Experiments / Saffire flow duct
Saffire-IA spacecraft fire-safety study
Spacecraft Fire Safety Experiment - I
Lit a metre-long sheet of cotton-fiberglass fabric inside an uncrewed Cygnus cargo ship to see how a large fire grows in low gravity.
What burned
Solid materials
Cotton fabric
Where
In a cargo ship
After it left the space station, with no crew aboard
How much data
2 tests
Each one is a row in NASA's table
What they changed between tests
- flow direction
What it found
- 1 of 2
Saffire exists because fire standards derived on Earth carry unknown risk when applied to spacecraft.
NASA's words
“the use of terrestrial fires and fire standards to design spacecraft fire safety systems presents an inherent risk to the vehicle because of the significant level of uncertainty” PSI record
- 2 of 2
It is the only way to study a realistically large fire, because that cannot be done safely with crew aboard.
NASA's words
“provides a new way to study a realistic fire on an exploration vehicle, which has not been possible in the past because the risks are too high” PSI record
Summarized by the SI. Each summary is tied to a quotation that the build checks against NASA's text. A matching quote is not a scientific review.
What it helps with
Stopping a fire from starting
Which materials burn, and in what air
A main aim
Noticing a fire early
What smoke looks like to a detector
Touches on it
Putting a fire out
What makes a flame go out
Not an aim
For researchers: NASA's full recordThe conditions tested, every row of the table, NASA's description, publications and hardware
Shared hardware: A large flow duct flown in an uncrewed cargo ship after it left the station, so that a big fire could be lit safely. Experiments that shared hardware share its limits, so their results can be compared directly.
Why it counts as fire-safety research
“Flammability studies focus on solid materials such as fabrics and plastics, as studied in the Burning and Suppression of Solids (BASS and BASS-II) and Spacecraft Fire Safety Demonstration (Saffire-I, -II, and -III) investigations.” NASA challenge statement
NASA's words behind each rating
- Prevention3 of 3
“investigate the low-g flammability limits compared to those obtained in NASA’s normal”
- Detection1 of 3
“Instruments on an unmanned cargo vessel measure oxygen, carbon dioxide, heat, pressure and flame growth”
- Suppression0 of 3
Not an aim of this investigation.
Conditions covered
- Oxygen in the atmosphere
- 21.5% to 21.7%
- airMoon
- Pressure
- 102 kPa to 103 kPa
- Moonsea level
- Flow speed
- 20 cm/s
- Itemized rows
- 2
- 2 tests
Fuels and materials
SIBAL fabric (cotton/fiberglass) (2)
Measurements named in the PSI record
- Flame imaging
- Radiometry
- Thermocouples
- Gas analysis
- Flow velocity
How the tests differ, and how they are the same
Worked out from the 2 rows of the PSI table. A variable that is not listed was not reported, which is different from being held fixed.
Changed from test to test
- Oxygen
- 21.5% to 21.7%
- Pressure
- 102 kPa to 103 kPa
- Flow direction
- 2 different values
- Burn time
- 70 s to 420 s
- Flame spread rate
- 1.3 mm/s to 1.8 mm/s
- Burn length
- 10 cm to 84 cm
The same in every test
- Oxygen refers to
- ambient
- Flow speed
- 20 cm/s
- Fuel or material
- SIBAL fabric (cotton/fiberglass)
- Fuel phase
- solid
- Geometry
- fabric sheet
- Sample thickness
- 3.7 mm
- Sample length
- 40.6 cm
- Sample width
- 94 cm
- Igniter power
- 182 W
- Ignition time
- 8 s
- Ignited
- yes
Reported for only some rows, with one value: how the test ended, burn length at 1 g.
