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Rocket reusability dates as long as rockets. Since the beginning of space age, the possibility to reuse the full vehicle or some stages has been a matter of engineering. But this was directly opposite to mass ratio efficiency, the key for a well-designed rocket. Since as soon as a stage has to be recovered, subsystems to provide this function and additional inert mass are needed. Even if reusable systems are only a small part of the worldwide rockets, they flew operationally since the space shuttle age. However, full reusable vehicles are not yet operational and only partially reusable launch vehicles have been flown until now. The preliminary space shuttle design consisted of two stages both liquid and reusable (booster and orbiter stages). The consolidated design retrieved the orbiter (upper stage, the cargo and propulsion bay) and the solid rocket boosters. On Russian side Energia-Buran only retrieved the upper stage with its cargo bay and the same approach was adapted for the original design of Ariane 5-Hermes. Europe investigated and developed different reusable systems, set up test facilities and flew the IXV demonstrator in 2015. More recently, the preferred strategy consists in reuse of unwinged booster stages (e.g. Falcon 9 of SpaceX) or of only the orbited spacecraft (e.g. NASA-USAF X-37). France and Europe are preparing propulsion and reusable rocket stage demonstration bricks for next generation launchers. The purpose of this paper is to provide an overview of some reusable space systems with emphasis on the different design strategy and skills mainly focused on European heritage. The systems are split into low and high energy with a view to technology aspects and in-flight experiments.

BACKGROUND: Glaucoma and ocular hypertension (OHT) are prevalent diseases with baseline intraocular pressure (IOP) elevations that future astronauts and spaceflight participants may suffer from. Preflight, in-flight, and postflight IOP measurements were collected aboard two U.S. Space Shuttle Program missions in normotensive control, OHT, and glaucomatous crewmembers. METHODS: Five subjects (three controls, one glaucomatous, one OHT) were studied aboard 2-wk Space Shuttle missions. Baseline IOP (triplicate; handheld tonometry) was recorded during training 12 mo preflight, in flight (114 d), and postflight (329 d). Subjective symptoms were recorded via questionnaires. Data were analyzed using a spreadsheet with two-sample t-tests. P-value < 0.05 determined significance. RESULTS: IOP increased for all in-flight vs. preflight measurements for controls (N 3, 48.9, 16.9, 5.85), OHT (N 1, 20.3), and glaucomatous (N 1, 32.2) groups. IOP eventually returned to baseline postflight [Return (R)35 d], except for the astronaut with OHT (R917). Subjective symptoms, likely multifactorial, included blurredvision, decreased visual acuity, and headaches. DISCUSSION: IOP increased during spaceflight and normalized upon return. Astronauts and commercial spaceflight participants may need screening for elevated IOP to potentially prevent sequelae related to glaucoma and OHT, the former which requires treatment in flight and the latter which may need prophylaxis. Previous studies have shown elevated IOP upon entry into microgravity with various normalization timeframes in flight and postflight. It is unclear how increased IOP relates to spaceflight-associated neuro-ocular syndrome (SANS); however, several hypotheses exist. Treatment strategies should be available for acute and chronic ocular pathology during spaceflight despite the unique challenges of eye-drop application in microgravity. Dalal SR, Ramachandran V, Khalid R, Manuel FK, Knowles JR, Jones JA. Increased intraocular pressure in glaucomatous, ocular hypertensive, and normotensive space shuttle crew. Aerosp Med Hum Perform. 2021; 92(9):728733.

Aluminum and titanium char-layer deposits discovered on overhead windows recovered from the Space Shuttle Columbia accident revealed unexpected material response. It was observed that titanium melted and deposited before aluminum: behavior inconsistent with their relative melting temperatures. In close proximity to the windows, payload bay door (PLBD) latch rollers, containing Ti-6Al-4V, exhibited significant thermal damage that could not be explained by re-entry heating alone. The roller was considered a likely source of the deposition as damage was localized to the titanium region and the component was evaluated to identify features of ignition and/or combustion. A second examination was conducted on arc-jet samples obtained from a previous work that studied Ti-6Al-4V combustibility in a simulated re-entry environment. The samples were compared to the analysis of the PLBD roller and both exhibited features suggestive of titanium combustion. The PLBD roller possessed microstructural similarities to the arc-jet specimens that reacted more aggressively to the simulated environment.

In 2005 we reviewed microgravity for macromolecular crystallization, four years after the final flight of the Space Shuttle Orbiter, and five years before the first commercial flight to the Interna...

INTRODUCTION: Hypergolic propellants can be released in large amounts during space launch contingencies. Whether propellant-contaminated suit fabric poses a significant risk to rescue crews, due to off-gassing, has not been explored in detail. In this study, we addressed this issue experimentally, exposing space suit fabric to propellants (dinitrogen tetroxide [N2O4] and monomethyl hydrazine [MMH]).METHODS: The NASA Space Shuttle Program Advanced Crew Escape System II (ACES II) is similar to the NASA Orion Crew Survival System (OCSS) and was utilized here. Suit fabric was placed and sealed into permeation cells. Fabric exterior surface was exposed to constant concentrated hypergolics, simulating permeation and leakage. Fabric was rinsed, and permeation and off-gassing kinetics were measured. Experimental parameters were selected, simulating suited flight crewmembers during an evacuation transport without cabin air flow.RESULTS: The fabric allows for immediate permeation of liquid or vaporized MMH and N2O4. NO2 off-gassing never exceeded the AEGL-1 8-h level (acute exposure guideline level). In contrast, MMH off-gassing levels culminated in peak levels, approaching AEGL-2 10-min levels, paralleling the drying process of the fabric layers. DISCUSSION: Our findings demonstrate that MMH off-gassing is promoted by the drying of suit material in a delayed fashion, resulting in MMH concentrations having the potential for adverse health effects for flight and rescue crews. This indicates that shorter decontamination times could be implemented, provided that suit material is either kept moist to prevent off-gassing or removed prior to medical evacuation. Additional studies using OCSS or commercial crew suits might be needed in the future.Schwertz H, Roth LA, Woodard D. Propellant off-gassing and implications for triage and rescue. Aerosp Med Hum Perform. 2020; 91(12):956961.

Subcentimeter orbital debris is currently undetectable using ground-based radar and optical methods. However, pits in space shuttle windows produced by paint chips demonstrate that small debris can...

To expand the selection of preassigned shock surfaces, a new inverse design method called the local-turning osculating cones method has been proposed for waverider design. The new method discretize...

