Donovan Magney

Overview

One fundamental practice during analog missions is the extra-vehicular activities (EVAs). These activities focus on getting analog astronauts to perform various experiments in an open and controlled environment, helping them get accustomed to wearing heavy suits and familiarizing them with their tools. One of the suits used for EVAs at LunAres is known as the PUMA suit, which features a ventilation system for comfortable breathing and a CO2 sensor to measure the carbon dioxide levels inside the helmet.

Modules

Airflow

Problem

During my first EVA, the crew noticed an issue with low airflow into the PUMA suit. While wearing the suit, I observed that I was breathing heavily even when idle, and the temperature inside the helmet would become uncomfortably hot. After the EVA, an inspection of the backpack revealed that the fan was not secured properly, preventing efficient air intake. This also caused the air hose connector on the backpack to move around significantly when trying to attach the air hose.

Final Design

The final design features a two-piece mount. The first component, called the connector, interfaces with the air hose and routes the fan exhaust into it. The second component, known as the funnel, directs air from the relatively small hole on the backpack exterior to the larger hole on the fan. The connector includes a long extrusion under the fan exhaust that allows for a bolt to be installed, securing it to the sides of the backpack. The funnel is a funnel-shaped piece with drilled bolt holes to secure it to both the backpack exterior and the fan. By separating the mounting holes, we were able to use much shorter screws that we had on hand, and the assembly could be removed from the backpack without taking it apart.

Wiring

Problem

While trying to solve the airflow issue, the team found that the internal wiring of the backpack was very difficult to understand, and most of it was unsecured to the backpack itself. This meant that in the process of debugging the airflow problem, we had to spend several hours just trying to learn and understand the current state of the wiring. The situation was made more difficult by an incomplete schematic. Additionally, the messy wiring could come loose due to its own weight, potentially causing a failure if not properly secured.

Final Design

The final design utilizes Velcro to secure large components and wire bundles, while electrical tape is used to electrically isolate the wires. Electrical tape was chosen over heat shrink tubing as it was easier to apply and remove, and could serve as its own label (black for GND, red for VCC). Most individual components and a few important wires were labeled. The length of many wires was also reduced to only what was necessary. Additionally, a USB hub was added to the backpack to power up to four USB devices. Currently, these devices include the LEMs device (life support sensor readout), the helmet sensor, and two LEDs on the front straps of the backpack. Based on a recommendation from a previous crew, the backpack now also has a charging switch. This switch cuts off power to the charging port to prevent accidental shorts during an EVA. The switch should be ON when charging and OFF at all other times.

Helmet sensor

Problem

Wearing a helmet designed to hold in pressure means that CO2 cannot escape. The backpack airflow system is designed to bring in fresh air for the astronaut, so it is important to monitor if that system is functioning correctly and has enough performance to keep the astronaut safe. A previous crew appears to have attempted to add the ability to measure CO2 and temperature inside the helmet but ran into the problem of needing to run a wire inside the helmet to power the sensors. Since the helmet needs to hold pressure, it doesn't have any holes that would easily allow wires to run through without modification.

Final Design

The easiest place to route the wire through was an old air connection (not the one in use for ventilation). This access point had a sort of plug that we were able to take apart and reveal the actual hole in the helmet. We were then able to 3D print a part that would fit into the hole and allow the wire through. For the aesthetics, we also added back the rubber cover from the original plug to our 3D print. The helmet was not damaged at all and is able to be restored to its original condition. We also moved the Raspberry Pi to the exterior of the helmet secured with velcro to improve its internet connection.

Conclusion

The Puma backpack had a few issues that put the analog astronaut inside it at risk, such as the inoperative ventilation system. Even if this system did work, there was a risk of failure during an EVA due to the rushed assembly of the wiring. Tweaks were made to the ventilation mounting mechanism and the wiring cleaned up to mitigate these issues, and a CO2 sensor inside the helmet implemented to monitor the astronauts safety in real time. The new system was tested on an actual EVA and performed flawlessly despite being intentionally shaken and required to continue running for multiple hours.