From Wikipedia, the free encyclopedia
A type of quick release fastener
A
pyrotechnic fastener
(also called an
explosive bolt
, or
pyro
, within context) is a
fastener
, usually a nut or bolt, that incorporates a
pyrotechnic charge
that can be initiated remotely. One or more explosive charges embedded within the bolt are typically activated by an
electric
current, and the charge breaks the bolt into two or more pieces. The bolt is typically scored around its
circumference
at the point(s) where the severance should occur.
[1]
Such bolts are often used in space applications to ensure separation between rocket stages, because they are lighter and much more reliable than mechanical
latches
.
In applications that require safety, precision and reliability, such as the aerospace industry,
[2]
pyrotechnic fasteners are triggered using
exploding bridgewire detonators
, which were themselves later succeeded by
slapper detonators
.
[
citation needed
]
Classical
blasting caps
are generally avoided for such usage.
More recent developments have used pulsed
laser diodes
to detonate
initiators
through
fiber-optic cables
,
[3]
which subsequently fire the main charge.
Gas generators
are similar to pyrotechnic fasteners. They are used to generate large amounts of gas, as for turbopumps, to inflate balloons, especially airbags, to eject parachutes and similar applications.
Compositions used
[
edit
]
Various pyrotechnic compositions can be used, depending on the desired burn rate and required amount of energy and volume of gas produced. Some materials, such as
RDX
,
sublime
in vacuum, which limits their usefulness in aerospace applications.
[4]
Composition with the character of
bipropellants
and
flash powders
are often used.
[
citation needed
]
Standard pyrotechnic mixtures used by NASA
[
edit
]
- Manganese
/
barium chromate
/
lead chromate
: Time-delay mix, used for sequencing. Gasless burning.
[5]
- RDX
/
nitrocellulose
: Gas generator, unsuitable for deep space missions, burn rate dependent on pressure.
[5]
- Boron
/
potassium nitrate
: Gas generator and rocket-motor igniter, thermally stable, stable in vacuum, burn rate independent of pressure.
[5]
- Zirconium
/
potassium perchlorate
: Used in the
NASA Standard Initiator
(NSI).
[6]
Rapid pressure rise, little gas but emits hot particles, thermally stable, vacuum stable, long shelf life. Sensitive to static electricity. Known to cause circuit damage during ground testing.
[5]
- Lead azide
: Used as a
primary explosive
.
[7]
: 38
Sensitive to impact, friction, and static electricity. Thermally and vacuum stable, if
dextrin
is not used for desensitizing. Long shelf life.
[5]
- Hexanitrostilbene
: Used in detonators, linear
shaped charges
, and bulk explosives. Insensitive to stimuli other than explosion. Thermally stable. Vacuum stable.
[5]
Used in deep space applications where
RDX
can not be utilized, such as aboard the
Apollo Lunar Module
[7]
: 23
Detonates at 22,000 feet per second (6,700 m/s).
[5]
See also
[
edit
]
References
[
edit
]
- ^
U.S. Army Material Command Pamphlet 706-179 - 'Explosive Trains'
(PDF)
. U.S. Army. 9 March 1965. p. 108.
Archived
(PDF)
from the original on 19 August 2022.
- ^
"AIAA 96-2874 Development and Qualification Testing of the High Voltage Detonator"
.
- ^
"Laser Motor Igniter"
. Retrieved
12 September
2022
.
- ^
Ewing, Robert G.; Waltman, Melanie J.; Atkinson, David A.; Grate, Jay W.; Hotchkiss, Peter J. (1 January 2013).
"The vapor pressures of explosives"
.
Trends in Analytical Chemistry
.
42
: 35?48.
doi
:
10.1016/j.trac.2012.09.010
. Retrieved
19 August
2022
.
- ^
a
b
c
d
e
f
g
Bement, Laurence J.; Schimmel, Morry L. (1 June 1995).
A Manual for Pyrotechnic Design, Development and Qualification
. Hampton, Virginia: NASA, Langley Research Center. pp. 14?16.
Archived
from the original on 22 May 2011.
- ^
Hohmann, Carl; Tipton, Bill Jr.; Dutton, Maureen (1 October 2000).
Propellant for the NASA Standard Initiator
(PDF)
. Houston: NASA, Johnson Space Center. p. 1.
Archived
(PDF)
from the original on 11 April 2022.
- ^
a
b
Falbo, Mario J.; Robinson, Robert L. (1 March 1973).
NASA Technical Note D-7141 - Apollo Experience Report: Spacecraft Pyrotechnic Systems
(PDF)
. NASA, Lyndon B. Johnson Space Center, Houston.
Archived
(PDF)
from the original on 12 December 2020.
External links
[
edit
]