Kemper was slow to adjust to life in space, visiting Doctor Phlox nearly every morning after first joining the crew. As one of his first assignments on Enterprise, Kemper participated in the rescue of Captain Archer, Commander Tucker, and the Xindi Kessick from a trellium-mining colony. Shortly afterwards, Kemper was a member of the MACO team which accompanied Archer to investigate a derelict vessel they encountered in the Orassin distortion field. (ENT: "The Xindi", "Anomaly")
The next year, Kemper was part of the boarding party led by Major Hayes to a Xindi-Reptilian warship to rescue Ensign Hoshi Sato. During the action, Kemper was wounded, but was expected to make a full recovery upon treatment by Dr. Phlox. (ENT: "Countdown")
Kemper was also mentioned in dialog in "Countdown".
In the script of "The Xindi", Kemper is said to have come from Canton, Ohio, rather than Duluth, Minnesota. Kemper was played by Nathan Anderson, who is also from Duluth, Minnesota.
In the novels Last Full Measure and The Good That Men Do, Kemper's first name is Nelson. The latter of those books also depicts Kemper attending the signing of the treaty for the Coalition of Planets, having left MACO service to have a daughter with a MACO corporal named Selma Guitierrez. The Star Trek Customizable Card Game gives his name as Nelson Kemper, as well.