scope:

Description of Driving Event:

Motor information was routinely tabulated during the manufacture of solid rocket motors. This information was furnished by the motor vendor (or obtained by resident representatives) from inprocess propellant mechanical and ballistic properties testing. Typical properties included stress, strain, density, liquid-strand burn rate, propellant burn rate from subscale motor testing, and peel strength. Once logbooks were available, other parameters were tabulated. Typical properties were motor assembly total weight, propellant weight, case weight, linear weight, insulation weight, igniter propellant weight, igniter assembly weight, and nozzle assembly weight.

Post-flight motor performance information was tabulated for all flights (some fourth stage motors were not instrumented). Information items included thrust and chamber pressure. From these items were calculated Isp, total impulse, web burnout time, total burn time, and the pressure integral.

Beginning in 1984, age related information was accumulated for the solid rocket motors to aid in engineering evaluation of motor shelf life. Typical information accumulated from storage site inspections, return-to vendor inspections, or launch site receiving inspections which included propellant shore a hardness, radial slot width measurements, and visual inspections of the propellant grain surface and bond lines.

As a result of the evaluation of motor shelf life, the Scout Program has been launching vehicles with motors that are well beyond the shelf life established by the motor manufacturer. Motor production to replace aging motors is costly. Use of the tabulated age related information allowed engineering and quality/reliability personnel to extend motor shelf life. New production was not required. Inventory motors could be flown.

Further information can also be obtained by contacting the Reliability and Quality Division of Loral Vought Systems at P.O. Box 650003, Dallas, TX 75265-0003 or calling (214) 603-1000.