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CROPELLNY
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CLEVELAND S.WATERMAN
4 ~AUGUST1916i
ONMAORAY1y
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. . . ... .I
UNC LASSIFIE D
SECURITY CLASSIFICATION OF THIS PAGE (Whon 0.t. Entered)
DOCUENTAION
AGEREAD INSTRUCTIONS
REPORT DOUETTINPG EFOIPE COMPLETING FORM
_7ILandSu e We
ttvr gRC 6EIO
7. AUTHOR(#)
'40--R
1 14. MONITORING AGENCY NAME & ADDREES(II differenti trot" Controlling Office) 15. SECURITY CLASS. (of Ihla report)
AUNCLASSIFIED AJ
15. ECL ASSI F1CATION7DOWN GRADING
___________________________________________ __________SCHEDULE_____
17, DISTRIBUTION STATEMENT (of the aimtrmcl entered In Block 20, It different from Report.)J
2 19. KEY WORDS (Continue on reverse side If nec essary and idenltfy by block number)
I-ITPI3
72
o'/
TABLE OF CIONTENTS
Preface .. . . . . .. . . . . .. . . .1.. . . . . .
Introduction...................................................... 2
References...................................... ................ 18
Appendix I
GacIoFEngineering Maintenance Responsibilities................. ....... 20
Appendix II
Accid~nt at TestArea 1-21................................ ......... 22
Appendix III
Generaland Detailed Test Schedule. .. .. .. .... .... .... ...... .... .......... 25
Appendix IV
.. . .. .. .. ... . ... . .. ....... .28
.. .. .. ... ..
Propellant Ingredients Being Aged
j .,
iv
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I ILLUSTRATIONS
F1,gure Page
A..
PRE FACE
This technical report summarizes the work done on the In-House Propellant Aging
Program at the AFRPL between I November 1974 and 30 June 1976, No previous
technical reports have been published on this program.
The authors -wish to acknowledge those people who proved Invaluable to the
development of an aging capability at the AFRPL. MSgt. Louis Franks, TSgt.
Rex Thompson and Mr. Kelley Palmer were responsible for planning and over-
seeing the necessary construction of the facility. They also had the difficult task
of day-by-day maintenance of the environmental chambers and cutting the samples.
The actual aging of the propellants is only a part of the task. An important part
is samnple testing, and Mr. Tom Chew has done an excellent job at this.
Since 1972, the AFRPL has been building up an In-House capabilIty for aging solid
propellants. This initial work involved 'he selection of a site for the activities
and the procurements of equipment that would make accelerateu Qging of propel-
lant possible. This equipment consisted mostly of environmental chambers tlhat
could store propellant for long periods of time at constant humidity and tempera-
ture. By November of 1974, the facilities had expanded to a point where full bcale
aging of propellants could occur.
Once the facilities were in place and operating, a 6tandard procedure for utilizing
the capabilities had to be formulated, This procedure includes the timely insertion
of propellant 'ato the environmental chanmbers along with the subsequent
extraction and testing. Coordination of all facilities and personnel had to be
effected. This technical report summarizes how this task was accomplished.
Now that the capability and procedures have been established, future reports will
contain the actual aging data.
1,,,
,.-.
INTRODUCTION
It is the objective of this report to review the efforts which have led to the
development of the capability to perform an aging study at the AFRPL and to
review the types of propellants currently being aged. The reason for performing
aging studies at the AFRPL is to eliminate comparison problems among different
facilities by having a central facility to age and test propellants under identical
conditions.
! ', .. . . . . . .
S.Ilarge meters where the exothermi~c cure reaction can produce up to 9°0F higher
temperatures in ,;he center of the grain during cure. The temperature differential
results in different propellant properties. One way around this problem i½
s toh
e
determine the temperature gradient across the grain during cure and then to cure
cartons at the required temperatures to correspond to certain sections of the motor.
An additional problem with carton aging is that flow lines are introduced during
casting and the physical properties (as well as burn raie) will vary with these lines.
The flow (and thus properties) can be different in cartons and motors, and in
different parts of a motor.
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may see a relatively constant temperature whereas a tictical missile is exposed
to a varied temperature history. Davis and Nelson (reference #6) have shown for
an HTPB propellant that total time at an elevated temperature is the important;
factor and the same degree of damage occurs regardless of whether the exposure
for that time period is continuous or intermittent.
