Zenit (Ukrainian:Зеніт,Russian:Зени́т; meaningZenith) was a family of spacelaunch vehicles designed by theYuzhnoye Design Bureau inDnipro,Ukraine, which was then part of theSoviet Union. Zenit was originally built in the 1980s for two purposes: as aliquid rocket booster for theEnergia rocket and, equipped with a second stage, as a stand-alone middle-weight launcher with a payload greater than the 7 tonnes of theSoyuz but smaller than the 20 tonnes payload of theProton. The last rocket family developed in the USSR, the Zenit was intended as an eventual replacement for the dated Soyuz and Proton families, and it would employ propellants which were safer and less toxic than the Proton's nitrogen tetroxide/UDMH mix. Zenit was planned to take over crewed spaceship launches from Soyuz, but these plans were abandoned after thedissolution of the Soviet Union in 1991.

Zenit

Zenit-2 rocket (Baikonur, 10 December 2001)
Function	Medium-liftexpendablecarrier rocket
Manufacturer	Yuzhnoye (design) Yuzhmash (manufacturing)
Country of origin	Zenit-2:USSR,Ukraine Zenit-3SL:Ukraine
Size
Height	57–59.6 m (187–196 ft)
Diameter	3.9 m (13 ft)
Mass	444,900–462,200 kg (980,800–1,019,000 lb)
Stages	2 or 3
Capacity
Payload toLEO
Mass	Zenit-2: 13,740 kg (30,290 lb)
Payload toSSO
Mass	Zenit-2: 11,380 kg (25,090 lb)
Payload toGTO
Mass	Zenit-3SL: 6,000 kg (13,000 lb)
Launch history
Status	Suspended
Launch sites	BaikonurLC-45 Odyssey (ocean platform)
Total launches	84 36 Zenit 2 36 Zenit 3SL 2 Zenit 2M 6 Zenit 3SLB 4 Zenit 3F
Success(es)	71 28 Zenit 2 32 Zenit 3SL 2 Zenit 2M 5 Zenit 3SLB 4 Zenit 3F
Failure(s)	10 7 Zenit 2 3 Zenit 3SL
Partial failure(s)	3 1 Zenit 2 1 Zenit 3SL 1 Zenit 3SLB[1]
First flight	Zenit 2: 13 April 1985 Zenit 3SL: 28 March 1999 Zenit 2M: 29 June 2007 Zenit 3SLB: 28 April 2008 Zenit 3F: 20 January 2011
Last flight	Zenit 2: 10 June 2004 Zenit 3SL: 26 May 2014 Zenit 2M: 8 November 2011 Zenit 3SLB: 31 August 2013 Zenit 3F: 26 December 2017
First stage
Powered by	1RD-171
Maximum thrust	8,180 kilonewtons (1,840,000 lbf)
Specific impulse	337 seconds (3.30 km/s)
Burn time	150 seconds
Propellant	RP-1 /LOX
Second stage
Powered by	1RD-120 1RD-8
Maximum thrust	912 kilonewtons (205,000 lbf) 79,500 newtons (17,900 lbf)
Specific impulse	349 seconds (3.42 km/s)
Burn time	315 seconds
Propellant	RP-1/LOX
Third stage (Zenit-3SL/3SLB) –Block DM-SL
Powered by	1RD-58M
Maximum thrust	84,900 newtons (19,100 lbf)
Specific impulse	352 seconds (3.45 km/s)
Burn time	650 seconds
Propellant	RP-1 /LOX
Third stage (Zenit-3F) –Fregat-SB
Powered by	1S5.92
Maximum thrust	19,600 newtons (4,400 lbf)
Specific impulse	327 seconds (3.21 km/s)
Burn time	877 seconds
Propellant	N2O4 /UDMH
[edit on Wikidata]

Many of components of the Zenit rockets were produced in Russia. The Ukrainian space industry was highly integrated with that of Russia due to its Soviet heritage, but that cooperation was interrupted by theRusso-Ukrainian War beginning in 2014, which has effectively led to a hiatus in the Zenit program.^[2] The subsequentRussian invasion of Ukraine in 2022 saw damage to its manufacturing facilities due to Russian missile strikes, and what survived those strikes pivoted to producing military weapons.^[3]