Rows from the PSI table
Click a row for the source of every value. Filter and export
| Record | Type | Fuel or material | Shape | Oxygen | Pressure | Flow, cm/s | Outcome | Date |
|---|---|---|---|---|---|---|---|---|
| Sample S1 | Test | SIBAL fabric (cotton/fiberglass) | fabric sheet | 21.5% to 21.7% | 102 kPa | 20 | flow terminated | |
| Sample S2 | Test | SIBAL fabric (cotton/fiberglass) | fabric sheet | 21.5% | 103 kPa | 20 |
How the table was read, and what was repaired
Saffire-I - samples
PSI-98_Experimental table_SAFFIRE-1.csv
4 rows in the file, 2 kept as records, 2 left out (Pre-test flow visualization video).
Assumed: Not listed in the PSI table. Taken as the cabin pressure of the Cygnus cargo vehicle.
sha256 c01f29c62455f0a3b512290ab85e5687ecded326733189f002f580368402308d · fetched 2026-11-11
Repairs and warnings
- 2 row(s) are not tests and were left out: Pre-test flow visualization video
- Sample S1, Sample width: the experimental table gives 94 cm; NASA's file NTRS-20170008805.pdf gives 40.6 cm (p. 29, Table I, row 1-1, column Width). The table's value is the one used.
- Sample S1, Sample width: the experimental table gives 94 cm; NASA's file NTRS-20180005168.pdf gives 40.6 cm (p. 30, Table 1, row I-1, column Width). The table's value is the one used.
- Sample S1, Sample thickness: the experimental table gives 3.7 mm; NASA's file NTRS-20170008805.pdf gives 0.37 mm (p. 29, Table I, row 1-1, column Thickness). The table's value is the one used.
- Sample S1, Sample thickness: the experimental table gives 3.7 mm; NASA's file NTRS-20180005168.pdf gives 0.37 mm (p. 30, Table 1, row I-1, column Thickness). The table's value is the one used.
- Sample S1, Sample length: the experimental table gives 40.6 cm; NASA's file NTRS-20170008805.pdf gives 94 cm (p. 29, Table I, row 1-1, column Length). The table's value is the one used.
- Sample S1, Sample length: the experimental table gives 40.6 cm; NASA's file NTRS-20180005168.pdf gives 94 cm (p. 30, Table 1, row I-1, column Length). The table's value is the one used.
- Sample S2, Sample width: the experimental table gives 94 cm; NASA's file NTRS-20170008805.pdf gives 40.6 cm (p. 29, Table I, row 1-2, column Width). The table's value is the one used.
- Sample S2, Sample width: the experimental table gives 94 cm; NASA's file NTRS-20180005168.pdf gives 40.6 cm (p. 30, Table 1, row I-2, column Width). The table's value is the one used.
- Sample S2, Sample thickness: the experimental table gives 3.7 mm; NASA's file NTRS-20170008805.pdf gives 0.37 mm (p. 29, Table I, row 1-2, column Thickness). The table's value is the one used.
- Sample S2, Sample thickness: the experimental table gives 3.7 mm; NASA's file NTRS-20180005168.pdf gives 0.37 mm (p. 30, Table 1, row I-2, column Thickness). The table's value is the one used.
- Sample S2, Sample length: the experimental table gives 40.6 cm; NASA's file NTRS-20170008805.pdf gives 10 cm (p. 29, Table I, row 1-2, column Length). The table's value is the one used.
- Sample S2, Sample length: the experimental table gives 40.6 cm; NASA's file NTRS-20180005168.pdf gives 10 cm (p. 30, Table 1, row I-2, column Length). The table's value is the one used.
NASA's description
Objectives
The objectives of this investigation were to: (1) determine how rapidly a large scale fire grows in low-gravity and (2) investigate the low-g flammability limits compared to those obtained in NASA’s normal gravity material flammability screening test.
