The Effect of the Environment on Engineering

General Discussion

Astronauts think they need to leave the earth to find themselves in a different world. Most don't realize that there has been less research done about ecosystems and dynamics in deep water than on the moon and some planets. In the Atlantis II Project, distance from the shore is huge. Looking at the conditions there, one feels much farther away from surface conditions than 430 kilometers.

Under the crushing weight of 3000 meters of water, there is a pressure 200 times that on the surface. A favorite experiment of many deep sea explorers is to bring a styrofoam cup outside the submersible. As the vehicle goes deeper into higher pressure, the cup shrinks to a fraction of its original size - more fit for a doll than a human.

One of the things that makes the life there so facinating is it's survival independent of light. People are not used to this, however, and it becomes a physcial and phycological health concern. Additionally there is the tremendous heat of the smoker plumes and their unleashing of sometime corrosive and other times valuable chemicals.

Designing vehicles and thinking about the day to day habits of the personnel living in the habitat must take all of these aspects of the vents (the distance, pressure, light, heat, and the chemicals) into consideration.

The Habitat

The design of the habitat began with a simple sphere since it is the most stable geometric design at high pressures. We realized it would be inconceivable to have just one large sphere so we planned to connect 5 or six spheres. We then arranged the spheres into a spherical arrangement. By simplifying that design we created a torus. Finally, we added two docking spheres.

So, for a depth of 3000 meters and an internal diameter of 6 meters with a 50% safety margin, the walls will need to be about 36 centimeters thick. More details about the Habitat

Health and Safety

Living at the bottom of the ocean brings up many unusual problems for the people on board Atlantis 2. In our daily lives on the surface, there are many things that keep us healthy that we take for granted. These missing factors in our lives are very important to the crew's continued mental and physical health. Such things as the vitamins produced from the energy of the sun or the air pressure that is not so great as to collapse our bodies into tiny globs of protein and water. In addition, we have to take into account the psychological effects of living on the bottom of the ocean, a place that most would agree is a depressing and oppressive place not lacking in danger.

The Main Health concerns from living underwater are:
- Lack of Light causes a vitamin deficiency which is solved by taking vitamin pills.
- Slightly imbalanced pressure causes sickness, so the station has to be kept at exactly 1 atmosphere.
- Living under water may cause depression in the crew members, so they are being put through a psychological test before going down and will be rotated regularly.
More details about Health and Safety

The Transport Vehicle

The environment's impact on the design of the transport vehicle, LEEAMITe, cannot be overstated. Because LEEAMITe was designed to carry as large a payload as possible, the passenger hull diameter is larger than conventional submersibles. Therefore it was extremely important to find the lightest material possible to construct the hull with that could still withstand the enourmous pressure at 3,000 meters below the ocean surface. Also, since there is limited space within the hull, many of the ship components had to be designed to function in ambient pressure. More details about Transport

The Manned Vehicle

Designing a manned submersible would not be a hard problem if it weren't for the harsh environment it has to withstand. The most challenging problem was dealing with the high water pressure. The inside of the sub must be kept at atmospheric pressure for the people to survive, so there is a huge pressure difference between the outside and the inside of the sub. To counteract this we had to make a pressure hull with titanium that was 10cm thick. It is shaped like four spheres connected so it looks like a caterpillar. We used spheres because they are the strongest shape. Another concern of ours was the cold. The water is 2 degrees Celsius at the habitat's depth, so we had to put heaters on the sub to keep the pilots warm. The vents get very hot, but we don't need to deal with that problem because the unmanned submersibles will do all the work in the hot temperatures. The water around the vents is also very corrosive, but they will not hurt our titanium pressure hull. After fulfilling all these constraints, the manned submersible was a lot harder to design than it would first appear. More details about The Manned Vehicle

