Jet pig, Yellow pig: spotting and identifying the various autonomous vessels in Plymouth Sound

By The Captain, maritime correspondent to The Beagle

The University of Plymouth runs an Unmanned Surface Vehicle (USV) programme from Coxside, with objectives of teaching and carrying out research into USVs.  The School of Biological and Marine Sciences is also involved in delivering accredited courses, training and data acquisition for commercial clients. 

You may spot the following USVs out on the Sound – from the smallest upwards:

Jet Pig was designed and built by the university's marine station at Coxside.  She is 1.5 m long and was built to operate in energetic surf.  She is self-righting and can be used to survey beaches both before and after major storms, including tsunami.  Jet Pig’s top speed is 12 knots and she has an endurance of 90 minutes at five knots. 

The Yellow Pig – a 2.3m inflatable (just like a yacht’s tender) built about five years ago for £1500.  She can run for about six hours at three knots and is the university's most frequently used USV.  Yellow Pig can be transported to site in a 6m RIB (Rigid Inflatable Boat) and is used for tasks such as seagrass and hydrographic surveys, for which she is fitted with a multi-beam echo sounder.  She is a very stable and capable platform and has been used regularly in repeat surveys.   

Red Pig (slightly bigger than her yellow sister at 2.5m) is also one knot faster, with an on-task endurance of six hours at four knots.  She has much the same role as Yellow Pig.  Her software package (control and hydrographic acquisition) was written in-house by the university survey team, and she can be operated beyond line-of-sight (but isn’t).

Otter is a Marine Robotics USV that belongs to the Royal Navy.  She is effectively a commercial version of Red and Yellow Pigs designed for inshore and estuary survey work.  She is primarily used to train hydrographers. 

Cetus is a 4.5 m diesel driven aluminium hulled USV with a top speed of seven knots and a maximum endurance of 48 hours.  She was manufactured in Portchester by L3 Harris. In the Sound, the university's Cetus has a moonpool in the middle part of her hull (under the Starlink Aerial) and the aft ‘cabin’ hinges at the front edge to open up another space for power systems. 

There is also a forward bay for hydrographic/oceanographic sensors to be fitted.  Cetus has an extensive communications suite, including Starlink, 4G, Wi-Fi and military-grade radio datalinks.

Finally, Bauza – a 4.75m long L3 Harris ASView fitted C-Enduro class USV, also built in Portchester, belonging to the RN.  Her propulsion is a diesel engine charging a DC battery, with two 3 kW electric drives.  With a 1 kW solar panel and a 300 W wind turbine, this gives her up to 6 weeks' endurance. 

During the Repmus 2024 large-scale annual NATO maritime innovation exercise held off the coast of Portugal, Bauza was controlled from Coxside in Plymouth over Starlink.  She was the only one of the USVs involved to have been controlled remotely.  Repmus 2026 will feature more than 300 USVs. Airborne drones may get most of the attention because of the war in Ukraine, but the marine area is certainly not being neglected - and Plymouth is the UK’s National Centre for Marine Autonomy!