Fabrication and Testing of a Leading-Edge-Shaped Heat Pipe

8/3/2019 Fabrication and Testing of a Leading-Edge-Shaped Heat Pipe

http://slidepdf.com/reader/full/fabrication-and-testing-of-a-leading-edge-shaped-heat-pipe 1/20

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Available from:

NASA Center for AeroSpace Information (CASI) National Technical Information Service (NTIS)

7121 Standard Drive 5285 Port Royal Road

Hanover, MD 21076-1320 Springfield, VA 22161-2171

(301) 621-0390 (703) 605-6000

Available electronically at the following URL address: http://techreports.larc.nasa.gov/ltrs

The use of trademarks or names of manufacturers in this report is for accurate reporting anddoes not constitute an official endorsement, either expressed or implied, of such products ormanufacturers by the National Aeronautics and Space Administration or by AnalyticalServices & Materials, Inc.



* Phone: (757) 864-5423, e-mail: [email protected]

Fabrication and Testing of a

Leading-Edge-Shaped Heat Pipe

David E. Glass*

Analytical Services & Materials, Inc., Hampton, VA 23666

Michael A. Merrigan, J. Tom Sena, and Robert S. Reid

Los Alamos National Laboratory, Los Alamos, NM 87545

Abstract

A leading-edge-shaped heat pipe was successfully fabricated and tested. The heat

pipe had a D-shaped cross section and was fabricated from arc cast molybdenum-

rhenium. An artery was included in the wick. Several issues were resolved during thefabrication of the heat-pipe container and wick with a sharp-leading-edge radius. The

heat pipe was tested in a vacuum chamber using induction heating and was started up

from the frozen state several times. The heat pipe did operate as a heat pipe over a

portion of its length. However, design temperatures and heat fluxes were not obtained

due to premature failure of the heat pipe resulting from electrical discharge between theinduction heating apparatus and the heat pipe.

Introduction

Stagnation regions, such as wing and tail leading edges and nose caps, are criticaldesign areas of hypersonic aerospace vehicles because of the hostile thermal environment

those regions experience during flight. As a hypersonic vehicle travels through the

earth's atmosphere, the high local heating and aerodynamic forces cause very high

temperatures, severe thermal gradients, and high stresses. Analytical studies andlaboratory and wind tunnel tests indicate that a solution to the thermal-structural

problems associated with stagnation regions of hypersonic aerospace vehicles might beobtained by the use of heat pipes to cool these regions.

In the early 1970's, several feasibility studies were performed to assess theapplication of heat pipes for cooling leading edges and nose caps of hypersonic vehicles.1-

5 NASA Langley Research Center (LaRC), through a contractual study, analytically

verified the viability of heat pipes for cooling stagnation regions of hypersonic vehicles.1

In 1972, McDonnell Douglas Astronautics Co. (MDAC) compared four space shuttle



2

wing leading-edge concepts: a passive carbon-carbon concept, a passive coated-columbium concept, an ablative concept, and a liquid-metal/superalloy heat-pipe-cooled

concept.2 The heat-pipe-cooled concept was determined to be a feasible and durable

design concept, but was slightly heavier than the other candidate concepts. In 1973,

MDAC fabricated a half-scale shuttle-type heat-pipe-cooled leading edge to verify

feasibility of the concept.4

This model was tested by a series of radiant heat andaerothermal tests at NASA LaRC from 1977 to 1978 to verify heat-pipe transient, startup,

and steady-state performance.6-8 In 1979, MDAC received a follow-on contract to

optimize a heat-pipe-cooled wing leading edge for a single-stage-to-orbit vehicle.Results of the follow-on study indicated that the mass of a shuttle-type heat-pipe-cooled

leading edge could be reduced by over 40 % by use of a more efficient structural design.9

In 1986 MDAC received a contract to design and fabricate a sodium/superalloy heat-

pipe-cooled leading edge component for an advanced shuttle-type vehicle. 10 Thisadvanced shuttle-type heat pipe was 6-ft long and was tested at MDAC by radiant heating

and at Los Alamos National Laboratory (LANL) by induction heating.11-12

A Haynes 25/sodium leading-edge-shaped heat pipe with a D-shaped crosssection was designed and tested by Boeing Advanced Systems.13 The heat pipe had alength of 11.8 in., and a wall thickness of 0.030 in. Thermal performance, vibration

sensitivity, and critical heat flux tests were conducted. Straight niobium/lithium heat

pipes with a D-shaped cross section and a 0.024 in. thick wall have also been fabricated

and tested.14-15 These heat pipes had an oxidation resistance coating on the outer surface.Each of the heat pipes in references 13-15 utilized a sintered metal wick.

