Engineering topics
Rajulu, Sudhakar L.
Publications and source records attributed to Rajulu, Sudhakar L..
Posture Transfer Method on Pre-Scanned Full-body Geometry for Space Architecture Design
No abstract available
Predictive Assessments of Spacesuit Fit: Monte-Carlo Modeling and Analysis
No abstract available
Quantification of In-Flight Physical Changes: Anthropometry and Neutral Body Posture (Body Measures)
No abstract available
A Parametric Model of Shoulder Articulation for Virtual Assessment of Space Suit Fit
Shoulder injury is one of the most severe risks that have the potential to impair crewmembers' performance and health in long duration space flight. Overall, 64% of crewmembers experience shoulder pain after extra-vehicular training in a space suit, and 14% of symptomatic crewmembers require surgical repair (Williams & Johnson, 2003). Suboptimal suit fit, in particular at the shoulder region, has been identified as one of the predominant risk factors. However, traditional suit fit assessments and laser scans represent only a single person's data, and thus may not be generalized across wide variations of body shapes and poses. The aim of this work is to develop a software tool based on a statistical analysis of a large dataset of crewmember body shapes. This tool can accurately predict the skin deformation and shape variations for any body size and shoulder pose for a target population, from which the geometry can be exported and evaluated against suit models in commercial CAD software. A preliminary software tool was developed by statistically analyzing 150 body shapes matched with body dimension ranges specified in the Human-Systems Integration Requirements of NASA ("baseline model"). Further, the baseline model was incorporated with shoulder joint articulation ("articulation model"), using additional subjects scanned in a variety of shoulder poses across a pre-specified range of motion. Scan data was cleaned and aligned using body landmarks. The skin deformation patterns were dimensionally reduced and the co-variation with shoulder angles was analyzed. A software tool is currently in development and will be presented in the final proceeding. This tool would allow suit engineers to parametrically generate body shapes in strategically targeted anthropometry dimensions and shoulder poses. This would also enable virtual fit assessments, with which the contact volume and clearance between the suit and body surface can be predictively quantified at reduced time and cost.
A Parametric Model of Shoulder Articulation for Virtual Assessment of Space Suit Fit
Suboptimal suit fit is a known risk factor for crewmember shoulder injury. Suit fit assessment is however prohibitively time consuming and cannot be generalized across wide variations of body shapes and poses. In this work, we have developed a new design tool based on the statistical analysis of body shape scans. This tool is aimed at predicting the skin deformation and shape variations for any body size and shoulder pose for a target population. This new process, when incorporated with CAD software, will enable virtual suit fit assessments, predictively quantifying the contact volume, and clearance between the suit and body surface at reduced time and cost.
Characterization of Joint Resistance and Performance Degradation of the Extravehicular Mobility Unit Spacesuit: A Pilot Study
No abstract available
Functional Mobility Testing: A Novel Method to Create Suit Design Requirements
This study was performed to aide in the creation of design requirements for the next generation of space suits that more accurately describe the level of mobility necessary for a suited crewmember through the use of an innovative methodology utilizing functional mobility. A novel method was utilized involving the collection of kinematic data while 20 subjects (10 male, 10 female) performed pertinent functional tasks that will be required of a suited crewmember during various phases of a lunar mission. These tasks were selected based on relevance and criticality from a larger list of tasks that may be carried out by the crew. Kinematic data was processed through Vicon BodyBuilder software to calculate joint angles for the ankle, knee, hip, torso, shoulder, elbow, and wrist. Maximum functional mobility was consistently lower than maximum isolated mobility. This study suggests that conventional methods for establishing design requirements for human-systems interfaces based on maximal isolated joint capabilities may overestimate the required mobility. Additionally, this method provides a valuable means of evaluating systems created from these requirements by comparing the mobility available in a new spacesuit, or the mobility required to use a new piece of hardware, to this newly established database of functional mobility.
Mark III Space Suit Mobility: A Reach Evaluation Case Study
A preliminary assessment of the reach envelope and field of vision (FOV) for a subject wearing a Mark III space suit was requested for use in human-machine interface design of the Science Crew Operations and Utility Testbed (SCOUT) vehicle. The reach and view of two suited and unsuited subjects were evaluated while seated in the vehicle using 3-dimensional position data collected during a series of reaching motions. Data was interpolated and displayed in orthogonal views and cross-sections. Compared with unsuited conditions, medio-lateral reach was not strongly affected by the Mark III suit, whereas vertical and antero-posterior reach were inhibited by the suit. Lateral FOV was reduced by approximately 40 deg. in the suit. The techniques used in this case study may prove useful in human-machine interface design by providing a new means of developing and displaying reach envelopes.
