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This paper presents a simplified orbit analysis program developed to calculate orbital parameters for the thermal analysis of spacecraft and space-flight instruments. The program calculates orbit data for inclined and sunsynchronous earth orbits. Traditional orbit analyses require extensive knowledge of orbital mechanics to produce a simplified set of data for thermal engineers. This program was created to perform orbital analyses with minimal input and provides the necessary output for thermal analysis codes. Engineers will find the program to be a valuable analysis tool for fast and simple orbit calculations. A description of the program inputs and outputs is included. An overview of orbital mechanics for inclined and Sun-synchronous orbits is also presented. Finally, several sample cases are presented to illustrate the thermal analysis applications of the program.

Noise is a barrier issue for penetration of civil markets by future tiltrotor aircraft. To address this issue, elements of the NASA Short Haul (Civil Tiltrotor) [SH(CT)] program are working in three different areas: noise abatement, noise reduction, and noise prediction. Noise abatement refers to modification of flight procedures to achieve quieter approaches. Noise reduction refers to innovative new rotor designs that would reduce the noise produced by a tiltrotor. Noise prediction activities are developing the tools to guide the design of future quiet tiltrotors. This paper presents an overview of SH(CT) activities in all three areas, including sample results.

The need for highly accurate measurements of velocity, temperature, pressure and density has required the development of new experimental techniques. While the majority of these development efforts at NASA Langley are focused toward applications for aeronautical programs such as the High-Speed Civil Transport, Advanced Subsonic Transport, and the National Aero-Space Plane, a number are applicable to other fields. The intent of this paper is to review recent instrumentation developments and applications at NASA Langley Research Center that may have applications in automotive testing. Five experimental techniques are described along with recent results obtained in NASA facilities.

This paper describes recent research in integrated aerodynamic-performance design optimization applied to a supersonic transport wing. The subsonic and supersonic aerodynamics are modeled with linear theory and the aircraft performance is evaluated by using a complete mission analysis. The goal of the optimization problem is to either maximize the aircraft range or minimize the take-off gross weight while constraining the total fuel load and approach speed. A major difficulty encountered during this study was the inability to obtain accurate derivatives of the aerodynamic models with respect to the planform shape. This work addresses this problem and provides one solution for the derivative difficulties. Additional optimization studies reveal the impact of camber design on the global optimization problem. In these studies, the plan-form optimization is first conducted on a flat plate wing and camber optimization is performed on the resulting planform.

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.

Aerodynamic effects induced from vectoring an exhaust jet are investigated using a well established thin-layer Reynolds averaged Navier-Stokes code. This multiple block code has been modified to allow for the specification of jet properties at a block face. The applicability of the resulting code for thrust vectoring applications is verified by comparing numerically and experimentally determined pressure coefficient distributions for a jet-wing afterbody configuration with a thrust-vectoring 2-D nozzle. Induced effects on the body and nearby wing from thrust vectoring are graphically illustrated.

An investigation was conducted at the NASA Langley Research Center's Aircraft Landing Dynamics Facility (ALDF) to define the post-tire failure drag characteristics of the Space Shuttle Orbiter main tire and wheel assembly. Skid tests on various materials were also conducted to define their friction and wear rate characteristics under higher speed and bearing pressures than any previous tests. The skid tests were conducted to support a feasibility study of adding a skid to the orbiter strut between the main tires to protect an intact tire from failure due to overload should one of the tires fail. Roll-on-rim tests were conducted to define the ability of a standard and a modified orbiter main wheel to roll without a tire. Results of the investigation are combined into a generic model of strut drag versus time under failure conditions for inclusion into rollout simulators used to train the shuttle astronauts.

Laminar flow flight experiments conducted over the past fifty years will be reviewed. The emphasis will be on flight testing conducted under the NASA Laminar Flow Control Program which has been directed towards the most challenging technology application- the high subsonic speed transport. The F111/TACT NLF Glove Flight Test, the F-14 Variable Sweep Transition Flight Experiment, the 757 Wing Noise Survey and NLF Glove Flight Test, the NASA Jetstar Leading Edge Flight Test Program, and the recently initiated Hybrid Laminar Flow Control Flight Experiment will be discussed. To place these recent experiences in perspective, earlier important flight tests will first be reviewed to recall the lessons learned at that time.

Over the past three decades, the application of simulation facilities to manned space flight projects has increased chances of successful mission completion by revealing the capabilities and limitations of both man and machine. The Space Station era, which implies on-orbit assembly, heightened system complexity, and great diversity of operations and equipment, will require increased dependence on simulation studies to validate the tools and techniques being proposed. For this reason the Society of Automotive Engineers (SAE) undertook a survey of both the facilities available for and the research requiring such simulations. This paper was written to provide LaRC input to the SAE survey of simulation needs and resources. The paper provides a brief historial sketch of early Langley Research Center simulators, and the circumstances are described which resulted in a de-emphasis of manned simulation in 1971.

