Sea Slug vs Terrier


ACCESS: Top Secret
Senior Member
4 June 2006
Reaction score
Sea Slug used wrap around boosters while the Terrier system used an in-line booster, what was the reasoning behind the decision to place the boosters where they did?

Which was the easier to handle on the ship?
Norman Friedman says in "Modern Warship", that this configuration was chosen for length
reason, as the missiles were stowed in tandem rows and not parallel in the County class.
Perhaps the text gives a better description :
"Unlike Terrier and Talos, the British Seaslug employed a booster wrappe around
the missile propoer - in effect it traded length for diameter. Instead of a ring of
missile bodies, Seaslug stowage is a string of assembled missiles, eac on its own
trolley, leading up to the launcher rail.Ship-impact was tremendous: much of the
superstructure deck of a 'County' class missile destroyer conceals the Seaslug ready-
service stowage, one line of missiles for each side of the launcher. Other missiles, not
assembled, are held in a magazine."
True, it did make the missile shorter but that doesn't seem to have bothered the US with their Terrier missiles, they ended up with larger magazines on ships that were not that much bigger than the Counties
Wrap around saved you about 2.3 metres per missile - magazine capacity was around 24 from what DK Brown says in 'Rebuilding the RN' and not all those would be assembled.

I really do wonder if trying to shorten the missile just added problems later on for the the assembly crew - four boosters rather than one.
Your average Terrier (and RIM-67) launcher had 20 rounds per arm for 40 rounds per launcher. The Belknap (and Truxtun one-off) had a three-ring magazine with the third holding 20 ASROC. (I'll post a link to a video of this latter configuration later tonight). Went and double-checked and it looks like Long Beach also had the triple-ring magazines albeit with all Terriers for a total of 120 Terrier/RIM-67 and 52 Talos before modification.
Just noticed something on the Skomer page

The ultimate version for the Chilean Navy dispensed with the wrap-around boosters and used a tandem boost.
i remember reading somewhere, but of course i can't remember where, that the reason the seaslug boosters were wrapped around the front of the missile, was that in that position, no stabilising fins were needed, unlike the aft mounted boosters on the bloodhound and thunderbird missiles.

What type of guidance did Bloodhound have at the time, it did have semi-active at some point but did it start out with semi-active?

I ask this because the beam riding guidance of Sea Slug does get criticised.
Here's the link I mentioned earlier of a peek at the Terrier magazines:

Last edited:
Presumably 4 boosters increases the chances of failiure on launch - does anyone know the launch fail rate of Sea Slug vs Terrier?
Anyone know what the UK's ability to make boosters big enough for an in-line configuration was at this time?

See post 24 from NwGolconda
"What type of guidance did Bloodhound have at the time"

Semi-active homing with a BTH, later AEI Stingray radar.

I've just read, that at first a triple launcher was planned, what probably would have meant
3, instead of two rows of missiles. Such a launcher was even used on trials from the HMS
Girdle Ness.
Sea Slug was redesigned from a tandem, liquid fuelled configuration to solid fuelled, wrap around boosters "due to size constraints" according to Chris Gibson's BSP4.
The main reason for Sea Slug's wrap-around boosts was to produce a compact unit, however wrap-around boosts have another "advantage" in that the missile's own stabilsers (held in a neutral postion until boost separation) can be used as boost fins on launch. A tandem boost would have needed it's own boost fins, adding size.

A single boost failure would not be totally catastrophic on a wrap-around system as the nozzles are canted so they apply their thrust through a common point to reduce assymetric thrust.

Whether these compensate for the hassle of boost separation is debatable, but you don't see it very often today.

Anti-Kamikaze was UK's first GAAP application, 1944, assigned to spare AWA in 1946. Red Heathen was split in 1949, liberating Army to do fixed SAM with Bristol (to be RAF Regt. Bloodhound 1) and mobile with EE (to be Thunderbird), with fresh suppliers. I think, PMN1 you are right, that before the 1950 Burns/Templer data-exchange, which put BOMARC data on Bloodhound as (to be) Thor ramjet, and Aerojet General licenced motors in Bristol Aerojet, UK could only do little boosters.

