FEASIBILITY DEMONSTRATION OF PYROLYTIC GRAPHITE COATED NOZZLES
Quarterly progress rept. no. 1, 1 Feb-30 Apr 1964
ATLANTIC RESEARCH CORP ALEXANDRIA VA
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The objective of this program is to demonstrate the feasibility of pyrolytic graphite coatings for use in uncooled solid propellant rocket nozzles in a size range of use for practical propulsion units under very severe operating conditions. In prior work the excellent serviceability of pyrolytic graphite coatings in 12-inch diameter nozzles was demonstrated with propellants having flame temperatures from 5500 to 6500 F. In the current work nozzles of 1.1-inch and 2.3-inch diameter are to be tested with a 6500 F propellant. This report describes the work of the first quarter of this program. Thermal analyses were completed on several nozzle systems typical of those to be used in motor firings. These analyses indicated the adequacy of the designs selected. Design of the 1.1-inch diameter test nozzle was completed. Several pyrolytic graphite coated throat inserts were prepared. Problems with delamination cracks occurred with those coatings. In the first motor firing test partial coating failure and subsequent edge spalling combined to cause erosion of the coating at a rate substantially above the predicted capability of the material.