Space Apps Challenge 2018

Story

An astronaut is planning an expedition on Mars in order to find sources of water for his/her research. They require internal systems to monitor the health of their spacesuit, and externals systems to determine their position, to measure their environment, and to determine clues leading to sources of water.

Description

The challenge is to design a system that will monitor essential parameters for the spacesuit, and notify the astronaut of any anomalies detected. This project is intended to model a system for monitoring gases (CO2, CH4), humidity, and pressure on Mars. The system will enhance the astronaut's spacesuit on Mars, containing both external and internal sensors.

The following parameters are monitored:

• External altitude, temperature, humidity: These parameters give clues to the astronaut as to their position and environment. On Mars, the temperature and humidity are directly related to the time of day. During daytime, the temperature increases, and the humidity decreases. During night, the temperature drops, and the air saturates to the point where the humidity is at 100%. [1]
• Internal CO2: This parameter is used to detect leakage in the astronaut's space suit. The atmosphere of Mars is composed primarily (over 95%) of carbon dioxide. A leakage in the suit would lead a sudden increase in the CO2 PPM inside the suit, which can then cause the external LED to blink red, notifying the user.
• External Methane: Methane gas levels are typically constant on the Martian surface. However, in the event of out-gassing, the levels can increase rapidly. Hence, when the spacesuit comes close to such an area, the increasing levels of methane can be monitored, and the user can know they are reaching an out-gassing area. Out-gassing can be an indication of a possible source of water underneath the surface. [2]

In summary, the system is capable of detecting the following conditions:

• Internal CO2 levels, in order to notify the astronaut in the event of a leakage.
• External pressure, humidity, temperature, and altitude (relative to an average ground level on Mars).
• External methane levels, in order to detect out-gassing for possible sources of water.

Hardware

Block Diagram representation of the device.

Setup

The system is equipped with the following hardware:

1. Teensy 3.6 - This is the controller for the system.

2. CCS811 - This is the internal sensor used to measure CO2 and TVOC.

3. BME680 - This is the external sensor used to measure pressure, temperature, and humidity.

4. MiCS-5524 - This is the external sensor used to detect methane gas.

The sensors are chosen based on availability and budget constraints for this project.

Design Challenges

In order to get accurate parameters on Mars, the sensor algorithm had to be modeled based on parameters of the Martian atmosphere. For example:

• In order to determine altitude, the pressure detected from the external sensor is needed. A NASA model for the surface of Mars is used for the altitude determination [3]:
  
  p = .699 * exp(-0.00009 * h)
  
  Where p is the measured pressure. The formula accounts for the lapse rate for air at altitudes less than 7000 m.
• In order to determine methane levels, a model based on the datasheet of the gas sensor is constructed. From the datasheet of the MiCS-5524, the following model was built to correlate the measured analog voltage and the PPB of methane [4]:
  

Resources:

[1] The Martian humidity is discussed here: https://www.space.com/29857-mars-humidity-alien-li...

[2] Out-gassing, described in wikipedia: https://en.wikipedia.org/wiki/Atmosphere_of_Mars

[3] Altitude model is based on the work here: https://www.grc.nasa.gov/www/k-12/rocket/atmosmrm.html

[4] Datasheet for MiCS-5524: https://cdn-shop.adafruit.com/product-files/3199/M...

Source Code:

Source code can be found here: https://github.com/rahmant3/Marscope