“It almost looks like perpetual motion.” – Quote about a working Nitinol Engine. One of the memorable things reported at the famous crash in Roswell, New Mexico in 1947 of, supposedly, one or more flying disks, was a super light weight very strong material that returned to its original shape when bent.
Major Jesse Marcel, who everyone – believers and doubters – acknowledges was at the crash site, said decades later: “I saw a lot of wreckage but no complete machine. It had disintegrated before it hit the ground. The wreckage was scattered over an area about three quarters of a mile long and several hundred feet wide. I was pretty well acquainted with most everything that was in the air at that time, both ours and foreign. I was also acquainted with virtually every type of weather-balloon or radar-tracking device being used by either the civilians or the military. What it was we didn’t know. We just picked up the fragments…it certainly wasn’t anything built by us.” …
– via Mysterious Universe
The reports I’ve read and heard said the amazing light weight material with shape memory could not be destroyed by heat. No one has presented solid proof of these claims, but today we have more than 20 metal alloys with shape memory. One of the most interesting is Nitinol.
The nickel-titanium alloys were first developed in 1962–1963 by the United States Naval Ordnance Laboratory and commercialized under the trade name Nitinol (an acronym for Nickel Titanium Naval Ordnance Laboratories). Their remarkable properties were discovered by accident. A sample that was bent out of shape many times was presented at a laboratory management meeting. One of the associate technical directors, Dr. David S. Muzzey, decided to see what would happen if the sample was subjected to heat and held his pipe lighter underneath it. To everyone’s amazement the sample stretched back to its original shape.
Shape memory is the ability of nitinol to undergo deformation at one temperature, then recover its original, undeformed shape upon heating above its “transformation temperature”. Superelasticity occurs at a narrow temperature range just above its transformation temperature; in this case, no heating is necessary to cause the undeformed shape to recover, and the material exhibits enormous elasticity, some 10-30 times that of ordinary metal.
The thing that motivated this post was an idea that was new to me, using the shape changes Nitinol makes as a power source. This could work anywhere you have a reasonable heat differential. Impressively, the force of Nitinol’s shape return is described in the following video as being up to 55 tons per square inch. That’s serious. Even stranger, Nitinol wires get stronger the more they are used, developing a double memory, one shape for one temperature and another shape for a different temperature. Just cycling Nitinol between two different temperatures, then, could make it work as a force to turn a generator. In fact, here is a video of a 5- Megawatt Nitinol Engine once being developed by Mcdonnell Douglas.
Nearly 2/3 of energy generated is currently lost to waste heat. This could be reclaimed by Nitinol engines. The material can be produced at about $200/lb so the video says a Nitinol engine would pay for itself after about 2 years of continuous operation for electricity generation.
This video shows a Nitinol engine in action. Nitinol represents first time heat has been converted directly to mechanical energy.
Nickel and titanium are both very common elements and Nitinol is “not hard to make” according to one person in the video. Wikipedia disagrees, saying:
“Nitinol is exceedingly difficult to make, due to the exceptionally tight compositional control required, and the tremendous reactivity of titanium. Every atom of titanium that combines with oxygen or carbon is an atom that is robbed from the NiTi lattice, thus shifting the composition and making the transformation temperature that much lower.”