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This Defense Intelligence Reference Document, DIA-08-0912-008, is dated 12 January 2010. It was prepared by the Defense Warning Office's Acquisition Support Division at the Defense Intelligence Agency as one of a series of FY 2009 technology reports under the Advanced Aerospace Weapon System Applications program. It reviews materials for launch vehicles, space vehicles and reusable rocket engines, including aluminum alloys, polymer and metal matrix composites, titanium and nickel alloys, and titanium aluminides. It concludes that newer materials and integrated design could improve on the space shuttle.
From the source:Release of 2026-09-18 Incident: 1/12/10, Las Vegas, Nevada. Released with redactions. This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD surveys the structural materials needed for advanced aerospace platforms and argues that material choice cannot be separated from overall vehicle design, because launch vehicles, space vehicles, reusable systems, and propulsion hardware each face different temperature, durability, weight, and manufacturing constraints. The report reviews a range of candidate material classes, including advanced aluminum alloys; polymer-, aluminum-, and titanium-matrix composites; titanium alloys; nickel-base alloys; refractory metals; ceramic-matrix composites; carbon-carbon composites; and titanium aluminides. It emphasizes that balancing performance against practical limits such as fabrication methods, cost, inspection, contamination control, and service environment remains a major challenge. Its overall conclusion is that many promising materials exist, but their usefulness depends on application-specific tradeoffs and on closer integration of material selection with design and manufacturing, with some systems judged to be more valuable targets for development than others.
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Therefore, instabilities that cause time-dependent reductions in toughness must be
understood before these materials can be considered candidates for future TPS
applications.
Titanium Aluminides
Titanium aluminides are intermetallic compounds that form between Ti and Al. There
are three such compounds-TbAI, TiAI and AbTi-but the one of principal interest is
TiAI, often referred to as gamma titanium aluminide or y-Ti AI. This compound contains
about 35 weight% Al, but ternary and quaternary alloys based on TiAI typically contain
somewhat less than th is amount. y-TiAI is interesting for intermediate-temperature
applications for several reasons. These include a lower density, at least a 125 °Celsius
higher temperature capability, and better surface stability (oxidation resistance)
compared with conventional Ti alloys. The surface scale that forms during oxidation of
y-TiAI is Al rich and is more protective than the TiO2 scale that forms on conventiona l Ti
alloys. Like most other intermetallic compounds, y-TiAI has very limited ductility at
temperatures up to about 600 °Celsius but is not brittle in the classical sense; that is, it
has the capabi lity to deform plastically before fracturing. The ductility increases as
temperatures increase and is quite good at normal service temperatures.
y-TiAI alloys' limited ductility poses manufacturing problems for any wrought products.
These issues are manageable but reduce product yields, which in turn impacts cost.
Recent work in Austria has demonstrated that some y-TiAI alloys can be made into
sheet. This is particularly relevant to applications such as metallic TPS. Other work has
demonstrated that some y-TiAI alloys can be conventionally forged, albeit with care.
Should one or more of the efforts currently under way to produce low-cost, prealloyed
Ti powder prove successful, the availability of affordable y-TiAI alloy powder could be a
major cost breakthrough.
The development and maturation of y-TiAI alloys has taken more than 30 years. This is
in part due to the lack of actual production applications because of designer's concerns
regarding the limited low-temperature ductility of all the y-TiAI alloys. Today, finally,
there are several applications of alloys based on y-TiAI, the most significant of which are
two stages of low-pressure turbine blades in the engine General Electric is providing for
the Boeing 787 and the growth 747 (called the 747-8). These blades are cast to near
net shape and will operate at temperatures up to about 750 °Celsius. Another
application is a cast y-TiAI turbocharger rotor Mitsubishi uses in a production auto
because it has half the mass of an equivalent Ni-base alloy component.
A potentially ideal, high-volume application of y-TiAI alloys is exhaust valves for autos.
If the low-cost powder mentioned earlier becomes a reality, th is factor, coupled with
the current pressure to improve fuel consumption in American cars, could make this
prospect a reality. The point of this short discussion of non-space-related applications of
y-TiAI alloys is that rea lization of any or all of these appl ications will create a stronger
production base for this class of alloy, which in turn will make their introduction into
future space platforms easier and more cost effective.
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Official release, from the pursue collection. The PDF is mirrored here; the original link is above. 27 pages are in the text index: search them above, or from the library's search.