due to malfunction of the Igla system, and loss of the rendezvous antenna prevented docking of Soyuz T-8 on 22 April 1983. On Skylab 2 (first crewed mission) on 26 May 1973, the crew attempted multiple automatic docking attempts which failed, but they were finally able to manually dock to the Skylab orbital workshop. US docking anomalies in the Space Shuttle program happened on STS-130, on 10 February 2010, and on STS-133, on 26 February 2011. Both times were due to a significant misalignment between the shuttle and ISS during post-capture free drift, related to gravity gradient induced motion.
Combustion events on Russian spacecraft occurred on Salyut 1 in 1971, on Salyut 6 in 1979, on Salyut 7 in 1982, and on Mir in 1994. Two notable and well-documented combustion events on Mir occurred during the period that NASA flew astronauts on Mir. On 24 February 1997, a solid fuel oxygen generator (SFOG) ruptured and ignited, and on 26 February 1998, the overheating of an atmospheric revitalization exchange bed led to combustion and carbon monoxide measured at 600 ppm. Combustion events on the space shuttle were primarily due to insulation shorts or electronics overheating and occurred on STS-6 in 1983, STS-28 in 1989, STS-35 in 1990, and STS-40 in 1991. Combustion events on ISS occurred in March 2005, September 2006, and October 2008.
Toxic atmosphere events which resulted in symptomatic crew have occurred due to carbon monoxide on Mir, ethylene glycol coolant leaks on Mir, and from carbon dioxide on Salyut, Apollo 13, and STS 96. The worse toxic exposure was from nitrogen tetroxide (N2O4) on Apollo 18 of the Apollo-Soyuz Test Project reentry. During the final stages of reentry, the crew switched the auto landing mode to manual mode because the crew thought the parachute deployment seemed delayed. The crew had to perform all the steps of the landing checklist and got out of sequence. As a result the cabin pressure relief valve opened prior to drogue deployment. The manually deployed drogue chute caused the capsule to sway, and the reaction control system (RCS) fired to counteract capsule motion. The opened pressure relief valve allowed toxic propellant gases from RCS thrusters to enter the crew cabin. The crew armed the auto system 30 s later and RCS thruster terminated, but by then the cabin was flooded with toxic nitrogen tetroxide. At splashdown, the capsule inverted (called Stable 2), and one astronaut became unconscious from the fumes. The commander managed to get free and climb back up and get an oxygen mask over the unconscious astronaut, who began to recover. When the command module flipped back upright, the commander opened the vent valve, and fresh air dissipated and the remaining fumes disappeared. The crew were hospitalized for 2 weeks with chemical pneumonia. The total time of toxic exposure was 4 min and 40 s. The estimated average crew N2O4 exposure was 250 ppm, with the OSHA permissible exposure limit of 5 ppm.
Extravehicular activity represents one of the most dangerous endeavors for spaceflight crew (Shayler 2000). Of the 358 spacewalks up to July 2011, there have been 127 significant incidents (36%). During an extravehicular activity, astronauts and cosmonauts have been exposed to thermal injury from sunlight (Gemini 9), separation from the spacecraft (Salyut 6), a suit leak (STS 37), contact with toxic substances (STS 98), and severe pain due to an improper boot fit (STS 98). Visor fogging has occurred from excessive workload on Gemini 9 (Cernan) and Gemini 11 (Gordon), visor fogging from heat exchanger failure on Mir (Artsebarski, Volkov, Tsibliyev, Solovyov), visor fogging from urine leak on STS 11/ STS 41C (Nelson), and visual obscuration from excessive tearing due to visor antifog compound in the eyes on Gemini 10 (Young and Collins) and STS 100 (Hadfield).
Additionally, radiation, retinal injury from sunlight, life-support system failures, work site injury (crush or electrical), hypobaric decompression sickness, and space suit pressure loss due to micrometeoroid and orbital debris are potential concerns for a crew working outside the spacecraft. Workload can cause both mental and/or physical fatigue. Inadvertent tool releases also occur regularly. There have been 40 inadvertent releases during space walks, including Gemini, Salyut, Space Shuttle, Mir, and ISS. Excess workload plagued early spacewalks, resulting in injury and visor fogging. These issues still continue to the present.
One of the most highly significant close calls during a US extravehicular activity (EVA) occurred on the International Space Station (ISS) on 16 July 2013. US astronaut Chris Cassidy and European Space Agency astronaut Luca Parmitano exited the International Space Station US Airlock to begin US Extravehicular Activity 23. About 44 min into the spacewalk, Parmitano reported water on the back of his head and continued to work until the water increased and eventually went from the back of his head onto his face. The water was very cold and indicated a different source than the drink bag, sweat, or urine, but EVA flight controllers and the ISS crew could not identify the water’s source. The EVA was terminated early, and the crew safely ingressed the airlock and underwent an expedited suit removal where it was estimated that about 1.4 liters of water were present. Parmitano reported impaired visibility from water covering his eyes, and difficulty breathing from water covering his nose and ears while returning to the Airlock, as well as audio communication problems from water in the communication cap. As the sun set, the water inside the helmet and darkness so reduced visibility that he had to manually feel for the safety tether cable to return to the airlock. The Investigation Board established the cause for the catastrophic water leakage inside the Extravehicular Mobility Unit (EMU) as a clog inside the EMU space suit fan pump separator caused by inorganic material.