Preliminary design studies at NASA LaRC indicate that a refractory-

composite/refractory-metal heat-pipe-cooled leading edge can reduce the leading-edgemass by over 50% compared to an actively cooled leading edge, can completely eliminate

the need for active cooling, and has the potential to provide failsafe and redundant

features.16 Recent work to develop this novel refractory-composite/refractory-metal heat-

pipe-cooled leading edge for hypersonic vehicles combines advanced high-temperaturematerials, coatings, and fabrication techniques with an innovative thermal-structural

design. Testing of a component at NASA LaRC with three straight molybdenum-

rhenium (Mo-Re) heat pipes embedded in carbon/carbon (C/C) has demonstrated the

feasibility of operating heat pipes embedded in C/C.17-18 In those tests, the heat pipeswere tested with quartz lamps up to temperatures around 2200°F. Some of key concepts

utilized in the fabrication of the refractory composite heat-pipe-cooled leading edge, such

as a compliant or removable layer to reduce thermal stresses and a slightly convex

surface to maintain good thermal contact, have been patented.19

The present paper discusses the next step in the development of a refractory-

composite/refractory-metal heat-pipe-cooled leading edge: a leading-edge-shaped heat

pipe with a relatively sharp leading edge and a thin wall thickness. Numerous fabrication

issues were resolved in the fabrication of both the heat-pipe container and wick. The heatpipe was fabricated from arc cast Mo-41Re, used lithium as the working fluid, and had a

D-shaped cross-section. The heat-pipe wick was constructed with 400 x 400 mesh Mo-

5Re screen with a single artery along the length of the heat pipe. The heat pipe was

tested in a vacuum chamber at LANL using induction heating.



3

Description of Heat-Pipe-Cooled Leading-Edge Concept

Heat pipes have been considered for use on leading edges of hypersonic vehicles.A brief description of how heat pipes operate and are applied for leading-edge cooling is

first presented, followed by a description of the proposed heat-pipe-cooled leading-edge

concept.

Heat input Heat output

CondenserEvaporator

Vapor flow

Capillary wick Liquid flow

Container

Figure 1: Schematic diagram of the operation of a heat pipe showing the heat-pipe

container, working fluid, and wick.

Leading-Edge Heat-Pipe Operation

Heat pipes transfer heat nearly isothermally by the evaporation and condensation of

a working fluid, as illustrated in Figure 1. The heat is absorbed within the heat pipe by

evaporation of the working fluid. The evaporation results in a slight internal pressuredifferential that causes the vapor to flow from the evaporator region to the condenser

region, where it condenses and gives up heat. The cycle is completed with the return

flow of the liquid condensate to the evaporator region by the capillary action of a wick.

Condenser

Condenser

Vapor flow

Heat pipeEvaporator Aerodynamic heat inputHeat radiated awayNet heat input

Figure 2: Schematic diagram of a heat-pipe-cooled leading edge showing regions of net

heat input (evaporator) and net heat output (condenser).



4

Heat pipes provide cooling of stagnation regions by transferring heat nearlyisothermally to locations aft of the stagnation region, thus raising the temperature aft of

the stagnation region above the expected radiation equilibrium temperature. When

applied to leading-edge cooling, heat pipes operate by accepting heat at a high rate over a

small area near the stagnation region and radiating it at a lower rate over a larger surface

area, as shown in Figure 2. The use of heat pipes results in a nearly isothermal leading-edge surface, thus reducing the temperatures in the stagnation region and raising the

temperatures of both the upper and lower aft surfaces.

Refractory Composite Heat-Pipe-Cooled Wing-Leading-Edge

The refractory composite heat-pipe-cooled wing-leading-edge concept is illustrated

in Figure 3. The heat pipes are oriented normal to the leading edge and have a D-

shaped cross section, with the flat part of the D forming the wing-leading-edge outer

surface. The leading edge comprises J-tube heat pipes, with a J-tube heat pipe beinga heat pipe with a long leg on one side of the nose region, and a short leg on the other

side of the nose region, as shown in Figure 3. An alternating J-tube configuration wasselected to minimize heat-pipe spacing in the nose region where heating is the highest,

provide a greater heat-pipe spacing on the upper and lower surfaces where heating islower, and at the same time minimize mass. The refractory composite structure sustains

most of the mechanical structural loads and also offers ablative protection in the event of

a heat-pipe failure.

