February 2011 

NASA/TM–2011-217065 

Results From a Pressure Sensitive Paint Test 

Conducted at the National Transonic Facility on 

Test 197: The Common Research Model 

 

A. Neal Watkins, William E. Lipford, and Bradley D. Leighty 

NASA Langley Research Center, Hampton, Virginia 

Kyle Z. Goodman 

ATK, Hampton, Virginia 

William K. Goad and Linda R. Goad 

Jacobs Sverdrup, Hampton, Virginia 
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February 2011 

NASA/TM–2011-217065 

Results From a Pressure Sensitive Paint Test 

Conducted at the National Transonic Facility on 

Test 197: The Common Research Model 

 

A. Neal Watkins, William E. Lipford, and Bradley D. Leighty 

NASA Langley Research Center, Hampton, Virginia 

Kyle Z. Goodman 

ATK, Hampton, Virginia 

William K. Goad and Linda R. Goad 

Jacobs Sverdrup, Hampton, Virginia 
Available from: 

NASA Center for AeroSpace Information 

7115 Standard Drive 

Hanover, MD 21076-1320 

443-757-5802 
 Results From a Pressure Sensitive Paint Test 

Conducted at the National Transonic Facility on 

 Test 197: The Common Research Model 

 

 A. Neal Watkins, William E. Lipford, and Bradley D. Leighty 

 NASA Langley Research Center, Hampton, Virginia 

 

 Kyle Z. Goodman 

 ATK, Hampton, Virginia 

 William K. Goad and Linda R. Goad 

 Jacobs Sverdrup, Hampton, Virginia 

Abstract 

This report will serve to present results of a test of the pressure 

sensitive paint (PSP) techniqueon the Common Research Model (CRM). 

This test was conducted at the National Transonic Facility (NTF) at 

NASA Langley Research Center. PSP data was collected on several 

surfaces with th etunnel operating in both cryogenic mode and standard 

air mode. This report will also outline lessons learned from the test as 

well as possible approaches to challenges faced in the test that can be 

applied to later entries. 

Introduction 

The accurate determination of spatially continuous pressure and temperature distributions on 

aerodynamic surfaces is critical for the understanding of complex flow mechanisms and for the 

comparison with computational fluid dynamics (CFD) predictions. Conventional pressure measurements 

are based on pressure taps and electronically scanned pressure transducers. While these approaches 

provide accurate pressure information, pressure taps are limited to providing data at discrete points. 

Moreover, the integration of a sufficient number of pressure taps on a surface can be time and labor 

intensive and add significant expense to the model. 

Using pressure sensitive paint (PSP) allows for the accurate determination of pressure distributions 

over an aerodynamic surface and is based on an emitted optical signal from a luminescent coating. As 

originally developed,1-3 this technique was primarily useful for mean pressure measurements at transonic 

and higher flows, but has since been adapted to lower speed flows4-6 as well as measurements of 

fluctuating pressures.7,8 A number of review articles cover the topic in detail.9-11 PSP measurements 

exploit the oxygen (O2) sensitivity of luminescent probe molecules suspended in gas-permeable binder 
 6

materials. In wind tunnel applications, the PSP is applied to the model by conventional paint spraying 

techniques. Light sources such as UV LED arrays are mounted external to the test section to illuminate 

the painted model and effect luminescence emission from the entrapped oxygen-sensitive molecules. For 

the majority of pressure paints, PSP emission occurs in the red or orange region of the visible spectrum 

(~580 - 650 nm). The intensity is inversely proportional to the amount of oxygen present such that 

brighter regions in the paint emission indicate lower concentration of oxygen (and thus lower pressure) 

relative to the darker regions. Scientific-grade CCD cameras with spectral band-pass filters to 

discriminate between the excitation (blue) and emission (orange) signals, capture the intensity image of 

the PSP-coated model surface, providing a means to recover global surface pressure distributions on test 

articles of interest. PSP measurement systems all employ a ratio of image pairs to compensate for 

intensity non-uniformity due to sources other than oxygen concentration, the most significant of which 

are paint application and illumination heterogeneity. In the conventional approach, PSP images acquired 

either prior to or immediately following tunnel operation (wind-off) are ratioed with images acquired at 

each tunnel condition (wind-on). A companion technique, temperature sensitive paint (TSP), uses probe 

molecules whose brightness varies with temperature, but which are insensitive to oxygen concentration. 

