Soyuz-U was in use continuously for almost 44 years. Production of R-7 derived launch vehicles peaked in the late 1970s-early 1980s at 55–60 a year. Soyuz-U held the world record of highest launch rate in a year in 1979 with 47 flights until this was beaten by SpaceX's Falcon 9 in 2022.[10][11] Over its operational lifetime, the Soyuz-U variant flew a total of 786 missions, another world record. Soyuz-U has also been one of the most reliable launchers, with a success rate of 97.3%.
Development
The earlier Soyuz 11A511 was the first attempt at creating a standardized R-7 core in place of the numerous variations that had been used up to 1966. It took the first stage from the Molniya 8K78M booster with the 8D74M engines and made them standard across the board for all R-7 vehicles. In addition, Soyuz vehicles would all use the RD-0110 engines from the 8K78M's Blok I stage, although Voskhod vehicles retained the older, less powerful RD-0107 engines.
The uprated core (GRAU index 11A511U) was introduced to the R-7 family in 1973, yielding the carrier rocket variant named Soyuz-U, although adoption across the board was not complete until 1977 when the existing stock of 11A511-derived boosters was used up. The 11A511U was similar to the 11A511 but had some improvements to the engines to cut down on issues such as in-flight vibration and combustion instability and the instrument packet was shortened on three stage variants while the four stage Molniya booster continued using the older, longer instrument packet from the 11A511.
Versions
Two versions of Soyuz-U were fitted with an additional upper stage:
Soyuz-U/Ikar with the Ikar third stage, produced by the Progress State Research and Production Rocket Space Center, TsSKB-Progress. Ikar is used to deliver various payloads with masses of 750 to 3,920 kg (1,650 to 8,640 lb) to heights of 250 to 1,400 km (160 to 870 mi). The performance of the Ikar upper stage is lower than that of the Fregat upper stage, but it is more precise in maneuvering and it can operate autonomously longer. This version was launched 6 times in 1999, carrying four GlobalStar satellites on each mission.[3]
Soyuz-U/Fregat with the Fregat third stage, developed and produced by Lavochkin Association in Khimki. This version only flew 4 times in 2000;[4] the Fregat upper stage was subsequently flown regularly atop Soyuz-FG and Soyuz-2 boosters.
An older variant of Soyuz-U, the Soyuz-U2 launcher, first flown in 1982, had the same hardware as the basic Soyuz-U. Instead of standard RP-1, it used a high energy, synthetic version, Syntin, as the first stage fuel. This variant, mainly used to transport crew and cargo to the Mir space station, last flew in 1995, after production of Syntin ended due to cost reasons.
Soyuz-U was the basic platform for the development of the Soyuz-FG variant, which used an all-new first stage and took over crew transport to the ISS in 2002. Since 2013, both Soyuz-U and Soyuz-FG are gradually being replaced by the modernized Soyuz-2 launch vehicle.
Human spaceflight
The first use of a Soyuz-U to launch a crewed mission took place 2 December 1974, when the Soyuz 16 crew was launched in preparation for the Apollo–Soyuz Test Project (ASTP). Soyuz 19, which as part of the ASTP docked with the last Apollo spacecraft ever flown, was also launched by a Soyuz-U rocket.[6]
On 6 July 1976, a Soyuz-U launched Soyuz 21, which took a crew of two to the Salyut 5 space station. Many subsequent space station crews were launched on Soyuz-U launchers. The final crewed mission to use the Soyuz-U was Soyuz TM-34, a Soyuz ferry flight to the International Space Station.
A spectacular accident occurred on 26 September 1983, when the launcher for the Soyuz T-10a mission was destroyed by fire on the launch pad. The crew was saved by activation of the launch escape system a few seconds before the explosion.
