High-speed Research Research Articles

Is ozone doomed by supersonic plume?

The simple desire to save time is reviving interest in supersonic flight. Travelers' demands for faster travel have compelled Congress to fund NASA's High Speed Research Program, which aims to overcome the obstacles that sent full development of the supersonic passenger plane to its demise over 25 years ago.Removing those obstacles presents substantial challenges. The current $6,000 to $9,000 fare for a supersonic trans‐Atlantic trip on the Concorde lends credence to the view of supersonic aircraft as “chariots of the rich.”

Aerodynamic Performance and Instability Initiation of a High Speed Research Centrifugal Compressor

Aerodynamic Performance and Instability Initiation of a High Speed Research Centrifugal Compressor

Sensitivity of two‐dimensional model predictions of ozone response to stratospheric aircraft: An update

The Goddard Space Flight Center two‐dimensional model of stratospheric photochemistry and dynamics has been used to calculate the O3 response to stratospheric aircraft (high‐speed civil transport (HSCT)) emissions. The sensitivity of the model O3 response was examined for systematic variations of five parameters and two reaction rates over a wide range, expanding on calculations by various modeling groups for the NASA High Speed Research Program and the World Meteorological Organization. In all, 448 model runs were required to test the effects of variations in the latitude, altitude, and magnitude of the aircraft emissions perturbation, the background chlorine levels, the background sulfate aerosol surface area densities, and the rates of two key reactions. No deviation from previous conclusions concerning the response of O3 to HSCTs was found in this more exhaustive exploration of parameter space. Maximum O3 depletions occur for high‐altitude, low‐latitude HSCT perturbations. Small increases in global total O3 can occur for low‐altitude, high‐latitude injections. Decreasing aerosol surface area densities and background chlorine levels increases the sensitivity of model O3 to the HSCT perturbations. The location of the aircraft emissions is the most important determinant of the model response. Response to the location of the HSCT emissions is not changed qualitatively by changes in background chlorine and aerosol loading. The response is also not very sensitive to changes in the rates of the reactions NO + HO2 → NO2 + OH and HO2 + O3 → OH + 2O2 over the limits of their respective uncertainties. Finally, levels of lower stratospheric HOχ generally decrease when the HSCT perturbation is included, even though there are large increases in H2O due to the perturbation.

Significance of shock structure on supersonic jet mixing noise of axisymmetric nozzles

One of the key technical elements in NASA's high speed research program is reducing the noise level to meet the federal noise regulation. The dominant noise source is associated with the supersonic jet discharged from the engine exhaust system. Whereas the turbulence mixing is largely responsible for the generation of the jet noise, a broadband shock-associated noise is also generated when the nozzle operates at conditions other than its design. For both mixing and shock noise components, because the source of the noise is embedded in the jet plume, one can expect that jet noise can be predicted from the jet flowfield computation. Mani et al. developed a unified aerodynamic/acoustic prediction scheme by applying an extension of Reichardt's aerodynamic model to compute turbulent shear stresses which are utilized in estimating the strength of the noise source. Although this method produces a fast and practical estimate of the jet noise, a modification by Khavaran et al. has led to an improvement in aerodynamic solution. The most notable feature in this work is that Reichardt's model is replaced with the computational fluid dynamics (CFD) solution of Reynolds-averaged Navier-Stokes equations. The major advantage of this work is that the essential, noise-related flow quantities such as turbulence intensity and shock strength can be better predicted. The predictions were limited to a shock-free design condition and the effect of shock structure on the jet mixing noise was not addressed. The present work is aimed at investigating this issue. Under imperfectly expanded conditions the existence of the shock cell structure and its interaction with the convecting turbulence structure may not only generate a broadband shock-associated noise but also change the turbulence structure, and thus the strength of the mixing noise source. Failure in capturing shock structures properly could lead to incorrect aeroacoustic predictions.