If the test surface under study is immersed in an atmosphere containing O2 (e.g. air), the recovered 

luminescence intensity can be described by the Stern-Volmer relationship12 

I0/I = 1 + KSV(T)PO2 (1) 

where I0 is the luminescence intensity in the absence of O2 (i.e. vacuum), I is the luminescnec intensity at 

some partial pressure of oxygen PO2, and KSV is the Stern-Volmer rate constant. The value of KSV

depends on the properties of both the luminescent molecules and the binder, and is generally temperature 

dependent. Since it is a practical impossibility to measure I0 in a wind tunnel application, a modified 

form of the Stern-Volmer equation is typically used. This form replaces the vacuum calibration (I0) with 

a reference standard 

IREF/I = A(T) + B(T)P/PREF (2) 

where IREF is the recovered luminescence intensity at a reference pressure, PREF. A and B are temperature 

dependent constants for a given PSP formulaiton and are ususally determined a priori using laboratory 

calibration procedures. The calibration and interpretation of TSP data follows a similar procedure, using 

the TSP luminescence intensity recovered at a reference temperature. 

PSP measurements are difficult to make under cryogenic conditions for two reasons. First, the test gas 

is typically nitrogen, refrigerant, or some other medium that usually contains little or no oxygen. Second, 

the diffusion of oxygen into the paint binder is highly temperature dependent, and at low temperatures, is 

practically nonexistent. As such, it is not surprising that initial cryogenic testing with luminescent paints 

used TSP.13 Indeed; probe molecules can be found which respond strongly to temperature even under 

cryogenic conditions. 

For PSP, researchers developed two distinct methods to overcome the challenges caused by the low 

diffusion of oxygen into the paint binder. Initial cryogenic PSP tests were conducted using anodized 

aluminum.14 In these tests, the model was constructed from aluminum and anodized to coat the surface 

with a monolayer of aluminum oxide. Then the model was coated with an oxygen luminophore that 

chemically bonds with the aluminum oxide. This produces a coating that is essentially a few molecules 

thick, thus alleviating the issues with paint binders and oxygen diffusion. The disadvantages to this 
 7

technique are that the anodizing requirement makes it difficult to use with large and complex models, and 

it cannot be used with the stainless steel models that are typically employed in large-scale cryogenic 

testing. For this testing, a PSP formulation consisting of a binder that has a very large diffusion rate and 

can be applied with standard airbrush techniques and capable of adhering to many different types of 

surfaces was developed.15,16 These formulations have been used successfully at the NASA Langley 0.3-

Meter Transonic Cryogenic Tunnel15 as well as other facilities.16 A variation of the PSP technique has 

been performed at the NTF with this formulation to visualize surface flow patterns on a blended wing 

body model,17 and preliminary testing of cryogenic PSP at the European Transonic Windtunnel has also 

been reported.18 Recently, a full cryogenic PSP test has also been reported at the NTF on a traditional 

commercial transport wing.19

Experimental 

Paint Formulations 

Two separate PSP formulations were used for this test depending on the operating conditions of the 

tunnel. In both formulations, the oxygen sensitive luminphore platinum mesotetra(pentafluorophenyl)porphine, or Pt(TfPP), was dissolved in an appropriate oxygen-permeable binder. 

