POSTERRA: HANDHELD MECHANISM FOR UNDERWATER CLEAN-UP DIVES
SENIOR CAPSTONE PROJECT - FALL 2020 AND SPRING 2021
OVERVIEW
Posterra was a year-long capstone project sponsored by the MEAM department that I worked on with Chris Fox, Hanna Kim, Lucy Stinn, Rakesh Ravi, and Seth Rogers. The goal of our project was to develop a handheld underwater device to assist scuba divers participating in clean-up dives. It accomplishes this goal by allowing divers to safely remove solid waste at depths up to 10 meters within the sublittoral zone of the ocean, while also providing an effective storage solution for the collected waste.
The project won the Judges' Choice award at the culminating department-wide competition and I was responsible for stakeholder research, product development, and pump and hose research and testing.
BACKGROUND
Much of the first semester for Senior Design is dedicated to finding an impactful and rigorous project which means lots of brainstorming, reaching out to stakeholders, and downselecting. Our team knew we were passionate about sustainability and during the process of figuring out what we would work on, we had brainstormed ideas for compact recycling machines, a device that could crochet yarn from plastic bags, and autonomous street sweepers (to name a few).
While we were all used to being given a problem and solving it with the technical knowledge we had gained during our time at Penn, this was the first time we were really tasked with understanding how our work could impact real people and how to appropriately scope our work for our time. This was a really tough but rewarding experience and after talking to stakeholders from scuba divers to people who worked at environmental non-profits to water management authority, we honed in on the lack of efforts to cleanup solid waste at the bottom of the ocean and decided on Posterra, a device that would increase the efficiency of clean-up dives for scuba divers.
DEVELOPMENT
Our design for our device featured three main subsystems that we focused on: the aquisition subsystem (the pump that would increase rate of pickup), the extension subsystem (the tubing that would provide further reach for the diver), and the encasement subsystem (the container that would allow the diver to carry a larger amount of trash for a given dive).
For our aquisition subsystem, we decided to use a pump and venturi to drive flow through our system. With our weight and space constraints, we decided to use a low voltage (less than 60V) pump and for our use underwater, decided to use a bilge pump which is traditionally used for aquatic vehicles. Since the pump couldn't safely intake trash and other particulates, we needed to design a venturi junction which would utilize the flow velocity from the pump to induce a suction flow through our channel that connected our extension subsytem to the encasement subsystem. We ended up testing two different pumps and many many venturi designs to validate our numbers for fluid flow found from COMSOL.
For our extension subsystem, we decided on a flexible hose to maximize usability and performed flow testing to determine an optimal length of 3 feet 7 inches. For our encasement subsystem, we designed a container with an aluminum base plate, to which all other components are rigidly connected, as well as a tapered enclosure constructed of aluminum extruded mesh panels. These were designed to minimize the additional effort that a diver must exert while using Posterra while maximizing the amount of trash that it could hold.
For more technical detail, you can read our final report below: