R-7 Semyorka
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[[Image:SS6 Sapwood launch vehicle.png|thumb|250px|SS-6 rocket. (NASA)]]
The '''R-7 Semyorka''' ({{lang-ru|Р-7 "Семёрка"}}) was the world's first true [[intercontinental ballistic missile]] and was deployed by the [[Soviet Union]] during the [[Cold War]] from 1959 to 1968. To the West it was known by the [[NATO reporting name]] '''SS-6 Sapwood''' and within the Soviet Union by the [[GRAU]] index '''8K71'''. In modified form, it launched [[Sputnik]], the first artificial satellite, into orbit, and became the basis for the [[Soyuz launch vehicle|Soyuz]] [[Expendable launch system|space launcher]] and the [[Molniya (rocket)|Molniya]], [[Vostok]] and [[Voskhod]] variants.
The widely used nickname for the R-7 launcher, "semyorka", simply means "the digit 7" in [[Russian language|Russian]].
== Description ==
The R-7 was 34 m long, 3 m in diameter and weighed 280 [[metric ton]]s, it was two-stage, powered by [[rocket]] motors using liquid [[oxygen]] (lox) and [[kerosene]] and was capable of delivering its payload at around 8,800 km, with an accuracy ([[Circular error probable|CEP]]) of around 5km. A single [[nuclear weapon|nuclear warhead]] was carried with a nominal yield of 3 [[megaton]]s of [[trinitrotoluene|TNT]]. The initial launch was boosted by four strap-on [[liquid rocket booster]]s making up the first stage with a central 'sustainer' motor powering through both the first and the second stage. Each strap-on booster included two [[vernier thruster]]s and the core stage included four.<ref>
{{cite web | url = http://www.energia.ru/english/energia/launchers/rocket-r7.html | title = Rocket R-7 | publisher = S.P.Korolev RSC Energia}}</ref> The guidance system was inertial with radio control of the vernier thrusters.
== Development ==
Design work began at OKB-1 (later [[S.P. Korolev Rocket and Space Corporation Energia]]) in Kaliningrad (now [[Korolev, Moscow Oblast|Korolev]]) and other divisions in 1953 with the requirement for a two-stage missile of 170 tons with a range of 8,000 km carrying a 3000 kg warhead. Following first ground tests in late 1953 the initial design was heavily reworked and the final design was not approved until May 1954. The first testing of the new missile, codenamed 8K71, was on [[May 15]], [[1957]] from [[Baikonur Cosmodrome]]. A fire in a strap-on rocket led to an unintended crash 400 km from the site. Following another unsuccessful test the first successful long flight, of 6,000 km, was made on [[August 21]]. It was announced by [[TASS (USSR)|TASS]] on [[August 26]]. A modified version of the missile placed [[Sputnik 1]] in orbit from Baikonur on [[October 4]] and [[Sputnik 2]] on [[November 3]].
Following these first tests certain modifications were found to be needed and test flights were not completed until December 1959. The additional development resulted in the 8K74 which compared to the 8K71 was lighter, had better navigation systems, more powerful engines and more fuel extending its range to 12,000 km and payload to 5,370 kg. The warhead was tested on [[Novaya Zemlya]] in October 1957 and again in 1958, yielding an estimated 2.9 Mt of TNT.
The 8K71 and the 8K74 variants were manufactured as the R-7 and R-7A. The missiles were fully deployed by 1962 and were phased-out by 1968. But it was still used for space research, where it was further developed into the reliable [[Vostok rocket|Vostok]], [[Voskhod rocket|Voskhod]] and later the [[Soyuz launch vehicle|Soyuz]] launchers.
== Operational history ==
The first strategic-missile unit became operational on [[9 February]], [[1959]] at Plesetsk in north-west Russia. On [[15 December]], 1959 it tested its R-7 missile for the first time.
Total service was limited to no more than ten nuclear armed missiles active at any time. A single launch pad was operational at [[Baikonur]] and from six to eight were in operation at [[Plesetsk]].[http://data-freeway.com/plesetsk/bsemyorka_8.htm]
The costs of the system were high, mostly due to the difficulty of constructing in remote areas the large launch sites required. At one point, each launch site was projected to cost 5% of the Soviet defence budget. However, these huge costs were not unique for a first generation missile and the US experienced similar problems.
Besides the cost, the missile system faced other operational challenges. With the [[Lockheed U-2|U-2]] overflights, the huge R-7 launch complexes could not be hidden but could be expected to be destroyed quickly in any nuclear war. Also, the R-7 took almost twenty hours to prepare for launching, and it could not be left on alert for more than a day due to its cryogenic fuel system. Therefore, the Soviet force could not be kept on permanent alert, and could have been subject to an air strike before launching. Additionally the huge payload for which it was designed, adapted to early heavy H-bombs, became irrelevant with the coming of lighter bomb technology. The limitations of the R-7 pushed the Soviet Union into rapidly developing second-generation missiles which would be more viable weapons systems.
==Modifications==
[[Image:GPN-2002-000184.png|center|Vriants of R-7]]
=== Sputnik Rocket ===
{{Main|Sputnik rocket}}
Sputnik Rocket ({{lang-ru|ракета-носитель Спутник}}) was the name of a rocket, indexed as '''8K71PS''', used as a launch vehicle by the [[Soviet Union]] to launch [[Sputnik 1]] and [[Sputnik 2]] satellites.<ref>{{ru icon}} [http://www.tsenki.com/Roket1Show.asp?RoketID=8 Sputnik Rocket]</ref> The 8K71PS is essentially a modified [[R-7 rocket|R-7 ICBM]]. No other rocket stages were added to the ICBM to launch the satellites.
