Apparently you are not familiar with the advances in materials specifically superalloys and the new ceramic matrix composites (CMC) that Pratt and GE are now using in their high performance engines. The high end superalloys (mainly gamma/gamma' NiAl amoung others) have melting temperatures of 1600C. With active cooling and the TBC-TGO-BC-substrate layering used in modern superalloys these parts can be run to 90% of their respective melting temperatures. The most current progress into CMCs using SiC pushes the melting point of the materials even higher having a melting temperature of roughly 2700C for SiC.
In addition to this producing an engine that out preforms the J58 is not outside the realm of feasibility the PW5000-F119 produces similar thrust at almost half the weight (6000lbs for J58 vs 3500lbs for the F119). The main reason that no engine has been built is that there is no need for such performance in current applications.
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Apparently you are not familiar with the advances in materials specifically superalloys and the new ceramic matrix composites (CMC) that Pratt and GE are now using in their high performance engines. The high end superalloys (mainly gamma/gamma' NiAl amoung others) have melting temperatures of 1600C. With active cooling and the TBC-TGO-BC-substrate layering used in modern superalloys these parts can be run to 90% of their respective melting temperatures. The most current progress into CMCs using SiC pushes the melting point of the materials even higher having a melting temperature of roughly 2700C for SiC. In addition to this producing an engine that out preforms the J58 is not outside the realm of feasibility the PW5000-F119 produces similar thrust at almost half the weight (6000lbs for J58 vs 3500lbs for the F119). The main reason that no engine has been built is that there is no need for such performance in current applications.