FLIGHT TEST SONIC BOOM MEASUREMENTS

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP71B00822R000100280001-7
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 25
• Document Creation Date: December 19, 2016
• Document Release Date: January 30, 2003
• Sequence Number: 1
• Publication Date: June 1, 1965
• Content Type: REPORT

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COPY ? CIf 9-
ADVANCED DEVELOPMENT PROJECTS
B U R BAN K. CAL I FOR N I t
REPORT NO. SP-815
DATE 1 June 1965
COPY NO..
I-
TITLE FLIGHT TEST SONIC BOOM MEASUREMENTS
STAT
Clarence L. JO nson
Vice President
Advanced Development Protects
On file USAF release REVISIONS
instructions apply. DATE
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 P-31i
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~ e-,
0~ ? CALIFORNIA COMPANY
A D I V I S 1 0 N O F L O C K H E E D A I R C R A F T C 0 R P C R A - I O N
Sonic boom overpressures of 1.2 to 1.7 pounds per square foot were
measured under the aircraft track during the YF-12A record rune.
The Match number range was 2.6 to 3.1 M. at altitudes of 60,000 to
76,500 feet above terrain. Fifteen nautical miles to the side of the
aircraft track the overpressure was reduced from 1.7 to 0.8 PSF and
the boom was described as "very faint".
Fifty-one sonic boom recordings were obtained in the low superecnic
Mach number range. The maximum overpressure was 5.0 PSF and
the minimum was 0.3 PSF. Statistically, 4% of these data points
were between 4.0 and 5.0 PSF, 67% were between 2.0 and 4.0 FSF
and 29% were less than 2.0 PSF.
The data are the average of five microphones individually recorded
by an oscillograph. The system was calibrated using AC calibrations
in the frequency range from approximately 400 to 1200 cps. Present
plans are to obtain additional data using five DC calibrated pressure
transducers.
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 SP- 113
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yoo&ft~ ? CALIFORNIA COMPANY
TABLE OF CONTENTS
Title
Summary
Table Of Contents
Figure Index
Discussion
YF-12A Record Runs
Observers' Comments
Atmospheric Conditions
Supplementary Data
Instrumentation
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pCALIFORNIA COMPANY
A D I V I S I O N O F L O C K H E E D A I R C R A F T C O R P O R A 1 1 J N
FIGURE INDEX
No. Title
Pa !Na
Comparison of Measured Sonic Boom
1.
Overpressure With Measured -B-58 Data.
YF-1ZA Record Runs.
2. Comparison of Measured Sonic Boom
Overpressure With Volume & Lift Theory.
Y'F-1ZA Record Runs.
3. Tracing of Oscillograph Boom Recordings.
4. Tracing Of Oscillograph Boom Recordings.
5. Tracing Of Oscillograph Boom Recordings.
6. Tracing Of Oscillograph Boom Recordings.
7. Track For Sonic Boom Recordings During
Record Runs.
8. Local Weather Balloon Data, 1 May 1965.
9. Wind Data, 1 May 1965.
10. Comparison Of Measured Sonic Boom
Overpressure With Measured B-58 58 Data.
YF-1ZA Practice Run.
11. Comparison Of Measured Sonic Boom
Overpressure With Measured B-58 Data.
Condition I.
12. Comparison Of Measured Sonic Boom
Overpressure With Volume & Lift Theory.
Condition I.
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 Approved For Release 2003/04/17 : CIA-RDP71B00822R000100280001-7 "219 e ii;
G~K/teACL CALIFORNIA COMPANY
FIGURE INDEX (Continued)
No. Title
13. Comparison of Measured Sonic Boom
Overpressure With Measured B-58 Data.
Conditions I. II and II to III.
14. Comparison Of Measured Sonic Boom
Overpressure With Volume & Lift Theory.
Conditions I. II and II to M.
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Pajja No.
 SP?-815
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? CALIFORNIA COMPANY
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L O C K H E E 0 A I R C R A F T C O R P O R A 1 1`) N
A D I Y I 5 I 0 N O F
DISCUSSION
YF-12A Record Runs
The sonic boom overpressures meadnzed during the YF-1ZA record:
runs. are shown in Figures 1 through 6. Figures 1 and 2 show over-
pressures .of 1.2 to 1.7 pounds per square foot measured at a record-
lug station located under the aircraft track. Also shown is a measure-
Mont =Wde:apps'oX11 tely 15 nautical miles to the side of the aircraft
track during the 500 kilometer run. This data point shows a reduc
tion in overpressure from 1.7 to 0.8 PSF, slightly more than 50%.
The Mach numbers for the various runs were 2.6 to 3.1 M. and alti-
tude was 60,000 to 76,500 feet above the local terrain level. Note
that the two recording stations were located outside of the traps for
the course, therefore the Mach numbers and altitudes at time of data
recording were somewhat different-than the records established over
the official course. Figure 7 shows the location of the two data
recording stations in respect to the aircraft trick.
