Conclusions The first series of metallic TPS tests in the NASA-LaRC Mach 7 High Temperature Tunnel has been completed. Additional testing is 'in progress and shall provide data for off-design configurations for the metallic TPS. The available data are being analyzed and being used to correlate analytical models to be used for X-33 flight design analysis. The final paper shan present additional data from these tests and comparisons between the data and analytical predictions

Bouslog, Stanley A.

Moore, Brad

Sawyer, James Wayne

Scanlon, Ron J.

English

NASA Technical Reports Server

X-33 METALLIC TPS TESTS IN NASA-LARC HIGH TEMPERATURE TUNNEL
Stanley A. Bouslog
Brad Moore
Ron J. Scanlon
BF Goodrich Aerospace
Aerostructures Group
Chula Vista, CA
and
James Wayne Sawyer
NASA Langley Research Center
Hampton, VA
Extended Abstract for the
Thermophysics Session
AIAA 37 _ Aerospace Sciences Meeting
Jan. 11-14, 1999
Introduction
The X-33 flight vehicle is being developed by a team consisting of Lockheed Martin, NASA, BF
Goodrich Aerospace, Boeing Rocketdyne, Allied Signal, and Sverdrup. The X-33 flight vehicle
is being built and flown to demonstrate key technologies for the Reusable Launch Vehicle (RLV)
a Single Stage To Orbit (SSTO) launch vehicle. Three of the key technologies being
demonstrated on X-33 are a linear aerospike engine, composite fuel tanks, and advanced metallic
thermal protection system (TPS). In order to qualify the nominal metallic panel assembly for
flight on the X-33, a combined design analysis and test program was defmed to verify that this
assembly complies with the design requirements when exposed to flight-like environments. One
of the key tests in this program was the NASA-LaRC 8-foot High Temperature Tunnel (HTT)
test. A description of the planned tests was presented in Ref. 1. The proposed paper shall
provide a short description of this test, present data obtained during the test, and provide
comparisons with predictions.
Test Objectives
Three major test objectives were defined for the metallic honeycomb panel assembly HTT test
series. The first objective was to obtain thermal and structural data on the as-designed assembly
for correlation of analytical models while the test article is exposed to aerothermodynamic
environments comparable to those expected in X-33 flight. These analytical models are used to
verify that structure below the metallic panel TPS is maintained below specified temperature
https://ntrs.nasa.gov/search.jsp?R=19990008829 2020-06-18T00:41:51+00:00Z
limits. Thesecondobjectivewasto evaluatethedurability of thepanel-to-panelinterfaceswhile
exposedto severalcyclesof combinedhightemperature,hypersonicflow. The third objective
was to obtainthermalandstructuraldatafor hardwareoff-designcases.These cases included
vertical misaligmnents between metallic panels, missing fasteners, and damaged panel-to-panel
interface seals.
Test Facility
The 8-Foot High Temperature Tunnel (HTT) is a large, blow down wind tunnel that combusts
stored air with methane to create high enthalpy flow representative of flight conditions at 80k to
130k feet altitude. Combusted gases are expanded to approximately Mach 7 by a contoured
nozzle with an eight foot exit diameter. Total temperature of the combustor can be varied from
2400 °R to about 3600 °R with total pressures approaching 2400 psia. The nozzle extends into a
twenty-six foot diameter test chamber that houses the eight foot diameter, twelve foot long open
jet test section. A schematic of the HTT facility is shown in Figure 1.
Two banks of quartz lamps are located below the test section for radiant pre-heating of test
models prior to insertion into the flow. A typical test run of a TPS model consists of a radiant
heat exposure to bring the model up to expected temperatures prior to re-entry simulation. After
the radiant pre-heat cycle, the lamp bank is retracted and the model is rapidly inserted into the
open jet of the wind tunnel by means of an elevator system. Aerothermal exposure of the model
varies from 30 to 60 seconds depending on the test conditions selected.
Test Fixture and Test Article
The model consists of seven Inconel 617 TPS panels and is approximately 32" X 54" in size. Six
of the panels around the model perimeter are a "home plate" configuration and the center panel is
a "diamond" shaped panel. The panel geometries are representative of the flat region of the X-
33 windward surface (-_ vehicle station 250 to station 620) shown in Figure 2. The panels are
made of(2) .006" Inconel 617 face sheets that are brazed to Inconel 617 honeycomb core (3/16"
cell and.0015" foil thickness). The surfaces of the TPS panels are painted with Pyromark 2500 TM
thermal paint to achieve a high (=.85), uniform emissivity. One and one-quarter inches of 3.5
lb/_ Q-fiber felt insulation are encapsulated on the backside of each honeycomb panel with a
resistance welded .003" l.nconel 617 pan. Vents are provided in the insulation pans to
accommodate the pressure changes associated with the tunnel start up and shut down. The TPS
panels mount to rosette attachment clips made of Rene 41 alloy. The rosettes mount to a
representation of the LMSW X-33 substructure which consists of mounting beams and
