A Brief History of Launch Aborts

The space-related accidents that have been in the news recently are reminders of the inherent dangers of spaceflight. And such losses are certainly more keenly felt when crews are involved. Because of this, various abort options usually exist for all phases of ascent in case of a crewed launch vehicle malfunction. There were two exceptions of note to this philosophy during over half a century of crewed spaceflight.

The first exceptions were the Soviet Voskhod missions of 1964 and 1965 where no abort options existed during the first 27 seconds of flight and only limited options with questionable survivability were available for the next 18 seconds (see “50 Years Ago Today: The Mission of Voskhod 1”). The reason for this was the need to beat the American Gemini program for propaganda reasons which left insufficient time to develop and test a launch escape system (LES) for Voskhod. The other exception was the American Space Shuttle which, after it became “operational” and its ejection seats were removed, had no abort options during the first two minutes of flight while the solid rocket boosters were firing. The reason for this was the belief that the highly redundant Space Shuttle systems were so reliable that having no abort options during this phase of flight was an acceptable risk. This gamble cost the lives of seven astronauts when the Space Shuttle Challenger disintegrated 73 seconds after launch on January 28, 1986. Instead of replacing a crewed spacecraft with such an obvious design deficiency, NASA doubled down on the program and continued flying the Space Shuttle for the next quarter of a century with no realistic abort options early in the flight (fortunately without any additional loss of life, at least from launch accidents).

The Soviet manned Voskhod missions of 1964-65 had no launch abort options for their first 27 seconds of flight. The American Space Shuttle flown from 1981 to 2011 had no abort options for its first two minutes of flight. (RKK Energia)

Looking at the long history of crewed spaceflight, I was curious to find examples of actual launch aborts. Of course there were numerous instances of missions being aborted on the launch pad just moments after the launch vehicle’s engines ignited but these were flights that never left the pad (see “Rendezvous in Space: The Gemini 6 Launch Abort“). There was also the abort that took place during the STS-51F shuttle mission launched on July 29, 1985 ironically involving the Space Shuttle Challenger that would be lost six months later. As a result of the loss of multiple sensors on the Challenger’s three main engines during the ascent of STS-51F, one of these engines shutdown 5 minutes and 41 seconds after liftoff forcing an “abort to orbit”. But in my mind, this does not count a a true “launch abort” since the Challenger carrying Spacelab 2 still made it into orbit allowing it to carry out its week-long mission albeit in a slightly lower than planned orbit. After looking through the history of crewed spaceflight, I could find only two launch aborts that involved missions that actually got off the pad in one way or another and were unable to fulfill their mission.

The April 5 Anomaly

The first genuine launch abort of a crewed space mission occurred on April 5, 1975 involving what was to be called “Soyuz 18”. The crew for this flight consisted of veteran cosmonauts Vasili Lazarev as the commander and Oleg Makarov as the flight engineer. These two cosmonauts had flown together earlier on Soyuz 12 launched on September 27, 1973.   The purpose of the Soyuz 12 mission was to perform a two-day orbital flight test of the upgraded Soyuz 7K-T ferry to check out the modifications made after the loss of three cosmonauts at the end of the Soyuz 11 mission to the Soviet Union’s first space station, Salyut 1, in June 1971. The mission for this new flight with Lazarev and Makarov, using the call sign “Urals”, was to spend 60 days onboard the Salyut 4 space station which had been launched into orbit the previous December and had hosted the crew of Soyuz 17 for a 28-day mission. The intent was to have the crew back on Earth before the launch of the upcoming Apollo-Soyuz Test Project (ASTP) mission in July.

Cosmonauts Oleg Makarov (left) and Vasili Lazarev (right) shown training for their 60-day mission on Salyut 4 in 1975. Instead their flight was cut short in the first launch abort known as the “April 5 anomaly”.

The Soyuz 7K-T number 39 atop its Soyuz 11A511 launch vehicle serial number Kh15000-023 lifted off from Launch Complex 1 at the Baikonur Cosomodrome (the same pad used by Yuri Gagarin) at 14:04:54 Moscow Time on April 5, 1975. At 120 seconds after launch, the four boosters of the Soyuz rocket were dropped as planned from the Blok A core followed 30 seconds later by the jettisoning of the LES which was no longer needed to support an abort for the rest of the flight. At 288 seconds after launch, the Blok A shut down as planned. The Blok I upper stage was then suppose to separate and ignite sending the Soyuz into orbit. Instead the Blok I RD-461 engine ignited and the ascending craft began to roll and pitch heavily. This was followed by a “Booster Failure” alarm sounding in the Soyuz cockpit and the emergency shutdown of the RD-461 engine when the attitude had deviated by more than the preset limit of 10 degrees only four seconds after ignition.

