thermal response and reusability testing of advanced
TRANSCRIPT
• ' t. ~ . '
AEDC-TR-79-62 • = APR 2 4 1981
Thermal Response and Reusability Testing of Advanced Flexible Reusable Surface
Insulation and Ceramic RSI Samples at Surface Temperatures to 1,200°F
E. C. Knox ARO, Inc.
April 1981
Final Report for Period April 4 - 5, 1979
Approved for public release; distribution unlimited.
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ARNOLD ENGINEERING DEVELOPMENT CENTER ARNOLD AIR FORCE STATION, TENNESSEE
AIR FORCE SYSTEMS COMMAND UNITED STATES AIR FORCE
NOTICES
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Qualified users may obtain copies of this report from the Defense Technical Information Center.
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This report has been reviewed by the Office of Public Affairs (PA) and is releasable to the National Technical Information Service (NTIS). At NTIS, it will be available to the general public, including foreign nations.
APPROVAL STATEMENT
This report has been reviewed and approved.
JOSEPH F. PAWLICK, JR., Lt Colonel, USAF Director of Test Operations Deputy for Operations
Approved for publication:
FOR THE COMMANDER
Cf JAMES D. SANDERS, Colonel, USAF Deputy for Operations
UNCLASSIFIED REPORT DOCUMENTATION PAGE
! REPORT NUMBER ~2 GOVT ACCESSION NO
L AEDC-TR-79-62
4 T ITLE ( ~ d Subttlte) THERMAL RESPONSE AND REUSABILITY TESTING OF ADVANCED FLEXIBLE REUSABLE SURFACE INSULATION AND CERAMIC RSI SAMPLES AT SURFACE TEMPERATURES TO 1,200°F
7. AUTHOR(.)
E. C. Knox, ARO, Inc., a Sverdrup Corporation Company
S PERFORMING ORGANIZATION N ~ E AND ADDRESS
A r n o l d E n g i n e e r i n g D e v e l o p m e n t C e n t e r / D O A i r F o r c e S y s t e m s Command A r n o l d A i r F o r c e S t a t i o n , T e n n e s s e e 37389
I|1. CONTROLLING OFFICE NAME ANO ADDRESS
NASA/JSC/ES3 H o u s t o n , T e x a s 77058
14 MONITORING AGENCY NAME & ADDRESS(JLdlIIerenf Irom Conlrolt |n80fl ico)
READ INSTRUCTIONS BEFORE COMPLETING FORM
3 RECIPIENT'S CATALOG NUMBER
S TYPE OF REPORT & PERIOD COVERED F i n a l R e p o r t , A p r i l 4 - 5 , 1979 B PERFORMING ORG. REPORT NUMBER
S. CONTRACT OR GRANT NUMBER(s)
10. PROGRAM ELEMENT, PROJECT, TASK AREA& WORK UNIT NUMBERS
P r o g r a m E l e m e n t 921E01
12. REPORT DATE April 1981 13. NUMBER OF PAGES
47 IS. SECURITY CLASS. (0! fhic raporfJ
UNCLAS S I F I ED
ISa. DECLASSI FICATION / DOWNGRADING SCHEDULE
N/A 16. DISTRIBUTION STATEMENT (ol thlc Rapowl)
A p p r o v e d f o r p u b l i c r e l e a s e ; d i s t r i b u t i o n u n l i m i t e d .
17. DISTRIBUTION STATEMENT (ol Ihe abstract entered In Block 20. I I dllfarm~t born Raporf)
IS. SUPPLEMENTARY NOTES
A v a i l a b l e i n D e f e n s e T e c h n i c a l I n f o r m a t i o n C e n t e r (DTIC) .
I9. KEY WORDS (CMfJnue on reverae aide II neceaaary ~ d I ~ n t l ~ ~ block numbe~
m a t e r i a l t e s t i n s u l a t i o n f l e x i b l e f a b r i c c e r a m i c t e m p e r a t u r e e x p o s u r e
ZO ABSTRACT (C~ l l nae m rav~aa aide I I n c c o a e ~ ~ d I d M f i ~ ~ block n m ~ r )
T e n - m i n u t e e x p o s u r e t e s t s w e r e p e r f o r m e d on s a m p l e s o f an a d v a n c e d f l e x i b l e r e u s a b l e s u r f a c e i n s u l a t i o n (AFRSI) made o f a q u a r t z g l a s s f a b r i c a n d s a m p l e s o f a c e r a m i c t i l e r e u s a b l e s u r f a c e i n s u l a t i o n ( R S I ) . The s a m p l e s w e r e t e s t e d i n a w i n d t u n n e l a e r o t h e r m a l e n v i r o n m e n t t h a t c a u s e d t h e s a m p l e s u r f a c e t o h e a t t o 1 , 2 0 0 ° F d u r i n g e a c h e x p o s u r e . No s e r i o u s d e f e c t s i n t h e s a m p l e s w e r e d e t e c t e d a s a r e s u l t o f t h e e x p o s u r e . The t e s t
FOR. 1473 ED,T, ON OF 1 NOV SS IS OBSOLETE DD , j AN ~3
UNCLASSIFIED
UNCLASSIFIED
20. ABSTRACT. C o n c l u d e d
t e c h n i q u e u s e d p r o v i d e d a s u i t a b l e a e r o d y n a m i c h e a t i n g e n v i r o n m e n t f o r c a n d i d a t e m a t e r i a l s e v a l u a t i o n .
AFgC Amald AFS Telm
UNCLASSIFIED
AEDC-TR-79-62
PREFACE
The work reported herein was conducted by the Arnold Engineering Development Center (AEDC), Air Force Systems Command (AFSC), at the request of the National Aeronautics and Space Administration (NASA), Johnson Space Center (JSC), Houston, Texas, for the NASA/Ames Research Center (ARC), Mountain View, California. The results of the test were obtained by ARO, Inc., AEDC Group (a Sverdrup Corporation Company), operating contractor for the AEDC, AFSC,. Arnold Air Force Station, Tennessee, under ARO Project Number V41C-56. The NASA-JSC program manager was Mr. Bill Moseley (E53), and the NASA-ARC program managers were Messrs. Howard Goldstein and Roy Wakefield. The data analysis was completed on June 28, 1979, and the manuscript was submitted for publication on August 2, 1979.
AEDC-TR-79-62
C O N T E N T S
1.0 I N T R O D U C T I O N ........................................................ 5
2.0 A P P A R A T U S ........................................................... 6
2. I Test Facility .......................................................... 6
2.2 Test Article ........................................................... 6
2.3 Test Ins t rumenta t ion . . . . . . . . . . . . . . . . . . . . . . ' . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.3.1 Tunnel Condi t ions ............................................... 7
2.3.2 Test Data ....................................................... 7
3.0 T E S T D E S C R I P T I O N .................................................... 8
3.1 Test Cond i t ions and P rocedure .......................................... 8 3.1.1 Test Cond i t ions .................................................. 8
3.1.2 Test P rocedure .................................................. 8
3.2 Data Reduct ion ....................................................... 10
3.2.1 IR System P h o t o g r a p h s o f Sample Surface Tempera tu re . . . . . . . . . . . . . . . 10
3.2.2 Sample Tempera tu res ............................................ 10
3.2.3 Hea t -Trans fe r Measurements ...................................... 12
3.3 Uncer ta in ty o f Measurements ........................................... 12
3.3. ! General ........................................................ 12
3.3.2 Tunne l Condi t ions ............................................... 13
3.3.3 Test Data . . '. .................................................... 13
4.0 R E S U L T S A N D D I S C U S S I O N ............................................. 13
4.1 Sample Test Env i ronmen t .............................................. 14
4.2 Test Results .......................................................... 14
5.0 C O N C L U D I N G R E M A R K S ............................................... 15
R E F E R E N C E S .......................................................... 16
I L L U S T R A T I O N S
Figure
1. Tunne l C ................................................................ 17
2. Instal lat ion P h o t o g r a p h and Sketch .......................................... 18
3. P h o t o g r a p h s o f Test Samples ............................................... 20
4. Details o f Test Samples .................................................... 24
5. T h e r m o c o u p l e Loca t ions in Test Samples ..................................... 29
6. P h o t o g r a p h s o f Damaged Samples .......................................... 31
3
A E DC-TR-79-62
Figure Page
7. AFRSI Spectral Emissivity ................................................. 33
8. Blackbody and AFRSI Total Emissivity ...................................... 34
9. Flow-Field Shadowgraph of Sample 2, Run 23 ................................ 36
10. Heat-Transfer and Shear Stress Distributions on Wedge Surface . . . . . . . . . . . . . . . . . 37
11. IR Camera Photograph Indicating Surface Temperature of Sample 2, Run 23 . . . . . 38
12. Influence o f Sample Emissivity on IR Camera Temperature Calibration . . . . . . . . . . . 39
13. Temperature Response of Sample 2 to Test Environment, Run 23 . . . . . . . . . . . . . . . . 40
TABLES
1. Test Summary ............................................................ 43
2. IR System Color /Tempera ture Calibration ................................... 44
APPENDIX
A. SURFACE E Q U I L I B R I U M T E M P E R A T U R E C O M P U T A T I O N . . . . . . . . . . . . . . . 45
N O M E N C L A T U R E ....................................................... 46
4
AEDC-TR-79-62
1.0 INTRODUCTION
The structure of the space shuttle orbiter will be protected from the reentry thermal
environment by a system of ceramic Reusable Surface Insulation (RSI) tiles that can be i'eplaced quickly, as necessary, after one or several missions. This thermal protection system
design allows quick turn around of an orbiter subsequent to a mission and thereby makes the
shuttle concept cost effective; however, the cost of this system is significant. In an effort to recluce the total insulation costs, the National Aeronautics and Space Administration/Ames Research Center (NASA/ARC) has developed a less,:expensive Advanced Flexible Reusable
Surface Insulation (AFRSI) for possible use on th~ leeward surfaces of the orbiter as a replacement for the ceramic tiles. The AFRSI wdl experience relatively low heating rates and
is expected to reach an equilibrium surface temperature of about 1,200°F.
The suitability of the AFRSI requires testing in a simulated environment prior to
commitment for use on the orbiter. Radiant heating facilities provide the required temperature but not the other necessary conditions, most notably the surface shear. Plasma
jet facilities provide the desired temperature and shear, but the shear and heating rates are often too high. Moreover, particles in the flow for these facilities can produce serious material erosion, distorting the performance evaluation. The AFRSI needs to be tested in a
clean, convective heating environment that provides realistic surface shear. The AEDC yon K~rm~n Gas Dynamics Facility (VKF) Hypersonic Wind Tunnel (C) satisfies these requirements and was selected for testing the AFRSI samples largely because several
materials evaluation tests'have been conducted in this facility over the years. A summary
description of the testing techniques developed from these tests is presented in Ref. !.
t
In the present application the desired test environment was obtained by utilizing a wedge to support the materials samples and inclining it at a 25-deg angle to the Tunnel C Mach number 10 flow. The desired surface temperature and shear values, which were the primary
test conditions, were provided.
The principal objectives of the subject test were to determine the thermal response and reusability of the AFRSI thermal protection materials. A second objective was to obtain performance comparisons between AFRS! materials and the ceramic RSI tiles which the AFRSI are intended to replace. This report presents a description of the test technique
utilized and some typical test results•
A E O C-T R -79-62 t
2.0 APPARATUS
2.1 TEST FACILITY
Tunnel C (Fig. l) is a closed-circuit, hypersonic wind tunnel with a Mach number l0
axisymmetric contoured nozzle and a 50-in.-diam test section. The tunnel can be operated continuously over a range of pressure levels from 200 to 2,000 psia with air supplied by the
VKF main compressor plant. Stagnation temperatures sufficient to avoid air liquefaction in the test section (up to 1,800°F) are obtained through the use of a natural gas-fired
combustion heater in series with an electric resistance heater. The entire tunnel (throat, nozzle, test section, and diffuser) is cooled by integral, external water jackets. The tunnel is
equipped with a model injection system, which allows removal of the model from the test section while the tunnel remains in operation. A description of the tunnel may be found in the Test Facilities Handbook (Ref. 2).
The local flow conditions needed to meet the test requirements were produced by using a
large wedge to process the tunnel free-stream Mach number l0 flow through an oblique
shock wave. Varying the wedge angle and the tunnel free-stream conditions tailored the flow conditions on the surface of the wedge (where the material samples were placed) to provide the needed local flow conditions. The wedge (Fig. 2) is a 15-in.-wide by 41.5-in.-Iong flat
plate mounted on a 13-deg wedge block. The flat plate has a i.5-in, backstep occurring 17.5 in. aft of the sharp leading edge, which permits mounting material samples flush with the plate surface. It was desired that a turbulent boundary layer exist on the material samples.
