Sea Wolf and Sea Dart: Unbuilt Derivatives and Cancelled Applications

[Dilandu]

Because the range will inevitably be extended to beyond-the-horizon,

"Inevitably" is a rather poor celling point for converted SAM, which main advantage is that it build on basic of existing missile. A major efforts to reconfigure Sea Dart into fire-and-forged ASM would be required. At some point, the question would inevitably arise "wouldn't it be simpler to just design a new missile from scratch?"

Do not forget, at this point of development (mid-1970s at best) there was no Sea Dart mod 2 even in theory. The possibility of extended range Sea Dart was just theoretical, and missile didn't even have autopilot yet. So the longer range Sea Dart was far from "inevitable"; it was something theoretically possible but pretty far in the future.

 

[Martes]

Why bother, if the missile only have range to operate within the horizon? You need to fit a new seeker, an automomous autopilot - all the way battling the missile architecture limitations - to provide it with the capabilty it doesn't even need?

Historically, we know the range limit is not a given and was extended and this option would have to be explored anyway. Because the question would have been asked. Can you do a) beyond the horizon and b) radar seeker. It could take time, and very possibly it could have been implemented only during the work on Mod 2 - all depending on requirements and budget.

If you have a surface enemy within 37 km, it likely a top priority anyway.

Right. You fire 2 surface-surface missiles and have your illuminators ready for AA fire immediately, instead of waiting very precious seconds. Or you fire one and can reserve the second rail for AA.

 

[Dilandu]

Which means the missile does not occupy a very premium illumination channel.

Which also means that missile is much more prone to jamming, much more like to be decoyed, ect. The advantage of SARH is that you coudl use big bad shipborbe radar with excessive power and massive signal processing and computing capabilities to illuminate the target. At 37 km range, it would be VERY hard to jam (the beam would just burn through) and almost impossible to decoy (the target is observed visually, after all)

Going for ARH, you put all the pressure of finding, locking & tracking target on the missle own feeble seeker. Which - in case of Sea Dart - is inefficient pretty much by definition (interferometer antenna is just not very good). It could easily be jammed - the missile have much less power to radiate, and the receiver is vulnerable. It could easily be decoyed - the processing capabilities of 1960s vacuum tube tech aren't exactly great, and with the unimpressive seeker, even just a chaff cloud would be very hard to discriminate.

So essentially its a lot of efforts for a dubious results.

 

[Martes]

So essentially its a lot of efforts for a dubious results.

It wasn't built, was it?

What I am trying to say is that a feasible variant would have to have both ARH and OTL capabilities, otherwise the secondary surface targeting of the original missile would be sufficient. It was fired on a ship hulk once at least, and it was considered rather impressive, IIRC.

 

[Dilandu]

Historically, we know the range limit is not a given and was extended and this option would have to be explored anyway.

Yes, by late 1980s. Almost twenty years after.

Because the question would have been asked.

OTL, Royal Navy settled for Exocet because it was cheaper, range clearly wasn't viewed as very important.

a) beyond the horizon and

No, because 1973s missile did not have neither range nor homing capacity to go beyond the horizon.

b) radar seeker

Likely no, because the missile architecture is not suitable for any efficient seeker.

could have been implemented only during the work on Mod 2 - all depending on requirements and budget.

By the 1989, the sea-skimming Sea Dart would not look impressive at all.

Right. You fire 2 surface-surface missiles and have your illuminators ready for AA fire immediately, instead of waiting very precious seconds. Or you fire one and can reserve the second rail for AA.

It may be useful only in a very limited sets of engagement, while you simultaneously have enemy ship within the horizon and enemy aircraft attacking at the same time. Not exactly a common scenario, and anyway, the enemy warship is much more direct threat.

 

[Martes]

By the 1989, the sea-skimming Sea Dart would not look impressive at all.

Depending on range - even on M1.5 it's thrice as fast as a Harpoon, has the same target size and is a proper headache to shoot down.

 

[Dilandu]

What I am trying to say is that a feasible variant would have to have both ARH and OTL capabilities

And I'm trying to explain, that ARH seeker on Sea Dart would likely not work at all due to missile architecure limitations, would be very limited in capacity even if it would work, and would require somehow finding space for autopilot (and there are no laser gyros yet).

Also, the extending of Mod 2 range was mainly the result of installing autopilot. The missile could now use more energy efficient semi-ballistic trajectory, instead of running straight toward the enemy.

So to extend the range of the anti-ship Sea Dart the approach would be to use combined, high-low trajectory. It would basically defeat the main idea of sea-skimming - to stay below horizon for enemy as long as possible. Large Soviet supersonic could afford this, since they have a range & brains to actually make complex approach. The Sea Dart is neither long range enough, nor smart enough.

 

[Dilandu]

Depending on range - even on M1.5 it's thrice as fast as a Harpoon, has the same target size and is a proper headache to shoot down.

It would be much more noticeable due to both the missile air intake increasing RCS and its seeker emitting on rather high power. While it would be harder to hit (AK-630 may have other opinion, though), it would be easier to decoy.

