STS-51 (57)

DISCOVERY (17)

Pad 39-B (26)

57th Shuttle Mission

14th Flight OV-103

KSC landing (17)

6th Night Landing

1st KSC Night Landing

RSLS Abort after SSME Ignition (4)

Crew:

Frank L. Culbertson Jr.(2), Commander

William F. Readdy (2), Pilot

James H. Newman Ph.D.(1), Mission Specialist 1

Daniel W. Bursch (1), Mission Specialist 2

Carl E. Walz (1), Mission Specialist 3

Milestones:

OPF -- 4/18/93

VAB -- 6/18/93

PAD -- 6/26/93

Payload:

ACTS-TOS, ORFEUS-SPAS, IMAX, CPCG-II, CHROMEX-04, HRSGS-A, APE-E, IPMP, RME-III, AMOS

Mission Objectives:

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Launch:

September 12, 1993, 7:45 a.m. EDT. Officials decided to scrub Discovery's mission Saturday, July 17, at about 8:52 a.m. EDT because all eight of the solid rocket booster hold down bolts and the T-0 liquid hydrogen vent arm, located on the side of the external tank, were prematurely charged with current. This charge is normally initiated at the T-18 second mark in the countdown. The problem circuit card in the pyrotechnic initiator controller (PIC) which caused the launch scrub on Saturday has been replaced on the mobile launcher platform. Efforts to duplicate the problem on the suspect card were successful at KSC's malfunction laboratory. A thermally unstable circuit was the culprit. The problem was narrowed down to a prematurely charged capacitor in the firing circuit of all eight Solid Rocket Booster hold down posts and the T-0 liquid hydrogen vent arm, located on the side of the external tank.

Launch was delayed on Saturday, 7/24/93 due to a problem with the right hand Solid Rocket Booster (SRB). The Ground Launch Sequencer detected an unacceptably slow speed rate of a hydraulic power unit located inside the Shuttle's righthand solid rocket booster. The Hydraulic Power Unit (HPU) was replaced and retested.

Launch was again delayed until 9:10 am EDT on August 12 due to concerns about the Perseid meteor shower which is expected to peak on the evening of August 11. The Perseid event, which happens each August, is one of about a dozen such occasions each year that are the result of a comet's nucleus shedding debris along its orbital path as it approaches the Sun. When Earth's orbit passes through the debris field it causes meteor showers activity or "shooting stars." The concern with the Perseid event was that the activity is expected to be extremely heavy this year and thus there was an increased chance that a spacecraft in Earth orbit could be damaged by a piece of the debris.

Launch on 8/12/93 was scrubbed at the T-3 second mark following a Redundant Set Launch Sequencer (RSLS) abort. The cause for the RSLS abort was a faulty sensor that monitors fuel flow through main engine #2. Engine cutoff occurred at 9:12:32 a.m. EDT. There are two sensors which are part of the flow meter that monitor the flow of hydrogen through the main engine. Each sensor has a Channel A and Channel B for a total of four readings. These sensors are monitoring the fuel flow from main engine ignition through main engine cutoff.

The sensors are redundant so that all four channels must report an acceptable fuel flow rate prior to liftoff. Data indicates that Channel A on the number two sensor failed. There was no electrical output at all from this sensor while the others were found to have operated normally. A completely redundant set of measurements is required to commit to flight. All three of Discovery's main engines were removed and replaced with a set from Endeavour at the Pad. Tests conducted under cryogenic conditions were successful in duplicating the sensor failure that caused the launch scrub.

On Sept 9, the pickup of the launch count was delayed pending the outcome of the ACTS Independent Review Team. This team met to review the design of the ACTS spacecraft in light of the recent loss of of contact with the Mars Observer spacecraft and the failure of the NOAA-13 weather satellite. All three spacecraft are manufactured by Martin Marietta. TOS contains two transistors manufactured in the same manner as those made by Unitrode that are suspected in the failure of Mars Observer.Launch occured September 12, 1993, 7:45 a.m. EDT. Payload Weight up: 42,682 lbs.

Orbit:

Altitude: 160nm

Inclination: 28.45 degrees

Orbits: 157

Duration: 9 days, 20 hours, 11 minutes, 11 seconds.

Distance: 4,106,411 miles

Hardware:

(Flow-A)

SRB:

ET :

MLP :

SSME-1: SN-2030

SSME-2: SN-2033

SSME-3: SN-2032 (Flow-B)

SRB: BI-060

SRM: 360W/L033

ET : 59

MLP : 3

SSME-1: SN-2031

SSME-2: SN-2034

SSME-3: SN-2029

Landing:

Both landing opportunities to the Kennedy Space Center.in Florida on September 21, 1993 were passed up due to clouds and rain in the vicinity so Discovery and its five-member crew were told to stay in space an additional day. The shuttle landed on September 22, 1993, 3:56 am EDT on KSC SLF runway 15. This was the first nighttime Shuttle Landing at KSC. Preliminary measurements show the orbiter touched down about 2,150 feet from the runway 15 threshold. After landing, plumes were visible from teh venting of APU's 1 and 2. Rollout distance was about 8,350 feet. The vehicle was towed from the SLF beginning at about 7:30 a.m. and was in OPF bay 3 at about 8:40 a.m. Payload Weight down: 8,567lbs. Orbiter Landing Weight: 206,438 lbs.

