After speaking to Dawn Kernagis and Kirk Krack as part of our DEEP interview series, we chat to Rick Goddard, Product Director of the Sentinels, and Harry Thompson, Advanced Manufacturing Lead of the WAAM Robots. Both currently work on creating the Sentinels, DEEP’s elaborate underwater habitats that will sit on the ocean floor. At DEEP’s headquarters in Bristol, they show our editor the impressive line-up of 3D metal printing robots that they will use to manufacture underwater habitats, as well as a life-size 1:1 ratio mock-up structure of their Sentinel habitat.

Oceanographic: Rick, this wooden mock-up structure is really impressive to see first-hand. Why is the Sentinel mock-up here? What is it currently used for? 

Rick Goddard: “We use a ‘design thinking’ approach, combining Industrial Design and Human Factors alongside our Mechanical Engineering early in our design process. The mock-up is a great example of how we can quickly step out of early CAD and analysis into real physical models for human factors testing from 5^th percentile to 95^th percentile and iterate quickly through design development, this applies to everything from the overall positioning of bulkheads to the positioning of the taps in a bathroom and how divers handle umbilicals in an enclosed space. We also use the mockup for development of our operational processes both standard and emergency; our divers work through processes here and we update both the design and processes in tandem.”

Oceanographic: How is the Sentinel different than other underwater habitats?

Rick Goddard: “Sentinel‘s design tenets differentiate us immediately from habitats that have existed before. Most notably habitability, the sheer size of Sentinel is an order of magnitude larger than previous underwater habitats. The internal volume of a single span is ~450 m³ meaning we can place an emphasis on comfort and reconfigurability as well as safety. We need to make our habitats places where scientists and researchers can spend time and carry out their work and this drives the habitat spatially.

By 3d printing our hull, we can use generative design to create efficient structures allowing us to make sure Sentinel is designed for stress in effective ways without the need for big heavy forgings which are spatially inefficient. Because we’re able to print these sections, in areas where there’s a lot of stress on the structure, we can put more material, and in those places where there isn’t much stress, we can use thinner printed pieces. Visually this creates structures which are not just efficient but also beautiful in form, you see this best in the main hull. Habitat occupants will always see this structure and will remain connected not just to their external environment, enabled by our huge 2m viewports, but also to the engineering wonder of being in one of the world’s largest additively manufactured structures.”

Oceanographic: What is the habitat made out of exactly? 

Rick Goddard: “It’s made from 3D-printed mild steel, supplemented in key areas with Inconel, which is a nickel-chromium-based superalloy. It is very corrosion resistant, very strong material that will be printed on top of the steel in areas where we have higher risks of corrosion or where we have finishing faces. This is crucial in delivering our deployed design life of 20 years which in turn is critical to maximising our reusability and getting the most from our components in terms of carbon efficiency.”

Oceanographic: On the interior, how many rooms will there be?

Rick Goddard: “In this configuration there are six cabins, all approximately the same size (the habitat commander and second in command spaces are slightly larger). Every living space will have a section of a large aperture within it, giving a connection to the occupant’s surroundings, at shallow depths they’ll be able to see the surface and at deeper depths, the external lights will give visibility of the surrounding ecosystem. The rooms will also be acoustically insulated to allow privacy and a good night’s sleep, essential for maximising the performance of the team.”

Oceanographic: How do you make sure everything is where it needs to be in the end?

Rick Goddard: “We test everything thoroughly first in the Sentinel mock-up, here at DEEP, we’re spoiled by the fact that we’ve got our first end-users in the same building as our engineers and designers and we use this extensively to ensure that each space in the Sentinel System has been experienced by the range of people who will use it and their input gathered and actioned. This isn’t just divers, it’s also our scientists who are indicative of the future researchers we intend to host in the Sentinel System. Most visitors to DEEP enter the mock-up and when they do we gather all feedback to ensure we’re creating a multi-role space which works for the large range of potential users. We are also in the process of assembling our wet-trainer at our Campus facility which will be another full-scale structure but this time made from aluminium and floating on our incredible 80m deep test site. Alongside similar activities as those conducted in the mockup, we’ll also be able to dive out of this structure to practice our diving procedures in a direct analogue with the final deployed Sentinel, this will help confirm placement and format of dive equipment in a very real simulated environment.”

Oceanographic: Thanks, Rick. Harry, these robot cells look absolutely amazing. How many printers do you have here?

Harry Thompson: “We currently have three robots in single cells and six are being further developed in Rotterdam. In total we have 19 robot arms for printing metal. They’ll all eventually be put here in this workshop. At this stage, we’re doing pre-production testing in terms of the material processes. After that, we’ll test how to best ship the parts, and the software will have to go into the trial period. I imagine, if you’d come back in a year, these printing robots would have taken over the entire place!”

Oceanographic: How will the printing process work exactly? 

Harry Thompson: “At the moment, the printers stand in their own individual cells, but the idea is that the robots will work together in groups of 6 to print the large Sentinel components. What is really interesting is how we’re automating the printing of the Inconel onto the steel directly which is conventionally done by hand.”

Oceanographic: Once all pieces are printed and assembled, where will the first Sentinel be deployed? How do you see the habitat’s future?

Rick Goddard: “The first Sentinel we deploy will be deployed at our Campus facility. We’ll be putting it through the final factory acceptance tests on the shoreside there before deploying it for harbour trials in controlled conditions. Following these harbour acceptance tests we’ll then demobilise the habitat and transport it to a customer site for final sea acceptance and customer acceptance testing. We’ve created the habitat with a strong emphasis on reconfigurability, it’s one of our design tenets. We don’t want to create a habitat which is individually mission tailored but can’t then be reconfigured for future deployments, each Sentinel component is an enduring asset.

I like to consider the next 20 years of humankinds adoption of subsea habitats from the perspective of a habitat pressure hull: deployed for sea acceptance testing, then used for a reef observation project at 40m for 5 years before being reconfigured and moved with minimal disruption to be used for DNA profiling for another 7 years at 60m, then reconfigured at depth at the same site to conduct marine archaeology and so on and so forth. A Sentinel System is an incredible piece of equipment and to gain the most from it, it needs to be able to adapt and change with developments in technology, diving approaches, missions and humankinds understanding of the Oceans. We’ve spent the last 70,000 engineering hours as a team trying to achieve this goal, it’s a rewarding and exciting challenge.”

Get a sneak preview of the DEEP Campus near Bristol: