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Special exposure limit recommendations have been designated by the National Council on Radiation Protection (NCRP) for U. S. astronauts in low earth orbit (LEO) operations. These have been established from consideration of a 3% lifetime excess risk of cancer mortality for a 10-yr. active career. The most recent recommendations of the National Council on Radiation Protection and Measurements (NCRP) have incorporated modified procedures for evaluating exposures with accompanying adjustments in career limits. Of special importance are the limit specifications for female exposures, which are approximately 40% less than those for males. Furthermore, radiosensitive organs unique to females require additional attention.

A detailed spacesuit computational model is being developed at the Langley Research Center for exposure evaluation studies. The details of the construction of the spacesuit are critical to an estimate of exposures and for assessing the health risk to the astronaut during extra-vehicular activity (EVA). Fine detail of the basic fabric structure, helmet, and backpack is required to assure a valid evaluation. The exposure fields within the Computerized Anatomical Male (CAM) and Female (CAF) are evaluated at 148 and 156 points, respectively, to determine the dose fluctuations within critical organs. Exposure evaluations for ambient environments will be given and potential implications for geomagnetic storm conditions discussed.

An experimental investigation was conducted to study the effectiveness of Synthetic Vision Systems (SVS) flight displays as a means of eliminating Low Visibility Loss of Control (LVLOC) and Controlled Flight Into Terrain (CFIT) accidents by low time general aviation (GA) pilots. A series of basic maneuvers were performed by 18 subject pilots during transition from Visual Meteorological Conditions (VMC) to Instrument Meteorological Conditions (IMC), with continued flight into IMC, employing a fixed-based flight simulator. A total of three display concepts were employed for this evaluation. One display concept, referred to as the Attitude Indicator (AI) replicated instrumentation common in today's General Aviation (GA) aircraft. The second display concept, referred to as the Electronic Attitude Indicator (EAI), featured an enlarged attitude indicator that was more representative of a “glass display” that also included advanced flight symbology, such as a velocity vector.

The General Aviation Element of the Aviation Safety Program's Synthetic Vision Systems (SVS) Project is developing technology to eliminate low visibility induced General Aviation (GA) accidents. SVS displays present computer generated 3-dimensional imagery of the surrounding terrain on the Primary Flight Display (PFD) to greatly enhance pilot's situation awareness (SA), reducing or eliminating Controlled Flight into Terrain, as well as Low-Visibility Loss of Control accidents. SVS-conducted research is facilitating development of display concepts that provide the pilot with an unobstructed view of the outside terrain, regardless of weather conditions and time of day. A critical component of SVS displays is the appropriate presentation of terrain to the pilot. An experimental study is being conducted at NASA Langley Research Center (LaRC) to explore and quantify the relationship between the realism of the terrain presentation and resulting enhancements of pilot SA and performance.

Meeting radiation protection requirements during EVA is predominantly an operational issue with some potential considerations for temporary shelter. The issue of spacesuit shielding is mainly guided by the potential of accidental exposure when operational and temporary shelter considerations fail to maintain exposures within operational limits. In this case, very high exposure levels are possible which could result in observable health effects and even be life threatening. Under these assumptions, potential spacesuit radiation exposures have been studied using known historical solar particle events to gain insight on the usefulness of modification of spacesuit design in which the control of skin exposure is a critical design issue and reduction of blood forming organ exposure is desirable.

A new Green’s function code (GRNTRN) capable of simulating HZE ions with either laboratory or space boundary conditions is currently under development. The computational model consists of combinations of physical perturbation expansions based on the scales of atomic interaction, multiple scattering, and nuclear reactive processes with use of the Neumann-asymptotic expansions with non-perturbative corrections. The code contains energy loss due to straggling, nuclear attenuation, nuclear fragmentation with energy dispersion and downshifts. Recent publications have focused on code validation in the laboratory environment and have shown that the code predicts energy loss spectra accurately as measured by solid-state detectors in ion beam experiments. In this paper emphasis is placed on code validation with space boundary conditions.

