ENGINEERING RESEARCH INSTITUTE UNIVERSITY OF MICHIGAN ANN ARBOR PROGRESS REPORT For 1 January 1954 to 1 April 1954 UPPER-ATMOSHPERE WIND, TEMPERATURE, AND PRESSURE MEASUREMENT REPORT NO. C-6 By H. F. SCHULTE Project Engineer Submitted to the Geophysics Research Division. Air Force Cambridge Research Center, Cambridge, Massachusetts. The work reported herein is of a preliminary nature and the results are not necessarily in final form. Approved by N. y Stpencer Poe$ct Supervisor Project 2096 U, S. AIR FORCE, AIR FORCE CAMBRIDGE RESEARCH CENTER CONTRACT NO0 AF 19(604)r545 April, 1954

TABLE OF CONTENTS Page PERSONNEL EMPLOYED DURING PERIOD OF REPORT iii ABSTRACT iv INVESTIGATIONS BEING UNDERTAKEN I 1. Wind Vanes 1 2. Flashing Light System 2 3. Gyroscope Testing 3 4. Instrumentation Construction 3 RESEARCH REPORTS, PUBLICATIONS, AND OTHER SCIENTIFIC ACTIVITIES 4 1. Publications 4 2. Scientific Report 4 3. Technical Meetings and Visits 4 FUTURE PLANS PERSONNEL AND ADMINISTRATION FISCAL INFORMATION 6 PROPERTY ACQUIRED DURING THE PERIOD 6 ii

PERSONNEL EMPLOYED DURING THE PERIOD OF REPORT W. G. Dow Consultant H. V. Dada Data Analyst Part-time (student) J. A. Foster Research Assistant Part-time (student) P. Hogan Data Analyst Part-time (student) G. Hok Consultant W, G. Kartlick Research Technician A. A. Kirsons Data Analyst Part-time (student) D. L. McCormick Machinist T. Pattinson Research Technician Part-time (student) H. F. Schulte Project Engineer H. S. Sicinski Research Physicist N. W. Spencer Project Supervisor iii

ABSTRACT The present status of the wind-vane development program is discussed and a favorable outcome is indicated. The results of a life test on the flashing light system are presented and the progress on other phases of instrumentation construction for the June, 1954, Aerobee missile is described. A technical paper on rocket instrumentation was accepted for publication in the Proceedings of the I.R.E. during the quarter. iv

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN UPPER-ATMOSPHERE WITND, TEMPERATURE, AND PRESSURE MEASUREMENT INVESTIGATIONS BEING UNDERTAKEN 1. Wind Vanes The data obtained from the recent series of Supersonic Wind Tunnel tests* were analyzed during this period. The results confirmed the preliminary estimate that the wind-vane cross section be of the order of 0.002 inch if adequate response is to be obtained. Similarly, the approximate upper limit on the moment of inertia of the entire rotating mass(wind vane, bearing, and transducer) was experimentally confirmed. The tests also verified the theoretical prediction that the angle between the wind vane and the cone axis can have a maximum limiting value of twice the cone's angle of attack, provided that the angle of attack is not greater than the half-angle of the cone. This is an important factor since it ultimately determines the maximum angle throughout which the instrumentation must be able to provide useful data. Regarding accuracy of measurement, the wind-tunnel tests indicated a lack of adequate reproducibility of results for angle measurement to 1 part in 500. This was anticipated in view of the particular bearing design and to some extent the transducer system Iutilized on this first model. The -experienice gained iin the'se preliminary tests and in. later. bench. testing; of new bearing'designs and circuit modifications. indicates, at.this time, that the.:esign- and construction'of a'bearing and-: transducer system to- provide, the requisite'accuracy.and reprdducability'-can be achieved. The wind-vane bearing design must comply with the following re uirements: 1. Minimum friction, 2. Minimum lateral bearing-play, 3. Minimum end bearing-play, 4. Minimum rotating mass, 5. Suitable configuration for attachment of transducer element. * Progress Report C-5, December, 1955, Contract No. AF 19(604) -54-5. ______ _________________________ 1 ____________________1

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN At present, emphasis has been placed on the development of a bearing system using two-synthetic -sapphire "center jewels" and-a 0.060-inchdiameter shaft of hardened ground, and polished drill rod which passes through the precision-ground center holes in the jewels. When assembled, the system has the appearance of a tiny-,';two-bearing line shaft, with the wine vane attached to one end of the shaft and the transducer element attached to the other. Shaft rotation is translated into an electrical signal by the variation in capacitance between a small metallic paddle affixed to the rotating shaft and a fixed plate or plates mounted nearby. This small variable capacitor is connected across a high-Q, parallel-resonant, tuned circuit which is inductively coupled to a crystal-controlled, constant output signal generator. A shunt-connected, vaxaum-tibe diode detector is also connected across the tank circuit and acts as a peak-reading, vacuum-tube voltmeter. Intially the tank circuit is tuned off-resonance and then as the capacitance varies in accordance with shaft rotation, the tank circuit is tuned closer to or farther from resonance, depending, of course, upon the magnitude and sign of the capacitance change. If the energizing voltage to the coil remains constant, the peak-reading VTUM will provide a rectified d-c output voltage whose magnitude will vary as the tank-circuit tuning is varied and thus it is possible to calibrate angular degreees of shaft rotation directly in terms of a d-c voltage. Investigation of the d-c stability and reproducibility of this circuit are now in progress. Wind-tunnel tests indicate the presence of a small amount of noise fluctuation (approximately 1 part in 250) and a certain amount of d-c shift. This latter phenomenon is apparently associated with the change in pressure in the wind-tunnel section during the supersonic run. Laboratory vacuum equipment will be used to study and minimize this effect. 2. Flashing Light System Life tests on the flashing light system used for photographic illumination have shown that the energy-storage capacitor originally chosen for use in this system is not adequate. The energy-storage unit consists of two paralleled, 1-microfarad, 600-volt, metallized-paper capacitors, charged to a peak value of 460 volts, The capacitors are discharged through the flash tube in approximately 1 millisecond to a level of 20 volts. The measured discharge: current:ha's.a peak value of about 20-' amperes per capacitor, In virtually all cases of failure, the capacitance slowly decreases in value until the capacitor is virtually an open circuit. It is assumed that the extremely thin metallic film (0.000 003 inch) cannot withstand the high current surges present in the application. Since the metallized capacitors were chosen primarily for their small size, the substitution of larger conventional paper capacitors requires some redesign of the power-supply package, which is now in progress, --------- - 2