This was accomplished by welding three rows of 0.078-in.-diam spheres across the wedge, 3 in. from the leading edge. These spheres caused the normally laminar boundary layer to
transition to turbulent flow. An installation sketch of the spheres is also shown in Fig. 2. i
2.2 TEST ARTICLE
Four test articles were furnished by NASA/ARC, photographs of which are presented in Fig. 3. These articles, or samples, were fabricated at NASA/ARC and consisted of various combinations of Advanced Flexible Reusable Surface Insulation (AFRCI) and ceramic Reusable Surface Insulation (RSI). Shown in Fig. 4 are planform sketches of the test articles denoting the different combinations of insulation used on each sample. Using several materials on the same test sample enabled direct comparisons of the thermal response of these materials. In addition, the total wind tunnel test time required to test the various materials was reduced. Variations among the AFRS! samples were the weight of the fabric, the weave of the quilting, the felt thickness, and the edge formation. The RSI samples were
of different thicknesses and had various silicon coatings applied to their surfaces. Typical
AE DC-TR-79-62
construction characteristics for the AFRSI and RSI tiles are also shown in Fig. 4e. All
samples were bonded to l/8-in.-thick aluminum plates which in turn were attached to
Bakelite ® plates of various thicknesses to maintain a total thickness of 1.50 in.
2.3 TEST INSTRUMENTATION
2.3.1 Tunnel Conditions
Tunnel C stilling chamber pressure is measured with a 500- or 2,500-psid transducer
referenced to a near vacuum. Based on periodic comparisons with secondary standards, the
accuracy (a bandwidth which includes 95 percent of the residuals, i.e., 2~ deviation) of the
transducers is estimated to be within +_0.16 percent of pressure or +_0.5 psi, whichever is
greater, for the 500-psid range and within + 0.16 percent of pressure or + 2.0 psi, whichever
is greater, for the 2,500-psid range. Stilling chamber temperature measurements are made
with Chromel ® -Alumel ® thermocouples which have an uncertainty o f +_(I.5°F + 0.375
percent of reading in °F).
2.3.2 Test D~ita
The instrumentation in each sample consisted of thermocouples (22 in samples 1, 3, and
4; 23 in sample 2) placed at positions of interest to evaluate the thermal response. The
thermocouples were o f AWG No. 36 (0.005-in. diam) plat inum/plat inum-rhodium (13
percent) material. The locations of these thermocouples in the samples are shown in Fig. 5.
The precision of these thermocouple measurements is _+ 4 deg for temperatures between 70
and 1,200°F.
A radiometer supplied by NASA/ARC was utilized to view a 0.5-in.-diam area of the sample surface about 2.8 in. aft of the sample leading edge and on the wedge centerline. This
instrument recorded the total radiant heat flux emitted from the sample area, and its output
was recorded in millivolts. The precision of the recorded signal is estimated to be +0.015
m Y .
The VKF infrared system was used to map the sample surface temperature. The system
utilizes an AGA Thermovision ® 680 camera which scans at a rate of 16 frames per second. The camera detector is sensitive to infrared radiation in the 3- to 6-tz wavelength band.
Camera calibrations are performed with a standard blackbody reference source, have consistently been within + 1 percent of the camera manufacturer 's calibration, and are repeatable within + i percent in absolute temperature. A description of the VKF system is
A E D C-TR -79-62
given in Ref. 3. The output of the IR camera was displayed on a color TV monitor in real
time, and at selected times the monitor was photographed with a 70-mm color still camera.
Color movies (16mm) were taken of the samples intermittently during the run.
Shadowgraphs were taken after the samples reached the tunnel centerline and at selected wedge angles to record the flow-field characteristics.
Five Gardon-type heat flux gages were installed in the steel wedge ahead of the samples
(see Fig. 2b for locations). These gages had CR-AL thermocouples installed as part of the
gage, and the output of the gages provided confirmation of the boundary-layer state on the
wedge. The output of the gages was recorded at the same time the output of the sample
thermocouples was recorded. A general description of these gages is given in Ref. 2.
3.0 TEST DESCRIPTION
3.1 TEST CONDITIONS AND PROCEDURE
3.1.1 Test Conditions
The desired test conditions on the material samples were obtained by pitching the wedge
about 25 deg to the Tunnel C Mach number l0 flow and adjusting the stagnation pressure
and temperature. Pretest estimates showed that it would be necessary to set the tunnel
stagnation pressure as high as possible at the maximum tunnel stagnation temperature in
order to achieve the material temperature of 1,200°F within the 10-min exposure time. Following is a list of the tunnel stagnation conditions and the wedge local flow conditions
that existed during the test. A verification of the wedge flow conditions is presented in
Pt' Tt' P, T w, V w, Re x 10 -6 , w
M psia OR t l psia OR ft/sec ft -I W
10.14 1,200 2,150 3.3 0.083 676 4,207 0.95
Section 4.1.
A test summary showing all configurations tested and the variables for each is presented in Table 1.
3.1.2 Test Procedure
In the VKF continuous flow wind tunnels [Hypersonic Wind Tunnel (A), Supersonic
Wind Tunnel (B), and Tunnel C] the test article is mounted on a sting support mechanism in
8
A EDC-TR-79-62
an installation tank directly underneath the tunnel test section. The tank is separated from
the tunnel by a pair of fairing doors and a safety door. When closed, the fairing doors,
except for a slot for the pitch sector, cover the opening to the tank, and the safety door seals
the tunnel from the tank area. After the test article is prepared for a data run, the personnel
access door to the installation tank is closed, the tank is vented to the tunnel flow, the safety
and fairing doors are opened, the model is injected into the airstream, and the fairing doors
are closed. After the data are obtained, the test article is retracted into the tank, and the
sequence is reversed with the tank being vented to atmosphere to allow access to the test
article in preparation for the next run. The sequence is repeated for each configuration
change.
The procedure for obtaining the test measurements evolved during the progress o f the
test. Initially there was concern for the survivability of the cloth samples at wedge angles as
large as 25 deg; hence, the wedge was injected at 6 = 0 and rotated to 25 deg, while the
sample (No. 3 was used) was observed for any indication of failure; the procedure was
reversed for retraction. No indications of failure were observed. Next the sample was
injected and retracted at c$ = 25 deg and again observed for indications of failure. No
problems were encountered during injection, but on retraction the top layer of the cloth
sample was blown away (see Fig. 6a). It appears the turbulence encountered during
retraction through the tunnel wall boundary layer at such a large angle was too severe. A
possible explanation of the absence of failure during injection through the same turbulence
is that the increased fabric temperature decreased its strength prior to retraction.
Consequently, the initial procedure described above was adopted for the remainder of the
test.
The samples were exposed to the flow for 10 rain each time they were injected. The output of all the instrumentation was recorded every 0.5 sec until the wedge reached the
25-deg pitch angle; then data were recorded every 5 sec for the remainder of the run. The IR
system TV monitor~ was observed, and when the sample surface temperature reached
approximately 1,200°F a 70-ram photograph was taken. Another photograph was taken just
prior to retraction.
The samples were observed directly during exposure, and whenever any unusual
circumstances developed (fabric tears or loose tiles) the 16-mm movie camera was used to
record the events. In addition, the injection cycle of each run was recorded on 16-mm film.
After retraction, the sample was cooled by high-pressure air through the tank door nozzle and adjustable manifolds on each side. Also, the steel wedge has internal water-
cooling passages which aided in cooling the sample. Whenever the sample's aluminum
support plate cooled to 150°F, the sample was injected for another run or was replaced by
9
A EDC-TR-79-62
another sample. The nominal temperatures of the tiles at injection ranged from 70 to 140°F. Any damage to the samples was photographed using a 70-mm camera prior to continued
testing (see Fig. 6b).
Each exposure is termed a run, and all the data obtained are identified in the data tabulations by run number. The samples tested during each run are listed in Table I.
3.2 DATA REDUCTION
3.2.1 IR System Photographs of Sample Surface Temperature
The calibration of the IR system itself is detailed in Ref., 3, and the only other information required to obtain the sample surface temperature is the surface emissivity.
A representative sample of the fabric insulation was examined to determine its emissivity over the range from 3 to 6 #. The results are presented in Fig. 7. The sample total emissivity
was computed by the equation
6 (1)
t" = 6
3
where
~ =
ebZ =
X~.=
sample spectral emissivity from Fig. 7 at 530°R
blackbody spectral emissivity at 530 ° R
IR camera spectral response factor obtained from the manufacturer
Both ebX and (ebX Xx) variations with wavelength over the range of interest are presented in
Fig. 8a, and (e~) (ebX XX) variations are shown in Fig. 8b. The values of the integrals are
shown in the figures; from these the sample total emissivity was computed to be 0.62. For
this emissivity, the color calibration with temperature for the photographs of the IR system
TV monitor is listed in Table 2.
3.2.2 Sample Temperatures
Because of the expense of platinum wire, the thermocouple leads were only about 12 in.
long and terminated at a 50-pin connector inside the wedge support. Copper leads were used
10
AEDC-TR-79-62
from the other side of the connector to the instrumentation. The output of the sample thermocouples was dependent upon the connector temperature with this type of hookup;
hence, the temperature at two locations (TRI and TR2) on the connector were measured using
CR-AL thermocouple wire. The connector temperatures were measured with direct readout
instruments in °F.
The total output of each thermocouple was computed by first calculating the equivalent
platinum millivolt output of the connector thermocouple using the following equation:
EI~ = 0.42282 4 (2.66830 x 10-3) TR1
where
E R = equivalent millivolt output of a platinum thermocouple at temperature TRI
TR I = measured connector temperature in °F
The second connector temperature (TR2) was used as a redundant measurement. The equivalent millivolt output (ER) was added to the output of each platinum thermocouple to
obtain the total millivolt output of each thermocouple (ETc). The temperature for each platinum thermocouple was then computed from the equation
TC i ffi Ao+ AI(ETCi)+ A 2 ( E T C I ) 2 + . . . + AN (ETci~
where the coefficients A0 ..., AN are defined below and " i " denotes the TC number.
(3)
Range o f
ETCi, mv A0 A1 A2 A3 A4
-0.422 ~ ETC ~ 1.175 591.727 270.981 -11.8644 53.7323 -37.7430
1.175 ~ ETC ~ 5.604 605.398 234.610 -17.7323 2.18924 -0.122826
5.604 ~ ETC ~ 11.024 657.117 192.452 -3.8197 0.0687992 - - -
A 5
11.9930
11
A E D C-T R-79-62
3.2.3 Heat-Transfer Measurements
The output of the Garden-type heat gages was converted to heat flux by the equation
= (SF) (,~g) (4)
where AE is the measured gage output in millivolts and SF is the gage scale factor
determined from direct measurements of the gage output for a known radiant heat flux
input. The heat-transfer coefficient was then computed by the equation
h = ;J (5) o T t - - T
g
where T t is the tunnel total temperature and Tg is the gage temperature.
3.3 UNCERTAINTY OF MEASUREMENTS
3.3.1 General
The accuracy of the basic measurements (Pt and T0 was discussed in Section 2.3. On the basis of repeat calibrations, these errors were found to be
A P t - - = 0 . 0 0 1 6 = 0 . 1 6 p e r c e n t
P t
A T t
T t - 0 . 0 0 4 = 0 . 4 p e r c e n t
Uncertaint'ies in the tunnel free-stream parameters and the model temperatures were estimated using the Taylor series method of error propagation, Eq. (6),
(a 2 = ax,)2 ax2)= axa) 2 " " " °r ax, ) = (6)
where AF is the absolute uncertainty in the dependent parameter F = f(Xi, X2, X3...Xn) and
Xn represents the independent parameters (or basic measurements). The term AX, represents the uncertainties (errors) in the independent measurements (or variables).
12
A EDC-TR-79-62
3.3.2 Tunnel Conditions
The accuracy (based on 20 deviation) of the basic tunnel parameters, Pt and T~ (see Section 2.3) and the 2a deviation in Mach number determined from test section flow
• calibrations were used to estimate uncertainties in the other flow parameters using Eq. (6). The computed uncertainties in the tunnel free-stream and wedge flow parameters are summarized below.
Uncertalnty~ (+-) Percent of Computed Value
M M P T V Re __ wE_ wE_ w_E - w
0.8 2.5 6.3 3.5 6.3 2.9
3.3.3 Test Data
The uncertainties of the test data parameters are summarized below.
Data Type
IR Color Boundary* Temperature
Ames Radiometer Output
Sample Temperature at 1,660°R
Connector Temperature at 575°R
Gardon Gage Heat Flux, ~, Btu/ft2-sec
Gardon Gage Temperature, Tg, OR
Gardon Gage Heat Transfer Coefficient, ho, Btu/ft2-sec°R
Uncertainty,
(±) percent of actual value
1.00
0.14
0.35
0.67
5.00
0.50
6.00
* See Fig. 11 for color/temperature calibration
4.0 RESULTS AND DISCUSSION
The purpose of this report is to present a description of the test technique used to achieve the test objectives and to present some typical test results. The test technique used is described in Section 3.0; the wedge surface flow conditions (corresponding to the material sample local flow conditions) are verified and typical results are presented in this section.