Current viscous drag reduction research explores the limits of practical applications of natural laminar flow (NLF) for airplane drag reduction. To better understand these limits, advanced measurement techniques are required to study the characteristics of laminar to turbulent boundary-layer transition. Recent NASA research indicates that the transition mode which involves laminar separation can be detected using arrayed hot-film laminar separation sensor concepts. These surface-mounted sensors can provide information on the location of the laminar separation bubble as well as bubble length. This paper presents two different laminar separation sensor configurations developed in the NASA program and presents results of wind-tunnel and flight evaluations of the sensors as tools to detect boundary-layer transition.

The condition of aircraft tires and runway surfaces can be crucial in meeting the stringent demands of aircraft ground operations, particularly under adverse weather conditions. Gaining a better understanding of the factors influencing the tire/pavement interface is the aim of several ongoing NASA Langley research programs which are described in this paper. Results from several studies conducted at the Langley Aircraft Landing Dynamics Facility, tests with instrumented ground vehicles and aircraft, and some recent aircraft accident investigations are summarized to indicate effects of different tire and runway properties. The Joint FAA/NASA Runway Friction Program is described together with some preliminary test findings. The scope of future NASA Langley research directed towards solving aircraft ground operational problems related to the tire/pavement interface is given.

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.

This paper will examine modern avionics and related developments coming from the electronics revolution and show how they can be applied to in-service aircraft to produce significant performance improvements. While it is recognized the discussion could be very wide ranging, this paper will focus primarily on some of the developments in which NASA-Langley Research Center has been involved, including advanced flight management concepts, flat panel displays, and innovative fuel gauge designs. This paper will also look at emerging airspace system concepts, such as navigation using satellites and communications via data links, and provide a preliminary assessment of the impact of these concepts on in-service aircraft from the perspective of retrofitting avionics.

The Aircraft Landing Dynamics Facility (ALDF), formerly called the Landing Loads Track, is described. The paper gives a historical overview of the original NASA Langley Research Center Landing Loads Track and discusses the unique features of this national test facility. Comparisions are made between the original track characteristics and the new capabilities of the Aircraft Landing Dynamics Facility following the recently completed facility update. Details of the new propulsion and arresting gear systems are presented along with the novel features of the new high-speed carriage. The data acquisition system is described and the paper concludes with a review of future test programs.

This paper reports the status of the NASA Langley Research Center program aimed at the development of the technology required for large-scale Magnetic Suspension and Balance Systems. The use of magnetic suspension of the model in a wind tunnel is seen to be the only viable method to eliminate aerodynamic interference problems arising with mechanical model-supports. The two small-scale magnetic suspension systems in operation at Langley are the only ones now active in the U.S. The general features and capabilities of these two systems and all of the ongoing research in the use of magnetic suspension are described.

A research program is in progress to study the effects of the propeller slipstream on natural laminar flow. Flight and wind tunnel measurements of the wing boundary layer have been made using hot-film velocity sensor probes. The results show the boundary layer, at any given point, to alternate between laminar and turbulent states. This cyclic behavior is due to periodic external flow turbulence originating from the viscous wake of the propeller blades. Analytic studies show the cyclic laminar/turbulent boundary layer layer to result in a significantly lower wing section drag than a fully turbulent boundary layer. The application of natural laminar flow design philosophy yields drag reduction benefits in the slipstream affected regions of the airframe, as well as the unaffected regions.

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.

Two major concerns have inhibited the use of natural laminar flow (NLF) for viscous drag reduction on production aircraft. These are the concerns of achieveability of NLF on practical airframe surfaces, and maintainability in operating environments. Previous research in this area left a mixture of positive and negative conclusions regarding these concerns. While early (pre-1950) airframe construction methods could not achieve NLF criteria for waviness, several modern construction methods (composites for example) can achieve the required smoothness. This paper presents flight experiment data on the achieveability and maintainability of NLF on a high-performance, single-propeller, composite airplane, the Bellanca Skyrocket II. The significant contribution of laminar flow to the performance of this airplane was measured. Observations of laminar flow in the propeller slipstream are discussed, as are the effects of insect contamination on the wing.

A brief definition of an “All Electric Airplane” will be presented. Several NASA and DOD studies have examined the application of advanced electric/electronic technologies. The benefits identified in these studies will be summarized. The state-of-the-art in all electric airplane technology will be described. A NASA program has been proposed to develop the necessary technology base for industry application. The elements of this proposed program will be discussed.

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.