Wednesday, November 25, 2015

Harpoon Block II+ - What Changed In Three Minutes?

The Navy is in the process of testing the Harpoon Block II+ missile.  The main feature of the II+ is the ability to accept in-flight guidance.

Is that really a big deal?  Or even a moderately worthwhile capability?

Harpoon has a range of 60 miles and a speed of 540 mph.  Doing the math, that translates to 9 miles per minute.  Thus, at max range, the Harpoon will cover the distance to the target in 6.6 minutes.  Is there really going to be a need to update the targeting in 6.6 minutes?  A ship target moving at 30 kts, for example, will move 3.3 nm in 6.6 minutes – presumably still well within the Harpoon seeker range – and that’s the worst case of max range and max target speed. 

Presumably, the mid-course guidance (it’s called “mid-course” because it happens part way through the flight, not at the last second) would take place at around the 3 or 4 minute mark of the flight.  Seriously?  Is there really a need for mid-course flight path changes after 3 or 4 minutes?  Even a very fast ship would only have moved a mile or two and most targets less than that.  Presumably, we had a pretty good target fix when we launched.  It won’t have changed that much!  Yes, we can launch on bearing only but if that’s all we had at launch, we’re not going to have any better data 3 or 4 minutes later.

For any case of less than max range or less than max target speed, the need for mid-course guidance just goes from not realistically needed to utterly not needed.  There just seems to be little need for mid-course guidance updates.  This seems like a capability that sounds nice when you say it but is not worth the cost and added complexity.  Remember, not only does the Harpoon have to carry additional equipment (cost and complexity as well as weight) but whatever guiding platform there is has to have a transmitter capable of sending signals in whatever format is required (cost and complexity).

By the way, what platform is going to provide the mid-course guidance data?  Any platform that has a good enough fix on the target at the moment of mid-course correction almost certainly had the same good fix at launch with exact knowledge of location, course, and speed thus rendering the need for mid-course guidance moot.

Honestly, I get the feeling that this is just a hyped capability designed to get more developmental funding for the manufacturer.  This is a solution looking for problem.  There’s a lot of things I’d rather spend the developmental money on than this.


  1. "In production at Boeing facilities in Saint Charles, Missouri, is the Harpoon Block II, intended to offer an expanded engagement envelope, enhanced resistance to electronic countermeasures and improved targeting. Specifically, the Harpoon was initially designed as an open-ocean weapon. The Block II missiles continue progress begun with Block IE, and the Block II missile provides the Harpoon with a littoral-water anti-ship capability"

    I read this on Wiki, so caveat emptor. But maybe this is the "Over the Horizon' missile that the Navy wants for the LCS?

  2. The idea I suppose is to redirect the missile if another priority target is detected (or evaded another missile.) It's a worthwhile capability, although undoubtedly other upgrades are also being performed. It's also a good thing to run older missiles through the factory for a thorough checkout. As for the redirecting platform, it's supposed to be the job of the shooter, or the E-2. The Navy also seems to want the F-35C to be forward sensor node, so that would be another source (F-35s cannot shoot Harps btw) after the Super Hornet, laying back, lobs off a missile.

    1. Bear in mind the point of the post - that it's highly unlikely that new targeting information worth redirecting the weapon is going to pop up in the 3 minutes or so before the weapon is pretty much committed.

  3. HM Forces are moving very very quickly to fire and forget with Data link option.

    I think, I THINK, although they wont discuss it, this is to do with defeating counter measures.

    with 2 sets of eyes, the missiles and an observer at different places \ angles, we can observe and discriminate the chaff and flares from the ship better.

    When one observer is a much more advanced radar, or a man in the loop. either of which can discriminate counter measures from target better than a missile the hit probability increases massively.

    I think this is why optimal hunting formation for F35 is supposidly 4 F35 in a diamond at least 100nm apart with datalinked weapons.

    You get a better track with a composite image from several different angles.
    Then you KEEP updating the missile all the way in.

