Stability testing of full scale tactical motors

Blomshield, Fred S.; Crump, J. E.; Mathes, H. B.; Beckstead, M. W.

doi:10.2514/6.1991-1954

Cited by 17 publications

(23 citation statements)

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“…A small value of L , which has been shown to induce bulk-mode or L instability [23], has also been suggested as a contributing cause of the initial pressure spike seen in this motor [24]. This spike has also been attributed to ignition phenomena or erosive burning [21,25].…”

Section: Nawc Motor No 13mentioning

confidence: 99%

Solid Rocket Motor Internal Ballistics Simulation Using Three-Dimensional Grain Burnback

Willcox

Brewster

Tang

et al. 2007

Journal of Propulsion and Power

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Internal ballistics simulations of solid rocket motors have been conducted with the propellant grain's 3-D burning surface geometry described by a new minimum distance function approach and the internal flowfield represented by 1-D, time-dependent, single-phase compressible flow equations. The combustion model includes erosive burning and unsteady, dynamic burning corresponding to transient energy storage in the heated surface layer of the propellant. The integrated internal ballistics code (Rocballist) is used to investigate the role of these two burning rate augmenting mechanisms in solid rocket motor performance. Two tactical motors are used as test cases. Results indicate that dynamic burning can be the dominant factor in producing a short-duration ignition pressure spike in low-L motors, particularly if the L=D ratio is not too large and the port cross section is nonrestrictive (e.g., center perforated grain). However, when L=D is large and the port cross section is noncircular in the aft section (aft fins/slots), erosive burning can take over in dominating the burning rate to the extent that an otherwise progressive pressure-time trace becomes regressive/neutral. That is, erosive burning can effectively prolong the initial pressure spike in some star-aft motors. The results also show that with sufficiently accurate models of dynamic burning and erosive burning, it is reasonable to expect reliable internal ballistics predictions with suitable simplified flowfield models, thereby realizing significant reductions in computation time compared with 3-D, multiphase reacting flow simulations.

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Section: Nawc Motor No 13mentioning

confidence: 99%

Solid Rocket Motor Internal Ballistics Simulation Using Three-Dimensional Grain Burnback

Willcox

Brewster

Tang

et al. 2007

Journal of Propulsion and Power

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“…This implies that the tendency of a motor to become unstable often increases with time. 36,40,41,45,46,47,52 Referring to Figure 8, it can be seen that the magnitude of both driving alphas (those that are positive) and damping alphas (those that are negative) decrease in magnitude as the motor burns to completion. This can be explained by examining the following expression:…”

Section: Stability Observationsmentioning

confidence: 99%

“…40,41,45,46,52,53 A star aft geometry is an example. The driving mechanisms of velocity coupling and distributed combustion have terms like the following:…”

Section: Stability Observationsmentioning

confidence: 99%

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Lessons Learned In Solid Rocket Combustion Instability

Blomshield¹

2007

43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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Over the last 60 years, a considerable amount of time and money has been spent improving our understanding of combustion instability in solid rocket propulsion systems. Over this period, significant knowledge has been accumulated that can influence the acoustic stability of solid propulsive systems. Unfortunately, many of these lessons learned about combustion instability remain the knowledge of a select few in government and industry who work with combustion instability on a daily basis. This paper attempts to organize many of these "rules of thumb" that propellant formulators and motor designers need to be aware of in order to minimize the chances of combustion instability. In addition, several mathematical relationships are presented which can be used to predict the frequency of potential acoustic modes and determine resultant thrust oscillations produced by acoustic oscillations. Also included are some key fundamental equations which can be used to gain insight into combustion instability in rocket motor systems and there is a short section on motor instrumentation. This paper is not an attempt to be an exhaustive study into combustion instability, but rather, will attempt to list in a clear fashion some of the more important lessons learned and empirical observations of solid propellant combustion instability. This paper emphasizes composite propellants, but many observations apply to double base and composite modified double base propellants, as well.

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“…We ran several simulations of NAWC Tactical Motor Number 13 26,27 with two different spatial resolutions and two different fluids algorithm options to study the effect these have on the computed head-end pressure history. Motor 13 is approximately 2 meters in length, 0.12 meters in diameter, and features a cylindrical propellant grain that tapers outward near the aft end, plus a larger cylindrical cavity at the head end for instrumentation.…”

Section: Mesh Refinement Study and Ignition Spikesmentioning

confidence: 99%

Simulations of Slumping Propellant and Flexing Inhibitors in Solid Rocket Motors

Fiedler

Breitenfeld

Jiao

et al. 2002

38th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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We describe and present results from GEN2, the second-generation three-dimensional solid rocket motor simulation package developed at CSAR. The internal gas dynamics, propellant combustion, and structural response are fully coupled. In addition to several test cases, we simulate propellant slumping at a joint slot due to uneven gas pressure loads in the Titan IV SRMU. We also study the motion of a flexible inhibitor and its effect on the gas flow near a joint slot in a section of a typical large solid rocket motor. IntroductionDetailed 3-D simulation of solid rocket motors requires solving a very complex, tightly coupled multiphysics problem that includes a wide range of length and time scales. Obtaining accurate numerical solutions for relatively simple geometries, physical models, and even fairly short burn times, requires enormous computational resources that are available today only at major supercomputing centers. Each physics module (gas dynamics, structural mechanics, etc.) must run efficiently in parallel on many processors and data must be exchanged frequently between modules in order to solve the tightly coupled system.

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Stability testing of full scale tactical motors

Cited by 17 publications

References 0 publications

Solid Rocket Motor Internal Ballistics Simulation Using Three-Dimensional Grain Burnback

Solid Rocket Motor Internal Ballistics Simulation Using Three-Dimensional Grain Burnback

Lessons Learned In Solid Rocket Combustion Instability

Simulations of Slumping Propellant and Flexing Inhibitors in Solid Rocket Motors

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