In the cryogenic testing phase, this binder was polytrimethylsilylpropine, PTMSP,15,16,20 chosen because it 

is a glassy polymer with a large free volume, enabling it to have a high oxygen diffusion rate. This leads 

to high oxygen permeability even at cryogenic conditions. For the air mode operation of the tunnel, the 

binder is made from a co-polymer of trifluoroethylmethacrylate and isobutylmethacrylate (FEM).21

 

Paint Calibration 

All paint calibrations were performed separate from the wind tunnel in a laboratory calibration 

chamber. The chamber cell, shown in Figure 1, consists of a brass block (A). Temperature control of 

the block is accomplished by flowing liquid nitrogen into the block through milled channels internal to 

A

B

C

E D

Figure 1. Calibration chamber for cryogenic PSP and TSP formulations. The left picture depicts the 

interior of the chamber including the brass block (A), the inlet and outlet for liquid nitrogen flow 

(B), the resistive heaters (C), the thermocouple for temperature monitoring and control (D), and an 

unpainted coupon (E). The right picture shows the complete calibration chamber with a coupon and 

the external shutter open. 
 8

the block (B) and heat is applied via resistive heaters (C) imbedded in the block. A thermocouple (D) is 

also imbedded into the block, which serves as the sensor input to a proportional-integral-derivative (PID) 

controller capable of regulating both the amount of liquid nitrogen flowing to the cell (via a hardened 

solenoid valve) and the amount of heat applied. A painted coupon (E) is bolted to the front of the block 

and thermal contact is ensured using a silicon-free thermal compound. Pressure is controlled by sealing 

the block in a chamber equipped with a quartz window. An external shutter is affixed to the window to 

reduce photodegradation of the paint. The chamber is also placed inside a dark enclosure to minimize 

background illumination. The cell is capable of operating from vacuum to room atmosphere and to 

temperatures as low as -196 oC (-321 oF, boiling point of liquid nitrogen) to ~ 100 oC (212 oF). 

Illumination of the painted coupon is achieved using a 400 nm LED array and luminescent images are 

acquired using a CCD camera equipped with a band-pass filter to block excitation light. For cryogenic 

PSP calibration, oxygen-nitrogen gas mixtures were used to mimic the expected condition in the test 

section. For air mode operation, dried air was used as the calibration gas. A typical PSP response at 

cryogenic conditions to increasing pressure of a 3000 ppm oxygen-nitrogen mix is shown in the left of 

Figure 2 and a typical PSP response for air is shown in the right of Figure 2. 

Facility 

The NTF is one of the world’s leading facilities for providing high quality flight Reynolds number 

aeronautical data and has been operational since 1982. The tunnel has a test section of 2.5 m x 2.5 m (8.2 

ft x 8.2 ft) and is capable of operating at speeds from subsonic (M = 0.1) to transonic (M = 1.1) with 

Reynolds numbers from 13.1 x 106/m (4 x 106/ft) to 476 x 106/m (145 x106/ft) at transonic Mach numbers. 

The tunnel is capable of operating in either air mode at elevated pressure and temperature or at cryogenic 

conditions (to -156 oC or -249 oF) by injecting liquid nitrogen into the tunnel circuit. In the cryogenic 

operating mode, the NTF is capable of providing full-scale flight Reynolds numbers without an increase 

in model size. Several optical diagnostic techniques are available in the NTF, including Video Fluorescent 

Minituft Flow Visualization, Sharp Focusing Schlieren Flow Visualization, Video Model Deformation, 

and a newly designed and installed PSP/TSP system. 

For the cryogenic portion of the test, air injection was accomplished using a valve to regulate the 

amount of dry air (dew point < -60 oC) introduced into the tunnel. Numerical studies of the flow at the 

Figure 2. Typical calibration curves for PSP under cryogenic conditions (left) and standard air 

conditions (right).
 9

NTF estimated that approximately 0.9 kg/s dry air would be required to achieve an oxygen concentration 

of 1000 ppm in the flow at a tunnel temperature of -156 oC (-249 oF) and pressure of 275 kPa (40 psi). 

Little if any tunnel heating effects were observed using these magnitude flow rates, as determined by the 

negligible temperature changes noted in the flow. This could be expected as liquid nitrogen is introduced 

to the flow under these conditions at approximately 130 kg/s. Oxygen monitors (described below) were 

interfaced into the tunnel and monitored to determine when and how much air would be introduced. 

