The first space flight cryogenic flexible diode heat pipes (CFDHPs) were developed and verified under micro-gravity conditions on the Space Shuttle during STS-94 (July 1997) and the previous, minimum mission STS-83 (March 1997). The heat pipe working fluids were oxygen (with an operating range of 60 to 145 Kelvin) and methane (95 - 175 Kelvin). The heat pipes were verified as part of the Cryogenic Flexible Diode Heat Pipe (CRYOFD) flight experiment. CRYOFD was the third and fourth flights of the Hitchhiker based Cryogenic Test Bed (CTB). CRYOFD was managed by the Air Force Research Laboratory (AFRL) Phillips Research Site with NASA's Goddard Space Flight Center (GSFC) co-sponsoring the experiment, the Air Force's Space Test Program (STP) and GSFC's Hitchhiker (HH) group provided the Shuttle integration and support. Jackson and Tull (J&T) and Swales Aerospace, Inc. (SAI) executed the program as a Phase II SBIR under the AFRL. Additional Support was provided by Aerospace Corporation and Nichols Research Corporation.