As promised in another thread, I’ve dusted off my strategic weapons files to see what I’ve got on the UK’s Chevaline Polaris-improvement programme.
(These days my files are all on a massively backed-up hard disk, but when I started in this game they were paper documents. I caused consternation at one airport c.1980 when a zealous customers official opened my briefcase and found himself staring at a file labelled ‘Soviet strategic nuclear capability’. The situation was not improved when the looked at the titles of some of the other files I was carrying.)
Even before the first UK Resolution class submarine had made its first patrol, the UK had begun to study potential improvements to the Polaris A3 missile. By 1969, serious work was under way, based on a US Polaris-improvement project named Antelope. (The latter was abandoned, the US preferring to develop the MIRV-equipped Poseidon.)
The project-definition stage of what became Chevaline was completed in 1972. The programme was launched in 1974, and completed in 1982.
For a long time, the only detailed description of Chevaline was that contained in the Union Of Concerned Scientists’ 2000 report ‘Countermeasures: A Technical Evaluation of the Operational Effectiveness of the Planned US National Missile Defense System’.
This correctly stated that the system carried only two real warheads rather than the original three – as a result of the Polaris A3 missile’s limited throw weight, warhead-carrying capacity had to be traded for countermeasures.
According to Chevaline designer Dr Stanley Orman, in many of its other details the UCS report was incorrect.
The UCS claimed that Chevaline also deployed four re-entering decoy warheads – it carried none. (This disposes of the UCS claim that the four decoy warheads were fitted with small liquid-propellant thrusters used to compensate for the fact that atmospheric drag would have different effects on re-entering objects of different weights.)
It also claimed that the real and decoy warheads were each enclosed in gas-filled balloons. Known as anti-simulation, this technique sets out to make a warhead look like a decoy, rather than to develop a decoy that looks like a warhead.
Another claim was that Chevaline also released a large number of other balloon decoys with nothing inside. These were intended to overwhelm exoatmospheric interceptors.
The UCS report noted that the re-entry vehicles reportedly conducted preplanned manoeuvres during on re-entry; Orman says they did not.
It claimed that all the real and decoy warheads fired from one submarine flew trajectories that made them arrive over the target simultaneously. “Wrong”, said Orman at the 2001 missile conference I mentioned in another posting. “The firing sequence was very different.”.
The OCS also claimed that “most of Britain’s difficulties apparently centred on developing the maneuvering bus, which was the most technically complex component of the system (and which Britain eventually hired US contractors to build)”. I have no information on whether this is correct or not.
The Chevaline entry on Wikipedia – illustrated by a diagram that is worth downloading – is basically correct, but I can’t be sure of the details. It describes the penetration aid carrier, basically a form of post-boost vehicle. This carried one of the warheads and all the penaids – the other RV was released by the second stage of the Polaris A3.
The Wikipedia photo of the penetration aid carrier shows a series of tubular containers for decoys. These dispensed 27 decoys on unspecified into a ‘threat tube’ surrounding the RVs, “which also had a ‘disguise’ to match their radar appearance to the decoys” (a reference to some form of anti-simulation) says Wikipedia. This fits with Orman’s statement that the RVs were “disguised to resemble decoys”.
Each object in the threat cloud was surrounded by chaff tuned to match Russian radars.
The warheads and RVs were hardened to survive a nuclear burst, as were a potion of the penaids.
The entire array of warheads and penaids from each missile was designed to present the Russian defences with widely-spaced multiple realistic targets.
Mercurius Cantabrigiensis
By: Vega ECM - 23rd December 2007 at 08:45
The OCS also claimed that “most of Britain’s difficulties apparently centred on developing the maneuvering bus, which was the most technically complex component of the system (and which Britain eventually hired US contractors to build)”. I have no information on whether this is correct or not.
From the information that I have, the first bus maneuvering concept was powered by jets of gas metered down from a single very high pressure compressed gas bottle (stainless steel sphere). This was because the RN initially totally refused to have Hydrazine on their boats. The high pressure gas system worked well in the vacuum chamber but flew very badly on test shots. Crises erupted, so a team of consultants from an American company was brought in to review the design. The outcome of this was replacement of the compressed gas system with a more conventional Hydrazine decomposition system. The Amercian company became the prime for the bus reaction subsysystem development and the RN was persuaded against their better judgement (at government level) to reverse their original edict.
By: Mercurius - 22nd December 2007 at 18:14
I do think you intended to write ‘Resolution class’ 😉
I did, and I have fixed the error in my posting. Thanks for picking it up.
Mercurius Cantab.
By: Arabella-Cox - 22nd December 2007 at 17:04
Even before the first UK Vanguard class submarine had made its first patrol, the UK had begun to study potential improvements to the Polaris A3 missile.
I do think you intended to write ‘Resolution class’ 😉 Thanks for posting this info, it certainly seems to confirm my suspicion that the manoeuvering reentry vehicles were bogus.
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December 22, 2007 at 4:42 pm