STS-73 (72)

Columbia (18)
Pad 39-B (34)
72nd Shuttle Mission
18th Flight OV-102


Kenneth D. Bowersox (3), Commander
Kent V. Rominger (1), Pilot
Kathryn C. Thornton (4), Payload Commander
Catherine G. Coleman Ph.D (1), Mission Specialist
Michael E. Lopez-Alegria (1), Mission Specialist
Fred W. Leslie Ph.D (1), Payload Specialist
Albert Sacco Jr Ph.D (1), Payload Specialist

David H. Matthiesen (0) Ph.D, Alternate Payload Specialist
R. Glynn Holt (0) Ph.D, Alternate Payload Specialist


OPF -- 4/14/95
VAB -- 8/21/95
PAD -- 8/28/95
TCDT -- 9/11/95
FRR -- 9/14/95



Mission Objectives:

The second United States Microgravity Laboratory (USML-2) Spacelab mission will be the prime payload on STS-73. The 16-day flight will continue a cooperative effort of the U.S. government, universities and industry to push back the frontiers of science and technology in "microgravity", the near-weightless environment of space.

Some of the experiments being carried on the USML-2 payload were suggested by the results of the first USML mission that flew aboard Columbia in 1992 during STS-50. The USML-1 mission provided new insights into theoretical models of fluid physics, the role of gravity in combustion and flame spreading, and how gravity affects the formation of semiconductor crystals. Data collected from several protein crystals grown on USML-1 have enabled scientists to determine the molecular structures of those proteins.

USML-2 builds on that foundation. Technical knowledge gained has been incorporated into the mission plan to enhance procedures and operations. Where possible, experiment teams have refined their hardware to increase scientific understanding of basic physical processes on Earth and in space, as well as to prepare for more advanced operations aboard the International Space Station and other future space programs.

USML-2 experiments include the Surface Tension Driven Convection Experiment (STDCE), the Drop Physics Module, the Drop Dynamics Experiment; the Science and Technology of Surface-Controlled Phenomena experiment; the Geophysical Fluid Flow Cell Experiment; the Crystal Growth Furnace, the Orbital Processing of High Quality Cadmium Zinc Telluride Compound Semiconductors experiment; the Study of Dopant Segregation Behavior During the Crystal Growth of Gallium Arsenide (GaAs) in Microgravity experiment; the Crystal Growth of Selected II-VI Semiconducting Alloys by Directional Solidification experiment; the Vapor Transport Crystal Growth of Mercury Cadmium Tellurida in Microgravity experiment; the Zeolite Crystal Growth Furnace (ZCG), the Interface Configuration Experiment (ICE), the Oscillatory Thermocapillary Flow Experiment; the Fiber Supported Droplet Combustion Experiment; the Particle Dispersion Experiment; the Single-Locker Protein Crystal Growth experiment; (including the Protein Crystallization Apparatus for Microgravity (PCAM) and the Diffusion-controlled Crystallization Apparatus for Microgravity (DCAM)). the Crystal Growth by Liquid-Liquid Diffusion, the Commercial Protein Crystal Growth experiment; the Advanced Protein Crystallization Facility, Crystallization of Apocrystacyanin C experiment; Crystal Structure Analysis of the Bacteriophage Lamda Lysozyme, Crystallization of RNA Molecules Under Microgravity Conditions experiment; Crystallization of the Protein Grb2 and Triclinic Lysozyme experiment; Microgravity Crystallization of Thermophilic Aspartyl-tRNA Synthetase and Thaumatin experiment; Crystallization in a Microgravity Environment of CcdB experiment; A Multivariate Analysis of X-ray Diffraction Data Obtained from Glutathione S Transferase experiment; Protein Crystal Growth: Light-driven Charge Translocation Through Bacteriorhodopsin experiment; Crystallization of Ribosome experiment; Crystallization of Sulfolobus Solfataricus Alcohol Dehydrogenase experiment; Crystallization of Turnip Yellow Mosaic Virus, Tomato Aspermy Virus, Satellite Panicum Mosaic Virus, Canavalin, Beef Liver Catalase, Concanavalin B experiment; Crystallization of the Epidermal Growth Factor (EGF); Structure of the Membrane-Embedded Protein Complex Photosystem I; Crystallization of Visual Pigment Rhodopsin; Commercial Generic Bioprocessing Apparatus; Astroculture Facility and Experiment. Spacelab Glovebox Facility experiments include the Zeolite Crystal Growth Glovebox, Protein Crystal Growth Glovebox and the Colloidal Disorder-Order Transitions,

USML-2 flight controllers and experiment scientists will direct science activities from NASA's Spacelab Mission Operations Control facility at the Marshall Space Flight Center. In addition, science teams at several NASA centers and universities will monitor and support operations of a number of experiments.

