Processing When taking a road trip, it is important to plan ahead by making sure your vehicle is prepared for the journey. A typical road trip on Earth can be the Shuttle for routine and simple. The roadways are already properly paved, service Flight stations are available if vehicle repairs are needed, and food, lodging, and stores for other supplies can also be found. The same, however, could not be said for a trip into space. The difficulties associated with Steven Sullivan space travel are complex compared with those we face when traveling here. Preparing the Shuttle for Flight Food, lodging, supplies, and repair equipment must be provided for within Ground Processing the space vehicle. Jennifer Hall Peter Nickolenko Vehicle preparation required a large amount of effort to restore the shuttle Jorge Rivera to nearly new condition each time it flew. Since it was a reusable vehicle Edith Stull Steven Sullivan with high technical performance requirements, processing involved a Space Operations Weather tremendous amount of “hands-on” labor; no simple tune-up here. Not only Francis Merceret was the shuttle’s exterior checked and repaired for its next flight, all Robert Scully components and systems within the vehicle were individually inspected and Terri Herst verified to be functioning correctly. This much detail work was necessary Steven Sullivan because a successful flight was dependent on proper vehicle assembly. Robert Youngquist During a launch attempt, decisions were made within milliseconds by equipment and systems that had to perform accurately the first time—there was no room for hesitation or error. It has been said that a million things have to go right for the launch, mission, and landing to be a success, but it can take only one thing to go wrong for them to become a failure.

In addition to technical problems that could plague missions, weather conditions also significantly affected launch or landing attempts. Unlike our car, which can continue its road trip in cloudy, windy, rainy, or cold weather conditions, shuttle launch and landing attempts were restricted to occur only during optimal weather conditions. As a result, weather conditions often caused launch delays or postponed landings.

Space Shuttle launches were a national effort. During the lengthy processing procedures for each launch, a dedicated workforce of support staff, technicians, inspectors, engineers, and managers from across the nation at multiple government centers had to pull together to ensure a safe flight. The whole NASA team performed in unison during shuttle processing, with pride and dedication to its work, to make certain the success of each mission.

74 The Space Shuttle and Its Operations Preparing the the demands of the largest and most The initial six operational missions were complex reusable space vehicle. scheduled to land at DFRC/Edwards Shuttle for Flight Air Force Base because of the safety The end of a mission set in motion margins available on the lakebed a 4- to 5-month process that included Ground Processing runways. Wet lakebed conditions more than 750,000 work hours and diverted one of those landings—Space Imagine embarking on a one-of-a-kind, literally millions of processing steps to Transportation System (ST S)- 3 (1 982)— once-in-a-lifetime trip. Everything prepare the shuttle for the next flight. to . STS-7 must be exactly right. Every flight of (1 983) was the first mission scheduled to the Space Shuttle was just that way. Landing land at KSC, but it was diverted to A successful mission hinged on ground During each mission, NASA runways due operations planning and execution. designated several landing sites— to unfavorable weather. The Ground operations was the term used to three in the Continental , 10th shuttle flight—STS-41B (1 984)— describe the work required to process three overseas contingency or was the first to land at KSC. the shuttle for each flight. It included transatlanic abort landing sites, and landing-to-launch processing—called a various emergency landing sites Landing Systems “flow”—of the Orbiter, payloads, Solid located in the shuttle’s orbital flight Similar to a conventional airport, the Boosters (SRBs), and External path. All of these sites had one thing in KSC used visual Tank (ET). It also involved many common: the commander got one and electronic landing aids both on important ground systems. Three chance to make the runway. The the ground and in the Orbiter to help missions could be processed at one time, Orbiter dropped like a rock and there direct the landing. Unlike conventional all at various stages in the flow. Each were no second chances. If the target aircraft, the Orbiter had to land perfectly stage had to meet critical milestones or was missed, the result was disaster. the first time since it lacked propulsion throw the entire flow into a tailspin. (KSC) in Florida and landed in a high-speed glide at Each shuttle mission was unique. and Dryden Flight Research Center 343 to 364 km/hr ( 21 3 to 226 mph). The planning process involved creating (DFRC)/Edwards Air Force Base in Following shuttle landing, a convoy a detailed set of mission guidelines, California were the primary landing of some 25 specially designed vehicles writing reference materials and manuals, sites for the entire Space Shuttle or units and a team of about 150 trained developing flight software, generating Program. White Sands Space Harbor in personnel converged on the runway. a flight plan, managing configuration New Mexico was the primary shuttle The team conducted safety checks for control, and conducting simulation pilot training site and a tertiary landing explosive or toxic gases, assisted the and testing. Engineers became masters site in case of unacceptable weather crew in leaving the Orbiter, and at using existing technology, systems, conditions at the other locations. prepared the Orbiter for towing to the and equipment in unique ways to meet Orbiter Processing Facility.

The landing-to- launch ground operations “flow” at Kennedy Space Center prepared each shuttle for its next flight. This 4- to 5-month process required thousands of work hours and millions of individual processing steps. After landing, the Orbiter is moved to the Orbiter landing, STS-129 (2009). Processing Facility.

Landing Orbiter Processing Facility: 120-130 days

The Space Shuttle and Its Operations 75 Orbiter Processing coordination and prioritization among During missions, the breadboard some 35 engineering systems and replicated flow problems and worked The Orbiter Processing Facility was 32 support groups. Schedules ranged out solutions. a sophisticated aircraft hangar (about in detail from minutes to years. 2,700 m 2 [29,000 ft 2]) with three Engineers also tested spacecraft separate buildings or bays. Trained Personnel removed the Orbital communications systems at the personnel completed more than 60% Maneuvering System pods and Forward Electronic Systems Test Laboratory, of the processing work during the modules and where multielement, crewed spacecraft approximately 125 days the vehicle modified or repaired and retested them communications systems were interfaced spent in the facility. in the Hypergolic Maintenance Facility. with relay and ground elements When workers completed modifications for end-to-end testing in a controlled Technicians drained residual fuels and and repairs, they shipped the pods and radio-frequency environment. removed remaining payload elements modules back to the Orbiter Processing or support equipment. More than 11 5 The Avionics Engineering Laboratory Facility for reinstallation. multilevel, movable access platforms supported flight system hardware and could be positioned to surround the software development and evaluation as Johnson Space Center Orbiter Orbiter and provide interior and well as informal engineering evaluation Laboratories exterior access. Engineers performed and formal configuration- extensive checkouts involving some Several laboratories at Johnson controlled verification testing of 6 million parts. NASA removed and Space Center supported Orbiter testing non-flight and flight hardware and transferred some elements to other and modifications. software. Its real-time environment facilities for servicing. The Orbiter consisted of a vehicle dynamics The Electrical Power Systems Processing Facility also contained simulation for all phases of flight, Laboratory was a state-of-the-art shops to support Orbiter processing. including contingency aborts, and a full electrical compatibility facility that complement of Orbiter data processing Tasks were divided into forward, supported shuttle and International system line replacement units. midbody, and aft sections and required Space Station (ISS) testing. The shuttle mechanical, electrical, and Thermal breadboard, a high-fidelity replica The Shuttle Avionics Integration Protection System technicians, of the shuttle electrical power Laboratory was the only program test engineers, and inspectors as well as distribution and control subsystem, facility where avionics, other flight planners and schedulers. Daily was used early in the program for hardware (or simulations), software, activities included test and checkout equipment development testing procedures, and ground support schedule meetings that required and later for ongoing payload and equipment were brought together for shuttle equipment upgrade testing. integrated verification testing.

