Harpoon antiship missile with torpedo warhead.

[Hanse]

I could swear I've read somewhere that at one time they'd considered swapping out the Harpoon's 500lb blast warhead for a lightweight torpedo (Mk46) but decided it would be too hard to target. Anybody recall anything about this? I haven't been able to find anything on it.

 

[Brickmuppet]

There is a brief mention in Gunston's ROCKETS AND MISSLES on p82 " The Naval Weapons Center and MDAC are also studying possible variations with supersonic speed, torpedo carrying payload, imaging IR homing, passive radiation homing, nuclear warhead, vertical launch, mid-course guidance updating and other features. "

 

[isayyo2]

I could swear I've read somewhere that at one time they'd considered swapping out the Harpoon's 500lb blast warhead for a lightweight torpedo (Mk46) but decided it would be too hard to target. Anybody recall anything about this? I haven't been able to find anything on it.

There is a brief mention in Gunston's ROCKETS AND MISSLES on p82 " The Naval Weapons Center and MDAC are also studying possible variations with supersonic speed, torpedo carrying payload, imaging IR homing, passive radiation homing, nuclear warhead, vertical launch, mid-course guidance updating and other features. "

Sorry this is a few years late...

In Friedman's U.S. Submarines I came across "Tarpon" a Harpoon with a Mk46 Torpedo as a follow up to the abortive STAM design.

 

[NMaude]

I could see the USN resurrecting this idea and create a Harpoon variant where the payload is instead of the radar seeker and its' 500Lb warhead an encapsulated Mk-54 lightweight torpedo instead (With a retarding-parachut attached to it).

Now didn't the French navy have something like this for a while? I think it was called Malathon?

Edit: I did some checking around and it's called Malafon.

 

[TomS]

Malafon and the Australian/UK Ikara were rocket-boosted gliders: Malafon with a short heavyweight torpedo and Ikara with a lightweight. The closest equivalent to this Tarpon is MILAS, an Otomat turbojet-powered missile with a lightweight torpedo payload.

I think MILAS ended up rather longer than Otomat, and Tarpon might have done the same -- the torpedo and parachute pack is likely longer than the original warhead and seeker.

 

[NMaude]

The closest equivalent to this Tarpon is MILAS, an Otomat turbojet-powered missile with a lightweight torpedo payload.

I'd forgot about MILAS.

 

[Hood]

Oddly Friedman makes no mention of Tarpon in British Submarines in the Cold War Era despite the serious consideration he mentions in US Submarines. He does mention that;

About 1976, lists of future British missile projects, prepared in the context of the Sub-Harpoon decision, included a submarine-fired ASW missile, not yet assigned a project number, to begin development in the late 1980s and enter service in the 1990s. It is not clear whether that ever happened.

This I suppose is an oblique reference to the Tarpon concept, presumably the ASW missile was a future wish list item that went no further.

 

[Hanse]

Oddly Friedman makes no mention of Tarpon in British Submarines in the Cold War Era despite the serious consideration he mentions in US Submarines. He does mention that;

About 1976, lists of future British missile projects, prepared in the context of the Sub-Harpoon decision, included a submarine-fired ASW missile, not yet assigned a project number, to begin development in the late 1980s and enter service in the 1990s. It is not clear whether that ever happened.

This I suppose is an oblique reference to the Tarpon concept, presumably the ASW missile was a future wish list item that went no further.

Probably referring to Sea Lance.

Boeing RUM/UUM-125 Sea Lance

 

[NMaude]

Probably referring to Sea Lance.

Boeing RUM/UUM-125 Sea Lance

A pity that it never went into production.

 

[TomS]

I could swear I've read somewhere that at one time they'd considered swapping out the Harpoon's 500lb blast warhead for a lightweight torpedo (Mk46) but decided it would be too hard to target. Anybody recall anything about this? I haven't been able to find anything on it.

There is a brief mention in Gunston's ROCKETS AND MISSLES on p82 " The Naval Weapons Center and MDAC are also studying possible variations with supersonic speed, torpedo carrying payload, imaging IR homing, passive radiation homing, nuclear warhead, vertical launch, mid-course guidance updating and other features. "

Sorry this is a few years late...

In Friedman's U.S. Submarines I came across "Tarpon" a Harpoon with a Mk46 Torpedo as a follow up to the abortive STAM design.