Sleep deficiencies and associated performance decrements are common among astronauts during spaceflight missions. Previously, sleep in space was analyzed with a focus on global measures while the intricate structure of sleep oscillations remains largely unexplored. This study extends previous findings by analyzing how spaceflight affects characteristics of sleep spindles and slow waves, two sleep oscillations associated with sleep quality and quantity, in four astronauts before, during and after two Space Shuttle missions. Analysis of these oscillations revealed significantly increased fast spindle density, elevated slow spindle frequency, and decreased slow wave amplitude in space compared to on Earth. These results reflect sleep characteristics during spaceflight on a finer electrophysiological scale and provide an opportunity for further research on sleep in space.

The growth and development of plants during spaceflight have important implications for both basic and applied research supported by NASA and other international space agencies. While there have been many reviews of plant space biology, this chapter attempts to fill a gap in the literature on the actual process and methods of performing plant research in the spaceflight environment. One of the authors (JZK) has been a principal investigator on eight spaceflight projects. These experiences include using the U.S. Space Shuttle, the former Russian Space Station Mir, and the International Space Station, utilizing the Space Shuttle and Space X as launch vehicles. While there are several ways to fly an experiment into space and to obtain a spaceflight opportunity, this review focuses on using the NASA peer-reviewed sciences approach to get an experiment manifested for flight. Three narratives for the implementation of plant space biology experiments are considered from rapid turn around of a few months to a project with new hardware development that lasted 6 years. The many challenges of spaceflight research include logistical and resource constraints such as crew time, power, cold stowage, data downlinks, among others. Additional issues considered are working at NASA centers, hardware development, safety concerns, and the engineering versus science culture in space agencies. The difficulties of publishing the results from spaceflight research based on such factors as the lack of controls, limited sample size, and the indirect effects of the spaceflight environment also are summarized. Lessons learned from these spaceflight experiences are discussed in the context of improvements for future space-based research projects with plants. We also will consider new opportunities for Moon-based research via NASA's Artemis lunar exploration program.

As clocks across Florida struck eight on the last Monday of 1980, a new era began. In the early morning gloom, the doors of the Vehicle Assembly Building (VAB) – a 53-story sugar-cube of a structure which stood dominant over the marshy flatness of the Kennedy Space Center (KSC) on Merritt Island – clanked ajar to reveal a spacecraft like no other. It shimmered in the rays of the newly risen sun as the warming fingers of dawn gently caressed its flight surfaces and picked out its textures and contours in stark relief. The first Space Shuttle, named ‘Columbia’ in honor of the female personification of the United States, was on the move, bound for the launch pad. And after a troubled decade in development, the greatest experimental flying machine in history was about to spread its wings.

During the launch of the Chandra X-Ray Observatory in 1999, an in-flight anomaly occurred a few seconds after liftoff. A power fluctuation caused two Main Engine controllers to drop offline. Fortunately, due to redundancy, the Space Shuttle Columbia was able to successfully reach orbit and avoid an abort. After the successful deployment of Chandra and the safe return of the crew, investigation revealed that the controller failure was due to a wire short in the payload bay. It was suspected that the Kapton insulation on the wire rubbed off against a burred screw head, the result of overtightening of the screw during a maintenance event 4 to 5 years prior to the STS-93 mission. Vibrations led the abraded wire to short during flight. The Space Shuttle Program was grounded for 4 months while a program-wide inspection and wire chafing mitigation effort of all orbiter wiring ensued.

Nozzles are one of the most efficient ways of producing thrust. Most of the modern day launch vehicles use a conventional Converging-Diverging nozzle (CD nozzle). One of the critical drawbacks of using these nozzles is in their inability to provide the same efficiency under varying conditions of the course of the flight. CD nozzles when developed are designed to work at a certain range of altitudes, i.e. either at sea level or under near vacuum conditions. Hence, a sea level optimized nozzle can’t provide the same efficiency at higher altitudes and vice versa. Thus, modern day rockets have multiple stages (usually 2), with the first stage having a sea level optimized nozzle which lifts the rocket from the launch pad and takes it to an altitude before being ejected along with first stage and the second stage having vacuum optimized nozzle which propels the payload in vacuum of space to a desired orbit. This results in higher operating costs for a single launch, makes the process of payload deployment more complicated. The problem of having to use multiple nozzles can be solved by using an altitude compensating nozzle, with aerospike nozzle being one of them. These nozzles under operation provide the same efficiency throughout the course of flight under varying ambient conditions. This makes possible the development of a single stage to orbit vehicle, SSTO having a single aerospike nozzle. An SSTO vehicle unlike modern rockets doesn’t have components which require to be jettisoned during its flight and thus retains its expensive hardware even after being recovered. Hence, an SSTO vehicle results in less operating costs, having optimum payload capability. An SSTO having aerospike when developed properly is highly versatile it terms of thrust vectoring, and it has the potential of being completely reusable, by using a compact single structure similar to space shuttle and using aerodynamic re-entry. This paper analyses the performance of aerospike by comparison with CD nozzle using CFD (Computational Fluid Dynamics).

NASA is developing an expendable heavy lift launch vehicle capability, the Space Launch System, to support lunar and deep space exploration. To support this capability, an updated ground infrastructure is required including modifying an existing Mobile Launcher system. The Mobile Launcher is a very large heavy beam/truss steel structure designed to support the Space Launch System during its buildup and integration in the Vehicle Assembly Building, transportation from the Vehicle Assembly Building out to the launch pad, and provides the launch platform at the launch pad. The previous Saturn/Apollo and Space Shuttle programs had integrated vehicle ground vibration tests of their integrated launch vehicles performed with simulated free-free boundary conditions to experimentally anchor and validate structural and flight controls analysis models. For the Space Launch System program, the Mobile Launcher will be used as the modal test fixture for the ground vibration test of the first Space Launch System flight vehicle, Exploration Mission ? 1( now referred to as Artemis 1), programmatically referred to as the Integrated vehicle modal test. The Integrated vehicle modal test of the Exploration Mission - 1 integrated launch vehicle will have its core and second stages unfueled while mounted to the ML while inside the Vehicle Assembly Building, which is currently scheduled for the late spring or early summer of 2020. The Space Launch System program has implemented a building block approach for dynamic model validation. The modal test of the Mobile Launcher is an important part of this building block approach in supporting the integrated vehicle modal test since the Mobile Launcher will serve as a structurally dynamic test fixture whose modes will couple with the modes of the Exploration Mission ? 1 test vehicle. The Mobile Launcher modal test will further support understanding the structural dynamics of the Mobile Launcher and SLS during rollout to the launch pad, which will play a key role in better understanding and prediction of the rollout forces acting on the launch vehicle. The Mobile Launcher modal test is currently scheduled for the summer of 2019. Due to a very tight modal testing schedule, this Mobile Launcher modal pretest analysis has been performed to ensure there is a high likelihood of being able to successfully complete the modal test (i.e. identify the primary target modes) using the planned instrumentation, shakers, and excitation types. This paper will discuss this Mobile Launcher modal pretest analysis and the unique challenges faced due to the Mobile Launcher's size and weight, which are typically not faced when modal testing aerospace structures.

