Author: R.E.A.L.

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Soviet/Russian nuclear warheads with yield over 4.5 megatons

Data source: http://www.johnstonsarchive.net/nuclear/multimeg.html#S4

System/warhead: R-16 (SS-7 Mod 1/2/3)
type: ICBM
IOC: Nov 1961
weight (kg) 195
megaton yield: ~6
number built: 0-320

System/warhead: R-9A (SS-8)
type: ICBM
IOC: Dec 1964
weight (kg) 1800
megaton yield: ~5
number built: 23-46

System/warhead: R-36 8K67 Tsiklon (SS-9 Mod 1)
type: ICBM
IOC: Nov 1966
weight (kg) 7000
megaton yield: 18
number built: 140-290

System/warhead: R-36 8K67 Tsiklon (SS-9 Mod 2) [8F675]
type: ICBM
IOC: 1966
weight (kg) 7000
megaton yield: 25
number built: 140-290

System/warhead: R-36O 8K69 Tsiklon (SS-9 Mod 3)
type: FOBS
IOC: Aug 1969
weight (kg) 5000
megaton yield: ~20
number built: 0-20

System/warhead: MR UR-100N (SS-17 Mod 2)
type: ICBM
IOC: 1977
weight (kg) 3500
megaton yield: ~5
number built: 10-30

System/warhead: R-36M (SS-18 Mod 1) [15B86]
type: ICBM
IOC: Dec 1974
weight (kg) 7500
megaton yield: 24
number built: 20-60

System/warhead: R-36MUTTKh (SS-18 Mod 3)
type: ICBM
IOC: 1976
weight (kg) 7300
megaton yield: 20
number built: 20-60

System/warhead: R-36M2 Voevoda (SS-18 Mod 6)
type: ICBM
IOC: Aug 1990
weight (kg) 9000
megaton yield: 20
number built: 20

System/warhead: UR-100NU (SS-19 Mod 2))
type: ICBM
IOC: 1977
weight (kg) 3500
megaton yield: ~5
number built: 60

System/warhead: RDS-220 (“Tsar Bomba”)
type: NGB
IOC: 27000
weight (kg) 3500
megaton yield: ~150
number built: 0-5

The largest Soviet nuclear weapon

The largest nuclear weapon ever developed by any nuclear power was the Soviet RDS-220,[62] also nicknamed “Big Ivan”, “Vanya” or “Tsar Bomba” (King of Bombs). It was a three-stage weapon weighing 24.8 metric tons and was 8 meters long. Its 2-meter diameter required a specially modified version of the Tu-95 Bear bomber for delivery. The single such Tu-95V carried the RDS-220 partially protruding from the bomb bay.[63, 64] The U.S.S.R. tested this design in an airdrop over Novaya Zemlya on 30 October 1961 at a yield of about 58 megatons.[65, 89, 90] However, this was a reduced yield “clean” version: the uranium sleeve on the tertiary stage was replaced with lead, and the fission yield was only 3% of the total yield.[63] The full yield version had a yield variously reported as 100 mt [64] or 150 mt [62]. About 80% of the fallout from the “Tsar Bomba” test was deposited as global fallout.[67]

The yield of the 30 October 1961 test remains the subject of some debate. Best estimate here is that the actual yield was 57-58 mt, based on the following:

• The U.S. estimate of 57-58 mt was based on bhangmeter (high-speed photometer) observations and other data from a USAF KC-135 flown near the blast–apparently to within 45 km–as analyzed by the Foreign Weapons Evaluation Panel (or Bethe Panel) to determine the yield.[63, 96, 97]
• A yield of 58 mt has been affirmed in scientific publications by Russian experts on the Soviet testing program.[99]
• Nikita Khrushchev in his memoirs claims that the device yield was estimated before the test as 50 mt, and that the actual yield proved greater at 57 mt.[91]
• Following the collapse of the Soviet Union, official Russian sources (e.g. the Russian atomic energy ministry) have released information on Soviet nuclear tests, reporting a yield of 50 mt.[66, 92] In many cases, discrepancies between the new Russian data and older Western estimates represent the large uncertainties involved in Western intelligence efforts to estimate yields from remote observation. In this case the U.S. data was acquired from close at hand (sufficiently close that the U.S. KC-135 suffered scorching on the fuselage from the flash[96]). Discrepancies with Russian data may represent continued Russian secrecy (e.g. exact yields for several high yield Soviet tests are still unannounced by Russia [92]), combined with the desire to minimize the issue of fallout associated with the test. The current Russian figures for the Tsar Bomba test, 50 mt yield at 4000 m altitude, place it safely 9% above the Russian agency’s threshold defining “air explosions,” where “the expanding fireball does not touch the ground surface” [98], whereas the Western data of 57-58 mt yield at 3500 m altitude place it 9% below this threshold.

Thus the issue regarding the test yield is plausibly explained by the test exceeding its predicted yield by 15% (still close to design yield, given U.S. test experience) at an actual yield of 57-58 mt, with the current Russian government finding various reasons to prefer the 50 mt yield figure.

Another device tested the following year had a nominal yield of 50 mt. Tested at a reduced yield of 24.2 mt on 24 December 1962 at Novaya Zemlya, it was designed at Chelyabinsk-70 (as opposed to Arzamas-16 for the RDS-220)[66].