Recently, a new Green’s function code (GRNTRN) for simulation of HZE ion beams in the laboratory setting has been developed. Once fully developed and experimentally verified, GRNTRN will be a great asset in assessing radiation exposures in both the laboratory and space settings. The computational model consists of combinations of physical perturbation expansions based on the scales of atomic interaction, multiple elastic scattering, and nuclear reactive processes with use of Neumann-series expansions with non-perturbative corrections. The code contains energy loss with straggling, nuclear attenuation, nuclear fragmentation with energy dispersion and down shifts. Previous reports show that the new code accurately models the transport of ion beams through a single slab of material. Current research efforts are focused on enabling the code to handle multiple layers of material and the present paper reports on progress made towards that end.

Human factors egress testing of the HL-20 Personnel Launch System, a reusable flight vehicle for Space Station crew rotation, was conducted in both the vertical (launch) and horizontal (landing) positions using a full-scale model. Ingress and egress of 10-person crews were investigated with volunteers representing a range of heights. For both the vertical and horizontal positions, interior structural keels had little impact on egress times which were generally less than 30 seconds. Wearing Shuttle partial pressure suits required somewhat more egress time than when ordinary flight suits were worn due to the larger helmet of the Shuttle suit.

An advanced analytical methodology has been developed for predicting the residual strength of stiffened thin-sheet riveted shell structures such as those used for the fuselage of a commercial transport aircraft. The crack-tip opening angle elastic-plastic fracture criterion has been coupled to a geometric and material nonlinear finite element shell code for analyzing complex structural behavior. An automated adaptive mesh refinement capability together with global-local analysis methods have been developed to predict the behavior of fuselage structure with long cracks. This methodology is currently being experimentally verified. Advanced nondestructive inspection technology has been developed that will provide airline operators with the capability to conduct reliable and economical broad-area inspections of aircraft structures.

Alternate Environmental Control and Life Support System (ECLSS) technologies were evaluated to reduce Space Station resources and dependence on expendables resupplied from Earth to sustain a multiperson crew in low-Earth orbit. Options were evaluated to close the oxygen (O2) loop by removing carbon dioxide (CO2) from the cabin air, reducing the CO2 to water, and electrolyzing the water to provide metabolic O2 for crew consumption. Options were also evaluated to close the urine/flush, condensate, and hygiene water loops to provide potable water for crew use. Specific evaluation parameters were derived which included weight, power, volume, maintenance, resupply consumables, and technology readiness.

As part of NASA's composite structures crash dynamics research, a general aviation aircraft with composite wing, fuselage and empennage (but with metal subfloor structure) was crash tested at the NASA Langley Research Center Impact Dynamics Research Facility. The test was conducted to determine composite aircraft structural behavior for crash loading conditions and to provide a baseline for a similar aircraft test with a modified subfloor. Structural integrity and cabin volume were maintained. Lumbar loads for dummy occupants in energy absorbing seats were substantially lower than those in standard aircraft seats; however, loads in the standard seats were much higher than those recorded under similar conditions for an all-metallic aircraft.

The highly inclined orbit of the International Space Station Alpha exhibits significant radiation exposure contributions from the galactic cosmic rays penetrating the earth's magnetic field. In the absence of an accepted method for estimating the corresponding astronaut risk, we examined the attenuation characteristics using conventional LET dependent quality factors (as one means of representing RBE) and a track-structure repair model fit to cell transformation (and inactivation) data in the C3H10T1/2 mouse cell system obtained by T. C. Yang and coworkers for various ion beams. Although the usual aluminum spacecraft shield is effective in reducing dose equivalent with increasing shield thickness, cell transformation rates are increased for thin aluminum shields providing increased risk rather than protection to large shield thickness.

The effects of both the cosmic ray heavy ion exposures and the intense trapped electron exposures are examined with respect to impact on cellular system survival on exterior spacecraft surfaces as well as at interior (shielded) locations for a sample mission to Jupiter’s moons. Radiation transport through shield materials and subsequent exposures are calculated with the established Langley heavy ion and electron deterministic codes. In addition to assessing fractional DNA single and double strand breaks, a variety of cell types are examined that have greatly differing radio-sensitivities. Finally, implications as to shield requirements for controlled biological experiments are discussed.

