Glossary.

ACCELEROMETER
Seaslug had two accelerometers, one forward and one at the rear. They were used by the Guidance Receiver to prevent the missile turning too quickly.

AFT BODY
The shell of the rear of the missile which contained the electronics etc., it is attached to the rear of the sustainer motor.

ATTACHMENT SET
A substantial aluminium casting which held the four boost motors to the front of the missile.

BOOST ARMING HEAD
Fitted to the top of each boost motor, the BAH contained an electrical switch which (in the safe position) prevented any electrical pulse from reaching the motor's igniter. This switch was operated by the Boost Arming Lever engaging on a lug on the launcher.

BOOST ARMING LEVER
This lever made the final electrical connection to the boost igniter, and rotated a baulking cylinder which locked the BAH in place. In the unlocked position the BAH would be blown out if the boost motor was ignited thus rendering it non-propulsive.

BOOST MOTOR
Four boost motors were mounted in a cruciform arrangement around the front half of the missile, and were identified as Top, Bottom, Left and Right. Their nozzles were canted outwards by 22·5° to keep the efflux away from the missile body, and 22·5° to the left to impart rotation. The motors on the Mk1 missile were GOSLING and on the Mk2 RETRIEVER.

BEACON RADIO
The Beacon Radio transmitted a signal at the start of the gathering phase back to the 901M radar. In the Mk2 missile its output was modulated by the Time and Range Unit (TRU) which gave the fire control system an accurate range for the missile.

BREAK UP UNIT
This item was fitted to the telemetry missiles to ensure their destruction at the end of a test firing.

CANDLE FLAME EXTINGUISHER
The Candle Flame Extinguisher (CFE) contained about half a litre of tetrachloromethane(CCL₄) which was injected into the sustainer motor when it had burnt out. This was to prevent the formation of a 'candle flame' -a small flame creating a large quantity of ionised particles- which would have severely masked the reception of the guidance beam.

CLAMP SET CONTROL SURFACE
This assembly locked the control surfaces (at the rear of the missile) at a slight angle to match the effect of the bosst motor's canted nozzles. It was blown away by the efflux of the sustainer motor.

CONTROL RING
The control ring fitted to the rear of the Aft Body; it contained the hydraulic actuators for the control surfaces and the control surfaces themselves.

CONTROL SURFACES
Seaslug had four control surfaces which were in line with the wings.

DISPLAY MISSILE
Painted bright red, the display missile was totally inert but visually representative of an operational missile.

DIVE/GLIDE SWITCH
This switch was on the surface of the Guidance Receiver, and had two positions -Dive and Glide. It controlled the missile's response to the Dive/Glide command. In the Dive position it caused the missile to enter a 45° dive, in the Glide position for 'up and over' shoots it made the missile ignore any furtherchages in the vertical plane and follow a fixed steep dive angle.

DRILL MISSILE
The drill missile was used for handling practice etc. It was inert but weighed the same as an operational missile and was painted Oxford Blue.

ELECTRONIC PACK CONTROL
This unit received the Guidance Receiver's electrical output commands and operated the control valves in the Valve Transfer Auto-Pilot, which in turn operated the Control Surfaces.

FLARE
The Telemetry missile had a tracking flare fitted to each wingtip to assist camera tracking. They ignited automatically on launch.

FOREBODY
The section of the missile in front of the sustainer motor; it comprises the warhead, fuze and nosecone.

FUZE, INFRA RED.
This was a passive device, identified as the Type 178, and had a peak sensitivity at 430nm. It was only fitted to the Mk2 missile.

FUZE, PRANGER
The pranger fuze was an advanced radio fuze fitted to the Mk1 Seaslug, its name came from Pulse RANge GAte as it had a short receiver gate to detect pulses reflected by the target.

FUZE, RADIO
This was an X-band radar fuze; it had eight recessed-slot antennae spaced around the nose of the missile. Four produced a 5° beam tilted forward at 10-20° and the remaining four were receivers.

FUZE SEGMENT SELECTOR UNIT
Under some circumstances the Infra red Fuze fitted to the Mk2 missile could be triggered by the sun or by the target's exhaust plume during violent manouvering. The Fuze Segment Selector Unit (FSSU) monitored the output of the fuze for triggering responses during the missile's flight, and switched off those segments to prevent the warhead from being detonated as soon as the final arm command was received.

GAS GENERATOR
In the Mk2 missile the Gas Generator burnt iso-propyl nitrate (IPN) in a combustion chamber and then added water to the exhaust, which both reduced the temperature and increased the mass flow. This was used to drive the turbine alternator and the hydraulic pump, to provide electrical and hydraulic power.
In the Mk1 missile the gas generator burnt a cordite charge to drive the generator and pump.

GUIDANCE ANTENNA
This was the Guidance Receiver's aerial which was in the form of a recessed cylinder, similar to a waveguide. It incorporated a rotating polarimeter to compensate for the continually changing polarity of the guidance beam.

