A nickel-steel alloy used in the construction of spacecraft. It is a high-temperature material that can withstand re-entry temperatures. Rene 41 has been used for many vehicle parts, such as the conical walls of the Mercury spacecraft capsule and the internal load-carrying structure of the Dyna-Soar. Tests on spacecraft integral tank and fuselage structures found that Rene 41 panels have a life cycle of 500 ascents and re-entries.