Figure 3: Schematic drawing of a hypersonic vehicle with a diagram of a heat-pipe-

cooled wing leading edge.

The maximum operating temperature capability of coated refractory-composite

materials for the primary structure of the leading edge is high (~3000°F) relative to

refractory metals, which are typically limited to approximately 2400°F. The potentiallyhigher operating temperature increases the radiation heat-rejection efficiency of the heat-

pipe-cooled leading edge and permits reductions in the mass of the leading edge for a

given leading-edge radius. In addition, the higher operating temperature increases thetotal heat load that can be accommodated passively by the heat pipe (i.e., no forced

convective cooling required). For many trajectories, the high operating temperatures help

eliminate the need for active cooling during both ascent and descent, thus eliminating the

need for carrying additional hydrogen fuel (coolant) into orbit. Since many hypersonic

Heat pipes• "D-shaped" cross section• Alternating "J-tubes" Mo-Re heat pipe,

Lithium working fluid

Carbon/carbon

structure

NASA



5

vehicles return unpowered for landing, the additional hydrogen fuel needed for coolingduring descent would result in a mass penalty.

Figure 4: Photograph of Mo-Re nose section and similarly shaped machined graphiteembedded in C/C.

To evaluate the ability to embed leading-edge-shaped heat pipes in C/C, a truncatedheat-pipe container (just the nose section) was embedded in C/C along with two pieces of

graphite machined to the same shape as the Mo-Re nose section, as shown in Figure 4.

The goal was to obtain experience embedding curves tubes in C/C prior to embedding

actual heat pipes. The graphite and Mo-Re tubes were inserted into a 3-D woven carbonpreform (T-300 fibers) and the preform was then densified by Carbon-Carbon Advances

Technologies (C-CAT), Fort Worth, TX. Tooling was used on both the inner and outer

surface of the leading-edge component. Grafoil®, a soft carbon layer, was bonded to the

metallic tube with superglue prior to inserting it in the woven preform.

Results and Discussion

A single D-shaped cross section heat pipe in the shape of a leading edge was

fabricated and tested at LANL. Several fabrication issues were resolved in the

fabrication of the heat-pipe container and the wick. After fabrication, the heat pipe wastested at LANL using induction heating in a vacuum chamber. Premature failure of the

heat pipe occurred due to electrical discharge from the induction heating concentrator to

the heat pipe. A discussion of the fabrication, testing, and failure follows.

Fabrication

Due to the small leading-edge radius of 0.5 in., fabrication of the nose region of theheat pipe was challenging. The J-tube heat pipe has a D-shaped cross section and is

shaped like a leading edge, but has only a short leg on one side of the nose region, and a

long leg on the opposite side of the nose region. Several techniques were evaluated tofabricate the nose region of the heat pipes. Bending the D-shaped tube to the desired

radius was not found to be feasible, nor was bending sections and then welding the nose

together. The technique that was finally decided upon was to machine the nose



6

components out of a solid piece of Mo-41Re and weld them together to form the noseregion. Figure 5 is a photograph of the two nose section pieces individually and welded

together with the tubing on both sides. The end plugs and a cover to be placed over the

fill tube are also shown in the photograph. The machining, tube drawing, and welding

were performed by Thermo Electron Tecomet, Wilmington, MA.

Figure 5: Photograph of the individual machined nose components and the completed

nose assembly with the end plugs and fill tube cover.

The artery was fabricated by wrapping three layers of 400 x 400 mesh Mo-5Re

screen around a 0.125-in. outer diameter steel mandrel which was held in place with a0.003-in-diameter steel wire spirally wrapped the length of the artery. The steel

mandrel/screen assembly was inserted into a 0.25-in. outer diameter by 0.035-in. wallsteel sheath. The steel sheath was drawn down to a 0.210-in. outer diameter. After the

final draw, the assembly was immersed in a water/hydrochloric solution and the steelmandrel, sheath, and wire were dissolved leaving the formed screen artery.

36°

0.305 in.Screen wick

Artery

Figure 6: Schematic diagram of the dimensions of the artery prior to bending for

fabrication of the nose section.