As part of NASA’s Aviation Safety and Security Program, a simulation study of a twin-jet transport aircraft crew training simulation was conducted to address fidelity for upset or loss-of-control flight conditions. Piloted simulation studies were conducted to compare the baseline crew training simulation model with an enhanced aerodynamic model that was developed for high-angle-of-attack conditions. These studies were conducted in a flaps-up configuration and covered the approach-to-stall, stall and post-stall flight regimes. Qualitative pilot comments and preliminary comparison with flight test data indicate that the enhanced model is a significant improvement over the baseline. Some of the significant unrepresentative characteristics that are predicted by the baseline crew training simulation for flight in the post-stall regime have been identified.

The Federal Aviation Administration (FAA) and the National Aeronautics and Space Administration (NASA) have joined forces in a General Aviation Crashworthiness Program. This paper describes the research and development tasks of the program which are the responsibility of NASA. NASA is embarked upon research and development tasks aimed at providing the general aviation industry with a reliable crashworthy airframe design technology. The goals of the NASA program are: reliable analytical techniques for predicting the nonlinear behavior of structures; significant design improvements of airframes; and simulated full-scale crash test data. The analytical tools will include both simplified procedures for estimating energy absorption characteristics and more complex computer programs for analysis of general airframe structures under crash loading conditions.

NASA antiskid braking system research programs are reviewed. These programs include experimental studies of four antiskid systems on the Langley Landing Loads Track, flight tests with a DC-9 airplane, and computer simulation studies. Results from these research efforts include identification of factors contributing to degraded antiskid performance under adverse weather conditions, tire tread temperature measurements during antiskid braking on dry runway surfaces, and an assessment of the accuracy of various brake pressure-torque computer models. This information should lead to the development of better antiskid systems in the future.

This paper describes the NASA portion of a joint FAA-NASA General Aviation Crashworthiness Program leading to the development of improved crashworthiness design technology. The objectives of the program are to develop analytical technology for predicting crashworthiness of structures, provide design improvements, and perform full-scale crash tests. The analytical techniques which are being developed both in-house and under contract are described and typical results from these analytical programs are shown. In addition, the full-scale testing facility and test program are discussed.

This paper discusses a project for adapting advanced technology, much of it borrowed from the jet transport, to general aviation design practice. The NASA funded portion of the work began in 1969 at the University of Kansas and resulted in a smaller, experimental wing with spoilers and powerful flap systems for a Cessna Cardinal airplane. The objective was to obtain increased cruise performance and improved ride quality while maintaining the take-off and landing speeds of the unmodified airplane. Some flight data and research pilot comments are presented. The project was expanded in 1972 to include a light twin-engine airplane. For the twin there was the added incentive of a potential increase in single-engine climb performance. The expanded project is a joint effort involving the University of Kansas, Piper Aircraft Company, Robertson Aircraft Company, and Wichita State University. The use of a new high-lift Whitcomb airfoil is planned for both the wing and the propellers.

A discussion is given of the ongoing research related to laminar flow airfoils, nacelles, and wings where the laminar flow is maintained by a favorable pressure gradient, surface suction or a combination of the two. Design methologies for natural laminar flow airfoil sections and wings for both low and high speed applications are outlined. Tests of a 7-foot chord, 23° sweep laminar-flow-control-airfoil at high subsonic Mach numbers are described along with the associated stability theory used to design the suction system. The state-of-the-art of stability theory is simply stated and a typical calculation illustrated. In addition recent computer simulations of transition using the time dependent Navier-Stokes (N-S) equations are briefly described. Advances in wind tunnel capabilities and instrumentation will be reviewed followed by the presentation of a few results from both wind tunnels and flight. Finally, some suggestions for future work will complete the paper.

An automatic trim system for reducing the control forces after an engine failure on a light twin has been investigated on the Langley General Aviation Simulator. The system schedules open-loop trim tab deflections as a function of differential propeller slipstream dynamic pressure and freestream dynamic pressure. The system is described and the airplane-system static and dynamic characteristics are documented. Three NASA research pilots evaluated the effectiveness of the system for takeoff and landing maneuvers. A variety of off-nominal system characteristics were studied. The system was judged to be generally beneficial, providing a 2 to 3 point improvement in pilot rating for the tasks used in the evaluations.