NASA Ames Suborbital Flight Communication

While the barriers to space flight have been reduced due to the privatization of launch vehicles, two large hurdles remain for those seeking to conduct research in space: orbit-to-ground communication, and reentry recovery. Our work seeks to reduce these barriers through research in these areas.

Communication costs can be reduced by using consumer satellite phone modems, specifically the Iridium Core 9523, to give satellites in low Earth orbit (LEO) access to a constant internet connection. Satellites and other devices operating at or below LEO and equipped with such a module would be able to stream data to Earth without the need for users to apply for frequency licenses, while also eliminating the need for prohibitively expensive radio equipment.

Additionally, our research looks to solve the current lack of recoverability of small satellites. Through the development of a Tube Deployed Reentry Vehicle (TDRV), we will allow satellites a means of surviving reentry so that equipment can be reused, or physical samples collected and returned to Earth.

Continuing work started by the Technical Education Satellite (TechEdSat) research group led by Marcus Murbach at NASA-ARC, we are utilizing the Iridium satellite constellation to communicate with satellites in LEO. The TechEdSat team has demonstrated that Iridium modules such as the 9602 Short Burst Data (SBD) transceiver are fully functional in orbit and are able to communicate with the Iridium constellation. The next step in this research is to develop a carrier module for the Iridium Core 9523 modem that adapts the core for use in a cube satellite. The Iridium Core supports a 2.4 kbit/s data stream compared to the 9602’s 340-byte packets. The 9523 is currently used in NASA’s Reentry Breakup Recorder (REBR) to transmit reentry data while falling at sub-sonic velocity post-reentry. As such, we believe the 9523 shall also operate normally in LEO and provide a stable data connection. The NASA-ARC TechEdSat group has also been working to develop a three-stage Small Payload Quick Return (SPQR) device designed to return small payloads from the ISS back to Earth in a temperature and pressure-controlled environment. The middle stage of this device is developed under this project and consists of the TDRV.

=Project Background= A multi-year project, the goals of this research team have been incrementally furthered by each successive design team over the course of nearly five years. Due to the highly ambitious nature of this project, it is likely this project will be continued for several years into the future before it is flight-ready. This section outlines the prior work done by past senior design teams.

Team GPS (Guided Parafoil System) 2014-2015
Team GPS Wikipage

In 2014, Team Rocket focused on the development of a carrier module for the Iridium 9523 Core to allow for its eventual integration into a cube satellite. Their primary objectives were as follows: Create a carrier PCB for the Iridium 9523 Core Develop and Arduino library for the 9523 Using an NAL A3LA-RS Iridium module, test software to establish a dial-up connection

Rocket was ultimately only able to accomplish a few of their goals, primarily the creation of a prototype carrier board. Their notes and SCUBEE testing indicate their PCB is not functional and does not properly interface with the 9523. However, team Rocket made significant progress with software development, creating the base for what team ACOM would use the following year.

Team Rocket 2016-2017
Rocket Wikipage

In 2016, Team Rocket focused on the development of a carrier module for the Iridium 9523 Core to allow for its eventual integration into a cube satellite. Their primary objectives were as follows: Create a carrier PCB for the Iridium 9523 Core Develop and Arduino library for the 9523 Using an NAL A3LA-RS Iridium module, test software to establish a dial-up connection

Rocket was ultimately only able to accomplish a few of their goals, primarily the creation of a prototype carrier board. Their notes and SCUBEE testing indicate their PCB is not functional and does not properly interface with the 9523. However, team Rocket made significant progress with software development, creating the base for what team ACOM would use the following year.

Team ACOM (Advanced Communication Device) 2017-2018
ACOM Wikipage</li>

In 2017, Team ACOM was tasked with several goals aimed at advancing several aspects of the SPQR device and associated projects. Their primary objectives were as follows: Develop software for the Raspberry pi to allow use of the Iridium 9523 as a dial-up modem</li> Create a remote server to send data to using the 9523</li> Create and test a mesh network using ZigBee 900MHz radio modules</li> Create and test fly a prototype TDRV device</li>

ACOM was ultimately only able to accomplish a few of their goals, primarily the creation of a prototype TDRV and initial testing of basic software for the Iridium 9523. The TDRV prototype was 3-D printed using PLA plastic and drop-tested in the ASUI Kibbie Dome. Reports indicate the Iridium had difficulty sustaining satellite contact was was never able to initiate a dial-up connection. However, it appears short-burst-data (SBD) messages were able to be sent. No electrical hardware was created.

Specifications
This project shall develop the hardware and software required to achieve a live network connection from a cube satellite in low earth orbit to a remote ground-based server using the Iridium Core 9523 satellite communication module.

This project shall also further develop and optimize the Tube Deployed Re-entry Vehicle, a three-stage re-entry vehicle launched from an orbital payload at the Von Karman altitude.

=Design=

Mechanical Design


We made a number of improvements to team ACOM's design, including:
 * Replacing the felt material with ripstop nylon to increase the effectiveness of the descent arrestor;
 * Replacing replacing the rail-mounted endcap and nosecap with a press-fit design;
 * Reconstructing the interior to accept a configurable electronics tray;
 * Mounting the GPS and Iridum antennas on the endcap, in addition to the drop mechanism;
 * Introducing descent arrestor hard-stop stabs for deployment testing; and
 * Replacing the 3D printed body with a machined tube to improve the strength-weight ratio.

This design was tested to have a maximum velocity of 17.5 meters per second.

Electrical Design


The board contains an SAMD21 ARM Cortex-M0+ microcontroller.

The board provides two serial connections: one is connected to the microcontroller for normal use, and the other connected directly to the modem for testing.

The modem requires a 30W power supply to send data, so LR3959 boost converter was used to provide the necessary power from an 8V input.

Software Design


The library was designed to use a simple command/response packet system.

The library was designed to provide four modes of operation:
 * OFF, where the modem is disabled;
 * RAW, where all data packets are sent directly to the modem;
 * SBD, where all data packets are converted into Short-Burst Data packets, which is the format currently used; and
 * TCP, where all data packets are streamed over a TCP/IP connection, which is the primary goal of this project.

Two versions of the library were created. The first version is designed for use on a microcontroller and is optimized to use as little memory as possible. The second version is designed to run on a computer and provides debugging information to assist  future software development.

GitHub Repo

=Team Members=

=Additional Documentation=

Presentations: