Sea Wolf and Sea Dart: Unbuilt Derivatives and Cancelled Applications

[Mike Pryce]

Probably because the distance they can be seen over the horizon isn't as far.

Wait, that probably doesn't make any sense if you haven't had lookout training.

• Imagine a picture of a ship. The horizon is obviously behind it, and is probably even above the weather deck of the ship. Been long enough I don't remember the formal name for that. Usually called out as a distance to the horizon, "three-quarters to horizon," but if you remembered your horizon distance (based on how high you were up off the waterline yourself) you could guesstimate ranges pretty well.
• Now make it farther away from you, so you can still see all the way down to the waterline but the waterline is on the horizon. That's "on the horizon".
• Now make that ship even farther away from you, so that the horizon crawls up the hull from the waterline, say to the weather deck. That's "hull down on the horizon".
• Finally, make it so far away that the horizon covers up the superstructure and even the masthead. Completely out of sight.

The smaller the ship, the closer the distance between "Hull down on the horizon" and "on the horizon" is.

Wish I had the Paint skills to draw this out, it'd be a lot easier!

I used to watch ships along the English Channel from out the window of my old home. Odd to see containers moving along but the ship invisible.

My clutter comment was based on thinking at some distance only masts would be seen. Presumably they get lost in the clutter from waves, and that distance would be closer on smaller ships.

Without knowing the 909 radar height it's hard to know the distance to the radar horizon though.

 

[Dilandu]

Dumb question from me, but why is range shorter for smaller targets? Clutter?

The missile is semi-active homing on the radar echo from the target, illuminated by ship's radar. So the enemy ship must be visible above horizon. The smaller (and lower) the enemy ship is, the less distance from which it would be visible.

 

[Zoo Tycoon]

I assume so as the radio fuze was to be removed.

Chris

The original em fuse sensed the water so was a no go for a sea skimmer. For the Mod 0 to Mod 2 missiles it was inhibiting if doing a surface attack. The Mod 3 fixed this problem by replacing it with an IR fuse.

 

[Scott Kenny]

I used to watch ships along the English Channel from out the window of my old home. Odd to see containers moving along but the ship invisible.

My clutter comment was based on thinking at some distance only masts would be seen. Presumably they get lost in the clutter from waves, and that distance would be closer on smaller ships.

Without knowing the 909 radar height it's hard to know the distance to the radar horizon though.

Jane's will tell you the masthead height. Which IIRC is close enough to the radar horizon for government work.

Also, all the right angles on most masts make excellent radar reflectors. Subs and sailboats use ~8"-12" diameter "balls" made of 3 sheets of aluminum meeting at right angles as radar reflectors.

 

[Dilandu]

Jane's will tell you the masthead height. Which IIRC is close enough to the radar horizon for government work.

Also, all the right angles on most masts make excellent radar reflectors. Subs and sailboats use ~8"-12" diameter "balls" made of 3 sheets of aluminum meeting at right angles as radar reflectors.

Exactly. As long as at least some part of the ship is above horizon, there is a reflection for SARH seeker to work with. Of course, the common problem in targeting the mast tops is that missile might aim too high & miss the hull - but sea-skimmer Sea Dart, moving at constant altitude, would not have such problem.

 

[Martes]

but sea-skimmer Sea Dart, moving at constant altitude, would not have such problem.

And this, theoretically, should also fix the point of impact in case of radiation homing device, as you suggested.

 

[Dilandu]

And this, theoretically, should also fix the point of impact in case of radiation homing device, as you suggested.

Exactly. Assuming, of course, that the target isn't so low, that the missile overshoot it. Albeit a terminal glide-dive at pre-set angle could be programmed in that case, at least for SARH version (triggered by the strength of echo reaching a specific level as a crude range measure).

 

[SeaslugMk2]

Sea Dart surface-to-surface.

A trial shoot against HMS Rapid.

On the 16th October 1975 HMS Bristol carried out a surface-to-surface test firing of a Sea Dart missile at the Aberporth test facility. The target was the destroyer HMS Rapid, moored 17187 yards away at 280°, the sea state was between 1 and 2 and the wind speed was 10Kts.
The launcher was on a bearing of 105°Red (ie to port) and the missile was launched at 16:18 at at elevation of 28·5°. The missile was an operational round, serial JZ35, with a weight of 1208lbs at launch and approximately 600lbs at impact. As intended, the fuze and warhead were not armed.
The missile struck HMS Rapid at 2200 feet per second on the waterline between frames 38 and 39, just above No3 deck, and exploded just after impact. The missile may have skidded down the ship's side plating before catching on the first of three half-round rubbing bands and penetrating the hull.
A large hole was blown in the side of the ship, and had No1 boiler room bulkhead not remained intact and watertight the ship would have foundered. A target of this size would have ceased to be able to continue fighting.

Source: The National Archives file ADM 281/326.

Cue Peter Sellers’ Fu Manchu: “Haven’t I seen you somewhere before?”



Fair’s fair; you did link to my article. I can’t believe I wrote it over four years ago!

SRJ

 

[SeaslugMk2]

…The really difficult bit with Shelldyne was that it’s pyrophuric which was a big problem for the RN….

Are you sure that Shelldyne is pyrophoric? This document (https://apps.dtic.mil/sti/trecms/pdf/AD0703691.pdf) shows that Shelldyne is harder to ignite than JP4.

SRJ

 

[Yellow Palace]

Of course, the common problem in targeting the mast tops is that missile might aim too high & miss the hull - but sea-skimmer Sea Dart, moving at constant altitude, would not have such problem.

Proximity-fused expanding rod warheads also help with this problem, if one is employing a surface-to-air missile as a surface-to-surface weapon. Makes a right mess of a small warship, as the Turkish destroyer MUAVENET could have told you.

Granted that's not what was proposed for Sea Dart, but it is how the USN employs Standard.

 

[Martes]

Fair’s fair; you did link to my article.

Quite like the post about the sea-skimming project I brought above -

https://www.tapatalk.com/groups/warships1discussionboards/sea-skimming-sea-dart-t39442.html

I was very surprised I couldn't find both of them here, so I assumed they are worth to be linked and probably duplicated.