Although the Soyuz-U was generally reliable, occasional failures occurred, most of them on launches of Zenit and Yantar reconnaissance satellites. As with all Soviet/Russian launch vehicles, the 11A511U featured the AVD malfunction detection system which would terminate engine thrust in-flight if it detected a deviation from the booster's normal performance levels and on Soyuz launches also activate the launch escape system. The flight termination command could not be sent until 20 seconds into launch so the booster wouldn't fall onto or around the launch complex and the AVD could not generate a flight termination command until eight seconds to ensure the booster had entered stable mainstage operation. On June 18, 1987, a launch of a Resurs satellite from Plesetsk ended disastrously when the Blok D strap-on LOX turbopump disintegrated at T+6 seconds due to ingested debris. The booster crashed near the pad, badly damaging it and putting it out of use for 18 months. During investigation into the mishap, it was concluded that the launch would not have been survivable had it been manned because the failure occurred before the AVD system could have activated, and thus the launch escape system would not have worked on a manned launch.
It was also concluded that eight seconds was excessive and the booster would reach mainstage operation by about T+1.6 seconds; the AVD system had been designed in the late 1950s when only a few R-7 prototypes had flown and there was little flight data to go by. The AVD was redesigned to be able to issue a flight termination command at 1.6 seconds, which of course would still be blocked until T+20 seconds.
On July 27, 1988, the first R-7 vehicle with the redesigned AVD system launched from Plesetsk with another Resurs satellite. The AVD issued an erroneous shutdown command at T+1.6 seconds. The booster lifted and flew until T+20 seconds when the shutdown command was unblocked and terminated engine thrust, causing it to fall near LC-43/4 and severely damage it. An investigation into the mishap found that the new AVD system had a faulty circuit layout.
The October 2002 launch of a Foton satellite crashed near the pad at Plesetsk after the Blok D strap-on booster suffered an engine malfunction. One person on the ground was killed. The Blok D experienced an abnormally slow thrust rise at ignition followed by a decay in performance starting at T+4 seconds. The AVD system sensed the drop in Blok D performance and issued the flight termination command at T+5 seconds but it was blocked until T+20 seconds. The Blok D shut down completely and broke off the stack at T+8 seconds. The booster continued to climb but started deviating from its flight path due to the unbalanced thrust. The flight termination command was unblocked at T+20 seconds and the core and remaining strap-ons shut down. The booster impacted the ground at T+41 seconds as a crowd of 300 spectators watched. Six Russian military servicemen were injured and one later died of his injuries. A building used to produce compressed air and nitrogen was also badly damaged. Investigation into the mishap found that the Blok D's hydrogen peroxide pump had stopped working due to ingested debris.
A Soyuz-U mission failed to launch Progress M-12M to the ISS on 24 August 2011, when the upper stage experienced a problem and broke up over Siberia. It was the first time a Progress spacecraft had failed to reach orbit. Another cargo ship, Progress MS-04, was lost on 1 December 2016 shortly after launch, likely due to a problem with the third stage of the Soyuz-U.
In April 2015, Soyuz-U was declared obsolete. Its production was stopped and the rocket was scheduled for retirement after launching the remaining vehicles with Progress cargo ships.[12] The final flight was Progress MS-05, which launched from the Baikonur Cosmodrome on 22 February 2017, 05:58:33 UTC.[13]
References
^"Soyuz-U". Archived from the original on 11 December 2016. Retrieved 19 March 2022. Astronautix.com
^ abKrebs, Gunter. "Soyuz-U (11A511U)". Gunter's Space Page. Retrieved 22 February 2017.
^ abIn 1983, flight Soyuz T-10a took fire on the launch pad before the end of the countdown, so it is not counted in the list of launches; this is why adding successes and failures yields 787 launches instead of 786.
^ abcMark Wade (26 March 2001). "Soyuz 11A511U". Friends and Partners. Archived from the original on 4 March 2016. Retrieved 7 January 2009.
This Template lists historical, current, and future space rockets that at least once attempted (but not necessarily succeeded in) an orbital launch or that are planned to attempt such a launch in the future
Symbol † indicates past or current rockets that attempted orbital launches but never succeeded (never did or has yet to perform a successful orbital launch)
Uncrewed missions are designated as Kosmos instead of Soyuz; exceptions are noted "(uncrewed)". The † sign designates failed missions. Italics designates cancelled missions.
