Unobtainium

Thus the invention of high temperature fuels will enable us to consider cores which are radiation cooled; such cores would be surrounded by large tanks (cooled by water) which in turn would be penetrated by beam holes. The beam holes themselves would probably have to be made of "unobtanium". (This "unobtanium" is a word coined at Atomics International to describe the material needed to make reactor projects feasible.) In between the radiation cooled reactors and the water cooled reactors is a regime suitable for liquid metal (including boiling liquid) cooled reactors. Once again "unobtanium" is needed.

In order to illustrate some of the features of data processing under ideal conditions, a set of simulated data was generated and is presented in the last four columns of Table II. The hypothetical material is called Unobtainium.

The names of materials presently used in aerospace applications are familiar: magnesium, aluminum, titanium, and so on. Propulsion scientists call the ideal material for turbine engines "Unobtainium," because it does not exist.

As early as 1969, during the initial Phase A studies, Lockheed had taken the initiative in proposing a two-stage fully-reusable design with both stages built of aluminum and using silica tiles for thermal protection. [...] Though that company indeed was in the forefront in developing such tiles, they were items for laboratory research. A design that specified their use had no more intrinsic credibility than one that proposed to use the miracle metals Unobtanium and Wishalloy.

This is not a Tom Tomorrow Bike, made of NASA unobtainiums and employing warp drives that have yet to be invented. It could be built as soon as the production technology is put on the line and powered-up, because all the vehicle technology is proven, off-the-shelf stuff.

The vacuum furnace has been greatly improved and today we are melting titanium, zirconium, high alloy steels and other materials which are remarkably free of impurities and possess improved properties. These high performance metals are used in turbojet engines, missiles and atomic reactors. […] We call it "unobtainium."

Bikes made of titanium, once known as "unobtainium" because of its high price, are down from the stratosphere.

Sometimes parts turn out to be made of "unobtainium," that magic element which is simply unobtainable.