Reusable Launch Vehicle Technology Development and Test Program (1995) / Chapter Skim
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3 REUSABLE CRYOGENIC TANK SYSTEM
3 REUSABLE CRYOGENIC TANK SYSTEM
Pages 28-42
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From page 28... ...
Because the tanks are used to store propellants, which comprise most of the vehicle volume, they contribute significantly to the mass of the primary vehicle structure. To date no reusable cryogenic tanks of this scale have been used in flight, but two sub scare models have been built and tested at LH: temperature under the auspices of the National Aerospace Plane (NASP)
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From page 29... ...
These correlations will be at a level of confidence sufficient to ensure that analytical tools are valid for purposes of full-scale vehicle design. Estimated requirements for the REV, which will be supported by this analysis are a minimum of 100 lifetime missions including depot maintenance not more than every 20 missions, volumetric weight targets (which will be updated for selected X-33 configurations of 0.7 Ib/ft3 or less for an oxidizer tank and 0.5 Ib/ft3 or less for a liquid hydrogen tank, with leakage rates within the limits set for the space shuttle.
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From page 30... ...
The Super Lightweight Tank (SEWT) for the space shuttle at the NASA M~choud Assembly Facility in New OrIeans, Louisiana, is being constructed using alloy 2195 thick plate stock with Al alloy 2219 ring frames.
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From page 31... ...
In cooperation with MSFC, the Edison Welding Institute, Boeing, and Reynolds Aluminum, one industry partner will be examining a new method of "fnchon-stir welding." The fnction-scir-welding process shows promise and could, if successful, solve the welding problems associated with Al-Li alloys. Data for alloy 2195 on the space shuttle SEWT will also be incorporated into the database.
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From page 32... ...
Tests should include wide panel testing, not just coupon testing, of the weld zone because cutting out coupons may relieve the residual stresses associated with the welding process that can affect fracture toughness and fatigue properties. Fracture
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From page 33... ...
MSFC has been experimenting with an Al-Si alloy filter, which has resulted in some improvements in weld repair. But the committee believes MSFC should exercise caution in using an Al-Si filler material because silicon combines with Al-Li to form an AlLiSi phase that attracts and absorbs moisture, which increases susceptibility to stress-corrosion cracking.
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From page 34... ...
The Al-Li LOX tanks constructed during Phase ~ must be scaleable to the tank sme required for Phase IT. Problems with the through-thich~ess properties of thick plate, the weldability of thin sheet, and other properties of the candidate Al-Li alloys must be identified and resolved prior to tank construction in Phase IT.
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From page 35... ...
Because of the limited database for alloy 1460 and possible lot-to-lot of all alloy 1460 variations in Al-Li alloys, extensive coupon testing product forms should be conducted. Because Al-Li alloys have been shown to be more anisotropic than conventional aluminum alloys, their texture, strengths, and elastic moduli should be characterized, and properties in the C, T
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From page 36... ...
Caution is recommended regarding use of Ti honeycomb, which is being studied by one industry partner, because the Ti alloy Ti-6Al-4V is susceptible to hydrogen embnttlement and not enough hydrogen embr~ttlement studies have been conducted on the ELl variant of this alloy. Thermal/load cycle testing on the alloy 2195 tank is strongly recommended to ensure that the integrated system will satisfy reusability requirements and to provide a database comparable to the database designed for the alloy 1460 tank-flight and ground test articles in the DC-XA program.
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From page 37... ...
The tank was then filled with liquid nitrogen, taken to full pressure, and loaded simultaneously with the maximum predicted positive and negative structural loads. Four hydrogen detectors were placed in various locations on the tank for each test, and air samples were taken at venous locations near the tank skin during the low-temperature tests.
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From page 38... ...
FINDING AND RECOMMENDATIONS ORGANIC-MATRIX COMPOSITE TANKS Findings In general, the criteria for Phase II goals appear to be well conceived and reasonable, with one exception. It is not clear that the requirement of 0.5 lb/ft3 or less for the hydrogen tank is appropriate as a universal, absolute target.
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From page 39... ...
There is no precedent for this level of reusability, particularly for composite tanks. In addition to the temperature and pressure cycling, requirements for reusability and multiple orbital flights mean the tanks must withstand particle impact damage and be repairable.
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From page 40... ...
Evaluation of the use of composite tanks for LOX should be continued to resolution. · Thermal/Ioad cycle testing should be conducted on all the 8-ft-diameter or larger tanks with cryoinsulation, interfaces with neighboring components and TPSs affixed to ensure that the integrated system satisfies reusability requirements.
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From page 41... ...
Pp. 80-87 in the 4th International Conference on Aluminum Alloys: Their Physical and Mechanical Properties, vol.
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From page 42... ...
1973. Environmental hydrogen embr~ttlement of an a-,B titanium alloy: Effect of hydrogen pressure.
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