NASA Suborbital Flight Communication and Fire Box

=Problem Definition= This project continues the work by the previous University of Idaho capstone teams who have partnered with NASA Ames Research Center on developing a communications system for a Tube Deployed Re-entry vehicle (TDRV). Previous teams have done a variety of groundwork such as building a guided parafoil system that can move in order to reach a pre-determined GPS location during its descent. Other work, accomplished between two of the previous capstone teams includes creating a carrier module capable of controlling and housing the Iridium 9523 modem in order to help integrate into future returning cube satellites. Lastly, a previous team developed the initial codebase for creating communication over the Iridium network utilizing the Iridium 9523 via a dial-up connection. They also attempted to implement a remote server to receive the data.

Our team is building off of these previous groups and creating a fully functional communication system through an Iridium 9523 connected to a carrier module that is powered by Canon BP-955 batteries in a fireproof containment unit. The end product will be a cheap, reliable, and physically safe system capable of real-time data communication with a returning satellite.

The project can be broken down into 3 main components:  The software necessary to provide communication through the Iridium network. The carrier module re-design necessary to host the Iridium-9523 module. The battery box to store the Lithium-ion batteries necessary to power the system. 

=Deliverables=   Software:   Develop software packages and libraries for a Microcontroller Unit (MCU) necessary to establish a live connection over the Iridium Network. Develop a server capable of receiving transmitted information from the Iridium modem and display to a command line interface. </ul>  Carrier Module: </li>  Fully functional Iridium Carrier Module confined to the PC-104 form factor.</li>  Report on the effect of vacuum and orbit temperatures on the functionality of various types of capacitors and resistors, and the performance differences between typical and high-performance resistors. </li> </ul>  Battery Box: </li>  Design a lightweight “firebox” capable of containing a fire as a result of thermal runaway caused by batteries used to power the reentry module.</li> </ul> </ul>

=Specifications= The requirements as outlined by our client are shown below.  </ul>

=Project Learning=

Software:
 The software subteam has spent a considerable amount of time researching details of the Iridium network as well as how to interact between the Iridium-9523 modem and the carrier module.</li> Primarily, the first semester of our project revolved around properly powering on the carrier module, testing the majority of communication ports and functionality, and ultimately working with the Electrical Engineers to fix all hardware issues holding us back from successfully interacting with the modem and the Iridium network.</li> Once the board was fixed and tested, the software subteam has since then focused on reading Iridium-9523 developer guides, NAL-Research communication documentation, and AT reference guides to initially test the carrier module and Iridium modem possibilities with SBD as well as dial-up communication.</li>

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Carrier Module:
 The carrier module subteam is re-designing a carrier module that was created by a previous senior design team so much of the project learning for this section includes viewing and studying previously created schematics created in EAGLE.</li> Experience with this software is limited among team members so the early struggle on this project includes learning the software and how to make it usable for future re-design.</li> </ul>

Battery Containment Unit:
As outlined in the design specifications, the battery insulation box must withstand the mechanical and thermal shock of an explosion resulting from thermal runaway of Canon BP-955 batteries. Since thermal runaway produces hydrogen gas at a temperature exceeding 500oC and flames we must design a ventilation system that will vent the hot gasses while containing the flames. A potential material to fulfill these requirements are open-cell metal foams. Metal foams are metals with built-in pores, where 25% of the volume is occupied by air. Several of the chemical and physical properties are left unaffected. Namely Thermal/electrical conductivity, melting point, corrosion resistance, and reactivity. However, The addition of porosity creates a larger surface area. The major effect we would see is the increase in heat absorbed during contact. The large surface area makes metal sponges great heat sinks where energy is transferred energy away from the batteries in the event of thermal runaway. The absorption of energy is effective enough to make metal foams an effective material to quench flames. Since the box is designed to contain four batteries and prevent thermal runaway we must thermally isolate each battery. To do this and maintain within the weight and size constraints an aerogel or aerogel like material is needed. Aerogels are ultralight porous ceramic materials that are typically 98% air. The high distribution of the nano-sized pores inside the Aerogel creates excellent thermal and electrical insulation. However, the silica skeleton is incredibly brittle and the quantity of the pores limit airflow. Aerogel insulation blankets are produced by submerging a polymer, typically polyethylene terephthalate (PET), felt with silica gel before creating the aerogel. The polymer-stabilized aerogel insulation blankets are flexible with an operating temperature of 350oC and a density of 0.15g/cm3. High-temperature insulation blankets are produced by stabilizing the aerogel with fiberglass instead of PET. Pyrogel XT-e, is an example of a high-temperature aerogel insulation blanket. It has a density of 0.2g/cm3 and an operating temperature of 650oC. Initial learning consisted of reaching out to Mechanical and Material Science Engineering professors, listing possible materials, conducting a literature review, then narrowing down the selection so a design can be constructed.

