ENGINEERING RESEARCH INSTITUTE UNIVERSITY OF MICHIGAN ANN ARBOR Progress Report No. 1 A REVIEW OF AIRCRAFT PHOTOGRAPHIC SYSTEMS M, P. MOYLE F. K. LITTLE R. E. CULLEN Project 2197 WRIGHT AIR DEVELOPMENT CENTER, U.S. AIR FORCE CONTRACT AF 33(606)-2368 July, 1954

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN FOREWORD This progress report covers that period of Contract AF 33(616)-2268 devoted to the literature survey and study. The material contained in Part One represents the present state of the art of fog and frost prevention as determined during the study period. The material contained in Part Two describes the nature of the work being done by this laboratory with respect to the optic and thermodynamic problems associated with photographic windows. ii

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN TABLE OF CONTENTS Page FOREWORD ii PART ONE 1 I. INTRODUCTION 1 II. AERIAL-PHOTOGRAPHIC WINDOWS 3 Maintenance of Fog- and Frost-Free Windows 4 Other Proposed Methods 4 III. EVALUATION OF THE PHOTOGRAPHIC SYSTEM 5 A. Photographic Resolution 5 B. The System 7 IV. FUTURE PROBLEMS ASSOCIATED WITH INCREASING AIRCRAFT PERFORMANCE CHARACTERISTICS 7 CONCLUSIONS 8 PART TWO 8 CURRENT ACTIVITY OF THIS LABORATORY 8 BIBLIOGRAPHY 10..__ ~iii

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN A REVIEW OF AIRCRAFT PHOTOGRAPHIC SYSTEMS PART ONE I. INTRODUCTION Reconnaissance may be defined as the act of surveying a region to gain useful information. Modern aerial photographic reconnaissance is, then, reconnaisance conducted from an airplane by means of photography. Aerial photography, as conducted by the Air Force today, has as its main objectives (1) the collection and documentation of large quantities of detailed information, and (2) the interpretation, summarization, and distribution of the final results as rapidly as possible. These objectives are accomplished in three types of missions: photographic reconnaissance, photographic mapping, and instrumentation photography (photography of meters, radar scopes, etc.). During wartime, the aerial-photographic effort of the Air Force is used to secure information concerning the intent and potential of the enemy and to assess the damage inflicted upon him. The import of aerial photography is clear when it is realized that up to eighty percent of all information gained concerning our enemies during World War II was obtained by aerial photographic reconnaissance. In peacetime the photographic effort is directed toward photographing and mapping the world. Considerable nongovernment aerial photography is carried out also in forest surveys and city-planning mapping. The information obtained from any photographic effort results after a train of events has taken place. One may define this train of events as the photographic system. By photographic system, then, is meant the sum of those components which act upon and contribute to the final information. The rapid advancement of aircraft performance characteristics is continually imposing new problems upon the photographic system. A few years ago, a camera was merely held by hand over the side of the cockpit or over an open hole in the floor of the airplane fuselage. The low temperatures and 1

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN pressures encountered in present-day high-altitude flights have brought about the requirements for photographic windows; camera compartments must be sealed and maintained at relatively constant temperature and humidity in order to preserve the film and to avoid temperature gradients in the camera lenses. (It has been reported that temperature gradients in the camera lens reduce the resolution severely (1-7).) The major problems arising from the introduction of windows into the photographic system are fogging, frosting, bending, shattering, and icing. The increasing flight speeds of present-day aircraft have brought about a need for faster camera shutters. Although shutter speeds have advanced considerably, still faster speeds are desirable to eliminate completely the blur caused by the forward motion of the plane. However, this requires a shutter speed so great that the light available for forming the image becomes insufficient. The strip-film, shutterless camera has been designed to eliminate this problem and has experienced considerable success in this respect. In this type of camera, the film moves forward at a speed comparable to that of the aircraft, and thus no shutter is required. Supersonic flight brings about even more complicated problems, such as further compacting of the system. Supersonic aircraft are of such streamlined and narrow cross sections that available space for camera installations has become limited, Shock waves induced in transonic and supersonic flight create problems in optics; temperature gradients and sharp refractiveindex gradients created by the shock waves cause abrupt changes in the path a light ray follows. The advancement of aerial photography is further reflected in the development of night-photographic techniques. Flash photography is possible up to an altitude of 12,000 feet by means of the Edgerton flash unit; this unit consists of a 7200-microfarad, 4000-volt condensor which allows photography at 1/200 of a second, A newer development which is making the Edgerton flash obsolete is the small flash cartridge which has an output of 110 million candle power. For high-altitude photography (photography from an altitude of 25000 feet and above), the magnesium flash bomb is used. This type of bomb is constructed ballistically to fall just outside the cone of vision of the aerial camera and is set to explode at a considerably lower altitude than that at which the aircraft is flying; thus the illumination may be as great as possible on the ground. The weight of these bombs is of the order of 50 pounds, thus the number of pictures which can be taken on a given flight at high altitudes is limited. During World War II, German research in infrared techniques proved to be of great value in advancing the development of infrared devices for night vision. Long-range infrared photography was evolvedy infrared telescopes were developed, etco Much of this work has led to the advancement of these techniques in this country, Radar photography is also becoming an important tool for night reconnaissance missions. 2

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN As the photographic system becomes more complicated greater attention must be given to systems analysis in order to determine the weak link, if any. Each component in the photographic system must be examined to determine whether it is the limiting factor upon the final resolution obtained; the optimum performance with respect to the overall system must be obtained if the final resolution is to be increased. Further improvement in lens design or film characteristics may be useless if the photographic windows are of poor optical quality, if severe mechanical vibrations are present in the camera mounts, or if some other component contributes to the gross loss of resolution in the system. II. AERIAL-PHOTOGRAPHIC WI(DOWS As mentioned previously, higher altitudes and increased flight speeds have brought about the requirement for photographic windows. Many factors must be considered to determine the effect of the introduction of the window on the performance of the photographic system. Obviously, the optical quality of the window glass must be high. Ideally, it should be of the same quality as that of the camera lens in order to produce results comparable to those which could be obtained in the laboratory with the same camera, all other factors being neglected. Due to the high cost of production of optical quality glass, a compromise has been made wherein under present practice, selected plate glass is used, A tolerance system has been established by the Air Force such thrat the optical quality of the window conforms to the type of camera installation used, The two main defects to be looked for in plate glass are wedge angle and surface flatness, Other more obvious defects are striae, bubbles, and foreign matter. During flight at high altitudes$ pressurized compartments may be subjected to pressure differentials as high as ten pounds per square inch; thus, bending of the windows must be prevented by proper choice of window thickness. If the windows bulge, a simple lens is formed and a shift in camera focus is experienced; aberrations may also be introduced by nonuniform bending. Thermal bending and possible shattering must also be considered since fairly large lateral and transverse temperature gradients will exist in the glass, depending upon the method of window defrosting utilized, Other minor problems exist in connection with the windows, especially during flight operation, such as maintenance of clean and scratch-free windows. 5

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN Maintenance of Fog- and Frost-Free Windows One of the major problems associated with the use of photographic windows is the maintenance of the window fog- and frost-free during flight. Extremely low temperatures are encountered at the high altitudes of presentday flights; thus, in order to prevent fog formation on the window, the inner surface of the window must be maintained above the dew point of the cabin air. Many methods have been proposed for prevention and/or removal of fog and frost formation. Systems currently in operation utilize hot-air blasts across the interior surface of the windows. These systems are usually rather bulky and cumbersome and severe limitations are placed on them to prevent image deterioration by the hot-air blast. Laminar-flow nozzles exhausting cabin-temperature air are recommended for long-focal-length cameras, while air 500F hotter than the ambient air may be used for smaller-focal-length lenses7 i.e.,. 24 inches or less. Care must be taken in either case that the blast does not directly impinge on the camera lens. In spite of these restrictions, this system is reported to operate quite well. Conductive coatings are beginning to receive some attention and thus far they show considerable promise. Conductive coatings have been produced for a number of years and have been applied to air-exhaust tanks, wall heaters, fuel-line heaters, etc. It has only been recently, however, that coatings have been produced which are semi-transparent. In the transition zone of 5-40 microns thickness, the requirements of conductivity and light permeability can be met. A number of metals, gold., silver, copper, platinum, cadmium, tin, aluminum, and chromium, have been investigated as possible coating materials. Copper, silver, and gold were found to be the most suitable from a resistance-versus-permeability standpoint. Present trends seem to be toward the use of gold and tin oxides as the coatings. At least two techniques are used for applying the conductive film to the glass-window surface: (1) spraying of a liquid solution of the metal ion on the red-hot sheet of glass, and (2) evaporation of the metal and condensation on the glass under vacuum. Of these two techniques, the latter is preferred since the optical quality of the glass is impaired by the heat required in the former method. The oxide coating obtained is protected by a boro- or florosilicate film which is reported to be nearly as abrasionresistant as the glass itself. Light transmission is reduced about 25 percent by the dual coating,; but this reduction is not considered serious. Although this method of heating has not been adequately tested to date, it appears that it will solve many problems in window defogging. Power-dissipation rates up to 2000 watts/sq ft are reported possible. This is even considered sufficient for deicing in many cases. Other Proposed Methods. The more important methods which have been proposed, but which have received very little operational tests will be mentioned here. 4

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Infrared Heating: This method of heating utilizes radiant energy as the source of heat. The incident radiation causes molecular excitation in the irradiated body and thus the temperature of the body rises. The system has the advantage that it is relatively simple and compact. However, absorption of the incident radiation by the windows is very low -- of the order of 10 to 20 percent in the region where the maximum radiation is produced by presently available sources. Reflection of energy incident upon the metallic frames supporting the window appears to be a problem which may cause fogging of the photographic film during exposure. It is possible that reflections may be reduced to a minimum by proper selection of materials of construction, however. Finally, one other difficulty appears to be the realization of a uniform distribution of energy incident upon the window. Dessicant Hood: A camera hood with a dessicant has been mentioned and an improvement using a dry-air source with a valving system to correct for pressure variation due to altitude changes has been suggested by this laboratory. This system would provide a low-dew-point zone around the camera and provide for pressure fluctuations due to rise and descent of the aircraft The fogging problem would be eliminated by this system; however, no protection is offered for deicing or for fog or frost prevention on the outer surface during rapid descent. External Hot-Air Discharge: An external hot-air discharge has been suggested and given limited tests. In this method, hot air is bled into the boundary layer to maintain the outer surface of the window at a temperature essentially that of the cabin temperature. This method appears promising despite NACA tests which indicated that more heat is required than for an inner hot-air blast. III. EVALUATION OF THE PHOTOGRAPHIC SYSTEM A. Photographic Resolution The main objective in the design of any photographic system is to obtain as high a resolution as possible. The better the resolution, the more information that can be extracted from a given photograph by the photointerpreter, provided the proper contrast is present. In order to determine the relative influence upon the overall resolution by any one of the component parts, it becomes necessary to examine each component individually. Maximum resolution will be obtained by proper adjustment of those components which contribute most to the loss of resolution. The Film. Photographic films and plates being manufactured today are capable of yielding resolution of the order of 50 lines per millimeter for fast films. Slow-speed films such as positive emulsions may resolve as - ~~~~5

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN high as 100 lines/mm, while special emulsions have been made which resolve 1000 lines/mm. Kodak Aerographic Super XX film is used in this country for aerial photography in the visible region while Kodak Aerographic Infrared film, which is about as fast as Super XX, is used in the infrared region. Either film strips or plates may be used; the former type is preferred, however, because it is less bulky and lends itself to automatic operation more readily. Shrinkage of the film is one defect which must be guarded against when using strip film. Film shrinkage leads to distorted results and serious erro in estimated distances and heights. Special films which have a shrinkage coefficient due to processing of the order of 0.6 percent are employed for topographic or mapping photography. The difference between lateral and transverse shrinkage of these films amounts to about 1/10 of 0.6 percent. Proper precautions must also be taken to prevent expansion of the film due to humid conditions. That is, proper humidity control as well as temperature control must be maintained if the film is to retain desirable characteristics. Lenses. Since the beginning of World War II, noticeable advances have been made in the design of photographic lenses. The focal length and aperature of the lenses have steadily increased; lenses with up to 100-inch focal length are common today and special lenses for infrared and wide-angle photography have been designed. Kingslake (J-7) gives an extensive listing of cameras and lenses used during World War II; the many fine lenses in use today are too numerous to mention here. Proper precautions to maintain the lenses at a uniform temperature during operational use appears to be the only improvement required with respect to the lens at this time. Shutters. Probably the most obvious deleterious effect upon resolution is the image shift or blur due to the forward motion of the aircraft. In order to stop the motion and eliminate this blur, faster camera shutters are required. Compur shutters have been operated up to 1/500 of a second and focal-plane shutters at considerably higher speeds, but sufficient light is not usually available for the shutter speeds necessary to stop the motion completely. Development of the S-7 strip camera, a shutterless camera, has yielded remarkable results in stopping image motion. A method of image compensation was designed by Kodak during the war; this method imparts an oscillatory motion to the camera at the instant of exposure and is called the'sweep" method. Mounts. Camera mounts have received some attention but it appears that considerable improvement in their design may be possible. An improvement in design would result in less vibration from the aircraft and camera mechanism and thus improve resolution by reducing image blur. 6

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN B. The System The photographic system as defined previously iay be described by a flow sheet as follows (B-7): Aircraft Illumination % -/| i| Camera Mount I Le ns Fi ms The detail or resolution obtained in a photograph is measured in terms of the number of equally spaced black and white lines per millimeter which are just discernable. Under laboratory conditions, the degreeof re:so.itIn obtainable today is of the order of 35 lines/mm. Under flight conditions however. the errors mentioned previously are introduced. It is reported that the photographic quality before World War II averaged about 8 lines/mm and increased to 12 during the war. At present, the average resolution which can be obtained is of the order of 20 lines/mm; the goal desired is considerably higher than this, i.e., 40-50 lines/mm. Considerable improvement should be possible, then, by proper operation of the system. The loss of resolution due to atmospheric conditions may be impossible to avoid, however. IV. FUTURE PROBLEMS ASSOCIATED WITH INCREASING AIRCRAFT PERFORMANCE CHARACTERISTICS The increasing flight speeds of present-day aircraft and missiles require designs which are streamlined as much as possible; thus needle noses$ flat airfoil sections, and small tapered fuselages are common. Such design limits the available room for the aerial-camera installation. The increasing focal length of aerial cameras may well reach a limit because of space limitations rather than because of design difficulties in the lens system. Camera installations$ then, must be made more compact and in some cases may require mirrors to rotate the image into a different plane from the photographic windows. The optical picture also changes in high-speed flight. A boundary layer will develop, across which very large temperature and density variations occur; a gradual refraction of the light rays will occur when the light passes through the boundary layer. The magnitude of such effects is as yet not definitely established, especially for the case of the turbulent boundary layer, although some attempts are being made to determine it. Shock waves 7,

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN create a more abrupt change in the light path due to the change in density across the shock. It is conceivable that the photograph of an area taken during supersonic flight may be totally different from one obtained in subsonic flight. Fogging and/or frosting of photographic windows probably won't be a problem at the higher flight speeds. due to the effect of aerodynamic heating. It is conceivable that cooling of the windows may be required if aircraft flight speeds of Mach 2 to 3 are realized or if guided missiles are used to carry photographic equipment. It appears then, that aircraft will be flying through a range of speeds in which fogging of vision surfaces may occur at the lower speeds, thus requiring heat additions while cooling of the window surfaces may be required at the higher speeds. CONCLUSIONS From the preceeding discussion, it can be seen that many problems still exist concerning the photographic system and that many more are anticipated as supersonic flight takes place. Research along the lines pointed out should be fruitful indeed. PART TWO CURRENT ACTIViTY OF lT.IS LABORATORY In conjunction with the literature survey reported upon in Part One of this report, this laboratory has been engaged in the study of problems associated with photographic-window fog prevention and removal. Solution of the defogging problem introduces a problem in optics of one form or another$ regardless of the method of defogging. Since most defogging and defrosting systems are of the thermal type, it was felt advisable to investigate the wedge-angle effect produced by the thermal boundary layer. Exploratory calculations showed that the thermal boundary layer actually does act as an optical wedge. The analysis of the wedge angle produced by a plane jet has been begun and some experimental verification is anticipated. At the request of the Air Reconnaissance Laboratory, the investigation of the heat requirements for maintaining fog- and frost-free windows on the McDonnell RF-101 Aircraft during rapid descent has been undertaken. This..~~~~

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN aircraft is the first military aircraft to be fully equipped with photographic windows which are coated with an electrically conductive film produced by the Libby Owens Ford Company. The cases being investigated include steady-state heat requirements and surface temperatures attained at altitude for various Mach-number flights and the transient heat requirements and temperature distributions through the windows during rapid descent from 50,000 feet to sea level. Both analyses are being carried out on the forward oblique and midship windows. The icing problem on the forward oblique window is also being studie The results of this investigation will be issued in a separate report.._. ~9

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN BIBLIOGRAPHY A. Aerial Photography and Photogrammetry 1. Carman, P. D., "Photogrammetric Errors from Camera Lens Decentering," Journal of the Optical Society of America7 5, 951-4, November, 1949. 2. Cooper, M. R., High-Altitude Photographic Tests, Boeing Aircraft Company Report P-7898 Seattle, Washingtonj October$ 1946. 3. Bergstraih, T., Photography from a V-2 at Altitude up to 160 KM, NRL Report R-3083, April7 1947. 4. Duroux, J. W., The Situation in Aerial Photography Today} University of Chicago, Air Weapons Research Centers Ill., (Working Paper No. 33)l February, 1951. 5. Katzy A. H,, "Air Force Photography," ATI Technical Data Digest, 15-23, May 15, 1949. 6. Katz, A. H., "Contributions to the Theory and Mechanics of Photointerpretation from Vertical and Oblique Aerial Photographs," Photogrametric Engineering, June, 1950. 7. MacDonald, D. E., A Symposium on Recent Trends in Aerial Photography, Preface, Technical Note 84, Boston University Optical Research Laboratory, March, 1952. 8. School of Photography, TriMetrogen Mappingp Air Forces Technical School Lowry Field, Colorado) March, 1943l 9. Trorey, L. G., Handbook of Aerial Mapping, Cambridge University Press7 8,| 1950. B. Electrically Conductive Coatings 1. Anon., "Anti-Icing Glass," Aviation Weekj, 50 32, March 14, 1949. 2. Anon., "Electrically Conductive Glass is Useful for Heating Applications," Materials and Methods} 30, 70-71, August, 1949. 3. Anon,> "Hot Windshield Clears Pilots View," Product Engineering, 2_3 286, January, 1952. 10

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN 4o Anon., "Conducting Coatings on Glass," The Engineer, 193* 367, March 14, 1952. 5. Anon., "Tin Plated Glass to Fight Windshield Ice," Aviation Week, 56, 36, May 12, 1952. 6. Anon., "Conducting Films on Glass," Electrical Review (London) 152, 1069-72, May 8, 1953* 7. Anon., "Electrically Conductive Glass3" Metal Progress, 63, 206, June, 1953 8. Anon., 81-E Electrically Conducting Coating, Temporary Bulletin$ Liberty Mirror Division, Libby-Owens-Ford Glass Companyt Brackenridge, Pa.$ March, 1954. 9. Bethge, Bericht Ueber die Eignung Durchsichtiger Metallschichten zur Elektrischen Oberflaechenheizung von Sichscheiben (Report on the Suitability of Transparent Metal Layers for, the Electric Surface Heating of Windshield), Translation Report No. F-TS-1523-R.E. Headquarters Air Materiel Command, Wright Field, Dayton, Ohio. 10. Lyon D. N., and Geballie, T. H., "The Temperature Coefficient of Resist-a ance of Tin-Oxide Coated Electrically Conducting Glass between 1' and 300'K," Review of Scientific Instruments, 21 769-70, August, 1950. C. Fog and Frost Prevention 1. Anon., Summary Report of OS R.D. Project OEM sr-436, OSRD Report No. 18527 (Fogging of Vision Surfaces) National Research Corp.j Boston7 Mass.7 September 1943, Catalogued by ASTIA as ATI 30860. 2. Anon., Bericht Warmeaufnahmevermogen von Gewebescheiben aus Festigkestsglas (Thermal capacity of special laminated glass with wire defrosting grids for aircraft windows) Muhliz-1nion Glasindustrie-AktrEngesellschaft3 April, 1947. 3. Gerlough, P. L. and Ivanoff, W, G. F_ Prevention on the Intersurfaces of Windshield (Model XB-28 airplane) North American Aviation, Inc., Report No. LN2889, 1941. 4. Jaimat D. E.7 Snyder R. M,, and Weudland. D, E., Design Considerations of an Aerial Camera Window Defogging and Defrosting System _1, Boeing Airplane Company Report No. WD-11702, Wichita, Kansas3 1949. 5. Jaima, D, E,7 Snyder, R. M,, and Weud~nd, D. E., Investigation of Optical and Thermaldynamic Properties of an Aerial Camera Window Defogging and Defrosting Systems Boeing Airplane Company Report No. WD-11703, Wichita, Kansas, 1950. 11