Inside the Orbiter Processing Facility, technicians process the Space Shuttle Main Engine and install it into the Orbiter.

Orbiter Processing Facility (continued)

76 The Space Shuttle and Its Operations Kennedy Space Center Shuttle This facility established capabilities Logistics Depot for avionics and mechanical hardware ranging from wire harnesses and Technicians at the Shuttle Logistics panels to radar and communications Depot in Florida manufactured, systems, and from ducts and tubing to overhauled and repaired, and procured complex actuators, valves, and Orbiter line replacement units. The regulators. Capability included all facility was certified to service more aspects of maintenance, repair, and than 85% of the shuttle’s approximately overhaul activities. 4,000 replaceable parts. Prior to the launch of STS-119 (2009), Discovery gets boundary layer transition tile, which Kennedy Space Center Tile Processing monitors the heating effects of early re-entry Following shuttle landing, the Thermal at high Mach numbers. Protection System—about 24,000 silica tiles and about 8,000 thermal blankets—was visually inspected in the Orbiter Processing Facility. Thermal Protection System products included tiles, gap fillers, and insulation blankets to protect the Orbiter exterior from the searing heat of launch, re-entry into Earth’s atmosphere, and At the Kennedy Space Center tile shop, a worker the cold soak of space. The materials places a Boeing replacement insulation 18 tile were repaired and manufactured in the in the oven to be baked at 1,200°C (2,200°F) to cure the ceramic coating. Thermal Protection Systems Facility. Tile technicians and engineers used manufacture tile accurate to 0.00254 cm manual and automated methods to (0.00 1 in.). Tile and external blanket fabricate patterns for areas of the repair and replacement processing included: removal of damaged tile and At the Shuttle Logistics Depot, Rick Zeitler Orbiter that needed new tiles. Engineers assesses the cycling of a main propulsion fill and used the automotive industry tool preparation of the cavity; machining, drain valve after a valve anomoly during launch Optigo ™ to take measurements in tile coating, and firing the replacement tile; countdown caused a scrub. cavities. Optigo ™ used optics to record and fit-checking, waterproofing, the hundreds of data points needed to bonding, and verifying the bond.

Solid Rocket Boosters and the External Tank are delivered to Kennedy Space Center and transported to the Vehicle Assembly Building to be readied for the Space Shuttle.

Vehicle Assembly Building: 7-9 days

The Space Shuttle and Its Operations 77 Space Shuttle Main Engine called casting segments. Insulation was Technicians at the Rotation Processing Processing applied to the inside of the cases and the and Surge Facility received, inspected, propellant was bonded to this insulation. and offloaded the booster segments Trained personnel removed the from rail cars, then rotated the three reusable, high-performance, The semiliquid, solid propellant was segments from horizontal to vertical liquid-fueled main engines from the poured into casting segments and and placed them on pallets. Orbiter following each flight for cured over 4 days. Approximately forty inspection. They also checked engine 2. 7-metric-ton (3-ton) mixes of propellant Many booster electrical, mechanical, systems and performed maintenance. were required to fill each segment. thermal, and pyrotechnic subsystems Each engine had 50,000 parts, about were integrated into the flight The nozzle consisted of layers of glass- 7,000 of which were life limited and structures. The aft skirt subassembly and carbon-cloth materials bonded to periodically replaced. and forward skirt assembly were aluminum and steel structures. These processed and then integrated with the materials were wound at specified Solid Rocket Booster Processing booster aft segments. angles and then cured to form a dense, The SRBs were repaired, refurbished, homogeneous insulating material After a complete flight set of boosters and reused for future missions. The capable of withstanding temperatures was processed and staged in the surge twin boosters were the largest ever built reaching 3,300°C (6,000°F). The cured buildings, the boosters were transferred and the first designed for refurbishment components were then adhesively to the Vehicle Assembly Building for and reuse. They provided “lift” for bonded to their metal support structures stacking operations. the Orbiter to a distance of about 45 km and the metal sections were joined to (28 miles) into the atmosphere. form the complete nozzle assembly. External Tank Processing Transporting a flight set of two Solid The ET provided propellants to the Booster Refurbishment Rocket Motors to KSC required four main engines during launch. The tank Following shuttle launch, NASA major railroads, nine railcars, and 7 days. was manufactured at the Michoud recovered the spent SRBs from the Assembly Facility in New Orleans and KSC teams refurbished, assembled, Atlantic Ocean, disassembled them, and shipped to Port Canaveral in Florida. tested, and integrated many SRB transported them from Florida to ATK’s It was towed by one of NASA’s elements, including the forward and Utah facilities via specially designed SRB retrieval ships. At the port, aft skirts, separation motors, frustum, rail cars—a trip that took about 3 weeks. tugboats moved the barge upriver parachutes, and nose cap. to the KSC turn basin. There, the After refurbishment, the motor cases were prepared for casting. Each motor consisted of nine cylinders, an aft dome, and a forward dome. These elements were joined into four units

Inside the Vehicle Assembly Building, technicians complete the process of stacking the Solid Rocket Booster components.

