An exothermic furnace module was developed to rapidly heat and cool a 0.820-in. (2.1 cm) diameter by 2.75-in. (7.0 cm) long TZM molybdenum alloy crucible. The crucible contains copper, oxygen, and carbon for processing in a low-g environment. Peak temperatures of 1270 C were obtainable 3.5 min after start of ignition, and cooling below 950 C some 4.5 min later. These time-temperature relationships were conditioned for a foam-copper experiment, Space Processing Applications Rocket experiment 77-9, in a sounding rocket having a low-g period of 5 min

Darnell, R. R.

Poorman, R. M.

English

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NASA TECHNICAL
MEMORANDUM
J
NASA -82500
EXOTHERMIC FURNACE MODULE DEVELOPMENT
n
i
1
By Roy R. Darnell and Richard M. Poorman
Materials Processing In Space Projects Office
September 1982
OCT 1982
C	 RE IVEDa
NASA FACILITY
u^ ACCESS DEPT.
NASA
George C. Marshall Space Flight Center
Marshall Space Flight Center, Alabama
WFC . rem 1" (R.. Jm. 1971)
TtP•uY.l-A. afaAoT ITAYAAnn TITL < WAdff
1. REPORT NO. GOVOINMSNT ACCESSION NO. S. RRCIPIENT'S CATALOG NO.
NASA TM -82500
IT
4. TITLE AND SUBTITLE S. REPORT DATE
September 1982
Exothermic Furnace Module Development . B. PERFORMING ORGANIZATION CODE
7. AUTNOR(S) $.PERFORMING ORGANIZATION REPORT AI
Ray R. Darnell and Richard M. Foorman
G. PERFORMING ORGANIZATION HAMS AM ADDRESS 10. WORK UNIT NO.
George C. Marshall Space Flight Center 11. CONTRACT OR GRANT NO.
Marshall Span* Angith Center, Alabama 	 35812
IS. TYPE OF REPORT	 PERIOD COVERED
12. SPONSORING AGENCY NAME AM ADORESS
Technical Memorandum
National Aeronautics and Space Administration
Washington, D. C.
	
20546 14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
Prepared by Materials Processing In Space	 rojects Office
1G. ABSTRACT
An Exothermic Furnace 11odule (EFM) has been developed tc Vapidly heat and
cool a 0.820-in. (2.1 cm) diameter by 2.75-in. (7.0 cm) long TZM h1dybdenum alloy
crucible.	 The crucible contains copper, oxyge.z, and canon for prwassing in a
low-g environment.
	 Peak temperatures of 127000, were obtainable 3.5 min after start
of ignition, with cooling below 950 0C some^4 . 5 min later.	 These time-temp pre
 ure
relationships were conditioned for a Foam-Copper Experiment, Space Processing
APPncations Rocket (SPAR) Experiment 77-9, in a sounding roc%et having a low-g
Period of 3 min.	 i
t
t
r
r
17. KEY WORDS 16. DISTRIBUTION 37AT[MENT
Exothermic
Furnace
Foam-Copper Unclassified — Unlimited
Low gravity
Space Processing Applications Rocket(SPAR)
Materials Processing in Space
19.
	
SECURITY CLASSIF. (d tMM trPwt/
	 120. SECURITY CLASSIF. (.t NW p".) 21.	 N0. OF PAGES 22.	 PRICE
Unclassified Unclassified 14 NTIS
WVC - /.rS 73" (MY I"t)
fob taN ►s IYM^1 T^eWaa3 LLee^atlo^ B.,"w. N>. vle^ty^ f41i1
TABLE OF CONTENTS
Page
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I. SUMMARY ............................................ ............
II. BACKGROUND .....................................................
	III .	 FEASIBILITY TE'O TS ............................................ , .. .
	IV.	 DEVELOPMENT TESTS .............................................
	C.	 ADDITIONAL 'DEVELOPMENT EFFORTS .............................
VI. GASES OF THE BURNING EXOTHERMIC MATERIAL ................
VII. POTENTIAL APPLICATIONS ........................................
VIII. RECOMMENDATIONS ...............................................
LIST OF ILLUSTRATIONS
Figure
	