Figure 1 compares the measured YF-12A data with measured B-58
data. Although there is a disparity in the size and Mach number of
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 'i '-blh
Page
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CALIFORNIA COMPANY
A D I V I S I O N O F L O C K H E E D A I R C R A F T C 0 R P O R A T 1 U N
YF-12A Record Runs (continued)
the two aircraft, the measured overpressures are in good agreement.
Figure .Z compares measured and theoretical YF-IZA data. Measured
values are consistently higher than would be expected from theory.
The theoretical data are based the "signature" curve for the Y `-lZA.
developed by the ADP Aero/Thereto department.
Figures .3 through 6 are actual recorded data tracings. These figues
also show the layout and spacing of the five microphones and the
operator's comments on the nature of the boom. Note that the sequence
of the pressure pulses can be used as an indication of the aircraft fligbt
path. For example, Figure 3 shows microphones D, E. A, C and B
pulsing in sequence, indicating the aircraft approached from the WSW.
Also of interest is the difference in peak pressure recorded by indi-
vidual microphones. Figure 3 shows a 0.5 PSF difference between
microphones B and D located 100 feet apart. This, represents 33'% of
the average of the five microphones. Figure 5 shows a 0.46 PSI`
difference between microphones A and E located 50 feet apart, which
is 27% of the average for the five microphones.
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Approved For Release 2003/04/17: CIA-RDP71 B00822R000100280001-7 Page 11
? CALIFORNIA COMPANY
A D I V I S I O N O F L O C K H E E D A I R C R A F T C O R P O R A T r O N
Observers' Comments
Experienced observers located at the YF-12A service area commented
that the booms were generally quite light. As shown in Figures 3
through 5, the operator at the recording station under the aircraft track
reported "medium" booms. Figure 6 shows that the operator at the
recording station to the side of the aircraft track reported that the
500 km course boom wai 'Avery faint.". This is consistent with the data
and only indicates the effect of different locations with respect to the
aircraft track.
Atmospheric Conditions
Figures 8 and 9 show the ambient air temperature variation and wind
direction and velocity measured on the day of the runs. At the altitudes
concerned, the temperature was within + 5?C of standard and wind
velocity was 10 knots or less, varying from West to North. The --naxi-
mum wind velocity was approximately 65 knots at 40,000 feet from
WSW. These data are included because of the possible effects on the
sonic boom recordings.
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'WkAZ' ? CALIFORNIA COMPANY
A D I V I S I O N O F L O C K H E E D A I R C R A F T C 0 R P C R A T O N
Supplementary Data
Figure 10 shows YF-12A data obtained during a practice flight prior to
the actual record runs. This data point also agrees well with measured
B-58 data.
Figures 11 and 12 are data obtained from a different series of fli&ht tests
In this case, the recording station was located at 5000 feet terrain level
and all of the data were obtained in the low supersonic Mach number
range at altitudes from 25,000 to 42,000 feet above terrain. The maxi-
mum measured overpressure was 5.0 PSF and the minimum was 7.3
PSF. Statistically, 51 total data points were measured of which 4%
were between 4.0 and 5.0 PSF, 67% were between 2.0 and 4.0 PSF, and
29% were less than 2.0 PSF. The largest variations were at lower
altitudes where the aircraft was near "cutoff" Mach number; that is,
the minimum supersonic Mach number at which a sonic boom Will
reach the ground. Aircraft attitude, flight path and atmospheric vari-
ations become more critical at this condition. Overpressure variations
of this order undoubtedly will be typical of actual service operation.
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 Approved For Release 2003/04/17 : CIA-RDP71B00822R000100280001-7
age 16
OG CAL1fORNIA COMPANY
A D I V I S I O N O F L O C K H E E D A I R C R A F T C O R P O R A T O N
Instrumentation
All of the foregoing data were obtained with the same equipment used
by Lockheed during the FAA Oklahoma City tests. Similarly, the
I
microphones and recording system were calibrated using AC call rat 4:n=+
in the frequency range from approximately 400 to 1200 cps. It can be
argued that DC calibrations are inherently more accurate because there
are few sonic boom frequencies above 100 cps. Figures 13 and 14 show
data obtained over a wide Mach number and altitude range but measured
with a single, DC calibrated pressure transducer. In general, the mea-
sured overpressures were less than shown in Figures I through 12.
However, other effects may have been introduced since these were es-
sentially "unsolicited" tests and the flight conditions were not as well
controlled as the record runs. Present plans are to obtain additional data
using five DC calibrated pressure transducers.
Approved For Release 2003/04/17 : CIA-RDP71B00822R000100280001-7
 Approved For Release 2003/04/17: -CIA-?$22R000100280001-7
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