Vehicle Assembly Building (continued)

78 The Space Shuttle and Its Operations tank was offloaded and transported to the Vehicle Assembly Building.

Payload Processing William Parsons Payload processing involved a variety of manager (2003-2005) payloads and processing requirements. and director of Kennedy Space Center The cargo integration test equipment (2007-2008). stand simulated and verified payload/cargo mechanical and functional interfaces with the “The shuttle is an Orbiter before the spacecraft was extremely complex In the firing room, William Parsons (left), director of Kennedy transported to the . Payload space system. Space Center, and Dave King, director of Marshall Space Flight Center, discuss the imminent launch of STS-124 (2008). processing began with power-on health It is surprising and status checks, functional tests, how many people and vendors touch the vehicle. At the Kennedy Space Center, computer and communications interface it is amazing to me how we are able to move a behemoth space structure, like the checks, and spacecraft command and monitor tests followed by a test to Orbiter, and mate to another structure with incredibly precise tolerances.” simulate all normal mission functions through payload deployment. Hubble Space Telescope servicing Following processing, payloads were where experiments and other payloads missions provided other challenges. installed in the Orbiter either were integrated. Sensitive telescope instruments horizontally at the Orbiter Processing required additional cleaning and ISS flight hardware was processed in Facility or vertically at the launch pad. hardware handling procedures. a three-story building that had two Payload-specific ground support processing bays, an airlock, operational Space Station Processing Facility Checkout equipment had to be installed and control rooms, laboratories, logistic monitored throughout the pad flow, All space station elements were areas, and office space. For all including launch countdown. processed, beginning with Node 1 payloads, contamination by even the in 1997. smallest particles could impair their function in the space environment. Most ISS payloads arrived at KSC by plane and were delivered to the Payloads, including the large station Space Station Processing Facility modules, were processed in this

After the External Tank is mated to the Solid Rocket Booster, the Orbiter is brought to the Vehicle Assembly Building.

Vehicle Assembly Building (continued)

The Space Shuttle and Its Operations 79 state-of-the-art, nonhazardous facility strengthened the platform deck and The 295-metric-ton (325-ton) cranes that had a nonconductive, air-bearing added an over-pressurization water lifted and positioned the Solid Rocket pallet compatible floor. This facility had deluge system. Two additional flame Motor sections, ET, and Orbiter. a Class 100K clean room that regularly trenches accommodated the SRB The 227-metric-ton (250-ton) cranes operated in the 20K range. Class 100K exhaust. Tail service masts, also added, were backups. refers to the classification of a clean enabled cryogenic fueling and electrical Both cranes were capable of fine room environment in terms of the umbilical interfaces. movements, down to 0.003 cm number of particles allowed. In a Class Technology inside the mobile launcher (0.0 01 in.), even when lifting fully 100K, 0.03 m 3 (1 ft 3) of air is allowed platforms remained basically unchanged rated loads. The 295-metric-ton to have 100,000 particles whose size is for the first half of the program, reusing (325-ton) cranes used computer 0.5 micrometer (0.0002 in.). much of the -era hardware. The controls and graphics and could be Vehicle Assembly Hazardous Gas Leak Detection System set to release the brakes and “float” Integration for Launch was the first to be updated. It enabled the load, holding the load still in engineers in the firing room to monitor midair using motor control alone The SRB, ET, and Orbiter were levels of hydrogen gas in and around without overloading any part of the vertically integrated in the Vehicle the vehicle. Many manual systems crane or its motors. Assembly Building. also were automated and some could The cranes were located 140 m (460 ft) be controlled from remote locations above the Vehicle Assembly Building Mobile Launch Platform other than the firing rooms. ground floor. Crane operators relied on Technicians inside the building radio direction from ground controllers Assembly stacked the shuttle on one of three at the lift location. mobile launcher platforms originally Massive Cranes The cranes used two independent wire built in 1964 for the Apollo moon The size and weight of shuttle ropes to carry the loads. Each crane missions. These platforms were components required a variety of carried about 1.6 km (1 mile) of wire modified to accommodate the weight lifting devices to move and assemble rope that was reeved from the crane of the shuttle and still be transportable the vehicle. Two of the largest and to the load block many times. The by crawler transporters, and to most critical were the 295-metric-ton wire ropes were manufactured at the handle the increased pressure and (325-ton) and 227-metric-ton same time and from the same lot to heat caused by the SRBs. NASA (250-ton) cranes. ensure rope diameters were identical

The Orbiter is then mated with the External Tank and the Solid Rocket Booster.

Vehicle Assembly Building (continued)

80 The Space Shuttle and Its Operations and would wind up evenly on the and installations, the integrated shuttle vertical within +/- 10 minutes drum as the load was raised. shuttle vehicle was ready for rollout of 1 degree of arc—the diameter of to the launch pad. a basketball. The system also provided Stacking the Orbiter, External Tank, the leveling required to negotiate the and Solid Rocket Booster Rollout to Launch Pad 5% ramp leading to the launch pads SRB segments were moved to the and keep the load level when raised and Technicians retracted the access Vehicle Assembly Building. A lifting lowered on pedestals at the pad. platforms, opened the Vehicle beam was connected to the booster Assembly Building doors, and moved clevis using the 295-metric-ton Launch Pad Operations the tracked crawler transporter vehicle (325-ton) crane hook. The segment under the Once the crawler lowered the mobile was lifted off the pallet and moved into that held the assembled shuttle vehicle. launcher platform and shuttle onto the designated high bay, where it was a launch pad’s hold-down posts, a lowered onto the hold-down post The transporter lifted the platform team began launch preparations. These bearings on the mobile launcher off its pedestals and rollout began. required an average of 21 processing platform. Remaining segments were The trip to the launch pad took about days to complete. processed and mated to form two 6 to 8 hours along the specially built complete boosters. —two lanes of river gravel The two steel towers of Launch separated by a median strip. The rock Pads 39A and 39B stood 105.7 m Next in the stacking process was surface supported the weight of the (347 ft) above KSC’s coastline, atop hoisting the ET from a checkout cell, crawler and shuttle, and it reduced 13-m- (42-ft)-thick concrete pads. lowering into the integration cell, vibration. The crawler’s maximum Each complex housed a fixed service and mating it to the SRBs. Additional unloaded speed was 3.2 km/hr (2 mph) structure and a rotating service inspections, tests, and component and 1.6 km/hr (1 mph) loaded. structure that provided access to installations were then performed. electrical, pneumatic, hydraulic, Engineers and technicians on the The Orbiter was towed from the Orbiter hypergolic, and high-pressure gas lines crawler, assisted by ground crews, Processing Facility to the Vehicle to support vehicle servicing while operated and monitored systems during Assembly Building transfer aisle, protecting the shuttle from inclement rollout while drivers steered the raised to a vertical position, lowered weather. Pad facilities also included vehicle toward the pad. The crawler onto the mobile launcher platform, and hypergolic propellant storage (nitrogen leveling system kept the top of the mated. Following inspections, tests, tetroxide and monomethylhydrazine),

Once the process is complete, the Space Shuttle is transported to the launch pad. Crawler moving the shuttle stack to the launch pad.