Reach Envelope and Field of Vision Quantification in Mark III Space Suit Using Delaunay Triangulation
The Science Crew Operations and Utility Testbed (SCOUT) project is focused on the development of a rover vehicle that can be utilized by two crewmembers during extra vehicular activities (EVAs) on the moon and Mars. The current SCOUT vehicle can transport two suited astronauts riding in open cockpit seats. Among the aspects currently being developed is the cockpit design and layout. This process includes the identification of possible locations for a socket to which a crewmember could connect a portable life support system (PLSS) for recharging power, air, and cooling while seated in the vehicle. The spaces in which controls and connectors may be situated within the vehicle are constrained by the reach and vision capabilities of the suited crewmembers. Accordingly, quantification of the volumes within which suited crewmembers can both see and reach relative to the vehicle represents important information during the design process.
Ergonomic Evaluation of Space Shuttle Light-Weight Seat Lever Position and Operation
During a Shuttle flight in the early part of 1999, one of the crewmembers was unable to operate the backrest lever for the light-weight seat in microgravity. It is essential that the crewmembers are able to adjust this back-rest lever, which is titled forward 2 degrees from vertical during launch and then moved backwards to 10 degrees aft of vertical upon reaching orbit. This adjustment is needed to cushion the crewmembers during an inadvertent crash landing situation. The original Shuttle seats, which had seat controls located on the front left and right sides of the seat, were replaced recently with the new light-weight seats. The controls for these new, seats were moved to the night side with one control at the front and the other at the back. While it was uncertain whether the problem encountered was unique to that crewmember or not it was clear to the personnel responsible for maintaining the Shuttle seats that not knowing the cause of the problem posed a safety concern for NASA. Hence the Anthropometry and Biomechanics Facility (ABF) of the Johnson Space Center was requested to perform an evaluation of the seat controls and provide NASA with appropriate recommendations on whether the seat lever positions and operations should be modified. The ABF designed an experiment to investigate the amount of pull force exerted by subjects, wearing an unpressurized or pressurized crew launch escape suit, when controls were placed in the front and back (on the right side) of the light-weight seat. Single-axis load cells were attached to the seat levers, which measured the maximum static pull forces that were exerted by the subjects. Twelve subjects, six male and six female, participated in this study. Each subject was asked to perform the pull test at least three times for each combination of lever position and suit pressure conditions. The results from this study showed that as a whole (or in general), the subjects were able to pull on the lever at the back position with only about half the amount of force that they were able to exert on the lever at the front position. In addition, the results also showed that subjects wearing the pressurized suit were unable to reach the seat lever when it was located at the back. Furthermore, the pull forces on the front lever diminished about 50 % when subjects wore the pressurized suits. Based on these results from this study, it was recommended to NASA that the levers should not be located in the back position. In addition, further investigation is needed on whether the levers at the front of the seat could be modified or adjusted to increase the leverage for crew members wearing pressurized launch/escape suits.
Evaluation of COSTAR mass handling characteristics in an environment. A simulation of the Hubble Space Telescope service mission
The STS-61 Shuttle mission, which took place in December 1993, was solely aimed at servicing the Hubble Space Telescope (HST). Successful completion of this mission was critical to NASA since it was necessary to rectify a flaw in the HST mirror. In addition, NASA had never scheduled a mission with such a high quantity of complex extravehicular activity. To meet the challenge of this mission, the STS-61 crew trained extensively in the Weightless Environment Test Facility at the Johnson Space Center and in the Neutral Buoyancy Simulator at the Marshall Space Flight Center. However, it was suspected that neutral buoyancy training might induce negative training by virtue of the viscous damping effect present in water. The mockups built for this training also did not have the mass properties of the actual orbital replacement units (ORUs). It was felt that the crew should be further trained on mockups with similar mass characteristics. A comprehensive study was designed to address these issues. The study was quantitative, and instrumentation was set up to measure and quantify the forces and moments experienced during ORU mass handling and remote manipulator system run conditions.