13
A E DC-TR-79-62
4.1 SAMPLE TEST ENVIRONMENT
Shown in Fig. 9 is a shadowgraph of the flow over the sample surface. Several shocks
evidently are emanating from the quilted pattern in the fabric. The inclination of these
shocks is taken to be the Mach angle of the surface Mach number. From measurements of
the angles of the first and last shock that are visible in Fig. 9, the surface Mach number was
computed to be approximately 3.3. This Mach number corresponds to a wedge angle of 25.5
deg for the free-stream Mach number of 10.14. The indicated wedge angle was set to 24.5 deg; an additional degree of deflection apparently was produced by the aerodynamic loads.
From the wedge surface Mach number and tunnel stagnation conditions all the remaining surface conditions may be computed.
The computed surface flow conditions together with a finite difference procedure
outlined in Ref. 4 were used to calculate the surface heat-transfer coefficient and shear
distributions. It was assumed that transition occurred at the roughness location for the
turbulent case. The results are presented in Figs. 10a and b along with measurements from
the heat gages installed in the wedge ahead of the samples. It is seen from Fig. 10a that the
measured heat-transfer results agree well with computed values. The inferred shear values
from the heat gage measurements were computed from the equation below for a Prandtl number of one.
r = 0.117 h a V w (7)
4.2 TEST RESULTS
The sample surface temperature was monitored using the IR camera - - a picture was
taken whenever a region of the sample reached 1,200°F, and another was taken at the end of
the 10-min test period just prior to retraction. A typical picture of this type is presented in
Fig. 11. The temperatures associated with each color boundary are indicated on the picture. This temperature calibration was determined using an emissivity o f 0.62 for the fabric
samples and should be used to infer temperature for only the fabric portion of the sample surface.
To obtain the surface temperatures of the ceramic RSI tiles it would be necessary to
know the emissivity of those surfaces and adjust the IR camera temperature calibration for
the change. Shown in Fig. 12 are plots depicting the variation with emissivity of the
temperatures associated with each color number. The ceramic RSI tiles were not available
for pretest measurements of their emissivity values.
14
AEDC-TR-79-62
Typical measured sample thermocouple temperatures are presented as a function of time
in Fig. 13 for Run 23. Also presented in Fig. 13a are (I) the IR camera indicated fabric
surface temperature at approximately the center of the fabric sample (see Fig. I l) and (2) the
computed fabric surface equilibrium temperature (1,630°R). The computed value was
obtained by a one-dimensional conduction code (Ref. 5), a brief description of which is
presented in Appendix A. The IR camera results show that the fabric surface reached the
desired temperature and agrees quite well with the predicted equilibrium value. The
temperature just under the top layer o f fabric (TCI4) is about 200°F less than the surface
temperature indicated by the IR camera. This difference illustrates the necessity of having an
external measurement of the surface temperature in materials evaluation tests o f this type. It
would be difficult to install a surface thermocouple in a 0.010-in. layer of glass cloth and
obtain a true surface temperature.
The heat from the surface did not penetrate through the fabric sample until about 200 sec
after exposure. This is indicated by TCI ~, which shows the rise was only about 100°F at the end of the exposure cycle. Even then a difference of about 1,000°F was maintained between
, the exposed and interior surfaces o f the insulation over its 1-in. thickness. The temperatures
at the thermocouple locations in the ceramic RSI tiles are presented in Fig. 13b. The
thickness of these tiles was not available to allow evaluations similar to those of the fabric
sample. However, it is of interest to note that thermocouples located on the edges of the tiles
rose to higher equilibrium values than the thermocouples near the center o f the tiles. The
temperature-time data shown'in Fig. 13 are typical for Sample 2.
The performance of the samples in terms of reusability did not indicate any serious
defects. Sample 2 underwent 15 different exposures with only moderately visible "wear and
tear ." Sample 3 was damaged (see Fig. 6a and Section 3. !.2) for unrelated reasons, Sample l
showed a little fraying of one of the edges and was withdrawn from use to allow posttest
examination, and Sample 4 experienced a tear down the center of both fabric samples (see
Fig. 6b) which may have been related to handling. The preliminary analysis indicates that the
reusability of the materials is good for the test environment to which the samples were
subjected during these tests. However, a detailed analysis will be done by NASA/ARC.
$.0 CONCLUDING REMARKS
Wind tunnel tests were conducted to determine the thermal response and reusability of
AFRSI and ceramic RSI thermal protection materials. The materials were subjected to a convective heating environment which heated their surface to 1,200°F. The materials were exposed for a total of 10 min on each injection with one sample being injected 15 times. The
15
A E DC-TR-79-62
test environment was produced by a wedge at a 25-deg angle in the AEDC/VKF Mach 10
Hypersonic Wind Tunnel (C). The results of the tests may be summarized as follows:
. The materials testing technique developed at AEDC provided a clean convective
heating environment which subjected the materials samples to the required test conditions without any undesirable side effects (i. e., particle contamination) to distort the results.
. The temperature measured with a thermocouple under the top layer of fabric (0.010 in. thick) of the AFRSi material sample was 200°F less than the surface
temperature measured by the VKF IR system. This difference emphasizes the value of having an external measurement of the material surface temperature in evaluation tests of this type.
3. The temperature measurements on an AFRSI sample, which was about 1 in.
thick, indicated a 1,000°F difference between exposed and interior surfaces.
REFERENCES
1. Stallings, D. W. and Matthews, R. K. "Materials Testing in the VKF Continuous Flow Wind Tunnels." Proceedings, AIAA 9th Aerodynamics Testing Conference, Arlington, Texas, June 1976, pp. 233-237.
2. Test Facilities Handbook (Tenth Edition). "von K~rm~{n Gas Dynamics Facility, Vol. 3." Arnold Engineering Development Center, May 1974.
3. Boylan, D. E., et al. "Measurements and Mapping of Aerodynamic Heating Using a Remote Infrared Scanning Camera in Continuous Flow Wind Tunnels." AIAA Paper No. 78-799, April 1978.
4. Adams, J. C., Jr. "Implicit Finite-Difference Analysis of Compressible Laminar, Transitional, and Turbulent Boundary Layers Along the Windward Streamline of a Sharp Cone at Incidence." AEDC-TR-71-235 (AD734535), December 1971.
