TEST BY FIRE

[Music] [Applause] [Music] the principle consideration in manned spaceflight has been and always will be the safety of the crew no activities will ever knowingly be taken either to save time or money that will imperil the astronauts or jeopardize mission safety in support of this the characteristics of all spacecraft materials particularly those nonmetallic materials selected for the habitable areas in the Apollo command and lunar module are carefully determined through an extensive testing program of major importance in crew Bay materials is their location and flammability characteristics will they burn under what conditions are they self extinguishing can materials be arranged in the spacecraft to prevent a fire from spreading to find the answers and to provide maximum safety for the flight crew many commercially accepted materials are evaluated under the most rigid test conditions general fire control criteria are established and the tested materials are categorized by their functional use and their relative arrangement in the spacecraft category a includes those major materials applications that are unlimited with respect to quantity proximity to ignition sources or exposure to oxygen used in the crew compartment and over wide areas of a spacecraft these materials must be self extinguishing category B includes the many minor materials applications in the spacecraft that are arranged in unrelated locations and exposed to cabin atmosphere there is also category C which includes those materials used in the environmental control system suit loop and the interior of the spacesuit other categories include those material applications in the high pressure oxygen system materials used in hermetically sealed containers with no means of receiving a supply of oxygen materials used inside unsealed containers with or without an internal ignition source materials used in non flight equipment during closed hatch power on tests and in uninhabited portions of the spacecraft simultaneously exposed to ignition sources and an atmosphere which will support combustion in recent months the study of fire and materials was given greater urgency many groups within the manned spacecraft Center are conducting intensive materials investigations one of the most active in this science is the materials laboratory of the crew systems divisions supporting development branch peer through testing the characteristics of the materials are determined it is here that materials must conform to acceptance guidelines and test requirements to select candidate materials flammability tests are run to determine the rate of propagation those that are found to support combustion are detected and eliminated others are categorized according to their degree of flammability for those major exposed materials in the crew bay environment the criteria of acceptability is that they must be self extinguishing when a test specimen is ignited at the bottom materials are tested in an oxygen-rich atmosphere of sixteen point five pounds per square inch absolute like the test we are about to observe they are also tested at six point two pounds per square inch absolute oxygen chamber pressure for qualification and selected areas of both the Apollo command module and the lunar module included in the equipment is a flammability test chamber it contains inlets for vacuum and ignition wire air and oxygen all material samples must be clean and free of cuts and abrasions or other imperfections paints and coating materials are applied to a thickness equivalent to normal use the test sample is ignited by a wire wrapped with thin tissue paper which is placed in contact with the bottom edge of the sample electric current through the wire ignites the tissue paper testing begins with the evacuation of the chambers and the elimination of leaks after oxygen repressurization and stabilization to the required psi a the test specimen is soaked in oxygen subsequently current is applied and the test is underway combustion characteristics are noted during the process and the pressure rise is recorded observe that the sample material burns fairly rapidly and does not extinguish itself let's repeat the propagation rate test but this time we will use a material called beta fabric that does qualify and can be used in the Apollo crew Bay Area's with safety with test conditions the same we see that the test material a new glass fiber cloth does not burn when an attempt is made to ignite it in the oxygen-rich atmosphere the material is well qualified previous tests have shown that beta fabric has a melting temperature of over 1500 degrees Fahrenheit in this demonstration the burning rate of a sample of the silicone rubber oxygen hose now in use is compared to the burning rate of a floral compound presently being studied as a possible replacement the candidate material appears promising but will undergo a wide variety of tests before being accepted for use in the spacecraft tests such as these and other flammability studies are being conducted on a wide range of materials any substance or fiber organic inorganic natural or synthetic that offers heat retardant or flame resistant characteristics is being closely examined in fact at this laboratory in the past eight months over 