Model 

The model is a full-span 0.027 scale model incorporating a wing design based on an open geometry. 

The overall design of the model is a joint effort between NASA and several other partners to provide a 

common platform that can be tested in a variety of facilities using a plethora of techniques. The entire 

model has a finish of approximately 0.2 μm and is mainly composed of stainless steel. 

Previous cryogenic PSP15 and TSP22

 tests have shown that highly polished stainless steel models must 

first be painted with a basecoat before the PSP will adhere to the model. For this test, SpectraPrime 

(Sherwin Williams) was chosen as the basecoat. Previous tests have shown this paint to be very robust to 

cryogenic conditions. After curing, the basecoat layer was sanded with 1500-2000 grit paper, which was 

needed to promote adhesion of the PSP layer. Finally, the PTMSP PSP was applied to the model. The 

PTMSP PSP could be easily removed by wiping with toluene, allowing for either a re-coating of the 

cryogenic PSP or re-using the basecoat for the air mode PSP (FEM). However, removal of the FEM PSP 

cannot be accomplished in such a way that will leave the basecoat intact. 

Instrumentation 

Illumination: Illumination was achieved using several custom designed LED-based arrays capable of 

operating at either room temperature (for NTF air model operation) or at cryogenic conditions. The 

arrays consisted of 80 individual LED elements arranged on a 12.7 cm diameter 4.5 mm thick aluminum 

substrate. The aluminum substrate is also equipped with an RTD sensor to monitor temperature as well 

as resistive heaters on the back for cryogenic operation. The LED arrays are operated using a 1kW 

switching power supply and can be remotely operated using standard TTL (transistor-transistor logic) 

pulses. The LED array produces light centered at 400 nm (~20 nm full width at half maximum) at greater 

than 80 W under nominal forward current conditions. This can also be manually adjusted as needed by 

controlling the current applied to each array. 

Image Acquisition: Images were acquired from cameras placed directly over and under the model. 

The cameras employed were thermoelectrically-cooled monochrome interline transfer CCD cameras 

employing 11 Mpixels (4000 x 2672) capable of acquiring images at up to 5 fps at full resolution. The 

cameras employ an electronic shutter alleviating various frame transfer issues that were seen previously 

when cameras using mechanical shutters were used. This allows for operation where the LED 

illuminators are on constantly, alleviating some electrical and timing issues seen previously. The cameras 

employ 12-bit digital resolution and were interfaced to the computer using custom designed armored fiber 

optic cables capable of operating at cryogenic temperatures. 

Oxygen monitoring: To facilitate calibration of the paint, the oxygen concentration in the flow must 

be measured accurately. This was done by interfacing an oxygen monitoring system into the tunnel 

control loop. Two oxygen monitors were attached to outlets of pressure ports, one from a static port in 
 10 

the floor and one from a dynamic port in a small pressure rake. Both were mounted approximately 4.5 m 

forward of the model. The oxygen sensor system employed a zirconium oxide sensor with a time 

response of less than 10 s. The system was also equipped with an in situ calibration option allowing it to 

maintain linearity and repeatability of less than 2% or reading or 0.5 ppm O2 absolute. The unit is 

controlled by a personal computer via RS-232 protocol. 

Data Acquisition 

For cryogenic operation of the tunnel, data acquisition was performed using a modification of the 

typical procedure described above. Introduction of dry air into the tunnel was first performed using a 

valve and the oxygen concentration was monitored until it stabilized. Then wind-off images were 

acquired at various angles of attack (from 0 to 4 degrees) with a wind speed of ~Mach 0.09 (to ensure 

adequate circulation of the oxygen). It is realized that this causes as much as 1% error in the pressure 

measurements. After the initial set of wind-off images were acquired, wind-on images were acquired at 

the same angles of attack and at various speeds (Mach 0.7, 0.85, and 0.87). The oxygen concentration 

was continuously monitored and when it began to decrease significantly, more air was introduced to reestablish the baseline value. Wind-off images also were acquired immediately following the last wind-on 

image. For air mode operation of the tunnel, the standard wind-off/wind-on technique was employed as 

described in the section above. 

