ASGP: CubeSat

The ASGP Cube Sat Team

Introduction
The Alaska Space Grant Cube Sat project was a two-year effort to develop a small cubic satellie; also known as a "cube sat." Developments of cube satellites and small satellites are prevalent and widespread. Our efforts centered around developing a baseline utility system that would eventually be able to accept any scientific package. This would allow scientists to focus on developing the experiments and gathering results, rather than worrying about designing a one-off satellite package suitable for space conditions. Our satellite package provided an attitude control system (ACS) and solar panel charging system (SPS) for the satellite which allowed the satellite to actively orient itself with respect to the earth and provide power for the on-board systems and science, respectively.

Both years, the project was accepted into the NASA Microgravity University, which is a two-week research experience that takes place at Johnson Space Center, Houston, TX. The program chooses a handful of projects from across the nation and provides students with an opportunity to test their experiments and prototypes in micro-gravity conditions on the famous "Weightless Wonder."

The "Weightless Wonder"

In addition, students were run through training for the flight including altitude chamber testing, where we experienced the symptoms of hypoxia. As engineers, we were also put through a rigorous flight-readiness certification and FAA-modification certification process which ensured that our flight setup was safe for the "aggressive transport" and gravitational cycling (see image above to get an idea).

Project Design
I worked on both iterations of the satellite over the two year span of the project. On the first iteration, I was a mechanical fabricator working on building the systems. On the second iteration I became a mechanical designer as well as fabricator and traveled with the team to Houston over the summer.

Every project has interesting constraints that engineers, designers and fabricators have to work within. This project, however, seemed to take them to extremes. To list just a few of NASA's limitations: all fluids had to be double bagged, our entire satellite could not exceed 10 centimeters on any side, and we had to show that the magnetic coils in our ACS would not interfere with the aircraft's control or navigation systems. We also had restrictions of our own. For instance, in order to be useful as chassis for future science experiments, the ACS and SPS had to use take up very little room in the satellite. They also had to use very little power and be completely solid-state.

This is the volume of the cube sat

To make the most of our available volume, we utilized "cube corners" which were small, solid aluminum squares that mounted in each corner of the satellite. They provided the structural rigidity for the satellite, but also served as mounting points for the internal electronics and solar panel deployment system. This allowed maximum use of the available volume for future science packages.

For the solar panel deployment system, the SPS, we designed a system that utilized shape memory alloy, also known as "memory metal." This is an alloy that, when subjected to current, changes shape due to Joule heating. It served as a lightweight, small, solid-state actuator that tripped the solar panels, freeing them from their stowed position. Since they were controlled by the application of a voltage, it was simple to program either an automatic or manual control for the panels. For the purposes of testing, we used aluminum plates to approximate the solar panels:

A video of the first deployment, some tuning was still required.

After designing, fabricating, and testing our apparatus (not to mention finishing the mountain of paperwork and reports!) we prepared for our trip to JSC at Houston which was both a fun and challenging experience.

Fun: Sitting at Mission Control for the Apollo Program

Challenge: Preparing the apparatus for on-board testing (but fun as well)

The big payoff was seeing our year-long project come together in time to be tested on board the aircraft. We were able to have fun floating in zero-gravity while also accomplishing science, including a couple projects put together by local middle schools during our outreach program. One question, "What happens to a helium balloon in zero-gravity?" was answered by the star-shaped balloon floating in the background of the picture below.

Truly a once-in-a-lifetime opportunity coupled with an invaluable learning experience.