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN 6. Kapic, W, F.$ Frost Prevention and Defogging of Windows on XB-35 Airplanes, Northrup Aircraft Inc. Report PP-23, Hawthorne, Calif., August, 1943. 7. Selna7 J., and Zerbe, J. EI A Method for Calculating the Heat Required for the Prevention of F Formations on the Inside Surfaces of Single Pane Bullet - Resisting Windshields During Diving Flight NACA TN No. 1301, 1947. 8. Whiteside P,. C, D., Prevention of Frosting of Transparencies on Descent from High Altitudes' R.A.F. Institute of Aviation Medicine, August, 1950. D. Heat and Mass Transfer 1. Allen$ H. S., and Look, B. S., A Method for Calculating Heat Transfer in the Laminar Flow Region of Bodies. NACA Technical Report 764, 1943. 2. Anon., "Moisture Free Cabin," Aviation Week, D 51, December 18* 1950. 3. Anon., "Heat Loss through Plexiglas," Heating and Ventilating&,0 86-87, May, 1953. 4. Bloomberg, R., "Humidity Control in Plane Cabinst" Heating and Ventilating 49, 75-6, July, 1952. 5. Boelter, L. M. K., Grossman, L. M.) Martinelli, R. C., and Morrinp E. H., An Investigation of Aircraft eaters, Part XXI - Comparison of Several Methods of Calculating Heat Losses from Airfoils, University of Californias NACA TN 1453, 1947. 6. Carslaw, H. S., and Yeager, J. C,, Conduction of Heat in Solids, Oxford Press at the Clarendon, 1947. 7. Chapman, D. R., and Rubesin, M. W,, "Temperature and Velocity Profiles in the Compressible Laminar Boundary Layer with Arbitrary Distribution of Surface Temperature," Journal of the Aeronautical Sciences, 16, September, 1949. 8. Dorrance, W. H.. and Dorej F. J.,'The Effect of Mass Transfer on the Compressible Turbulent Boundary-Layer Skin Friction and Heat Transfer," Journal of the Aeronautical Sciences, 2_1 June, 1954. 9. Dusinberrep G. M., Nuumerical Analysis of Heat Flow McGraw-Hill Book Company, Inc. New Yorko 1949. 10. Eber7 Go R., "Recent Investigation of Temperature Recovery and Heat Transmission on Crones and Cylinders in Axial Flow in the W.OL. Aeroballis ties Wind Tunnel," Journal of the Aeronautical Sciences, 19. January, 1952 12

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN 11, Eckert) E. R. G., Introduction to the Transfer of Heat and i Mass McGrawHill Book Company,, Inc.,. New York, 1950. 12. Frick, C. W., Jro and McCullough, G. B,, A Method for Determining the Rate of Heat Transfer from a Wig or Streamline Body, NACA Technical Report 830. 1945. 13. Gredt, W. H.., "Effect of Turbulence Level on Incident Air Stream on Local Heat Transfer and Skin Friction on a Cylinder,M Journal of the Aeronautical Sciencesj 18- 725-30, November7 1951. 14. Jakob, M., Rose, R. L,. and Spielman, M.,t "Heat Transfer from an Air Jet to a Plane Plate with Entrainment of Water Vapor from the Environment," Transactions, of the American Society of Mechanical Engineers 72, 859-67, August, 1950. 15. Jakob, M., Heat Transfer 1_, John Wiley and Sons, Inc.,, New York$ 1949. 16. Johnson, A. A., Rubesin, M. W., Sauer, F. M., Slack, E. G., and Possner, L.. A Design Manual for Determining the Thermal Characteristics of High Speed Aircraft, AAF Technical Report7 5632. 17. Johnson, H. A.,, and Rubesin, MoW., "Aerodynamic Heating and Convective Heat Transfer Summary of Literature Survey," Transactions of the American Society of Mechanical Engineers, yj, 447,56o July,. 1949. 18. Jonasson, C. W.> Outside Beat Transfer Rates from Airplane Windshields, Boeing Aircraft Co., Seattley Washo, USAF Contr No. W38-033-ac-13013 ATTN No 52190. 19. Kaye, J., "Survey of Friction Coefficients, Recovery Factors and Heat Transfer Coefficients for Supersonic Flow," Journal of the Aeronautical Sciences, 21, February, 1954. 20. Lighthill, M, J.t "Contributions to the Theory of Heat Transfer Through a Laminar Boundary Layer," Proceedings of the Royal Society, 202. 1950. 21. Mickley, H, S., Ross, R, C,, Squyers* A, L,> and Stewart, W. C., Heat Masas and Momentum Transfer for Flow Over a Flat Plate with Blowing or Suction$ Massachusetts Institute of Technology Final Report of Work, September, 1952, 22. Rich, B. R., "An Investigation of Heat Transfer from an Inclined Flat Plate in Free Convection$" Transactions of the American Society of Mechanical Engineers, 7_, 489-99, 1953o 13