Launch Pad: 28-30 days

The Space Shuttle and Its Operations 81 cryogenic propellant storage (liquid launch pad hardstand. It was covered hydrogen and liquid oxygen), a water with about 6 m (20 ft) of dirt fill and tower, a slide wire crew escape system, housed the equipment that linked and a pad terminal connection room. elements of the shuttle, mobile launcher platform, and pad with Liquid Hydrogen/Liquid Oxygen— the Launch Processing System in the Tankers, Spheres . NASA performed and controlled checkout, Chicago Bridge & Iron Company built countdown, and launch of the shuttle the liquid hydrogen and liquid oxygen through the Launch Processing System. storage spheres in the 1960s for the . The tanks were Payload Changeout Room two concentric spheres. The inner stainless-steel sphere was suspended Payloads were transported to the launch inside the outer carbon-steel sphere pad in a payload canister. At the pad, using long support rods to allow the canister was lifted with a 81 ,647-kg thermal contraction and minimize (90-ton) hoist and its doors were opened Technicians in the Payload Changeout Room heat conduction from the outside at Launch Pad 39B process the Hubble Space to the Payload Changeout Room—an environment to the propellant. The Telescope for STS-31 (1990). enclosed, environmentally controlled space between the two spheres was area mated to the Orbiter payload bay. insulated to keep the extremely 380,000 L (1 00,000 gal) of each The payload ground-handling cold propellants in a liquid state. commodity. The spheres contained mechanism—a rail-suspended, For liquid hydrogen, the temperature enough propellant to support three mechanical structure measuring 20 m is -253°C (-423°F); for liquid oxygen, launch attempts before requiring (65 ft) tall—captured the payload with the temperature is -1 83°C (-297°F). additional liquid from tankers. retention fittings that used a water-based hydraulic system with The spheres were filled to near capacity gas-charged accumulators as a cushion. prior to a launch countdown. A Pad Terminal Connection Room The mechanism, with the payload, successful launch used about 1. 7 million The Pad Terminal Connection Room was then moved to the aft wall of the L (450,000 gal) of liquid hydrogen and was a reinforced-concrete room Payload Changeout Room, the main about 830,000 L (220,000 gal) of liquid located on the west side of the flame doors were closed, and the canister oxygen . A launch scrub consumed about trench, underneath the elevated

The Space Shuttle arrives at the launch pad, where payloads are installed into the Orbiter cargo bay. Payload Changeout Room at launch pad.

Launch Pad (continued)

82 The Space Shuttle and Its Operations was lowered and removed from the engineering data and delivered to pad by the transporter. the Launch Processing System in the firing rooms, where computer displays Once the rotating was gave system engineers detailed views in the mate position and the Orbiter was of their systems. ready with payload bay doors open, technicians moved the payload ground- The unique Launch Processing System handling mechanism forward and software was specifically written to installed the payload into the Orbiter process measurements and send cargo bay. This task could take as many commands to on-board computers as 12 hours if all went well. When and ground support equipment Water spray at the launch pad was used to installation was complete, the payload suppress the acoustic vibration during launch. to control the various systems. was electrically connected to the Orbiter The software reacted either to and tested, final preflight preparations six 3.7-m- (1 2-ft)-high water spray measurements reaching predefined were made, and the Orbiter payload bay diffusers nozzles dubbed “rainbirds.” values or when the countdown clock doors were closed for flight. reached a defined time. Launch was done by the software. Sound Suppression Operational Systems— Test and Countdown If there were no problems, the button Launch pads and mobile launcher to initiate that software was pushed platforms were designed with a water Launch Processing System at the designated period called T minus deluge system that delivered high- 9 minutes (T=time). One of the last volume water flows into key areas to Engineers used the Launch Processing commands sent to the vehicle was protect the Orbiter and its payloads System computers to monitor thousands “Go for main engine start ,” which was from damage by acoustic energy and of shuttle measurements and control sent 10 seconds before launch. From rocket exhaust. systems from a remote and safe that point on, the on-board computers location. Transducers, built into were in control. They ignited the main The water, released just prior to on-board systems and ground support engines and the SRBs. main engine ignition, flowed through equipment, measured pipes measuring 2 .1 m (7 ft) in each important function diameter for about 20 seconds. (i.e. , temperature, pressure). The mobile launcher platform deck Those measurements water spray system was fed from were converted into

In the firing room at Kennedy Space Center, NASA clears the Space Shuttle for launch. STS-108 (2001) launch.

Launch Pad (continued)

The Space Shuttle and Its Operations 83 Training and Simulations

Launch Countdown Simulation The complexity of the shuttle required new approaches to launch team training. During Mercury, Gemini, and Apollo, a launch-day rehearsal involving the , flight crew, and launch control was adequate to prepare for launch. The shuttle, however, required more than just one rehearsal. Due to processing and facility requirements, access to actual hardware in a launch configuration only occurred near the actual launch day after the vehicle was assembled and rolled to the launch pad. The solution was to write a computer program that simulated Space Station Processing Facility for modules and other hardware at Kennedy Space Center. shuttle telemetry data with a computer crew loading into the crew cabin. math model and fed those data into Special Facilities and Tools The Orbiter was configured to simulate launch control in place of the actual a launch-day posture, giving the flight Facility Infrastructure data sent by a shuttle on the pad. crew the opportunity to run through Although the types of ground systems all required procedures. The flight crew Terminal Countdown Demonstration Test at KSC were common in many members also was trained in emergency large-scale industrial complexes, KSC The Terminal Countdown egress from the launch pad, including systems often were unique in their Demonstration Test was a dress use of emergency equipment, facility application, scale, and complexity. rehearsal of the terminal portion of fire-suppression systems, egress routes, the launch countdown that included slidewire egress baskets, emergency The Kennedy Complex Control the flight crew suit-up and flight bunker, emergency vehicles, and the System was a custom-built commercial systems available if they needed to facility control system that included egress the launch pad.

After launch, Solid Rocket Boosters separate from the Space Shuttle and are recovered in the Atlantic Ocean, close to Florida’s East Coast.