NASA launched the Space Radar Laboratory (SRL) on the two space shuttle missions of “Endeavor” in April and October of 1995. The purpose of these missions was to assess the utility of Shuttle Imaging Radar (SIR-C/X-SAR) for applications in geology, hydrology, agriculture, forestry, desert studies, oceanography and subsurface mapping. The data coverage for the Kingdom of Saudi Arabia from the two missions was processed and analyzed for their ability to show surface and subsurface expressions of drainage channels, or wadis. The processing of the images included removal of speckle, merging of radar with optical Landsat imagery, and color compositing for optimum contrast. The evaluation was carried out at two sites in the Nafud Al-Mazhur and in the southern margin of the Rub’al Khali. Results indicate that radar imagery has the potential to detect old river beds (wadis) buried under a thin cover of sand. It is therefore anticipated that the radar data will be useful in enhancing the present understanding of the hydrogeology and paleo-climate of the Arabian Peninsula.

In 2009 I had the good fortune to fly on a long duration space mission. With two crewmates, I launched aboard a Russian Soyuz rocket from the Baikonur Cosmodrome in Kazakhstan. When our spacecraft reached orbit nine minutes later, we were traveling at a speed of 28,000 kilometers per hour through an environment devoid of air, water and anything familiar. Two days later we rendezvoused with the International Space Station (ISS) at an altitude of 350 km. As our Soyuz vehicle docked with the Station, we began an incredible space odyssey as members of the ISS Expedition 20/21 crew. This Expedition marked the first time that the ISS hosted a permanent crew of six. My international crewmates (from Russia, the United States, Japan and Belgium) and I performed an unprecedented amount of multidisciplinary research (Figure 1). We also performed complex robotic operations, spacewalks, and maintenance and repair work of Station systems and payloads (Figure 2). Figure 1: European astronaut Frank De Winne performs echocardiography on Robert Thirsk, MDCM. This experiment investigated cardiovascular adaptation to weightlessness. Figure 2: Robert Thirsk, MDCM, performs maintenance on the Station's Water Recovery System. This recycling system processes waste water and crew urine into potable water. Six months later my Soyuz crewmates and I undocked from the Station and landed back in Kazakhstan. During our stay in space, we completed 3,000 orbits of the Earth and traveled 125,000,000 km. It was truly an odyssey. This ISS expedition as well as my earlier Space Shuttle mission have enriched me in ways I can never fully explain. I often reflect on the career path that took me from medicine to the cosmos. To some of my medical colleagues, this path seems incongruous. They ask, "What does the practice of medicine have in common with space exploration?". In the following paragraphs, I describe the astronaut profession and its commonalities with medicine. Astronaut training is certainly a transformative experience and the spaceflight environment is alien to anything in the clinical world. However, a career transition to space exploration after investing so much time and effort in a medical career is not unusual. A well-trained astronaut exhibits many of the same knowledge, skills and professional attributes of an exemplary physician. Indeed, a medical background forms an excellent foundation for a career in astronautics.

With an initial requirement to make observations a minimum of 5-10 years, Hubble Space Telescope (HST) has continued to operate well for 30 years. It has relied upon five servicing missions to repair and replace essential components. Since the final Space Shuttle mission 10 years ago it has avoided major breaks in its operation, with the only serious effects of ageing in space being a progressive deterioration in the performance of the gyroscopes and sensitivity of the instrument detectors. A number of factors were important in making HST a scientific landmark. Ground-breaking discoveries have been made with HST----the most important being the discovery of cosmic acceleration. When HST operation ceases future observations in space should be assured with successful operation of major missions now planned by NASA, ESA, and the China and Japanese Space Agencies., 8 pages, 3 figures

On January 16, 2004, NASA Administrator Sean O’Keefe announced his decision to cancel the Hubble Space Telescope (HST) Servicing Mission (SM4) by the Space Shuttle. SM4 was to have inserted two new instruments, the Wide Field Camera 3 and the Cosmic Origins Spectrograph, at the same time replacing the batteries and gyroscopes, extending Hubble’s lifetime to 2010. The decision resulted in a strong reaction among some members of Congress, the HST science community, and the general public, because it would likely leave the telescope inoperable by 2007, years before its full lifetime and well before the James Webb Space Telescope (JWST) would be launched. In the immediate aftermath of his decision to cancel the final servicing mission, Administrator O’Keefe requested an independent study be undertaken by the author in his role as NASA Chief Historian, in order to document in detail the events that led to the cancellation decision. What follows is a history of that decision and its aftermath, completed December 17, 2004, as well as an Epilogue added in 2012 describing the reversal of O’Keefe’s decision by NASA Administrator Michael Griffin.

A total of 11,057 days (or 30 years, 3 months and 9 days) elapsed between Dan Brandenstein’s calls to Columbia during the STS-1 launch on April 12, 1981, and the final conversations between the crew of Atlantis and Shannon Lucid a few hours before STS-135 landed on July 21, 2011. It was a generation that encompassed the whole operational phase of the American Space Shuttle Program, one which members of the Class of 1978 had both witnessed first-hand and actively participated in. Their contributions began well before that first departure from the launch pad at LC-39A and continued with the International Space Station (ISS) for some years after the final wheelstop of Atlantis on Runway 15 at the Shuttle Landing Facility (SLF).

A new algorithm capable of guiding an orbiter glider to a target point with a prescribed alignment and descent path angle is presented. This algorithm can initiate Terminal Area Energy Management (TAEM) before reaching steady state and perform the Final Approach and Landing (FA&L). During TAEM, runway alignment is done through a moving virtual target derived from steady state, while during FA&L, a transient (or flare) is used to reach the extremely shallow descent path angles. All decisions are made dynamically relying solely on local information (position, speed, attitude, and atmospheric parameters), and all structural limits of the glider are respected at all times. As a proof of concept, a Space Shuttle return flight is simulated. For a large multitude of initial conditions and targets, the algorithm is able to consistently deliver distance errors below 19 m (transverse errors below 4 m), alignment errors below $$1^{\circ }$$ , descent path angles at the intended $$-\,2^{\circ }$$ , and vertical descent speeds below 8.5 m/s with control time intervals of 0.1 s.