Other payloads on board include the Orbital Acceleration Research Experiment (OARE), Space Acceleration Measurement System (SAMS), Three Dimensional Microgravity Accelerometer (3DMA), Suppression of Transient Accelerations By Levitation Evaluation (STABLE) and the High-Packed Digital Television Technical Demonstration system.


Friday, October 20, 1995 at 9:53:00 a.m. EDT. Launch window was 2 hours 30 min. The countdown cloc> picked up at 7:30pm at the T-11 hour mark with a scheduled T-0 at 9:50 a.m. Loading of fuel was completed at 3:53am. The crew suited up at 6:00am and traveled out to Launch Pad LC-39B.

At the post-launch press conference, Jim Harrington, Director of Shuttle Operations mentioned the launch countdown went relatively smoothly. At the beginning of the count there was a problem with one of 3 redundant sensors on Liquid Oxygen (LOX) portion of the External Tank toggling from wet to dry. The sensor was bypassed. After tanking, one of the relief valves in the LOX storage area had a slow leak internally that will be fixed during ground operations. There was also a fire alarm that went off accidently at the 155ft level during the later part of the count while the close out crew was still on the pad. No fire was detected. Also, a right hand mid joint heater trimmed down and thelaunch team switched over to the backup system. Finally, the range command destruct system lost communications between the ROCC and the antenna. A contingency plan was work and the count was picked back up.
The launch scheduled for October 15 10:46 a.m EDT was scrubbed at 1:25pm EDT due to weather conditions at KSC that were unacceptabledue for launch. Due to the scheduled launch of the Atlas launch vehicle on Tuesday morning (10/17/95), the next available time frame in which Columbia could have been launched was Thursday, Oct. 19 at 9:49 a.m. EDT. Bad weather delayed the Atlas launch which slipped the launch of Columbia till Friday. The launch window extended until 12:19 p.m. that day. Fueling operations had started around 1:20 a.m. EDT with the loading of 1/2 million gallons of liquid hydrogen and liquid oxygen into the External Tank and were completed at 4:03am. Since the available launch period extended to 1:35 p.m. EDT based on the Transoceanic Abort Landing ( TAL) lighting conditions at Ben Guerir, Morocco the crew was boarded one hour later than planned to provide a increased opportunity for favorable weather towards the end of the launch window. They departed the Operations and Checkout Building (O&C) at 7:20am EDT.

On 10/14/95, the Mission Management Team closed the two open issues with flight hardware which caused a one day postponement of the launch of Columbia on Mission STS-73. The issue with a duct on the main engines was resolved by technicians taking ultrasonic measurements of the duct to verify adequate wall thickness. That work along with additional data analysis have allowed engine managers to conclude that there are 3 good SSMEs on Columbia. The issue with a General Purpose Computer (GPC) was resolved by removing and replacing the suspect unit. The new GPC installed in Columbia has been tested and approved for flight support.

On 10/13/95, NASA managers postponed the launch of Space Shuttle Columbia on Mission STS-73 to 10/15/95 in order to work an issue with the Space Shuttle Main Engine (SSME) and another with the orbiter's onboard computer (GPC). The issue with the Shuttle main engines involves inspection work that is required because of a crack found in a high pressure oxidizer duct on a main engine (SSME SN# 2015) being tested at the Stennis Space Center in Bay St. Louis, Mississippi on 10/11/95. Inspection of the failed duct indicates the crack happened in a weld area and was due to the duct wall being too thin. The work on Columbia involves ultrasonic inspection of the welds on each engine's high pressure oxidizer duct to ensure proper wall thickness. There are seven different welds on each engine duct.

A separate issue was worked by the launch team with one of Columbia's General Purpose Computers (GPC). During prelaunch testing, the ground crew noticed an unusual response in the data transmission between the GPC and associated electronics hardware.

The launch scheduled for Saturday, 10/7/95 at 9:41am EDT was scrubbed at 10:05am EDT (T-minus 20 minute mark ) by KSC Launch Director Jim Harrington and the Mission Management Team due to a problem with one of Columbia's two Master Events Controllers (MEC). The MECs control all critical functions that occur on the Shuttle at T-0 and through flight, including routing commands from the Shuttle s onboard computers to fire the explosive bolts that hold the solid rocket boosters to the Mobile Launch Platform (MLP) and the pyrotechnics that separate the boosters from the external tank during flight.

The countdown had started and proceeded with little difficulty. During tanking operations, the only minor problem was an overvoltage failure of a ground pump (Primary Pump 126). Tanking was picked up using the backup pump 127 and the count proceeded normally. The flight crew had departed the Operations and Checkout Building for Pad 39-B at 6:25am EDT and was onboard Columbia. At 8:56am (T-minus 29 minute mark), the launch team called a Launch Commit Criteria violation due to a failed self test on B-Core (Port 1, bit 5) of Columbia's Master Events Controller #1. The four cores are all redundant allowing the Shuttle quad-redundancy. Launch commit criteria rules require all four cores to be operating properly for safe flight. The launch countdown was placed on hold at the T-minus 20 minute mark while commands were issued to determine if the problem was with the controller or with instrumentation. It was determined the problem was with the controller which will need to be replaced.