A Russian diagram of the various Soyuz launch abort options during its ascent. The option used during the “April 5 anomaly” is depicted in the third panel. Click on image to enlarge. (RKK Energia)

With the automatic abort system triggered at an altitude of 145 kilometers (above the widely recognized 100-kilometer threshold of space), the Soyuz’s own propulsion system pushed the spacecraft clear of the now inert launch vehicle followed by the separation of the three modules in preparation for an emergency descent. After reaching a peak altitude of 192 kilometers and the crew experiencing about 400 seconds of weightlessness, the Soyuz automatically executed a high-G ballistic reentry with a peak braking load of 21.3 G instead of the normal 3 to 4 G owing to a flight path that was steeper than a normal descent from orbit. The Soyuz descent module came down in the Altai Mountains 1,574 kilometers downrange after a flight of 21 minutes and 27 seconds. This was the first manned suborbital spaceflight since X-15 flight number 197 on August 8, 1968 (if you accept the USAF 50-mile definition for the threshold of space) or flight number 91 on August 22, 1963 (if you prefer the 100-kilometer Karman line definition – see “A History of Suborbital Crewed Spaceflights“).

The landing site of what became popularly known in the West as “Soyuz 18A”, a mountain called Teremok-3, was covered in chest-deep powdery snow at the time of landing. The descent module came to a stop just 150 meters shy of a sheer drop after rolling down the mountain’s steep slope before its parachute lines had become entangled in some vegetation. The cosmonauts donned their cold-weather survival gear and exited the capsule. Fearing that they might have come down in China, Lazarev burned documents having to do with a military experiment he was to perform on Salyut 4 relating to naked eye orbital reconnaissance. But soon the cosmonauts heard from the Soviet rescue teams on the radio – they had come down in Soviet territory 829 kilometers from the border. After much difficulty dealing with the mountainous terrain, the cosmonauts were rescued following a night spent on the mountain. On April 7, after the cosmonauts had returned home and been checked out, Soviet officials broke the news of the launch abort. Naturally, the American partners of the ASTP were interested in the cause of the mishap and required an explanation.

Closeup of a Soyuz launch vehicle showing the Blok I upper stage (left) and the Blok A core with its four boosters (right) and the lattice structure visible that connect the two. It was a failure in the separation mechanism in this lattice that caused the “April 5 anomaly”. (NASA)

The investigation into the “April 5 anomaly”, as it was officially known in the Soviet Union, showed that excessive vibration during the ascent of the 11A511 launch vehicle had caused an electrical relay to close unexpectedly which prematurely detonated one of two sets of pyrotechnic charges that were used to split apart the lattice structure that held the Blok I upper stage to the Blok A core stage during ascent. This premature firing also severed the electrical connections to the remaining charges needed to fully separate the two stages. So when the time came for the Blok I stage to fire and pull away from the spent Blok A, the stages were still partially attached to each other causing the rocket to deviate off course and set off the automatic abort system. The upcoming ASTP mission (as well as subsequent manned Soyuz missions for the next 27 years) would use the newer Soyuz-U 11A511U launch vehicle which, according to Soviet authorities, had a different separation system design that could not suffer from this sort of malfunction. As for the crew, Makarov went on to fly on the Soyuz 27 and T-3 missions to Salyut 6 in 1977 and 1980, respectively. Reports indicate that Lazarev apparently had experienced internal injuries during the high-G emergency descent and he never returned to flight status.

The Soyuz T-10-1 Launch Pad Abort

The Soyuz, like the earlier American Mercury and Apollo spacecraft, has an LES that uses a solid rocket motor on top of the spacecraft to pull the capsule carrying the crew from the launch vehicle in case of a malfunction during the earliest phases of the mission. The only time an LES was employed operationally on a crewed flight (for the second launch abort of a crewed space mission) was on September 26, 1983 for a mission that was originally to have been called “Soyuz T-10”. The objective of this mission was to carry cosmonauts Vladimir Titov, the mission commander, and Gennady Strekalov, the flight engineer, to the Salyut 7 space station to relieve the long-duration crew brought up on Soyuz T-9. Titov and Strekalov along with a third crewmember, Alexander Serebrov, had originally flown on the Soyuz T-8 mission launched the previous April but were unable to dock with Salyut 7 because of a failure of their rendezvous radar. After their return, Titov and Strekalov were quickly recycled to the top of the flight roster to take advantage of their training for the new mission.