Animal research aboard the Space Shuttle and International Space Station has provided vital information on the physiological, cellular, and molecular effects of spaceflight. The relevance of this information to human spaceflight is enhanced when it is coupled with information gleaned from human-based research. As NASA and other space agencies initiate plans for human exploration missions beyond low Earth orbit (LEO), incorporating animal research into these missions is vitally important to understanding the biological impacts of deep space. However, new technologies will be required to integrate experimental animals into spacecraft design and transport them beyond LEO in a safe and practical way. In this communication, we propose the use of metabolic control technologies to reversibly depress the metabolic rates of experimental animals while in transit aboard the spacecraft. Compared to holding experimental animals in active metabolic states, the advantages of artificially inducing regulated, depressed metabolic states (called synthetic torpor) include significantly reduced mass, volume, and power requirements within the spacecraft owing to reduced life support requirements, and mitigated radiation- and microgravity-induced negative health effects on the animals owing to intrinsic physiological properties of torpor. In addition to directly benefitting animal research, synthetic torpor-inducing systems will also serve as test beds for systems that may eventually hold human crewmembers in similar metabolic states on long-duration missions. The technologies for inducing synthetic torpor, which we discuss, are at relatively early stages of development, but there is ample evidence to show that this is a viable idea and one with very real benefits to spaceflight programs. The increasingly ambitious goals of world's many spaceflight programs will be most quickly and safely achieved with the help of animal research systems transported beyond LEO; synthetic torpor may enable this to be done as practically and inexpensively as possible.

Spaceflight studies offer a unique opportunity to examine the impact of gravity on developing motor skills. Previously, we reported that young rats experiencing microgravity in low Earth orbit (LEO) beginning on postnatal day (P)14 showed impaired swimming, walking, and surface righting after returning to 1 g, with immature motor skills persisting until adulthood. Here, we report on post-flight surface righting and swimming of rats experiencing spaceflight from P7 or P8. Litters with dams were flown aboard a space shuttle Space Transportation System (STS) 9-day (NIH-R3, STS-72) or 16-day mission (Neurolab, STS-90). Flight rats from both missions showed significantly fewer mature, age-appropriate righting tactics after landing compared to ground controls. Flight rats also had a steeper body angle while floating in the water before swimming, started swimming sooner, and swam faster. The effects on surface righting persisted for the duration of behavior tests (6 days [9-day mission] or 23 days [16-day mission]), after landing. Differences in pre-swimming behavior resolved by return day (R)2, and differences in swimming speed and posture resolved by R10. These data suggest that exposure to microgravity at a young age prevents the normal development of surface righting and that the normal development of swimming can recover if animals return from LEO by P16 or P24. These findings lend additional support to the existence of a critical period of development for motor function. However, studies are needed with improved housing during spaceflight to ensure that maternal offspring behavior is not disrupted, as was observed during the Neurolab mission.

There is limited information regarding the effects of spaceflight on the anatomical configuration of the brain and on cerebrospinal fluid (CSF) spaces.We used magnetic resonance imaging (MRI) to compare images of 18 astronauts' brains before and after missions of long duration, involving stays on the International Space Station, and of 16 astronauts' brains before and after missions of short duration, involving participation in the Space Shuttle Program. Images were interpreted by readers who were unaware of the flight duration. We also generated paired preflight and postflight MRI cine clips derived from high-resolution, three-dimensional imaging of 12 astronauts after long-duration flights and from 6 astronauts after short-duration flights in order to assess the extent of narrowing of CSF spaces and the displacement of brain structures. We also compared preflight ventricular volumes with postflight ventricular volumes by means of an automated analysis of TNarrowing of the central sulcus occurred in 17 of 18 astronauts after long-duration flights (mean flight time, 164.8 days) and in 3 of 16 astronauts after short-duration flights (mean flight time, 13.6 days) (P0.001). Cine clips from a subgroup of astronauts showed an upward shift of the brain after all long-duration flights (12 astronauts) but not after short-duration flights (6 astronauts) and narrowing of CSF spaces at the vertex after all long-duration flights (12 astronauts) and in 1 of 6 astronauts after short-duration flights. Three astronauts in the long-duration group had optic-disk edema, and all 3 had narrowing of the central sulcus. A cine clip was available for 1 of these 3 astronauts, and the cine clip showed upward shift of the brain.Narrowing of the central sulcus, upward shift of the brain, and narrowing of CSF spaces at the vertex occurred frequently and predominantly in astronauts after long-duration flights. Further investigation, including repeated postflight imaging conducted after some time on Earth, is required to determine the duration and clinical significance of these changes. (Funded by the National Aeronautics and Space Administration.).

Recovered artifacts from the Space Shuttle Columbia provide a unique opportunity to examine a broad spectrum of materials exposed to the extreme environment of earth re-entry. The degradation states of these components offer a unique perspective into material behavior in this highly reactive environment. The crew module X-links, which are composed of Ti-6Al-4V and provided structural support to the crew module within the fuselage, exhibit evidence of both oxidation and combustion phenomena. The conditions supporting ignition and combustion of bulk metals are not fully understood, due to the many compounding factors affecting variable oxidation behavior of metals. Materials characterization of the Columbia X-links will yield further insight into the discrimination between the oxidation, ignition, and combustion response of titanium alloys. Widespread use of titanium alloys in space vehicles warrants a thorough characterization of their potential failure modes to help ensure the safe and reliable operation of future spaceflight vehicles. Initial microstructural state of the X-links is assessed, and affected material exhibits microstructural gradients dependent on vehicle orientation. Three distinct microstructural states were observed across the length of the X-links, according to proximity of aggravated flow.

The objective of this study is to assess the performance of chemical kinetic model for heat transfer acting on the hypersonic vehicle. Four different chemical kinetic models, including Dunn Kang model, Gupta model, Park 87 model and Park 91 model, are implemented and assessed. The differences among these models are obvious, consisting of the elementary reactions, the method of evaluating backward rate coefficients and chemical kinetic rates. In order to further investigate the performance of these models for hypersonic aeroheating prediction, three typical test cases are employed: (1) the heat transfer acting on ELECTRE vehicle at Mach number 13, (2) the heat transfer acting on Apollo command module at Mach number 20.5 and (3) the heat transfer acting on Space Shuttle Orbiter at Mach number 20.985. Firstly, the behaviors of these models are demonstrated by comparing the numerical results with the flight data or experimental data in detail. Secondly, the reasons for the discrepancies of heat fluxes computed with these models are discussed. The results reveal that the heat fluxes acting on ELECTRE vehicle and the head of Space Shuttle Orbiter predicted by these chemical kinetic models are in good consistency and agree well with the flight or experimental data. With the increasing of complexity of the vehicle’s geometry, the differences of heat flux, especially the peak heat flux, become more and more obvious, and the maximum difference among them may exceed 25%. The numerical results also indicate that the numerical prediction of heat transfer acting on complicated geometry exhibits a relatively strong sensitivity to the choice of chemical kinetic models. The difference of chemical kinetic rates and the complicated flow structure in the flowfield may be the primary reasons for the heat flux discrepancies.