Title
1. Basic furz .ace installation ..........................................
2. Basic furnace configuration ........................................
3. Furnace assembly ..................................................
4. Exothermic furnace module, Run No. 9, May 21, 1982 ..............
5. Exothermic furnace module, Run No. 10, June 4, 1982 .............
6. ]Exothermic furnace module, Run No. 11, June 10, 1982 ............
FRECED I NGa ^ri s. . ii: iC^ IiStr f	 iL:il..
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s
TECHNICAL MEMORANDUM
EXOTHERMIC FURNACE MODULE DEVELOPMENT
I. SUMMARY
An Exothermic Furnace Module (EFM) has been developed to rapidly heat and
cool a 0.820-in. (2.1-cm) diameter by 2.75-in. (7.0-cm) long TZM Molybdenum alloy
crucible. The crucible contains copper, oxygen, and carbon for processing in a law-g
environment. In the EFM peak temperatures of 1270°C were obtainable 3.5 min after
start of ignition, with cooling below 950°C some 4.5 min later. These time-temperature
relationships were conditioned for a Foam-Copper Experiment, Space Processing Appli-
cations Rocket (SPAR)Experiment 77-9, in a sounding rocket having a low-g period
of 5 min. The overall furnace enclosure is 8-in. (20-cm) diameter by 9-in. (23-cm)
long, weighing 30 lb (14 kg) when mounted in an 11-in. (88-cm) SPAR canister.
Ignition of the exothermic material requires 22 A at 34 V for a period of 1.5 min.
II. BACKGROUND
SPAR VII was scheduled to process a Foam-Copper Experiment (SPAR Experi-
ment 77-9) per MSFC-SPEC-937. Dr. R. B. Pond, Sr., and J. M. Winter, Jr., are
the Principal Investigators (PIa) . The experiment was originally intended for pro-
cessing in the General Purpose Rocket Furnace (GPRF) . Evaluation of the flight
model showed that this furnace could not reliably meet the experiment temperature
requirements.
Independent of the Foam-Copper Experiment, and prior to the GPRF functional
evaluation, some feasibility tests (3.0) had been made using exothermic materials.
This work was primarily related to a cast iron solidification experiment that was under
consideration. These tests did define a reliable electrical ignition system and the
potential of very rapid heating to high temperature, 14000C.
With this background, an effort was initiated in February 1981 to develop (4.0)
an EFM for processing SPAR Experiment 77-9.
III. FEASIBILITY TESTS
Exothermic materials have been used for many years as high energy heat
sources. Literature shows several companies marketing exothermic material for various
heat treating processes. Exomet, Inc., being one, was contacted and they recom-
mended two of their commercial products. First, their Exomold LDK has a moderate
burn rate and internal temperatures of 15000C. Second, Exomold LDKK has a higher
burn rate and internal temperatures of 1700 0C. Work was initiated with the latter.
The first step was to develop an electrical ignition or start of the exothermic
reaction. A small sample of the Exomold LDKK was compacted around a 0.028-in.(0.1-mm) diameter Kanthal A-1 resistance wire. The wire had been formed into a
0.19-in. (4.8-mm) diameter helix. Tests showed good positive ignition when 10 to
12 A were passed through the wire.
Next step was to compact Exomold LDKK into a 4-in. (10-cm) diameter by 9-in.(23-em) long cylinder around a stainless steel rod. The rod, which was 0.75-in. (1.9 cm)
in diameter and approximately 7-in. (18-cm) long, was placed so the rod and cylinder
were coaxial. The end of the rod was flush with the end of the cylinder of the exothermic
material. The assembly was placed with the flush end on a lire brick for the evaluation.
The electrical ignition system was embedded at the bottom and energized. A
burn rate of 2 to 3 in. (6.3 cm) per minute was observed. The steel rod in the
center did not melt. However, same superficial surface melting was indicated. A
few additional tests confirmed the ignition system and the rapid heating to high tem-
peratur ss and slow cooling rates for a the-malty insulated package. Cooling rates
of 20°C /min were noted.	 .
IV. DEVELOPMENT TESTS
In February 1981, the need for a furnace to process the Foam Copper Experi-
ment in SPAR became apparent and a development effort was started. A basic
approach was defined:
1) An ignition system, essentially as had been tested, would be baselined
2) Use multiple segments of Excamold LDKK
3) Sample would be centered inside a cylinder of Exomold LDKK
4) Gas cooling system - carbon dioxide
5) Two ignition points for a shorter period of burn to completion.
All of these are now shown In Figures 1, 2, and 3.