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN 23. Rubesin, M. W., and Johnson, H. A., "A Critical Review of Skin Friction and Heat Transfer Solutions of the Laminar Boundary Layer of a Flat Plate," Transactions of the American Society of Mechanical Engineers, 71 383-8, May, 1949. 24. Scherer, R., The Effects of Aerodynamics Heating and Heat Transfer on the Surface of a Body of Revolution in Steady Supersonic Flight, NACA Report 917, October, 1948. 25. Slate7 L. and Murray, M. A Method of Predicting Skin, Compartmentp and Equipment Temperatures for Aircraft. WADC Technical Report 53-119, New York University, July, 1953. 26. Spielman, M., and Jakob, M., "Local Coefficients of Mass Transfer by Evaporation of Water into an Air Jet," Transactions of the American Society of Mechanical Engineers, 75, 385-92, April, 1953. 27. Sibulkin, M., "Heat Transfer near the Forward Stagnation Point of a Body of Revolution," Journal of the Aeronautical Sciences, 19, 570-71, August, 1952. 28. Stadler, J. R., and Jukoff7 P., "Heat Transfer to Bodies Traveling at High Speed in the Upper Atmosphere," Journal of the Aeronautical Sciencesj 15, July, 1948. 29. Van Driest, E. R., "Turbulent Boundary Layer in Compressible Fluids7" Journal of the Aeronautical Sciencesy, 18 March, 1951. E. Icing 1. Bergrunj N. R., A Method for Numerically Calculating the Area and Distribution of Water Impingement on the Leading Edge of an Airfoil in a Cloudy NACA TN 1397, Augustt 1947. 2. Blatz$ R. E., and Haines, A. W., Icing-Intensity Data for the 1952-53 Seasons WADC Technical Report 53-224, catalogued by ASTIA as ATI 18706. 3. Brun, E., and Caron, R., Procede pour determiner les trajectories de corpuseles en suspension dans un fluide, Bulletin du GR.A. No. 3. Translated by G. H. Beguin, University of Michigan, Engineering Research Institute, May, 1953. 4. Brun, E., and Vasseur, M., "La Mecanique des Suspensions," Journal des Recherches du centre National de la Recherche Scientifique Laboratorie d Bellevue, No. 3, 1947. Translated by G. Corcos, University of Michigan Engineering Research Institute, November7 1952. 14

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN 5. Callaghan, E. E., and Serafine, J. S., Method for Rapid Determination of the Icing Limit of a Body in Terms of the Stream Conditions, NACA TN 2914, December, 1952. 6. Dorsch, R. G., and Hacker, Paul T., Photomicrographic Investigation of Spontaneous Freezing Temperatures of Supercooled Water Droplets, NACA TN 2142, July, 1950. 7. Gelder, T. F., Lewis, J. P., and Koutz, S. L., Icing Protection for a Turbojet Transport Airplane: Heating Requirements, Methods of Protection, and Performance Penalties, NACA TN 2866, June, 1952. 8. Glauert, M., A Method of Constructing the Paths of Raindrops of Different Diameters, Rand M No.2025 (4805) ARC Technical Report, November, 1940. 9. Hardy, J. K., Kinetic Temperature of Wet Surfaces a Method of Calculating the Amount of Alcohol Required to Prevent Ice, and the Deviation of the Psychrometric Equation, NACA A.R.R. No. 5G13, 1945. 10. Hasinger and Larson, Use of Infrared Heating for Anti-Icing De-Icing and Defrosting of Aircraft Transparent Areas, A.F. Report 6113. 11. Jakob, M., Defrosting and Ice Prevention, Illinois Institute of Technology Report, 1949. 12. Jones, A. R., Holdaway, G. H., and Steinmetz, C. P., A Method for Calculating the Heat Required for Windshield Thermal Ice Prevention Based on Extensive Flight Tests in Natural Icing Conditions, NACA TN 1434, November, 1947. 13. Knoerschild, E. M., and Larson, L. V., Defrosting of High Performance Fighter Aircraft, A. F. Technical Report 6118, December, 1950. 14. Kushnik, J. L., Thermoq.ynamic Design of Double-Panel Air-Heated Windshields for Ice Prevention, NACA Rest. Bulletin No. 3F24, 1943. 15. Lagenbach, F,, Entersung von Flugzeugsichtsheiben Mittles Ammoniak, Deutsche Forshungsanstall fuer Segflug "Ernst Udett Zentrale Fuer Wissenshaftliches Berichtswesen, Berlin-Adlershof (De-Icing by Ammonia translated by Pittsburgh Plate Glass Company, Pittsburgh, Pennsylvania, 1947). 16. Langmuir, I., and Blodgett, K. B., A Mathematical Investigation of Water Droplet Trajectories, General Electric Rep., 1945 (Available from Office of Technical Services, U, S. Department of Commerce as PB No, 27565). 17. Lewis, W., A Flight Investigation of the Meteorological Conditions Conductive to the Formation of Ice on Airplanes, NACA TN No. 1393, 1947. 15