=Final Design=  <li> Software: </li> <ul> <li>General Details: <ul> <li>Power up carrier board - Consists of code running on the MCU. It will set pins on the carrier module to provide power to the Iridium-9523. <li>Serial communication over RS-232 - Can utilize an external raspberry pi to manually read/write from the Iridium modem to easily test AT commands and develop our code. <li>SBD transmission - SBD packets can be sent via AT commands over the Iridium network and arrive in an email inbox. <li>Establish dial-up connection - The Iridium Gateway number allows for data connections and acts as an Internet Service Provider (ISP). <li>The final codebase will transition control from our Raspberry Pi setup to the MCU on the carrier module instead. <li>Final code library - The library will contain classes and methods for sending and receiving SBD packets as well as establish and maintain a dial-up connection automatically. <li>TCP/IP stack - We will develop and implement a lightweight TCP/IP stack to utilize the network connection and stream data to a ground server. <li>Server - The server will act as a listener with a provided port and IP address to record all incoming TCP packets sent from our Iridium modem. </ul> <li>UML Class Diagram: <li>UML Activity Diagram: </ul> <li> Carrier Module: </li> <ul> <li>General Details: <ul> <li>Component Testboard: <ul> <li>The design is finalized, ordered, and assembled. <li>It has been shipped for testing and we are waiting to see how the components performed under near space conditions to ensure a final re-design uses components compatible with these conditions. </ul> <li>The new flight ready carrier module with be a 4-layer board (2 signal planes, power, and GND). <li>Iridium modem will need completely uninterrupted ground plane beneath it. </ul> <li>The re-designed carrier board will follow the block diagram seen below: <li>The schematic for the new boost converter can be seen below: <li>The re-design will conform to the 104 form factor and appear like the diagram below: <li>The test board design and final build can be seen in the images below: </ul>

Battery Containment Unit:
The Battery box design must conform to a PCB-104 form factor, 3.4in x 3.15in. Additionally, the box must weight less than 500g, ideally 300g. Due to the tight size constraints, the batteries must be packed in the following configuration:

The box will be made out of 3/16in thick 1100 1H4 aluminum with an integrated ventilation system on the top surface. Aluminum is used as the basis for the box due to its stable phase at cryogenic/pyrogenic temperatures and weight. The vent will be made by welding open-celled aluminum foam to the center of the metal sheet. The vent will have an internal lining of pyrogel XT-e. A silica aerogel blanket was originally intended but was later determined not viable due to a maximum operating temperature of 300 Celsius, half of the temperature released during thermal runaway. Instead, Pyrogel XT-E is being considered due to its operating temperature of 650 Celcius. Proof of concept is still required and two experiments have been designed to test the material's flame quenching, thermal resistance, and airflow properties. However, the literature available on these materials supports the current design.

The vent prototype is shown below:

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=Validation=

Software:
<ul> Successfully Completed </ul>

<li>Interfaced with the Iridium-9523 modem. <li>Validated Iridium network signals and achieved usable signal level and data integrity. <li>Transmitted short burst data messages and received them through an associated email account. </ul>

Future Validation: The software team plans to fly with VAST (Vandals Atmospheric Science Team) to test and validate that the communication from the Iridium-9523 is functional and performs the intended actions.

