Allen served as mission specialist on
STS-5, the first fully operational flight of the
Space Shuttle program, which launched from
Kennedy Space Center,
Florida, on November 11, 1982. He was accompanied by
Vance D. Brand (spacecraft commander), Col.
Robert F. Overmyer (pilot), and Dr.
William B. Lenoir (mission specialist). STS-5, the first mission with four crewmembers, clearly demonstrated the
Space Shuttle as fully operational by the successful first deployment of two commercial communications
satellites from the Orbiter's payload bay. The mission marked the first use of the
Payload Assist Module (PAM-D), and its new ejection system. Numerous flight tests were performed throughout the mission to document Shuttle performance during launch, boost, orbit, atmospheric entry and landing phases. STS-5 was the last flight to carry the
Development Flight Instrumentation (DFI) package to support flight testing. A Getaway Special, three Student Involvement Projects, and medical experiments were included on the mission. A planned
spacewalk by Allen and Lenoir, the first of the Space Shuttle program, was postponed by one day after Lenoir became ill, and then had to be canceled when the two
spacesuits that were to be used developed problems. The STS-5 crew successfully concluded the 5-day orbital flight of
Space Shuttle Columbia with the first entry and landing through a cloud deck to a hard-surface runway and demonstrated maximum braking. STS-5 completed 81 orbits of the Earth in 122 hours before landing on a concrete runway at
Edwards Air Force Base,
California, on November 16, 1982. Allen was a mission specialist on
STS 51-A, which launched from Kennedy Space Center, Florida, on November 8, 1984. He was accompanied by Captain
Frederick (Rick) Hauck (spacecraft commander), Captain
David M. Walker (pilot), and fellow mission specialists, Dr.
Anna Lee Fisher and Commander
Dale Gardner. This was the second flight of the Orbiter
Discovery. During the mission the crew deployed two satellites, Canada's Anik D-2 (Telesat H) and Hughes' LEASAT-1 (Syncom IV-1), and operated the
3M Company's Diffusive Mixing of Organic Solutions experiment. In the first space salvage attempt in history, Allen and Gardner performed spacewalks and successfully retrieved for return to Earth the
Palapa B-2 and
Westar VI communications satellites. STS 51-A completed 127 orbits of the Earth in 192 hours before landing at Kennedy Space Center, Florida, on November 16, 1984. With the completion of this flight Allen logged a total of 314 hours in space. ==Post-NASA experience==