attachment clips. The clips, which were provided by Lockheed-Martin Skunk Works, are
representative of the flight vehicle whereas the tank ring frames and longerons are simulations
(aluminum vs. Gr/BMI composite) modeled to provide comparable flexural rigidity. Movements
in the TPS substructure due to fuel tank displacements are not simulated in the model.
The X-33 TPS model is designed to fit in the standard model holder, also referred to as a panel
holder or sled, supplied by NASA LaRC for Thermal Protection System testing. The sled is
rectangularwith ahalf-wedgeleadingedgeanda42" x 60" x 10"cavity to accommodatethe test
modelandinstrumentation.Oneinch thick ceramicglassrocktiles arebondedto thesled surface
to serveasa thermalbarrierandblankoff unusedareasof thesledcavity.
To accommodatethe objectiveof measuringmassflow past the sealson the TPS test article, a
plenumbox was suppliedby BFG for the test. The plenum is a large,mild steelbox which fits
inside the sled cavity andis attachedwith bolts aroundtheperimeter. The plenumcontainsan
exit port on its aft endwhich connectsto amassflow meterthatis locatedin the aft cavity of the
sled.
Results
The first segment of the test has been completed and included eight radiant heat exposure cycles
in which the surface temperature was 1000 F or above and five aerothermal runs which included
a radiant pre-heat. All of these runs were made with the nominal model. Unfortunately, during
the sixth aerothermal run, the tunnel experienced cooling problems and in the shut-down process
a shock wave impacted the panel-holder sled and destroyed the test article. Presently, a new set
of metallic panels are being installed into the sled and the testing is planned to continue and be
completed within the next two months. Nevertheless, sufficient data have been obtained to meet
the first two objectives of the testing.
Radiant Heat Data
The array of radiant heat lamps positioned above the panel holder in the retracted position
provides the capability to pre-heat the test article and reduce the thermal shock as the model is
inserted into the Mach 7 flow. This capability also provides the opportunity to obtain
temperature and strain measurements during radiant heat only environments which shall be used
to correlate thermal math models and structural deflection models. The final paper shall includes
samples of these data and comparisons with predictions.
Aerothermal Data
Figure x presents temperature histories for one aerothermal run of the nominal model. These
temperatures were measured on the forward most panel in the array on the backside of the outer
and inner facesheets and on the bottom outside of the insulation pan. The different phases of the
nm can be determined from the outer facesheet temperatures as shown in Figure x. The radiant
pre-heat included a 10 F/sec ramp up rate and a dwell at a commanded temperature of 1300 F.
At the end of the dwell, the radiant heat lamps are shut off and retracted and the model is moved
vertically upwards into the flow. The data clearly show the expected trends for the thermal
response of the metallic panel assembly.
The heat transfer that occurs below and between the metallic panels has been an area of concern
for this metallic TPS. Therefore, a water-cooled heat flux calorimeter was located 4 inches
below the surface and centered in the interface between two adjacent panels. Data from this
instrument are presented in Figure x. During the radiant pre-heat phase, the calorimeter is
measuring the radiation emitted from the hot Inconel honeycomb panel edges and extensions and
thesidesoflnconel insulation pans. These data assist in correlating radiation heat transfer
models for prediction of the heat transfer to internal hardware located below the TPS assembly.
When the model is inserted into the flow, a small increase in the calorimeter measurement is
observed. These data shall be used to correlate the interface leakage convective heat transfer
models.
Conclusions
The first series of metallic TPS tests in the NASA-LaRC Mach 7 High Temperature Tunnel has
been completed. Additional testing is in progress and shall provide data for off-design
configurations for the metallic TPS. The available data are being analyzed and being used to
correlate analytical models to be used for X-33 flight design analysis. The final paper shah
present additional data from these tests and comparisons between the data and analytical
predictions.
Acknowlegements
Support for this effort is being provided by NASA through Cooperative Agreement NCC8-115.
References
1. Sawyer, J. W., Hodge, J, and Moore, B., "Aerothermal Test of Metallic TPS for X-33
Reusable Launch Vehicle," 3 'd European Workshop on Thermal Protection Systems, March
25-27, 1998.
2. Deveikis, W. D. and Hunt, L. R., "Loading and Heating of a Large Flat Plate at Mach 7 in the
Langley 8-foot High-Temperature Structures Tunnel," NASA TN D-7275, Sept. 1973.
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Figure 1 - NASA Langley Reseach Center High Temperature Tunnel.
Figure 2 - Sketch of Panel-Holder Sled with Metallic TPS Assembly.
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X-33 Metallic TPS Tests in NASA-LaRC High Temperature Tunnel

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