1,100 tests of various types have been made on more than 300 materials this includes those minor exposed materials in discrete locations in the crew Bay atmosphere their criteria of acceptability is that the propagation rate test measured downward does not exceed three tenths of an inch per second and that no spark drip or release of hot particles occurs during burning chamber pressure environments remain the same sixteen point five and six point two PS they for the Apollo command module and 6.2 for the lunar module for this particular test we will use an oxygen chamber pressure of 6.2 the material sample is Nomex a material that is known to ignite when it reaches a temperature of 1000 degrees Fahrenheit in oxygen but does not burn in normal air atmosphere the material burns with a bright yellow flame evolving some black soot burning rate is 0.193 inches per second now let's conduct a second test but this time we increase the chamber pressure to sixteen point five pounds and see how ninety-five percent minimum oxygen atmosphere affects the burning rate of another sample of Nomex from the results of this test it is apparent that by increasing the percentage of oxygen the ratio of burning rate increases considerably we must conclude then that Nomex would not qualify for the increased pressure environments of the Apollo command module however the material may be acceptable at 6.2 PSI aid for lunar module crew BAE application once more let's repeat the rate of propagation test at sixteen point five but use a material that does qualify with the same test conditions a sample of polybenzimidazole or PV I webbing is placed in a pressure chamber and prepared for ignition at the top during this test we can see that burning is slower and that the propagation rate does not exceed the disqualifying three tenths of an inch per second Apollo spacecraft fire protection also includes the elimination of possible ignition sources such as short circuited wiring when near other materials the faulty wiring becomes a serious flammability hazard short circuit flammability tests are conducted under simulated spacecraft environments in which candidate materials are exposed to repeated arcing in order to determine the minimum current required to ignite the test material test equipment includes the 3 cubic foot steel environmental test chamber and the short-circuit flammability tester ignition source is an external power supply providing steady DC current that can be adjusted by a variable resistor tests are conducted in oxygen-rich atmosphere zat six point to sixteen point five and nineteen point zero PSI a since all major and minor exposed materials in the Apollo crew Bay Area's as well as those in the ECS spacesuit loop are subject to qualification to demonstrate short-circuit testing let's use a sample of the cotton constant wear garment material and an oxygen chamber pressure of nineteen point zero pounds the sample is mounted over a wire grid attached to the sample holder and the entire apparatus is then installed in the environmental chamber following evacuation and elimination of leaks the chamber is repressurized to the required level with 95 percent pure oxygen an electric probe is charged with a constant voltage of 28 volts and is controlled from outside the chamber the probe is then touched to the sample in an effort to produce an electrical discharge the current is then varied in steps in an attempt to cause ignition if ignition occurs within 15 minutes the procedure is repeated but at a lower level until the minimum value capable of igniting the material is determined if ignition does not take place within the time limit the material is considered safe nonmetallic materials in spacecraft atmospheres must have sufficiently high ignition temperatures to prevent the start of a fire spark ignition characteristics are determined through flashpoint and ignition point test in chamber pressures of 6.2 and 16.5 psi a in an oxygen-rich environment a material that emits vapors which when mixed with oxygen produces a visible flash of the temperature of less than 400 degrees Fahrenheit is not acceptable neither is a material that shows evidence of charring sustaining combustion or a chemical decomposition under 450 degrees Fahrenheit for this test we will use a lubricating compound the 3 cubic foot steel environmental test chamber is again used along with a special flash ignition tester other items of equipment are an oxygen system for the chamber thermocouples for temperature measurement and spark ignition equipment to include spark needles and a high voltage capacitor to supply the sparking energy depending on the type of material test specimens are cleaned and cut to size or if a paint or sealant it is applied in the proper thickness to conform to established practice with the environmental chamber containing the test sample closed and free of leaks the Chamber's brought to the test pressure of sixteen point five pounds the chamber is heated to raise the sample temperature at least 25 degrees in one minute from 200 degrees Fahrenheit when the temperature is stabilised sparking occurs and is repeated at one-minute intervals after each 25 degree temperature increase until flashpoint has been observed or a maximum of 500 degrees