Zenit-3SL was launched by theSea Launch consortium's floating launch platform in thePacific Ocean and Zenit-2 was launched fromBaikonur Cosmodrome inKazakhstan.RD-171M engines of the Zenit's first and second stages as well as the upper stage of the Zenit-3SL rocket were supplied by Russia. An improved Zenit-3SLB rocket was used for commercial launches from Baikonur Cosmodrome beginning in April 2008, marketed asLand Launch.^[4]

Zenit-3SL was launched 36 times with 32 successes, one partial success, and three failures. The first failure, the launch of aHughes-built communications satellite owned byICO Global Communications, occurred during the second commercial launch on March 12, 2000, and was blamed on a software error that failed to close a valve in the second stage of the rocket. The second failure occurred on January 30, 2007, when the rocket exploded on theOdyssey launch platform, seconds after engine ignition. TheNSS-8 communication satellite on board was destroyed.^[5]

On September 24, 2011Zenit-3SL launched successfully from theOdyssey launch platform under a renewedSea Launch project withRSC Energia as the majority stakeholder. The rocket delivered the European communication satellite Atlantic Bird 7 to its planned orbit. On February 1, 2013, another Zenit-3SL failed while launching theIntelsat 27 satellite.^[6]

The Zenit-2 was the first Zenit to be designed for use as an orbital carrier rocket. It consists of two stages. The first uses anRD-171 engine, and anRD-120 engine powers the second stage. It first flew on 13 April 1985, two years before the Energia, due to delays relating to the Energia's development.^{[citation needed]} Zenit-2 would be certified for crewed launches and placed in specially builtlaunch pad atBaykonur spaceport, carrying the new crewed partially reusableZarya spacecraft that developed in end of the 1980s but was canceled. Also in the 1980sVladimir Chelomey's firm proposed never realised 15-tonUragan spaceplane launched by Zenit-2.

Two launch facilities were constructed for the Zenit at Baikonour, however the second was only ever used twice. On October 4, 1990, an attempted launch of a Tselina-2 naval reconnaissance satellite ended in disaster as the booster suffered a first stage engine failure seconds into launch and fell back onto the pad, which was severely damaged in the ensuing explosion. The failure was traced to a leak in a LOX line that caused a fire in the thrust section of the booster. Estimated repair costs were about 45 million rubles, but the collapse of the Soviet Union meant that there were no funds available, so the pad was abandoned.

Following two failures in 1991–92 both caused by the second stage, the Zenit was on the verge of being cancelled entirely, but a successful flight in November 1992 saved the program.

The rate of Zenit launches slowed to a trickle during the 1990s due to the severely cash-strapped Russian Federation, and also because of Russia's reluctance to fly military payloads on a booster manufactured in now-independent Ukraine. On May 20, 1997, a launch of a Tselina-2 satellite failed when the first stage shut down 48 seconds into launch. The booster crashed downrange.

During the 2000s, Zenit would find a new lease on life as the basis of the international Sea Launch project whereby commercial flights would be undertaken from an offshore launch platform. The basic Zenit booster received several upgrades to the propulsion and avionics systems for Sea Launch as well as a third stage, and the first test with a dummy payload was carried out on March 27, 1999. In October, a Direct TV 1-R satellite was orbited successfully. An ICO F-1 comsat was lost in March 2000 due to a second stage guidance malfunction. There followed eight consecutive successful launches until Apstar 5 in 2004 suffered a premature third stage shutdown that left it in an incorrect orbit, but the satellite's onboard engines corrected it.

After nine successful launches, the Zenit produced a repeat performance of the 1990 disaster when on January 30, 2007, the first stage lost thrust and exploded. The flame deflector on the Sea Launch platform broke off and sank into the water. Loose debris had been sucked into a turbopump, resulting in engine failure.

By the late 2000s, the Zenit program at Baikonour was reviving and would see considerable success.

On February 1, 2013, an Intelsat satellite launched from the Sea Launch Odyssey platform in the equatorial Pacific. The nighttime launch performed nominally for about 20 seconds when the first stage abruptly lost thrust. Approximately 40 seconds after liftoff, all telemetry data ceased. Subsequent investigation showed that the Zenit had begun deviating from its flight path when the pitch and roll maneuver started. The onboard computer sensed an abnormal situation and sent an automatic shutdown command to the first stage at T+23 seconds, and impact with the ocean occurred about one minute after liftoff. Ultimately, the failure was traced to a defective hydraulic pump that controlled gimbaling of the first stage engines. This resulted in the booster starting an uncontrolled rolling motion which caused the computer system to terminate all thrust. Although anomalous conditions began around T+11 seconds, the Zenit's flight computer was "locked" to prevent engine shutdown until at least 20 seconds after liftoff so the booster would not come down on or near the launch complex. Impact occurred about two miles downrange, but attempts to recover booster debris were unsuccessful.