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN 18. Lewis, W., Icing Properties of Noncyclonic Winter Stratus Clouds, NACA TN 1391, September, 1947. 19. Lewis, W., and Jones, A. R., Recomnended Values of Meteorological Factors to be Considered in the Design of Aircraft Ice-Prevention Equipment, NACA TN 1855, March, 1949. 20. Neel, C. B., Bergrun, N. R., Jukoff, D., and Schlaff, B. A., The Calculation of the Heat Re.quired for Wing Thermal Ice Prevention in Specified Icing Conditions, NACA TN 1479, December, 1947. 21. Schaetzel, S. S., "A Rapid Method of Estimating the Severity of Icing," Aircraft Engineering, July, 1950, 186. 22. Taylor, G. I., Notes on Possible Equipment and Technique for Experiment on Icing on Aircraft, R and M November, 2024, January 15, 1940. 23. University of Michigan, "Airplane Icing Information Course Notes," University of Michigan Extension Service, Ann Arbor, Michigan, March 30 - April 3, 1953. 24. Wieghardt, K., Uber Das Ausblasen von Warmluft Fur Enteiser (Hot Air Discharge for De-Icing), A. A. F. Translation Number F-T-TS-919-RE. Catalogued by CADO as ATI 24536. F. Infrared Photography 1. Clark, W., Photography by Infrared, 2nd ed., John Wiley and Sons, Inc., New York, 1946. 2. Kornfeld, G., "Limits for Infrared Sensitizing," British Journal of Photography, 85, 231-32, London April 15, 1938. (Also Journal of Chemical Physics, 201-02, April, 1938.) 3. Lord, R. C., "The Basic Optics of Infrared Radiation," Electrical Engineering, 68, 689, August, 1949. 4. Odarenko, T. M., German War-Time Developments in Infrared, University Laboratories, New York, March, 1948. G. Infrared Radiation 1. Coblentz, W. W., Investigation of Infrared Spectra, Carnegie Institution of Washington, 1906, 2. Coblentz, W. W., Supplementary Investigations of Infrared Spectra, Carnegie Institution of Washington, 1908. 16

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN 3. Coblentz, W. W., "Infrared Transmission and Refraction Data on Standard Lens and Prism Material," Scientific Paper of the Bureau of Standards, No. 401, U. S. Bureau of Standard.s, Washington, D. C. 4. Florence, J. M., Allshouse, C. C., Glaze, F. W., and Hahner, C. H.J "Absorption of Near Infrared Energy of Certain Glasses," Research Paper 2118, Journal of Research of the National Bureau of Standards, 45, 121-28, August, 1950. 5. Gibson, K. S., "Spectral Filters," Journal of Optical Society of America and Review of Scientific Instrument, 13, 267-80, 1926. 6. Lohausen, Karl$ A., "Fortschritte7 in der Infrarot-Technik, Anwendurgen und Ergebnisse," Zeitschrift des Vereines Deutscher Ingenieure, 94 792-796, 1952, Duesseldorf. 7. Stair, R. and Coblentz, W. W.. "Infrared Absorption Spectra of Plant and Animal Tissue and of Various other Substances," Research Paper RP 830, Journal of Research of the National Bureau of Standards, <, 295-316, September, 1935. 8. Stair, R. and Farick, C. H., "Infrared Absorption Spectra of Some Experimental Glasses Containing Rare Earth and other Oxides," RP 1761, Journal of Research of the National Bureau of Standards, 38, 95-101, January, 1947. H. Optics 1. Baskine, L. L., and Hamilton, L., Wind Tunnel Investigation of the Optical Transmission Characteristics of a Supersonic Turbulent Boundary Layer Northrup Aircraft Co. Report, Hawthorne, Calif. 2. Cheatham, T. P., and Kohlenberg, A., Analysis and Synthesis of Optical | Systems, Part 1 of Technical Note 84, Boston University Optical Research Laboratory, 1952. 3. Liepmann, H'. W., Deflection and Diffusion of a Light R Passing through a Boundary Layer, Douglas Aircraft Co., Report SM-14397t May, 1952. 4. Riggs, L. A., Mueller, C. G., Graham, C. H., and Mote, F. A., "Photographic Measurements of Atmospheric Boil"t Journal of the Optical Society of America, 37, June, 1947. 5. Speak, G. S. Effect of Errors in Filters, Aircraft Windows, and Register Glasses on the Performance of Air Survey CamerasV Royal Aircraft Establishment Tech. Note P.B?. 416, July, 1948. 17

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN 6. Tunnicliffe, W. W., and Ross, G. D., Investigation of Television Photography, Boston University Optical Research Laboratory Technical Note 12, January, 1948. 7. Woodford, E. B., and Nierenberg, R. V., "Effects of Temperature and Pressure on the Focus of Aerial Cameras," Journal of the Optical Society of America, 35, October, 1945. I. Photographic Equipment and Its Design 1. Blitz, M., "Dependence of the Sensitivity of Unsensitized Photographic Emulsions upon Temperature," Journal of the Optical Society of America, 39, 994-1008, 1949. 2. Carman, P. 0., and Carruthers, R. A. F., "Aircraft Camera Mounts - Their Design and Testing," Journal of the Optical Society of America, 41, 311-14, May, 1951. 3. Gewertz, H. R., Report on the Design of the F 3.5 Wide-Angle Camera, Boston University Optical Research Laboratory Technical Note 25, April, 1948. 4. Hopkins, R. E., Final Report on the 144 Inch Camera Lens, Boston Universit Optical Research Laboratory Technical Note 52, April, 1949. 5. Katz, A. H., "Aerial Photographic Equipment and Applications to Reconnaissance," ATI Technical Data Digest, 13-21, November 1, 1948. 6. Katz, A. H., "Camera Shutters," Journal of the Optical Society of America, 539 1-21 January, 1949. 7. Kingslake R., "Recent Developments in Lenses for Aerial Photography," Journal of the Optical Society of America-, 3_7 January, 1947. 8. MacDonald$ D. E., "Problems in Design of Large Aerial Cameras." Society of Automotive Engineers Journal, 58, 66, October, 1950. 9. Tackaberry, R. B., Design of a 100 Inch FJ16 Triplet for Infrared Aerial Photography, Boston University Optical Research Laboratory, Technical Note 111, January, 1954. J. Photographic Film 1. Gunter, R. C., Dimensional Stability of Film, Boston University Optical Research Laboratory Technical Note 55, July, 1949. 18