====Sputnik Rocket specifications====
*Stage number: 0 - Strap-on boosters; 4 x 8K71PS-0
**Gross mass: 43.0 tons{{vague|metric tons?|date=March 2008}}
**Empty mass: 3.400 tons
**Thrust (vac): 4 × 99,000 kgf = 396 Mgf (3.89 MN)
**[[Specific impulse|Isp]]: 306 s (3,000 N·s/kg)
**Burn time: 120 s (2 min)
**Isp(sl): 250 s (2,450 N·s/kg)
**Diameter: 2.7 meters (8.8 ft)
**Span: 2.7 meters (8 ft 10 in)
**Length: 19.00 meters (62 ft 4 in)
**Propellants: [[LOX]]/[[kerosene]]
**Engines: 1 x [[RD-107]]-8D74PS per booster = 4
*Stage number: 1 - Core stage; 1 x 8K71PS-1
**Gross mass: 94.0 tons
**Empty mass: 7.495 tons
**Thrust (vac): 99,000 kgf (970 kN)
**Isp: 308 s (3,020 [[newton second|N·s]]/kg)
**Burn time: 310 s (5 min 10 s)
**Isp(sl): 241 s (2,360 N·s/kg)
**Diameter: 3.0 meters (9 ft 10 in)
**Span: 3.0 meters
**Length: 28.00 meters (91 ft 10 in)
**Propellants: Lox/Kerosene
**Engine: 1 x RD-108-8D75PS
*Total mass: 267 tons{{vague|date=March 2008}} (534,000 lb)<!--somebody has interpreted the vague tons as short tons. Is that correct?-->
*[[Low Earth orbit|LEO]] payload: 500 kg
*Total liftoff thrust: 3.89 MN
=== Sputnik 8A91 ===
Sputnik 8A91 rocket, where '''8A91''' is rockets [[GRAU]] index, was another modification of R-7 rocket with more powerful engines 8D76 and 8D77 installed,<ref>[http://www.lpre.de/energomash/RD-107/index.htm RD-107 and RD-108]</ref> capable to launch much heavier satellites than Sputnik-1 and Sputnik-2. It was used two times to launch [[Sputnik 3]] satellite:<ref>[http://planet4589.org/space/log/launchlog.txt Jonathan McDowell's launch log]</ref>
*The first launch on [[April 27]] [[1958]] was unsuccessful due to vibrations that unexpectedly occurred during the flight along the [[longitudinal axis]] of the rocket.
*On [[May 5]] [[1958]] [[Sputnik 3]] was launched by this rocket.<ref>{{ru icon}} [http://www.lidorenko.ru/ns3.htm Soviet Solar Cells on Orbit]</ref>
====Sputnik 8A91 specifications====
*Stage number: 0 - Strap-on boosters; 4 x Sputnik 8A91-0
**Gross mass: 43.0 tons
**Empty mass: 3.400 tons
**Thrust (vac): 4 × 99,000 kgf = 396 Mgf (3.89 MN)
**[[Specific impulse|Isp]]: 310 s (3,040 N·s/kg)
**Burn time: 130 s (2 min 10 s)
**Isp(sl): 252 s (2,470 N·s/kg)
**Diameter: 2.7 meters (8.8 ft)
**Span: 2.7 meters
**Length: 19.00 meters (62.3 ft)
**Propellants: Lox/kerosene
**Engines: 1 x [[RD-107]]-8D76 per booster = 4
*Stage number: 1 - Core stage; 1 x Sputnik 8A91-1
**Gross mass: 95.0 tons{{vague|date=March 2008}}
**Empty mass: 7.100 tons
**Thrust (vac): 82,000 kgf (804 kN)
**Isp: 315 s (3,090 N·s/kg)
**Burn time: 360 s (6 min)
**Isp(sl): 246 s (2,410 N·s/kg)
**Diameter: 2.99 meters (9.8 ft)
**Length: 28.00 meters (91.9 ft)
**Propellants: LOX/Kerosene
**Engine: 1 x RD-108-8D77
*Total mass: 269.3 tons{{vague|short, as somebody converted one of them? long? metric?|date=March 2008}}
*[[Low Earth orbit|LEO]] payload: 1,327 kg (2,925 lb)
*Total liftoff thrust: 385,950 kgf (3.784 MN, 850,870 [[pound-force|lbf]])
== Operators ==
; {{USSR}}: The [[Strategic Rocket Forces]] were the only operators of the Semyorka.
== See also ==
* [[List of missiles]]
* [[1957 in spaceflight]]
== References ==
{{refbegin}}
{{reflist}}
* ''The Kremlin's Nuclear Sword'', Steven J. Zaloga, Smithsonian Institution Press, Washington and London, 2002.
{{refend}}
{{Refimprove|date=September 2007}}
== External links ==
* [http://www.energia.ru/english/energia/launchers/rocket-r7.html Rocket R-7] from [[S.P. Korolev Rocket and Space Corporation Energia]], a [[Russia]]n rocket and space contractor
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[[Category:Cold War intercontinental ballistic missiles of the Soviet Union]]
[[Category:Novaya Zemlya]]
[[Category:Soviet rockets]]
[[Category:Space launch vehicles]]
[[Category:Strategic Rocket Forces guided missiles]]
[[Category:Russian inventions]]
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