Making the Zero-G plane more accessible to deaf and hard-of-hearing researchers

The weightlessness aboard the Zero-G Corp.’s modified Boeing 727 is helping the AstroAccess project with its goal of making space friendly to people with disabilities, including those who are deaf or hard of hearing. Brenda Williamson tells the story of her undergraduate project to create an automated lighting system to warn when the weight is coming back.

If we are going to succeed in exploring outer space, we can’t afford to leave 15% of the world’s population behind just because they are disabled.

The AstroAccess project, with a largely volunteer staff in multiple countries including the United States, is determined to solve that problem for those with mobility, vision and hearing disabilities. I joined the team as director of logistics in April 2021, while I was earning my aerospace engineering degree at the University of California, San Diego.

In that role, I was given a meaningful assignment that also showed me the patience and perseverance that all of us in the space community must have: I was to equip the padded cabin of the Zero-G jet with a system of experimental color-coded LED lights that would automatically alert AstroAccess’ deaf or hard-of-hearing “ambassadors” aboard the plane when the g-force was about to return.

The Zero Gravity Corp. flies researchers and enthusiasts aboard a modified Boeing 727-200 that can be flown from any of dozens of airports in the United States. The pilots steer the aircraft up and down in a series of U-shaped, or parabolic, maneuvers that are tailored to replicate the weightlessness of free fall around Earth, or the gravity on the surface of the moon or Mars. The flights are a great way for the AstroAccess disability ambassadors and flight operations crew members to test the viability of designs, as well as identify modifications that will make spaceflight systems universally accessible. I was excited to learn that I would be flying with my experiment in a mission targeted for May 2023 — shortly before my graduation — under the 2023 Horizon Zero Gravity Flight program organized by the Aurelia Institute, a nonprofit space architecture group based in Cambridge, outside Boston.

My flight would not be the first time deaf or hard-of-hearing participants were aided by lights. Previous versions were controlled manually by one of the Zero-G flight coaches holding a smartphone equipped with an app and a Bluetooth connection. Green was for micro or zero gravity, red was for hypergravity and blue meant steady level flight. The lights were found to be beneficial not only by AstroAccess’ deaf/hard-of-hearing crew but also by multiple flyers regardless of their hearing level. My job was to remove the necessity of asking a Zero-G coach to press buttons on the app.

The experiment became a project for my final design course required for my aerospace engineering degree. For the automation, I knew I would need an accelerometer to detect shifting g-forces. My Aerospace Engineering Design II professor, Mark Anderson, gave me an accelerometer breakout board purchased from Adafruit, the New York City-based supplier of electronics for educational and home projects. It was a small circuit board with breadboard-ready pins that could be used with the Arduino UNO microcontroller kit I already had. The accelerometer board would detect the z-axis (downward) acceleration of the plane, and the code I wrote for the microcontroller would take its input and trigger the appropriate light color.

Using the individual LED bulbs the kit came with, I was on my way to making a prototype. While I was working on that, the Aurelia Institute hosted an online course to help me and the rest of the Aurelia Horizon 2023 cohort with our designs for the microgravity environment. I reported my progress to both Aurelia Horizon and my senior design professor, and I was also working with AstroAccess’ deaf/hard-of-hearing crew for their input on the design.

Over the next two weeks, I came up with a few different ways of testing my design on the ground in order to refine the hardware and software and to make sure it would behave as I expected in flight. When I was finally confident with its performance during testing, I had about 1,000 lines of code and a plywood-mounted circuit. This system was capable of detecting changes in g-forces and shifting the colors, while also collecting acceleration data for analysis post-flight.

And then the flight was delayed a year to 2024.

During that time, I graduated and did some additional testing with the team at the Arthur C. Clarke Center for Human Imagination at UCSD. They have a centrifuge in their Space Lab that can apply multiple gs to small payloads. This was a great way to make sure my accelerometer would react to a change in gs as I expected. Additionally, the Clarke Center generously covered my experiment and travel costs.