View attachment 698287

In US Naval Weapons, Friedman also mentions that during the 1970s, Tarpon was periodically considered as an ASROC replacement for surface ships. Since Harpoon could be fired from suitably modified ASROC launcher cells (beginning in 1976, the Knox class ASROC launchers were modified with two Harpoon-capable cells, for example), this would probably have been fairly straightforward. But the question becomes whether the ships could really detect subs reliably at 50-75 miles and whether they could localize targets at that range well enough to drop a lightweight torpedo within acquisition distance (especially without mid-course steering updates).

 

[isayyo2]

In US Naval Weapons, Friedman also mentions that during the 1970s, Tarpon was periodically considered as an ASROC replacement for surface ships. Since Harpoon could be fired from suitably modified ASROC launcher cells (beginning in 1976, the Knox class ASROC launchers were modified with two Harpoon-capable cells, for example), this would probably have been fairly straightforward. But the question becomes whether the ships could really detect subs reliably at 50-75 miles and whether they could localize targets at that range well enough to drop a lightweight torpedo within acquisition distance (especially without mid-course steering updates).

Perhaps DASH/LAMPS/SH-3 providing mid-course guidance?

 

[Hanse]

Would be nice if BAMS UAVs would be able to upload contacts and let those with the means prosecute them. CEC for ASW. With VL-ASROC you're pretty limited. Put a lightweight torpedo in a Tomahawk and let it fly. Or put it on ATACMS if you need more speed. (Or PrSM.)

 

[TomS]

In US Naval Weapons, Friedman also mentions that during the 1970s, Tarpon was periodically considered as an ASROC replacement for surface ships. Since Harpoon could be fired from suitably modified ASROC launcher cells (beginning in 1976, the Knox class ASROC launchers were modified with two Harpoon-capable cells, for example), this would probably have been fairly straightforward. But the question becomes whether the ships could really detect subs reliably at 50-75 miles and whether they could localize targets at that range well enough to drop a lightweight torpedo within acquisition distance (especially without mid-course steering updates).

Perhaps DASH/LAMPS/SH-3 providing mid-course guidance?

Thinking 1970s timeframe here: If you have any of these up and working, you might as well use them to relocalize and drop direct on the contact.

You could fly Tarpon higher than Harpoon so you could have a direct line-of-sight datalink back to the launch ship. But the basic question remains -- is a convergence zone (CZ) target location precise enough to dump a lightweight torpedo on? They don't have super-long acquisition range and long-distance ASW detection is notoriously vague. Basically, with CZ detection, you know the contact is in the CZ somewhere. And the CZ is probably a few miles wide, 20-30 miles away (60 miles if you're really lucky and get a second CZ detection). So you get a contact that you see for maybe 5-10 minutes with a an uncertainty of up to a couple of miles in range and hopefully not too many degrees in angle. Then have to extrapolate the likely course of advance for the sub, launch the missile, and hope you drop the torpedo within about a half mile of the submarine's track.

This is why the Tomahawk equivalent of this concept actually had onboard sonobuoys, to relocalize the target before dropping the torpedo.

 

[Yellow Palace]

This is why the Tomahawk equivalent of this concept actually had onboard sonobuoys, to relocalize the target before dropping the torpedo.

The alternative is the ASW-SOW approach, of using a 200 kiloton nuclear depth charge with a rapid flyout to obliterate everything in the area of uncertainty.

 

[TomS]

This is why the Tomahawk equivalent of this concept actually had onboard sonobuoys, to relocalize the target before dropping the torpedo.

The alternative is the ASW-SOW approach, of using a 200 kiloton nuclear depth charge with a rapid flyout to obliterate everything in the area of uncertainty.

True. Also, SUBROC. And of course ASROC's most lethal version was the nuke depth charge. For a long time, I suspect the torpedo version was just a fig leaf and they expected to use only the nukes in wartime.

 

[NMaude]

For a long time, I suspect the torpedo version was just a fig leaf and they expected to use only the nukes in wartime.

IIRC one of the RUR-5 ASROC's payload was the Mk-45 torpedo equipped with a W34 warhead.

 

[TomS]

For a long time, I suspect the torpedo version was just a fig leaf and they expected to use only the nukes in wartime.

IIRC one of the RUR-5 ASROC's payload was the Mk-45 torpedo equipped with a W34 warhead.

No. Mk 45 was a sub-launched torpedo that weighed over a ton. (RUR-5 all up was around a half-ton).

The payloads for ASROC were lightweight torpedoes (originally Mk 44 and later Mk 46) or the W44 10-kt nuclear depth bomb.

