STS-51-F
STS-51-F, also known as Spacelab 2, was the nineteenth flight of NASA's Space Shuttle program and the eighth mission for the orbiter Challenger. Launched on July 29, 1985, at 5:00 p.m. EDT from Launch Pad 39A at Kennedy Space Center in Florida, the mission carried a crew of seven astronauts to deploy the European-built Spacelab 2 module in the payload bay for a series of multidisciplinary scientific experiments focused on astronomy, astrophysics, plasma physics, atmospheric science, solar physics, and life sciences.[1] It is historically notable as the only Space Shuttle mission to execute an abort-to-orbit (ATO) procedure following a premature shutdown of one main engine during ascent, yet the crew successfully adapted and accomplished most primary objectives during the 7-day, 22-hour, 45-minute, and 26-second flight, which concluded with a landing at Edwards Air Force Base in California on August 6, 1985, at 12:45 p.m. PDT.[1][2] The crew was commanded by veteran astronaut C. Gordon Fullerton, with Roy D. Bridges Jr. serving as pilot; mission specialists included F. Story Musgrave, Karl G. Henize, and Anthony W. England, while payload specialists Loren W. Acton (from Lockheed Palo Alto Research Laboratories) and John-David F. Bartoe (from the U.S. Air Force) oversaw the Spacelab operations.[1] This was a dedicated Spacelab mission and the first to operate on a two-shift, around-the-clock schedule, utilizing three instrument-pointing pallets configured for observations outside the Earth's atmosphere, including ultraviolet and X-ray astronomy of celestial objects.[2] Key experiments verified Spacelab-2 systems performance, measured the spacecraft environment, and advanced understanding of solar magnetic fields, plasma behaviors, and biological adaptations in microgravity, despite challenges like the need for in-flight software adjustments to the Instrument Pointing System.[1][2] The mission's defining incident occurred approximately 5 minutes and 43 seconds after liftoff, when a faulty temperature sensor on the number-one main engine triggered its shutdown, reducing thrust and necessitating the ATO to achieve a lower-than-planned initial orbit of 108 by 143 nautical miles using the remaining two engines and an additional burn of approximately 4,400 pounds of propellant from the Orbital Maneuvering System (OMS).[2][3] Ground teams rapidly replanned the timeline to accommodate the lower orbit, enabling the crew to conduct 13 major experiments that yielded valuable data on infrared radiation, atmospheric plasma, and even a lighthearted comparison of carbonated beverages in space (the "Cola Wars" test).[2] Overall, STS-51-F demonstrated the Shuttle program's resilience and advanced international collaboration in space-based research, paving the way for future astronomical observations from orbit.[1][2]Mission Background
Designation and Objectives
STS-51-F was the 19th flight of NASA's Space Shuttle program and the eighth flight for the orbiter Challenger, designated as part of the Spacelab long-duration mission series to support multidisciplinary scientific research in low Earth orbit.[1] The mission, also known as Spacelab 2, utilized a pallet-only configuration of the European Space Agency's Spacelab facility to accommodate experiments requiring precise pointing and space exposure.[3] The primary objectives centered on verifying the performance of Spacelab systems integrated with the orbiter, measuring the induced space environment, and conducting experiments across astronomy, plasma physics, life sciences, high-energy astrophysics, solar physics, and atmospheric physics.[1] Key goals included the inaugural flight test of the Instrument Pointing System (IPS), a three-axis stabilized platform developed by the European Space Agency for sub-arcsecond pointing accuracy to support astronomical observations.[4] Another critical element was the deployment and retrieval of the Plasma Diagnostics Package (PDP), which investigated plasma interactions with the orbiter and shuttle bay environment during free-flight operations.[3] The mission was planned for 7 days to allow comprehensive data collection from these unique experiments.[1] Secondary objectives encompassed middeck experiments to explore microgravity effects, such as the Carbonated Beverage Dispenser Evaluation (CBDE), which tested the packaging and dispensing of carbonated beverages to assess fluid behavior and crew consumption in weightlessness.[5] Despite an in-flight abort-to-orbit that reduced the achievable altitude, most primary and secondary objectives were successfully met, though some astronomical experiments were impacted by the lower orbit, with the mission concluding after 7 days, 22 hours, 45 minutes, and 26 seconds.[3]Historical Context
