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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.
UNCLASSIFIED//P'OR. OP'Pl@IAL WSlii Ql'.L¥ PROPULSION SYSTEMS Among propulsion systems, only reusable rocket engines are considered here because they hold potential for significant progress that could reduce the cost of placing payloads into orbit. The basic concept of the space shuttle main engine is still viable, but the durability of the materials used to make the hardware has been a major expense and source of concern for NASA. Much of the concern is related to the effects of hydrogen on the Ni base alloys used in the turbo pumps. The turbo pumps are the heart of a liquid-fueled hydrogen-oxygen rocket engine because they deliver the fuel and oxidizer to the thrust chamber. The turbo pumps rotate at a very high speed-up to 35,000 rpm. Such speeds create enormous centrifugal stresses in the rotating components, particularly the disks that hold the air foils used to extract work from the hot gas stream. One side of the turbo pump rotor operates in the hot gas stream created by the combustion of the oxygen-hydrogen mixture; the other end is a cryopump that operates at cryogenic temperatures, either in liquid oxygen (90 K) or in liquid hydrogen (20 K). The hot side, a turbine, resembles the turbine rotor in a gas turbine engine and is made of many of the same Ni-base alloys. The cryopump is made of Ti alloys. The turbine essentially operates in a hydrogen-rich supercritical steam environment at a maximum temperature of about 1,050 °Celsius. The turbine disk is a forged Ni-base alloy, and the air foils are single-crystal investment castings. Neither material is well suited to operate in a hydrogen-rich environment; however, no other material class can withstand the operating temperatures and has better hydrogen tolerance-a situation that still prevails today. The mechanism of hydrogen-induced cracking is much better understood today as the result of extensive research over the past 25 years. Therefore, it would be very useful to use this improved understanding to design a Ni-base alloy that has improved hydrogen tolerance. If successful, a turbine that has improved resistance to hydrogen cracking would greatly reduce the intermission refurbishment time and cost. Traditionally, the cryopump rotating parts have been made from forgings of the near-o, phase Ti alloy Ti-SAl-2.SSn (Ti-5-2.5). This alloy has been chosen for its superior notched tensile strength compared with Ti-6-4 when tested at cryogenic temperatures . Hindsight suggests it is unclear that notched tensile strength is the best criterion for selecting a cryogenic rotor material. The use of notched tensile strength originated with steels. Here, the hydrostatic stress state at t he notch root could trigger the onset of brittle fracture of the type seen in smooth tensile tests below the ductile brittle transition temperature (DBTT). Ti alloys do not exhibit a DBTT; therefore, true fracture toughness measured at the re levant temperature is a more accurate indication of the fracture resistance of the rotor. An examination of the limited available fracture toughness data for the two alloys shows no clear advantage in using Ti -5-2.5. Because Ti-5-2.5 is more difficult to produce than Ti-6-4, using Ti-5-2.5 adds cost to the cryopump. Other, newer, higher strength Ti alloys-for example, several of the newer ~-Ti alloys-may be even better suited than Ti-6-4 is for this application. The critical question of how much toughness is real ly required cannot be answered at present because t he notched tensile ratio has been the deciding criterion. Therefore, a new 21 UNCLASSIFIED/;'FOR. OFFISIAL WSE 8HLY
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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.