-4
i, j
II EXPERIMENTAL DETAILS
At present, the propellant aging work at Test Area 1-21 breaks down into two
distinct phases. First is a two-year long period during which the propellant is
stored under a variety of environmental conditions and is sampled and tested at
predetermined intervals. Second is an indefinite period of storage during which
no testing is planned. The propellant is available for testing should any aspe3ct of
that propellant be of possible future interest. For example, the importance of
propellants containing ferric fluoride was not known at the time of their receipt at
the AFRPL. However, the effect of ferric fluoride on the aging of reduced smoke
Maverick and SRAM propellants became of concern, and therefore the ferric
-fluoride containing propellant was tested one year after being placed in the A.FRPL
inventory. The second phase is sinmple. All that is needed is a shelf on which the
propellant can be stored under ambient conditions of temperature and humidity.
Phase I requires a great deal more planning, more facilities, and more data
handling. The primary thrust of this report will be to show how Phase I was
constructed and how it can be modified to permit the easy insertion of new pro-
pellants into the two year formal period of aging.
Since the two years is not considered long in the lifetime of a propellant, an
environment that would accelerate the aging process of the propellant is required.
Thus, the six environmental chambers at Test Area 1-21 are the heart of the In-
I-louse Propellant Ajing Program. Figure 1 gives a technical description of the
chambers being used. Prior to 1972, environmental control capability at the
AFRPL was very limited. Hlumidity control was obtained by placing various salt
solutions in ovens. Varying humidity was obtained by varying the solution. The
chambers for temperature control were in the open with only a sun shade over the
top and dirt bunkers on three sides. Under these conditions it was difficult to
The proper operation and maintenance of the ovens is critical to the entire
program. Years of aging could be wiped out overnight if the ovens malfunctioned.
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For example, the temperature controller could go astray and literally bake the
propellant. Just as bad, the humidity controller could fail and drown the propel-
lant. In the early years of the program both of these fatal malfunctions occurred.
* To prevent their future occurrence, reiundant high temperature cutoffs were
installed on both the wet and dry bulb temperature controls. If either of the set
points on these redundant controllers iJ exceeded, the entire oven is shut down.
S~For
example, a very high wet bulb te riper'ature indicates that the relative humidity
is high since the wet air can no longer cool off the wick in the wet bulb temperature
sensor. To completely avoid any break in the test schedulo, one of the six ovens
is held on a stanabv basis to take ovct" the duties of any one of the other five. ovens
that malfunctions and shuts dcwn. When such a malfunction occurs, the party
responsible for effecting repairs is (Cornponent Processing, also known as Chalco,
Inc. The duties of this organization are described mnore fully in Appendix I.
The actual use of the ovens 's relatively simple. The bulk samples of propel-
lant aru ut into blocks with the rough dimensions 5 in. x 4 in. x 3 in. for a short
test serios and 5 in. x 8 In. x 3 in. for a full test series. The series will be
describrd subsequently. A sufficient number of these blocks for carrying out the
two yearsi of formal aging and testing are placed into the ovens. The blocks are
wrapped on all sides except one so that any gradient effects can be meas'ired.
The blocks are placed in the ovens so that the exposed surface faces the door of
*the chamiber. if the exposed surface of the block were to face upwards, any
collection of water on the upper surface could pool. This is, of course,undesirable.
Care is also taken to avoid stacking the blocks on top of each other so that the
physical stress on all blocks is the same. Propellant is also stored under ambient
conditions for both Phase I and Phase I. Gradient effects are considered
negligible in ambient storage. No special wrapping precautions are taken. The
propellant is stored in various bulk sizes and various types of wrapping. For the
must part, however, the propellant in ambient storage is wrapped much like that
which is placed in the ovens.
After storage comes testing. The mechanical properties testing is, at present,
limited to uniaxial Instron testing. Thus, the only treatment of the bulk propellant
necessary is the cutting, milling, and stamping of the dogbones used in Instron
testing. Throughout the program, the tolerance of the din-iensioris of the dogbones
conform to the specifications laid down for a JANNAF Class C dogbone, Vigure 2
gives these dimensions, The rough cutting is accomplished using a Blue Chip
7
ah
4.951.02
1.00± .06
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1.00± .02
.50:L_.01
8.