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN 2. Jones, L. A., and Higgens, C. C., "Photographic Granularity and Graininess," Journal of the Optical Society of America, 36, 203, 1946. K. Photographic Resolution and Detection 1. Aschenbrenner, C. M,, A Comparative Study of Some High-Altitude Photographic Systems, Boston University Optical Research Laboratory, Technical Note 98, June, 1953. 2. Carman, P. P., and Carruthers, R. A. F., "Brightness of Fine Detail in Air Photography," Journal of the Optical Society of America, 41, 1951. 3. Chandlery J. S., Sandviky 0.- and Jones, L. A., Improvement of the Definition in Aerial Photography, Final Report Eastman Kodak Co. Research Labs., Rochester, N. Y. November, 1942. 4. Higgins, G. C., and Jones, L. A., "The Nature and Evaluation of the Sharpness of Photographic Images," Journal of the Society of Motion Picture Engineers, 58, 1952. 5. Howlett, L. E., "Photographic Resolving Power," Canadian Journal of Research, 24, 15, 1946. 6. Kreisman, W. S., Some Theoretical Aspects of Image Degradation as a Function of Shutter Recoil in Aerial Cameras, Boston University Optical Research Laboratory Technical Note 90, October 1952. 7. MacDonald, D. E., A Preliminary Consideration of Air Turbulence on Definition in Aerial Photography, Boston University, Optical Research Laboratory Technical Note 54, June, 1949. 8. MacDonald, D. E., Criteria for Detection and Recognition of Photographic Detail; Part 1, Resolution, Scale and Contract Conditions for Isolated Detail, Boston University Optical Research Laboratory Technical Note 69, September, 1950. 9. MacDonald, D. E., Criteria for Detection and Recognition of Photographic Detailt Part 2 System Performansces Boston University Optical Research Laboratory Technical Note 72, October, 1950. 10. MacDonald, D. E., Some Considerations of Resolution, Sharpness, and Picture Quality in Technical Photography, Boston University Optical Research Laboratory. t. 11. Nagel, M., "Untersuchungen Uber die Erkennbarkeit Kleiner Details in Luftlildaufnahmen," Jahrbuch 1940 der Ieutechen Luftfahrtforschung, Berlin-Adlershof. 19

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN 12. Selwyn, E. W. H., "Definition in Air Photographs, n M. A. P. Scientific War Record, 2.5.16, RAE PH. 764, November, 1946. 15. Watson, J., The Deterioration of Image Quality Caused b a Heated Air Window Defrosting S ystem Boston University Optical Research Laboratory Technical Note 60, 1950. L. Photographic Windows 1. Britton, W. C.> Report on Aerial Photographic Windows> Boston University Optical Research Laboratory Technical Note 63, January, 1950. 2. Britton, W. C., Boston University, Optical Research Laboratory Technical Note 91, November, 1952. 3. Oas, W., Uber die optischen Engenschaften von Flugg;ugverglasungen. Bericht der Junkers Fluggeuz und Motorenwerke Aktiengesellschaft, Dessau. 4. Dillon, R. E., Pressure and Temperature Influences on Aircraft Camera Windows, Boston University, Optical Research Laboratory Technical Note 19, April, 1948. 5. Pitt, R. J., and Matheson, B. M., The Use of Curved Camera Windows in Aerial Photography. Royal Aircraft Establishment, Technical Note PH 438, August, 1950. 6. Staff Optic Section I.A.P., The Selection of Glass for Aircraft Camera Windows, Royal Aircraft Establishmnent, Technical Note PH 427, February, 1950. M. Properties of Glass 1. Gates, J. W., "The Measurement of Refractive Index Gradients in Small Glass Specimens`" Journal of Scientific Instruments3 28, 370-72, December, 1951. 2. Holland, A. J.. and Turner, W. E. S., "The Mechanical Strength of Glass," The Journal of the Society of Glass Technology, 20, 1936. 3. Molby, Fred A., "Index of Refraction and Coefficients of Expansion of Optical Glasses at Low Temperatures," Journal of the Optical Society of Americay 39~ 600-11, July, 1949. 4. Morey, G. W., The Properties of Glass, The Thermal Endurance of Glass, Reinhold Publishing Corporation, New Yorkt 1938. 20

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN 5. Schonborn, H., "Methods of Determing the Thermal Endurance of Glass," Journal of Society of Glass Technology, 20, 1936. 6. Walter, R. J., "Further Studies on Methods for Determining the Thermal Endurance of Glass," Journal of Society of Glass Technologyt 2 193t. 7. Watson, J. T.$ and Holt, W. W., An Experimental Study of the Thermal Endurance of Plate Glass, Boston University, Optical Research Laboratory Interim Technical Report 68-1, June, 1953.......21. _1............

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