Fahrenheit has been attained flashpoint is that temperature at which vapors ignite with a non self-sustaining flame and no evidence of chemical decomposition the temperature at which a self-sustaining self-propagating flame as apparent is the ignition point fail you to obtain a flash or ignition is sufficient proof that the tested material has passed this test for non combustible tea in addition autogenous or self generating ignition point determinations are made on crew compartment materials with the same flash ignition tester - its ignition capabilities this test conducted under similar conditions at 16 point 5 psi a determines the behavior of materials in an oxygen laden atmosphere at elevated temperatures when there is no outside source of ignition after the flash ignition tester has been inserted and the chamber stabilized at the required test pressure the chamber is heated at the rate of 25 degrees Fahrenheit per minute however this time the heat is allowed to rise until ignition or a thousand degrees Fahrenheit is reached at which time the heat is turned off autogenous fire point is the lowest temperature which the mixture of vapors from the material and oxygen continued to burn after self ignition in this test we used a sample of the cotton constant wear garment from our thermocouple readings we noticed that ignition did not take place until the temperature had reached 600 degrees Fahrenheit 30 minutes after the test commenced when no ignition occurs the test sample is examined after cooling for char melt or other evidence of destruction flame impingement tests are conducted by the laboratory at six point two and sixteen point five psi a in an oxygen-rich atmosphere to determine the thermal protective qualities of materials such as spacesuit assemblies when subjected to a controlled temperature flame a flame impingement test assembly is prepared with several thermocouples mounted between layers of candidate spacesuit materials to give a comparison of the temperature gradient within the assembly using a glass Bell Jar test chamber with its inlets for vacuum air oxygen natural gas thermocouple leads and ignition wire the impingement assembly is mounted in a sample holder and inserted the assembly placed horizontally over the flame can be adjusted to provide a temperature of 1800 degrees Fahrenheit at the surface of the sample of material once again the test chamber is evacuated check for leaks then we pressurized with oxygen to the required test pressure the flame which is a mixture of natural gas and oxygen is started and regulated from the outside to produce the desired temperature when the proper temperature is reached the impingement test assembly is lowered and exposed to the flame this test is terminated when the topmost layer a sample of beta cloth reaches a temperature of 250 degrees Fahrenheit the test can also be run by measuring the temperature rise over a predetermined period of time thermocouple readings are recorded on a special data acquisition system and later converted to data reduction graphs these data are useful in the design of protective containers for flammable materials the Apollo 3 man life raft properly designed containers will allow such equipment to be operable after a medium intensity fire while perhaps not as scientific in terms of pressure chambers controlled environments and computers but graphic from a point of view of the men involved in our spacesuit program this demonstration illustrates the flame resistant and heat retardant qualities of an experimental materials layup now being considered for our space program there are other tests on nonmetallic materials among them thermo gravimetric and differential thermal analysis physical and endurance tests thermal and radiation tests in addition to the broad testing support the laboratories are called upon for special development projects such as the implementation of qualified materials in an integrated Apollo thermal micrometeoroid spacesuit the selection of fire resistant materials in the Apollo program is a most important one in the design and redesigning of all future spaceflight equipment and ground support hardware the manned spacecraft Center follows the philosophy that regardless of applications any materials now being used where there is a non flammable substitute available shall be replaced immediately that if no substitute exists the containers of such flammable materials must be insulated to prevent the internal temperature from exceeding the ignition point of the materials and that is non flammable materials are developed they will be considered for replacement of flammable materials immediately the risk of fire in an Apollo spacecraft may never be completely eliminated a compromise must exist between the specific function of a material used in the spacecraft and its combustion characteristics flammability testing those are from it a whole new body of knowledge as to the causes and propagation characteristics of fire is being developed knowledge that will not only contribute to the success and safety of Apollo and succeeding generations of spacecraft but will add to the comfort and safety of American homes and industry in terms of new materials new fabrics that will reduce the hazard of fire [Music]