Problems and limitations associated with JP fuels at high Mach numbers have led to an interest in fuels with better heat sink and high temperature capabilities such as methane studies have shown methane to offer performance advantages for SSTs relative to JP, but the overall attractiveness of methane will depend upon the extent advantages are nullified by practical disadvantages. Problems and penalties of storing methane in an aircraft constitute some of the importrant “practical disadvantages.”
Several representative methane storage schemes for Mach 3-6 transport aircraft are evaluated, primarily on the basis of minimum weight. Fuel system weight (including tankage, insulation, plumbing, boiloff, etc.) is shown to be 6.3-13.6% of the fuel weight for methane depending upon the type of storage scheme used and upon the aircraft speed and range. By contrast, fuel system weight for JP is 2.5-3% of the fuel weight. Effects of the fuel system fraction (ratio of fuel system to fuel weight) upon payload are shown.
This report serves as a “primer” on the topic of methane storage in aircraft. It also brings unresolved issues into sharper perspective and suggests what should be done to clarify the future role of methane as an aircraft fuel.