Manufacturing Company circular saw. Slabs of propellant with a th•,ckness
roughly that of the finished dogbone are cut from the appropriate propellant
block. This slab is then machined with an Index Machine and Tool Company fly
spec milling machine till its thickness conforms to specifications. The final dog-
bones are then stamped from these slabs and are ready for testing. The dog-
bones derived from the propellant blocks are numbered and lettered as shown in
Figure 2. Testing on the Instron is done by triplicate runs using three dogbones
processed from the same slab. For example, the three dogbones numbered 5A,
5B, and 5C are tested at identical conditions. The data resulting from these
three dogbones is averaged for presentation.
This process, a, described here, sounds very quick and sinmple. Complications,
however, can set in. The 'rery nature of the material being cut and milled make
the process hazardous and necessitates remote control of the operation. Such
precautions proved necessary when a fire and explosLon occurred on 28 March 1976
resulting in severe damage to equipment,but no injury to the personnel operating
the equipment. Appendix II contains more information on this incident.
Once the dogbones are formed, they leave the purview of Project NX since
mechanical properties testing is the responsibility of Project NE. An engineering
request (ER) written by the project engineer of Project NX accomnpanies the dog-
bones to Test Area 1-30 fcr Instron testing. The ER calls out the temperature
and cross-head speed of the Instron at which each dogbone will be tested. There
are presently two Instron testing devices in operation at Test Area 1-30.
Specifications on these devices are given in Figure 3.
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causes different start dates for the formal two-year aging period of each
propellant. The stagger could not be made u.1iform (I.e., start a new propellant
each week) since the overlap of two schedules could cause an intolerable ,,umber
of tests to be performed in one week. A uniform stagger could also cause tests
downstream to be performed during ( irlstmas week in order to conform to the
basic test philosophy as described above. Each propellant testing schedule had
to be treated iadividually and thc earliest possible start date for insertion into
the ovens had to be determhied. A quick and simple graphical technique for
accomplishing this purpose was developed. A test plan for each propellant is slid
along a time scale drawn on a long piece of graph paper until an appropriate start
time can be determined. Information is then transferred to the graph paper con-
cerning the dates at which piopellant will be drawn from the ovens and tested.
Figure 4 shows this process in more detail. Any conflicts between propellant
schedules can be visualized as well as any test dates on holidays. Thus, the best
possible start time for each propellant can be quickly determined.
The generalized test plan that is the same for all propellants placed in the4
environmental chambers is as shown in Figure 5. The time is the number of
months from insertion into the ovens. The different ovens numnbered 1 through 6
are set at different operating conditions of constant temperature and relative
humidity. Appendix Ill contains a Standard Cutting Procedure that explains this
more fully and presents the test plan in detail as it presently stands. Oven #5 is
the stand-by oven that can take over the duties of any one of the other ovens in the
event of a malfunction.
As an example, at time point T 6 , the propellant has been in the ovens for six
months. Samples -vould be taken from ambient storage and from ovens #3 and #4.
They would be tested according to test series S,which is also called the short test
series. The engineering requests that would be generated by a propellant being
tested at time point T 6 would be as shown in Figure 6 and 7. The first ER directs
Test Area 1-Z1 personnel to extract half-blocks of propellant from the three storage
second ER directs Test Area 1-30 personnel to test these samples according to
the short test series. The day for cutting and the day for testing is called out on
the ER's so that coordination between the two groups can be obtained. The days
must also be specified so that there is a standardization of the length of time that
i"1 11
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Time Humnidity 90% RH 20% RH 30% RH 50% RH Huýmid i1
TO F
TI S S S S S
T3 S S S
-T6 S __ _ _ _ _ _ _ _ _ _ _ _ _ _
ST9_ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _
T12 F S S S S
T24 F S S S
1 77 0 F 907o RH
2 135OF 20% RH
3135SF 30% RH
4 135 0 F 50%1/ RH
6 170OF Ambient. (at present)
Chamber No. 5 is held in reserve in the event of failure of one of the other
C'' chambers.
Figure 5. General Test PlanI
,, = 10
ENGINCERING R$QUEST OT
01o THRWt
ER~
14
-XIEYOfMW 5 fEPLA69i HPI. FOýAiO.4 O4Ak 70, ýb4ICH WIZL~. USKID
OCT 72
I 'W IN
TDAT
E R.
Sample No. Temp. X-head Speed Sample No. Temp. X-head Speed
(Deg. Far.) (in/min) (Deg. Far. ) (in/min)
i:A. B.C 77 2.0 1:A, B, C 77 2.0
Z:A. B. C 77 2.*0 4:A, B, C 165 2.0
3:A, B, C 165 2.0 5:A, B, C 135 2.0
4:A, B. C -65 2.0 - :A
RB, C 40 2.0
B 0A 2.0
Sampl1.s 5:A, B, C are to be used as backup 8:A, B, C -40 2.0
spares and are not to be otherwise used. 9:A, B G -65 2.0
1 O:A, B, G 165 0.2
3.A. B.CG -40 -o 200
Samples 2:A, B, C are to be used as backup
spares for above tests. Ifnot needed as
spares, test 77'F and 2 in/mn..