US offered licenced BT-1 Terrier in 1951, declined as that would "have a bad effect on UK GW industry" Twigge, Early Devt of (UK)GW, P.164. We proceeded with a bespoke "convoy escort missile ship", adding bow-mounted Blue Slug SSM. Terrier "would not fit" (Chicken? Egg?) In 1957 US offered BT-3 Terrier, declined, even as we were subsuming our Bomb into theirs, because "US might not supply".

Slug 1 went to sea in 1962. Squander, of money and skills, embarrassing many Ministers in Commons grillings. As for sustaining "independent" design capability, I doubt any corporate wisdom flowed from Slug into Dart, Wolf, or anything. (It is good to see, in your Warships1 link, that Terrier, too, had its problems, endangering life and limb. Though we did not know that when we rejected it).
At the time it was being developed, could Sea Slug have had the same sort of propulsion that Sea Dart did when it was developed - solid booster and ramjet and if so what would that have done to the range of the missile?
When was the originally hoped for 'in service' date for Sea Slug??
Not a simple A. Origin was 1944, anti-Kamikaze, so NOW! Then Peace broke out and money dried, till Berlin Blockade. MoS R&D contract on AWA was 4/49, promoted 8/49 as "highest priority" of the 4 confirmed from 20 nascent UK GW projects. Drift. Bloat, bulking beyond any Fleet vessel, so tied 7/53 to a bespoke "convoy escort missile ship" (aka County). (This much, largely S.R.Twigge,Early Devt of GW in UK ’40-60,H’wood,1993 e.g. P.164). You must then research your surface vessel sources to find intended commissioning date for Counties. The A, of course, was "somewhat sooner, please, than 1962".

Slug destroyed the GW business credibility of AWA/HS: “effective financial control was exercised at no stage (A) completely sorry story” 59/60 Pub.Accts. Cttee,in Twigge,P225. “Final cost exceeded initial estimates by a factor of 19” Sir R.Way,MoS Perm.Sec., in J.Bruce-Gardyne,N.Lawson (Yes, him, as in Nigella),The Power Game,Macmillan,1976,P25. MoS/Admiralty didn't do well either.
I've only recently found this thread and thought I'd add some comments as I am currently researching the Seaslug system.
The Chilean Navy never carried out any development on seaslug see the picture of a firing by Capitan Prat at -it still has the boost motors at the front. I don't know where Chris got the information on his Skomer site from and unfortunately he doesn't have any contact details on his website.
Robunos & CJGibson: You're quite right. Seaslug Mk1 had 'drag struts' to provide air resistance for boost separation; Seaslug Mk2 had the unique spoiler rings to do the same thing.
Seaslug was originally going to have a liquid fuelled sustainer but this was dropped for several reasons in favourof solid fuel
Kind of bizarre to read this thread side by side with the warships1 thread of same name...

I'd be interested in hearing if anyone knows of any plans to field a Sea Slug Mk 3. Seems like a bit of a no brainer in the 1970s to use Sea Dart guidance technology and the latest rocket propellant mix to make Sea Slug a better weapon and significantly enhance the capability of eight good ships into the 1980s for the RN.
The Batch I ships were decommissioned from the RN from 1976 to 1981, this having been planned as early as 1967/8 when it was decided not to upgrade them, they never got Sea Slug Mk2 or ADAWS so were still running CDS and Sea Slug Mk I when they were decommissioned. That leaves the 4 Batch II ships which theoretically have more scope for upgrade but in reality the RN seems (this is apparent in various documents in the PRO) to have lost interest in Seaslug as soon as they realised how good the small ship system (Sea Dart) was going to be by comparison (early-mid 60s). By 1979 the RN had ordered 18 ships with Sea Dart and their priority was getting more (which they never did), getting a better Sea Dart, and a more modern CMS for it so a Sea Slug Mark III would have been very low on the list of priorities.

Not to mention the County class had a complement of 471 compared to 287 for the T42 BIII so there would have been little motivation to keep them any longer than necessary.


Your convoy escort missile ship is probably not a County but Girdle Ness; she was not just a typical trials ship but was also considered a prototype for actual convoy escorts (it was thought both coastal and ocean would be needed). Destroyers seem to have been about the last ship type considered for Sea Slug due to the systems size.

There has also been some odd statements made about Seaslug. For instance the oft repeated line that it was not used as a SAM in the Falklands, was not operational by 1982 or was only used for shore bombardment; yet I have seen at least two accounts that contradict this whilst (at least one of???) the missiles fired at Stanley airport was apparently a telemetry round and it was done to clear that particular missile from Glamorgan's magazine to ease the reloading of the launcher. Lack of low altitude performance does appear to have been a real issue though.
Last edited:

you mentioned Twigge, Early Devt of (UK)GW. The title piqued my interest, so I tried to find more information. As the book is OOP, not much to be found other than a timeframe 1940-1960. Does the book cover all GW projects, or just naval SAM?
And, pray tell, what is this topic doing in the Aerospace section, for goodness' sake?!?!? :eek:
Stargazer2006 said:
And, pray tell, what is this topic doing in the Aerospace section, for goodness' sake?!?!? :eek:

Thread start date is 2007 so I'm pretty sure that predates the missile section and maybe even the naval section.
Stargazer2006 said:
...what is this topic doing in the Aerospace section ...?!?!? :eek:

Had the same thought, too, nearly everytime I saw this thread, but:

- It's NOT about projects, not even just prototypes or cancelled programs.
- It's about flying objects, so more appropriate here, than in the military section
- It's one of those "... vs ..." topics, to my opinion always wrong in our ".. projects"
sections, as mixing up two completely different types. Although I must admit, that at
least here, the bar-room clichés, very often typical for such threads weren't used (Thank you !)

So, to my opinion, this thread is quite well place here.
Abraham Gubler said:
Kind of bizarre to read this thread side by side with the warships1 thread of same name...

I'd be interested in hearing if anyone knows of any plans to field a Sea Slug Mk 3. Seems like a bit of a no brainer in the 1970s to use Sea Dart guidance technology and the latest rocket propellant mix to make Sea Slug a better weapon and significantly enhance the capability of eight good ships into the 1980s for the RN.

There was a Mk3 proposed by the Project 502 team -in competion with a rather slim offering from Bristol powered by a ramjet. Mk3 was still a beam rider and the navy preferred Bristol's SARH; but they insisted that the Project 502 team be the design authority, probably because they had the track record of taking little more than a 'back of an envelope' idea and turning it into a functional weapon -albeit at a cost and a long time!
I've never encountered a Seaslug Mk.3, only the Mk.1 and Mk.2. Bristol Seaslug didn't thrive while Red Hand was Seaslug with AA No.3 Mk.7 radar for the Army, but that went nowhere.

Can't see the Admiralty opting for a further development of Seaslug, so NIGS is probably what is being referred to.

Oddly enough, last time I went offshore, my taxi driver was a former weapons articifer on HMS Fife. Yes, I always have a blah with the drivers, but don't rely on them for all my research, Mr Stargazer, I much prefer a bloke in a pub. He confirmed the story I'd been told offshore that whenever a Seaslug was launched and guided as advertised, they broke out the rum! Which was nice.

Via Commandant Ours Polaire over at HP&CA, here's a handy Shipbucket image of the Sea Slug launcher installation layout:


  • sea slug launcher.png
    sea slug launcher.png
    7.8 KB · Views: 122
Red Hand proposed development plan produced in June1950 included JTV1 /JTV2 and CTV4. it was the original name for what became Bloodhound while the design was still MRJW 410 and had forward mounted boost motors. JTV1 Mk 1 Trials as Larkhill showed forward mounted boost motors and wing mounted Ramjet did not get on together. Only place I have ever seen Red Hand mentioned is in a Bloodhound File at Kew (AVIA 54-1224). First Mention of Red Duster in the Document is after X-9 configuration selected and weapon moved to the Army.
Top Bottom