Accession Number:

AD0392561

Title:

DEVELOPMENT OF PYROLYTIC GRAPHITE COATINGS FOR ROCKET NOZZLES

Descriptive Note:

Final rept. 1 Jan 1967-15 Aug 1968

Corporate Author:

ATLANTIC RESEARCH CORP ALEXANDRIA VA

Personal Author(s):

Report Date:

1968-08-01

Pagination or Media Count:

80.0

Abstract:

The program to develop pyrolytic graphite PG coatings for advanced rocket nozzle service included three phases 1 coating improvement including firing tests 2 study of chemical corrosion of PG in different propellant environments and 3 study of PG-coated nozzles to restart motor service. A stress analysis study showed the importance of selected variables such as substrate properties, coating thickness, and geometrical considerations on residual stresses imparted to the composite nozzle system from the deposition cooldown cycle. Based on these studies, techniques were worked out to produce defect-free PG coatings on substrates which provided good firing test results. Limitations on the serviceability of PG coatings in 6550 F propellants were found to be about 45-sec duration at 700 psi. Under these conditions, average erosion rates were 1 milsec but in local areas the average rate was greater. With lower temperature propellants the erosion of PG coatings was negligible. Computer programs were developed for calculating surface thermochemical response of materials and temperature and surface recession history of composite nozzles. Experimentally - determined kinetic reaction rate constants were used with these programs to predict the erosion of PG coatings. The predictions turned out to be substantially higher than the measurements obtained in firing tests. It was evident from the environmental firing tests that PG coatings are relatively insensitive to a wide range of reactive propellant combinations.

Subject Categories:

  • Rocket Engines

Distribution Statement:

APPROVED FOR PUBLIC RELEASE