This paper considers human reliability analysis (HRA) for long-duration space missions. HRA has previously been used in the space program to support ground-based operations, Space Shuttle and International Space Station missions. New missions, such as a prospective mission to Mars, present new contexts for human spaceflight, including longer distances and durations, and different gravity levels. For HRA to be used to inform and prevent hazards, new research and data gathering are needed to understand the psychological and physiological aspects of astronautics. This paper outlines several areas of research that would support HRA for long-duration spaceflight. HRA methods must be adapted for space, which requires new data to inform and validate human error categorization and quantification.

This chapter focuses on the effects of weightlessness on the structural integrity of bone, muscle, and connective tissue, with an emphasis on the biomechanical changes, both as cause and effect. With regard to the human, the dominant spaceflight factor influencing physiological changes is weightlessness. Given that functional loading is known to increase bone and muscle mass, loss of bone and muscle integrity are an expected consequence of space flight where such loading is diminished. Losses of muscle strength and volume have been measured after 5- to 16-day Space Shuttle missions. Increased urinary excretion of calcium indicated increased bone resorption during short duration Gemini, Apollo, and Space Shuttle missions. Longer duration Skylab and Mir missions were required to detect changes in bone density. These observed changes raised early concern that muscle atrophy and bone loss could increase risks of long-term space flight to unacceptable levels unless adequate countermeasures were developed to prevent the losses.

This chapter is intended as an overview of the basic body of information required of the space medicine practitioner to understand the adaptive and operational environment of space flyers. An understanding of the physiologic and medical implications of this environment enables the practitioner to provide optimal medical support. This information should provide a foundation for discussions of physiologic and psychological processes associated with space flight and allow the response to medical events to be placed in proper context. Understanding this context also prepares the spaceflight surgeon to serve as a consultant in space program organizations, where human needs must fit into mission parameters and priorities.

This chapter discusses three case studies in modulus-limited design. The first case study is on selecting materials for racing yacht masts. A good way to compare the performance of different materials in this type of application is to look at the mechanics of a cantilever beam in bending. The second case study is on designing a mirror for a large reflecting telescope. In simple terms, the mirror is an inert backing (of low-expansion glass, weighing 14.5 tons) for a very thin layer of vapor-deposited aluminum, 100 nm thick. Before coating, it is ground and polished to the shape of a parabola of revolution. The final dimensions must be incredibly accurate, otherwise the optical image seen through the telescope may not be sharp. The third case study is on the Challenger space shuttle disaster. On 28 January 1986, the U.S. space shuttle Challenger caught fire and broke up 73 seconds after lift-off. Together with the break-up of the space shuttle Columbia during re-entry on 1 February 2003, these are the worst accidents in the history of space travel. The circumstances of the disaster are well known and are extensively documented in the report of the Presidential Commission (the Rogers report) and many other sources.

The process of investigating spacecraft accidents rests on the lessons of more than 60 years of aircraft crash investigation. There was little need for such skills in the early years of US spaceflight. This changed dramatically in 1986 with the loss of the Space Shuttle Challenger and was perpetuated by the loss of Space Shuttle Columbia in 2003. There have been other fatal accidents involving spacecraft and many near misses. With plans that include continued manning of the International Space Station (ISS); multiple new vehicles; exploration of the moon, asteroids, and Mars; and a vigorous civilian presence in space, it is certain that there will be a need for such investigations in the future. Medical investigators, human factors specialists, and flight surgeons will have essential roles. Their activities will concern human factors, physiology, and the assessment of human survivability – all aimed at preventing future injury and death. The necessary “forensic analysis” will be difficult, both emotionally and physically, and will not always be appreciated, supported, or understood by those uninvolved with the process. Outcome conclusions must be “evidence based” and oriented toward gaining information that will contribute to answering specific questions relevant to future practices and designs.

The space manipulator which has advantages of high dexterity and universality, is used to the space capturing usually. According to the different types of mechanical interfaces of targets, the on orbit capturing operation includes capturing of cooperative target and capturing of uncooperative target. The performances of the famous large space manipulators named space shuttle remote manipulator system (SRMS), the space station remote manipulator system (SSRMS) and the Europe robotic arm (ERA) are reviewed and studied respectively. Moreover, the space manipulators being developed by China for space station is also surveyed. Based on the performance analysis of the large space manipulators and end-effectors, which are adapted to the construction and daily maintenance for the large space structure such as the space station, the basic requirements of large misalignment tolerance capability, soft capturing capability and hard docking capability for the end-effector of large space manipulator are proposed in this paper. According to these requirements, the capture mechanism and methods that can enable the end-effector to have the capability of misalignment tolerance and soft capturing are presented. The development trend and key technologies of the large space manipulators and the end-effectors are also reviewed.

Designed for the launch and subsequent on-orbit maintenance by astronauts and the Space Shuttle, the Hubble Space Telescope presented a unique and challenging set of flight operations issues during six missions between 1990 and 2009. Starting with the launch in 1990 and for the following three servicing missions, the solar arrays represented an unanticipated and significant operational challenge for the crews and the flight operations teams. Modified first-generation solar arrays were installed on Servicing Mission 1 in 1993 to correct for a jitter introduced into the telescope’s control system by the design of the original solar arrays. However, although the jitter was improved, the modified solar arrays introduced additional issues for the second servicing mission, Space Transportation System 82, due to the existence of a significant static twist. New flight operations techniques had to be developed to monitor the condition and protect the integrity of the solar arrays. It was not known until after Hubb...

After an 11-month review, a new National Space Policy was announced by President Reagan on July 4, 1982. That policy did not reflect major changes to existing NASA programs, but placed increased emphasis on private sector and military space activities. A lasting impact of the policy was to create a Senior Interagency Group for Space [SIG (Space)], operating under the auspices of the National Security Council and having as members heads of major executive branch agencies or their deputies. SIG (Space) was to be the forum for developing Reagan administration space policy. President Reagan announced the new policy as he watched space shuttle orbiter Columbia land at Edwards Air Force Base in the California high desert after its fourth flight and as the transport plane carrying the second orbiter, Challenger, took off, headed to the Kennedy Space Center to enter service.

