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NASA NTRS2023

High-Pressure, Normal-Gravity Droplet Combustion Experimental Hardware

The High-Pressure, Trans-Critical (HPTC) 1-g Liquid Droplet Combustion Experiments will assess the autoignition and combustion of liquid fuel droplets at elevated temperatures and pressures. These experiments are being conducted at the NASA Glenn Research Center in a manner similar to experiments performed in Glenn’s Zero Gravity Research Facility (ZGF) using the B drop vehicle. The modification to the test capabilities of the ZGF experiments in the new experimental configuration will allow researchers to continue performing normal-gravity liquid droplet combustion experiments without requiring the use of the ZGF test equipment. These normal-gravity experiments will be conducted at lower pressures than in the ZGF because the pressure vessel for this setup is limited to a maximum working pressure of 7.74 atm (99.1 psig) at 366.5 K (200 °F). This experimental configuration will enable development of a similar capability for conducting high-pressure combustion and supercritical oxidation research on the International Space Station. Experiments will be conducted with the capability of altering the ambient pressure, temperature, and gas concentrations, as well as the fuel type for each test. For these experiments, the test vessel operates at pressures up to 7.5 atm (95.5 psig), temperatures up to 1,073 K (1,472 °F) inside the insulated oven, and oxygen concentrations up to 30 percent.

Droplet Combustion↗

NASA NTRSDate not supplied

Fire Safety Implications of Preliminary Results from Saffire IV and V Experiments on Large Scale Spacecraft Fires

The spread and growth of flames over large solid fuel samples and their effect on the pressurized spacecraft were studied inside the Cygnus spacecraft while in orbit after departing the International Space Station. These experiments were developed by NASA’s Advanced Exploration Systems Division in the Human Exploration and Operations Mission Directorate. The ignited materials consisted of poly-methyl methacrylate (PMMA), cotton fabric and a cotton/fiberglass fabric blend. The samples were all 40 cm wide and with various lengths ranging from 18 cm for the PMMA samples to 50 cm for the fabrics. The overall results from these tests and their impact on the spacecraft are presented with emphasis on the fire safety implications of the results. The experiments included, a post-fire cleanup system, vehicle internal volume measurements, and transport of acid gases (HCl and HF). Measurements included video images, flame spread rate, flame temperatures and radiant heat output; energy release through oxygen calorimetry; distributed measurements of CO2 concentration and temperature at six locations in the spacecraft; CO2, CO, O2, HF and HCl concentrations; vehicle pressurized volume; and aerosol concentrations. Details of the flame growth and spread are discussed in other papers as are details of the post-fire cleanup system performance. The fire events had a measurable impact on the vehicle pressure, temperature, and carbon dioxide concentration. However, despite having heat release rates up to 10 kW, the average vehicle conditions did not rise to unacceptable levels. The combined results of the experiments provide significant new understanding of the impact of sample and flow duct height on flame spread and growth in addition to an improved perspective of the impact of a fire event on a spacecraft.

micorgravity↗

NASA NTRSDate not supplied

Fire Safety Implications of Preliminary Results from Saffire IV and V Experiments on Large Scale Spacecraft Fires

The spread and growth of flames over large solid fuel samples and their effect on the pressurized spacecraft were studied inside the Cygnus spacecraft while in orbit after departing the International Space Station. These experiments were developed by NASA’s Advanced Exploration Systems Division in the Human Exploration and Operations Mission Directorate. The ignited materials consisted of poly-methyl methacrylate (PMMA), cotton fabric and a cotton/fiberglass fabric blend. The samples were all 40 cm wide and with various lengths ranging from 18 cm for the PMMA samples to 50 cm for the fabrics. The overall results from these tests and their impact on the spacecraft are presented with emphasis on the fire safety implications of the results. The experiments included, a post-fire cleanup system, vehicle internal volume measurements, and transport of acid gases (HCl and HF). Measurements included video images, flame spread rate, flame temperatures and radiant heat output; energy release through oxygen calorimetry; distributed measurements of CO2 concentration and temperature at six locations in the spacecraft; CO2, CO, O2, HF and HCl concentrations; vehicle pressurized volume; and aerosol concentrations. Details of the flame growth and spread are discussed in other papers as are details of the post-fire cleanup system performance. The fire events had a measurable impact on the vehicle pressure, temperature, and carbon dioxide concentration. However, despite having heat release rates up to 10 kW, the average vehicle conditions did not rise to unacceptable levels. The combined results of the experiments provide significant new understanding of the impact of sample and flow duct height on flame spread and growth in addition to an improved perspective of the impact of a fire event on a spacecraft.