Loads produced by a suited subject performing tool tasks without the use of foot restraints
With an increase in the frequency of extravehicular activities (EVA's) aboard the Space Shuttle, NASA is interested in determining the capabilities of suited astronauts while performing manual tasks during an EVA, in particular the situations in which portable foot restraints are not used to stabilize the astronauts. Efforts were made to document the forces that are transmitted to spacecraft while pushing and pulling an object as well as while operating a standard wrench and an automatic power tool. The six subjects studied aboard the KC-135 reduced gravity aircraft were asked to exert a maximum torque and to maintain a constant level of torque with a wrench, to push and pull an EVA handrail, and to operate a Hubble Space Telescope (HST) power tool. The results give an estimate of the forces and moments that an operator will transmit to the handrail as well as to the supporting structure. In general, it was more effective to use the tool inwardly toward the body rather than away from the body. There were no differences in terms of strength capabilities between right and left hands. The power tool was difficult to use. It is suggested that ergonomic redesigning of the power tool may increase the efficiency of power tool use.
Anthropometric survey of the astronaut applicants and astronauts from 1985 to 1991
The Anthropometry and Biomechanics Laboratory at the Johnson Space Center has been collecting anthropometric data from astronaut applicants since 1977. These anthropometric measurements had been taken from 473 applicants. Based on the position they applied for, these applicants were classified as either mission specialists, payload specialists, pilots, or observers. The main objective was to document the variations among these applicants and tabulate the percentile data for each anthropometric dimension. The percentile and the descriptive statistics data were tabulated and graphed for the whole astronaut candidate population; for the male and female groups; for each subject classification such as pilot, mission specialist, and payload specialist; and finally, for those who were selected as astronauts.
Evaluation of hole sizes in structures requiring EVA services as a means to prevent gloved-hand finger entrapment
One of the concerns of Space Station designers was making sure that the suited crewmembers' gloved fingers are not trapped in the holes that may be present in the structures during EVA activities. A study was conducted on 11 subjects to determine the minimum and maximum possible hole sizes that would eliminate the possibility of finger entrapment. Subjects wore pressurized gloves and attempted to insert their fingers into holes of various sizes. Based on the experimental results, it is recommended that the smallest diameter should be less than 13.0 mm and the largest diameter should be greater than 35.0 mm in order to eliminate the possibility of finger entrapment while wearing gloves. It is also recommended that the current requirements specified by the MSIS-STD-3000 (Section 6.3.3.4) should be modified accordingly.
A comparison of hand grasp breakaway strengths and bare-handed grip strengths of the astronauts, SML 3 test subjects, and the subjects from the general population
Astronauts have the task of retrieving and deploying satellites and handling massive objects in a around the payload bay. Concerns were raised that manual handling of such massive objects might induce loads to the shuttle suits exceeding the design-certified loads. The Crew and Thermal Division of NASA JSC simulated the satellite handling tasks (Satellite Manload Tests 1 and 3) and determined the maximum possible load that a suited member could impart onto the suit. In addition, the tests revealed that the load to the suit by an astronaut could be calculated from the astronaut's maximum hand grasp breakaway strength. Thus, this study was conducted to document that hand grasp breakaway strengths of the astronauts who were scheduled to perform EVA during the upcoming missions. In addition, this study verified whether the SML 3 test results were sufficient for documenting the maximum possible load. An attempt was made to predict grasp strength from grip strength and hand anthropometry. Based on the results from this study, the SML 3 test results were deemed sufficient to document the maximum possible load on the suit. Finally, prediction of grasp strength from grip strength was not as accurate as expected. Hence, it was recommended that grasp strength be collected from the astronauts in order to obtain accurate load estimation.
A comparison of two Shuttle launch and entry suits - Reach envelope, isokinetic strength, and treadmill tests
A quantification has been conducted of any existing differences between the performance, in operational conditions, of the Space Shuttle crew Launch Entry Suit (LES) and the new Advanced Crew Escape Suit (ACES). While LES is a partial-pressure suit, the ACES system which is being considered as a replacement for LES is a full-pressure suit. Three tests have been conducted with six subjects to ascertain the suits' reach envelope, strength, and treadmill performance. No significant operational differences were found between the two suit designs.
A study to explore locomotion patterns in partial gravity environments
An effort is made to ascertain the factors affecting stability during locomotion in lunar and Martian gravity environments, as well as to establish criteria for the enhancement of stability and traction. The effects of changing both the speed and the pattern of locomotion under three different gravity conditions were investigated. As gravity level increased, vertical and horizontal forces significantly declined; similarities were noted across gravity levels, however, with respect to locomotion speed and pattern changes, where increasing speed enhanced both vertical and horizontal forces. With decreasing gravity, the ratio of horizontal to vertical forces increased significantly.