Solid Rocket Booster Recovery

84 The Space Shuttle and Its Operations about 15,000 monitored parameters, replace the entire high bay air volume of the vehicle in the Orbiter Processing 800 programs, and 300 different in fewer than 30 minutes. Facility. In that facility, the station was displays. In 1999, it was replaced with configured as a passive repeater to route The launch processing environment commercial off-the-shelf products. the uplink and downlink radio frequency included odorless and invisible gaseous signals to and from the Orbiter The facility heating, ventilating, and commodities that could pose safety Processing Facility and Merritt Island air conditioning systems for Launch threats. KSC used an oxygen-deficiency Launch Area using rooftop antennas. Pads 39A and 39B used commercial monitoring system to continuously systems in unique ways. During monitor confined-space oxygen content. Operations Planning Tools launch operations that required hazard If oxygen content fell below 19.5%, an proofing of the mobile launcher alarm was sounded and beacons flashed, Requirements and Configuration platform, a fully redundant fan— warning personnel to vacate the area. Management 149, 140 W (200 hp), 1.1 2 m (44 in.) in diameter—pressurized the mobile Communications and Tracking Certification of Flight Readiness was launcher platform and used more the process by which the Space Shuttle Shuttle communications systems and than 305 m (1 ,000 ft) of 1.2- by Program manager determined the equipment were critical to safe vehicle 1.9-m (48- by 75-in.) concrete sewer shuttle was ready to fly. This process operation. The communications and pipe as ductwork to deliver this verified that all design requirements tracking station in the Orbiter pressurization air. were properly approved, implemented, Processing Facility provided test, and closed per the established Facility systems at the Orbiter checkout, and troubleshooting for requirements and configuration Processing Facility high bays used Orbiter preflight, launch, and landing management processes in place at KSC. two fully redundant, spark-resistant activities. Communications and tracking air handling units to maintain a supported Orbiter communications and Requirements and configuration Class 100K clean work area in the navigations subsystems. management involved test requirements 73,624-m 3 (2.6-million-ft 3) high bay. and modifications. Test requirements Following landing at KSC, the During hazardous operations, two ensured shuttle integrity, safety, and communications and tracking station spark-resistant exhaust fans, capable performance. Modifications addressed monitored the Orbiter and Merritt Island of exhausting 2,492 m 3/min (88,000 permanent hardware or software Launch Area communications ft 3/min), worked in conjunction with changes, which improved the safety of transmissions during tow and spotting high bay air handling units and could flight or vehicle performance, and mission-specific hardware or software changes required to support the payload and mission objectives.

The recovered Solid Rocket Boosters are returned to Kennedy Space Center for refurbishment and reusability.

The Space Shuttle and Its Operations 85 NASA generated planning, executing, shuttle processing sites, including the Propulsion System had to be able to and tracking products to ensure the three Orbiter Processing Facility bays, control the flow of cryogenic propellant completion of all processing flow Vehicle Assembly Building, launch through a wide range of flow rates. steps. These included: process and pads, Shuttle Landing Facility, and The liquid hydrogen flow through the support plans; summary and detailed Hypergolic Maintenance Facility. vehicle was as high as 32,550 L/min assessments; milestone, site, (8,600 gal/min). While in stable maintenance, and mini schedules; replenish, flow rates as low as and work authorization documents. Space Shuttle Launch 340 L/min (90 gal/min) had to be Over time, many operations tools Countdown Operations maintained with no adverse affects on evolved from pen and paper, to Launch countdown operations occurred the quality of the super-cold propellant. mainframe computer, to desktop PC, over a period of about 70 hours during Once the tank was loaded and stable, and to Web-based applications. which NASA activated, checked NASA sent teams to the launch pad. Work authorization documents out, and configured the shuttle vehicle One team inspected the vehicle for implemented each of the thousands systems to support launch. Initial issues that would prevent launch, of requirements in a flow. Documents operations configured shuttle data and including ice formation and cracks in included standard procedures computer systems. Power Reactant the ET foam associated with the tank performed every flow as well as Storage and Distribution System loading. Another team configured the nonstandard documents such as loading was the next major milestone crew cabin and the room used to access problem and discrepancy reports, test in the countdown operation. Liquid the shuttle cabin . Flight crew members, preparation sheets, and work orders. oxygen and liquid hydrogen had to be who arrived a short time later, were transferred from tanker trucks on the strapped into their seats and the hatch Kennedy Space Center Integrated launch pad surface, up the fixed service was secured for launch. Control Schedule structure, across the rotating service structure, and into the on-board storage The remaining operations configured The KSC Integrated Control Schedule tanks, thus providing the oxygen and the vehicle systems to support the was the official, controlling schedule hydrogen gas that the shuttle fuel cells terminal countdown. At that point, for all work at KSC’s shuttle required to supply power and water the ground launch sequencer sent the processing sites. This integration tool while on . commands to perform the remaining reconciled conflicts between sites and operations up to 31 seconds before resources among more than a dozen The next major milestones were launch, when the on-board computers independent sites and multiple shuttle activation of the communication took over the countdown and missions in work simultaneously. equipment and movement of the performed the main engine start and Work authorization documents could rotating service structure from the booster ignition. not be performed unless they were mate position (next to the shuttle) to entered on this schedule, which the park position (away from the Solid Rocket Booster Recovery distributed the required work shuttle), which removed much access Following shuttle launch, preparations authorization documents over time to the vehicle. continued for the next mission, and sequenced the work in the proper The most hazardous operation, short beginning with SRB recovery. order over the duration of the of launch, was loading the ET with processing flow. The schedule, liquid oxygen and liquid hydrogen. Approximately 1 day before launch, published on the Web every workday, This was performed remotely from the the two booster recovery ships— contained the work schedule for the Launch Control Center. The Main Freedom Star and Star—left following 11 days for each of the 14 Air Force Station and

86 The Space Shuttle and Its Operations Port Canaveral to be on station prior to Parachutes exposed to 60°C (140°F) air for 10 to launch to retrieve the boosters from 12 hours, after which they were SRB main parachute canopies were the the Atlantic Ocean. inspected, repaired, and packed into a only parachutes in their size class that three-part main parachute cluster and Approximately 6½ minutes after were refurbished. NASA removed the transferred to the Assembly and launch, the boosters splashed down parachutes from the retrieval ships and Refurbishment Facility for integration 258 km (1 60 miles) downrange. Divers transported them to the Parachute into a new forward assembly. separated the three main parachutes Refurbishment Facility. from each booster and the parachutes At the facility, technicians unspooled, were spun onto reels on the decks of defouled, and inspected the parachutes. Summary each ship. The divers also retrieved Following a preliminary damage drogue chutes and frustums and lifted In conclusion, the success of each mapping to assess the scope of repairs them aboard the ships. shuttle mission depended, without required, the parachutes were hung on exception, on ground processing. The For the boosters to be towed back to a monorail system that facilitated series of planning and execution steps KSC, they were repositioned from movement through the facility. The required to process the largest and most vertical to horizontal. Divers placed first stop was a 94,635-L (25,000-gal) complex reusable space vehicle was an enhanced diver-operated plug into horizontal wash tank where each representative of NASA’s ingenuity, the nozzle of the booster, which was parachute underwent a 4- to 6-hour dedicated workforce, and unmatched 32 m (1 05 ft) below the ocean surface. fresh water wash cycle to remove all ability, thus contributing immensely to Air was pumped into the boosters, foreign material. The parachutes were the legacy of the Space Shuttle Program. displacing the water inside them and transferred to the drying room and repositioning the boosters to horizontal. The boosters were then moved alongside the ships for transit to Cape Canaveral Air Force Station where they were disassembled and refurbished. Nozzles and motor segments were shipped to the manufacturer for further processing. Following recovery, the segments were taken apart and the joints were inspected to make sure they had performed as expected. Booster components were inspected and hydrolased—the ultimate pressure cleaning—to remove any residual fuel and other contaminants. Hydrolasing was done manually with a gun operating at 103,4 21 kPa (1 5,000 psi) and robotically at up to 120,658 kPa (1 7,500 psi). Following cleaning, the frustum and forward skirt were media- blasted and repainted.