Approach
The Saffire-1 experiments was performed on the Orbital Science’s Cygnus resupply vehicle after it deberthed from the ISS. The sample material for Saffire-I is a composite fabric called Sibal consisting of cotton on a fiberglass substrate (75% cotton, 25% fiberglass by weight). It has been used in many space experiments because it burns like cotton but maintains structural integrity after the cotton is consumed. The sample was approximately 0.94 meters long and 0.4 meters wide, simulating a large piece of flammable fabric. The Saffire-1 flight unit had a sample card installed in the middle of a large flow duct. Air is drawn through the flow duct by fans located at the top of the duct with flow straighteners at the bottom of the experiment module. Saffire-I was conducted at an air flow velocity of 20 cm/s. Once the sample was ignited flame images were captured using two cameras. In addition, thermocouples provided flow, flame, and plume temperatures, two radiometers recorded flame radiation, solid state sensors were used to measure pressure, CO2 and O2 mole faction, and two anemometer tracked flow velocity. All data was compressed, and subsequently downlinked.
Hypothesis
This investigation hypothesizes that due to large differences between fire behavior in normal and reduced gravity, the use of terrestrial fires and fire standards to design spacecraft fire safety systems presents an inherent risk to the vehicle because of the significant level of uncertainty. While this approach has been successful thus far, the uncertainty and risk will increase as exploration missions venture further from earth with considerably longer transit times for a safe return. There is a significant lack of microgravity data available for spacecraft designers on which to base their fire safety designs and procedures. To address this knowledge gap, this investigation proposed to conduct large-scale fire safety experiments in an expendable spacecraft without risk to a crew.
Research impacts and Earth benefits
The Saffire-I experiment provides a new way to study a realistic fire on an exploration vehicle, which has not been possible in the past because the risks are too high. Instruments on an unmanned cargo vessel measure oxygen, carbon dioxide, heat, pressure and flame growth, and two video cameras provide views of the flame. Results determine microgravity flammability limits for several spacecraft materials, help to validate NASA’s material selection criteria, and how microgravity and limited oxygen affect flame size. The investigation is crucial for the safety of current and future space missions. Studying fire in small, sealed environments such as the Cygnus cargo supply vehicle benefits fire safety and prevention efforts on Earth, including inside mines, airplanes, or submarines.
Publications
6 listed in PSI, 3 with a DOI.
- The Spacecraft Fire Experiment (Saffire) - Objectives, Development and StatusW Schoren, GA Ruff, DL Urban
- Buoyant Effects on the Flammability of Silicone Samples Planned for the Spacecraft Fire Experiment (Saffire)JE Niehaus, PV Ferkul, SA Gokoglu, GA Ruff
- Flame spread: Effects of microgravity and scaleUrban David L., Ferkul Paul, Olson Sandra, Ruff Gary A., Easton John, T'ien James S., Liao Ya-Ting T., Li Chengyao, Fernandez-Pello Carlos, Torero Jose L., Legros Guillaume, Eigenbrod Christian, Smirnov Nickolay, Fujita Osamu, Rouvreau Sébastien, Toth Balazs, Jomaas Grunde
- Transient flame growth and spread processes over a large solid fabric in concurrent low-speed flows in microgravity – Model versus experimentLi Chengyao, Liao Ya-Ting T., T'ien James S., Urban David L., Ferkul Paul, Olson Sandra, Ruff Gary A., Easton John
- Fire safety in space – beyond flammability testing of small samplesJomaas Grunde, Torero Jose L., Eigenbrod Christian, Niehaus Justin, Olson Sandra L., Ferkul Paul V., Legros Guillaume, Fernandez-Pello A. Carlos, Cowlard Adam J., Rouvreau Sebastien, Smirnov Nickolay, Fujita Osamu, T׳ien James S., Ruff Gary A., Urban David L.
- Operation and Development Status of the Spacecraft Fire Experiments (Saffire)Gary A. Ruff and David L. Urban.
Hardware and raw data
12.3 GB of raw data on PSI: raw data 68, science documents 4, engineering documents 2. FlameLens reads the experimental table, not the raw video or sensor files.
Linked investigations
On Earth
Material flammability standards: Results test whether NASA's material selection criteria hold up, which informs flammability screening generally.
“help to validate NASA’s material selection criteria”