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN - 3. Gyroscope Testing To facilitate final gyroscope balancing and testing, a dustresistant enclosure was constructed to allow balance adjustments to be made with less chance of bearing contamination. The box contains a large, sloping, glass front for observation, a gyro control panel, and an externally mounted blower which supplies filtered air at a slight positive pressure, the object being to minimize admission of airborne dust and lint through the hand-hole access area. The box is now in use and final adjustments are now in progress on one of the two Bendix J-8 gyroscopes to be flown in the June, 1954, Aerobee. 4. Instrumentation Construction Fabrication of the many components and sections of this project's instrumentation for the forthcoming Aerobee firing is proceeding approximately on schedule. 3..9_

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN RESEARCH REPORTS, PUBLICATIONS, AND OTHER SCIENTIFIC ACTIVITIES 1. Publications a. A paper entitled "Rocket Measurements of Upper-Atmosphere Ambient Temperature and Pressure in the 30 to 75-Kilometer Region", by H. S. Sicinski, N. W. Spencer, and W. G. Dow* was published in the February, 1954, issue of the Journal of Applied Physics. b. A paper entitled "Rocket Instrumentation for Reliable UpperAtmosphere Temperature Determination" by N. W. Spencer, H. F. Schulte and H. S. Sicinski was accepted for publication in the Proceedings of the Institute of Radio Engineers. (Summary: This paper briefly describes rocket-borne electronic equipment which has been developed and utilized in the determination of ambient atmospheric pressure and temperature. In the design.of the equipment, emphasis has been placed on reliability of operation, and on the ability to produce data of significant accuracy. Typical resulting curves of amibient pressure and temperature are presented.) 2. Scientific Report A Scientific Report on the Paschen's Law Experiment flown on the September, 1951, University of Michigan Aerobee (USAF 18)** is nearing completion. The report will be abstracted, also, for publication in a suitable technical journal. -3. Technical Meetings and Visits Professor W. G. Dow and Mr. N. W. Spencer attended'the February, 1954, meeting of the Upper Atmosphere Rocket-Research Panel held in Washington, D.C. A two day meeting was held on February 25 and 26, 1954, at the University of Michigan to discuss critically the results and the methods employed at present for.measurement of upper-atmosphere amibient temperature, pressure, and density. The meeting was attended by the following: * Progress Report C-4, October, 1953, Contract No. AF 19(604)-545. *Progress Report A-8, October, 1953, Contract No. AF 19(122)-55. ________________________________ 4 ________________________________

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Air Force Cambridge Research Center M. Dubin R. A. Minzner Naval Research Laboratory R. J. Havens University of Michigan - Aeronautical Engineering Department - Signal Corps Project F. L. Bartman L. M. Jones M. H. Nichols E. J. Schaefer University of Michigan - Electrical Engineering Department - Air Force Project J. A. Foster H. F. Schulte H. S. Sicinski N. W. Spencer Members of this project also participated in discussions with Mr. Minzner and Mr. Dubin concerning specific details of the forthcoming Aerobee aspect-missile firing in which both agencies will have equipment. A tentative firing date during the week of June 14, 1954 (subject to range availability) was agreed upon. FUTURE PLANS Maximum effort will be expended on completion and testing of the instrumentation to be flown in the June, 1954, Aerobee. Since the next reporting period includes the tentative firing date, the field trip and firing will also be included in the forthcoming activities. PERSONNEL AND ADMINISTRATION The following personnel change occurred during the period of this report: a) Mr. H. V. Dada was added to the staff and will do part-time data analysis and computational work. He received his M.S.E. in Electrical Engineering from the University of Michigan and is presently studying for the Ph. D. _______________________ 5 ____________________

- ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN Formation of the Advisory Committee-* to discuss pertinent project matters has been completed. The committee consists of: W. G. Dow, Professor of Electrical Engineering R. G. Folsom, Professor of Mechancial Engineering and Director of Engineering Research Institute M. H. Nichols, Professor of Aeronautical Engineering N, W. Spencer, Project Supervisor The Holloman Air Development Center Flight Determination Laboratory was contacted on March 3, 1954, concerning the status of the additional missile-velocity data (to facilitate "T"-day analysis) this project requested in September, 1953 ** FISCAL INFORMATION As of March 31, 19514, approximately forty-three percent of project funds available and anticipated as of September 1, 1953, will be expended. Since existing funds are budgeted to December 31, 1954, the rate of expenditure continues to be satisfactory. PROPERTY ACQUIRED DURING.THE PERIOD Following is an unofficial list of property acquired during the period of this report: a) Binolcular microscope b) Routine miscellaneous supplies. * Progress Report Ct-5 December, 1953, Contract No. AF 19(604)-545. ** Progress Report C-4, October, 1953, Contract No, AF'l(604)-545. ~~~~____~~______...._ 6 __________?