5. Marchand, E. O. "One Dimensional, Transient Heat Conduction in Composite Solids." M.S. Thesis, University of Tennessee, August 1974.
16
TEST SECTION-
~ INSTRUMENTATION QUARTZ WlNDOif S - - RING
SCREEN \ Tlfl~OAT SECT,ON-~ SECTI~- 7 ~S~ETY DOOR
TRANSITION 7 ~ _ F A I R ~ SECT \ WATER /
• n- : _ , _ .. !1_ I , ~ , ~ : - , , N
OPERATION Im I I n n ' i & l
u. lt F E ?
a. Tunnel assembly
A E D C - T R - 7 9 - 6 2
MODEL SUPPO~ INJECT I ON/R.ETHACTIOR SYSTEM
DIFFUSER SECTION
~-'I II I--IZlll ~_~OD~ coo[iNG~ - U ;~B-- ,,R '.INK ll"--II
H ~ : °z'''Es ~L /I TEST SECTION TANK
WINDOWS FOR MODEL INS OR PHOTOGRAPHY
WINDOWS FOR SI-LADOWGRA: SCNLIEREN PHOTOGRAPHY
NOZZLE
AIR DUCTS TO COOL MODEL FOR HEAT- TRANSFER TESTS OR QUICK MODEL CHANGE
PRESSURE TRANSDUCERS AND VALVES
TANK EIq'I'HANCE DOOR FOR MODEL INSTALLATION OR INSPECTION ~ODEL INJECTION AND
PITCH MECHANISM
b. Tunnel test section Figure 1. Tunnel C.
17
O0
m
~D &
a. Installation photograph Figure 2. Installation photograph and sketch.
~O
~ ~ \ / ~ Gage Inoperative \ ~ \ • :.- _ ~ \ / During Test \ ~. ~ , ~ \
~ / ~ ! ~ - ~ ~ Is \ Surface-- 7 1.5-~
All Dimensions in nces
b. Installation sketch Figure 2. Concluded. m
J~ -n
A EDC-TR-79-62
\
\ \ \
J
\
2~
A E D C 3 1 5 2 - 7 9
a. Sample No. 1 Figure 3. Photographs of test samples.
20
A E DC-T R -79-62
P
_4
J
b
A,E D C 3153-79
b. Sample No. 2 Figure 3. Continued.
21
A EDC-TR-79-62
A E D C 3 1 5 4 - 7 9
c. Sample No. 3 Figure 3. Continued.
22
A EDC-TR-79-62
A E D C 3155-79
d. Sample No. 4 Figure 3. Concluded.
23
A EDC-TR-79-62
AFRSI = Advanced Flexible Reusable Surface Insulation
RCG = Reaction-Cured Glass
12
12
12
AFRSI 593 Fabric Top I/2-in. Felt Taped Edges
(All Dimensions in Inches and Typical for Sample Nos. i, 3, and 4)
AFRSI 503 Fabric Top 1/2-in. Felt Taped Edges
N-18
RCG
N-17
RCG
N-12
White
RCG
N - I I
W h i t e
RCG
6
6
a. Sample No. 1 Figure 4. Details of test samples.
24
A EDC-TR-79-62
AFRSI = A d v a n c e d F l e x i b l e R e u s a b l e S u r f a c e I n s u l a t i o n RCG = Reaction-CUred Glass
VHT = Very High Temperature Paint
~-- 3 - - D - g l - - - - - 6 ---- 6
6
6
12
I I
N - 2
RCG
L-2
RCG
L-4
RCG/VHT
L-I
RCG
L-3
RCG/VHT
AFRSI 593 Fabric Top
1-in. Felt Two Taped Edges
Panels Tufted Together
1 9
N - 4
RCG/
VHT
6
6
m
N-I
RCG 6
RCG/
VHT 6
All Dimensions in Inches
b. Sample No. 2 Figure 4. Continued.
25
A EDC-TR-79-62
AFRSI = A d v a n c e d F l e x i b l e R e u s a b l e S u r f a c e I n s u l a t i o n RCG = R e a c t i o n - C u r e d G l a s s
VHT = V e r y H i g h T e m p e r a t u r e P a i n t
AFRSI 593 F a b r i c Top
1 / 2 - i n . F e l t R o l l e d E d g e s
AFRSI 503 F a b r i c Top
1 / 2 - i n . F e l t R o l l e d E d g e s
N-20
RCG/
VHT
N-19
RCG/
VHT
N-14
White
RCG
N-IS
White
RCG
See Fig. 3a 1'or Dimensions
c. Sample No. 3 Figure 4. Continued.
26
AEDC-TR-79~2
AFRSI = A d v a n c e d F l e x i b l e R e u s a b l e S u r f a c e I n s u l a t i o n RCG = R e a c t i o n - C u r e d G l a s s
VHT = V e r y H i g h T e m p e r a t u r e P a i n t
AFRSI 5 9 3 F a b r i c
1 / 2 - i n . F e l t R o l l e d E d g e s
N - 2 2
RCG/
VHT
N-21
RC6/
VHT
AFRSI N - 1 6 503 F a b r i c
White i/2-in. Felt R o l l e d Edges RCG
N-15
White
RCG
See Fig. 3a for Dimensions
d. Sample No. 4 Figure 4. Continued.
27
A EDC-TR-79-62
M a t e r i a l
, ~ ~ - ~ 0 ~ ~ n ~ " ~
~ ~ ~ , ~ ~ ~ ~ A - - F e l t
1.50 • ~ ~ ~ ~ ~ % ~_ _ ' j r n u a b r i c
"- ........................... ~ R T V - 6 0 ® Bond
~ ~ ~ ~ ~ - - Ap1 l ~ t i num Support
1 . AFRSI M a t e r i a l
Thickness I in.
0.010
V a r i a b l e
O.010 0 .010
0.125 V a r i a b l e
Typical Thermocouple Locations)
All Dimensions in Inches
II°
/Various Silicon Q --Coatings
Ceramic Material
-------q----RTV-60 ® Bond ...................................
w
,,~ ,~ ~ ,.~ ~ ,.~ ,.j --Felt Strain ,,~ ,,j ,,j ~ ~.~ ,.J ~ Isolation Pad (SIP)
. . . . . . . . . . . . . . . . . . . ~RTV-60 ® Bond ~ ~ ~ ~ ~ ~ - - ~ n u m Support
2 . C e r a m i c R S I T i l e s
e. Typical construction of AFRSI and RSI samples Figure 4, Concluded.