Results and Discussion 

Cryogenic PSP Results 

The basecoat for all of the PSP experiments was applied while the model was installed in the test 

section. This allowed for the pressure ports to be purged with air, as well as prevented excessive handling 

of the model that would have occurred if it had to be installed after painting. This first cryogenic PSP 

coating was then applied in the test section and then the tunnel was purged with nitrogen and prepared for 

cryogenic operation. After sufficient cooling and treatment, the PSP data was collected and showed 

unexpected results, including what can only be described as turbulent wedges, as seen in left of Figure 3. 

These wedges are reminiscent of the turbulent wedges that can be seen in some TSP experiments. 

However, the image shown in Figure 3 is that of a reference image (pseudo wind-off image taken at Mach 

~0.09), which should have little if any temperature effects due to flow. Some sort of irreversible change 

occurred in the cryogenic PSP that has caused this pattern to occur, which unfortunately overwhelmed 

any pressure sensitivity of the paint. This necessitated re-painting the model, which was accomplished by 

simply removing the top layer of PSP using toluene and reapplying a new active layer. 

The second layer was applied by inserting the access housing into the tunnel, thus alleviating the need 

to purge and cool the majority of the tunnel circuit. Thus, the second coating could be tested shortly after 

completion (requiring only the tunnel temperature to be re-established at ~-150 oC. This coating still 

showed some of the wedge effect, evident near the leading edge (see the right image of Figure 3). Still, 

an in situ calibration was performed on the PSP using a selection of pressure taps that were visible on the 

upper portion of the port wing. Specifically, taps from rows “C”, “D”, “F”, and “H” (according to the 

mechanical drawings on the wing) were employed as the larger pressure gradients should be present in 

these areas. A complete angle of attack sweep at Mach = 0.85 (run 124) is shown in Figure 4, along with 

the comparison with the taps in row “G” (not used for calibration). Unfortunately, the PSP data shows 

some very large noise characteristics and cannot quite follow the tap readings at the leading or trailing 
 11

edge (which could be due to the wedge effect seen in Figure 3, as well as increasing oblique angle due to 

curvature , especially a the leading edge). However, even with these issues, the PSP measurements are 

within 30% error compared with the pressure taps. Solving some of these issues should reduce this error 

to within 10% or less agreement with the taps. Several improvement strategies for the cryogenic PSP will 

be presented in a future section. Also, it should be noted that all of the data has been analyzed, but only 

the sample data was provided for brevity. 

Air Mode PSP 

After the cryogenic testing, the tunnel was warmed to ambient conditions and the cryogenic PSP layer 

was removed with toluene. After drying, the FEM PSP was applied and allowed to dry for a couple of 

hours while the tunnel was prepared for operation. For these runs, the exact same angles of attacks and 

speeds were employed as for the cryogenic runs. Using air mode and elevated temperatures and pressures 

allowed testing at a Reynolds numbers of approximately 26 x 106/m (8 x 106/ft) as opposed to the 

cryogenic testing, which used a free stream Reynolds number of approximately 105 x 106/m (32 x 106/ft). 

However, even with these differences, the qualitative behavior of the wing should be expected to be 

similar across the two regimes. 

Even with the elevated temperatures and pressures employed in air mode, the PSP retains much of its 

sensitivity. However, the luminescence signal of the paint is significantly quenched, requiring exposure 

times about ten times larger than that needed for the cryogenic testing. Thus, only two images were able 

to be acquired during a point as opposed to ten images in the cryogenic testing. Moreover, calibration of 

the images was accomplished using the same procedure (and same taps) as in the cryogenic mode of 

operation. These results (as well as tap comparisons to row “G”) are shown in Figure 5. The run at Mach 

= 0.85 (Run 138) was chosen for comparison with the cryogenic data. The PSP data looks much cleaner 

in this mode of operation, though the wear on the basecoat is beginning to be seen as certain physical 

features of the model are easily seen (most notably, the body filler used in certain portion of the wing). 