The screen wick was fabricated by wrapping the first two layers of 400 x 400 mesh

screen over a copper mandrel that had been machined to the wick’s final shape. The

artery was placed over the first two layers of screen and the final two layers of screen



7

were wrapped over the mandrel and artery and the edge of the final wrap was spot weldedthe length of the wick. The assembly was then slid off the copper mandrel.

Figure 7: Photograph of the nose portion of the wick on a mandrel.

Portions of the screen wick were removed in the nose portion of the wick as

illustrated in Figure 6. This allowed the screen wick to bend and still maintain acontinuous artery through the nose section of the heat pipe. The angle of the screen that

was cut out was 36°, with a 0.305-in. spacing between the cut regions on the outside

surface. A photograph of the nose portion of the screen wick on a mandrel with a solid

rod used to support the artery is shown in Figure 7.

A photograph of the inside bend of the heat pipe with the screen wick beingwrapped around is it shown in Figure 8. In the figure the region of the wick where

sections were cut out in the nose region can be seen. The straight sections of the wick are

also shown. The nose section of the wick was formed by bending the wick assembly onthe machined parts that form the nose section. Figure 9 shows the screen wick in its

final configuration. The artery can be seen extending from the upper portion of the wick

in the photograph.

Figure 8: Photograph of the screen wick in the nose region prior to bending around the

machined nose part.



8

Figure 9: Photograph of the screen wick in the nose region after fabrication.

Testing

After the heat pipe was assembled, 0.017 lb (7.5 g) of lithium were loaded into the

heat pipe by distillation, as described in ref. 20. The heat pipe was wet-in at 3170°F for53 hours in a vacuum furnace. After wet-in, the heat pipe was oriented with the short leg

of the heat pipe on the top and the long leg on the bottom and placed in a vacuum test

chamber. An rf-induction coil/concentrator was used as the heat source. The heating

device was designed to heat the entire width of the flat portion of the heat pipe for achord length of 1.6 in. in the nose region. Initial tests heated the heat pipe to 1700°F,

resulting in a heat flux of approximately 362 Btu/ft2-s. Figure 10 shows a photograph of

the heat pipe during initial testing in the vacuum chamber. The induction heatingconcentrator can be seen on the outside of the nose region. In the photograph, the noseregion is hotter than the rest of the heat pipe since the photograph was taken during

startup.

In order to put enough heat into the heat pipe to heat the entire heat pipe to

operating temperatures, a large amount of heat was required in the nose region. Duringinitial testing of the heat pipe, the inside surface of the nose region remained hotter than

the outside heated surface. The hot spot was due to the fact that the inside surface was

heated by the induction heating but was not adequately cooled by the liquid lithium. The

heating distribution resulted from the nature of induction heating, which inductively heats

the entire nose region. The inside surface of the nose region was not cooled adequatelydue to the discontinuous wick, as shown in Figure 7. In the actual application, inadequate

cooling of the inside surface would not be a problem since it would not be subjected tothe aerodynamic heating.

The approach taken to solve the hot spot problem was to insulate the inside, curved

surfaces of the heat pipe. In actual operation, the inside surface would radiate away only

a minimal amount of heat. If the inside surface were insulated, then less heat input would



9

be required to bring the heat pipe up to operating temperatures. With less heating in thenose region, the inside surface of the nose region might not develop a hot spot.

Figure 10: Photograph of the heat pipe during initial testing with induction heating

concentrator in the nose region.

The heat pipe was mounted inside the vacuum chamber with the nose region facing

a new rf concentrator and coils, as shown in Figure 11. RF power was induced from thecoils to the concentrator and then to the heat pipe. Porous refractory insulation that had

been baked for several days at 1880°F was placed on inward facing surfaces to reduce

radiative coupling between the heat pipe and the chamber walls. In the photograph, the

insulation is seen to cover only the curved portion of the heat pipe. (The photograph inFigure 11 was taken after the accident to be discussed later. Holes seen in the copper

cooling coils resulted from the accident.)

Figure 11: Photograph of insulated heat pipe positioned in rf concentrator.



10

xx x x

x

xxx

s = 0.0

Appliedheatflux TC1

TC2 TC3

TC4 TC5 TC6 TC7 TC8

Heat pipe

Insulation

Figure 12: Schematic drawing of the insulated heat pipe with thermocouples.