In February 2015, following a year of strained relations as a result of aRussian military intervention into Ukraine, Russia announced that it would discontinue its "joint program with Ukraine to launchDnepr rockets and [was] no longer interested in buying Ukrainian Zenit boosters, deepening problems for [Ukraine's] space program and its strugglingYuzhmash factory."^[7]

Strained relations between Ukraine and Russia after 2014 have led toRussian Federal Space Agency intending to purchase no more of the Zenit first-stage boosters made by Yuzhmash (powered by Russian engines). However 2 Zenit rockets that have been delivered to Russia forRussian Federal Space Agency missions will still be used; another Zenit rocket for launching a Ukrainian satellite has been completed but without engines due to lack of funding for payments.^[8] The world market for Zenit launch vehicles has shriveled since Sea Launch suspended operations, and the future of Zenit is uncertain.^[9]

Despite the ongoing conflict between the two governments, a Zenit rocket was launched in December 2017, after a two-year hiatus, to deliverAngoSat 1.^[10]

The first and the second stages of the Zenit were designed by Yuzhnoye and are manufactured byYuzhmash.^[11]

The Zenit-2 was the first member of the rocket family. It consists of two stages. The first uses anRD-171 engine, and anRD-120 engine powers the second stage. It first flew on 13 April 1985, carrying aTselina-2 mass simulator. However the test flight was unsuccessful. The first successful flight occurred on 22 October 1985.

The Zenit first stage was used as a strap-on booster rocket for theEnergia carrier rocket.^[12] Four Zenit first stages were attached to the core vehicle to produce extra thrust at lift-off, in the same way thatSolid Rocket Boosters were used on the USSpace Shuttle. Energia made two flights (1987 and 1988) before the programme was abandoned.

Zenit 2M is a new version of the Zenit 2 with an upgraded control system and modernized engines.^[13] The first Zenit 2M was launched on June 29, 2007, carrying a classified Russian militaryTselina-2 satellite. The Zenit-2SLB designation applies to commercial launches through theLand Launch subsidiary of Sea Launch, which began satellite launches from Baikonur Cosmodrome in 2008.^[4]

Zenit-3SL is a three-stagecarrier rocket developed for and used by the Sea Launch consortium.

It combines:^[14]

• two-stage Zenit-2S built byUkraine's SDOYuzhnoye/POYuzhmash
• Block DM-SL upper stage, provided by Russia'sEnergia
• nose-cone enclosure for protection of payload during launch, provided byBoeing.

Rockets used by Sea Launch are assembled inLong Beach, California. Launches occur from theOcean Odyssey offshore launch platform, situated at the equator.Ocean Odyssey is also used to transport rockets to the launch site. Themost recent launch of a Zenit-3SL occurred on 11 December 2015. The RD-171 engine of the Zenit-3SL first stage, and most of the control system of -3SL missiles were made in Russia.^[15] However, according to the same source, it is not clear if Russia's component suppliers are still working together with Yuzhmash as of this date.

The Zenit-3M is a Zenit-2M with theBlock-DM upper stage used on the Zenit-3SL. It is launched from Baikonur. The maiden flight was launched on 28 April 2008.Land Launch commercially market the Zenit-3M under the designation Zenit 3SLB.^[4]

The Zenit-3F, also known as the Zenit-2SB/Fregat, is a 3-stage derivative of the Zenit-2M, using aFregat upper stage, as already used on theSoyuz, to propel spacecraft to higher orbits. It made its maiden flight in January 2011, with theElektro-L No.1 spacecraft for the Russian government. Later the same year, another launch carriedSpektr-R, a 5,000-kilogram (11,000 lb)space telescope, into an orbit with aperigee of 10,000 kilometres (6,200 mi) and anapogee of 390,000 kilometres (240,000 mi).^[16] The most recent launch occurred on 26 December 2017 from Baikonur Cosmodrome when the rocket lifted off with the Angolian Angosat 1 spacecraft.^[17]

• Comparison of orbital launcher families
• Tsyklon-4
• State Space Agency of Ukraine

• Zenit Family
• Information at Encyclopedia Astronautica
• Information at National Space Agency of Ukraine
• Information at Buran web site
• Information at Orbital Report News Agency