Red Shrimp
Red Shrimp was the airborne high-bandwidth :en:radar jammer|radar jammer fitted to the Vulcan and Victor. The name was one of the :en:Rainbow Code|Rainbow Codes.
Operation
Red Shrimp was a wide-coverage jammer for radar between 2.5–3 GHz. This is in what was described as :en:S band|S band at the time, but is now termed the :en:D band |D and :en:E band |E frequency bands. It was based on a :en:carcinotron|carcinotron or :en:backward-wave oscillator|backward-wave oscillator valve. This is a variable frequency voltage-controlled wide-range oscillator. Changing the control voltage, without requiring any mechanical adjustment, could produce a high-power jamming signal which could be adjusted rapidly to jam any radar frequency.The main target for the jamming was the :en:Fan Song|Fan Song radar, the target acquisition radar of the :en:S-75 Dvina|S-75 Dvina surface-to-air missile. The :en:Blue Diver|Blue Diver jammers targeted its :en:Knife Rest|Knife Rest targeting radar.
The Red Shrimp antenna was quite small and housed in a downward-pointing hemispherical dome, approximately 6 inches in diameter. These were of dielectric material coloured black or dark grey and unpainted. Their signal was broadcast downwards as a cone of around 45° included angle. Later on, as the aircraft switched to operating at extremely low level, this gave a ground coverage patch barely larger than the aircraft's shadow.
Fitment
Valiant
The first Red Shrimp fitment was to a :en:Vickers Valiant|Valiant of the :en:Bomber Command Development Unit|Bomber Command Development Unit. The BCDU was a development unit which operated Valiant WP214 from the end of 1955 as a trials aircraft.By mid-1958 the :en:Electronic Counter-Measures|Electronic Counter-Measures fitment which would become standard for the V bombers had been developed. Equipment was mounted in a series of sealed cylindrical drums, each weighing around 200 lbs, the limit of what could be manhandled for servicing. These were installed in the tail of the aircraft and slid into place on an overhead trolley rail. A water-glycol cooling system, the Vapour Cycle Cooling Pack, was used to cool the equipment, with a large external cooling air intake. An additional AC power system was added to supply enough electrical power. Rather than being engine-driven, this was an air-powered turbo-alternator.
18 Squadron
From 1958 to 1963 :en:No. 18 Squadron RAF#Post war|18 Squadron operated as a dedicated ECM squadron, having been formed from the :en:Vickers Valiant|Valiant-equipped C flight of :en:No. 199 Squadron RAF|199 Squadron, which had developed the role post-war. These seven were the only ECM-equipped Valiants. The initial intention for these aircraft was that they would be used for training UK air defences, simulating a Soviet ECM-using threat. Any idea of a war role for them, as an ECM escort for an attack force of Valiant bombers, developed later. This also required 18 Squadron to start training for the same QRA 'scramble' exercises as the Bomber Command main force.The S band jammer of the 18 Squadron Valiants was the magnetron-based US-made AN/APT-16A jammer. This was a much simpler and less capable system, without the frequency agility of the carcinotron devices. The Carpet 4 spot jammer, had been trialled in Lincolns and also the 18 Squadron Valiants, but it was unreliable and ineffective, so never used.
The electrical supply of the Valiant was also a limitation. The Valiant and first Vulcans had a 112 V DC electrical system, although the trials aircraft had a more powerful 240 V AC system. The DC system was not powerful enough to supply active ECM, such as Red Shrimp, and so those aircraft were limited to the radar warning receivers and chaff dispensers. This omission was never upgraded, as the Valiant's service life was so short.
From 1958, the new 18 Squadron were based at :en:RAF Finningley|RAF Finningley, South Yorkshire, as was the BCDU. Nick Prager, a Czech-born sergeant with the BCDU in the ECM servicing section of the base, together with his wife Jana, supplied photographs of the ECM manual set to the :en:Czech Intelligence Service|Czech Intelligence Service. He was arrested for this in 1971, after betrayal by the defector :en:Josef Frolík|Josef Frolík, and sentenced to 12 years for spying. :en:No. 230 Operational Conversion Unit RAF|230 OCU, the training unit for Vulcan crews, was also based at Finningley from 1961.
