Skip to main content

Space Sciences

Modal Propellant Gauging (MPG)

The MPG project is a collaboration between Carthage Space Sciences and Kennedy Space Center Cryogenics Laboratory to develop a high-resolution low-gravity fuel gauging technology by exploiting the effect of fluid loading on the structural properties of liquid-filled propellant tanks. 

Experiment Background

Comparison of low gravity and earth gravity equilibrium shapes of propellant

Conventional methods of measuring propellant volume are ineffective in microgravity conditions. Instead of using direct buoyancy based techniques, spacecraft must rely on indirect techniques such as equation of state methods and burn-time integration. Indirect methods often require additional hardware to pressurize tanks and are inaccurate at lower fuel levels. Microgravity causes fluid sloshing within the tanks, further complicating the estimate of propellant volume. We present a non-invasive, indirect fuel gauging technique based on real- time measurements of the tank’s resonant acoustic modes.

Experimental Modal Analysis (EMA) involves recording the vibration spectrum of a solid object and using the spectral characteristics to infer the structural properties of the object. The EMA technique requires that we stimulate all acoustic resonances in the tank structure by applying a broadband white noise signal. Tank response is measured at discrete locations on the surface of the tank and the Fourier Transforms of the response and input functions are computed in real- time. Finally, the Frequency Response Function (FRF) for each structural response is computed by essentially taking the ratio of the response FFT to the input FFT. The resulting FRF is a complex-valued function in which the real part is a function of the effective mass of the vibrating object and the imaginary part is related to the rate of energy dissipation through structural damping. Adding fluid to a tank lowers the real part of the frequency by increasing the effective mass. In addition, fluid in a closed tank changes the imaginary part of the frequency by damping the vibrations.

Carthage College’s Microgravity Team has been developing this method since a 2011 reduced gravity flight campaign under the NASA Systems Engineering Education Discovery (SEED) program. In 2012, the SEED team demonstrated that EMA is a promising fuel gauging method with a resolution of 10% of the total volume of the tank in the case of unsettled, sloshing liquid. Carthage’s 2013 RockSat-C team further tested the precision of this technique with an experiment on a sounding rocket launched from Wallops Flight Facility: the maximum resolution achieved was 1.5% in volume for fill fractions from 30% to 70% and 7.4% in volume between 0% and 20% fill fractions. A 2014 USIP/FOP flight campaign demonstrated a liquid volume resolution of 2.0% for fill fractions between 30% and 70% of total tank volume (unsettled, zero- g measurements). The 2015 NASA/FOP flight campaign achieved resolutions of 1.5% for sloshing propellant simulants at fill fractions between 20% and 60%.MPG 1-g Modal Response Data

  • Quick Facts

    • Carthage is named a Best Midwestern College by The Princeton Review (2017), a designation given to only 25 percent of four-year schools.

    • Scheduled to open in fall 2018, a new residential tower will offer suite-style housing and two floors of shared campus spaces for gaming, cooking, group meetings, or quiet studying. Learn more about The Tower

    • You’re going to need brain fuel. Grab a morning coffee and a snack and Starbucks or Einstein Bros. Bagels. Later, meet friends at “The Caf,” where the specials change daily but the staples are constant, or swing through “The Stu” for wins, a burrito, or a sub. A new option, Carthage Cash, even covers some off-campus meals.

    • 96% of Carthage alumni report that they have secured a job or are continuing their studies six months after graduation. Visit Career Services.

    • 91% of employers say critical thinking, communication, and problem-solving skills matter more than your major when it comes to career success. Learn more about how the liberal arts prepare you for a successful career.

    • Lots of schools wear the four-year label. Carthage stands behind it. 95% of Carthage graduates earn their degrees in four years. Learn more

    • Oscars. Emmys. Tonys. Golden Globes. The playwrights we’ve brought in have them. Each year, the Carthage Theatre Department commissions an original script by a renowned playwright for its New Play Initiative. Carthage students then work with the writer to stage it. 

    • As a freshman in the highly selective Honors Program, learn how to gain expertise in anything from music to forest ecology. After that, tackle a contemporary social, economic, or political problem. If you like, you can live on an Honors-only floor of a Carthage residence hall. 