In the aftermath of the Challenger accident, and particularly after the reviews by the Rogers Commission and others assessing the reality of the shuttle’s operations and National Aeronautics and Space Administration’s (NASA’s) less-than-stellar performance in managing them, it became clear that there was a high degree of self-delusion in the way the shuttle had been perceived. Rather than a vehicle delivering on the promises that NASA had made to Richard Nixon in 1972, claiming that the space shuttle would “revolutionize transportation into near space by routinizing it” and would “take the astronomical costs out of astronautics,” the shuttle was revealed to be a vehicle that was expensive and difficult to operate safely. The stage was thus set for a debate over post-Challenger launch policy. That seven-month debate proved very contentious, with its focal points being both whether to build a new shuttle orbiter to replace Challenger and what role the shuttle would play in future U.S. launch policy.

Performance of astronaut pilots during space shuttle landing was degraded after a few weeks of microgravity exposure, and longer-term exposure has the potential to impact operator proficiency during critical landing and post-landing operations for exploration-class missions. Full-motion simulations of operationally-relevant tasks were utilized to assess the impact of long-duration spaceflight on operator proficiency in a group of 8 astronauts assigned to the International Space Station, as well as a battery of cognitive/sensorimotor tests to determine the underlying cause of any post-flight performance decrements. A ground control group (N = 12) and a sleep restriction cohort (N = 9) were also tested to control for non-spaceflight factors such as lack of practice between pre- and post-flight testing and fatigue. On the day of return after 6 months aboard the space station, astronauts exhibited significant deficits in manual dexterity, dual-tasking and motion perception, and a striking degradation in the ability to operate a vehicle. These deficits were not primarily due to fatigue; performance on the same tasks was unaffected after a 30-h period of sleep restriction. Astronauts experienced a general post-flight malaise in motor function and motion perception, and a lack of cognitive reserve apparent only when faced with dual tasks, which had recovered to baseline by four days after landing.

Ground to air temperature gradients drive the creation and evolution of optical turbulence in the atmospheric boundary layer. Ground composition is an important factor when observing and measuring the generated optical turbulence. Surface roughness and thermal characteristics influence the formation of optical turbulence eddies. The Space Shuttle Landing Facility (SLF) at The Kennedy Space Center offers a unique opportunity to measure the generation and evolution of these turbulent eddies, while also providing a temperature gradient “Step Function” after which turbulence evolution can be analyzed. We present the analysis of data collected on the SLF during May of 2018. Mobile towers instrumented with sonic anemometers are used to examine the statistics of turbulent eddies leaving the increased heat gradient of the runway. This data is compared to an optical scintillometer and other local weather station data. Point and path average Cn2 data are calculated and attention is given to turbulence spectrum as a function of height above ground.

This paper describes how the Orion program is utilizing the Thermal Protection System (TPS) experience from the Apollo and Space Shuttle programs to reduce program risk and improve affordability to meet NASA's future manned exploration missions. The Orion program successfully completed the Exploration Flight Test (EFT-1) mission in 2014 and is currently assembling, integrating, and testing the next spacecraft for the Exploration Mission (EM-1) to meet the flight test objectives of an unmanned orbital mission to the moon and return to earth in 2019. The Orion spacecraft production operations are located in the Neil Armstrong Operations and Checkout (O&C) facility at the Kennedy Space Center (KSC) providing an affordable and seamless delivery approach of vehicles directly to the launch site eliminating spacecraft transportation and additional checkout testing. Innovative vehicle design, manufacturing and test operations approaches are maturing and evolving with each Orion vehicle build to support the challenging NASA exploration mission requirements beyond Low Earth Orbit (LEO) while reducing program cost and schedule impacts. An example of Orion's evolution is the incorporation of an improved heat shield design, assembly and testing approach to meet the higher re-entry velocities for a lunar return for the EM-1 mission. The EFT- 1 heat shield was based on the Apollo heat shield manufacturing processes and was assembled at a supplier location and then transported to KSC for final integration. The EM-1 heat shield is now manufactured, assembled, tested, and installed into the spacecraft at the O&C facility reducing program cost and production schedules. The transition of the Space Shuttle TPS capabilities has enabled Orion to provide a human rated capsule design using proven materials and processes established over years of orbiter re-entry missions. The Orion Crew Module (CM) TPS configuration is derived from the Apollo CM approach utilizing improved materials and processes developed from the Space Shuttle program. The Orion EFT-1 heat shield utilized the Avcoat ablative material from Apollo which was injected into a honeycomb substrate and has been updated for EM-1 incorporating a block configuration bonded to a composite shell structure. This approach utilizes the proven Avcoat material for the heat shield ablator and is utilizing derived bonding and inspection methods and techniques from the Space Shuttle tile experience. The Orion back shell TPS configuration is based on Space Shuttle tile designs using proven tile materials and coatings. The Orion forward bay cover utilizes the high temperature tiles similar to the back shell tiles and low temperature blankets derived from the Space Shuttle program reducing weight impacts. Space Shuttle Multi-Layer Insulation (MLI) is installed in the Orion capsule to control the interior temperature environment providing a light weight design. These TPS design approaches have performed successfully on the Orion first flight test on EFT-1 and are incorporated in the configuration for the next flight test for EM-1. Completion of these two flight tests will certify the TPS for the Orion program for human rated exploration missions and has reduced the development cost to the Orion program. In addition to transitioning the Space Shuttle TPS design configurations to Orion, the supporting manufacturing infrastructure, manufacturing processes, and inspection methods are also incorporated into the Orion assembly operations at KSC. This has avoided significant startup schedule and costs impacts of new capabilities and development of support operations necessary to fabricate, install, inspect, and validate the TPS installations for the Orion spacecraft. The Thermal Protection System Facility (TPSF) which supported the Space Shuttle program provides the heat shield Avcoat blocks and the back shell AETB-8 tiles for Orion program. Extending the existing Space Shuttle TPS operations at KSC provides onsite support to the Orion spacecraft assembly operations. A significant benefit to the Orion program is the transition of the Space Shuttle technician work force at KSC. This highly skilled workforce was able to transition to the Orion program and immediately support the TPS installation operations. They brought with them the human rated manufacturing and assembly operations culture that was critical to the Space Shuttle success avoiding the retraining cost and schedule impacts of a new workforce to Orion. The technician skills certification program from the Space Shuttle was found to be compatible with the Lockheed Martin technician certification programs enabling a seamless training process utilizing process similarity avoiding the cost of retraining the work force to Orion standards. The existing workforce is certificated for multiple processes enabling reassignment of technicians to other tasks in the Orion AI&P operations reducing the overall touch labor manpower requirements. Additional benefits of using the Space Shuttle workforce is the incorporation of the lessons learned from Space Shuttle processes to improve the Orion TPS processes. This has resulted in a continuous evolution of TPS processes to improve the producibility and reduce the program cost for the TPS for the Orion program. Transitioning the Apollo and Space Shuttle TPS designs, processes, and technician workforce has been instrumental in enabling Orion to successfully meet the program challenges for NASA's exploration missions of the future.

