Undergraduates Taylor Peterson and Cassandra Bossong were in class in February 2020 when a notification appeared on Peterson’s laptop. It was from the Massachusetts Institute of Technology, and it had a word on it: “Congratulations.” Peterson slammed his hand on the table. “We won!” she blurted out. Peterson and Bossong, along with fellow physics majors Nicholas Bartel, Bennett Bartel, and Celestine Ananda of Carthage College in Kenosha, Wisconsin, had just won a $ 10,000 prize for promising university inventors – the 2020 Lemelson-MIT Student Award. Their feat: a new way to alert airplane pilots that they are out of gas. The technology, called thruster modal gauging (MPG), uses sound frequencies to determine fuel levels. It adapts for use in airplanes an experimental method of measuring the fuel of spacecraft. The MPG team was one of six student winners, having faced some 200 competitors from renowned universities.
“We were all in a state of shock and disbelief,” recalls Ananda, their former team leader, graduating in 2020 and now a PhD student in aerospace engineering at the University of Colorado. “But it turned into a kind of humility and pride that, even though we come from a very small school, we still have what it takes to compete with students from Stanford, MIT and Caltech.”
The Carthage team’s work spans research initiated by educational advisor Kevin Crosby, a physics and astronomy professor who worked for years with NASA research engineer Rudy Werlink. Werlink, the project manager at NASA’s Kennedy Space Center, came up with the idea and Crosby coined the name of the technology. A decade of NASA-funded experiments by Carthage students supplemented their research, as did the contribution of small aircraft pilots.
“Since our curriculum has an entrepreneurship component, the students had already started to think about how to translate what they were doing into other fields,” says Crosby.
Does not run empty
Unreliable fuel gauges have long bothered the aviation and space industries. The National Transportation Safety Board (NTSB) ranked fuel-related problems as the fifth leading cause of aviation accidents in 2017, the most recent year for which data is available. In that year, fuel outages accounted for 79 of 1,233 accidents, for an average total of 1.5 per week. An NTSB safety alert that year reported that fuel management caused, on average, more than 50 aircraft accidents per year from 2011 to 2015. Most of those accidents involved smaller craft.
In space, conventional methods of measuring the volume of propellant have not taken into account the behavior of the liquid. For example, the Space Shuttle’s capacitive probe system, which correlated the evolution of electrical charges at different fuel levels, failed in microgravity when fuel evenly coated the tank and probe, providing a “full” false reading. . Its pilots learned to estimate fuel levels by indirect methods, such as measuring tank pressure or recording the duration of engine burns. Today, international space treaties require a six-month propulsion margin for satellites on a 10-year mission so that they can be moved to cemetery orbits at the end of their service.
This means that satellites could carry more fuel than needed, a big deal for the weight-conscious industry. “Across the industry, those six months represent billions of dollars a year in lost revenue and payload mass that you can’t take just because you don’t know how much fuel is in. this tank, ”says Crosby.
Although engineers have come up with promising new approaches, NASA’s budget constraints and different agency priorities have hampered major investments in them. Lately, more affordable test methods associated with a planned crewed return to the moon as part of NASA’s Artemis program have drawn more attention to ways of accurately measuring fuel.
“NASA has been very interested in using it for space and satellites, but it has not been applied to the aircraft market,” Ananda explains. “It was something that had not been considered before, and we thought it could have a very big impact. “
Commercial jets use capacitive probes similar to those used on the Space Shuttle, which are more reliable in gravity but far too heavy and complex for small planes. Most light aircraft use a floating float with a lever arm whose changing position electronically signals fuel levels when the tank is emptying.
“In small airplanes, the fuel gauge is basically the same technology that is used in your car,” says Crosby. “So if you accelerate, go up, down, if there’s turbulence, or if you pitch or roll, the fuel gauges jump a bit.”
“The main reason for the inaccuracy of the fuel gauge is that the float tends to stick,” says Phil Holcomb, a flight instructor at Spring City Aviation in Waukesha, Wisconsin, which primarily operates Cessna, Piper and Cirrus planes. “The only important thing that I focus on with the students is to visually check the tanks with a fuel stick for the precise amount of fuel during the pre-flight inspection. By knowing the amount of fuel in the tank and your hourly burn rate, you can make a safe guess about how long you can stay in the air.