First tests were made with Exomold LDKK segments 3.5-in. (9-cm) diameter,
a 0.88-in. (2-cm) hole, and 0.63-in. (1.6-em) long. Basically the segment was a
"donut" configuration. Some nine segments were stacked. A stainless steel crucible
was supported in the center of the stack. The stack was insulated with 2.5-in.
(6.3-cm) thick high temperature wool, basically quartz. The crucible was sized to
simulate the experiment sample, both in outside dimensions and specific heat. Thermo-
couples were mounted on each end of the stainless steel crucible.
Upon ignition, the lead wires to both thermocouples melted where they were
exposed to the hot exotherm. The stainless steel crucible melted and ran freely into
the alumina support system. It was concluded that the peak temperatures were in
excess of the melting point of stainless, 14000C.
4
Subsequent runs were made with 2.5-in. (6.3-cm) diameter exothermic segments
proved thermal insulation on the thermocouples. Temperatures measured were
well in excess of 1200°C. Next, 2-in. (5-om) diamete _-P segments were used. They
provided temperatures between 1100 and 1200°C and have been used in all subsequent
work.
Based on tests to this point, a more flight-type oontiguration was made. A
ground test . TZM crucible-copper sampld supplied by the PI was substituted for the
stainless steel crucible. The configuration is shown in Figure 1, 2, and 3. Figure 1
shows the basic furnace, which is 8 in. (20 cm) in diameter and $-in. (23 am) long,
with cooling gas bottle and nonpropulsive vent all mounted in an 11-in. (28-om) long
SPAR canister, 17.5-in. (44.5-cm) diameter. Figure 2 shows two coils of ignition
wire "B." Each has 31 in. ( 79 cm) of 0.0285-in. (0724-mm) diameter Kanthal A-1
wire. The helix is 0.153-in. ( 3.89-mm) outside diameter. The ignition coils are
paralleled on 34 Vdc and together draw a total of 22 A. Nine segments of Exomold
LDKK were used in this configuration and Inconel 718 and Type 303 stainless made
up the support members. Cooling gas was stored in a 4 x 8 in. (10 x 20 cm) high
pressure gas storage bottle. " solenoid valve, when activated, allowed gas flow
through an orifice at the base ' the exothermic support structure. ^ Gaa flowed
through ducts directly to one .d of the TZM crucible.
Various insulations and sleeves were tested around the sample and exotherm
stack until the desired .fame-temperature relationships were obtained: 1) A peak tem-
perature between 1130 and 1200°C, 2) a temperature in excess of 1130°C for more
than 1 min, and 3) the time from start of copper melt until the copper had resofldi ted
shall be less than 5 min, the low gravity period for SPAR. However, a study of th-3
temperature data in these tests gave indications that the temperature in the center of
the TZM crucible was significantly hotter than the ends, where the thermocouples were
mounted.
This flight configuration with carbon dixode coaling gas met the Foam Copper
Experiment conditions. A flight package, less electronics for signal conditioning of
the thermocouple outputs, was vibration tested to the SPAR prototype criteria (ftfer-
ence Test Laboratory, ET19, vibration report "SPAR Exothermic Furnace Module Vibra-
tion, B-D-563"). There were no anomalies. The solenoid valve and fill valve were
observed by Stress Analysis EP46. They suggested the addition of mounting
supports for this plumbing to improve its long term reliability.
V. ADDITIONAL DEVELOPMENT EFFORTS
For several reasons, the EFM was not flown on SPAR as planed. In May 1982,
there appeared to be another sounding rocket launch that might accommodate the
Foam Copper Experiment. This rocket, however, would not -have the capability of
in-flight power, temperature recording system, or timing signals for proper initiation
of the cooling gas. Thus additional development was required.
A close study of data at this point revealed-
 that it might be possible ' to refine
the thermal insulation, use a more precise amount of exotherm, and meet the time-
temperature requirements without the use of cooling gas. Since the original experi-
ment did not have in-flight temperature records, work was directed to provide a
furnace operating with constraints of the May 1982 sounding rocket.
3
. The following tests wtwe made with a thermocouple in the center of the 'TIM
crucible and one on the bottom. As suspected, the center was found to be tAtter
than the end, 150°C hotter. Hence. a new wrinkle was tested, namsly, an inert
segment (firebrick) was placed in the middle of the stack. This provided a demired
reduction of the center temperature. The temperature difference from center to end