    • In 2016 and 2017, Carthage was named a top producer of Fulbright Scholars by the U.S. Department of State’s Bureau of Educational and Cultural Affairs.

    • Things look new at Carthage because they are. Our athletic and recreation center, student union, computer labs, audiovisual production suite, and numerous residence halls have all been constructed or newly renovated in the last 10 years. Our new science center caps it off.

    • Carthage offers majors, minors and concentrations in more than 50 areas of study, from archaeology to athletic training, neuroscience to music theatre.

    • Our Summer Undergraduate Research Experience offers select students a research budget, one-on-one mentoring with a professor, and 10 weeks of analyzing, deciphering — and getting paid.

    • So the lake is kind of a focal point, but there’s a lot more to love about our campus — like the fact that our 80-acre campus is also an arboretum and wildlife sanctuary. Focused on keeping campus lush forever, we plant between 50 and 75 new trees every year from a variety of species.

    • Carthage was founded in 1847. That’s more than 170 years of leaders, makers, and go-getters going out and going forth. Read more about Carthage’s rich history.

    • More than 90 percent of our students receive financial aid, a hefty chunk of which is scholarships and grants — including $1.25 million annually from the Presidential Scholarship Competition and numerous Merit Scholarships. Learn what’s available.

    • Abraham Lincoln was an early Trustee of the College, and U.S. Secretary of State John Hay was a Carthage alum. The two still have a proud place on our campus. Spend some time with them in our Sesquicentennial Plaza. On warm days you’ll find professors leading their classes here.

    • Come to Carthage; hear yourself think — think … think …
      Legend has it that Sesquicentennial Plaza holds a perfect echo. Just stand with both your feet on the “1847,” face Straz, and start talking. “You’re the only one who can hear you, but you’ll be crystal clear,” promises English and theatre alumna Mikaley Osley.

    • Our Great Lake provides Carthage students with some amazing views. Think classes on the beach, lake views from the lab, and sunrises from your dorm room. “I love waking up in the morning with the sun shining off the lake. Nothing compares to the view in the morning,” says biology and neuroscience major Ann O’Leary.

    • Carthage awards up to 30 Presidential Scholarships each year, which range from 75% tuition up to full tuition, room, and board. Learn more.

    • For a full decade, NASA has selected Carthage students to conduct research aboard its zero-gravity aircraft. Lately, the stakes have risen. A team of underclassmen is grinding to prepare a tiny but powerful Earth-imaging satellite for launch to the International Space Station. Learn more about the space sciences at Carthage

    • Carthage is the only college or university in the Midwest where every freshman takes a full-year sequence of foundational texts of the Western intellectual tradition. Learn about the Carthage core.

    • With a student-faculty ratio of 12:1, your professors will know who you are. They will also know who you want to be — and how to get you there. Meet our faculty.

    • There are more than 120 student organizations on campus, from Amnesty International to Chemistry Club, to Frisbee and Latin Belly Dancing. See how easy it is to get involved.

    • True story: There are more than 27 art galleries, a dozen museums, and nine theatres within 25 miles of Carthage. Some highlights: The nationally recognized Racine Art Museum, the world-renowned Art Institute of Chicago, and the Milwaukee Art Museum. Learn more about our location.

    • What’s better than one professor? Two professors. What’s better than two professors? Two professors from totally different fields teaching a single class. There’s debate. Discussion. Differing perspectives. This is where the magic happens. That’s why every student takes a Carthage Symposium.

    • Imagine presenting your original research at an international conference — as an undergraduate. Carthage is dedicated to undergraduate research. Learn more about current opportunities.

    • You can’t hide here — not with only 17 other students in the classroom with you. That’s going to be rough some mornings. But later, when you’re able to argue your point of view thoughtfully, express your opinions succinctly, and meet challenges head-on, without fear … Yep, you’ll thank us.

    • Carthage is ranked No. 5 in the country for student participation in short-term study abroad. Every J-Term, hundreds of students travel all over the world on faculty-led study tours. Imagine a month in Sweden, Rome, Cuba, Senegal, India, Japan …