  4. I remember when studying fire support that one method of verifying suspected targets covered by clutter is to fire missiles at suspected targets in an area and then to focus the missiles on the targets that missile sensors can confirm. Supposedly this capability is coming to multiple air to ground missiles.
    Still don't understand what a missile sensor will see that better aircraft or ship sensors will not unless you are shooting blindly (which sounds like a good way to violate ROE)

  5. Remember if you think back to why the harpoon was first deployed, the mission was to strike at russian cruise missile subs, which needed to fire at ships from the surface and the air launched torpedoes on the Vikings didnt do 'surface' vessels. Then the option was made to use them from ships as well and back in those days the Soviets didnt have much at sea on the surface and even an intel trawler was very worthwhile hit.

    As indicated above mid course guidance isnt really necessary if you have a good target location when firing, and this is important, have only a single target to consider.
    The interesting part comes when you have a dispersed collection of targets, which one is the harpoon going to lock on? The first one it finds on the outer screen or something important. This happened with exocet in the falklands war when the Atlantic Conveyor was hit, better targets were spoofed away or missed.
    Im thinking in situations in the South China Sea for instance, do you want to target one of many 'militia' fishing vessels that would surround higher value targets or with a later more precise targeting information, ignore these decoys and go for the most important military vessel .

    1. If you have a sensor platform in sufficient position to discriminate and guide a missile to a specific ship in a group of ships, you presumably had that same sufficient information 3 minutes prior when you launched the missile. That's the point of the post. What could have changed in 3 minutes?

      If we try hard enough, could we come up with a scenario in which this capability would be useful? Probably, but it is it really worth the investment, time, and effort for a highly improbably situation? Do we not have plenty of other efforts that are much more useful and likely? That's the question the post asks.

  6. The scenarios I've seen in PR materials have a ship lobbing a missile OTH in the vague direction of the enemy, and a Hornet or similar giving a more precise aimpoint because it actually has sensors on the target. You'd think you could do this with datalink at launch time, but perhaps they're not expecting datalink to be working.

    It seems to me that a capability like this is a hugely tempting technical target. If you can crack the MCU code, you can reliably redirect an enemy missile…

    1. Roger, you've correctly assessed the PR. If we have good enough guidance data at the 3 minute mark, wouldn't we have had it at launch?

      If data linking at launch is not working, how will it be working 3 minutes later for mid-course guidance?

      The scenario that this capability is based on is highly unlikely, it seems to me, hence, the post.

  7. You could launch the missile off-axis and then re-direct it effectively giving it waypoint.


    1. My understanding is that the newer versions of the Harpoon already have the ability to use waypoints in order to fly a dogleg course. This would be standard tactics in combat to make it more difficult for an enemy ship to return fire using a bearing only launch. Otherwise, the enemy ship can respond in kind by shooting his ASCM's back along a reciprocal bearing.

  8. Perhaps the USN view it as a low-cost option to gain operator experience with providing mid-course-updates for SSMs, in preparation for the delivery of LRASMs (at an obscenely high unit cost and absurdly low batch quantities - just wait and see).

    I can't see too many LRASMs being fired off at the PMRF.

    Cheaper to fire off minimally modified Harpoons.

    Or, maybe they want the RGM-84(?) to seem more compelling when it is chosen for the LCS OTH missile.

  9. Boeing is modifying the Harpoon Block II to reduce warhead size to c. 300lbs and increase range to c. 134nmi through a more efficient engine and additional fuel. With the greatly increased range in mind, the midcourse guidance upgrade makes more sense.


    1. CLH, partly yes but no. Yes, the mid-course guidance could make some sense for the longer version, however, the longer range version is the proposed new Harpoon (Block 4, in a sense) and is not in production and is not a Navy weapon. So, no, the mid-course guidance which is part of the Block II+ is not part of a longer range Harpoon and serves no realistic, practical purpose.


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