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Sputnik launch vehicle (8K71/8A91)


The version of the R-7 rocket that was destined to carry the first satellite into orbit was designated 8K71PS No. M1-1PS. That particular vehicle received several upgrades deferring it from earlier experimental R-7 rockets. (52) Along with the military warhead, gone were measurement hardware, top avionics section containing the vibration monitoring system, cables connecting the rocket and the warhead and a considerable portion of the flight control hardware, including the radio-control system. Some of the onboard electric batteries were also removed. (51) As a result, the total mass of the rocket went down from 280 tons for the original R-7 rocket to 272.83 tons (or 267 tons, at the time of liftoff) for the space launcher. At liftoff, the engines would reach the total thrust of around 398 tons. (256, 52)

Upon reaching the orbit, the main engine cutoff had to be performed by the gyroscopic integrator or on a command from the emergency contact of the turbine in the main engine. Such command would be issued as soon as the rocket run out of fuel or oxidizer.

All tracking of the rocket in flight had to be conducted passively by means of radar, without onboard response, and with the help of ground telescopes. Both ways had a limited range and accuracy. Based on experience with the previous launch of the R-7 rocket, ground controllers expected the Binokl (binocular) tracking system to "see" no further than 200 kilometers for the rocket, and much less for a satellite. In the meantime, the P-30 radar demonstrated an effective range of 500 kilometers, when tracking aircraft. Its effectiveness would be further reduced by a relatively slow rotation of its antenna. Optical sensors Kth-41 and KT-50 available in Tyuratam at the time had a range of 100-200 kilometers, also too short for effective tracking of a satellite. (51)

Modifying the rocket for Sputnik-2

For the launch of the second satellite, the second braking nozzle was added to the core stage of the rocket to prevent tumbling of the vehicle upon entering orbit. (248) As in the rocket launching the first satellite, the braking nozzle would employ gas, which pressurized oxidizer tank during the powered flight. (84)

Once in orbit, a special programming device, installed on the core stage would switch the Tral-Ts telemetry system from transmitting the parameters of the rocket to channel data from scientific payloads. (52)

To help maintain proper temperature in the dog cabin, the transfer cone, which connected the satellite with the rocket, was thoroughly polished, additional thermal blanket were added and copper panels were installed on the telemetry boxes. The core stage was also equipped with deployable reflectors.

To maximize scientific payload of Sputnik-2, some flight control equipment was removed from the rocket. For the same purpose, the flight profile was modified to ensure maximum use of onboard propellant. It was achieved by programming the flight control system to shut down the main engine only when its turbo pump detects that it run out of either propellant or oxidizer. In the previous launch, this way of shutting down the engine was only a backup mode.

The rocket for Object D: 8A91

By the time the third Soviet orbital mission was prepared to fly, a new version of the R-7 launch vehicle designated 8A91 was also in works. It was a transitional upgrade between the older 8K71 ballistic missile and the yet-to-be-tested lighter 8K74 ICBM designed for a longer range. Chemical milling was used to shave off some extra metal from waffle-like tank walls. In addition, the Tral-V telemetry system was removed from the first stage and its tasks of data transmission were transferred to a single Tral unit on the second stage. (537)

Mass changes led to a different flight profile. The engine of the core stage would be throttled down from 73 tons to 60 tons, while strap-on boosters would be throttled up 25 percent 17 seconds before their separation. Also special covers would be introduced to reduce the backward thrust of separation nozzles. The radio-equipment bay was replaced with an adapter section.

The development of the 8A91 launch vehicle was completed by the beginning of 1958. (84)


Technical specifications of the R-7 ICBM and Sputnik launcher:

8K71 (M1-5) test version ICBM
Sputnik launcher 8K71PS (M1-1PS)
Number of stages
Length of the vehicle
  • 28 meters (without warhead or upper stages)
  • 31.07 meters (an original R-7 8K71 ICBM with a warhead) 34,290 mm (248)
29,167 mm (51, 256, 137, 248)
10.3-11.2 meters at the base of four strap-on boosters
10.3 meters at the base, including stabilizers span. (137)
Launch mass (fueled)
280 tons (empty weight: 27 tons); 274.2 tons (248)
272.83 tons (256) (267.13 tons at liftoff) (51, 248)
Fuel (all stages)
Kerosene T-1
Kerosene T-1
Oxidizer (all stages) Liquid Oxygen Liquid Oxygen
Total thrust 396.9 tons 396.9 tons
Mass of propellant 253 tons 253 tons
Dry mass - 22 tons (137)
Maximum payload

