Japanese Large Diameter Unmanned Underwater Vehicle (LDUUV) Developments

Comments by Anonymous, of November 24 and 25, 2018, shed a useful spotlight on differing national requirements for Large Diameter (or Displacement) Unmanned Undersea Vehicles (LDUUVs). 

For example the size, speed and sensors of a UUV are dictated by a country’s undersea patrol areas. A UUV should also be of a size to respond to unforeseen future duties.

[Pete Comments: Japan may deploy its future LDUUVs in the East China Sea, Sea of Japan or the Russian SSBN bastion near the Kamchatka Peninsula. Meanwhile the US may also use much larger Extra Large UUVs (XLUUVs), with much longer 6,000+nautical mile (nm) range, to tow sonar arrays on mid Pacific, Atlantic and Indian Ocean tracks.]

Timeline of Japanese UUV Development

In 2006, Mitsubishi Heavy Industries (MHI) built a prototype UUV calling it “Marine Challenger 150” to demonstrate sensor and navigation technology. MHI adopted Lithium-ion Batteries (LIBs) as energy sources and studied other Fuel cell options. 

See photos of the yellow colored “Marine Challenger 150” on pages 12 and 15 of this Japanese language MHI document https://www.mhi.co.jp/technology/review/pdf/484/484012.pdf. Marine Challenger 150 looks like a lightweight torpedo and may weigh “150”kg(?).

Marine Challenger 150 looks much like the lightweight torpedo sized REMUS 600 AUV. See Submarine Matters' 2015 article about USS South Dakota (SSN-790) launching and recovering a REMUS 600 AUV - reportedly the first time for a USN sub.

 Also note the larger REMUS 6000 won a Japanese civilian agency order in November 2018.

In 2014, the Japanese Ministry of Finance (MoF) started three stage development of UUV (total budget was US$27 million: 

i)  first research trial (manufacture of LDUUV), 2014-2016), 

ii) second research trial (development of fuel cell, 2015-2017), and 

iii) third research trial (2018-2020). See Japanese Ministry of Defense (MoD) 

http://www.mod.go.jp/j/approach/others/service/kanshi_koritsu/h29/pdf/h29_gaiyo_open04.pdf

Also in 2014, the US Navy requested Japanese joint research on the development of UUVs.

In 2017, Council of External Adviser [to the MoD?] recommended amendments to the UUV plan, and the Japanese MoD accepted the recommendations.

Current Japanese Activity

In December 2018, the Japanese Cabinet is going to approve the development of a 10m long large LDUUV  with funding to be US$37million for the years 2019-2024. [Pete Comment: $37 million is actually quite low. Costs may be minimized by previous Japanese and US development of UUVs over the last 12+ years.] 

For the LDUUV development, the MoD will conduct demonstration experiments to detect sound waves in a large water tank at a naval facility in Iwakuni, in Yamaguchi Prefecture. This may be the same tank that the MoD’s Acquistion Technology & Logistics Agency (ATLA) is going to build - dimensions 35m long, 30m wide, 11m deep. The test facility will begin operations in fiscal 2021 at the earliest, although the timing for the restart of LDUUV development is not yet known.

A very informative Japanese language Sputnik article of November 20, 2018 (once translated) explains that one of the uses of this LDUUV will be to monitor Japanese territorial waters over the Senkaku islands in the East China Sea. Ownership of the Senkakus and surrounding territorial waters is also disputed by China and Taiwan. Under the seabed in the area may be usable oil and gas reserves.

A chronic shortage of [the Japanese] Self-Defense Forces personnel has also contributed to the MoD's view that developing LDUUVs is necessary.

In a further comment of November 29, 2018 Anonymous has pointed to an:

"Abstract of a study on long-term operation of UUV technologies by a Japanese MoD 27th Expert Panel on Policy Assessment held August 16, 2018. [Pete further translating]. The Abstract concerns:

The trial production of replaceable modules for UUVs will be conducted to develop new capabilities such as warning, surveillance and marine observation. Trial production and testing/evaluation of UUVs will be conducted in the 2019-2022 and in 2022-2024 periods, respectively. Total cost is US$53 million.

By cooperation with other domestic institutions such as JAMSTEC, studies and tests will be conducted on:
-  effective utilization of marine observation technologies
-  maximum utilization of test facilities, 
-  reduction of reseach risk, and 
-  on cost and development periods [budgeting and scheduling].

In the case of a UUVs embarking on a 5 days basic mission, an extension of the mission to 15 days will be attempted by adding a battery module or modules. 

So develoment of basic technologies for battery and other modularization will be established.

Acoustic, salt concentration (salinity) and temperature sensors for UUVs will be developed. The impact of addional modules on UUV movement will be studied. This is a preliminary development study to overcome technical challenges rather than developing operational UUVs.

PETE COMMENTS

A LDUUV 10 meters long may limit range to around 1,000nm. The LDUUV might be too small and lack power to pull a towed sonar array. Instead the Japanese LDUUV may have sonars on its hull of the LDUUV to detect Chinese, Taiwanese etc ships, patrol boats and submarines.

Communicating and full processing of the sonar data collected may depend on moving closer to the surface, maybe using a line and communications buoy, working to satellite. The satellite then downlinks messages to Japanese naval earth stations, naval vessels and aircraft. Possibly seabed line arrays may help the LDUUV communicate. Side scan sonars may help find Chinese seabed arrays and bottom-rising mines.

Full data the LDUUV collects may be on its computer hard-disk. Meaning it needs to return to its Japanese naval base (Japanese and US at Okinawa, Sasebo and Yokosuka?) to securely upload all the sensor records and have then process the data using Japanese (and others) mainframe computers.