On an SSTO vehicle, optimizing nozzle performance on Isp, from sea-level takeoff to the vacuum space environment, will be critical. Several nozzle technology programs are planned for reducing the expansion ratio operation at low altitudes and expanding to high ratios as altitude increases. Development of a two-position, moveable bell nozzle, a dual-inner-contour nozzle to induce flow separation, and an Aerospike altitude compensating nozzle are directed toward this objective. A series of wind tunnel flow tests are planned to evaluate various nozzle shapes upon expansion, with and without a double contour. New lightweight nozzles, alternate fabrications of nozzle shapes, variable nozzle expansion area ratios by means of inserts, dual-step nozzles for sea-level/altitude performance, and milled slot nozzles are also being investigated. These investigations are aimed at: (1) improving sea-level performance of a high nozzle expansion ratio; and (2) reducing the weight of the units. The programs have high merit, and there is much to be learned from them.

In general, the engine companies did not highlight overall engine manufacturing procedures and materials in their presentations to the committee. No product improvement programs were presented that addressed the question of manufacturing hardware exactly to print, although this is a common problem in existing hardware programs and decreases producibility. Because there is only one major U.S. development program for reusable engines, attention should be paid to the issues of producibility.

One of the existing flight-proven engines that may be applicable to the X-33 (i.e., the RD-0120) was designed, developed, and qualified in Russia, where the Voronezh plant manufactures as many as 20 engines a year. Manufacturing time for each engine is reported to be one year. The time required to manufacture one SSME is four to five years, leading to the conclusion that it would be prudent to examine carefully the manufacturing processes and controls used by Russia's Chemical Automatics Design Bureau (CADB). Under a strategic business partnership between Aerojet and the CADB, Aerojet plans to test the RD-0120 in the United States and, pending contract award, will create U.S. production facilities for the RD-0120. A NASA/industry program will facilitate this technology transfer and provide benchmark life testing of the RD-0120 both in Russia and at MSFC. The life tests will provide answers to questions about the maturity of the X-33 and questions on long life engine design. Life tests will be duplicated at NASA MSFC.

FRONT MATTER (R1-R10)

EXECUTIVE SUMMARY (1-10)

1 INTRODUCTION (11-18)

2 PRIMARY VEHICLE STRUCTURE (19-27)

3 REUSABLE CRYOGENIC TANK SYSTEM (28-42)

4 THERMAL PROTECTION SYSTEM (43-54)

5 PROPULSION (55-75)

6 CONCLUSIONS AND OBSERVATIONS (76-80)

A LIST OF PARTICIPANTS (81-82)

B BIOGRAPHICAL SKETCHES OF COMMITTEE MEMBERS (83-87)

C LIST OF ACRONYMS/ABBREVIATIONS (88-88)