AFRFL
FO MaPL ACES RPL FORM 0 -6,, AA 70, bIIHM WIRLL, 8USE 0S!
OCT 72 "
a sample spends between its extraction from the ovens and its testing. Samples
stored in oven #4 would lose the moisture gained from storage in the high
temperature - high humidity environment of oven #4. The loss of moisture would
cause a change i.i nmeasured mechanical properties. To circumvent this change,
propellant from oven #4 is cut in the woQrning and tested in the afternoon. It is not
possible to maintain such a schedule with all of the chambers because of man-
power and facility limitations. The cutting/testing schedule that is followed for
the ovens at their present settings is as follows for propellants extracted and cut
on some day D:
This way the less important parts of the full test series are eliminated.
The example ER shown in Figure 7 will result in 36 dogbones being tested.
Each one of thtse dogbones generates nine numbers upon testing which means that
this ER will reduce about 13 lbs of solid propellant 324 numbers. During the two-
year formal aging period, a single propllant will cause around 3300 new numbers J
to come into the world. ror the propellant now on hand at Test Area 1-21, around
V,16
_____ _____
_____ __ *
50, 000 numbe'.s will be presented ro the project engineer over the three years
required for testing all of the propellants. This is around 50 numbers per day,
seren days per week, for three years. Keeping track of all these numbers can lead
to problems. This problem is compounded by the fact that even though the pro-
gram has been in progress for a year, the numbers have only recently started
coming in. Thus, the project engineer immediately has to contend with approxi-
mately 10, 000 numbers. Therefore, the meth'-ds that will be employed to handle
the data are cnly just beginning to make themselves known. The techniques to be
used for cataloging the data will be greatly influenced by the data acquisition system
used in conjunction with the Instron. This syster. has not yet been flnali:e.i nor
is there any firm date for its completion. Ultimately', a computerik'd system will
have to be employed. Presently, a hard copy computer cutput is received by the
project engineer from the personnel at TETP responsible for data reduction. The
output consisits almost entirely of numbers with little alphamerl, information on it.
This puts the burden on the project engineer to identify the orig~n of the numbers as
:1
to propellant name, dogbone number, storage condition, and length of time at the
storage condition. Project NE, Mechanical Properties Testing, is nmaking progress
in this direction. Meanwhile, this information must be extracted from the hand-
writtcn data sheets generated at the time the tests are performed. This unfortunate
method of gathering is a result of the temporary system presently being used in
conjunction with the Instron.
17
id
REFERENCES
LI18/19I
,'I
APPENDIX I
Change w icks
Monthly
Monthly
J
Inspect wiring, heaters, insulation,, Monthly
I'i
and connections
120
Chamber #Z
Chamber f#1
211
hi
Y.,.>,.***
JL
APPENDIX II
On 28 Mar.74 at 1045 hours, a flre and explosion occurred in Bldg 8582, ;: oom
B, S6lid Prdpejlant M~iling and Cutting Facility.
2. Two operators were present;'MU1gt Louis A.. Franks and Mr. Kelley N. Palmer.
No injuries occurred.
3. The incident occurred while remotely cutting an eight pound piece of TP-
H819 propel] 4nt (about X 7," X 4") into one-half inch slabs with a band saw.
MSgt Franks loticed a ian'ie near the band saw table in the region of the saw
blade. After ne had stepped back from the protective window, an explosion
occurred. The TP-H8219 specimens being cut at the AF RPL were relatively
new samples that were entering an aging program. This propellant c'ontains
ultrafine ammonium perchlorate (20%6), iron oxide (1%), 90 micron ammmonium
perchlorate and 6 micron ammonium perchlorate. A Class II explosive
classification resulted from AFRPL test on compositions similar to TP-H8219.
4. An AFRPL group closely inspected the site on 2 Apr 74. Physical evidence
showed that the block of propellant being cut burned without detonation. The
cenflagration caused substantial but repairable damage to the band saw. A cutting
exhaust duct,4 inches I. D. with 0. 125 inch walls connected to the band saw with a
t-wo-inch flexible line, e:ploded scattering large metal fragments throughout the
cell. Another more or less simultaneous explosion occurred under a vacuum
holding plate on an adjacent milling machine blowing the vacuum plate against the
ceiling. The milling machine was also in repairable condition after the incident.