In recent years, microwave methods for nondestructive testing (NDT) as an alternative to conventional ultrasound techniques, are becoming more common in the aerospace industry. Microwave sensors are applied to the examination of composite materials and structures which have many advantages over, and are replacing, traditional metal alloys. Composites typically have a better strength-to-weight ratio, and can withstand adverse weather conditions and corrosive environments. Such materials include polyurethane foam (PUF) insulation, silica fiber tiles (which were used for thermal protection in the American Space Shuttles and the Soviet spacecraft “Buran”), and honeycomb fiberglass which is frequently used in airplanes. The American and Soviet reusable launch system, and other space rockets, which fly on cryogenic fuel components, use PUF insulation to prevent both boiling-away of these components during prelaunch preparation, and the formation of surface ice which can damage the construction. The Space Shuttle Columbia catastrophe showed that PUF insulation coatings require diligent quality control during manufacture and use. Due to the high level of acoustic wave attenuation in porous composites, conventional ultrasonic diagnostic methods are ineffective for these materials, and holographic subsurface radar may be the best alternative. This work describes the development of a special experimental setup consisting of a vector network analyzer, used for signal generation and reception, and an electromechanical scanner which precisely moves the studied samples. The operating frequency band of the vector network analyzer allows experiments across a wide waveband up to 24 GHz. For registration and reconstruction of complex multifrequency microwave holograms, specialized software was developed. The software has special functions for improving quality of reconstructed holograms and suppressing reflections from samples borders. The setup was used for investigation of the operating frequency influence on subsurface imaging results. All of the samples contained intentional model defects typical of composite materials. Comparison of blind experimental imaging results for these test samples with maps of defects (revealed post-experiment) showed good agreement, proving effective detection and delineation of hidden flaws.

When we send humans to search for life on other planets, we'll need to know what we brought with us versus what may already be there. To ensure our crewed systems meet planetary protection requirements — and to protect our science from human contamination — we'll need to assess whether microorganisms may be leaking or venting from our spacecraft. Microbial sample collection outside of a pressurized spacecraft is complicated by temperature extremes, low pressures that preclude the use of laboratory standard (wetted) swabs, and operation either in bulky spacesuits or with robotic assistance. A team at the National Aeronautics and Space Administration (NASA) recently developed a swab kit for use in collecting microbial samples from the external surfaces of crewed spacecraft, including spacesuits. The Extravehicular Activity (EVA) Swab Kit consists of a single swab tool handle and an eight-canister sample caddy. The design team minimized development cost by re-purposing a heritage Space Shuttle tile repair handle that was designed to quickly snap into different tool attachments by engaging a mating device in each end effector. This allowed the tool handle to snap onto a fresh swab end effector much like popular shaving razor handles can snap onto a disposable blade cartridge. To disengage the handle from a swab, the user performs two independent functions, which can be done with a single hand. This dual operation mitigates the risk that a swab will be inadvertently released and lost in microgravity. Each swab end effector is fitted with commercially available foam swab tips, vendor-certified to be sterile for Deoxyribonucleic Acid (DNA). A microbial filter installed in the bottom of each sample container allows the container to outgas and re-pressurize without introducing microbial contaminants to internal void spaces. Extensive ground testing, post-test handling, and sample analysis confirmed the design is able to maintain sterile conditions as the canister moves between various pressure environments. To further minimize cost, the design team acquired extensive ground test experience in a relevant flight environment by piggy-backing onto suited crew training runs. These training runs allowed the project to validate tool interfaces with pressurized EVA gloves and collect user feedback on the tool design and function, as well as characterize baseline microbial data for different types of spacesuits. In general, test subjects found the EVA Swab Kit relatively straightforward to operate, but identified a number of design improvements that will be incorporated into the final design. Although originally intended to help characterize human forward contaminants, this tool has other potential applications, such as for collecting and preserving space-exposed materials to support astrobiology experiments.

From exoskeleton to the remote teleoperation, the development of patents related to space exploration later provided significant opportunities in many fields of sciences such as medicine, robotics, underwater expeditions, hazardous work, industrial assembly, and even during everyday work as mowing. Antal K. Bejczy the Hungarian born innovator was working on the technical part of these projects, under his work at JPL the technology turned over to private industry, like the remote control. Bejczy and the college's evaluation report was used by the Johnson Space Center Space Shuttle Arm's research in 1984. The focus of the report from 1982 was the Evaluation of smart sensor displays for multidimensional precision control of Space Shuttle remote manipulator.

Since the Space Shuttle retirement in 2011, the National Aeronautics and Space Administration (NASA) has lost its ability to provide comparable up and down mass to the International Space Station (ISS). One consequence of reduced mass exchange has been the extended operational life cycle of the Space Suit, known as the Extravehicular Mobility Unit (EMU), and extended periods between ground servicing. In 2013, NASA suffered a near-fatal release of water inside the EMU, leading a full review of the safety, reliability and maintenance practices of the EMU. NASA's mishap investigation board's final report determined that the water-inthe-helmet mishap was the unfortunate result of a series of extenuating events. This paper examines if these events are part of a wider trend of more frequent failures as a result of the extended maintenance cycle. EMU usage data is compared using both statistical hypothesis tests and reliability growth models to show that the incidence of failures for the current maintenance approach is not increasing over previous maintenance approaches. It is thus concluded that the mean time between failures of the EMU cannot be shown to change, but that the changing of the maintenance model due to the space shuttle retirement introduced high severity failure modes that were not adequately assessed due to a normalization of certain failures.

The environment on the International Space Station (ISS) includes a variety of potential physiologic stressors, including low gravity, elevated exposure to radiation, confined living and working quarters, a heavy workload, and high public visibility. This retrospective study examined medication use during long-duration spaceflights (>30 d). Medication records from 24 crewmembers on 20 missions longer than 30 d over a 10 yr period were examined for trends in usage rates, efficacy, and indication, as well as adverse event quality, frequency, and severity. Results were compared with those from crewmembers on shorter space shuttle missions (>16 d) and other reports of medication use by healthy adults. The most frequently used medications on the ISS were for sleep problems, pain, congestion, or allergy. Medication use during spaceflight missions was similar to that noted on the Space Shuttle and in adult ambulatory medicine, except that usage of sleep aids was about 10 times higher during spaceflight missions. There were also 2 apparent treatment failures in cases of skin rash, raising questions about the efficacy or suitability of the treatments used. Many spaceflight-related medication uses (at least 10%) were linked to extravehicular activities, exercise protocols, or equipment and operationally driven schedule changes. It seems likely that alterations in spaceflight mission operations (schedule-shifting and lighting) or hardware (extravehicular activity suits and exercise equipment) could reduce the need for a sizable fraction of medication uses.

