Unobtainium

In fiction, engineering, and thought experiments, unobtainium is any fictional, extremely rare, costly, or impossible material, or (less commonly) device needed to fulfill a given design for a given application. The properties of any particular unobtainium depend on the intended use. For example, a pulley made of unobtainium might be massless and frictionless; however, if used in a nuclear rocket, unobtainium would be light, strong at high temperatures, and resistant to radiation damage. The concept of unobtainium is often applied flippantly or humorously. For instance, unobtainium is described as being stronger than helium, and lighter than air.

The word derives humorously from with the suffix , the conventional designation for a chemical element. It pre-dates the similar-sounding IUPAC systematic element names, such as ununennium. An alternative spelling, unobtanium is sometimes used (for example, for the crypto-currency Unobtanium), based on the spelling of metals such as titanium.

Since the late 1950s, aerospace engineers have used the term "unobtainium" when referring to unusual or costly materials, or when theoretically considering a material perfect for their needs in all respects, except that it does not exist. By the 1990s, the term was in wide use, even in formal engineering papers such as "Towards unobtainium [new composite materials for space applications]." The word unobtainium may well have been coined in the aerospace industry to refer to materials capable of withstanding the extreme temperatures expected in re-entry.Aerospace engineers are frequently tempted to design aircraft which require parts with strength or resilience beyond that of currently available materials.

Later, unobtainium became an engineering term for practical materials that really exist, but are difficult to get. For example, during the development of the SR-71 Blackbird spy plane, Lockheed engineers at the "Skunk Works" under Clarence "Kelly" Johnson used unobtainium as a dysphemism for titanium. Titanium allowed a higher strength-to-weight ratio at the high temperatures the Blackbird would reach, but the Soviet Union controlled its supply and was trying to deprive the US armed forces of this valuable resource.

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