Carrier Module:
<ul> Successfully Completed </ul>

<li>Re-designed components: <li>New Boost Circuit: <li>Designed with the Texas Instruments Power Designer <li>Validated that it performs as expected with LTSpice and allows for worst case (~1A) current draw <ul> <li>New PCB Layout: <li>Form factor design with 4-layer technology built overseas. <li>Upgraded SAMD51 chip: </ul> <li>Microchip provides 15 page checklist to help with the building and test against. <li>Created the power supply requirements.

Future Validation: <li>After assembling the PCB, we will test the components onsite. <li>Testing will work with the Software subteam to ensure that code working on the initial carrier module will work on the re-designed board. </ul>

Battery Containment Unit:
<ul> Incomplete due to COVID-19 </ul> A series of experiments were designed to fail li-ion batteries, determine the approximate energy released during thermal runaway, and show how thermal runaway is transferred from cell-to-cell/module-to-module. A full list of the experiments is shown below. <ul> </ul> Initial testing was conducted with a two-cell Zippy brand Li-ion batteries. To fail the battery we connected two external leads and recorded the temperature of the battery with a thermal camera. Hydrogen gas production and temperature of 135oF were observed but extreme failure was not observed due to safety measures built into the batteries. Different Li-ion batteries with fewer built-in safety measures are required in order to observe extreme failure. As a result, we ordered several single 18650 Li-ion cells from Samsung. Experiment one has four procedures where thermal runaway will occur; short circuit, overcharge, external heat, and mechanical failure. The objective of this experiment is to determine the most reliable way to fail the li-ion cell for future experiments. Experiment two would look at how thermal runaway transfers from cell to cell and module to module. One cell would e forcibly failed and data would be collected with the thermal camera. This experiment will allow us to better understand how thermal runaway transfers between the modules and will determine the critical transfer temperature. Additionally, different lining materials will be tested for their effectiveness to halt the transfer of thermal runaway between the modules. The flames produced during thermal runaway are produced by hydrogen gas burning, not oxygen/nitrogen. As a result, the flames burn hotter and may not be as effectively quenched by the metal foam as oxygen-based flames are. Experiment number three would force a li-ion cell into a thermal runaway with the metal foam placed within the produced flames. Images collected with the thermal camera would be used to measure the flame propagation through the foam. From these images, the critical flame quenching distance can be measured. Should the foams effectively quench the flames they can be utilized in the final design. To determine the amount of energy released by a single Li-ion cell during thermal runway we would have built and calibrated a "coffee cup" calorimeter. A sealed powder coated junction box would hold the cell and be submerged inside another box with room temperature water. The cell would be forced into thermal runway and the change in water temperature would be used to determine the energy released by the cell. To calibrate the calorimeter, hot water would be poured into the junction box to determine the energy absorbed by the steel. The airflow test would determine how effectively the materials would ventilate pressurized gasses. The junction box would be sealed with a burst disk calibrated to a specified pressure. The materials of interest would sit next to the burst disk. Once the disk popped the pressurized air would escape through the material of interest. The time it would take for the air inside the box to return to atmospheric pressure would be recorded. Materials with shorted depressurization time would be better at ventilating the gasses built up during thermal runaway. The ventilation prototype consisting of the metal foam and pyrogel/silica fabric will be validated with this experiment. </ul> </ul>
 * 1) Forced Failure of 18650 Li-ion cells: </i>Development for Reproducible Failure Procedures</i>
 * 2) Transfer Mechanism of Thermal Runaway
 * 3) Flame Quenching Properties of Pyrogel and Al metal foam
 * 4) Determination of Energy Released during Thermal Runaway of Li-ion cells via Calorimetry
 * 5) Flowthrough Properties for Battery-Box Ventilation Materials

Future Validation: The experimental results from experiments two, three, and five would validate the selection of the materials for the final product. The final firebox prototype will be sent to Johnson Space Center for destructive testing to test it's resistance to mechanical failure.

=Team Members=

=Additional Documentation=

Project Schedule

Meeting Minutes