0 . 0 0 9
V a r i a b l e
0 . 0 1 0
Vat iable
0.010
0 . 1 2 5
V a r i a b l e
28
A EDC-TR-79-62
0
In Top Coating of RSI Tile
Top of Strain Isolation Pad
Top of Aluminum Support Plate
AFRSI Panel (Location Noted)
1/4 in. Below Top of Fabric in Felt (Typ, TC Nos. 1 5 ~
210 ~ &- - l l 0 20
Upper Radius Under Top 22
18 0
17
Lower Side of Top Fabric (Typ, TC Nos. 16, 17, 20, 22) 16
&-- 10
14
D • 7 8
9
D I 5 6
13
D • 3 4
12 At Edge of Tile (Typ,.~, D @ TC NOS. 1, 3, 5, 7) ~ 1 2
See Fig. 3a for Dimensions
Note: Thermocouple locations shown are approximate.
a. Sample Nos. 1, 3, and 4 Figure 5. Thermocouple locations in t u t samples.
29
A E DC-TR-79-62
0
21
In Top Coating of RSI Tile
Top of Strain Isolation Pad
Top of Aluminum Support Plate
AFRSI Panel (Locat ion Noted)
19 18 | • m20 08
•17 7
22
23
1% 4 9
@16
Lower Side of Top Fabr i 7
1 4 0 ~-- ii 0 I0
~---i.'4 in Below Top of Fabric in Felt
At Edge of Tile (Typ, TC Nos, 1, 3, 5, 7, 16, 17, 19, 23)
13
% ""
4 • • 3
12
See Fig. 3a for Dimensions
Note: Thormocouple locations shown are approximate.
b. Sample No. 2 Figure 5. Concluded.
30
A E D C - T R - 7 9 - 6 2
Damage C o n s i s t e d o f :
( 1 ) R i p p i n g O f f Top F a b r i c L a y e r ( 2 ) T e a r i n g Away F e l t I n s u l a t i o n ,
E x p o s i n g B o t t o m F a b r i c L a y e r
( 2 ) : :~ ~ "~*~ " -~ - ~ll~.
• . ," ~ ~'~:
" ! i i, i --: i-i~"i , .F~°*.-"-:-°": '
" : : '" : : " ~ - I ~ : i-' " : . ' - - ' , "
a. Sample 3 after Run 1 Figure 6. Photographs of damaged samples.
31
A E D C - T R - 7 9 - 6 2
Damage Consisted of:
(I) Fraying Edge (2) Ripping Off Top Fabric Layer
across Both Panels
• ~
: ~.~:;~'~"~ ~ ~.
..... ~.... . :~--.o~ .'-
b. Sample 4 after Run 18 Figure 6. Concluded.
32
A E DC-TR-79-62
1 . I I I I I I I I I I
-- Note___ss
I n c i d e n c e r a d i a t i o n s o u r c e w a s a t 5 d e g f r o m n o r m a l t o s u r f a c e .
- - T e x t u r e o f f a b r i c s u r f a c e w a s a s s u m e d t o p r e c l u d e s i g n i f i c a n t v a r i a t i o n o f e~ w i t h i n c i d e n c e a n g l e
i i I "
y_-.
I I I I I I I I I 4 5
W a v e l e n g t h ( k ) ,
Figure 7. AFRSI spectral emissivity.
I I I , 6
33
A E D C-T R-79-62
3
A
>¢
2
1
0
|
_ X~ -- IR Camera R e s p o n s e F a c t o r
/~ (e b X~) d~ = 2 . 0 9 4 X
- - ~. eb~ a t 530 O R
_ i
(ebX X x)
.- A¢~ _ V
_ ; '
-
- / \
3 4 5
W a v e l e n g t h (X), ~.
a. Blackbody emissivity Figure 8, Blackbody and AFRSI total emissivity.
34
2
,c X x X) eb X
V
_ f ~ (¢X ebX X k) dX = 1 . 2 9 0 3
¢ = 1 . 2 9 0 3 ~ 0 . 6 2 - - 2 . 0 9 4
AEDC-TR-79~2
3 4 5
W a v e l e n g t h ( k ) ,
b. AFRSI sample total emissivity Figure 8. Concluded.
35
A E D C - T R - 7 9 - 6 2
# -
, / /
, . o M w = 3.3 "
, / * sin-i i_~
. %
/
= 2 5 . 5 d e ~
= 1 0 . 1 , 1
i ¸ :~ ~ ~
?
Figure 9. Flow-field shadowgraph of Sample 2, Run 23.
36
A E DC-T R-79-62
i0.0
Sym
I Average of Measurements
Max/Min of Measurements
Theory (Ref . 4)
5 = 2 5 . 5 deg
P t ffi l j 2 0 0 p s i a
T t = 2 ,150 OR
Tw ~ 900 °R
D: 0
I O
m I
C~
m
+J
6.0
4.0
2.0
1.0 m
m
0.6--
0.4 0
6.0
4,0 --
2.0 -
T u r b u l e n t ,
I I I I I I I I i0 20 30 40
X, in.
a. He~-transfer distribution along centerline
50
t i
~ o n t
Laminar
0 I I I I I I I I 0 10 20 30 40 50
X, in.
b. Shear stress distribution along centerline Figure 10. Heat-transfer and shear stress distributions on wedge surface.
37
A E D C-T R - 7 9 - 6 2
AFRSI Sampi~
PoP'inter Which Temperature Was Selected for Fig. 13a
i 1,503 i 1,459 1 1,544
C o l o r
i i i i
1,584 I 1,6581 1,728 1,794 L 1,622 I ~ i, 762 _ _ _ _ I I
Bar Temperature Calibration (From Table 2), OR
Figure 11. I R camera photograph indicating surface temperature of Sample 2, Run 23.
38
A E D C - T R - 7 9 ~ 2
+a
u
O) o~
20
4J
®
0
.,4
e~
O
;< :3 4~
k
10
0
-I0 m
a ,
2,200
2,000
1,800
1,600
1,400
Figure 12.
-20 I I I I 0 . 4 0 0 . 4 8 O. 56 0 . 6 4 0 . 7 2 0 . 8 0
Sample Emissivity, ¢
Percent change of I R camera temperature calibration wilh sample emissivity
1,200 0.40 O. 48 O. 56 0 . 6 4 0 . 7 2 0 . 8 0
Sample E m i s s i v i t y , e
b. IR camera temperature calibration (Runs 2 through 29) with emissivity
Influence of sample emissivity on I R camera temperature calibration.
