ASTM D2541-93
(Test Method)Standard Test Method for Critical Diameter and Detonation Velocity of Liquid Monopropellants
Standard Test Method for Critical Diameter and Detonation Velocity of Liquid Monopropellants
SCOPE
1.1 This test method covers the evaluation of two properties of a high-energy liquid propellant. In one form, the critical internal diameter is determined in a given type of metal or plastic tubing below which propagation of stable high-velocity detonation will not take place. In the alternative form, which uses more material, detonation rate is concurrently measured. The composite donor of either size may be used in most instances to initiate detonation in experimental trap designs.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
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Designation: D 2541 – 93
Standard Test Method for
Critical Diameter and Detonation Velocity of Liquid
Monopropellants
This standard is issued under the fixed designation D 2541; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope not necessarily imply that the same results would be obtained
in an aluminum, copper, glass, etc., tube of similar dimensions.
1.1 This test method covers the evaluation of two proper-
Type 347 stainless steel tube is acceptable for a standard
ties of a high-energy liquid propellant. In one form, the critical
reference test, but for practical application, diameters should be
internal diameter is determined in a given type of metal or
studied in the materials and wall thicknesses proposed for use.
plastic tubing below which propagation of stable high-velocity
4.2 When working with high-energy liquid propellants,
detonation will not take place. In the alternative form, which
serious consideration shall be given to the possibility that a
uses more material, detonation rate is concurrently measured.
detonation originating in the engine can propagate upstream to
The composite donor of either size may be used in most
the propellant tank and cause a disastrous explosion. Therefore,
instances to initiate detonation in experimental trap designs.
it is useful to know the minimum diameter of propellant line
1.2 This standard does not purport to address all of the
through which a detonation of the propellant in question can
safety problems, if any, associated with its use. It is the
propagate. If it is impracticable to use propellant lines smaller
responsibility of the user of this standard to establish appro-
than this minimum, it will be necessary to design and test
priate safety and health practices and determine the applica-
detonation traps in larger lines. The minimum or critical
bility of regulatory limitations prior to use.
diameter (often referred to as “failure” diameter), when the
1.3 The values stated in SI units are to be regarded as the
conditions are properly defined, can be a useful measure of the
standard. The values given in parentheses are for information
shock sensitivity of similar systems. The detonation velocity of
only.
the propellant in question is another property of interest.
2. Terminology 4.3 The three determinations, namely: minimum diameter
for propagation, detonation trap requirements, and detonation
2.1 Definition:
velocity, have much in common; all presuppose the initiation
2.1.1 critical diameter—the largest diameter that will not
of a stable detonation in a liquid contained in a tube. The key
detonate when the donor is exploded.
to the present test method is the use of a donor stage consisting
3. Summary of Test Method
of the material under test. Although a compound initiator
comprised of a blasting cap and high-explosive booster is
3.1 Various diameters of tubing are filled with propellant,
employed, the true donor is a length of the subject material
and an attempt is made to cause the propellant to detonate by
sufficient to assure establishment of a stable detonation char-
use of a secondary detonating medium (the donor).
acteristic of the test medium ahead of the first test section or
4. Significance and Use
measuring station. Questions of wall and boundary discontinu-
ity are thereby eliminated along with the accompanying
4.1 It should be emphasized that the critical diameter, as
complications of impedance mismatch and perturbation of the
determined under these conditions, is valid only for these
shock front.
conditions and is not an intrinsic property of the sample. One
vital parameter in establishing the critical diameter is that of
5. Apparatus
confinement of the test specimen. The fact that detonation
5.1 The liquid under test, depending on what measurement
occurs or does not occur in Type 347 stainless steel tube does
or measurements are to be made, shall be contained in one of
the following three assembled units:
This test method is under the jurisdiction of ASTM Committee F-7 on
5.1.1 Assembly No. 1, Critical Diameter Measurement (Fig.
Aerospace Industry Methods and is the direct responsibility of Subcommittee
1 (a)):
F07.02 on Propellant Technology.
Current edition approved March 15, 1993. Published May 1993. Orginally
5.1.1.1 Section A, Fig. 1 (a), shall consist of Type 347
published as D 2541 – 66 T. Last previous edition D 2541 – 83.
stainless steel tubing (1-in. (254-mm) outside diameter by
This test method is identical in substance with the JANNAF method,“ Critical
0.049-in. (1.24-mm) wall thickness by 6-in. (152-mm) length).
Diameter and Detonation Velocity Test,” Test Number 8, Liquid Propellant Test
Methods, May 1964, published by the Chemical Propulsion Information Agency, When filled with test sample, it is considered the “self donor”
Johns Hopkins University, Applied Physics Laboratory, Johns Hopkins Rd., Laurel,
section.