 

[Hood]

I doubt that the full Harpoon range would be utilised for Tarpon given the different payload and need to keep length more or less compatible with an ASROC launcher or Harpoon cannister (less likely).
If we take Metel as an example, max range with an A/S torp was 31 miles, but 56 miles when used for anti-ship with an 85kg warhead.

I agree its hard to see how the full range of Harpoon could be utilised. I suppose using LAMPS III to lay a sonobuoy barrier might help, but then its not really a rapid-reaction response if you're reliant on that sonobuoy barrier (and you might as well use LAMPS to drop the torpedo/nuke).

I suspect the idea was to counter the Charlie-classes (to hit them before they can launch) which Tarpon might have been able to match - P-70 65km aboard Charlie I and P-120 (70-110km) aboard Charlie II. Of course by the mid-70s the impending P-700 on Oscar threat presents a whole different threat level to which only advance screens can counter.

 

[Yellow Palace]

I doubt that the full Harpoon range would be utilised for Tarpon given the different payload and need to keep length more or less compatible with an ASROC launcher or Harpoon cannister (less likely).
If we take Metel as an example, max range with an A/S torp was 31 miles, but 56 miles when used for anti-ship with an 85kg warhead.

For a similar concept in the West, MILAS is credited with 35km range, compared to 180km for Otomat Mk 2.

 

[Dilandu]

Well, USSR implemented such approach in the "Metel"/"Rastrub" anti-submarine missiles with torpedo warheads ("Rastrub" also was equipped witn shaped-charge warhead & infrared seeker to use against surface ships). They were launched with the help of external targat tracking - from helo, plane or other ship - flew to the target location, recieving mid-course guidance commands from parent ship, and then drop the torpedo in water, to seek&destroy.

 

[TomS]

I doubt that the full Harpoon range would be utilised for Tarpon given the different payload and need to keep length more or less compatible with an ASROC launcher

Yeah, the geometry is difficult. The Harpoon seeker and warhead are about half the overall length of the missile, roughly 6.5 feet. A lightweight torpedo is a good 2 feet longer, not even counting the parachute pack. Fortunately ASROC is already about 1.6 feet longer than surface-launched Harpoon, but you still need to shave a foot or more off the total for the parachute and the midcourse guidance system. Problem is, the inlet for the jet engine on Harpoon starts almost immediately behind the warhead and runs the length of the fuel tank. So you can't just cut out fuel to get the length down, you may have to rework the whole inlet geometry.

 

[TomS]

Harpoon cannister (less likely).

And what do you know, here is a 1974 concept for a hydrofoil escort incorporating Tarpon in Harpoon-style launch tubes.

https://foils.org/wp-content/uploads/2017/10/0186-High-Endurance-Escort-Hydrofoil-For-the-Fleet-Aroner-Hubbard-Feb-74-1.pdf

 

[Brickmuppet]

I wonder if the 60-80 nautical mile range of Harpoon was not intended to hit targets at 60-80 NM but rather to give Tarpon a degree of loitering capability while the targeting solution was perfected or perhaps give time for a lost/intermittent target to be re-acquired at much shorter ranges. I don't know how much time to adjust targeting this reduction in range might realistically give.

 

[TomS]

I wonder if the 60-80 nautical mile range of Harpoon was not intended to hit targets at 60-80 NM but rather to give Tarpon a degree of loitering capability while the targeting solution was perfected or perhaps give time for a lost/intermittent target to be re-acquired at much shorter ranges. I don't know how much time to adjust targeting this reduction in range might realistically give.

I am pretty sure that Tarpon would not have matched Harpoon's range. The fuel tank would be smaller and it would probably fly a bit like SLAM (nose-up) unless they rejiggered the wings as well.

Speaking of which, I did not realize that the various versions of Harpoon have different wing sets (they fold differently for different applications). It looks like the ASROC launcher and Tartar versions may even have different boosters.

 

[isayyo2]

And what do you know, here is a 1974 concept for a hydrofoil escort incorporating Tarpon in Harpoon-style launch tubes.

Looks a like great alternative to the Mk 16 ASROC launcher. Should be a few tons lighter than the under deck reload magazine too.

Do the fixed Mk 141 launchers need much, if any maintenance while underway?

 

[Dilandu]

I am pretty sure that Tarpon would not have matched Harpoon's range. The fuel tank would be smaller and it would probably fly a bit like SLAM (nose-up) unless they rejiggered the wings as well.

Hm, but it could climb to higher altitude - after all, submarines did not require low-altitude approach.