 

[Martes]

And I'm trying to explain, that ARH seeker on Sea Dart would likely not work at all due to missile architecure limitations

We had here an actual person who worked on the missile, and he sounded more confident in the possibility to solve this, and much more worried about fuel flammability.

 

[Dilandu]

We had here an actual person who worked on the missile, and he sounded more confident in the possibility to solve this, and much more worried about fuel flammability.

He admitted, that he never heard anything about any kind of over-the-horizon seeker, so what is your point?

 

[Martes]

He admitted, that he never heard anything about any kind of over-the-horizon seeker, so what is your point?

And immediately suggested a seeker configuration.

My point is that if I came to him from the Admiralty with those papers then, I would get the same answer and probably could sign off some tests.

 

[Dilandu]

And immediately suggested a seeker configuration.

Which is basically the same as I suggested before - some kind of immobile more-or-less directional antenna with electronic scanning as transmitter, and interferometer array as receiver. While it MIGHT work, it would likely be highly inefficient.

 

[Martes]

While it MIGHT work, it would likely be highly inefficient.

Attitude. He didn't try to dissuade us
And neither considered this a primary problem.

 

[Dilandu]

Attitude. He didn't try to dissuade us
And neither considered this a primary problem.

Well, I consider this a primary problem. With all respect to Zoo Tycoon, but we both are speculating here.

 

[Martes]

It's a matter of historical reconstruction.

We - at this time - can speculate whether it could work or not, but he brought us the primary source insight of how exactly the contemporary development team would approach such request.

 

[Dilandu]

We - at this time - can speculate whether it could work or not, but he brought us the primary source insight of how exactly the contemporary development team would approach such request.

No. He suggested that such approach might be tried, not how exactly.

The most probable approach - assuming that the whole idea of OTH sea-skimmer would not be rejected immediately on the point of major contradictions (not enough range to validate, no place for autopilot, no way of installing normal seeker) would likely be to just use passive guidance on enemy radar. Which could be implemented even on interferometer seeker (as Talos-ARM demonstrated).

 

[Martes]

use passive guidance on enemy radar.

Now that's an interesting option.

 

[zen]

Of course at such a range as 37km, a much weaker signal could guide the missile. So arguably a helicopter or jet aircraft could provide this.

With a low level speed in excess of Mach 1.5, it would cross that distance in short order. Meaning the duration and risk for the illuminating aircraft is kept to a minimum.

 

[NMaude]

Of course at such a range as 37km, a much weaker signal could guide the missile. So arguably a helicopter or jet aircraft could provide this.

With a low level speed in excess of Mach 1.5, it would cross that distance in short order. Meaning the duration and risk for the illuminating aircraft is kept to a minimum.

So basically a supersonic version of the Sea Skua.

 

[Scott Kenny]

The most probable approach - assuming that the whole idea of OTH sea-skimmer would not be rejected immediately on the point of major contradictions (not enough range to validate, no place for autopilot, no way of installing normal seeker) would likely be to just use passive guidance on enemy radar. Which could be implemented even on interferometer seeker (as Talos-ARM demonstrated).

That's certainly how I'd want to do it.

Though Talos was a far more massive missile that hit harder than a 16" gun.

 

[NMaude]

Though Talos was a far more massive missile that hit harder than a 16" gun.

Several SA-2 Guideline batteries found that out the hard way in North Vietnam when their Fan Song radar units were obliterated (Along with their crews) by RGM-8H Talos-ARMs.

 

[zen]

Mach 1.5 at sea level is about 670kts (nautical miles per hour).

So 67nm is covered in 6 minutes.

37km is 20nm
So unless my math is wrong...

At that speed the missile would cover the distance in 1.8 minutes or 108 seconds.

 

[Dilandu]

Though Talos was a far more massive missile that hit harder than a 16" gun.

True. Sea Dart is much smaller & lighter. Still, it's a mach 2 missile, with a kinetic energy of heavy gun fired point-blank (abeit less than 16-inch one) The sea-skimmer anti-ship version was supposed to carry a much heavier warhead, to remedy the prolebm.

 

[Martes]

It was fired on a ship hulk once at least, and it was considered rather impressive, IIRC.

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.

 

[Dilandu]

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.

Impressive!

 

[NMaude]

Impressive!

Yeah, the missile operators in HMS Bristol must've had a lot of fun at punching a hole in a destroyer to see if they could sink it (Which they almost). According to the HMS Rapid wikipedia article after it was repaired it was finally torpedoed as a target for an RN submarine in 1981.

 

[Dilandu]

Yeah, the missile operators in HMS Bristol must've had a lot of fun at punching a hole in a destroyer to see if they could sink it (Which they almost). According to the HMS Rapid wikipedia article after it was repaired it was finally torpedoed as a target for an RN submarine in 1981.

The general destructive power of supersonic missile hitting at Mach 2+ is often underestimated. Many peoples are quite shocked when they realize that "flimsy missile" is actually a pretty strong metal pipe with a weight and velocity of 16-inch shells fired point-blank - or more - and could break armor plates through simple kinetic energy.

 

[Mike Pryce]

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.

There is a photo of the aftermath that was used in an old HSD/BAeD advert. IIRC I saw it in an old British Defence Equipment Catalogue.

 

[NMaude]

There is a photo of the aftermath that was used in an old HSD/BAeD advert. IIRC I saw it in an old British Defence Equipment Catalogue.

Is there a video of the test on YouTube?

 

[Mike Pryce]

Is there a video of the test on YouTube?

Not that I know of. The advert was a pair of pictures of the Sea Dart about to hit, and then the hole in the side I think.

I flicked past it 20 years ago and just remember thinking 'I did not know Sea Dart could be used like that'. I guess the photos may well be stills from a cine film of the test.

I also have a dim memory of an FPB being used as a target.

 

[CJGibson]

My notes on Sea Dart SSM

On 15 October 1970, the Chairman of the ORC raised the possibility of adapting the Sea Dart SAM to the surface-to-surface guided weapon role (SSGW) with a range comparable with the Exocet. It would arm the ships being fitted with the Sea Dart SAM; Bristol and the Type 42. However, the chairman pointed out that ‘the tactical undesirability of using a SAM system for surface fire is restated’.

Range is 39,000 yards against a cruiser, 35,000 yards against a frigate and 22,000 yards against as FPB. Exocet has a range of 40,000 yards against targets larger than frigates.

A modification to the Type 909 from 1974 will remove the ‘present severe weather limitations on the surface range of Sea Dart’.
Sea Dart carries a small AA warhead but ‘its high terminal speed (M2.5) causes considerable amount of kinetic energy to be released on impact, giving a missile which reaches the target a 90% chance of causing category B damage.’ On the other hand, NSR.6532 requires Exocet to ‘have at least 65% probability of causing category B damage.’

The AA warhead would be replaced with a semi-armour piercing (SAP) warhead weighing in at 140lb.

The centre island would be extended by 6in to accommodate the SAP warhead.

Radio fuze removed and space used for other equipment

Radio altimeter fitted

Cuckoo boost extended by 4in

Use of higher density fuel i.e. Shelldyne.

Remove fuze aerials to reduce drag.

HSD proposed fitting the Sea Dart SSM in deck boxes a la Exocet. Four boxes would allow salvo fire.

However, Sea Dart SSM would occupy a 909 and thus reduce the effectiveness of the vessel in the area air defence role, hence the undesirability of this proposal.

Chris

 

[Dilandu]

My notes on Sea Dart SSM

Thank you for the data!

 

[Zoo Tycoon]

HMS Leander was also hit with a Sea Dart during a Sinkex in 1989 ….together with 3 Harpoons. There may be some film about.

I’ve can also remember the HMS Rapid photo as well, big can opener comes to mind, lots of damage.

 

[NMaude]

Remove fuze aerials to reduce drag.

I assume you're referring to the proximity-fuse's aerials?

 

[CJGibson]

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

Chris

 

[Hood]

This thread has a little info on the use of Type 909 against surface targets.

https://www.arrse.co.uk/community/threads/improvised-use-of-missiles-in-non-intended-roles-and-converted-adapted-missiles.314347/page-5#post-12215635

 

[Mike Pryce]

My notes on Sea Dart SSM

On 15 October 1970, the Chairman of the ORC raised the possibility of adapting the Sea Dart SAM to the surface-to-surface guided weapon role (SSGW) with a range comparable with the Exocet. It would arm the ships being fitted with the Sea Dart SAM; Bristol and the Type 42. However, the chairman pointed out that ‘the tactical undesirability of using a SAM system for surface fire is restated’.

Range is 39,000 yards against a cruiser, 35,000 yards against a frigate and 22,000 yards against as FPB. Exocet has a range of 40,000 yards against targets larger than frigates.

A modification to the Type 909 from 1974 will remove the ‘present severe weather limitations on the surface range of Sea Dart’.
Sea Dart carries a small AA warhead but ‘its high terminal speed (M2.5) causes considerable amount of kinetic energy to be released on impact, giving a missile which reaches the target a 90% chance of causing category B damage.’ On the other hand, NSR.6532 requires Exocet to ‘have at least 65% probability of causing category B damage.’

The AA warhead would be replaced with a semi-armour piercing (SAP) warhead weighing in at 140lb.

The centre island would be extended by 6in to accommodate the SAP warhead.

Radio fuze removed and space used for other equipment

Radio altimeter fitted

Cuckoo boost extended by 4in

Use of higher density fuel i.e. Shelldyne.

Remove fuze aerials to reduce drag.

HSD proposed fitting the Sea Dart SSM in deck boxes a la Exocet. Four boxes would allow salvo fire.

However, Sea Dart SSM would occupy a 909 and thus reduce the effectiveness of the vessel in the area air defence role, hence the undesirability of this proposal.

Chris

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

 

[Scott Kenny]

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

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!

 

[NMaude]

For a low-altitude shot the range is also likely effected by the sea-state too.

 

[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.