[3] He completed his training on February 10, 2006, and was assigned to STS-119, which flew from March 15 to 28, 2009, to deliver the final set of solar arrays to the International Space Station.

Acaba's parents, Ralph and Elsie Acabá, from Hatillo, Puerto Rico, moved in the mid-1960s to Inglewood, California, where he was born.

Acaba spent two years in the United States Peace Corps and trained over 300 teachers in the Dominican Republic in modern teaching methodologies.

[1] Upon his return to the United States, Acaba moved to Florida, where he became shoreline revegetation coordinator in Vero Beach.

[12] Upon his return to Florida in fall 2012, Acaba began coursework in the College of Education at Texas Tech University.

[1][15] Acaba was assigned to the crew of STS-119 as mission specialist educator, which was launched on March 15, 2009, at 7:43 p.m., after NASA engineers repaired a leaky gas venting system the previous week, to deliver the final set of solar arrays to the International Space Station.

On March 21, he performed a spacewalk with Steve Swanson in which he helped to successfully unfurl the final "wings" of the solar array that will augment power to the ISS.

[21] He and his fellow crew members, Gennady Padalka and Sergei Revin, arrived and docked with the space station two days after launch, on May 17 at 4:36 UTC.

Until being selected as a flight engineer for Expedition 54\Expedition 55 Acaba served as Director of Operations Russia in Star City supporting crew training in Soyuz and Russian Segment systems.

[1] In September 2019 Acaba served as cavenaut[23] in ESA CAVES[24] training (between Italy and Slovenia) spending six nights underground simulating a mission exploring another planet.

On October 20, 2017, Acaba and Randy Bresnik performed an EVA to continue with the lubrication of the new end effector on the robotic arm and to install new cameras.

He received the Ana G. Mendez University System Presidential Medal and an Honorary Doctorate from the Polytechnic University of Puerto Rico,[34] where he inaugurated a flight simulator[35] on February 7, 2013, during one of his visits to Puerto Rico to promote the study of math and science among students, as well as to visit his relatives.