7he cutting cell door was blown off and the door of an adjacent cell pulled off,
with damage to lower hinges.
5. Damage was sustained by the band saw, milling machine, exhaust duct, a
small vacuum pump, two doors and electrical wiring. Estimated cost of damage
4 wva s:
TOTAL $5,140.00
6. The incident was probably initiated with a fire caused by friction between the
saw blade and the propellant. An examination of a piece of propellant that had
been previously cut cff the block that was involved !n the incident showed that
extensive deformation and smearing of the aluminum particles had occurred. Thus,
galling between the large aluminum particles (90 micron) and the saw blade could
have created sufficient local heating to cause ignition. Burning particles from
22 i:
the burning propellant were swept into the cutting exhaust duct igniting an
accumulation of finely divided propellant in an approximately ten-foot horizontal
duct section. The propellant particles in the duct exploded. By an undetermined
process,a spark also ignited finely divided propellant powder accumulated in a
cavity under a vacuum holding plate on the milling machine bed. The ensuing
explosion ripped the vacuum holding plate off the machine.
a. Replace the band saw with a large circle saw. This was suggested
because Mhe band saw is a more complex device that is difficult to clean and has
a large number of places where entrained propellant particles can be subjected to
pinching and friction. Particularly, particle entrapment between the driving
wheels and the saw blade appeared to be an ignition hazard.
b. Use a tungsten carbide tipped saw blade. Gallinxg between large aluminum
part-cles (90 micron) in the propellant and a slightly dulled saw blade appeared a
probable Lgnition source for this incident. Use of tungsten carbide cutters, which
are not readily dulled from cutting aluminum,could reduce the amount of local
heating during cutting. Cutting speed did not stand out as a factor ir. this incident
but should be controlled to less than 1000 feet 'per minute.
c. Design the particle exhaust system so that the inlet at the cutter is not
reduced to less than fifty percent of area of the primary exhaust duct. This
design feature will keep the air velocity and mass flow in the exhaust duct maxi-
accumulating in the
mized. Such conditions should aid in keeping particles from duct
I. D. terminating at
duct. The system before this incident used a four inch
the cutter with a two inch I. D. flexible hose.
d. Minimize horizontal exha'st duct sections to less than two feet and
eliminate dead air spaces in connections where particulate material could accumu-
late . An explosion occurred in a long horizontal duct section where propellant
dust from the cutting operation had settled out. If the exhaust duct was constructed
so that it rose at a steep angle to a high point and then fell at a sharp angle to the
dust collector, buildup of particulate in the duct would be lessened. Also, the
duct in use has horizontal connections for accessory equipment with dead air
spaces about one foot long at right angles to the duct flow between the duct and
shut off valves. Such dead air zones that would be efficient particle collectorb
should be eliminated.
e. Flush cutting exhaust duct with high pressure nitrogen each day following
cutting oaerations. By flushing higE/pressure nitrogen through smnall lines
installed in the rising portion of the exhaust duct after each day of cutting operation,
dangerous buildup of fine propellant particles would be avoded. Direct observation
of the duct interior for inspection would be desirable.
in the cell when the duct exploded. Lightweight construction should not impair
operation of the duct and would lessen damage to surrounding equipment due to
impact of heavy metal fragments.
"V.
Ire
Z4I
APPENDIX III
Time Propellant
Point Typo
#1 77'F/90% RH 5
#2 135°F/Z0% RH 5
#3 135°F/30% RH 6
I#4 135°F/50% RH 5
#6 170 0 F/Arnbient 3
i TI H ~ 3, 4, andone
Rem-ove 6. half-block
Cut and mark< Environmental
fromas usual. Chambers 1, 2,
251
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Time propellauit
44
26
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APPENDIX IV
POLYMERS
CURING AGENTS
PLASTICIZERS
FlOronite
IDP
Stan-Pete
isodecyl pelargonate
a polybutene
a hydrocarbon oil
BA benzllic acid
Cr Cl., chromium trichlorlde
28
BONDING AGENTS
STABILIZERS
DT 11 d itert iarybutyl hydroquinone
OXIDIZERS
AP ammonium perchlorate
B-MX cyclotetramethiylenietetranitramine
F UEL
AlI alumi-inumn
29 1