MD 20707.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 2541
FIG. 1 Diagram of Apparatus
5.1.1.2 Section C, Fig. 1 (a), shall consist of Type 347 cement or passed through neoprene sleeves, provided either is
stainless steel tubing (30-in. (762-mm) length) of any one of compatible with the test liquid.
the following sizes: (a) T-1 targets are pressure-shorting switches encased in a
copper tube ⁄4 in. (6.4 mm) in diameter by 1 in. (25.4 mm)
Outside Diameter, Wall Thickness,
in. (mm) in. (mm)
long. These switches are inserted through holes in the side of
1 (25.4) 0.049 (1.24)
the container. (The same item in an aluminum case bears the
⁄4 (19.0) 0.049 (1.24)
⁄8 (15.9) 0.035 (0.89) designation T-2 target.)
⁄2 (12.7) 0.035 (0.89)
5.1.2.2 The downstream end of Section D is closed by
⁄8 (9.5) 0.035 (0.89)
crimping or plugging.
⁄4 (6.4) 0.035 (0.89)
⁄8 (3.2) 0.020 (0.51)
5.1.2.3 A longer container and more distance between
stations, or a greater number of stations is required if greater
When filled it is considered the “test” section.
accuracy in rate measurement is required.
5.1.1.3 Section A and Section C is connected by means of a
5.1.2.4 If the test sample is limited, smaller diameters can be
stopper of rubber or other suitable material compatible with the
used.
propellant under test. The top of Section C is flush with the top
5.1.3 Assembly No. 3, Combination Critical Diameter and
of the stopper.
Detonation Velocity Measurement (Fig. 1(c)):
5.1.1.4 The downstream end of Section C is closed by
5.1.3.1 Section B, or “self donor” section, Fig. 1(c) (see
crimping, plugging, or clamping, the latter being shown in Fig.
5.1.2.1).
1(a) and (c). A pinch clamp over vinyl tubing shall be used in
5.1.3.2 Section C, or “test” section, Fig. 1(c) (see 5.1.1.2).
freeing the container, especially one of small diameter, of
5.1.3.3 Section C, connection to Section B (see 5.1.1.3).
entrapped air during the filling operation.
5.1.3.4 Section C, closure at bottom (see 5.1.1.4).
5.1.2 Assembly No. 2, Detonation Velocity Measurement
(Fig. 1 (b)): 5.1.3.5 Additional timing stations can be positioned along
the length of Section C if rates are desired in small-diameter
5.1.2.1 Section D or “test” section, Fig. 1 (b), shall consist
of Type 347 stainless steel tubing (1-in. (25.4-mm) outside tubes.
diameter by 0.049-in. (1.24-mm) wall thickness by 11-in. 5.1.3.6 The apparatus as described is suitable for determin-
(279-mm) length). Two timing stations of either ionization ing critical diameters up to 1 in. (25.4 mm) (the donor itself
wires or T-1 targets (Note 1), 100 mm apart, and located at acts as the 1-in. section), but if the minimum diameter for
approximately 5 and 9-in. (127 and 229-mm) levels from the propagation is greater than 1 in., a larger donor shall be used.
booster end, shall be used for the rate measurements. The This donor should be 1 ⁄2 or 2 in. (38.1 or 50.8 mm) in
probes inserted in the container can be sealed with epoxy diameter, as necessary, but otherwise of the same length and
D 2541
wall thickness (0.049 in.) (1.24 mm) as the standard donor. The all-cotton clothing and special conductive shoes.
diameter of the high-explosive booster and detonator holder
5.1.7 Rate-Measurement Apparatus—A 10-MHz counter, or
shall be scaled up to match, and the constant L/D of 2 shall be
an oscilloscope (with suitable camera attachment) with a
maintained. For instance, if the donor is 2 in. in diameter, the
5-μs/cm sweep frequency, can be used to measure the time of
booster will be at least 2 in. in diameter by 4 in. (102 mm) long.
propagation between the stations (Note 1). The oscilloscope
5.1.4 Assembly No. 4, Trap Testing—In testing detonation
has an advantage in that the trace can give some evidence as to
traps, the trap to be tested is attached to either Assembly No. 1
the cause of malfunctions when they occur.
or 3 in place of the small-size tubing being tested for critical
NOTE 1—It can be desirable to use more than two stations or probes,
diameter (Section C). Certain configurations can require filling
thus obtaining replicate rate measurements. A circuit diagram for single-
with liquid before assembly with the donor section. In this
oscilloscope rate measurements is given in Fig. 2.
event, the precautions under Section 6 shall be observed.