Mission Highlights:

The Advanced Communications Technology Satellite (ACTS) was deployed. This satellite will serve as a test bed for advanced experimental communications satellite concepts and technology. Its Transfer Orbit Stage (TOS) upper stage fired on time 45 minutes later and boosted the satellite to geosynchronous altitude on the first day of the mission.

The first attempt to deploy ACTS was delayed by the crew when two-way communications were lost with Mission Control about 30 minutes before the deploy time. Flight controllers could receive telemetry and voice communications from Discovery, however the crew could not receive communications from the ground. The crew waived off the 2:43 p.m. CDT deploy when they did not receive a "go" from Mission Control as called for in preflight plans made for just such an occurrence.

After the waive off of deploy, the crew changed the shuttle's S-Band communications system to a lower frequency and restored two-way communications with the ground. The two-way communications had been lost for a total of about 45 minutes. After consulting the crew, flight controllers began immediately planning for the second, and ultimately successfull deploy.

Another payload on this mission was the Orbiting Retrievable Far and Extreme Ultraviolet Spectrometer (ORFEUS) telescope mounted on the Shuttle Pallet Satellite (SPAS) payload carrier. ORFEUS was designed to provide information on how stars are born and how they die, while studying gaseous interstellar clouds. Also in the cargo bay was the Limited Duration Space Environment Candidate Materials Exposure (LDCE) experiment.

During the deployment on September 12 of the Advanced Communications Technology Satellite (ACTS) and its Transfer Orbit Stage (TOS) booster, two Super*Zip explosive cords, one primary and the other a backup simulataneously detonated. This caused minor tears in two dozen insulation blankets mounted on the bulkhead between the payload bay and the AFT near the #3 APU.

On Thursday, September 16, 1993, spacewalkers Jim Newman and Carl Walz performed a spacewalk designed to evaluate tools, tethers and a foot restraint platform. Their findings reassured the designers and planners of the Hubble Space Telescope servicing flight that their preparations are sound.

The new equipment designed for the extensive spacewalk work that will be required on the December telescope servicing mission was only part of the goal of today's spacewalk, and Newman and Walz fulfilled the other goals as they explained at length to Mission Control the differences they perceived between work in orbit and ground training. The two EVA crewmen were ahead of schedule much of the day, and completed more tasks than originally planned for the spacewalk.

However, as they were cleaning up, a balky tool box lid slowed them down when they had to pry it free and close it for Discovery's trip home. The toolbox lid stretched the spacewalk by about 45 minutes over what had been planned, with Newman and Walz logging a total seven hours, five minutes and 28 seconds of spacewalk time.

Other in-cabin payloads included the Air Force Maui Optical Site (AMOS) Auroral Photography Experiment-B (APE-E), Commercial Protein Crystal Growth (CPCG), Chromosome and Plant Cell Division in Space (CHROMEX), High Resolution Shuttle Glow Spectroscopy-A (HRSGS-A), IMAX, Investigations into Polymer Membrane Processing (IPMP) and the Radiation Monitoring Equipment-III (RME-III) experiment. The Investigation into Polymer Membrane Processing, or IPMP, is designed to research the mixing of various solvent systems in the absence of convection found on Earth in hopes of controlling the porosity of various polymer membranes. RME measures gamma ray, electron, neutron and proton radiation levels in the crew cabin throughout the flight.

Onboard, Mission Specialist Jim Newman donned a special visor to perform a medical experiment testing vision in weightlessness as part of investigations into how vision compensates for the inner ear's lack of balance in space. Newman also successfully tested a Global Positioning System receiver flying aboard Discovery as an evaluation of using such equipment to supplement the shuttle's navigation. Also, in a precursor of space station operations, one of Discovery's fuel cells was turned off and restarted.

In another medical evaluation, Commander Frank Culbertson and Mission Specilaist Dan Bursch rode a stationary bike on Discovery's lower deck as part of a continuing study of using exercse to counteract the effects of weightlessness on the body. The crew also powered up an experiment that looks at improving membrane filters in weightlessness and checked on another experiment that has been running well studying the effects of microgravity on plant cells.

Astronauts Carl Walz and Jim Newman operate the experiments designed to study the glowing effect, one a spectrometer that records the effect on film in fine detail and another that records the effect on still photographs. The experiments are hoped to provide information about just what types of gasses -- in addition to atomic oxygen -- create the glow. The information on kinds of gasses in the extreme reaches of the atmosphere may be coupled with the materials exposure experiment in the cargo bay to assist with the design and construction of future spacecraft.

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