In the week NASA’s Perseverance rover landed on Mars, Birlinn MD Hugh Andrew looks at another case of long-range perseverance with a NASA connection, the story of the Stirling Engine and the mission to the furthest reaches of the solar system.
Robert Stirling was a Scottish Minister who in 1816 – we don’t know how or why he came up with the idea – patented a revolutionary hot air engine, powered solely by heat. Nothing in his education or background gave any clue as to the remarkable engine he then tried to build. The engine worked – but at only a fraction of its potential because the engineering required to build the engine was way beyond anything 19th century technology could muster. Indeed it was way beyond anything most 20th century technology could bring to bear. It was only at the end of that century, when another genius, William Beales, turned his mind to it, that the technical issues were triumphantly resolved and the Stirling engine could take its rightful place as the staggering feat of imagination and technology that it is.
There are many remarkable twists and turns to this story – not least that Stirling was working with an antiquated theory of heat we now know to be wrong, not least that he added on to his engine something called the Regenerator which he instinctively knew improved it without any idea of how. Indeed the mystery of the Regenerator has only recently been solved using the latest mathematical techniques. Stirling in one sense did not ‘understand’ his engine or its workings, he ‘intuited’ it. Following his death the engine was taken up by a number of other geniuses, all extraordinary characters. Leading them were Sir George Cayley – a Yorkshire baronet in the early 19th century who singlehandedly invented the principles of aviation and would have had a working flying machine generations before the Wright brothers if only he had had a power plant to make it work. And then there was John Ericksson, maverick genius who in the Monitor invented the iron warship and changed the course of naval history. (Its famous duel with the Merrimac arguably changed the course of the American Civil War). Many others followed, but all came up against the same hurdle: turning the visionary idea into a practical project at an affordable cost within the limits of the technology with which they had to work.
As the 19th century ended and the 20th century began a new wonder-fuel once again drove the Stirling engine into the background – carbon. It was plentiful, cheap and filthy but that seemed not to matter. We ran our ships, powered our cars, and heated our houses with it. It is now the year 2020 and we are seeing around us in scenes of environmental disaster the terrible consequences of a carbon-driven economy powered by astonishingly inefficient engines. But Beales’s revolution has finally resolved the problems that plagued Stirling’s extraordinary engine. For NASA it is the engine that will take mankind to the stars. Using fuel far more efficiently than any competitor, immensely flexible, capable of being fuelled and running for years without maintenance, is the this the age when the Stirling engine will come into its own? Beales, its latter day visionary, certainly thought so.
Amongst Stirling’s many interests was astronomy. At the end of his life he and a friend shared a small observatory to observe the stars. It is both moving and fitting that it was his brilliant idea that led to the engine that may both lie at the heart of saving our planet and taking mankind out into the universe. On Mars now sits the most sophisticated machine man has put onto another planet. In a few decades could it be that mankind will have settled on Mars, powered by NASA’s KRUSTY (Kilowatt Reactor Using Stirling TechnologY) reactors with ships sailing the heavens powered by variants of those same Stirling engines?
Birlinn will publish The Star Drive: The True Story of a Genius, an Engine and our Future by Pip Hills in August 2021