From Halopedia, the Halo wiki
Sometime in 2531, Prescott was involved in repairing the Spirit of Fire during the Harvest campaign. After the removal of the ship's FTL reactor during the Battle of the Etran Harborage, he determined that fashioning a new one out of existing spare parts was impossible. By 2559, he had been replaced as chief engineer aboard the ship by Lieutenant Commander Alys Vallum.
A short story about Prescott was written by Halo Wars writer Graeme Devine prior to the release of Halo Wars, as part of the game's development. The story is self-described "fan fiction" and thus non-canon. In it, Prescott is described as an older man with a military background and reactivated for duty by Vice Admiral Cole after the glassing of Harvest. Before that Prescott was intensely interested in building and racing high-speed cars on Mars, using a pulse-detonation propulsion system. Following the outbreak of the war with the Covenant, he was stationed at Fort Marshall, pending transfer to Spirit of Fire.
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