of the T SM crucible was measured a low as 500C. Further refinements could pro-
bably reduce this temperature difference even more.
Additions: balancing of the exotherm , insulation , and brick segment@ give atie-
factory temperatures. However, the time from melt to remolidilication was 5 min. In
that the cooling rate very likely would be less in !light than on the g-.,ound, flxrther
refinement was desirable.
The next series of tests used a heavy walled aluminum sleeve inside the furnace
lousing and around the exotherm stack. In principle, the aluminum sleeve reduced
the quarts wool insulation thickness. Also, the quarts wool was now packed to a
greater density and the venting of the spent exotherm gases more critical. However,
this approach did reduce the time from melt to resolidifiostion to about 5 min and
provided a satisfactory time-temperature profile. With essentially the some configura-
tion, three consecutive runs were made. The time from ignition power on until
resoliditication of all the copper was 7 min. There wr ►s a total variance of 15 sec
within these three runs. The peak temperatures had a variance of id and i°C fbr
the crucible center and bottom, respectively (Figs. 4, 5, and 6). Thus, the EFM
had proven its reproducibility.
VI. OASES OF THE BURNING EXOTHERMIC MATERIAL
The exothermic material has a phenolic based binder. During the reaction of
Exomold LDKK, a significant volume of gas is released. It is estimated at 4 standard
cubic feet (110 liters) for the RPM. A gas analysis was made of some gases collected
during the reaction. It is shown below.
H 2 51 percent
N 2 36 percent
0 2 01 percent
Co 2 14 percent
One might expect this composition to change during the reaction. No attempt was
made to define the change, if any exists.
VII. POTENTIAL APPLICATIONS
The EFM has four very different characteristics than furnaces in common use
today.
1) When it is started. it goes to completion in a pattern determined almost
entirely by its design.
3) It carries, in the ext-therm, the energy for the designed temperature
profile.
4
8) It appears to be highly reliable with no elemeW burn-outs. In all of the
tests of this effort, lierhaps 20, the exotherm performed in a oandstent manner. No
anomalies were noted related to the burn.
4) A significant volume of bas is released during the exothermic reaction.
These characteristics have advantages in MPS applications requiring rapid heat-
ing, high energies, and high temperatures. Sounding rockets and free fliers are
lUely to be vehicles for this combination of furnace and experiment. Shuttle applica-
tions may be constrained by the off-gases of the exothermic reactions.
A wide range of exothermic materials are marketed today. They can be sized
for the desired temperature conditions. The upper Limit for temperature is probably
1500 to 2000°C when using commonly known materials.
VIII. RECOMMENDATIONS
It is recommended that the EFM be utilized to process the Foam Copper Experi-
ment on either SPAR X or any other suitable sounding rocket. The EFM is extremely
simple in operation and should prove highly reliable. Preintegration testing should be
initiated for SPAR X when concurrence is received from! the PIs and the SPAR Con-
Sgurstion Control Board.
EM
5
ORIGINI Ai_ P'jN'"F IS
OF POOL 
Figure 1. Basic furnace installation.
	 Figure 2. Basic furnace configuration.
6
ORIGINAL PAGE 1g
OF POOR QUALITY
Figure 3. Furnace assembly.
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OMINAL PAGE 1V
OF POOR OUALITY
131
0	 1	 Z	 3	 4	 6	 t	 7	 t
TIME - MINUTES AFTER IGNITION
Figure 4. Exothermic furnace module. Run No. 9, May 21, 1982.
8
0 W. Ct
OF PC? '),R QUALITY
0	 2	 3	 4	 6	 6	 7
TIME MINUTES AFTER IGNITION
Figure S. Exothermic furnace module, Run No. 13, June 4, 1982.
N
x
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UA
9
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aW6
W
ORIGINAL PAGE 13
cF POOR QUALITY
0	 1	 2	 3	 4	 6	 •	 7
TIME MINUTE'S' AFTER IGNITION
Figure 6. Exothermic furnace module, Run No. 11„ June 10, 1932.
10
_-^
	
- - - -
11
APPROVAL
EXOTHERMIC FURNACE MODULE DEVELOPMENT
By Roy R. Darnell and Richard M. Poorman
The information in this report has . been reviewed for technical content. Review
of  any information concerning Lapartment of Defense or nuclear energy activities or
programs has been made by the MSFC Security Classification Officer. This report,
in its entirety, has been determined to be unclassified.
9 V	 .
K. ZORLER
Manager, Materials Proeessing in Space
Projects Office


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