ME 72 Takes to the Sky for Rousing Match of Quidd ... Airship Quadball

There were no brooms or bludgers in sight on the basketball court inside Caltech's Scott Brown Gymnasium on March 8, but it was hard not to think of everyone's favorite teenage wizard and his sporting pastime while watching the 39th annual ME 72 Engineering Design Competition. As onlookers cheered from the stands, remotely controlled blimps maneuvered through the air, scooped up shiny blue, floating balls, and sometimes sent them through goals raised 10 feet off the ground.

Every year, third-year mechanical engineering undergraduate students at Caltech take ME 72, a two-term, project-based course that culminates in the engineering design competition. The details of the challenge vary from year to year (previous students have been tasked with building amphibious robots, "SumoBots," and robotic tanks), but the competition always shows off the ingenuity and engineering capabilities of the student teams that spend hundreds of hours designing, building, testing, and reimagining their entries leading up to the course's big finale.

This year's challenge, dubbed "Airship Quadball," was the first aerial battle of the bots in the competition's history. The task—dreamed up by the course's advisor, Michael Mello (PhD '12), teaching professor of mechanical and civil engineering, and his teaching assistants—sounds simple enough: Design and build as many as three helium-filled, lighter-than-air vehicles to intercept neutrally buoyant balloons and push them through one of three goals on the other side of a court.

In reality, every aspect of the task, including what material to use to make the airships, what shape to make them, and what hardware and electronics to use to maneuver them through the air, was extremely tricky.

"It's much harder than it looks. For the human eye, it is challenging to see a ball distantly and somehow remotely guide your balloon toward it," Mello says. "Then there is the buoyancy and weight restriction. You only get so much vertical lift force from helium. Every ounce matters, so the students had to make lots of decisions about what materials to use and what tradeoffs they were willing to make."

The students worked in five teams with four or five members each—B.O.O.M. (Blimp Operations Of Mayhem), Las Aguilas Azules, Led Zeppelin, Mechromancers, and M.O.A.B. (Mother Of All Blimps). Beginning in the fall term, the students first attended orientation lectures and then began the design phase of their projects. By the end of that first term, each team had to complete a mobility milestone and show that one of its blimps could fly and be steered. Then came the big push during the 10 weeks of winter term when the teams repeatedly prototyped, tested, brainstormed, and made adjustments to arrive at the final products that eventually took to the air in Brown Gym.

After one team discovered an excellent heat-sealable metallized film (sheets of a mylar-like material that can be ironed together) all the teams ended up using it to make the balloon "envelope," the blimp part of their airships. All the teams also used thin, flexible carbon fiber rods or balsa wood to create and integrate a frame structure to their blimp. But beyond these similarities, each team came up with its own design and method of maneuvering.

"It's really remarkable to see what they've come up with," Mello says.

Working in the Jim Hall Design and Prototyping Lab in the subbasement of the Eudora Hull Spalding Laboratory of Engineering, the students spent most of their afternoons, and many evenings, building and tweaking their airships. Among other tools, teams this year relied heavily on 3D printers to fabricate custom lightweight joints and carriages for the onboard electronics.

"A lot of it has been prototypes, testing, failing, more prototypes, more testing, and failing, sort of going through a bunch of iterations of things," says Sofia Syed, one of the students on team B.O.O.M. "Last term, we worked on one style of electronics for the entire term until our final mock demo, and it didn't work as well as we'd hoped, so we had to revamp our design almost completely."

Mello says such experiences are completely expected and are kind of the point of the class. Being able to work through problems and learn to communicate constructively with teammates, delegate tasks, follow schedules, and put in the time needed to "really grind on a problem" are some of the core values and abilities that ME 72 drives home, Mello says—and they are invaluable to engineers in the workforce.

Payal Patel from the Mechromancers team added that the students in the course also learned a lot from the experience of creating something from the ground up. "I'm not likely to be building a blimp in the future, but I think the process of building something from scratch is definitely something that I can carry over," Patel says. "We had to be very adaptable in this project because no one's really ever done this. Given the time limit that we had, we had to think quick on our feet."

The day before the competition, students from team M.O.A.B. were making last-minute preparations, printing extra pieces, and ensuring the mesh carriage beneath the blimps, which is used to capture balls, was ready. Isabelle Ragheb was feeling pretty confident about her team's vehicles. "We've put in a lot of time and effort, but there are always last-minute things," she said.

Teammate Miles Jones agreed. "Sometimes, when you're flying, you just get unlucky. So just trying to control the controllables is the name of the game for us."

M.O.A.B. worked hard to increase the maneuverability of its white airships and the accuracy with which they were piloted. At one point, the students changed the configuration of the electric ducted fans that steer the vehicles and push captured balls through goals. The team also added large cardboard fins to their blimps to improve stability. They even started 3D printing their airships' joints in a different orientation when they noticed that they were all cracking in one direction. "We have gone through so many iterations," Jones says.

On the day of the competition, all the students' hard work paid off. The five teams competed in a round-robin style tournament with one team facing off against another in four-and-a-half-minute battles, trying to capture the most balls and score goals. If an airship captured and held onto a ball until the end of the match, it earned its team one point. If it managed to push a ball through any of the other team's goals in either direction, it garnered two points.

Onlookers cheered when the blimps scored and sometimes groaned when an airship faltered. Students worked feverishly along the sidelines trying to make needed repairs and adjustments as the tournament progressed and some of the airships suffered damage.

Middle school students from Sierra Madre Middle School were on hand cheering for their favorite teams. "I bring them every year just to inspire them for the future," said Ravi Dev Anandhan, a science and robotics teacher at the middle school. "They see the end goal, and it motivates them. We enjoy it so much. Every year is different, and the students are completely wowed by it."

After the initial round-robin tournament, in which each team faced off against everyother team once, one of the five teams was eliminated and the remaining four teams headed into the semifinals. Throughout the tournament, M.O.A.B. dominated each faceoff, racking up as many as 23 points in a single round. M.O.A.B. faced off against the Mechromancers in the final round. With under a minute left on the clock, one of the Mechromancers' pink blimps pushed two balls through a goal, narrowing the score to 8-6, and the crowd went wild. M.O.A.B clung to its lead by capturing and holding eight balls as time expired, and walked away with the ME 72 gear-shaped trophy.

Still, AJ Torres from the Mechromancers said after the competition that she had loved everything about the event. She had been excited about taking ME 72 since she first heard about the course. "It has really lived up to my expectations," Torres said. "I just feel sad that the class is over. It's going to be lonely without the shop."