The original Tomahawk antiship missile had the same active seeker as Harpoon. It was to be fired at targets up to 1,000 miles away, and find its victim when it got there. At about 60 miles, Harpoon was finding anything but its intended target. We accepted that--during WWIII--we were going to be fighting in more open oceans, lots of destruction would be inevitable, and collateral damage was "to be expected."
That changed after the Cold War. Launching a Harpoon at a pirate mother ship in the crowded shipping lanes off the African Horn, and having it blow up the merchant ships we hoped to save, was clearly not "good policy." More precise targeting has been the technological challenge being worked on ever since. With things like drones "lurking" over horizons, and better sensors in the infrared range, and so on, the targeting problem is now finally being tamed. It then remains to get all this new tech onto working missiles. We have selected Tomahawk due to its maturity and required range as a candidate, and testing of them is happening. Deployment will follow. We will then have a system with a credible chance of hitting its target at extreme range. Things like LRASM are less mature, so need more testing. Once through that, they offer the next generation of these long range weapons.
Most Western navies have faced the identical issue. The more advanced are also now nearly ready to field their solutions.
Meanwhile, the Russians initiated a new approach. Very high speed, at very close range. At such high speeds, they can not generate much range. Close range means not dealing with complicated targeting solutions. High speed means our defenses have little time to respond. Very clever, and very effective when wars are fought at 60 mile Harpoon ranges. When (not if) we open up the spaces to 1,000 mile ranges, we fire before they can get their weapons in range. War being messy, there will always be exceptions to the rules. No realist thinks we will always be far away, and never get hit. But, in general, our strategy offers a solution to the problem.
So, the Russians have come up with the hypersonic glide weapon. Put a high speed "missile" (glider, actually) on a long range ballistic missile. Fire it to vacinity of intended target. Glider detaches and zooms to target at low altitude (where it is harder to detect) at high speeds which give little reaction times. Number one, the Russians now have the long range targeting problem. Their solution is to put the warhead "in the vacinity," but it still needs to fly in the right direction once separated, etc. Number two, we again open distances by extending our sensors farther out (primarily with plentiful numbers of low cost drones) providing earlier detections, and thus longer reaction times.
This cycle has gone on since humans have made war. Thag hit Gronk with club. Gronk create wooden shield. Thag make spear to put pointy end way out in Gronk's face. Gronk make arrow to fly pointy end to Thag before he use spear. Chinese make gunpowder and we blow each other all up. Gunpowder not enough. Americans make nuclear warheads. Now, we REALLY blow each other up!
i would like to congratulate MR PUTIN for the way his "operatives" have denuded the west of any effective long range anti ship missiles! at the same time he and China have a multiple choice of weapons to use that outrange the wests missiles and carrier bourne aircraft!
Type 21, late
4.5 inch gun
4 Exocet missiles
Sea Cat point defense AA
6 ASW torpedo tubes
4 20 mm guns (manual)
All on a small hull
Type 31, per you link
4.5 inch gun
Sea Ceptor point defense AA
Extensive boat launch ability
20 mm Phalanx CIWS
1 helicopter plus UAVs
On a hull nearly twice the size of the earlier vessel.
For its day, the Type 21 was well rounded, and well armed. All sorts of drawings aside (many showing all the potential export options) the above list is all I have ever read that the Type 31 will be armed with in RN service. And this fits the £250 million price cap as well. (That is around the cost of a US LCS, btw.) At present, the RN envisions using these 5 ships in much the same low-end functions as we plan for LCS.
57 mm gun
Hellfire missiles (and now 8x NSM is being added)
RAM/Sea RAM point defense AA
Extensive boat launch abilities
2 30 mm guns
1 helicopter plus UAVs
All on a small hull.
The difference is clearly the ability of a Type 31--by virtue of greater size--to upgrade in future if more money is spent. They can take up to a 5 inch gun, and even apparently strike length VLS. But, not for the £250 million cost cap! Those sorts of systems reside on the over £1 billion Type 26. Unless the British Government spends more, it is doubtful the Type 31 will be armed to the level of a Type 26, which--with a MK 41 strike length VLS--can accommodate very large and capable missiles simply by acquisition or development, whereas the Type 31 will then also need to have the VLS installed too. While likey that Type 31 will see an upgrade to a heavier antiship missile via box launchers once one is available, the Type 26 can similarly be fitted with the Tomahawk antiship variant being developed by the US. And Type 26 can fire much heavier AA missiles, and ASW weapons, which are also under development.
The Type 21 was a product of its times, and I don't think it was too shabby. Meant as an ASW convoy escort, it adapted up to a general purpose warship well enough. The Type 26 and 31 are also both products of their times, and I appreciate both for what they are. One is a high end frigate of some cost, with the features one expects to see as a result. The other is a wise decision to obtain as big/flexible a hull as possible for the low desired price, cheaply obtaining great future potential. The current and foreseeable fit, however, will be on the light side. The ships will be used accordingly as well.
The anti-ship missile launchers on the drawings are much more massive than the LMM - but if the Type 31 only gets LMM and a real anti-ship missile in 2030, the armament would be really weak (at least the anti-ship capability). But it would be still significantly more heavy armed than the frigates of the times of that specialist... And still has a anti-ship capability similar to the Type 26 (close to non)...
It appears that really a lot of western navies have troubles with anti-ship missiles. The German Brandenburg class has their antique MM38 Exocet replaced by Harpoon Block 1C - also close to have to be retired... RBS-15 are in use on board of the corvettes and NSM will be bought, not sure for which class of ships (F126?).