First off, contrary to what I stated in my previous post, today’s post will not discuss one way in which UUV technology is being optimized for the purpose of undersea warfare through the utilization of advanced biomimetics, as I ran out of time to prepare that post and thus will publish it in my next round of posts.
Today I will be sharing something a little bit different…the design of a full body suit that was recently worn by a man who was swallowed whole by a 25 ft. anaconda…on purpose. I’ll decline to comment on the validity of this kind of feat, as that is not what I am here to write about, but will rather focus on what is effectively a pretty interesting case study in engineering design.
Anytime something must be designed to be used by humans, the level of engineering required is almost immediately stepped up [for many reasons, including (but not limited to) the increased importance of safety], and this is no exception. In all product design, engineers must begin by determining the problem statement and the constraints imposed by that statement. Dr. Cynthia Bir (a biomedical engineer), one of the project leads for the suit design, would have begun by looking at the facts: there is a man, who will be ingested by an anaconda, and that man must then come back out of the anaconda without being harmed. As ridiculous as this must sound, it is actually quite reflective of the absurd nature of the design/operational constraints that engineers must often meet. Next, Dr. Bir would have had to conduct literary (or possibly even experimental) research into the aspects of the problem statement (the snake itself, and all aspects of the human-snake interaction to take place) and then determine/look at the consequences associated with this problem statement; that is, what are the specific risks posed to the user in this scenario (in this case: constriction, snake bite, and acid attack from the gastrointestinal acids). Next, she would have started in with generating concepts, selecting a few concepts to further develop, doing some base-line evaluation and analysis of those concepts in order to cut it down to one final design, and then starting in with the actual design/calculations/analysis/testing of her chosen design. I should note that engineering design is never this simple and is actually a very complex process, that generally sees many iterations and a great deal of looping back to earlier steps of the design process.
So, as we stated before, Dr. Bir had already deciphered the situation, conducted relevant research (how a snake attacks its prey, what kind of acids are present in the snake’s stomach, etc.), resolved the situation into the key parameters/constraints associated with the situation (ability to resist snake bite, constriction, and stomach acids), and now would have come up with a few concepts. Undoubtedly, one of the decisions that would have been made early on would revolve around what kind of material system to use in the design: one material for the entire suit or multiple materials used throughout the suit. In this case, it would have been very difficult to use one material for the entire suit, as the application calls for many different material properties (hardness, strength, and fracture toughness for the snake bite, stiffness and compressive strength for the constriction, and resistance to chemical attack for the acids, etc.) and thus it would be far more economical to use multiple materials (each one targeting a few key constraints) on the suit (as opposed to having to develop a whole new material to meet all of the specific needs of the suit). In fact, this is exactly what Dr. Bir and her team did.
The innermost layer of the suit actually served a different purpose: to monitor the vital signs of the man being swallowed (his heart rate, respiration rate, core body temperature, etc.), as if something began to go wrong, they would want to stop the experiment immediately. This layer consisted of a biometric vest that was paired through Bluetooth to the project team’s computers, giving them live updates of all of his vitals (it is interesting to note that these kinds of vests are also used by special operators, astronauts, some athletes during training, and many others).
Next, came a thermal control layer in the way of a vest fitted with a pumped liquid cooling loop heat exchanger which essentially sends cold (colder than the man’s body temperature) water through small tubes that run across his body. The temperature difference between the man’s body and the water in the tubes drives heat transfer out of the man’s body into the tubes, thus cooling the man’s core temperature. This is important in order to make sure that the man does not overheat, because he will be wearing a number of thick layers of various materials and will be inside of the snake’s stomach so that he will be exposed to his own internal heat generation, the snake’s internal heat generation, and all of his insulating layers.
Next comes a chemical suit (not pictured) to provide the chemical resistance that we mentioned earlier. After this, a layer of chain mill (like that worn by Renaissance knights or people who dive with sharks) is added in order to block the snake bite.
On top of this comes a rigid carbon fiber shell that must be made custom to conform to the user’s torso and is used to resist damage to the ribs/chest cavity by constriction of the snake’s muscles. The torso shell was designed with a factor of safety of a little over 3 (meaning that the shell’s strength is over 3 times the stress that it will be subjected to during the event) and was tested by wrapping a thick rope around the shell and pulling the rope with tow trucks at either end.
On top of all of this, the user donned a thick layer of neoprene (think a wetsuit) to keep all of the other layers together and cover any otherwise unprotected parts of his body; this layer was then dusted with pig’s blood in order to attract the snake and ensure that the snake would actually want to ingest the man. Other things (a few of the many other things) that had to be considered in the design of this suit would have included the weight of each component, thickness (to ensure mobility of appendages), range of motion (note the fact that the torso shell is sleeveless), thermal conductivities of all materials (for proper heat transfer calculations), possible interference with the Bluetooth signal, ability to put on/take off the suit, and of course ability to breathe! The ability to breath is vastly secured by a combination of three things: the carbon fiber torso shell, none of the layers being too restrictive, and a sealed face mask (which also serves as eye/face protection from any objects or acids, thus the mask must also be chemical-resistant) with an external air hose (which must also be resistant to chemical infiltration) fed by an air supply from the project crew.
So there you have it, an interesting look at some of the engineering considerations behind one of the strangest things I have ever heard of anyone wanting to do. This just goes to show that the possible applications of the world of science, technology, engineering, and mathematics (STEM) are truly limitless!
Please be sure to check back Thursday for a Presentation post by Andrew and please remember to help us to share our fundraising campaign at GoFundMe.com/TeamUV