Sea Dart missile guidance

[yellowaster]

The Sea Dart (UK naval missile) had an interferometer guidance system - evident by the four polyrod antenna surrounding the nose. I have always assumed that the guidance system also incorporated an auxiliary dish antenna in the missile nose cone (a technique used to improve the angular accuracy of/eliminate ambiguity of the interferometer). I can't seem to find a definite reference to confirm this. Anyone have such a reference ?

 

[Zoo Tycoon]

I don’t recall seeing such, the warhead, including a contact fuse, sat behind the aero spike pretty much taking up the whole of the forebody, so there wasn’t much space for a dish, particularly if articulated. The forebody complete with warhead came to us as a fully made up module so never got a close look inside.

 

[TomS]

Looking at some pictures, it looks like there might be a 5th rod antenna on the nose, but probably not a dish. See this one, for example.

 

[timmymagic]

Looking at some pictures, it looks like there might be a 5th rod antenna on the nose, but probably not a dish. See this one, for example.

Is that Chevaline in the top left? Was this at Cosford?

 

[red admiral]

Looking at some pictures, it looks like there might be a 5th rod antenna on the nose, but probably not a dish. See this one, for example.

Air data probe?

Is that Chevaline in the top left? Was this at Cosford?

Bristol's museum at Kemble, now moved to Filton. Also the dual SRAAM launcher in that picture.

 

[CJGibson]

Is that Chevaline in the top left? Was this at Cosford?

Yes and No, Bristol Collection last century. It's my photo.

I took a load of snaps of the Chevaline vehicle at FAST the other week. Includes a rather nice scale model.

Chris

 

[yellowaster]

In case anyone is interested, I did a bit more research on this. Found a Royal Radar Establishment document c.1967 which describes the guidance system as "compound dish-interferometer" which seems to confirm the presence of a dish. Conical radome may have been Pyroceram. Also came across an interesting book "Radar Homing Guidance For Tactical Missiles", DA James, Macmillan Education, 1986 which describes use of auxiliary dish in an interferometer a system. Put-on to target at launch and then by LOS gyro during flight. It restricts field of view of interferometer (signal must be present in dish to enable interferometer output) in order to eliminate ambiguities (side-lobes?).

 

[Zoo Tycoon]

In case anyone is interested, I did a bit more research on this. Found a Royal Radar Establishment document c.1967 which describes the guidance system as "compound dish-interferometer" which seems to confirm the presence of a dish. Conical radome may have been Pyroceram. Also came across an interesting book "Radar Homing Guidance For Tactical Missiles", DA James, Macmillan Education, 1986 which describes use of auxiliary dish in an interferometer a system. Put-on to target at launch and then by LOS gyro during flight. It restricts field of view of interferometer (signal must be present in dish to enable interferometer output) in order to eliminate ambiguities (side-lobes?).

I worked on the propulsion side of Sea Dart so had only a limited dealing with guidance. I did the Sea Dart “101” course when I joined the team in late 83, where a fair bit of this was explained…. Wow 40years ago next month, alas forgotten.

Is the dish fixed or can it be pointed ? I would really appreciate of a quick reminder of how the interferometers aerials achieve there RF directional properties.

 

[yellowaster]

My understanding is that interferometer uses phase difference of signal arriving at an antenna pair to determine angle of arrival. Two antenna pairs used in Sea Dart. The auxiliary dish moves - it's kept pointed at the target by the guidance system and effectively limits the field of view of the interferometer so that only signals from a defined arc centred roughly on target position are processed.