Technicians assemble a Solid Rocket Booster parachute at Kennedy Space Center.

The Space Shuttle and Its Operations 87 Space Operations Weather: How NASA, the National Weather Service, and the Air Force Improved Predictions

Weather was the largest single cause of delays or scrubs of launch, landing, and ground operations for the Space Shuttle.

The Shuttle Weather Legacy NASA and the US Air Force (USAF) worked together throughout the program to find and implement solutions to weather-related concerns. The Kennedy Rollout of , STS-128 (2009), was delayed by onset of lightning in the area of Space Center (KSC) Weather Office Launch Pad 39A at Kennedy Space Center. Photo courtesy of Environmental Protection Agency. played a key role in shuttle weather operations. The National Weather enabled safe ground launch and Service operated the Spaceflight Living With Lightning, landing, they contributed to atmospheric Meteorology Group at Johnson Space a Major Problem at Launch science related to observation and Center (JSC) to support on-orbit and Complexes Worldwide prediction of lightning, wind, ground landing operations for its direct and atmosphere, and clouds. Naturally occurring lightning activity customers—the shuttle flight directors. associated with thunderstorms occurs At Marshall Space Flight Center, the By the late 1980s, 50% of all launch at all launch complexes, including Natural Environments Branch provided scrubs were caused by adverse weather KSC and Cape Canaveral Air Force expertise in climatology and analysis conditions—especially the destructive Station. Also, the launch itself can of meteorological data for both launch effects of lightning, winds, hail, and trigger lightning—a problem for and landing operations with emphasis temperature extremes. So NASA and launch complexes that have relatively on support for engineering analysis their partners developed new methods infrequent lightning may have a and design. The USAF 45th Weather to improve the forecasting of weather substantial potential for rocket-triggered Squadron provided the operational phenomena that threatened missions, lightning. The launch complex at weather observations and forecasting for including the development of Vandenberg Air Force Base, California, ground operations and launch at the technologies for lightning, winds, and is a primary example. space launch complex. This collaborative other weather phenomena. The Space community, which worked effectively Shuttle Program led developments Natural lightning discharges may occur as a team across the USAF, NASA, and innovations that addressed within a single thundercloud, between and the National Weather Service, not weather conditions specific to Florida, thunderclouds, or as cloud-to-ground only improved weather prediction to and largely supported and enhanced strikes. Lightning may also be triggered support the Space Shuttle Program and launch capability from the Eastern by a conductive object, such as a Space spaceflight worldwide in general, it also Range. Sensor technologies developed Shuttle, flying into a region of contributed much to our understanding were used by, and shared with, atmosphere where strong electrical of the atmosphere and how to observe other meteorological organizations charge exists but is not strong enough by and predict it. Their efforts not only throughout the country. itself to discharge as a lightning strike.

88 The Space Shuttle and Its Operations Natural lightning is hazardous to all aerospace operations, particularly those that take place outdoors and away from Lightning Flash Density at Launch protective structures. Triggered lightning is only a danger to vehicles in flight but, Complexes as previously described, may occur even when natural lightning is not present.

Lightning Technology at the Space Launch Complex Crucial to the success of shuttle operations were the activities of the USAF 45th Weather Squadron, which provided all launch and landing orbit weather support for the space launch complex. Shuttle landing support was provided by the National Weather Service Spaceflight Meteorology Group located at JSC. The 45th Weather Squadron operated from Range Weather Operations at Cape Canaveral Air Force Station. The Spaceflight Flash density is a measure of how many lightning flashes occur in a particular area Meteorology Group housed weather or location over time. Florida, and particularly the space launch complex, receives system computers for forecast and also analyzed data from the National Centers the highest density of lightning flashes in the contiguous 48 states. Review of for Environmental Prediction, weather lightning flash activity at the complex over many years shows that the highest average imagery, and local weather activity levels occur between June and September, and the lowest levels between sensors as well as assisted in putting November and January. together KSC area weather forecasts. Another key component of shuttle operations was the KSC Weather processing and launch commit Launch Pad Lightning Warning System Office, established in the late 1980s. criteria for the shuttle were properly data helped forecasters determine The KSC Weather Office ensured all considered. It coordinated all when surface electric fields may have engineering studies, design proposals, weather research and development, been of sufficient magnitude to create anomaly analyses, and ground incorporating results into operations. triggered lightning during launch. The data also helped determine when Lightning Evaluation Tools System Network to issue and cancel lightning advisories and warnings. The original Lightning Launch Pad Lightning Warning System Thirty-one electric-field mills that serve as an early warning system for electrical charges building aloft due to a storm system. Detection and Ranging System, developed by NASA at KSC, sensed Lightning Detection and Ranging Nine antennas that detect and locate lightning in three dimensions within 185 km (100 nautical miles) using a “time of arrival” computation on signals. electric fields produced by the processes of breakdown and channel National Lightning Detection Network One-hundred ground-based sensing stations that detect cloud-to-ground lightning activity across the continental US. The sensors instantaneously formation in both cloud lightning and detect the electromagnetic signal given off when lightning strikes the ground. cloud-to-ground flashes. The locational Cloud-to-Ground Lightning Six sensors spaced much closer than in the National Lightning Detection accuracy of this system was on the Surveillance System Network. order of +/- 100 m (328 ft). In 2008, a Weather Radar Two radars that provide rain intensity and cloud top information. USAF-owned system replaced the

Systems used for weather and thunderstorm prediction and conditions.