Tug ROV

ROV's are distinguished by their tether, which traditionally gives the vessel access to (almost) infinite power and with fiber optics allows communication with people. In thinking about this advantageous tether, one finds that running a cable all the way to the habitat where the scientist labs and living quarters are is extremely difficult. It is important that Tug is able to explore vents within a few kilometer radius from the habitat, but having such a long cable creates many complications. First, currents make it difficult to control the cable and keep it in place. It is also important that the cable not drag along the seafloor and damage the life and geology the scientists are there to study. Further, a cable that is a few miles long requires a vehicle with huge propusion capabilities because it takes so much power to drag its entire mass. Ultimately, one realizes the utility of bringing the scientists with us - attach Tug's cable to the Manned Vehicle! More details about Tug

Drillette ROV

The tethering for Drillette had the same problems as with Tug, but Drilling requires much more power than tug. That creates complications, because the manned vehicle cannot carry such huge battery resources, hence, a cable from the habitat is mandatory. To solve that complicated problem this is the Distant Drilling Station to save the day.

Besides a cable, the logistics of designing a drill to get a 10 meter deep sample that the scientists want are almost insurmountable. The vehicles do not have the power nor leverage to attain such samples by common means. The most promising idea are ten 1m segment drill cores which the ROV pieces together as it drills meter by meter. This would save on the major problem of having a 10m rod extending from the ROV and causing it to be more inefficient in terms of energy use and mobility. More details about Drillette

Three Sisters AUVs

Some of the characteristics that distinguish the The Three Sisters from standard ROVs are precisely because of the vent environment and the nature of the Atlantis II project. Pressure at that depth is much higher, and the structure must be resilient. Concerns about melting and corrosion affected the choice of hull material. They'll leave most of the exploration really close to the smokers at the highest temperatures to Superman. Safety and Emergency measures evolved expressly for this environment. Namely, when the AUVs malfunction, the safety mechanism is for the vehicle to sink, because all operations are taken from the bottom. In all other AUV missions, the default is to float because then the ship can find the broken vehicle. They are also equipted with collision detectors to navigate around dangers. More details about The Three Sisters

Superman AUV

Superman acquires data from extreme conditions and especially unexpected events. He has special equiptment to keep him safe in such a risky environment. As the temperature of th water surounding vents decreases rapidly with increasing distance from the heat source, Superman has an extension at its front that measures extreme temperatures and pH while keeping the vehicle at a safe distance. Because the hydrothermal vent fields are unpredictable territory, the auv has myriad ssensors on its exoskeleton that detect extreme temperatures, or salinites, and can direct the auv to a safer environment if it finds itself in hazaradous conditions, that would damage its exoskeleton. Superman uses a revoltutionary form of propulsion provided by Nektors (developed by Nekton research companny) see Mobility. These nektors give the auv increased mobility over thruster operated vehicles, and allow it to turn on a dime. This high degree of maneuvrability is desirable given that the auv will have to negotiate its way through hazardous conditions. More details about Superman

The Communication Cable

The main communications cable avoids the vent system entirely, and as such was only mildly effected by its evironment. Running cables on the ocean floor is not a new technology. Communication between vehicles was another puzzle entirely.

Acoustic modems cannot operate at temperatures higher than 45 degrees Celsius. Even though the temperature in the vent could be as high as 300 degrees, we do not know whether the temperature would ever be so hot near the modems that are placed on top of the vehicles. The large amount of dust particles in the water around the smokers may also cut off the communication completely.

One solution would be to just cease the communication. However, the ROVs do not work without human controllers. To prevent losing the ROVs when unconnected, they can be programmed to either go up or go backwards, tracing their recent trajectory. Then the habitat can resume control after the vehicle regains communication.

The solution ultimately adopted for cases like this, however, would be to tether the ROV to the manned vehicle (Tug) or connect the ROV to a cable running back to the habitat (Distant Docking Station).

If the water temperature gets higher than 75 degrees then there would be risk for breaking the modems. However, since the vehicles are unlikely to stay in that kind of temperature for long, there shouldn't be a problem. Otherwise, we could either implement a heat resistant casing around the modem that could open and close (costing the vehicle some mobility), or simply use the tether method, making sure that the vehicle doing the work does not have a modem equipped at all. More details about Communication

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