Spacecraft
Fire Safety
Fire Signatures and Detection
Modern spacecraft
are equipped with smoke detectors that respond to
smoke particles in the air. The Shuttles
and the Russian modules of the International Space
Station (ISS) use ionization-based detectors that
are similar, in concept, to those commonly found
in homes and offices. An alternative type of particulate
detector, which is photoelectric-based, is used on
the U.S. modules of the ISS. Quite naturally, this
inconsistent design approach raises the questions:
Which type
of detector is best for spacecraft? Can we develop
better detectors based on our knowledge of
smoke generated in microgravity?
Answers to these
and other questions are starting to emerge. A recent
study -- the Comparative Soot
Diagnostics experiment -- showed that the ionization
detectors used in the Space Shuttles performed
less well in space than in normal gravity. And
the photoelectric
smoke detectors on the ISS are sensitive to dust,
which produces disruptive false alarms. Clearly,
better sensors are needed and researchers in the
FPDS program at NASA GRC are responding to these
findings by developing advanced sensors for combustion
particles and gases and exploring how to couple
particulate and gas sensors to provide a more comprehensive,
effective suite of sensors.
Fire Signatures
 |
| An
artist's rendering of The Smoke Aerosol Measurement
Experiment (SAME) in the Microgravity Science
Glovebox. SAME will quantify prefire signatures
in low gravity and evaluate detection technologies. |
Fire detection technology is based on measuring a
unique characteristic of a fire, such as temperature
rise, smoke particles, combustion gases, pressure
changes, and UV radiation. What causes a sensor
to respond to a fire can be thought of as the signature
of that fire. Research is being conducted within
the FPDS program to identify and quantify fire
and pre-fire signatures in order to create a database
that can guide the development of improved fire
detectors.
One of the
biggest challenges facing researchers is that many
fire signatures are different in the
reduced gravity of space than in Earth’s gravity.
Consequently, researchers must identify normal gravity
signatures, conduct ground-based microgravity tests
to quantify differences, develop a ground-based process
for accurately predicting fire signatures in space,
and then assess the accuracy of the process by testing
combustible materials in space.
Sensor Technology Development
Significant advances in sensor technology have occurred
during the last decade, including the miniaturization
of sensors, reduced power requirements, development
of wi-fi interfaces, and improved sensitivity.
Technologies that are being developed and evaluated
include micro-electromechanical gas and particulate
sensors and advanced electronic nose sensors. Spacecraft
and space habitat designers can dramatically improve
the health and safety of astronauts by incorporating
into their designs this new technology and the
promising technology developed in the FPDS program.
Movement of Smoke and Contaminants in a Spacecraft
The effectiveness of any fire detector is compromised
unless it is located in the right place. If a network
of sensors is used, designers need to determine
the optimum number and placement of sensors to
provide adequate protection. For designers to make
intelligent decisions, researchers must develop
computer models of how smoke, gases, and other
contaminants move within a spacecraft in order
to accurately evaluate a network of fire detectors.
Products
The fire signatures and detection element of the
FPDS program will yield several significant products:
-
Advanced
sensors for spacecraft and space environments
-
A data bank of fire signatures
-
Smoke and contaminant transport models
and Accessibility Certification