pumps easier because they would not have critical speed problems. Although highly reliable pumps can be designed without this technology, hydrostatic bearings show great promise and could be available for use in an RLV engine with further development.

This unit features a higher performing injector and a new, single-tube heat exchanger. Manufacturing heat exchangers for converting liquid oxygen to gaseous oxygen (to pressurize the oxygen tanks) has been complicated because the exchanger consists of a primary tube, a bifurcation joint, and two secondary tubes that are assembled by welding. Advanced technology to produce the very long jointless tube of the appropriate material has recently been developed, and single-tube heat exchangers can now be fabricated. The new heat exchanger eliminates a potential Category I failure (i.e., a failure involving loss of life or mission) that might have occurred as a result of leakage in one of the many welds in the original heat exchanger. Eliminating the welds also enhances producibility. The single-tube heat exchanger also improves maintainability and operability, and eliminating welds reduces concern about leakage and failure of tubes. This, in turn, reduces the need for inspections and checking for leaks.

The programs for improving the producibility of the main combustion chamber (MCC) are based on eliminating welds and developing new fabrication processes. The potential payoff of this approach is illustrated in the case of the SSME, for example. Rocketdyne reported that the SSME Phase II engine MCC requires 40 months to manufacture. MCC manufacture of the SSME Block II engine will be reduced to 24 months by using precision castings of the combustion manifolds rather than welding and by improvements in the plating and assembly process. Changing to a proposed milled channel combustor allowed the manufacturer to demonstrate production of a universal MCC in 12 months. This universal MCC will need to be certified prior to use in the SSME, but these changes in fabrication and material processes have yielded dramatic improvements in producibility. The goal is to extend the life of the SSME thrust chamber to at least 100 flights. Although the universal MCC would greatly enhance engine producibility, it may not be available in time for the X-33.

Programs for simplifying the fabrication of nozzles have also been proposed. One of these combines Russian technology and advanced manufacturing technologies to produce a lightweight, milled, channel nozzle.

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)