posted 08-24-2017 09:09 AM
This is a summary of the uncrewed flight tests prior to Soyuz 1.The Soyuz program, years behind its original schedule, was now working towards the unrealistic objectives of a manned lunar circumnavigation in 1967, followed by a manned moon landing in 1968. Two Soyuz versions were in development for these tasks: the three man 7K-OK Earth orbital craft, and the two man 7K-L1 version (later publicly known as Zond 4 to 8). Different groups of cosmonauts were assigned to each spacecraft type.
The 7K-OK spacecraft themselves were divided into odd numbered passive, and even numbered active docking types. The first unmanned test vehicle 7K-OK no. 1 commenced ground tests in May 1966. These ran on for 112 days instead of the planned 13 days, 2123 defects were discovered but it was still sent for launch preparation after "the review team's patience ran out" (Chertok). 7K-OK no. 2 in it's turn displayed about half this number of defects.
7K-OK no. 2 was inserted into orbit on Nov. 28, 1966. By the end of its first orbit it had depleted all of its attitude control hydrogen peroxide and was rolling out of control at two revolutions per minute. The remaining orbital life was used to conduct as many systems tests as practical before attempting return using the back-up engine. However, attitude control on this also malfunctioned. They resorted to attempting de-orbit by numerous short firings of the backup engine but the craft was destroyed by the APO system when it detected that landing would occur outside the USSR. It turned out that both the primary and backup means of attitude control had effectively been "phased" in reverse.
The launch of 7K-OK no. 1 was rescheduled for Dec. 14. The launch attempt was scrubbed when one first stage booster failed to ignite. The cause was investigated whilst the launch vehicle was still fully fueled. During this time the launch escape system (SAS) unintentionally automatically activated. The 7K-OK descent module made a normal soft landing about 500 yards away but a fire was started in the launch vehicle. The vehicle exploded, destroying the launch facility and killing one member of the ground crew.
On Feb. 7, 7K-OK no. 3 was launched. This again had (different) attitude control problems and numerous other glitches. Again a non-normal deorbit was performed followed by entry in the backup ballistic mode. The descent module landed on the Aral Sea and sank due to a burn through of the heat shield.
Despite these failures, they decided to resume the program with piloted launches after defect rectification. I think that the undisputed facts are as follows:
The plan was to launch 7K-OK no. 4 with a single cosmonaut. The next day 7K-OK no. 5 would be launched with a crew of three. 7K-OK no. 4 would conduct an automatic rendezvous to around 200 yards and the pilot would then dock manually with the other craft. An EVA transfer of two cosmonauts from vehicle 5 to vehicle 4 would then be performed. The craft would then undock and land individually having once more upstaged the Americans. As each vehicle was successfully inserted into orbit they would assume the public designations of Soyuz 1 for 7K-OK no. 4 and Soyuz 2 for 7K-OK no. 5.
Three days prior to the first launch the crew assignments were made: Komarov as commander of 7K-OK no. 4 with Yuri Gagarin as his backup; and Valery Bykovsky (commander), Aleksei Yeliseyev and Yevgeny Khrunov for 7K-OK no. 5.
On April 23, 1967, Soyuz 1 piloted by Komarov was inserted into an approximatey 110 nautical mile near circular orbit. The left solar array failed to deploy, and the right array operated below design efficiency leaving the craft critically low on electrical power and endurance. In addition, both the 45K sun/star and ionic orientation systems failed.
The crew of 7K-OK no. 5 were re-tasked to rendezvous with and conduct EVA repairs of Soyuz 1, but this was subsequently cancelled due to thunderstorms at the launch site. Eventually, with the craft almost out of electrical power reserves, Komarov successfully used an untrained ad hoc emergency procedure sent up by the ground to deorbit. The last confirmed radio contact with Komarov occured after he calmly confirmed descent module separation. The retro-fire problems resulted in a default to backup ballistic reentry.
After a successful reentry, the soft landing systems failed and the descent module impacted the ground at around 90 mph approximately 2 miles west of Karabutak in southern Russia. Komarov died on impact. The wreckage and body were severely distorted by a post-crash fire.
The investigation determined the final accident sequence to be as follows:
The main parachute container cover was jettisoned, presumably at the nominal altitude of around 31,000 feet. This deployed the pilot chute which in turn extracted the drag chute. This chute was designed to reduce the descent velocity so that the main chute would not be damaged by excessive air loads, and to extract the main chute which would then deploy.
However, the main chute remained in its container with the drag chute deployed in the airflow. At around 18,000 feet altitude a barostatic instrument measuring detected excessive rate of descent and commenced deployment of the reserve parachute system. Part of this sequence was to release the main canopy, but since it was still in it's container, this step failed. The reserve parachute was extracted but failed to inflate in the disturbed airflow caused by the main drag chute, and the two may have subsequently become entwined. The high rate of descent meant that the front heat shield was only jettisoned just above the surface, and the soft landing rockets fired after impact.
The cause of the main parachute deployment failure was officially put down to deformation of the parachute container structure resulting from the pressure differential between the pressurised descent module interior and the atmosphere. Chertok subsequently provided a hypothesis that fits all known facts much better. A manufacturing process error on both 7K-OK no. 4 and no. 5 resulted in excessive roughness of the inside of the main parachute container surfaces. The force required to extract the chute was greatly in excess of that which the drag chute was designed to produce. If the launch of 7K-OK no. 5 had not been cancelled, that crew would also have perished on landing.
posted 08-24-2017 09:06 AM
advertisement