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Mission or Study ID:   STS-41
Shuttle Program
Launch/Start Date:
Landing/End Date:
4 days
STS-41 Crew Patch

Space Shuttle Discovery (STS-41) launched on October 6, 1990, carrying the heaviest payload to date with a launch weight of 259,593 pounds. The five member crew included Commander Richard N. Richards, Pilot Robert D. Cabana and Mission Specialists William M. Shepard, Bruce E. Melnick and Thomas D. Akers.

The primary payload on STS-41 was the European Space Agency (ESA) built Ulysses spacecraft, created to explore the polar regions of the Sun. Two upper stages, the Inertial Upper Stage (IUS) and a mission-specific Payload Assist Module-S (PAM-S), combined together for the first time to send Ulysses toward out-of eliptic trajectory.

STS-41 was the second flight of the Chromosome and Plant Cell Division Experiment (CHROMEX-02). CHROMEX payloads fly in the middeck of the Shuttle and consist of experiments using the Plant Growth Unit (PGU), which allowed scientists to grow whole plants on orbit. The plants grew for the length of the mission and were analyzed postflight to determine the effects of microgravity and space flight on their chromosomes and mitotic structures. Little to no crew interaction with the payload was required.

The Physiological Systems Experiment (PSE) was also flown on STS-41. The objective of this experiment was to test the hypothesis that a growth-hormone-deficient state contributes to bone loss and decreased function of specific tissues in microgravity. The investigators expected that replacement with recombinant growth hormone would retard these changes in the presence of adequate nutrition and exercise. PSE was designed by Genentech, Inc., in San Francisco, California, and sponsored by the Center for Cell Research at Pennsylvania State University, one of NASA's 16 centers for the Commercial Development of Space. The venture between the three groups resulted in the first commercial space research project in the life sciences.

Multiple Detailed Supplementary Objectives (DSOs) were also performed during this mission. A DSO is a NASA-sponsored investigation performed by Space Shuttle crewmembers, who serve as the test subjects. These studies required minimal crew time, power and stowage. Biomedical DSOs focus on operational concerns, including space motion sickness, cardiovascular deconditioning, muscle loss, changes in coordination and balance strategies, radiation exposure, pharmacokinetics and changes in the body's biochemistry.

Other payloads and experiments flown on STS-41 included the Shuttle Solar Backscatter Ultraviolet (SSBUV) experiment; INTELSAT Solar Array Coupon (ISAC); Voice Command System (VCS); Solid Surface Combustion Experiment (SSCE); Investigations into Polymer Membrane Processing (IPMP); Radiation Monitoring Experiment III (RME-III); Shuttle Student Involvement Program (SSIP); and Air Force Maui Optical Site (AMOS) experiment.

STS-41 landed on October 10, 1990, at Edwards Air Force Base in California.

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