Reusable Launch Vehicle Technology Development and Test Program (1995) / Chapter Skim
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5 PROPULSION
5 PROPULSION
Pages 55-75
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From page 55... ...
Operability of current engines, in terms of the maintenance, parts replacement, and inspections required after each flight, are too costly in time and manpower to meet the low cost-per-flight goals of the REV. Basic contributing factors to these costs are the lack of significant demonstrated reusability of critical components and adequate, reliable health monitoring instrumentation with automated rapid engine health diagnosis.
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From page 56... ...
Several technology programs in Phase ~ are directed at engine health monitoring and simplifying operational systems. The committee reviewed the engine technology projects established by the prime vehicle contractors and the engine contractors with the intent of determining whether the approach was adequate to support a decision about whether to proceed with an X-33.
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From page 57... ...
The technology development, test, and analysis programs planned for Phase include: analysis of existing rocket engines that may be considered for X-33; evaluation of modifications to existing engines for upgrades to X-33; analyses of new engine systems both for the X-33 and for advanced RLVs; technology programs to improve performance, producibility, reusability, and maintainability/operability for application to the X-33 and REV; and advanced concept studies to evaluate candidates to improve future REVs. Table 5-l is an assessment of technology programs in terms of performance, producibility, reusability, and maintainability/operability.
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From page 59... ...
s9 it: · ~ o - ~ A, ~4 2 P4 a: o ._ c do ._ 8 C~ ~ Cat in m 6 ·!
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From page 60... ...
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From page 61... ...
RD-0120. This Russian LOX/LH2 engine, designed and tested by the Chemical Automatics Design Bureau, was first used in 1976 and has completed 793 ground tests and two successful flight tests (four engines each)
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From page 62... ...
SSME Block · . Modifications of the present SSME engine that will be used in the space shuttle program include improved LOX and EH2 turbopumps, a single-tube heat exchanger, a two-duct powerhead, a simplified low-pressure oxidizer turbopump, a large throat main chamber, and an improved engine controller.
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From page 63... ...
RD-0120AD-~. This modification of the basic RD-0120 design features a reduced nozzle expansion ratio of 37.5:!
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From page 64... ...
rocket engine development. Developing new, simplified pumps with fewer parts that are enabled by hydrostatic bearings will also be a challenge.
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From page 65... ...
Technology programs for these applications are notably absent from the Phase ~ and IT programs. Perfonnance With some improvements in performance, current engines can be used for X-33 demonstrators; however, REV s will require very high rocket engine performance (thrust/weight and specific impuise3.
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From page 66... ...
Concerns about deep throttling during pump speed changes include controlling pump speed with turbine inlet temperatures that do not drop rapidly and are low enough to freeze moisture in the pumps; controlling the preburner injector dynamics, and ensuring sufficient flow to coo} the combustion chambers and nozzle; overall system dynamics; and sustained preburner combustion at the mixture ratios required for deep throttling. Any of these engines that can successfully and reliably deep throttle would be viable for X-33.
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From page 67... ...
This approach does not apply to the Aerospike engine, which uses a conventional gas generator cycle. A main combustion mixture ratio of 7: ~ is also being tested to evaluate performance loss versus vehicle mass fraction gain.
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From page 68... ...
flow tests are planned to evaluate venous nozzle shapes upon expansion, with and without a double contour. New lightweight nozzles, alternate fabrications of nozzle shapes, vanable nozzle expansion area ratios by means of inserts, dual-step nozzles for sea level/altitude performance, and milled slot nozzles are also being investigated.
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From page 69... ...
For example, the producibility of the alternate high-pressure LOX and hydrogen turbopumps of the SSME Block II engine has been improved substantially through development of nonmetallic bearing balls, integral turbine tip seals, precision castings, and single crystal turbine blades. Precision castings have eliminated the sheet metal housings, which required many welds, in the SSME Phase II engine turbopump designs, thus reducing the need for tedious crack inspections and crack weld repairs during fabrication.
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From page 70... ...
Rocket~yne reported that the SSME Phase IT engine MCC requires 40 months to manufacture. MCC manufacture of the SSME Block IT 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.
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From page 71... ...
It was not clear to the committee how thoroughly this question is being addressed. Health Monitoring Onboard or built-in health monitoring for rocket engines involves installing instrumentation to measure critical temperature, pressure, vibration, and rotation speed.
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From page 72... ...
This is a complex problem with a high payoff and should be pursued vigorously because test and evaluation on the X-33 are essential. The committee received relatively little information about health monitoring of the rocket engine from NASA/industry partners.
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From page 73... ...
In addition, engine/propellant conditioning may constitute a significant mass penalty in a mass-cntical vehicle. Development efforts to reduce engine turnaround time significantly after each flight do not adequately reflect the desire for a rocket engine that can be handled the way an operational jet engine is handled.
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From page 74... ...
Current F/W goals of greater than 75 will be very difficult to achieve with existing engines and even new ones, without compromising the structural margins required to satisfy reusability goals. If the requirement of high (sea-level)
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From page 75... ...
Throttling and thrust vector methods, including interaction effects between adjacent engines should also be evaluated. · Overall engine health monitoring requirements should be better defined.
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