Analysis of critical conditions on the reusable spacecrafts Columbia (USA), and Buran (Russia) related to defects in insulation and heat-protection coatings have been performed. It is shown that the existing methods of non-destructive testing, including ultrasonics, failed to prevent the disaster of the Space Shuttle Columbia and serious incidents involving the spacecraft Buran during its only flight. A new method for using the holographic subsurface radar RASCAN-5/15000 which reveals the internal defects of the coating was proposed, and experiments on models of thermal insulation coatings were performed. The experimental results were displayed in the form of radar images on which defects in the heat insulation provided a good contrast. The article reflects preliminary study and further efforts are needed to improve resolution of the technology.

The Shuttle Hypervelocity Impact Database documents damage features on each Orbiter from micrometeoroids (MM) and orbital debris (OD). Data is divided into tables for crew module windows, payload bay door radiators and thermal protection systems along with other miscellaneous regions. The database contains nearly 3000 records, with each providing impact feature dimensions, location on the vehicle and relevant mission information. Additional detail on the type and size of particle that produced the damage site is provided when sampling data and definitive spectroscopic analysis results are available. Relationships assumed when converting from observed feature sizes in different shuttle materials to particle sizes will be presented.

Large temperature gradients are a known source of strong atmospheric turbulence conditions. Often times these areas of strong turbulence conditions are also accompanied by conditions that make it difficult to conduct long term optical atmospheric tests. The Shuttle Landing Facility (SLF) at the Kennedy Space Center (KSC) provides a prime testing environment that is capable of generating strong atmospheric turbulence yet is also easily accessible for well instrumented testing. The Shuttle Landing Facility features a 5000 m long and 91 m wide concrete runway that provides ample space for measurements of atmospheric turbulence as well as the opportunity for large temperature gradients to form as the sun heats the surface. We present the results of a large aperture LED scintillometer, a triple aperture laser scintillometer, and a thermal probe system that were used to calculate a path averaged and a point calculation of Cn2. In addition, we present the results of the Plenoptic Sensor that was used to calculate a path averaged Cn2 value. These measurements were conducted over a multi-day continuous test with supporting atmospheric and weather data provided by the University of Central Florida.

Human spaceflight is an inherently risky endeavor. From the first missions to explore space to recent problems on the International Space Station, NASA has faced many challenges and has relied on creative and innovative ways to overcome issues, complete the mission, and ensure the safe return of crew members. However, over the past 50 years, NASA has also experienced three fatal accidents resulting in the loss of seventeen astronauts — the Apollo 1 fire on the launch pad, the Space Shuttle Challenger explosion during ascent, and the destruction of the Space Shuttle Columbia during entry. Studying the lessons learned from the Challenger and Columbia accidents, as well as similarities in those two tragedies, provides a prospective of cultural, organizational, and management failures that can occur in any engineering organization managing extremely complex systems operated in high risk environments.

Current NASA Human Mars architectures require delivery of approximately 20 metric tons of cargo to the surface in a single landing. A proposed vehicle type for performing the entry, descent, and landing at Mars associated with this architecture is a rigid, enclosed, elongated lifting body shape that provides a higher lift-to-drag ratio (L/D) than a typical entry capsule, but lower than a typical winged entry vehicle (such as the Space Shuttle Orbiter). A rigid Mid-L/D shape has advantages for large mass Mars EDL, including loads management, range capability during entry, and human spaceflight heritage. Previous large mass Mars studies have focused more on symmetric and/or circular cross-section Mid-L/D shapes such as the ellipsled. More recent work has shown performance advantages for non-circular cross section shapes. This paper will describe efforts to design a rigid Mid-L/D entry vehicle for Mars which shows mass and performance improvements over previous Mid-L/D studies. The proposed concept, work to date and evolution, forward path, and suggested future strategy are described.

Those eight short words aptly sum up the excitement, relief and satisfaction for an astronaut at finally being able to ply their trade after years of training. As NASA astronauts, the achievements of each of the seventeen remaining members of the NASA Class of ‘66 and the seven former MOL Class of ‘69 are impressive, though the time between selection and flying their first mission into space varied considerably. For Dick Truly, the only member of the first MOL selection of November 1965 to make it into orbit, it was a sixteen year wait before finally leaving the launch pad. His MOL colleagues who had moved across to NASA with him in 1969 also endured a long wait for a flight. Over a two-year period, between April 1981 and April 1983, each would make their maiden spaceflight aboard the Space Shuttle, with six of the seven going on to complete their second, third or fourth flights by October 1985.

Written four decades before the Shuttle flew to Mir, these words accurately forecast the need to develop a regular resupply system and logistics infrastructure to keep a station in operation. In 1978 the Soviets introduced the first unmanned variant of their Soyuz, named Progress, which routinely supplied cargo, consumables, and propellants to the Salyut 6, 7, and Mir stations, and is today servicing the ISS. During the nearly twenty years the ISS has been in space, a variety of unmanned cargo craft have supplemented the capabilities of the Space Shuttle to stock it with supplies and new hardware and to remove unwanted items. But none of these spacecraft has been able to match the great volume of the Orbiter’s payload bay, nor its capacity to transport an array of different logistics owing to its particular portfolio of resources.

The U.S. Space Shuttle fleet was originally intended to have a life of 100 flights for each vehicle, lasting over a 10-year period, with minimal scheduled maintenance or inspection. The first space shuttle flight was that of the Space Shuttle Columbia (OV-102), launched April 12, 1981. The disaster that destroyed Columbia occurred on its 28th flight, February 1, 2003, nearly 22 years after its first launch. In order to minimize risk of losing another Space Shuttle, a probabilistic life and reliability analysis was conducted for the Space Shuttle rudder/speed brake actuators to determine the number of flights the actuators could sustain. A life and reliability assessment of the actuator gears was performed in two stages: a contact stress fatigue model and a gear tooth bending fatigue model. For the contact stress analysis, the Lundberg-Palmgren bearing life theory was expanded to include gear-surface pitting for the actuator as a system. The mission spectrum of the Space Shuttle rudder/speed brake actuator was combined into equivalent effective hinge moment loads including an actuator input preload for the contact stress fatigue and tooth bending fatigue models. Gear system reliabilities are reported for both models and their combination. Reliability of the actuator bearings was analyzed separately, based on data provided by the actuator manufacturer. As a result of the analysis, the reliability of one half of a single actuator was calculated to be 98.6 percent for 12 flights. Accordingly, each actuator was subsequently limited to 12 flights before removal from service in the Space Shuttle.