ASTM_D_2508_-_93.pdf

Designation:D 2508 93An American National StandardStandard Test Method forSolid Rocket Propellant Specific Impulse Measurements1This standard is issued under the fixed designation D 2508;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the measurement of solidpropellant specific impulse values.1.2 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.2.Referenced Documents2.1 ASTM Standards:D 2506 Terminology Relating to Solid Rocket Propulsion22.2Military Specification:MIL-STD-292C33.Terminology3.1 DefinitionsRefer to Terminology D 2506 or MilitarySpecification MIL-STD-292C.3.2 Definitions of Terms Specific to This Standard:3.2.1 mass of propellant,mp,to be used in the calculationof specific impulse,shall be the mass of propellant charged intothe motor.3.2.1.1 An igniter correction shall be made,determinedeither by experiment or calculation,when the theoretical valueof this correction exceeds 0.1%.3.2.1.2 The difference between before and after firingweights shall be recorded as expended weight.3.2.1.3 The percentage difference between expended weightand propellant weight shall be recorded as either inertsexpended(if the expended weight is higher)or residue re-tained.Values less than 0.2%may be ignored.3.3 Symbols:3.3.1 total impulse I 5*AGFdt.3.3.2 burning time tb5 time from“B”to“E”.3.3.3 action time ta5 time from“B”to“F”.3.3.4 averagepressureoverburningtimePb5*BEPdt/tb.3.3.5 averagepressureoveractiontimePa5*BEPdt/ta.3.3.6 measured specific impulseIsp5 I/mp,which iscorrected to standard conditions in accordance with Section 8.4.Summary of Test Method4.1 This test method sets forth the following:4.1.1 A set of uniform designations to be used for thecalculations.4.1.2 Precautions to be taken in experimental techniques.4.1.3 Acceptable ranges of experimental conditions to as-sure good results.4.1.4 Uniform procedures for correcting measured values toa standard of set conditions.4.1.5 Limited thrust coefficient values for use with thispractice.5.Significance and Use5.1 It is recognized that the size and design of ballistic testmotors affect the determination of propellant specific impulse,and it is not intended that results from this test method be usedto predict performance in motors of size or design widelydifferent from that tested.6.Procedure6.1 Assume a pressure-time or thrust-time trace as shown inFig.1.6.2 The following experimental criteria is recommended toensure meaningful values of Isp:46.2.1 Use a geometry that gives a relatively neutralpressure-time trace,be essentially sliverless,and provides anominal 50-lb grain.A suggested method for achieving theseconditions is to use a thin-webbed cylindrical geometry withends uninhibited.6.2.2 Use a geometry that also gives a value for throat-to-port area ratio of J 5 At/Apof less than 0.35.6.2.3 Use nozzles that give values of Pabetween 5.52 and7.58 MN/m2(900 and 1100 psia)to minimize the pressurecorrection.6.2.4 Use nozzles with an expansion ratio near optimum,but such that no separation due to over-expansion takes placeduring the equilibrium burning time(see Fig.1,C to D).1This test method is under the jurisdiction of ASTM Committee F-7 onAerospace Industry Methods and is the direct responsibility of SubcommitteeF07.02 on Propellant Technology.Current edition approved March 15 1993.Published May 1993.Originallypublished as D 2508 66.Last previous edition D 2508 71(1980)e1.2Annual Book of ASTM Standards,Vol 15.03.3Available from Standardization Documents Order Desk,Bldg.4 Section D,700Robbins Ave.,Philadelphia,PA 19111-5094.4Procedures(except for specific impulse corrections in Section 6)used in thispractice were released by the Chemical Propulsion Information Agency,JohnsHopkins University,Applied Physics Laboratory,Johns Hopkins Rd.,Laurel,MD20707 in August 1968,and are identical in substance to Publication No.174,“Recommended Procedures for the Measurement of Specific Impulse of SolidPropellants.”1Copyright ASTM,100 Barr Harbor Drive,West Conshohocken,PA 19428-2959,United States.6.2.5 Use nozzles that have a conical nozzle with exit conehalf-angle of 15 6 1.6.2.6 Use nozzles that have graphite inserts.6.2.7 Use nozzles that have a conical approach half angle of40 6 10.6.2.8 Use nozzles that have a nozzle convergence ratio(inletarea/throat area)greater than three.6.2.9 Use nozzles that have a ratio of wall radius ofcurvature at the throat-to-throat diameter greater than two.6.2.10 Use nozzles that are insulated.6.2.11 Use weighing equipment and techniques that assureaccuracy to within 0.1%of the propellant weight.6.2.12 Record and use barometric pressure at time of firingas the basis for conversion to psia.6.3 Spe