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Features Of Cavity Flow And Acoustics Of Stratospheric Observatory For Infrared AstronomyThe stratospheric observatory for infrared astronomy (SOFIA) is a 2.5 meter aperture Cassegrain telescope with a Nasmyth focus that will be housed in an open cavity in the Boeing 747-SP aircraft and operated at altitudes around 41,000 feet for infrared (IR) viewing of celestial events of astronomical nature. At these altitudes the IR viewing capability of SOFIA far exceeds that of any ground based system. To minimize IR transmission losses, SOFIA will operate with an open cavity. Such an open cavity during flight creates several challenging aerodynamic and aeroacoustic design problems. Foremost of these are: the shear layer over the cavity may cause unwanted resonance if the cavity is untreated; this might give rise to excessive sound pressure levels (SPL) in the cavity and thus affect the unsteady loads on the telescope; the unsteady flow within the cavity produces large dynamic loads and moments that will impact the pointing accuracy of the telescope; the open cavity and the shear layer control devices produce additional drag that will affect directly the time of flight of the mission; the aft location of the cavity down stream of port wing will affect the the flow on the aircraft control surfaces and thus the stability of the aircraft. Also, the highly turbulent shear layer over the cavity and the temperature gradients and 'hot spots' within the cavity can produce a wave front error of the image when it reaches the focal plane of the recorder.
Document ID
20020034856
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Srinivasan, G. R.
(Sterling Software, Inc. Moffett Field, CA United States)
Klotz, S. P.
(MCAT Inst. Moffett Field, CA United States)
Tu, Eugene
Date Acquired
August 20, 2013
Publication Date
January 1, 1996
Subject Category
Fluid Mechanics And Thermodynamics
Meeting Information
Meeting: 1997 ASME Fluids Engineering Conference
Location: Vancouver
Country: Canada
Start Date: June 22, 1997
End Date: June 26, 1997
Sponsors: American Society of Mechanical Engineers
Funding Number(s)
CONTRACT_GRANT: NAS2-13210
PROJECT: RTOP 188-78-60
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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