Molnija (rocket)

Molnija-8K78M

A Molnija launcher on its way to the launch pad

The Molnija ( Russian Молния for lightning, English Molniya ) was a four-stage, Soviet or Russian rocket, which is specially designed for launching high-flying satellites and interplanetary space probes.

history

The development of the rocket goes back to the R-7 rocket, which was expanded to four stages for interplanetary missions or for high earth orbits. These signed Sergei Korolyov on 15 January 1960 a corresponding development contract and was in May 1960, the first draft. The first launch of a Molnija took place on October 10, 1960 in Baikonur , and since then it has been used to launch lunar, Mars and Venus probes until the end of the 1960s. Many early Molnija launches ended with the payload remaining in orbit that was too low. This was due to the error-prone technology of the fourth stage of the rocket. Molnija is no longer in use today and was often used from 1964 to the end of 2010 to launch its namesake (the Molnija communications satellite ) and military early warning satellites of the Oko type. It was built by ZSKB-Progress (Samara Space Center), the engines were supplied by Motorostroitjel (Samara) and the upper stage came from the Lavochkin design office (Moscow-Chimki). The Molnija was later considered to be one of the most reliable rockets in Russia, on June 21, 2005 it suffered the first false start since 1990 due to a fault in the second stage engine. It was only used commercially in 1995 when it hit the Indian earth observation satellite IRS-1C and the American military satellite Skipper put into orbit. Since the technology of the Molnija is already outdated and not flexible enough in use, it was gradually replaced by the more modern Soyuz Fregat . The last launch of a Molnija-M (built in 2005) took place on September 30, 2010, during which it brought the Kosmos 2469 satellite (an early warning satellite of the Oko type) into a highly elliptical (see Molnija orbit ) orbit. A total of 320 rockets were launched from Baikonur and Plesetsk into space. There were a total of 21 false starts, 7 of them in the first 15 starts.

technology

The first two stages of the Molnija ( GRAU index 8K78) correspond to those of the Vostok rocket, on the basis of which it was based. For the third stage, however, the Blok E of the Vostok was not used , but a more powerful rocket stage called the Blok I was developed, which was later also used in the Voschod and Soyuz . Blok I was of an RD-108 - four-chamber engine (actually for the R-9 was developed -Interkontinentalrakete) driven, the Kerosinart the RP-1 and liquid oxygen used (LOX) as fuel. In contrast to the Blok E, which is only half as long, it was given a spherical fuel container with three times the fuel capacity.

The fourth stage of the Molnija ( Blok L ) was based on the third stage of the Vostok rocket, also burned RP-1 with liquid oxygen and was propelled by a S1.5400 main current engine developed by the engine specialist Michael Melnikow with 66.7 kN of thrust. The stage had 1160 kg empty weight and could take around 3700 kg of fuel. Blok L could only be ignited once and therefore had to be ignited at an exact time in order to reach the orbit required for the satellite. In addition, this resulted in the necessity of an own orientation and stabilization system as well as thermal insulation for the tanks which increased the empty weight. The ignition of the engines in weightlessness also caused some problems. For example, before the actual engines were ignited, at the furthest point of the transition orbit, a drop-off solid-fuel auxiliary engine BOZ was started, which through its thrust ensured that the fuel collected in the tanks on the ground and thereby simulated engine ignition under the conditions of earth gravity. This made Blok L complicated, error-prone and inflexible, which often, especially during early launches, resulted in the payload being suspended in an unusable orbit.

From 1964 Molnija-M (GRAU index 8K78M) was introduced, which had minor modifications to the first two stages and a Blok L with the improved S1.5400A engine. Later three variants of the Bloks L (Blok 2BL, Blok-ML and Blok SO-L) were created, which only differed in the flight profile adapted to the respective payload.

Technical specifications

version	Molnija-M (8K78M)
Takeoff mass	305.5 t
Height (maximum)	43.4 m
Diameter (maximum)	10.3 m
Launch site	Baikonur
Payload ( MEO 400–40000 km, 65 °)	1.9 t
First flight	4th October 1965
1st stage (Blok B, W, G, D)
Engine	4 × RD-107
length	19.2 m
diameter	2.68 m
Dimensions	43.3 t / 3.77 t (empty)
Thrust (max)	813 kN (floor) + 38 kN control nozzles
Burn time	118 s
fuel	LOX / RP-1
2nd stage (Blok A / 8K78M-1)
Engine	RD-110 (RD-108 for 8K78)
length	27.8 m
diameter	2.95 m
Dimensions	100.6 t / 6.8 t (empty)
Thrust (max)	778 kN (floor), 977 (vacuum)
Burn time	285 s
fuel	LOX / RP-1
3rd stage (Blok I / 8K78M-2)
Engine	RD-0110
length	7.2 m
diameter	2.7 m
Mass ( t )	24.8 t / 1.98 t (empty)
thrust	298 kN (vacuum)
Burn time	230 s
fuel	LOX / RP-1
4th stage (Blok L / 8K78M-3)
Engine	S1.5400A
length	2.64 m (5.15 m with payload fairing)
diameter	2.7 m
Dimensions	6.66 t / 1.16 t (empty)
thrust	66.7 kN (vacuum)
Burn time	340 s
fuel	LOX / RP-1
Payload fairing
length	7.8 m
diameter	2.7 m
Payload space	3.67 x 2.65 m

See also

• List of Molniya rocket launches
• Molniya orbit

Web links

• Bernd Leitenberger: The Semjorka launcher
• Raumfahrer.net: Vostok / Molnja

Individual evidence

1. ↑ ^{a b} Molniya 8K78 in the Encyclopedia Astronautica (English)
2. ↑ ^{a b c} FliegerRevue February 2011, pp. 51–53, The last lightning
3. ↑ ^{a b} Eugen Reichl: The rocket type book . 1st edition. 2007, ISBN 978-3-613-02788-6 .