STS-51-F, designated as the Spacelab 2 mission, marked the third dedicated flight of the Spacelab laboratory chronologically, following STS-9 in 1983 and STS-51-B earlier in 1985, underscoring NASA's commitment to advancing microgravity research through international partnerships with the European Space Agency (ESA), which developed the reusable Spacelab components.[6] This mission built on the foundational Spacelab operations established during STS-9 in 1983 and the life sciences focus of STS-51-B, emphasizing astrophysics, plasma physics, and technology demonstrations to expand the shuttle's role as a versatile orbital platform. The mission's astronomical experiments also served as a precursor to Hubble Space Telescope operations, testing key observation techniques from orbit.[1] Originally targeted for launch on July 12, 1985, STS-51-F faced delays due to technical challenges with the Instrument Pointing System required for the unpressurized pallet configuration, which necessitated extensive ground testing and integration adjustments.[6] These issues, combined with scheduling constraints in the shuttle manifest, pushed the mission to July, occurring approximately 84 days after Challenger's return from STS-51-B on May 6, 1985—a relatively rapid turnaround that highlighted the orbiter's increasing operational reliability.[7] The program had matured significantly since STS-41-C in April 1984, when Challenger successfully performed the first in-orbit satellite repair, boosting confidence in extended shuttle capabilities for complex payloads like Spacelab. A distinctive feature of STS-51-F was its implementation of dual crew shifts—Red and Blue teams—enabling around-the-clock science operations for the first time, which addressed the operational constraints of shorter prior missions and maximized the seven-day flight's productivity despite an in-flight Abort to Orbit.[2] Pre-launch preparations were further impacted by external factors, including weather considerations that influenced the final launch window selection on July 29, 1985, after a July 12 pad abort due to a coolant valve malfunction.[7]Crew
Composition and Roles
The STS-51-F crew consisted of seven members, including a commander, pilot, three mission specialists, and two payload specialists, selected for their expertise in piloting, engineering, science, and astrophysics to support the Spacelab 2 mission objectives.[1][8] Commander C. Gordon Fullerton, aged 48 and a Colonel in the U.S. Air Force, was a veteran NASA astronaut since 1969 with a background in mechanical engineering from the California Institute of Technology and extensive experience as an Air Force test pilot. He had previously served as pilot on STS-3, accumulating 192 hours in space, and was responsible for overall mission command and flight operations.[8][9] Pilot Roy D. Bridges Jr., aged 42 and also a Colonel in the U.S. Air Force, was on his first spaceflight; he held degrees from the U.S. Air Force Academy and Purdue University, with a career as a fighter and test pilot since joining NASA in 1980. Bridges assisted Fullerton in spacecraft piloting, navigation, and rendezvous operations.[8] Mission Specialist Karl G. Henize, aged 58 and holding a Ph.D. in astronomy from the University of Michigan, was a NASA scientist-astronaut selected in 1967 with prior support roles on Apollo and Skylab missions; he had over 1,900 hours of flying time. Henize, an astronomer, managed Spacelab systems and conducted astronomical observations.[8] Mission Specialist F. Story Musgrave, aged 49 and an M.D. with degrees in mathematics and chemistry, was a veteran of STS-6 with more than 13,200 hours of flying experience; he served as flight engineer, overseeing Spacelab systems and supporting experiment operations.[8] Mission Specialist Anthony W. England, aged 43 and holding a Ph.D. in geophysics from MIT, specialized in Earth and planetary sciences with over 2,000 hours of flying time; he focused on conducting experiments such as the Infrared Imaging System (IRT) and other geophysical payloads.[8] Payload Specialist Loren W. Acton, aged 49 and a Ph.D. in solar physics from the University of Colorado, from Lockheed Palo Alto Research Laboratories, as a payload specialist for the Spacelab 2 mission; as a scientist and co-investigator for the Solar Optical Universal Polarimeter (SOUP), he was responsible for solar observation experiments aboard Spacelab 2.[8][10] Payload Specialist John-David F. Bartoe, aged 40 and holding a Ph.D. in physics from Georgetown University, was an astrophysicist from the Naval Research Laboratory and co-investigator for the High-Resolution Telescope/Spectrograph (HRTS) and Solar Ultraviolet Spectral Irradiance Monitor (SUSIM); he handled astrophysics experiments and payload operations.[8] Fullerton and Bridges primarily managed flight operations from the forward flight deck, while Henize and Musgrave oversaw Spacelab module systems and integration. England, Bartoe, and Acton concentrated on executing scientific experiments, including the IRT for infrared mapping and IPS (Instrument Pointing System) for precise observations.[8] Crew seating assignments for launch and entry positioned Fullerton in seat 1 (commander, forward left), Bridges in seat 2 (pilot, forward right), Henize in seat 3 (mission specialist, aft left), Musgrave in seat 4 (mission specialist, aft right), England in seat 5 (middeck forward left), Acton in seat 6 (middeck forward right), and Bartoe in seat 7 (middeck aft).[11]| Seat | Position | Crew Member | Role |
|---|---|---|---|
| 1 | Forward Left (Commander) | C. Gordon Fullerton | Commander |
| 2 | Forward Right (Pilot) | Roy D. Bridges Jr. | Pilot |
| 3 | Aft Left (MS) | Karl G. Henize | Mission Specialist |
| 4 | Aft Right (MS) | F. Story Musgrave | Mission Specialist |
| 5 | Middeck Forward Left | Anthony W. England | Mission Specialist |
| 6 | Middeck Forward Right | Loren W. Acton | Payload Specialist |
| 7 | Middeck Aft | John-David F. Bartoe | Payload Specialist |