At this time, the external tank will be drained and purged, the Rotating Service Structure (RSS) moved back around the vehicle and preparations made to gain access to the aft engine compartment to remove and replace the MEC. The MEC is scheduled to be removed on Monday 10/9/95 and the replacement MEC tested on Tuesday 10/10/95. Some of the experiments in the USML-2 spacelab module must be serviced before another launch attempt can be made and the onboard cryogenic tanks must be off-loaded and then re-loaded with liquid hydrogen and liquid oxygen reactants.

The launch on 10/6/95 was scrubbed at 3:33am for a minimum of 24 hours due to a problem in the orbiters #1 hydraulic system which services Columbia's nose wheel steering system. On 10/6/95, during pre-launch checkout, engineers noticed a problem with the volume of hydraulic fluid in the system. They will cycle the hydraulic system's fill and dump valve and run a compressibility test.

The launch scheduled for 10/5/95 was posponed 24 hours due to bad weather from Hurricane Opal. The launch attempt of Columbia on September 28, 1995 at 9:35 a.m was scrubbed due to indications of a hydrogen leak in Space Shuttle Main Engine (SSME) #1 (SN#-2037) . The scrub was called at 4 a.m. on 9/28/95. The hydrogen main fuel valve needed to be replaced which delayed the launch approximately one week.

During the launch postponement press conference, Jim Harrington, KSC Launch Director and John Plowden, Rocketdyne Site Director reported that Tanking operations had begun approximately an hour later than planned primarily due to lightning in the area of the launch pad. Liquid hydrogen was in recirculation for about 30 minutes and the main fuel valve had begun to chill down. When it reached the temperature of -10F degrees the valve started to leak. Tanking operations were stopped when the temperature on the valve reached the Launch Commit Criteria cuttoff limit of -250F degrees at the downstream side of the valve. Normal temperature on the valve runs at -100F to -150F degrees.

This would have been the first launch of < A HREF = "sts-mps.html#sts-mps-ssme">SSME engine SN#-2037 and the failed valve but it had been thru 7 static firings during ground tests. The engine and valve were last tested at cryogenic temperatures during hot firing June 15, 1995 at Stennis Space Center in Mississippi. A failure of this nature has occured only once before during the STS-2 tanking test. That failure was due to metallic contamination in the downstream seal of the valve. The valve is accessable via the AFT engine compartment. It weighs about 75 pounds with a flow path of 2.5 inches. It will be replaced at the pad. The bad valve will be sent back to the Rocketdyne factory in California for testing.

The launch countdown had begun at 4am on Monday, September 25, 1995 and the crew arrived at the KSC Shuttle Landing Facility (SLF) at 8:20 a.m.

RTV backfilling for both solid rocket boosters of Space Shuttle Columbia was performed on 9/5/95. Earlier, on 8/8/95, engineering analysis indicated that the No. 2 main engine on Columbia was unacceptable for flight and was removed and replaced with an engine originally slated to fly on mission STS-74. The replacement engine does not have a block one liquid oxygen pump.


Altitude: 150 nm (172 statute miles)
Inclination: 39.0 degrees
Orbits: 255
Duration: 15 days, 21 hours, 53 minutes, 16 seconds.
Distance: 6.6 million miles


SRB: BI-075
ET : SN-73
SSME-1: SN-2037
SSME-2: SN-2031
SSME-3: SN-2038


November 5, 1995 at 6:45:21am EST at KSC Runway 33. Main gear touchdown at 6:45:21 EST (MET 15days 21hr 52min 21sec). Nose gear touchdown at 6:45:35 EST (MET 15days 21hr 52min 35sec). Wheels stop at 6:46:16 EST (MET 15days 21hr 53min 16sec).

Two landing opportunities were possible for a landing on 11/5/95.. Columbia took the first opportunity which began with a deorbit engine firing by Columbia at 5:46 a.m. EST, on the mission's 255th orbit, leading to a touchdown at the Kennedy Space 6:45 a.m. EST. The second opportunity would have begun with a deorbit burn at 7:20 a.m. EST on orbit 256 leading to a 8:19 a.m. EST touchdown. Mission duration was 17hours short of the existing shuttle record set by Endeavour.

Mission Highlights:

The seven-member crew will work in two 12-hour shifts, for 16 days conducting 14 major experiments and a variety of other medical and engineering investigations. The experiments are part of the planned operations of the United States Microgravity Laboratory 2 payload.

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