Alice I. Atwood

Burning Rate of Solid Propellant Ingredients, Part 1: Pressure and Initial Temperature Effects

Burning rate data are presented with respect to initial temperature and pressure for three compounds that are currently used in propellant and explosive formulations. The dependence of burning rate on initial temperature and pressureispresented forammonium perchlorate(AP), HMX, and RDX.Data foringredients being considered for advanced propellants, such as CL-20, ammonium dinitramide (ADN), and hydrazinium nitroformate (HNF) are also presented and compared to the more traditional compounds. These ingredients are all capable of selfdee agration,andtheirbehavioroftencontrolsthebehaviorofthepropellantsinwhichtheyarethemainingredients.

Burning Rate of Solid Propellant Ingredients, Part 2: Determination of Burning Rate Temperature Sensitivity

aep D [± rb=±T0]p Care must be taken in how one evaluates aep when making comparisons of various materials. The collection of burning rate data, number of points measured at a given condition, initial test conditions, and inherent data scatter will have an effect on the value obtained for the burning rate temperature sensitivity. ‡‡;§§ The largestvariationsinburning ratemeasurementsgenerally occur at low pressures, where one approaches the dee agration limit of thematerial,andatregionswhereabreakintheburningratepressure exponentoccurs.Coincidentally,theseareoftentheareasofgreatest interest when determining the burning rate temperature sensitivity. The changes in aep that occur due to data smoothing vs averaging, and with the selection of the initial pressure and temperature conditions, can be signie cant. The effect of initial temperature selection on aep will be demonstrated using the HMX data, and e tting techniques will be illustrated with the ADN data, where considerable data scatter is present. Samples Thedee agrationdataforthesixmonopropellantslisted inTable1 of Ref. 2 will be used to demonstrate the evaluation of burning rate temperature sensitivity. The tabular burning rate data may be found in Refs. 3 and 4. The sample type and preparation was described in Ref.4.Alloftheburningratemeasurementsusedinthispaperforthe calculations were made using the cinephotomicroscopy technique also described in Refs. 3, 4, and elsewhere.

Experimental Investigation of the Decomposition Preceding Cookoff in a Composite Propellant

The decomposition preceding autoignition of an ammonium-perchlorate-based composite propellant was experimentally investigated. Autoignition temperature is measured for a selected heating rate. At that same heating rate, differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared spectroscopy, and hot-stage microscopy are employed to study the propellant behavior leading to reaction. These experiments are conducted on both cured composite propellant and individual ingredients, including neat ammonium perchlorate and a cured binder. For a heating rate of 2 °C/min., it is determined using thermogravimetric analysis/Fourier transform infrared that ammonium perchlorate and the binder begin to react together near 150°C, whereas differential scanning calorimetry shows initial exothermic behavior after the orthorhombic-to-cubic phase transition near 240°C. This disparity is discussed and further investigated using larger-scale cubes of propellant heated in ovens at the same heating ...

Design of a Robust High Altitude Rocket Motor Igniter

In order to ensure reliable high altitude ignition of the improved Black Brant Mk 1 sounding rocket, a new igniter was designed and tested. Since traditional theoretical methods for calculating the required igniter charge size gave widely varying requirements, an empirical method was instead utilized. Various igniter models were fired in an enclosed chamber and heat flux and pressure outputs were measured. These data were compared to laser ignitability results obtained for the Black Brant solid propellant to ensure that sufficient igniter output was provided. A static test and flight test demonstrated that the redesigned igniter performed well to ignite the rocket under near vacuum conditions.

Characterization of impact-induced violent reaction behavior in solid rocket motors using a planar motor test model

Abstract A planar model of a solid rocket motor with a central bore has been developed that allows visual observation of impact-induced violent reaction processes (e.g., nondetonative explosions and delayed detonations). Studies have been conducted, using this model, to characterize the response of full-scale motors to projectile impact. A comparison of explosive burn reaction data from planar model and full-scale tests shows a number of similarities. In particular, displays of burning, fragmented propellant ejects are qualitatively the same. In planar motor tests, these displays result from two reactions, a brief, intense one within the bore and a longer duration, less intense one within the web. These tests also show an apparent inverse relation between the two reactions, for some propellants, arising as a result of bore width changes or mechanical property differences. This paper summarizes the results of a number of studies conducted to characterize the two types of reactions and define the relationship between them. These studies show that the two are independent events and that the inverse relation, when it involves bore width changes, is most likely the result of depressurizationrelated phenomena whereas, when it involves mechanical property differences, may be the result of penetration heating differences.