The Space Shuttle and Its Operations 89 original KSC Lightning Detection and accurate and timely reporting capability orderly manner. A Phase II warning was Ranging System, which served the space over that of the upgraded Cloud-to- issued when lightning was imminent or launch complex for about 20 years. Ground Lightning Surveillance System occurring within 8 km (5 miles) of the or the older Lightning Detection and designated site. All lightning-sensitive The National Lightning Detection Ranging System individually, and it operations were terminated until the Network plots cloud-to-ground allowed for enhanced space launch Phase II warning was lifted. This lightning nationwide and was used to operations support. two-phase policy provided adequate identify cloud-to-ground strikes at KSC lead time for sensitive operations and to ensure safe transit of the Orbiter Launch and landing forecasters located without shutting down less-sensitive atop the . A in Texas, and Cape Canaveral, Florida, operations until the hazard became National Lightning Detection Network accessed displays from two different immediate. Much of this activity was upgrade in 2002-2003 enabled the Florida radar sites—one located at on the launch pads, which were tall, system to provide a lightning flash- Patrick Air Force Base, and a NEXRAD isolated, narrow structures in detection efficiency of approximately (next-generation weather radar) wide-open areas and were prime 93% of all flashes with a location Doppler, located in Melbourne at the targets for lightning strikes. Lightning accuracy on the order of +/-500 to National Weather Service. advisories were critical for the safety 600 m (1 ,640 to 1,968 ft). of over 25,000 people and resource Lightning Operational protection of over $ 18 billion in The Cloud-to-Ground Lightning Impacts; Warning Systems Surveillance System is a lightning facilities. Several more billion dollars detection system designed to record The likelihood of sustaining damage could be added to this value, depending cloud-to-ground lightning strikes in from natural lightning was reduced by on what payloads and were at the vicinity of the space launch minimizing exposure of personnel and the launch pads or in transit outside. complex. A Cape Canaveral Air Force hardware during times when lightning This policy ultimately reduced ground Station upgrade in 1998 enabled the threatened. To accomplish this, it was processing downtime by as much as system to provide a lightning necessary to have in place a balanced 50% compared to the older system, flash-detection efficiency within the warning system whereby lightning saving millions of dollars annually. sensor array of approximately 98% of activity could be detected and reported Operationally, warnings were all flashes and with a location accuracy far enough in advance to permit sometimes not sufficient, for example on the order of +/-250m (820 ft). protective action to be taken. Warnings during launch operations when needed to be accurate to prevent harm The Lightning Detection and Ranging real-time decisions had to be made yet not stop work unnecessarily. System was completely upgraded based on varying weather conditions Lightning advisories were important during the shuttle era with new sensors with a potentially adverse effect on for ground personnel, launch systems, positioned in nine locations around the flight. Following a catastrophic and the transport of hardware, including space launch complex proper. Along lightning-induced failure of an the 6- to 8-hour transport of the Space with a central processor, the system was Atlas/Centaur rocket in 1987, a Shuttle to the launch pad. referred to as the Four-Dimensional blue-ribbon “Lightning Advisory Lightning Surveillance System. This The original deployment of the Panel” comprising top American new central processor was also capable Lightning Detection and Ranging lightning scientists was convened to of processing the Cloud-to-Ground System pioneered a two-phase lightning assist the space program. The panel Lightning Surveillance System sensor policy. In Phase I, an advisory was recommended a set of “lightning data at the same time and, moreover, issued that lightning was forecast launch commit criteria” to avoid produced full cloud-to-ground stroke within 8 km (5 miles) of the designated launching into an environment data rather than just the first stroke in site within 30 minutes of the effective conducive to either natural or triggered real time. The synergistic combination time of the advisory. The 30-minute lightning. These criteria were adopted of the upgraded Four-Dimensional warning gave personnel time to get to a by NASA for the Space Shuttle Lightning Surveillance System and protective shelter and gave personnel Program, and also by the USAF for all the Cloud-to-Ground Lightning working on lightning-sensitive tasks military and civilian crewless launches Surveillance System provided a more time to secure operations in a safe and from the Eastern and Western Ranges.

90 The Space Shuttle and Its Operations Hail Damage to the External Tank

On the afternoon of February 26, 2007, during STS-117 prelaunch processing at Kennedy Space Center (KSC) Launch Pad A, a freak winter thunderstorm with hail struck the launch complex and severely damaged the External Tank (ET) (ET-124) Thermal Protection System foam insulation. The hail strikes caused approximately 7,000 divots in the foam material. The resulting damage revealed that the vehicle stack would have to be returned to the Vehicle Assembly Building to access the damage. This would be the second time hail caused the shuttle to be ET-124 damage repairs, post storm. returned to the building. To assess the damage, NASA built customized scaffolding. The design and installation of the scaffolding needed to reach the sloping forward section of the tank was a monumental task requiring teams of specialized riggers called “High Crew” to work 24 hours a day for 5 straight days. A hand-picked engineering assessment team evaluated the damage. The ET liquid oxygen tank forward section was the most severely damaged area and required an unprecedented repair effort. There were thousands of damaged areas that violated the ET engineering acceptance criteria for flight. NASA assembled a select repair team of expert technicians, quality inspectors, and engineers to repair the damage. This team was assisted by manufacturing specialists from Lockheed Martin, the ET manufacturer, and Marshall Space Flight Center.

KSC developed an inexpensive, unique hail monitoring system using a piezoelectric device and sounding board to characterize rain and hail. While the shuttle was at the pad, three remote devices constantly monitored the storms for potential damage to the vehicle.

The lightning launch commit criteria, accessible online archive. This data Lightning Protection and as initially drafted, were very set is the largest, most comprehensive Instrumentation Systems conservative as electrical properties of its kind. Physical lightning protection for the of clouds were not well understood. The Airborne Field Mill science team shuttle on the pad was provided by a Unfortunately, this increased the developed a quantity called Volume combination of a large, loose network of number of launches that had to be Averaged Height Integrated Radar wiring known as a counterpoise beneath postponed or scrubbed due to weather Reflectivity that could be observed with the pad structure and surrounding conditions. The program undertook a weather radar. This quantity, when environs and a large wire system series of field research initiatives to small enough, assured safe electric comprising a 2.5-cm- (1 -in.)-, 61 0-m- learn more about cloud electrification fields aloft. As a result, the Lightning (2,000-ft)-long steel cable anchored and in hopes that the criteria could safely Advisory Panel was able to recommend grounded at either end and supported be made less restrictive. changes to the lightning launch in the middle by a 24.4-m- (80-ft)-tall These field research initiatives used commit criteria to make them both safer nonconductive mast. The mast also aircraft instrumented with devices and less restrictive. The new criteria served to prevent currents—from called electric field mills that could are used by all US Government launch lightning strikes to the wire—from measure the strength of the electric facilities, and the Federal Aviation passing into the pad structure. A 1.2-m field in clouds as the aircraft flew Administration is including them in (4-ft) air terminal, or lightning rod, through them. The research program its regulations governing the licensing was mounted atop the mast and was known as Airborne Field Mill. of private . These criteria electrically connected to the steel cable. Data collected by the Airborne were expressed in detailed rules that The cable arrangement assumed a Field Mill program were subjected described weather conditions likely characteristic curved shape to either side to extensive quality control, time- to produce or be associated with of the pad described mathematically synchronized, and consolidated into lightning activity, the existence of as a catenary and therefore called the a carefully documented, publicly which precluded launch. Catenary Wire System.