GUIDANCE RECEIVER
This unit received the signal from the Type 901 radar, and by referring to its internal time base (synchronised with the radar before launch) steered the missile to the centre of the beam.

GYROSCOPE, ROLL DISPLACEMENT
The gyroscope provided roll stabilisation for the missile in flight; it should be noted that the missile flew with its control surfaces in a vertical and horizontal position, and not the diagonal configuration of launch.

HYDRAULIC ACCUMULATOR
This unit provided a small stored reserve of hydraulic power to even out demands caused by control surface movements.

IRGO VALVE
The Inertia-Release Gas-Operated valve was the device which released the Boost Motors once they had burned out. It was fixed to the bottom Boost Motor and was primed by the gas pressure of the burning propellant. When the acceleration dropped to 1g the valve opened and the stored gas pressure operated the release gear and cable cutters, and the Boost Motors swung clear of the missile.

MISSILE ELECTRIC AND AIR SOCKET
The Missile Electric and Air Socket (MEAS) was engaged by the Launcher Electric and Air Plug (LEAP), and ensured a constant supply of electricty and cooling air whilst the missile was on the launcher. As soon as the missile's internal power supply came up to the correct voltage the LEAP disengaged and swung behind a protective cover.

NOZZLE TRANSFER PIPE
This carried the efflux from the sustainer motor (which was in the middle of the missile) to the nozzle at the rear.

PITOT
Seaslug missiles had a Pitot Tube in the nose cone, not to measure speed but to provide an assessment of the air pressure acting on the missile frame. This was used by the Guidance Receiver to limit Control Surface movements to prevent damage to the air frame in flight.

SAFETY AND ARMING MECHANISM
The Safety and Arming Mechanism comprised two elements: the Electrical Sub Assembly and the Mechanical Sub-Assembly. These were known as the SAMESA and the SAMMSA respectively.
The SAMESA was an electrical switch which was closed by the 'Arm' command, and made the final connection between the fuze and the warhead; it also opened a short-circuit across the warhead's detonator.
The SAMMSA consisted of a switch which closed when the bottom boost motor separated which allowed the sustainer motor to ignite. It also had an inertia switch which required a 13g acceleration for 3 seconds to open the shutters in the detonator train to the warhead.

SERVICING MISSILE
The Servicing Missile was used to test both the shipborne and Armament Depot test equipment. It contained no explosive or propellant but was otherwise fully functional. It had a telemetry bay in place of the warhead and the telemetry transmitter aerial was replaced by a cable. The Turbine Alternator was powered by the ship's (or Depot's) high pressure air supply. The whole missile was painted the same salmon pink colour as the Telemetry Bay, which led to its nickname of 'Pink Panther'.

SPOILER RINGS
These were fitted to the Boost Motors on the Mk2 missile. They provided drag to enable the motors to sparate cleanly on release and fall clear of the missile. They were required in place of the drag struts of the Mk1 because of the higher speed of the missile. They performed the same function as the large fins fitted to Bloodhound and Thunderbird but took up less space, an important factor given the limited space onboard ship.

SUSTAINER MOTOR
This gave a thrust of 1820Kg for 38 seconds in the Mk2 missile and was known as DEERHOUND. The sustainer for the Mk1 (called FOXHOUND) had a lower thrust. A modified Sustainer Motor was used as the third stage of the BLACK ARROW, Britain's space vehicle. So faultlessly did it perform the satellite (PROSPERO) and the motor are still in orbit over 40 years later and both are expected to continue in orbit for another 50 years.

TELEMETRY BAY
This replaced the warhead in a telemetry missile, and was painted a fetching shade of pink. It transmitted a radio signal which contained data about the missile's performance. It also contained a Break Up Unit to ensure the missile's destruction at the end of a test firing. The Telemetry Bay was also used in the Servicing Missile.

TIME AND RANGE UNIT
Once the missile switched over from gather mode to guidance mode, the Guidance Receiver switched the TRU on. This modulated the output of the Beacon Radio which allowed the shipborne system to accurately measure the missile's range.

TURBINE ALTERNATOR
The Turbine Alternator was driven by the efflux from the Gas Generator and produced 115v at 400 Hz.

WARHEAD
The warhead of the Mk2 missile contained 22Kg of an RDX/TNT mixture which was surrounded by a series of 10mm steel rods welded at the top and bottom in such a way as to form a folded hoop. When the warhead detonated it forced the hoop to unfold into a 70 foot (21 metre) diameter circle. This would cut its way through any section of airframe unlucky enough to be in its path. The hoop would would then fracture into random lengths; this type of warhead is known as Continuous Rod. The Mk1 warhead had a plain blast warhead containg 73kg of explosive.

WING
Seaslug had four wings, they provided stabilisation in flight but not lift.



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Last updated: 17^th December 2022.
Copyright SR Jenkins February 2012.