W/W-Re thermocouples were placed on the heat pipe by strapping them down with

wire since experience welding thermocouples on a different Mo-Re heat-pipe container

was unsuccessful.18 Though the temperature uncertainty was greater than if thethermocouples were welded, the operation of the heat pipe was not compromised by the

instrumentation. Two thermocouples were located on the upper surface (the short leg),

and six were located on the (long leg) lower surface. The thermocouple locations relative

to the stagnation line are shown in Figure 12 and listed in Table 1, where the negative

numbers refer to the short leg on the upper surface.

Table 1: Location of Thermocouples

Thermocouple Position, s, in.

1 1.2

2 -1.4

3 -3.54 8.1

5 14.9

6 21.8

7 28.7

8 30.7

Four tests were performed on the heat pipe prior to catastrophic failure of the heatpipe. In each case, the heat pipe was started up over the course of several hours. Though

neither isothermal nor design temperatures were obtained, the heat pipe was operational.

Due to outgassing from the insulation, high heat fluxes were not obtained. Figure 13

shows the start-up data for the heat pipe during the first test with insulation.Thermocouples 1 and 2 indicated similar temperatures since they were similar distances

from the stagnation line. Since the thermocouples were strapped onto the heat pipe, the

accuracy of the readings is unknown. However, it is likely that the actual heat-pipetemperature was higher than the thermocouple reading.

The start up data from the second test is shown in Figure 14. As in Figure 13, the

start up was quite slow. In this case, the heat flux was reduced after about six hours, and

then increased again. Steady state temperatures were then obtained, but the heat fluxvalues were too low to attain isothermal operation. The start-up data from test three is

shown in Figure 15. Though the start-up was slower, the maximum temperatures attained

were similar.



11

0

500

1000

1500

2000

Temp., °F

0 60 120 180 240 300 360 420 480

Time, min.

tc 1 - tc 8

Figure 13: Start-up data for heat pipe during initial test.

The start-up data for the final test is shown in Figure 16. The temperature readings

for thermocouples 3 - 8 seem to flatten out at lower temperatures than in the three priortests. The cause of this is unknown. Approximately 250 minutes into the test, electrical

discharge was noticed in the vacuum chamber and the induction heating concentrator and

the heat pipe were destroyed.

0

500

1000

1500

2000

Temp., °F

0 60 120 180 240 300 360 420 480

Time, min

tc 1 - tc 8

Figure 14: Start-up data for heat pipe during second test.



12

0

500

1000

1500

2000

Temp., °F

0 60 120 180 240 300 360

Time, min

tc 3 - tc 8

tc 1tc 2

Figure 15: Start-up data for heat pipe during third test.

In the first two tests, the heat pipe was operational over most of the entire length,

while in two later tests, it was operational only over a portion of the heat-pipe length, asshown in Figure 17. The data in the figure represent the highest temperatures obtained at

a given time during the particular test, not steady state values. The stagnation line is

located at s = 0 in. The data for test 1 does not include a temperature at s = 8.1 in. since

the thermocouple was not functioning properly at the time. From the figure, it is apparentthat the leading edge shaped heat pipe did operate as expected, though design

temperatures and heat fluxes were not obtained.

0

500

1000

1500

2000

Temp., °F

0 60 120 180 240 300

Time, min

tc 1

tc 3 - tc 8tc 2

Figure 16: Start-up data for heat pipe on final test.



13

0

500

1000

1500

2000

Temp, °F

-5 0 5 10 15 20 25 30

Position, in.

Stagnationline

Test 1

Test 4

Test 3

Test 2

Figure 17: Maximum heat-pipe temperatures during the four tests.

Failure

During the third test, the heat pipe was started from the frozen state over 6 h. Anindication of ionization was occasionally observed as the heat pipe grew warmer. This

ionization was attributed to outgassing of volatiles from the insulation. Power was

increased and the chamber pressure was monitored. When the chamber pressure neared

1x10-4 torr the power was kept constant until the insulation had outgassed volatiles at that

temperature and the chamber pressure fell below 2x10-5

torr. After reaching 1296°F, theheat pipe was shut down after repeated discharge (violet glow) in the vacuum chamber.

During the fourth and final test, the heat pipe was again started from the frozen

state. After 250 min, light suddenly flashed from the chamber. The rf generator was shutdown within 10 s of the first flash of light. After the generator was shut down, the heat

pipe and chamber were inspected. High vacuum was lost and standing water was seen on

the bottom of the vacuum chamber. The chamber was then opened. Large holes werefound on the upper and lower heat-pipe surfaces. Numerous holes penetrated the copper

rf coil wall in the turn nearest the heat pipe.

