"Once upon a time, many years ago..." as an undergraduate student at Texas A&M, I had a part-time job as a student assistant at our big, 8'x10' test cross-section, wind tunnel (uses a cut-down "Silverplate" B-29 Curtiss-Electric prop as its fan) and got to observe low-speed testing of the shuttle configurations as they evolved from straight wings and tail to pure delta wing to the final configuration that flew. At one point with the pure delta wing, they were looking at hanging four jet engines under the wing, the engines were humorously labeled with different fuels:
#1 - JP-4
#2 - 80/87 av-gas
#3 - coal oil
#4 - Wisconsin milk (a jibe at Sen. Proxmire).