Sonic boom predictions using a solution-adaptive full-potential code

The TranAir full-potential code, which utilizes a solution-adaptive, unstructured Cartesian grid, was used to compute near-field pressure signatures of three generic geometries: (1) a cone-cylinder; (2) a low aspect ratio rectangular wing; and (3) a delta-wing/body. Pressure signatures computed by TranAir are extrapolated to near- and midfield distances using a quasilinear extrapolation technique. Results are compared with wind-tunnel data and, where possible, with extrapolated wind-tunnel data and Whitham-method results. In general, extrapolated TranAir data is in good agreement with experimental and Whitham-method pressure signatures, but peak pressures are slightly underpredicted. It is felt that data computed too close to the model caused some of the discrepancies. The flowfield grid structure was also found to be an important issue in obtaining accurate off-body data. Results were encouraging enough to proceed with the application of TranAir to conceptual configurations in support of the NASA high speed research program (HSRP).

Sonic boom wave propagation from air into water: Implications for marine mammals

At the 1993 NASA High Speed Research Program Sonic Boom Workshop, hosted by NASA Ames Research Center, it ws noted that the development of a high speed civil transport in the next several years will focus only on overwater travel. At that meeting it was also made clear that some have raised concerns about the effects of sonic booms on the activities of marine mammals. Once a fleet of supersonic passenger aircraft are in service, there could be hundreds of flights per day, and, therefore, the effects of sonic booms on marine mammals should be well understood. The purpose of the present paper is to briefly describe the acoustic pressure and intensity variations that one can predict underwater due to a sonic boom impinging on an air–water interface. Arbitrary angles of incidence are investigated, and the proportion of energy incident and reflected from the interface are given for typical sonic boom wave forms.

NASA’s high-speed research program

In response to a study by the Office of Science and Technology of the Office of the President that identified technology development to support a long-range supersonic transport as one of the national aeronautical goals, NASA awarded contracts for market and technology feasibility studies of a high-speed civil transport (HSCT) to Boeing Commercial Airplanes and Douglas Aircraft Company in October 1986. Areas to be emphasized in these feasibility studies included market, economics, range, Mach number, fuels, payload, and technology needs. As a result of these studies, NASA initiated a program in 1990 to identify and develop technical and economically feasible solutions to environmental concerns surrounding this type of airplane. A second phase of the program to enhance the economic competitiveness of the vehicle is scheduled to begin in 1994. Results of the early studies showed that the economic viability of a supersonic transport would be tremendously reduced by environmental impact associated with sonic boom which limits overland supersonic flight. Research to develop technologies that would allow supersonic overland flight have been an important part of Phase I of NASA’s high speed research (HSR) program. Results of the feasibility studies that support the current HSR research will be covered in a 10-min overview.

Research and development of high speed, automated mechanical excavation systems for underground construction : Ozdemir, L Proc 2nd International Conference on Innovative Mining Systems, Pennsylvania, 27–29 October 1986P75–82. Publ Pennsylvania: Pennsylvania State University, 1986

Research and development of high speed, automated mechanical excavation systems for underground construction : Ozdemir, L Proc 2nd International Conference on Innovative Mining Systems, Pennsylvania, 27–29 October 1986P75–82. Publ Pennsylvania: Pennsylvania State University, 1986

Research and development of high speed, automated mechanical excavation systems for underground construction : Ozdemir, L Proc 2nd International Conference on Innovative Mining Systems, Pennsylvania, 27–29 October 1986P75–82. Publ Pennsylvania: Pennsylvania State University, 1986

Research and development of high speed, automated mechanical excavation systems for underground construction : Ozdemir, L Proc 2nd International Conference on Innovative Mining Systems, Pennsylvania, 27–29 October 1986P75–82. Publ Pennsylvania: Pennsylvania State University, 1986

The contribution from propeller cavitation to the airborne noise in after spaces on high speed marine vessels

Propeller cavitation is often overlooked as a source of airborne noise on ships, because it is unusual to have manned spaces in the vicinity of the propellers. However, when design considerations require that berthing spaces be located over the propellers, cavitation can produce severe airborne and structureborne noise problems. These problems are especially severe in high speed or high power craft, where the propellers are heavily cavitating and the vessel structure is fairly light. This paper presents the results of measurements aboard a high speed (35 knots) research vessel which identifies the contribution to structural vibration and airborne noise from propeller cavitation. Predictions of the airborne noise existing in a proposed crew living space on a similar vessel show airborne noise levels to be 25 dB in excess of compartment specs at a similar speed. The mechanism of propeller cavitation and procedures to estimate source strength are reviewed. Relationships are presented to describe the power input to the hull structure from this source, and to describe the airborne sound power resulting from this hull vibration. Procedures for the control of propeller generated airborne noise are outlined, along with some of the unsolved technical problems associated with each of these noise control procedures.