More generally, crew injuries have occurred in 13 EVAs (4%): on Gemini 10, Apollo 17, Salyut 7 PE-1, Salyut 7 VE-3, STS-61-B EVAs 1&2, STS-37, Mir PE-9, STS-63, STS-97/4A, STS-100/6A EVAs 1&2, and STS-134/ULF6. There had been 13 early terminations during spacewalks (4%).
In addition, medical events have occurred in space, and these have affected mission objectives. Indeed, medical evacuation from space has occurred three times, the first in 1976 for intractable headaches following a combustion event (Soyuz 21/ Salyut 5), again in 1985 for urinary infection (Soyuz T-14/ Salyut 7), and most recently in 1987 for a cardiac irregularity (Soyuz TM-2/ Mir EO-2). Medical evacuation was in process on three other occasions when the medical condition stabilized or resolved. In 1976, the Soyuz − 21 mission to Salyut-5, with cosmonauts Volynov and Zholobov, was shortened by 7 weeks with no official reason. Medical records released the following year indicate a decline in crew health and problems from psychological isolation and sensory deprivation. James Oberg mentioned psychological problems may have cut short the mission, although he noted that an acrid odor from the cabin air regeneration system may have been the problem. Brian Burrough, in Dragonfly, quotes NASA sources who have spoken at length with Russian psychologists as stating Soyuz − 21 (Volynov and Zholobov) as terminated early due to “interpersonal issues,” Soyuz T − 14 (Vasyutin) due to “mood and performance issues,” and Soyuz TM-2 in 1987 (Laveikin) due to “interpersonal issues and cardiac irregularity .”
The Vostok capsule, like the later Voskhod, had reentry module separation anomalies. Unstable reentry attitude due to incomplete separation of the crew module from the Service Module occurred on Vostok 1, Vostok 2, Vostok 5, Voskhod 2, and Soyuz 5 (Siddiqi 2000). Most recently, Soyuz TMA-11 encountered a similar problem during reentry on 19 April 2008, when the service module failed to separate from the crew descent module, and the capsule sustaining severe thermal damage to the hatch and during the process. The crew sustained a ballistic reentry which prolonged the time for crew recovery forces to reach them.
Prior to these events, X-15 Flight 191 broke apart near Edwards Air Force Base on 15 November 1967 with US Air Force test pilot Major Michael J. Adams flying. A payload electrical anomaly on ascent and during the coast phase had distracted the pilot and the X-15 gradually yawed to a right angle to flight path at 266,000 feet. Because of the distraction, the attitude flight display was set for roll for payload attitude control and was not set back to pitch/yaw setting for reentry. As the X-15 reentered denser atmosphere, it entered a Mach 5 spin at 230,000 feet. No supersonic spin recovery procedures had been developed. The pilot attempted a spin recovery at 118,000 and the X-15 entered a Mach 4.7/ 45 degree inverted dive. The adaptive flight control system became saturated due to the excessive vehicle motion and developed pitch oscillation, and the X-15 experienced over 15 +/− Gz and 8 g lateral (Gy) and underwent structural breakup 65,000 feet at Mach 3.93. No ejection was initiated. The Accident Board concluded that the mishap was precipitated when the pilot allowed the aircraft to deviate in heading and drove it to such an extreme deviation that there was a complete loss of control. The Board also concluded that pilot actions resulted in a combination of display misinterpretation, distraction, and possible vertigo. They further concluded that the destruction of the aircraft was the result of a sustained control system operation driven by the adaptive flight control system that caused divergent aircraft oscillations and aerodynamic loads in excess of the structural limits. The electrical anomaly was attributed to the use in one of the scientific experiments of a motor that was unsuited to very high altitude environments. The pilot was awarded astronaut wings posthumously as his flight exceeded 50 miles altitude, the US Air Force definition of space.
Risks of spaceflight cover all phases, including launch, ascent, on-orbit, reentry, landing, and post-landing. Fatalities during space operations have occurred primarily during reentry and landing, followed by ascent. Suborbital flight risk in an air-launched winged reentry vehicle based on X-15 flights is 1 fatality/1 event in 199 flights. Orbital flight risk in winged reentry vehicle (STS) is 14 fatalities/2 events in 135 flights. Orbital flight risk in a blunt capsule (Soyuz) is 4 fatalities/2 events in 116 flights. Hazards of the space environment, vehicle environment, and mission architecture present significant challenges to human performance and mission success. Human errors have contributed to events in space that have affected crew health and mission success.
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