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Okay, finally got a bit of time.

The whole point of the UUV was raised by the question of what ASW is going to look like going forward and in response to the issue of whether our next-generation primary ASW combattant, lets call it C1 for sake of ease, needs to be a son-of-T23 and as capable in all regards.

We've been lucky here having the opfor involved in the reparte in the form of Kev!. He has obliquely confirmed that the higher frequencies, in active search, offer the best chances for detection of a discrete SSK contact in the shallows. Anecdotally our Falklands experience with the HAS.2/5 and their 195 dipping gear predicted that a long way back!.

Problem is that they are short range sets. The Thales USV HF-variant of the FLASH dipping sonar was credited with a range of about 8000yds. The L3 HS200 MF hull sonar perhaps 20,000yds if you have a lucky PWO aboard!. Look up the specs for contempory HWT's like the Russian UGST and decide whether you want to be just getting a start on a track at 20k yards!.

The obvious solution to the problem was to move the sensors offboard as far as practicable...enter SOSUS, SURTASS, Sonobuoys and pinger choppers. Of those, applicable to the littoral you can scrub the first two. SURTASS-LFA is a seperate case, but, no matter how capable it ends up being it wont offer full theatre coverage. The US ADS network was an attempt to get a mongrel-halfbreed SOSUS/Sonobuoy network fielded to cover assembly areas, but, that proved unworkable. So the only actual operational systems left open to prosecute submarines in the littorals, at safe(ish) standoff, are choppers.

Simple equation then - C1 must embark as many ASW choppers as possible short of being a CVS itself. My view on this is that a stretched T45, prob up to about 8500-9000tons, able to take up to 3 Merlins as a ships flight would be cost-effective, deliverable, supportable and damned useful. Problem is, naturally, that ASW choppers are viciously expensive especially when you get to the Merlin end of the league table. They also demand wince-inspiring levels of local resource supporting their sorties and, in the main, score fairly low on endurance terms.

So, whilst choppers are a principle ASW weapons system and will be ever more, they are deeply flawed. Whilst its patrolling the SSK has a problem. If there isnt a replacement in the air when the patrolling chopper has to call time and go back for refuel/maintenance/crew rest then the SSK has its window of opportunity....thankyou and goodnight. The money spent on the chopper in the first place was wasted because the sub is through anyway.

This problem being exacerbated in proportion with the length of the ASW perimeter that the tactical environment presents you. If as in the Falklands campaign a beachead can be selected in a sound or natural harbour the ASW job diminishes measurable and it is up to the on scene commander to attempt to create that situation. If the geography doesnt allow that the options are limited. Throwing an ASW zone out 50nm from your assembly area, assuming an 180 degree arc to seaward of the landing forces, gives an ASW perimeter of 157nm. At 50nm range, using MH-60R as representative, a pinger has an endurance of approx 1.5hrs. To cover that perimeter with choppers you would need 12-15 aircraft simultaneously airborne. With sortie endurances of 1.5hrs 3 airframes would be required to keep one on station so, just to maintain the perimeter you would be looking at 36-45 airframes plus additionals for attrition reserve.

Obviously a non-starter. You really would need C1 to be a CVS and for another buy of ASW choppers to achieve that!.

Some means is needed to deny avenues of approach to an SSK and to cut down the perimeter needed to be patrolled by the choppers. In many ways similar to the land battefield where minefields were used to channel enemy forces into fire-sacks. In the naval environment mines can create as many problems as solutions and the ADS, offering mine-like presence, isnt going to happen so an alternate solution is required.Enter, after 6 paragraphs, the USV/UUV solution.

The platform required must offer all-weather persistence in the battlespace. It must offer the kind of endurance to undertake sustained entry denial 'barrier' operations and it must offer the sensor capability to detect a discrete SSK in high ambient noise/poor accoustic conditions. It doesnt need weapons capability. I've long been of the opinion that, in ASW, divorcing the sensor and shooter platforms is a obvious beneficial step. Once detected and identified a submarine, particularly an SSK, isnt running far or fast if its trying to stay discrete. Keep the sensor platform on the target and it doesnt matter if the torpedoes dont arrive for half an hour with a second chopper/UAV or at the tip of an ASROC.

So, now the scene is set and the rationale detailed we come to the technology. In the C1 thread we've discussed power densities, propulsion technology, sensor packages, buoyancy, communications and processing power. Kev has stated a belief that to put all those factors together in an operational UUV creates a vehicle of at least 20tons. I am using, as a template, the Japanese R-One UUV. Details of this platform at:

http://underwater.iis.u-tokyo.ac.jp/robot/r1/r1-chp2-e.html

Essentially, as the Japanese admit in their own research, the power density of the Closed Cycle Diesel (CCDE) is less than can be achieved with batteries. Rolls Royce and Salf both advertise battery packs in the 20-50kw/h range - against the R-One CCDE at 60kw/h. Rolls Royce provide the most detail for their Zebra technology batteries and list a 22kw/h battery pack capable of sustained output, at that rate, over 20hrs from a 195kg module. 6 such modules producing double the R-Ones power budget on a much smaller and lighter installation than the CCDE. It is my contention that a vehicle of similar dimensions to R-One could be developed to incorporate a modified chopper dipping array based on current technology.