The heat pipe most likely failed when volatiles (water vapor) in the refractoryinsulation outgassed, raising the gas pressure in the rf coil-heat pipe gap above 0.1 torr.A violet-colored electric discharge followed between the rf coil (anode) and the heat pipe

(cathode). At some point, the transfer of charge carriers across the gas gap was

apparently sufficient to form multiple holes in the copper rf coil.

After the failure, a blue-colored coating was seen on grounded copper surfacesinside the vacuum chamber. The hypothesis is that the blue coating is plated



14

molybdenum. If true, this suggests significant removal of molybdenum during thedischarge. The heat-pipe wall was 0.010-in. thick where the holes formed.

An order of magnitude estimate of the time required to form a hole the size found in

the copper rf coil, assuming a 1 kV potential between the coil and heat pipe, resulted in a

time estimate of 1 second. Once a hole formed in the rf coil, 70 psi water flowed into thechamber and onto the heat pipe. Whether the large holes formed in the heat pipe and coil

before or after the water started flowing is uncertain, but probably unimportant. The

water resulted in a sudden rise in chamber pressure and reacted with the lithium from the

heat pipe.

In future tests, it is recommended that refractory insulation with high vapor pressure

contents be avoided. Foil radiation shields are one possibility for insulating the surfaces.

This would pose a potential problem with inducing rf onto the foil, but that would be a

less sever problem than the one experienced here.

Concluding RemarksA leading-edge-shaped Mo-Re heat pipe was fabricated and tested. Several

container and wick fabrication issues were resolved that arose due to the small 0.5-in.

leading-edge radius. The heat pipe was tested in a vacuum chamber with induction

heating, but prematurely failed due to electrical discharge between the induction heatingconcentrator and the heat pipe. The heat pipe did start up as expected and operated as a

heat pipe, however, not at design heat fluxes and temperatures. Though a testing

anomaly caused premature failure of the heat pipe, successful startup and operation of theheat pipe are key steps toward the development of heat pipes for cooling sharp leading

edges.

Acknowledgment

The authors would like to thank the Thermal Structures Branch at NASA Langley

Research Center for funding this work under Contract No. NAS1-96014.

References

1Silverstein, C. C., A Feasibility Study of Heat-Pipe-Cooled Leading Edges for

Hypersonic Cruise Aircraft, NASA CR 1857, Nov. 1971.2Niblock, G. A., Reeder, J. C., and Huneidi, F., Four Space Shuttle Wing Leading

Edge Concepts, Journal of Spacecraft and Rockets, Vol. 11, No. 5, 1974, pp. 314-320.3Alario, J. P., and Prager, R. C., Space Shuttle Orbiter Heat Pipe Application,

NASA CR 128498, April 1972.4Anon., Study of Structural Active Cooling and Heat Sink Systems for Space

Shuttle, NASA CR 123912, June 1972.5Anon., Design, Fabrication, Testing, and Delivery of Shuttle Heat Pipe Leading

Edge Test Modules, NASA CR 124425, April 1973.6Camarda, C. J., Analysis and Radiant Heating Tests of a Heat-Pipe-Cooled

Leading Edge, NASA TN D-8468, Aug. 1977.



15

7Camarda, C. J., Aerothermal Tests of a Heat-Pipe-Cooled Leading Edge at Mach7, NASA TP-1320, Nov. 1978.

8Camarda, C. J., and Masek, R. V., Design, Analysis and Tests of a Shuttle-Type

Heat-Pipe-Cooled Leading Edge, Journal of Spacecraft and Rockets, Vol. 18, No. 1,

1981, pp. 71-78.9

Peeples, M. E., Reeder, J. C., and Sontag, K. E., Thermostructural Applications of Heat Pipes, NASA CR 159096, June 1979.

10Boman, B. L., Citrin, E. C., Garner, E. C., and Stone, J. E., Heat Pipes for Wing

Leading Edges of Hypersonic Vehicles, NASA CR 181922, Jan. 1990.11Boman, B. L., and Elias, T., Tests on a Sodium/Hastelloy X Wing Leading Edge

Heat Pipe for Hypersonic Vehicles, AIAA Paper 90-1759, June 1990.12Merrigan, M. A., Sena, J. T., and Glass, D. E., Evaluation of a Sodium/Hastelloy-

X Heat Pipe Designed to Cool the Wing Leading Edge of an Advanced SpaceTransportation System, Proceedings of the ASME Heat Transfer Conference, Houston,

TX, August 1996, pp. 333-341.13Clark, L. T., and Glenn, G. S., Design Analysis and Testing of Liquid Metal Heat

Pipes for Application to Hypersonic Vehicles, AIAA Paper 88-2679, June 1988.14Wojcik, C. C., Niobium Alloy Heat Pipes for Use in Oxidizing Environments,

8th Symposium on Space Nuclear Power Systems, Albuquerque, NM, January 1991, pp.

