NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Acoustic-Modal Testing of the Ares I Launch Abort System Attitude Control Motor ValveThe Attitude Control Motor (ACM) is being developed for use in the Launch Abort System (LAS) of NASA's Ares I launch vehicle. The ACM consists of a small solid rocket motor and eight actuated pintle valves that directionally allocate.thrust_- 1t.has-been- predicted-that significant unsteady. pressure.fluctuations.will.exist. inside the-valves during operation. The dominant frequencies of these oscillations correspond to the lowest several acoustic natural frequencies of the individual valves. An acoustic finite element model of the fluid volume inside the valve has been critical to the prediction of these frequencies and their associated mode shapes. This work describes an effort to experimentally validate the acoustic finite model of the valve with an acoustic modal test. The modal test involved instrumenting a flight-like valve with six microphones and then exciting the enclosed air with a loudspeaker. The loudspeaker was configured to deliver broadband noise at relatively high sound pressure levels. The aquired microphone signals were post-processed and compared to results generated from the acoustic finite element model. Initial comparisons between the test data and the model results revealed that additional model refinement was necessary. Specifically, the model was updated to implement a complex impedance boundary condition at the entrance to the valve supply tube. This boundary condition models the frequency-dependent impedance that an acoustic wave will encounter as it reaches the end of the supply tube. Upon invoking this boundary condition, significantly improved agreement between the test data and the model was realized.
Document ID
20100022026
Acquisition Source
Marshall Space Flight Center
Document Type
Conference Paper
Authors
Davis, R. Benjamin
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Fischbach, Sean R.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Date Acquired
August 24, 2013
Publication Date
May 3, 2010
Subject Category
Acoustics
Report/Patent Number
M10-0184
Meeting Information
Meeting: 57th JANNAF Joint Propulsion Meeting
Location: Colorado Springs, CO
Country: United States
Start Date: May 3, 2010
End Date: May 7, 2010
Sponsors: Department of the Air Force, NASA Headquarters, Department of the Army, Department of the Navy
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available