SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS

A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 43, ISSUE 19 - SEPTEMBER 23, 2005

01 AERONAUTICS (GENERAL)
Includes general research topics related to manned and unmanned aircraft and the problems of flight within the Earth’s atmosphere.

Also includes manufacturing, maintenance, and repair of aircraft.

For specific topics in aeronautics, see categories 02 through 09. For information related to space vehicles see 12 Astronautics.

20050210162 General Accounting Office, Washington, DC, USA

Air Traffic Control: Characteristics and Performance of Selected International Air Navigation Service Providers and Lessons Learned from Their Commercialization

Jul. 2005; 44 pp.; In English Report No.(s): PB2005-109418; GAO-05-769; No Copyright; Avail: CASI; A03, Hardcopy

In the past, governments worldwide owned, operated, and regulated air navigation services, viewing air traffic control as a governmental function. But as nations faced increasing financial strains, many governments decided to shift the responsibility to an independent air navigation service provider (ANSP) that operates as a business. As of March 2005, 38 nations worldwide had commercialized their air navigation services, fundamentally shifting the operational and financial responsibility for providing these services from the national government to an independent commercial authority. GAO selected five ANSPs--in Australia, Canada, Germany, New Zealand, and the UK--to develop, as requested, a descriptive analysis of commercialized ANSPs that illustrated similarities and differences in ownership, length of experience with commercialization, and size and scope of operations. This report addresses the following questions: (1) What are common characteristics of commercialized ANSPs in selected foreign countries; (2) What do available data show about how the safety, cost, and efficiency of air navigation services have changed since commercialization; and (3) What are some key lessons learned about the commercialization of air navigation services. NTIS

Air Navigation; Air Traffýc; Air Traffýc Control; Air Transportation; Commercialization; Navigation

20050210231 NASA Goddard Space Flight Center, Greenbelt, MD, USA

Hubble Space Telescope Angular Velocity Estimation During the Robotic Servicing Mission

Thienel, Julie K.; Queen, Steven Z.; VanEepoel, John M.; Sanner, Robert M.; [2005]; 14 pp.; In English; AIAA Guidance, Navigation and Control Conference and Exhibit, 15-18 Aug. 2005, San Francisco, CA, USA; Copyright; Avail: CASI; A03, Hardcopy

In 2004 NASA began investigation of a robotic servicing mission for the Hubble Space Telescope (HST).

Such a mission would require estimates of the HST attitude and rates in order to achieve a capture by the proposed Hubble robotic vehicle (HRV). HRV was to be equipped with vision-based sensors, capable of estimating the relative attitude between HST and HRV. The inertial HST attitude is derived from the measured relative attitude and the HRV computed inertial attitude. However, the relative rate between HST and HRV cannot be measured directly. Therefore, the HST rate with respect to inertial space is not known.

Two approaches are developed to estimate the HST rates. Both methods utilize the measured relative attitude and the HRV inertial attitude and rates. First, a non-linear estimator is developed. The nonlinear approach estimates the HST rate through an estimation of the inertial angular momentum. Second, a linearized approach is developed. The linearized approach is a pseudo-linear Kalman filter. Simulation test results for both methods are given.

Even though the development began as an application for the HST robotic servicing mission, the methods presented are applicable to any rendezvous/capture mission involving a non-cooperative target spacecraft. Author

Robotics; Angular Velocity; Estimating; Hubble Space Telescope; Attitude (Inclination)

20050212115 NASA Langley Research Center, Hampton, VA, USA

Performance of a Checkerboard Liner With Uncertain Impedances

Robinson, J. H.; Watson, W. R.; [2005]; 13 pp.; In English; 11th AIAA/CEAS Aeroacoustics Conference, 23-25 May 2005, Monterey, CA, USA Contract(s)/Grant(s): 23-781-10-12; No Copyright; Avail: CASI; A03, Hardcopy

The current fleet of large commercial aircraft has successfully achieved FAA noise certifications because of, in part, the successful application of uniform passive duct liner treatments to control engine system noise. One goal of NASA’s engine system noise reduction program is to develop technologies to improve the sound absorbing properties of duct liner treatments so that they remain effective in modern turbo fan engines.

One such technology being studied is checkerboard or periodic axially and circumferentially segmented liners. A preliminary assessment of the potential of this technology was conducted by applying uncertainties associated with manufacturing, installation, source structure, and tonal frequency to a liner developed using deterministic design methods and generating a measure of improvement with respect to a uniform liner subjected to the same uncertainties. Deterministic design and analysis of the candidate checkerboard liner showed that it obtains a 1.5 dB per duct aspect ratio improvement in liner attenuation over a similarly designed uniform liner. When uncertainties in liner impedances, source structure, and frequency are considered, the performance of the checkerboard liner drops off dramatically.

The final results of this paper show that the candidate checkerboard liner has a less than 25 percent chance of outperforming the uniform liner when moderate levels of uncertainty are considered. It is important to note that this study did not include the effects of mean flow on liner performance and, more important to note, that as a gradient based optimization process was used to design the checkerboard liner, it is almost certain that a global optimal design was not found for the candidate checkerboard liner. Had it been possible to find a better deterministically performing checkerboard liner, the probability that this candidate liner would outperform the uniform liner would certainly have been higher. Author

Linings; Ducts; Engine Noise; Noise Reduction; Absorbers (Materials); Commercial Aircraft; Design Analysis

20050214038 Boeing Co., USA

Emissions Inventory

Baughcum, Steven L.; Sutkus, Donald J.; NASA Glenn Research Center UEET (Ultra-Efficient Engine Technology) Program: Agenda and Abstracts; [2001], pp. 49; In English; See also 20050214031; No Copyright; Abstract Only;Available from CASI only as part of the entire parent document

We report on our recently completed three-dimensional (1deg latitude by 1deg longitude by 1 km altitude) inventory of global aircraft emissions (fuel burned, NO(x), CO, and total hydrocarbons) from scheduled air traffic for the year 1999. The methodology used to create this inventory is described and inventory results are presented. These results are compared with our previously published inventory of emissions for the year 1992, and the trends are discussed. Author

Hydrocarbons; Inventories; Air Traffýc; Trends

20050214639 Lawrence Livermore National Lab., Livermore, CA USA

Experimental Study of Drag Reduction Devices for a Trailer Underbody and Base

Ortega, J. M.; Salari, K.; Jun. 04, 2004; 22 pp.; In English Report No.(s): DE2005-15014223; UCRL-CONF-204489; No Copyright; Avail: Department of Energy Information Bridge

Low speed wind tunnel measurements are made on a 1/16th scale generic tractor-trailer model at a width-based Reynolds number of 325,000. The model is fixed to a turntable, allowing the yaw angle to be varied between plus or minus 14 degrees in 2 degree increments. Various add-on drag reduction devices are mounted to the model underbody and base. The wind-averaged drag coefficient at 65 mph is computed for each configuration, allowing the effectiveness of the add-on devices to be assessed. NTIS

Drag Reduction; Tractors; Trailers

Source: NASA.