Last month, as I sat in the back of the Zero-G jet bound for our assigned airspace off the coast of New Hampshire, it hit me that it was finally happening. Three months of work and a year of waiting had led me to this moment, and in less than 5 minutes I was going to know if any of it was going to work. I reminded myself that even if the lights absolutely failed, I would have plenty of data to tell me what went wrong and what to do to fix it. In the event that the lights did fail, I had a few alternatives to choose from: My circuit included hard-wired buttons that could be used to manually control the lights instead. However, I realized that for data collection purposes, it would be better for me to let the lights run “incorrectly” should they fail, so I could assess what happened and fix them for next time. Also, if the changing colors became confusing or even began to pose a hazard to participants, I could use the “lights off” switch I’d built into the system to turn off the strip of lights without disrupting the code or the data collection.

We moved to the cabin floor and were just about to start the first parabola when I applied power to the whole thing for the first time in-flight. I was looking for blue lights, which meant steady level flight. It was highly unlikely my code would fail here. When I flipped the “LED strip on” switch, we had blue.

Moments after I applied power, we had to lie down on the white vinyl cushioned floor and stare at the ceiling for the hypergravity to start as the aircraft climbed. Soon, we had red lights coloring the walls and floor — so far, so good. First up was Martian gravity, which is about three-eighths of Earth’s gravity. This means a 130-pound (60-kilogram) person would feel like they are about 50 pounds (22 kg). I was waiting for green.

Right on time, the lights turned green. After a few brief moments of euphoria as I enjoyed the feeling of lightness, they quickly turned red way before they were supposed to. Very few people around me truly understood what my lights were doing except for the Zero-G coaches, so there was no reaction from anyone when the lights turned red, except for me. In the heat of the moment, I pointed to the lights and shouted “They’re red!” but no one really cared or understood that was a bad thing. Everyone was too caught up in the moment. So I held my breath and waited for the next parabola.

I laid down once again, and right as the plane slowed in its climb and I felt the weight release, I saw green. And it stayed green for the duration it was supposed to.

At this point, I knew the lights were working. For the rest of the flight, they transitioned between red, green and blue exactly how I was expecting them to. I hoped the other flyers were taking note, but it was hard to be certain in the busy cabin.

Besides testing the automated light signaling system, this was also my very first time experiencing weightlessness. Many people told me it feels like the drop of a roller coaster. I would describe full weightlessness as swimming down into the deep end of a pool and curling yourself into a ball, not moving a muscle, and just existing there until your own buoyancy carries you slowly back up to the surface. If you give yourself the gentlest of pushes during zero gs, you will float to the top of the cabin in a very similar way. Having spent a great deal of time in pools, the sensation was surprisingly familiar.

When we returned to the hangar, I asked the participants who were in my general vicinity aboard the plane if they had noticed the lights. I was hit with simultaneous exclamations of positivity, excitement and amazement. They said they couldn’t hear anything above the cacophony of the cabin and relied on the lights for their cues. Some even thought the lights were installed by Zero-G itself as part of the standard flight experience.

Now, my next steps are to analyze the data and quantify how close the lights actually were to the Zero-G verbal warnings. Then, I can continue working with AstroAccess to see how it wants to implement this technology on future parabolic flights.

Brenda Williamson

Black and white photo of a smiling woman with long, dark hair, wearing a collared shirt. She is looking directly at the camera.

is the former director of logistics at AstroAccess. She holds a Bachelor of Science in aerospace engineering from the University of California, San Diego.

A wooden board with an assembly of electronic components and wiring, including an Arduino, power supply, buttons, and a connected LED strip that coils beside the board, emitting blue light.
The day before her Zero-G flight, Brenda Williamson turned on the signaling lights to verify that they would operate with power supplied by the company’s modified Boeing 727 aircraft. During the flight, Williamson’s software code prompted the lights to change automatically, a task that was previously done manually by one of the flight crew. Credit: Brenda Williamson
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Credit: Graphic by Thor Studio

Making the Zero-G plane more accessible to deaf and hard-of-hearing researchers