Whether either of these weapons was operational is unknown. The RDS-220 was probably never operational: only the single specially modified Tu-95V could carry it, and when doing so it would have been particularly vulnerable to anti-aircraft action. The 50-mt Chelyabinsk-70 device might have weighed 10-15 metric tons, based on comparison to other Soviet warheads of the time. Thus it was probably deliverable by unmodified Tu-95M Bear bombers, which could carry 15 metric tons of payload (albeit to a reduced range).[68] Any operational deployment was probably only for a short time since bomber forces were converting to cruise missiles, but the weapons could have remained in the stockpile as late as the 1980s, given the apparent slow pace of Soviet warhead disassembly.

The Soviets briefly considered developing an ICBM capable of carrying the 150-mt RDS-220 warhead or a similarly large warhead. Of several proposed missiles, only the UR-500 reached the flight stage, by which time any nuclear-armed version was abandoned in favor of using the UR-500 exclusively as a space launch vehicle.[69]

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The first Soviet ICBMs

The first Soviet ICBM was the R-7/R-7A, known as the SS-6 Sapwood in the West. Six of these missiles were deployed from 1960 to 1967, with warheads of about 4 mt yield (yield variously reported as 3-5 mt).[93]

Deployment of the R-7 was limited, since the superior R-9A and R-16 ICBMs were deployed a short time later. The R-16, or SS-7 Saddler, was deployed in several versions and with two types of warhead, 3 mt yield or 6 mt yield. The first R-16s were operational 1 November 1961, and by the end of 1965 a total of 186 to 202 missiles were deployed. Retirement began in 1967, and the last R-16 was withdrawn in 1977.[94, 95]

The R-9A, or SS-8 Sasin in the West, carried a 5-mt warhead. It was deployed 14 December 1964 with full deployment of 23-26 by 1966; all were retired by 1976.[94, 95]

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The R-36 heavy ICBM

The R-36 heavy ICBM, known in the West as the SS-9 Scarp, was deployed in four versions. Two versions of the R-36 carried single warheads: the SS-9 Mod 1 carried a warhead of 10 mt (some sources report 5 mt), and the SS-9 Mod 2 carried the 8F675 warhead with a yield of 25 mt (some sources report 18 mt). The R-36O version (Western designation SS-9 Mod 3) was a fractional-orbit bombardment system (FOBS). It would launch a single 5-mt warhead into low-Earth orbit, southbound from the USSR. Once orbiting over the United States, the warhead would deorbit and strike its target. The system was intended to bypass U.S. early-warning radars. The final version, the R-36P (Western designation SS-9 Mod 4) carried 3 warheads, not independently targetable. Each warhead had a yield between 2 and 5 mt.[70, 71]

The R-36 went on alert on 9 November 1966, and 268 of all four versions were deployed in underground silos. All were retired by 1978 except for some R-36O versions. The R-36O FOBS version, which went on alert 25 August 1969, was retained in small numbers until January 1983, when the SALT II treaty was completed and barred their deployment.[70, 71]

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The R-36M, R-36MUTTKh, and R-36M2 heavy ICBMs

The heavy ICBM known in the West as the SS-18 Satan actually includes three related missiles–the R-36M, the R-36MUTTKh, and the R-36M2–with a variety of warhead loadings in each case. Deployed in both MIRVed and single-warhead versions, the single warhead variants carried the largest missile warheads ever deployed.[72, 73]

The R-36M was developed as a replacement for the R-36. Flight tests were conducted from October 1972 to October 1975 on three variants. The 15B86 single warhead version, with a 24-mt yield, was the first version deployed; this was known in the West as the SS-18 Mod 1. These became operational in December 1974 in converted R-36 silos at Dombarovksy. Most R-36Ms were deployed with 15F143 MIRV warheads–eight warheads each–although a ten-warhead 15F143U version also existed. The MIRVed version (Western designation SS-18 Mod 2) became operational in November 1975. A version carrying terminally-guided 15F678 warheads (MaRVs) was tested from July 1978 to August 1980 but never deployed.[72, 73]

The follow-on R-36MUTTKh was flight tested in a MIRVed variant from October 1977 to November 1979, known in the West as the SS-18 Mod 4.[72, 73] The 15F183 warhead section generally carried 10 warheads, although at least one flight test carried 14 warheads.[74] Some R-36MUTTHk ICBMs carried the 15B86 single warhead at 24 mt (Western designation SS-18 Mod 3), now with improved accuracy over the R-36M. In September 1979 the first three R-36MUTTKh regiments became operational; they had replaced all R-36 missiles by 1980, all R-36M missiles by 1982 or 1983, and reached full deployment in 308 silos by 1983.[72, 73]

Another follow-on, the R-36M2 Voyevoda (“commander” in English), was flight tested from March 1986 to September 1989. The MIRVed variant (SS-18 Mod 5), with ten 15F173 warheads, became operational in December 1988. A single-warhead version (SS-18 Mod 6), with the 15F175 warhead providing a 20-mt yield, was deployed in small numbers begining in August 1990.[72, 73] The single-warhead R-36M2 is the highest yield nuclear weapon currently deployed by any nation.