Researches in Space Flight Technology

The Forty-Ninth Wilbur Wright Memorial Lecture, “Researches in Space Flight Technology,” was given by Dr. Abe Silverstein, B.S., F.R.Ae.S., F.I.A.S., Director of Space Flight Programs, N.A.S.A., before a large and distinguished audience in the Lecture Theatre, 4 Hamilton Place, on 12th September 1961. Air Marshal Sir Owen Jones, K.B.E., C.B., A.F.C, B.A., D.I.C., F.R.Ae.S., M.I.Mech.E., R.A.F.(retd.), President of the Society, presided. The Lecture was given during the Eighth Anglo-American Aeronautical Conference, and the President was accompanied on the platform by Dr. H. Guyford Stever, President of the Institute of the Aerospace Sciences, and Head of the Mechanical Engineering Department at the Massachusetts Institute of Technology, and Air Commodore W. P. Gouin, R.C.A.F., a member of the Directing Staff of the National Defence College, Canada, and President of the Canadian Aeronautical Institute.As has become the custom, before the Lecture was delivered, the President presented the awards made by the Council for 1961 for outstanding contributions to aeronautics. The list of awards presented on this occasion was published in the June 1961 Journal (p. XXVII).Introducing the Lecturer, the President reminded the audience that the first Wilbur Wright Memorial Lecture was given in 1913 by Horace Darwin. The list of Lecturers, as they would see in their programmes, contained the names of eminent scientists and engineers from America and from this country. They had with them on this occasion a number of those who had given the lecture, among them their very distinguished visitor, Dr. von Kármán.This lecture had been given alternately by a lecturer from this country and one from the United States, with one exception. On one occasion it had been given by the late Professor Ludwig Prandtl—a name well-known to them all.Now Dr. Abe Silverstein was to give the 49th Wilbur Wright Memorial Lecture and had chosen as his subject “Researches in Space Flight Technology.” Dr. Silverstein was Director of Space Flight Programs at the National Aeronautics and Space Administration headquarters in Washington. Before the N.A.S.A. was established on 1st October 1958, Dr. Silverstein had been Associate Director of the Lewis Flight Propulsion Laboratory, Cleveland, a research centre of the National Advisory Committee for Aeronautics, which formed a nucleus of the N.A.S.A. Dr. Silverstein joined the N.A.C.A. in 1929 and spent much time at the Langley Aeronautical Laboratory on wind tunnel design and high speed research until he was transferred to the Lewis Laboratory in 1943 to direct research at the Altitude Wind Tunnel. He had done pioneering work on large scale ram-jet engines and on the supersonic wind tunnels at Lewis.

High–Speed Flying

The Title of this paper gives only the broadest indication of the line it is intended to take. Other papers with similar titles have been read by those connected with the design or aerodynamic side, but this paper is mainly concerned in conveying the pilot's own view of the problems of high-speed flying.The paper is divided under the following main headings:—1.The obstacles to negotiate at high and low altitude.2.The approach to high–speed investigation and means of obtaining test results.3.Present and future requirements of research aircraft.4.Pilot safety measures.5.Some requirements of a pilot engaged in high speed research and development flying.For the most part it is intended only to cover research and development flying. This necessarily entails some reference to combat, which is in itself a separate field.The problems confronting a pilot who sets out to explore the behaviour of contemporary aircraft at high speed are considered first.

Recent Developments in High Speed Research

Much work has been done on compressible flow since the contribution of the Aerodynamics Division to research in this field was last described to the Society by the late C. N. H. Lock in 1937. At that time he was able to review many of the data which were available from other sources, whereas today such a task would be impossible in a paper of this length. We shall confine ourselves here, therefore, to a description of some of the experimental work that has been done during the past few years in the high-speed laboratory of the Division, and to an account of the lines along which it is intended to continue the work in the future.