Even with safety buffers, like fuel reserve and pre-flight planning, faulty gauging can trap even the most seasoned pilots. Ed De Reyes, a retired U.S. Air Force experimental test pilot who is now CEO of Sabrewing Aircraft in Oxnard, Calif., Has already had to make an emergency landing in his Cirrus SR-22 after his Fuel gauge indicated a rapid drop to a quarter of a tank, only to later discover that it was over 60 percent full. “I still have no idea what caused this, but small planes are notorious for it,” he says. “I’ve had other times where the fuel gauges have told me I have more fuel than I actually have. I’ve seen planes where you fill up with gas, turn on the power, and the gauge only shows a half or even a quarter of a tank.
The problem is even more pronounced for aerobatic pilots. “The plane is only really going to give you an accurate reading on the fuel gauges when you’re in straight and level flight,” says Matt Stephenson, an aerobatic pilot in Eureka, Calif., Who flies a Super Decathlon. “When you are aerobatics, you are quite far from that.”
Adapting MPG technology from space to aviation presented two challenges: redesigning the device and calculations to account for gravity and assessing the market for its use in aviation.
MPG, which can be added to existing fuel gauges without structural modifications, uses sensors that record the changing acoustic vibrations of the tank as the fuel volume is depleted. One sensor vibrates the tank while two others record the tank’s response to vibrations. Dividing the response of these two sensors provides a set of frequencies representing a unique “fingerprint” for the tank that contains information about its mass. When fuel sticks to the walls, it adds mass to the tank, altering some of these frequencies. MPG can detect and relate these small offsets to the volume of liquid in the tank.
Still, the amount of fuel hitting the tank wall plays a role. In microgravity, the liquid spreads evenly along the interior surface of the tank. But in airplanes, the fuel laps unevenly against the tank, producing a different set of frequencies than the same volume in zero gravity. The students had to adapt their calculations to take this difference into account.
The market research, which cites a potential of $ 150 million in annual revenue, has proven to be more complicated for physics majors than tailoring frequency metrics. They had to look for ways to evolve manufacturing without sacrificing quality.
For example, a space-grade material must be able to resist radiation and vibration, and not emit gases. “All of these qualifications make the components very expensive, but are not necessary for airplanes or ships,” says Ananda. “So our team looked for many ways to make this much cheaper and mass produced in the future. “
Promote undergraduate research
Crosby founded the Space Science Program at Carthage College in 2006 to foster undergraduate space research. Two years later, its participants began working with NASA under its former Systems Engineering Educational Discovery (SEED) program, pairing teams of students with NASA researchers for microgravity experiments. Their work with Werlink began in 2011, after he launched a call through SEED for student experiences to test his ideas for MPG technology. When SEED ended in 2013, Crosby took on the role of Principal Investigator and secured other grants from NASA. The agency’s recent flight opportunity grants will support MPG weightlessness testing for NASA’s Lunar Gateway Outpost, a component of the Artemis mission.
“We’re a small midwestern university with no engineering program and few aerospace employers nearby, and we have students going to work at NASA, Boeing, and Blue Origin,” says Crosby.
A major advantage was to test their work aboard Zero Gravity Corporation’s parabolic flights which simulate 20 to 30 seconds of weightlessness. The students also conducted experiments on unmanned parabolic flights to space aboard Blue Origin’s New Shepard rocket.
“To experience weightlessness is just the coolest thing in the world,” says Ananda. “The problem is, after doing this for an hour and the adrenaline starts to wear off, I almost always inevitably vomited on the very last dish. It’s not great, but it’s totally worth it.
Crosby has raised more than $ 13.4 million over 11 years for the space science program, which now includes six projects, three of which involve MPG technology. The MPG experiment continues. The approach is among the main candidates for NASA’s next generation of fuel gauge solutions and was recently approved for a 30-day test aboard the International Space Station in 2023.
Susan Karlin is a freelance journalist based in Los Angeles. His stories have been published in Wired, American scientist, and the New York Times, and she writes frequently on the future of transportation.