Similar to the cryogenic PSP testing, the PSP cannot quite follow the pressure taps at the leading edge, 

Figure 3. Cryogenic wind-off images showing “wedges” which are permanently imposed in the paint. 

The left image is from run 119 (the first cryogenic PSP application) and the right image is from run 

126 (the second cryogenic PSP application).
 12

but this is most likely due to the oblique angle between the camera and the surface at the leading edge. If 

these taps are removed from the fit, then the PSP data agrees well within 5% of the pressure tap values. 

Figure 4. PSP results from run 124 with corresponding pressure tap comparison. Conditions 

are M = 0.85, T = -156 oC (-249 oF), P = 124 kPa (18 psi), Re = 105 x 106/m (32 x 106/ft).
 13

Proposed Improvements/Lessons Learned 

While this test was used to build upon the previous test and used several improvements that were 

Figure 5. PSP results from run 138 with corresponding pressure tap comparisons. Conditions are 

M = 0.85, T = 50 oC (122 oF), P = 124 kPa (18 psi), Re = 26 x 106/m (8 x 106/ft).
14

identified, additional improvements in the process, paint, and instrumentation need to be investigated to 

ensure the technique PSP technique is effective at cryogenic conditions. The data in air mode seems to 

agree quite well with the pressure tap values, and the sensitivity of the paint is also quite sufficient for 

testing in this regime. This should be expected because of the legacy of PSP measurements in this 

pressure and temperature regime. 

Improvements in the process entail mostly application of the cryogenic PSP. The cryogenic PSP 

formulation is notorious for being highly application dependent, and is not sprayed in the traditional 

manner. Most paint formulations are sprayed to give an even, almost “wet” coating to ensure a good 

application. However, the cryogenic PSP formulation requires a dry-type of spray; the PTMSP needs to 

be applied so that the majority of the solvent evaporates before the polymer impact the surface. This 

causes the PTMSP to be applied as island-like structures that ensure that the porous nature of the polymer 

remains intact. However, if the PTMSP is not sprayed dry, then the polymer tends to coalesce and form a 

continuous layer that has similar oxygen permeability as the FEM. Thus, the oxygen sensitivity at 

cryogenic temperatures is lost as the barrier to oxygen diffusion becomes too great. Additionally, the 

basecoat applied to the model (SpectraPrime) does have an influence as well, and there were portions of 

the model that had a thinner basecoat than others. This could lead to issues with spraying and with 

general interactions of the PTMSP and the SpectraPrime. While it is relatively simple to apply this to test 

coupons, great care must be taken in applying this formulation to larger areas on the model. The only real 

solution to this is practice by the appropriate personnel. This practice would just be in the spraying 

technique, and does not require a full wind tunnel test; large sheets of aluminum flashing could be painted 

and portions of the aluminum calibrated to provide a measure of the sensitivity across large areas. 

For the cryogenic PSP formulation itself, a better grasp of the curing requirements needs to be 

ascertained as well as any effects of water (ice) contamination on the paint itself. One theory of the 

wedge formation that appeared in the first cryogenic application was due to contamination from the 

tunnel itself. Unfortunately, none of the traditional “frost” detection methods (other than manual 

surveillance) were employed during the cool down of the tunnel. However, during the second application 

of the cryogenic PSP, the access housing was used to allow entry into the section, thus keeping the 

majority of the tunnel under a nitrogen atmosphere. This would greatly reduce the amount of possible 

moisture contamination from air, and there was a correspondingly lesser amount of wedges that were 

observed. For this run, the PSP was illuminated, and images acquired during the tunnel cool down phase. 

