Commandant Gerald Simpson commands the International Rescue Organisation (IRO) from its Pacific Island base, Arcology, in 2086. Holding the rank of commander, he serves as primary mission coordinator for the Thunderbirds team, remotely directing all rescue operations without entering the field—mirroring Jeff Tracy's leadership role from the original series.

Born in Washington, he pursued advanced aerospace, industrial, and systems engineering studies before becoming a NASA deep space explorer. His career culminated in commanding the UNSS Clarke spaceship, leading to his appointment by the World Federation to establish and head the IRO. His intensely dedicated leadership prioritizes organizational duties over personal recreation, occasionally straining family relations; his brother Wayne uses the affectionate nickname "Gerry" during private moments.

He maintains a professional yet avuncular dynamic with his seven-year-old nephew, Skipper Simpson, who idolizes the Thunderbirds and dreams of joining IRO. Though Skipper remains a civilian, their familial bond occasionally intersects with organizational activities. Early production materials alternately titled him "Dr. Gerald Simpson" in archival press kits and select merchandise packaging.