The crew of Soyuz T-8: (l to r) Alexander Serebrov, Vladimir Titov and Gennady Strekalov.  After they failed to dock with Salyut 7, Titov and Strekalov were reassigned to the ill-fated Soyuz T-10-1 launch attempt later in 1983.

For this flight, Soyuz 7K-ST number 16L was to be launched into orbit from Launch Complex 1 by the Soyuz-U 11A511U launch vehicle serial number Yu15000-363. Titov and Strekalov boarded their spacecraft, identified by the call sign “Proton”, at around 21:00 Moscow Time for a nighttime launch scheduled for 23:38 to the Salyut space station. With just 90 seconds to go before launch, a valve on the launch pad supplying fuel to the boosters of the Soyuz-U failed to close resulting in a spill around the base of the rocket. Within a minute, the spilled kerosene fuel ignited and a fire started on the pad. By the time the launch director noticed the flames through his blockhouse periscope, the fire had already burned through the ground command lines that were used to activate the LES. A backup system using a radio link that relied on a simultaneous command from two different locations (an arrangement used to minimize the chances of an unintended abort command being accidentally sent) had to be used.

A still from a video showing the Soyuz T-10-1 being engulfed in flames on the pad seconds before its LES was activated pulling the crew to safety.

About ten seconds after the fire was first noticed, the abort command was finally sent followed 1.2 seconds later by the LES being activated. The descent and orbital module above it were separated from the launch vehicle and the solid rocket motor generating 785 kilonewtons of thrust fired as flames engulfed the Soyuz launch vehicle. Some three or four seconds later, the Soyuz-U toppled over and exploded causing much damage to the launch pad. In the mean time, the LES with the Soyuz orbital/descent modules had accelerated to Mach 1 in just five seconds subjecting the crew to peak acceleration of 14 to 17 Gs. Once at an altitude of 950 meters, aerodynamic brakes were deployed and the descent module was released from the launch shroud. The reserve parachute was immediately deployed for the descent to the ground. Titov and Strekalov landed softly four kilometers from the burning launch pad where they were quickly rescued by recovery crews. The aborted flight of Soyuz T-10-1, as it was officially designated by the Soviets (and frequently referred to as “Soyuz T-10A” in the West), had come to a quick, but safe end.

It would be another month before Soviet authorities revealed the launch pad abort and more details followed in the years to come especially after the Challenger disaster. With no replacement crew coming, the crew of Soyuz T-9 remained on Salyut 7 until November 23, 1983 – a 150-day mission that exceeded the nominal 100-day orbital life of the Soyuz T spacecraft prompting unfounded rumors in the West of the crew being stranded in orbit. A replacement crew of three cosmonauts was finally sent to Salyut 7 on Soyuz T-10 launched on February 2, 1984. In the meantime, work began to repair Launch Complex 1 at the Baikonur Cosmodrome after it was heavily damaged by the Soyuz-U explosion. As for the crew of Soyuz T-10-1, Titov would next fly to command the Soyuz TM-4 mission to the Mir space station in 1987.  Strekalov would fly as a flight engineer on the Soyuz T-11 mission to Salyut 7 on April 11, 1984. After three attempts in less than twelve months, Strekalov would finally reach Salyut 7 to spend a week visiting the long-duration crew in orbit. Both men would continue their space careers including participating in American Space Shuttle flights to the Russian Mir space station.

A short video of the accident can be viewed below:

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Related Reading

“Rendezvous in Space: The Gemini 6 Launch Abort”, Drew Ex Machina, December 12, 2015 [Post]

“A History of Suborbital Crewed Spaceflights”, Drew Ex Machina, May 5, 2016 [Post]

General References

Phillip Clark, The Soviet Manned Space Program, Orion Books, 1988

Edward Clinton Ezell and Linda Neuman Ezell, The Partnership: A NASA History of the Apollo-Soyuz Test Project, Dover Publications, 2010

Rex D. Hall and David J. Shayler, Soyuz: A Universal Spacecraft, Springer-Praxis, 2003