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Correlations for transition from laminar to turbulent flow on 45° and 60° swept cylinders based on data obtained in the NASA Langley Mach 3.5 Pilot Quiet Tunnel are presented. Variations of free-stream noise from high levels comparable to those in conventional wind tunnels to more than an order of magnitude lower had no effect on transition. However, when boundary-layer trips were attached to the leading edges, transition occurred at lower Reynolds numbers depending on both the trip height and the wind tunnel noise level. Compressible linear stability calculations have been performed for the boundary layer on an infinite swept cylinder. The boundary layer on the attachment line has a generalized inflection point similar to that present in a flat-plate boundary layer. The results show that Tollmien-Schlichting waves are amplified in the attachment line boundary layer and that oblique waves have the highest growth rates. Wall cooling tends to be stabilizing.

This report summarizes the experimental research conducted at the NASA Langley Research Center on general aviation seat and occupant crash response and discusses seat design considerations. Included are typical floor acceleration pulses from general aviation airplane crash tests, the performance of typical general aviation seats in a simulated crash environment, and the performance of prototype energy absorbing (EA) seat designs. Static and dynamic seat testing procedures and test facilities are discussed. Also presented are results from a series of dynamic tests of typical general aviation seats and prototype EA seats.

Ionizing radiation exposures and associated dosimetric quantities are evaluated for the 11-year solar cycle ending in 1986. Solar flare fluences for the 55 largest flares occurring during the cycle are superimposed on the galactic cosmic ray flux. Published summaries of flare data from the Interplanetary Monitoring Platform (IMP)-7 and IMP-8 satellites are used and include flares whose integrated fluences are greater than 107 protons/cm2 for energies in excess of 10 MeV. A standard cosmic ray environment model for ion flux values at solar minimum and maximum is invoked with an assumed sinusoidal variation between the lower and upper limits. The radiation shielding analysis is carried out for equivalent water-shield thicknesses between 2 and 15 g/cm2. Results are expressed in terms of cumulative incurred dose equivalents for deep-space missions lasting between 3 months and 3 years.

Wind-Tunnel-Wall Interference Assessment and Correction (MAC) concepts, applications, and typical results are discussed in terms of several nonlinear transonic codes and one panel method code developed for and being implemented at the NASA Langley Research Center. Contrasts between 2-D and 3-D transonic testing factors which affect WIAC procedures are illustrated using airfoil data from the NASA Langley 0.3-Meter Transonic Cryogenic Tunnel (TCT) and Pathfinder I data from the NASA Langley National Transonic Facility (NTF). In addition, very recently obtained 3-D transonic WIAC results for Mach number and angle-of-attack corrections to data from a relatively large 20° swept semispan wing in the solid-wall NASA Ames High-Reynolds Number (HRN) Channel I (1.92% solid blockage) are independently verified by 3-D thin-layer Navier-Stokes free-air solutions. Initial results from the 3-D WIAC codes are encouraging; research on and implementation of WIAC concepts will continue.

The ability of modern airplane surfaces to achieve laminar flow has been well-accepted in recent years. Obtaining the maximum benefit of laminar flow for aircraft drag reduction requires maintaining minimum leading-edge contamination. Previously proposed insect contamination prevention methods have proved impractical due to cost, weight, or inconvenience. Past work has shown that insects will not adhere to water-wetted surfaces, but large volumes of water required for protection rendered such a system impractical. This paper presents results of a flight experiment conducted by NASA to evaluate the performance of a porous leading-edge fluid discharge ice protection system operated as an insect contamination protection system. In addition, these flights explored the environmental and atmospheric conditions most suitable for insect accumulation.

Barriers to the more extensive use of advanced composites in heavily loaded structure on commercial transports are discussed from a materials viewpoint. NASA-Langley matrix development activities designed to overcome these barriers are presented. These include the synthesis of processable, tough, durable matrices, the development of resin property/composite property relationships which help guide the synthesis program, and the exploitation of new processing technology to effectively combine reinforcement filament with polymer matrices. Examples of five classes of polymers being investigated as matrix resins at NASA-Langley will be presented, including amorphous and semi-crystalline thermoplastics, lightly crosslinked thermoplastics, semi-interpenetrating networks and toughened thermosets. Relationships between neat resin modulus, resin fracture energy, interlaminar fracture energy, composite compression strength, and post-impact compression strength will be shown.

High-angle-of-attack flight dynamics of the X-29 configuration were studied using dynamic model test techniques. These tests identified phenomena including wing rock, spins, and tumbling which dominate the high-α behavior of the configuration and define its usable flight envelope. Results of these tests have been used to design flight control concepts to minimize adverse behavior. Planned high-angle-of-attack flight tests of the X-29 airplane will provide an opportunity to validate the model predictions.

An impulse-momentum analysis was conducted of crash deceleration pulse data from the National Aeronautics and Space Administration (NASA) crash dynamics program on general aviation airplanes and transport crash data available in the literature. The purpose of the analysis was to correlate crash data with flight parameters at impact. In the analysis, assumptions made to simplify the complex crash scenario led to uncoupled equations for the normal and longitudinal floor impulses (product of deceleration and time) in the cabin area of the airplane. Analytical expressions for structural crushing during impact and for the airplane horizontal slide-out were also determined. Good agreement was found between the experimental and analytical data for the general aviation and transport airplanes over a relatively wide range of impact parameters.

Landings of the Space Shuttle Orbiter at 200 knot speeds on the rough, grooved Kennedy Space Center runway have encountered greater than anticipated tire wear, which resulted in limiting landings on that runway to crosswinds of 10 knots or less. The excessive wear stems from wear caused during the initial tire touchdown spin-up. Tire spin-up wear tests have been conducted on a simulated KSC runway surface modified by several different techniques in an effort to reduce spin-up wear while retaining adequate wet cornering coefficients for directional control. The runway surface produced by a concrete smoothing machine using cutters spaced 1 3/4 blades per centimeter was found to give adequate wet cornering while limiting spin-up wear to that experienced in spinups on smooth concrete.

A brief history of stall/spin technology for light general aviation airplanes and proposed criteria to describe desirable characteristics of a spin-resistant airplane are presented. Flight tests of a representative light airplane to evaluate compliance with and usefulness of the criteria are presented. The baseline airplane configuration would not meet the spin resistance criteria. Tests of the airplane with a wing leading edge modification to enhance its spin resistance showed compliance with the proposed criteria.

Measurements obtained for ground tests on a Twin Otter aircraft show that structureborne noise is a major contributor to the interior noise level. The structureborne source was the propeller blade wake and tip vortex interaction with the wing and contributes at the blade passage frequency and its harmonics.

A supercritical water oxidation (SCWO) concept was evaluated to determine its potential to reduce the number of processes required to provide an Environmental Control and Life Support System in an Evolutionary Space Station, to reduce the Station resupply requirements, and to enhance the integration of separate ECLSS functions into a single Supercritical Water Oxidation process. Three conceptual design cases were evaluated. The results indicated that the SCWO technology was not a viable substitute for the IOC Space Station ECLSS, because the technology was not sufficiently mature to meet the 1987 Space Station design commitment date. For an Evolutionary Space Station, the SCWO process could enhance the integration of eight ECLSS functions into a single function, thereby reducing programmatic costs. The SCWO technology combined with current onboard food production technology was not a viable option to replace stored food, because food production technology was inefficient.