326-333.15Wojcik, C. C., and Clark, L. T., Design, Analysis, and Testing of Refractory

Metal Heat Pipes Using Lithium as the Working Fluid, AIAA Paper 91-1400, June

1991.16Glass, D. E., and Camarda, C. J., Preliminary Thermal/Structural Analysis of a

Carbon-Carbon/Refractory-Metal Heat-Pipe-Cooled Wing Leading Edge, Thermal

Structures and Materials for High Speed Flight, edited by E. A. Thornton, Vol. 140,

Progress in Astronautics and Aeronautics, AIAA, Washington, DC, 1992, pp. 301-322.17

Glass, D. E., Camarda, C. J., Sena, J. T., and Merrigan, M. A., Fabrication andTesting of Heat Pipes for a Heat-Pipe-Cooled Leading Edge, AIAA 97-3876, August

1997.18Glass, D. E., Merrigan, M. A., and Sena, J. T., Fabrication and Testing of Mo-Re

Heat Pipes Embedded in Carbon/Carbon, NASA/CR-1998-207642, March 1998.19Glass, D. E., Camarda, C. J., and Merrigan, M. A, Refractory-Composite/Heat-

Pipe-Cooled Leading Edge, U.S. Patent No. 5,720,339, Feb. 1998.20Merrigan, M. A., Keddy, E. S., and Sena, J. T., Transient Performance

Investigation of a Space Power System Heat Pipe, AIAA Paper 86-1273, June 1986.



REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing datasources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any otheraspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations andReports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188),Washington, DC 20503.

1. AGENCY USE ONLY (Leave blank ) 2. REPORT DATE

October 19983. REPORT TYPE AND DATES COVERED

Contractor Report

4. TITLE AND SUBTITLE

Fabrication and Testing of a Leading-Edge-Shaped Heat Pipe5. FUNDING NUMBERS

NAS1-96014WU 242-33-03-20

6. AUTHOR(S)

David E. Glass, Michael A. Merrigan, J. Tom Sena, and Robert S. Reid

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

Analytical Services & Materials, Inc.107 Research DriveHampton, VA 23669-1340

8. PERFORMING ORGANIZATIONREPORT NUMBER

AS&M-LS05-98-03

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space AdministrationLangley Research CenterHampton, VA 23681-2199

10. SPONSORING/MONITORINGAGENCY REPORT NUMBER

NASA/CR-1998-208720

11. SUPPLEMENTARY NOTES

This report was prepared by Analytical Services & Materials, Inc., under subcontract to Lockheed MartinEngineering & Sciences, Hampton, Virginia, under NASA Contract NAS1-96014 to Langley Research Center.Langley Technical Monitor: Steven J. ScottiAn electronic version of this report can be found at: http://techreports.l arc.nasa.gov/ltrs

12a. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified-Unlimited

Subject Category 34 Distribution: NonstandardAvailability: NASA CASI (301) 621-0390

12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words)

The development of a refractory-composite/heat-pipe-cooled leading edge has evolved from the design stage tothe fabrication and testing of a full size, leading-edge-shaped heat pipe. The heat pipe had a “D-shaped” crosssection and was fabricated from arc cast Mo-41Re. An artery was included in the wick. Several issues wereresolved with the fabrication of the sharp leading edge radius heat pipe. The heat pipe was tested in a vacuumchamber at Los Alamos National Laboratory using induction heating and was started up from the frozen stateseveral times. However, design temperatures and heat fluxes were not obtained due to premature failure of theheat pipe resulting from electrical discharge between the induction heating apparatus and the heat pipe. Thougha testing anomaly caused premature failure of the heat pipe, successful startup and operation of the heat pipe wasdemonstrated.

14. SUBJECT TERMS

Heat pipes, liquid metals, leading edges15. NUMBER OF PAGES

20

16. PRICE CODE

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Fabrication and Testing of a Leading-Edge-Shaped Heat Pipe

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