5,375 kg (warhead on sub-orbital trajectory)

83.6 kg (4)
First launch 1957 May 15 1957 Oct. 4
Launch sites Tyuratam (two pads), Plesetsk (four pads) Tyuratam (Pad 1)
Stage I: Four strap-on boosters (Block B, V, G, D)
Stage I mass

168.9 tons (248)

168.0 tons (248)
Stage I propellant mass

153.2 tons(248)

153.2 tons (248)
Stage I length

19.2 m; 19.6 m (248)

19.6 m (248)
Stage I diameter 2.68 m 2.68 m
Stage I burn time 104-130 seconds; 120 seconds (248) 120 seconds (248)

Stage I propulsion
(each of four strap-on boosters has):

  • 1 x four-chamber main engine RD-107 (8D74)
  • 2 x one-chamber steering engines
  • 1 x four-chamber main engine RD-107 (8D74PS)
  • 2 x one-chamber steering engines
Stage I thrust (at liftoff)

80.9 tons each of four strap-ons (248)

80.9 tons each of four strap-ons (248)
Stage I thrust (in vacuum)

99.4 tons each of four strap-ons (248)

99.4 tons each of four strap-ons (248)
Stage I specific impulse (sea level)

247.6 seconds (248)

247.6 seconds (248); approximate. 250 seconds (137)
Stage I specific impulse (in vacuum

304.3 seconds (248)

304.2 seconds (248)
Liquid oxygen consumption

218.4 kg per second (248)

218.4 kg per second (248)
Kerosene consumption

88.3 kg per second (248)

88.3 kg per second (248)
Stage II: Core stage (Block A)
Stage II mass (fueled)

93.36 tons; 99.9 tons (248)

99.1 tons (248)
Stage II propellant mass

91.6 tons (248)

91.8 tons (248)
Stage II dry weight

6.465 tons

7.5 tons (51)
Stage II length

28 m; 26.9 m (248)

26.0 m (248)
Stage II diameter 2.95 m 2.95 m (248)
Stage II burn time 285-320 seconds; 300 seconds (248) 300 seconds (248)
Stage II propulsion 1 x four-chamber RD-108 (8D75) (248) 1 x four-chamber RD-108 (8D75PS) (248)
Stage II thrust

93.2 tons (248)

93 tons (137); 93.2 tons (248)
Stage II specific impulse (at liftoff)

239.1 seconds (248)

239.1 seconds (248)
Stage II specific impulse (in vacuum)

303.1 seconds (248)

303.1 seconds (248)
Liquid oxygen consumption

202.7 kg per second (248)

202.7 kg per second (248)
Kerosene consumption

84.8 kg per second (248)

84.8 kg per second (248)



This page is maintained by Anatoly Zak

Last update: May 8, 2019

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A payload fairing of the first simplest satellite (Sputnik-1). Copyright © 2011 Anatoly Zak


Payload section of the Sputnik launcher for the first orbital mission. Credit: RKK Energia


The first artificial satellite of the Earth blasts off from Site 1 in Tyuratam (Baikonur) at 22:28 Moscow Time on October 4, 1957. Credit: RKK Energia

Sputnik launch

The artist impression of the first Sputnik launch. Click to enlarge. Copyright © 2007 Anatoly Zak


Second stage of the launch vehicle with the first satellite shortly after reaching the orbit. Click to enlarge. Copyright © 2007 Anatoly Zak

Sputnik-2 rocket

The R-7 rocket configured to carry the second satellite of the Earth. Click to enlarge. Copyright © 2007 Anatoly Zak

Sputnik-2 on launch pad

The launch vehicle with the second Soviet artificial satellite on the launch pad in Baikonur. Credit: RKK Energia


Scale model of the Sputnik launcher on its original pad in Baikonur. Copyright © 2005 Anatoly Zak