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Zenit was the first new Soviet launcher developed since the unsuccessful N1 of 1969-72 and provides a payload capability between those of Proton/Soyuz. Its first stage was developed in parallel with Energia's strap-ons (designated Zenit 1). Principal payloads in the early program are heavy electronic intelligence satellites but Space Station supply modules and manned spacecraft could be users. A new cryogenic stage 3 was designed for Zenit 3 but discarded in favor of the existing Proton Block DM (which will be used by Sea Launch's Zenit 3SL version).


First launch: 13-Apr-1985 (sub-orbital)
Number launched: 26 to end-1995
Launch sites: Tyuratam, Plesetsk (expected operational 1997)
Principal uses: Tselina 2 elint, Resurs-O, Kuban; potential: commercial, Advanced Okean, super-Progress, manned to LEO
Vehicle success rate: 76.9% to end-1995
Zenit 2: 13,740 kg into 200 km 51.6o, 11,380 kg into 200 km 99o, both from Tyuratam; 15,700 kg into 200 km 12o for equatorial site
Zenit 3 capabilities from Tyuratam: 5,370 kg GTO, 1,600 kg GEO
Cost: R23 billion quoted Oct-1995
Number of stages: 2 (3 for Zenit 3)
Overall length: 57.00 m including 13.65 m fairing (61.40 m Zenit 3); 11.155 m fairing available
Principal diameter: 3.90 m
Launch mass: 449,000 kg without payload (466,000 kg Zenit 3)
Launch thrust: 7,259 kN sea level (7,622 kN SL Zenit 3)
Guidance: inertial. 1 Mbit/s telemetry provides information on 1,000 parameters during launch. Receives navigation update just before launch via laser optical receiver package mounted on side; package is then blown free

Engines: RD-171 from NPO Energomash, four gimbaled chambers. RD-172 will be used on Zenit 3 (5% thrust increase)
Length: 32.94 m
Diameter: 3.90 m
Dry mass: 28,080 kg
Oxidizer: liquid oxygen
Fuel: kerosene
Propellant mass: 318,800 kg
Thrust: 7,911 kN vac, 7,259 kN SL
Burn time: about 144 s
Separation: four retro solids at aft end

Engines: NPO Energomash RD-120 single fixed reignitable chamber with four gimbaled NPO Yuzhnoye verniers for steering
Overall length: 11.50 m
Diameter: 3.90 m
Dry mass: 8,300 kg
Oxidizer: liquid oxygen
Fuel: kerosene
Propellant mass: 80,600 kg
Thrust: 833.5 kN vac main + total 78.4 kN vac verniers
Burn time: about 300 s total, verniers can burn for up to 1,100 s
Separation: four retro solids at aft end

NPO ENERGOMASH / RD-170, RD-171, RD-172
There are only minor differences between Energia's RD-170 and Zenit's RD-171; for example, 2-axis gimballing for Zenit and 1-axis for Energia. Development of the improved RD-172 for Zenit 3 was expected to achieve certification in 1996. A 5% thrust increase is provided by a chamber pressure of 255.4 atm.
Designation: 11D520 (Energia's RD-170), 11D521 (Zenit's RD-171)
Configuration: four gimbaled chambers (two pairs)
Application: SL-16 Zenit stage 1, SL-17 Energia strap-ons
First flown: 13-Apr-1985
Dry mass: 8,755 kg
Length: 3.56 m
Maximum diameter: 3.99 m
Engine cycle: staged combustion
Oxidizer: liquid oxygen, delivered at 432 kg/s
Fuel: kerosene, delivered at 166.2 kg/s
Mixture ratio: 2.60
Feed method: 190 MW, 14,500 rpm turbopump for each chamber pair driven by pre-burners
Thrust: 7,904 kN vac, 7,257 kN SL (but can be throttled back to 4,413 kN vac) for SL-17 Energia; 7,911 kN vac and 7,259 kN SL for Zenit 2/3
Specific impulse: 308 s SL, 336 s vac for SL-17; 337 s vac for SL-16
Expansion ratio: 36.8:1
Combustion chamber pressure: 242 atm; 250 atm max
Burn time: 140-150 s

Designation: 11D123
Configuration: single fixed chamber + four NPO Yuzhnoye RD-8 verniers for steering
Application: SL-16 Zenit stage 2
Dry mass: 1,125 kg
Length: 3.87 m
Maximum diameter: 1.95 m
Engine cycle: closed gas generator
Oxidizer: liquid oxygen, delivered at 175.4 kg/s
Fuel: kerosene, delivered at 64.5 kg/s
Mixture ratio: 2.72
Feed method: 19,000 rpm turbopump; gas generator 462oC
Thrust: 834 kN vac (throttling -8.5/+3.5%)
Specific impulse: 350 s vac
Expansion ratio: 106:1
Combustion chamber pressure: 160.6 atm
Burn time: 200-315 s

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