microgravity fire safety↗

NASA NTRSDate not supplied

Fire on the Moon: Solid Fuel Combustion Experiments

As NASA plans to return people to the Moon for extended durations, we present an experiment concept to understand fire and material flammability there. A small combustion chamber would be used to conduct the first-ever combustion tests on another world. Multiple fuel samples are to be individually burned in Lunar gravity, with cameras and other sensors recording flame characteristics. The main hypothesis is that some materials burning in Lunar-g are more flammable than on Earth. The reason is that buoyant flow has two counteracting effects on material flammability. Increasing gravity level permits more fresh oxygen to be supplied to the flame, but if the buoyant speed is too high, combustion chemistry and increased cooling hinder combustion. This has important implications for the current 1-g material screening method used by NASA. Oxygen limits for upward and downward spread on the Moon will be compared to 1-g values. Earth-based partial gravity facilities (drop towers, aircraft, and sounding rockets) will be used to refine the experiment and provide some limited-duration data. Measured flame characteristics in 1-g and Lunar-g will be compared to a detailed model. These will refine pressure-gravity scaling relations that will then be applied to other g-levels. The work directly addresses knowledge gaps in flammability and crew safety as defined in several NASA strategic documents.

Fire↗

NASA NTRSDate not supplied

Preliminary Results from the Saffire VI Experiment

Preliminary results are presented for one test of the last flight of the Spacecraft Fire Experiment (Saffire VI) which was conducted on an orbiting Cygnus spacecraft. These experiments directly address the risks associated with our understanding of spacecraft fire behavior at practical length scales and geometries. The lack of this experimental data has forced spacecraft designers to base their designs and safety precautions on 1-g understanding of flame spread, flame self-extinguishment, fire detection, and suppression. The Saffire experiment was developed by an international team of investigators with the goal of addressing open issues in spacecraft fire safety. NASA’s Spacecraft Fire Safety Demonstration Project was formulated with the goal of conducting a series of large-scale experiments in spacecraft environments that represent practical spacecraft fires. These tests spanned 1.5 to 3.2 kW with free air volumes of 17 to 19 cubic meters. The final flight in the series of six experiments examined concurrent spread over large samples (all 41 cm wide) including a thin sheet of flammable fuel (cotton/fiberglass 50 cm long); 2-sided spread over 1 cm thick polymethyl methacrylate (PMMA) (18 cm long); 1-sided spread over 0.5 cm thick (18 cm long); and Nomex fabric (7 cm long). Results are presented for the PMMA samples, the SIBAL sample, and the thin cotton samples from Saffire IV and V. The flame heat release is determined and compared to the overall temperature rise in the spacecraft and the change in the concentration of carbon dioxide and carbon monoxide in the spacecraft. Overall, the temperature and pressure rise in the spacecraft were found to be less significant than the increase in carbon dioxide and carbon monoxide.

fire↗

NASA NTRSDate not supplied

Preliminary Results from the Saffire VI Experiment

The preliminary results are presented for one test of the last flight of the Spacecraft Fire Experiment (Saffire VI) which was conducted on an orbiting Cygnus spacecraft. These experiments directly address the risks associated with our understanding of spacecraft fire behavior at practical length scales and geometries. The lack of this experimental data has forced spacecraft designers to base their designs and safety precautions on 1-g understanding of flame spread, flame self-extinguishment, fire detection, and suppression. The Saffire experiment was developed by an international team of investigators with the goal of addressing open issues in spacecraft fire safety. NASA’s Spacecraft Fire Safety Demonstration Project was designed with the goal of conducting a series of large-scale experiments in spacecraft environments that represent practical spacecraft fires. The final flight examined concurrent spread over large samples (all 41 cm wide) including a thin sheet of flammable fuel (cotton/fiberglass 50 cm long); 2-sided spread over 1 cm thick polymethyl methacrylate (PMMA) (18 cm long) ; 1-sided spread over 0.5 cm thick (18 cm long); and Nomex fabric (7 cm long). This paper focusses on the two-sided PMMA sample. The flame heat release is determined and is compared to the overall temperature rise in the spacecraft and the change in the concentration of carbon dioxide and carbon monoxide in the spacecraft.

fire↗