5.1.7.1 Time-Interval or Counter-Chronograph
5.1.5 Booster—The booster charge shall consist of a cylin-
Apparatus—The instrument shall be a 10-MHz counter-
drical pentolite pellet (or equivalent high oxidizers), nominally
1 chronograph (0.1 μs time base) with a resolution of 0.1 μs in
2 ⁄2 in. (64 mm) long by 1 in. (25.4 mm) in diameter, weighing
the range from 0.3 μs to 1 s. The unit shall have an input
51 6 0.3 g with a density of 1.65 6 0.01 g/cm , and containing
1 1 sensitivity of 0.2 V rms. The input impedance shall be 1 MV,
an axial cavity ⁄4 in. (6.4 mm) in diameter by ⁄2 in. (12.7 mm)
direct or a-c coupled, trigger slopes either positive or negative.
deep for insertion of the electric detonator.
Step attenuators shall provide trigger voltage adjustment hav-
5.1.5.1 Warning—Pentolite is not considered to be a par-
ing a range of 61, 610, and 6100 V.
ticularly sensitive explosive, but handle with due respect.
5.1.7.2 Counter-Chronograph Input Circuitry—Counter-
Careless or rough handling can be fatal. Remembered, too, that
chronographs currently in use require input voltage pulses with
practically all high explosives are quite toxic. Handle them
relatively fast rise times and moderate amplitudes. Both of
with particular care to avoid spreading the material by contact
these conditions can be met with the simple R-C circuit
of the hands with other parts of the body. Wash hands with soap
described in two forms in Figs. 3 and 4. Since most counter-
and water frequently. Working garments shall be free from
chronographs permit polarity and slope selection of the trig-
dust-collecting features such as trouser-cuffs, and laundered
gering pulses, it is convenient and frequently desirable to
frequently.
provide maximum pulse isolation by using opposite polarities
5.1.6 Detonator—Detonation in the booster pellet shall be
for “start” and “stop” triggering pulses from adjacent probes.
initiated by an electric blasting cap which fits snugly into the
The circuits shown schematically in Figs. 3 and 4 were
hole in the booster. The cap used with the pentolite booster
designed to provide output pulses of opposite polarity when the
shall be a No. 8 commercial cap.
inputs are “shorted” through ionization probes or T-1 targets.
5.1.6.1 Warning—Electric blasting caps contain primary
With the supply voltage polarities as shown, the output pulse at
explosives, which are easily initiated by relatively mild physi-
J is negative when J is shorted, while the output pulse at J is
cal shock. Consequently, every precaution shall be taken by
3 1 4
positive when J is shorted.
those who work with them, with particular emphasis on gentle
handling and protection from electrostatic charges. Accumula- 5.1.7.3 Oscillograph Circuitry—The circuit for the oscillo-
tion of static charges by personnel shall be prevented by use of graph is shown in Fig. 5 and the circuit for the power supply is
All resistors 6 10 percent, 1 W
R —2000 V
R —50 V
R —1 MV
C —3000 pf, 610 percent, 600 V, dc (C may be changed to lengthen or shorten the pulse width)
1 1
C —0.05μ F, 620 percent, 600 V, dc
D—1N34 crystal diode
B—battery 25 to 50 V, dc
S —trigger station
S ,S ,S ,S —rate-measuring stations
1 2 3 4
FIG. 2 Four Channel Mixer Circuit Producing Four Positive Pulses
D 2541
6.2 Before each shot, the firing circuit shall be tested for
continuity with a blasting galvanometer. The shot can be
conveniently fired from the remote control point by means of
a portable blasting machine. The firing line shall consist of
16-gage (1.29-mm) or heavier duplex copper conductor cable.
6.3 It is recommended that the firing line and all instrument
lines have a positive disconnect at the firing position. The
safest practice is to provide an ungrounded shunt block for
FIG. 3 Bacis R-C Pulse-Forming Circuit
each of the lines, best located in a box with a hinged cover and
equipped with a lock. Routine inspection of all lines that are
subject to physical damage by fragments or abrasion due to
blasting shall be made and the lines replaced rather than
repaired by splicing and taping. The shunts are removed and
the connections made in the instrument and firing lines after the
blast area is cleared and secured just prior to firing the shot.
7. Preparation of Apparatus
FIG. 4 Practical 2-Channel R-C Pulse-Forming Circuit
7.1 Since the density of liquids varies with temperature, and
Producing a Positive Pulse in One Channel and a Negative Pulse
detonation velocity varies with density, it will be necessary,
in the Other Channel
when determining detonation velocity, to measure and control
the temperature.
shown in Fig. 6. With this apparatus, it is necessary to
NOTE 2—For example, the velocity of nitromethane varies about 3.7
synchronize the circuit, and for this a twisted wire (No. 32 B &
m/s·°C over the range from −20 to 70°C.
S gage (0.202-mm) enameled copper wire is satisfactory) shall
7.2 In the determination of critical diameter, temperature
be inserted between the pentolite donor and the acceptor.
5.1.8 Firing Chamber—It is necessary to provide protection will affect the result since the shock sensitivity generally
increases
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