The Space Shuttle and Its Operations 91 Lightning It was comprised of both voltage Mast monitoring on the Orbiter power busses Lightning Mast Cables and magnetic field sensing internal to Zone of the Orbiter middeck, the aft avionics Lightning PProtectionrotection bay, the Payload Changeout Room, and locations on the pad structure. The collected voltage and magnetic field data were used to determine induced current and voltage threats to equipment, allowing direct comparison to known, acceptable maximum levels for the vehicle and its equipment. The elaborate lightning detection and personnel protection systems at KSC proved their worth the hard way. The lightning masts at Launch Pads 39A and 39B were struck many times with a A grounded stainless-steel cable extends from the lightning mast to provide a zone of protection for shuttle on the pad, with no damage to the launch vehicle. equipment. No shuttle was endangered during launch, although several Additional lightning protection devices In addition to physical protection launches were delayed due to reported at the launch pads included a grounded features, the Space Shuttle Program weather conditions. overhead shield cable that protected employed lightning monitoring systems the crew emergency egress slide wires to determine the effects of lightning Ultimately, one of the biggest attached to the fixed service structure. strikes to the catenary system, the contributions to aerospace vehicle Grounding points on the pad surface immediate vicinity of the launch pad, design for lightning protection was the and the mobile launcher platform and and the shuttle itself. The shuttle used original standard developed by NASA electrical connections in contact with two specific lightning monitoring for the shuttle. New standards developed the shuttle completed the system that systems—the Catenary Wire Lightning by the Department of Defense, the conducted any lightning-related currents Instrumentation System and the Federal Aviation Administration, and safely away from the vehicle. Overhead Lightning Induced Voltage grid-wire systems protected hypergolic Instrumentation System. The Catenary fuel and oxidizer storage areas. The Wire Lightning Instrumentation System huge 3,407,000-L (900,000-gal) liquid used sensors located at either end of the Lightning hydrogen and liquid oxygen tanks at Catenary Wire System to sense currents each pad were constructed of metal and in the catenary wire induced by nearby Delays Launch did not need overhead protection. or direct lightning strikes. The data were then used to evaluate the potential In August 2006, while STS-115 was The shuttle and its elements were well for damage to sensitive electrical on the pad, the lightning mast suffered protected from both inclement weather equipment on the shuttle. The Lightning a 50,000-ampere attachment, much and lightning away from the pad while Induced Voltage Instrumentation in the Vehicle Assembly Building. stronger than the more typical 20,000- System used voltage taps and current This 160-m- (525-ft)-high structure to 30,000-ampere events, resulting in sensors located in the shuttle and the had eleven 8-m- (25-ft)-high lightning a 3-day launch delay while engineers mobile launcher platform to detect conductor towers on its roof. When and record voltage or current transients and managers worked feverishly to lightning hit the building’s air terminal in the shuttle Electrical Power System. determine the safety of flight condition system, wires conducted the charge to of the vehicle. The vehicle, following the towers, which directed the current After STS -11 5, NASA performed a down the Vehicle Assembly Building’s system review and decided to upgrade extensive data review and analysis, sides and into bedrock through the the two systems. The Ground Lightning was declared safe to fly. building’s foundation pilings. Monitoring System was implemented.

92 The Space Shuttle and Its Operations commercial organizations over the years have leveraged this pioneering effort, and the latest of these Hurricane standards is now applicable for design of the new spacecraft. Damage

Space Shuttle processing during Working With Winds Florida’s hurricane season was a Between the Earth’s surface and about constant challenge to ground 18 km (1 0 nautical miles) altitude, the processing. Hurricane weather Earth’s atmosphere is dense enough that patterns were constantly winds can have a big effect on an monitored by the team. If the Damage to Vehicle Assembly Building at Kennedy ascending spacecraft. Not only can the Space Center during Hurricane Frances. storms could potentially cause wind blow a vehicle toward an undesirable direction, the force of the damage to the vehicle, the stack was rolled back to the Vehicle Assembly Building for wind can cause stress on the vehicle. protection. During Hurricane Frances in September 2004, Kennedy Space Center The steering commands in the vehicle’s suffered major damage resulting from the storm. The Vehicle Assembly Building lost guidance computer were based on winds approximately 820 aluminum side panels and experienced serious roof damage. measured well before launch time. If large wind changes occurred between the time the steering commands were launch pad. The profiler scattered radar profilers, it was sufficiently complex calculated and launch time, it was waves off turbulence in the atmosphere and its run time too long for operational difficult for the vehicle to fly the desired and measured their speed in a manner use to be practical. trajectory or the vehicle would be similar to a traffic policeman’s radar stressed beyond its limits and break up. To use wind profiler data, NASA gun. It produced a complete profile Therefore, frequent measurements of developed algorithms for wind profiles of wind speed and direction every wind speed and direction as a function that included the ground wind profile, 5 minutes. This produced profiles of height were made during countdown. high-altitude weather balloons, and 12 times faster than a balloon and Doppler radar. This greatly enhanced The Space Shuttle Program measured much closer to the flight path of the the safety of space launches. upper air winds in two ways: high- vehicle. Its only technical disadvantage resolution weather balloons and a was that the smallest feature in the Doppler radar wind profiler. Both had a atmosphere it could distinguish was Landing Weather Forecasts wind speed accuracy of about 1 m/sec 300 m (984 ft) in vertical extent. (3.3 ft/sec). Balloons had the advantage The Doppler radar wind profiler was The most important shuttle landing step of being able to detect atmospheric first installed in the late 1980s. occurred just prior to the deorbit burn features as small as 100 m (328 ft) in decision. The National Weather Service When originally delivered, the profiler vertical extent, and have been used Spaceflight Meteorology Group’s was equipped with commercial since the beginning of the space weather prediction was provided to the software that provided profiles with program. Their primary disadvantages JSC flight director about 90 minutes unknown accuracy every 30 minutes. were that they took about 1 hour to prior to the scheduled landing. This For launch support, NASA desired a make a complete profile from the forecast supported the Mission Control higher rate of measurement and surface to 18 km (11 miles), and they Center’s “go” or “no-go” deorbit burn accuracy as good as the high-resolution blew downwind. In the winter at KSC, decision. The deorbit burn occurred balloons. Although the Median Filter jet stream winds could blow a balloon about 60 minutes prior to landing. First Guess software, used in a as much as 100 km (62 miles) away The shuttle had to land at the specified laboratory to evaluate the potential from the launch site before the balloon landing site. The final 90-minute value of the Doppler radar wind reached the top of its trajectory. landing forecast had to be precise, profiler, significantly outperformed any accurate, and clearly communicated for The wind profiler was located near the commercially available signal NASA to make a safe landing decision. Shuttle Landing Facility, close to the processing methodology for wind

The Space Shuttle and Its Operations 93