39
4~ 0
1,700
1,600
1,500
1,400
1,300
o 1,200
" 1 , 1 0 0
e 1,000
900
800
700
600
500 0
, / - -5 Changing i
~ 6 ~ 25 d e g
/ 9D--5 = 0
, ~d~ ~-Indicated ~~~------ ~ Surface
0 . . , . . . - , - " Computed S u r f a c e T e m p e r a t u r e E q u i l i b r u m T e m p e r a t u r e From IR Camera f ro m 1-D C o n d u c t i o n Code P h o t o g r a p h
( F i g . l l )
Lower S ide o f Top F a b r i c , TC14
0 . 2 5 i n . below Top of F a b r i c , TCIo
Top o f Aluminum S u p p o r t P l a t e , T C l l
I I I I I I I I00 200 300 400 500 600 700
Sample E x p o s u r c Time, t e x p , s e c
a. Temperature rise in AFRSI material Figure 13. Temperature response of Sample 2 to test environment, Run 23.
8 0 0
i l l O
J4 -n
¢0 & bJ
q~
1,700
I,600
1,500
1,400
1,300
o 1,200 g
~ 12100
1,000
9 0 0
800
700
600
500 0
~---Edge~ TCI6
I ~--TC 5
~ C e n t e r , TC 6
~-TC15
I , , .
I I I I I 100 200 300 400 500
Sample Exposure Time, texp, sec
• b. Temperature rise in RSI tiles Figure 13. Continued.
0.125 in. Below Top of Time
Pad, TC13
I I 600 700 800 m
O o
~0 tO &
4~
O
1,700
1,600
1,500
1,400
1,300
1,200 g
I,I00 k
1,000 O
900
800
700
600
500 " 0 I00 2 0 0
Edge, TCI7
C e n t e r ,
TCI8
Top o f Strain Isolation Pad, TC20
3 0 0 4 0 0 5 0 0
Sample Exposure Time, texp, sec
b. Concluded Figure 13. Concluded.
6 0 0
0.125 in. Below Top of Tile
7 0 0 8 0 0
> m o o
&
Table 1. Test Summary
J~ L o
Sample Number
Sample Position,* deg
0
0
180
0
Run
2, 3, 4
9, 10, 11, 12, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29
I
5, 6, 7, 8, 13, 14, 15, 16, 17, 18
*Sample position locates the sample on the wedge. Looking downstream from the wedge f r o n t , the zero p o s i t i o n p laces the AFRSI sample on the l e f t s~de of the wedge, and the 180-de8 sample p o s i t i o n puts the AFRSI sample on the r i g h t s i de of the wedge.
m
o
"!I
W
b~
A EDC-TR-79-62
Table 2. I R System Color/Temperature Calibration.
Temperature at Color Lower Boundary, OR Color Number Runs
Run 1 2 through 29
1
2
3
4
5
6
7
8
9
10
m
754
1,119
1,289
1,418
1,527
1,623
1,712
1,794
1,459
1,503
1,544
1,584
1,622
1,658
1,694
1,728
1,762
1,794
See Fig. 11 for color temperature callbration
44
A EDC-TR-79-62
APPENDIX A
SURFACE EQUILIBRIUM TEMPERATURE COMPUTATION
A one-dimensional conduction computer code (Ref. 5) was used to compute the fabric
sample surface equilibrium temperature considering heat input to the fabric by aerodynamic convective heating and heat losses from the fabric surface to the tunnel walls by radiation.
The sum of these heat-transfer mechanisms represents the amount of heat available to be conducted into the fabric sample. The equation for the heat available for input into the
conduction code is as follows:
~I = h o ( T t - r ~ , ) - o ~ ~ 1"4 -TI~) (A-I)
The measured heat-transfer coefficient, ho, from Fig. 10a and the computed emissivity from Fig. 8 (~ = 0.62) were used in the above equation; a is the Stefan-Boltzmann constant, Tw is
the sample surface temperature, and TR is the reference (tunnel wall) temperature (530 to 70°F) for the radiation term.
The conduction code was begun by computing the heat input for the sample initial temperature of 540°R. The conduction code then computed the temperature rise in the
fabric with this heat input for a specified time (6 sec in this case). At that time a new surface temperature was computed and used in Eq. (A-l) to compute a subsequent heat input. The
process was continued for 600 sec, which was sufficient for the equilibrium condition (q = 0) to be reached. Only the top layer of fabric was considered in this computation because
the thermal contact between all subsequent layers was not defined. The backside of the fabric was assumed to be insulated. The physical properties of the top layer used in these
calculations were as follows:
Density = 75 lbm/ft 3
Specific heat = 0.25 Btu/lbm-°R
Thermal conductivity = 8.75 x 10-~ Btu/ft-sec-°R
Thickness = 0.010 in.
The calculated equilibruim surface temperature ~'as 1,630 °R.
45
A E DC-TR-79-62
ER
ETC
AE
ebX
ho
M
P
Pt
Re
SF
T
Taw
T~
TRI, TR2
Tt
TCi
'~tex p
NOMENCLATURE
Equivalent millivolt output of a platinum thermocouple at connector temperature (TRt or TaD, my
Total millivolt output of the platinum thermocouple, mv
Millivolt output of gardon-type heat gages, mv
Blackbody spectral emissivity at 530°R
Heat-transfer coefficient [see Eq. (5)], Btu/ft2-sec-°R
Mach number
Static pressure, psia
Total pressure measured in tunnel stilling chamber, psia
Measured heat flux or computed heat input to sample surface, Btu/ft2-sec
Unit Reynolds number, ft- l
Gardon-type heat gage scale factor, Btu/ft2-sec/mv
Static temperature, °R
Adiabatic wall temperature, °R
Heat gage measured temperature, °R
Measured reference temperature at connector, °R
Total temperature measured in tunnel stilling chamber, °R
Output of thermocouple i, °R
Exposure time, sec
2
46
V
X
Xk
6
E~
O"
Velocity, ft/sec
Distance from wedge leading edge (see Fig. 4b), in.
IR camera spectral response factor
Wedge angle with respect to free stream, deg
Fabric sample total emissivity
Fabric sample spectral emissivity
Wavelength, #
Mach angle, sin-1 (l/M), deg
Stefan-Boltzmann constant, 4.761 x 10 -13, Btu/ft2-sec-(°R) 4
Computed shear stress [Eq. (7)], lbf/ft 2
SUBSCRIPTS
W
Note:
Wedge flow conditions
Unsubscripted parameters denote tunnel free-stream conditions.
A E DC -T R -79-62
47