As it became clear that the new low-level penetration role would involve bombers travelling singly, each bomber would need its own ECM fit. The squadron retained a development and training role for some time, but this could be performed by simpler aircraft, such as :en:English Electric Canberra|Canberras, than the Valiants and so 18 Squadron was disbanded in 1963.
Vulcan
Vulcan B.1
The original :en:Vulcan B.1|Vulcan B.1 had a fairly simple ECM fit, with little more than chaff dispensers and the :en:Orange Putter|Orange Putter tail warning receiver from the Canberra and Valiant.Additional equipment could be carried along the side walls of the bomb bay, in a series of up to nine containers. These included the Green Palm VHF voice communications jammer, Indigo Bracket, an early carcinotron-based jammer, and Red Carpet X-band radar jammer. Each system was designed to be as self-contained as possible, with the minimum of additional installation around the airframe. The :en:Bristol-Siddeley Olympus|Olympus 104 engines at this time had insufficient electrical generating capacity for such an ECM fit and so an internal ram air turbine was fitted, as for the trial Valiant WP214. This Turbo Alternator TGA 30 Mk 1 was mounted internally and driven by an air inlet near the port engine air intake.
Vulcan B.2
The :en:Vulcan B.2|Vulcan B.2 and B.1A both used an extended rear fuselage, extended into a more bulbous tailcone. The end of this was now a hemispherical radome for the Red Steer tail-warning receiver, rather than the pointed cone of the B.1. A large rectangular box-like duct on the starboard side was the cooling air duct for the :en:condenser |condenser of the VCCP. The braking parachute was inside a hatch on the top, now visible as an external bulge. The nine sealed and pressurised drums of the ECM equipment were arranged in two rows within this tail, with access through hatches in the bottom.The Red Shrimp antennae were arranged on panels added between the engines, usually the 3 & 4 engines. Some aircraft had three on one side, others two and one on each. Blue Diver also used a blade aerial in early years, later wingtip aerials.
| Name | Function | ||
| :en:Green Palm|Green Palm | ARI 18074 | VHF Comms Jammer | later replaced by ARI 18146 |
| :en:Blue Diver|Blue Diver | ARI 18075 | :en:B band |B-band UHF Jammer | - |
| Red Shrimp | ARI 18076 | S-Band Jammer | |
| :en:Red Steer|Red Steer | ARI 5919 | Tail warning radar | - |
| :en:Blue Saga|Blue Saga | ARI 18105 | Passive RWR | later replaced by ARI 18228 |
Vulcan B.1A
The :en:Vulcan B.1A|Vulcan B.1A was an interim design, converted from B.1 aircraft. ECM was a planned part of the new B.2 aircraft with their extended Phase 2C wing, and although there was great urgency to the delivery of the new B.2 aircraft and the first would arrive before the first B.1A, the simpler conversion would permit thirty ECM-equipped aircraft to enter service more quickly than a similar number of B.2s.Low-level
After the Nassau Agreement at the end of 1962, Britain's primary nuclear deterrent was to switch to the Royal Navy and the submarine-launched :en:Polaris missile|Polaris missile. A combination of this change of role, and the increasing effectiveness of Soviet anti-aircraft missiles at high altitude, led to the V-bomber force being re-tasked from a high-level attack to a :en:high-low-high|high-low-high profile with a low-level approach. The B.1 aircraft were re-tasked from Spring 1963, the B.2s from 1964. Visible evidence for this was Mod.1877, repainting from anti-flash white to a two-colour camouflage scheme.The Soviet :en:SA-3 Goa|SA-3 Goa missile was now in service, with its :en:Low Blow |Low Blow radar. This could also be countered by Red Shrimp. Despite the change in role, there was no change in the Vulcan ECM fit. There was little development of this for the next twenty years and it became increasingly less effective. Situational awareness of the threat was reasonable, but ability to counter it was reduced. Most obviously, the Red Shrimp jammers were mounted on the underside, facing downwards. At low level, they were masked by the same terrain which the aircraft was using to shield itself and so the area over which they could radiate became inconsequentially small. One important advance which was installed was a :en:terrain-following radar|terrain-following radar, with a small thimble radome added to the nose, from 1966.