The wedges were noticed almost immediately after initiation of the fan for purging, though they did 

eventually fade away. An alternative theory to the wedge formation is that the PSP itself was not cured 

completely, and that when flow was introduced during the purge cycle, the turbulence caused an uneven 

curing of the paint. Traditionally, the cryogenic PSP formulation has cured very quickly (within ten 

minutes), and this is in the published procedure. However, to test this, laboratory experiments looking at 

different curing times have been developed and are currently being carried out. These experiments will 

employ larger areas of aluminum flashing as coupons and samples will be taken and calibrated at varying 

times after spraying. Other experiments will be devised based on these results. 

Throughout the test, several instrument failures occurred, some being terminal while others being 

temporary. The LED wafers used for illumination gradually decreased in functionality throughout the test 

(especially the cryogenic portion) and could have caused some of the overall challenges (though it is 

difficult to say as there is no independent method of measuring illumination on the model). This is most 

likely due to the method of construction of the circuit boards of the wafers. A new procedure for 

mounting these into the tunnel has been suggested which should alleviate this failure. Additional failures 

occurred in the cameras themselves. The cameras employ a coverslip of very thin glass over the CCD 

sensor. This coverslip fractured in one camera and cracked in another camera during the pressure cycles 
15

of the tunnel itself. This could be alleviated by simply removing the coverslip entirely. While the 

presence of the coverslip is to prevent condensation on the sensor during thermoelectric operation, the 

cameras are only operated in a dry environment (dew point < -60 oC), and the thermoelectric cooler 

cannot approach the dew point to allow condensation to occur. Another alternative would be to design 

and build environmental chambers that could be pressure sealed, though the optical access in the tunnel 

could preclude this option. 

Conclusions 

This report has presented representative PSP data acquired at both cryogenic and standard air mode 

conditions in the National Transonic Facility. Several issues occurred during the cryogenic portion of the 

test that resulted in the PSP only able to agree with pressure tap readings to ~30%. In addition, several 

anomalies in the paint itself were noticed, with the biggest impact being the presence of permanent 

“wedges” that appeared in paint itself during the purge and cool down cycles. This required a re-paint of 

the model, which still displayed some of the wedges, though not to the large extent as the first application. 

Work is currently underway to try and ascertain the origin of the wedges, with the initial focus being on 

possible contamination from the tunnel circuit or an uncured paint application. 

The PSP performed admirably in the air mode phase of the test, in which data was collected at slightly 

elevated temperatures and pressures. This should be expected, and was borne out with the PSP reading 

agreeing with pressure tap readings to easily within 5%. For both of these portions of the test, all of the 

data has been analyzed to near completion (resectioning of the data on the surface will need to be 

completed after an appropriate surface grid is supplied), and is available upon request. Only a portion 

was presented here for brevity. 

Finally, some of lessons learned and possible improvements for future testing were presented. This 

will focus on general application techniques, improving and fully understanding the nature of the 

cryogenic paint, and making general improvements and repairs to the equipment will be emphasized. 

References 

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January 14-17, 2002. 
REPORT DOCUMENTATION PAGE Form Approved

OMB No. 0704-0188

2. REPORT TYPE 

Technical Memorandum

 4. TITLE AND SUBTITLE

Results From a Pressure Sensitive Paint Test Conducted at the National 

Transonic Facility on Test 197: The Common Research Model 

5a. CONTRACT NUMBER

 6. AUTHOR(S)

Watkins, Anthony N.; Lipford, William E.; Leighty, Bradley D.; Goodman, 

Kyle Z.; Goad, William K.; Goad, Linda R.

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NASA Langley Research Center

Hampton, VA 23681-2199

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National Aeronautics and Space Administration

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14. ABSTRACT

This report will serve to present results of a test of the pressure sensitive paint (PSP) technique on the Common Research 

Model (CRM). This test was conducted at the National Transonic Facility (NTF) at NASA Langley Research Center. PSP data 

was collected on several surfaces with the tunnel operating in both cryogenic mode and standard air mode. This report will 

also outline lessons learned from the test as well as possible approaches to challenges faced in the test that can be applied to 

later entries.

15. SUBJECT TERMS

Cryogenic Testing; National Transonic Facility; Optical Diagnostics; Pressure Sensitive Paint

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