Necessity is the mother of invention, as Plato is widely quoted as saying, although, in my opinion, breakthroughs in design more often come about by existing materials being used in untried ways.
Take the evolution of land speed records, which have captured the public’s imagination from George Stephenson’s 1829 Rocket to Richard Noble’s 1997 Thrust SSC (the first supersonic car), and his plan to break the 1,000mph barrier with Bloodhound SSC in 2011. The materials used in Rocket, such as wood, copper, brass, cast iron and steel, were not particularly new at the time, but what was different was how Stephenson applied them.
For the first time a multi-tube boiler, comprising 25 copper pipes, drew heated exhaust from the firebox, vastly improving the heat transfer compared to single pipe designs. A blast pipe, feeding the exhaust steam from the cylinders into the base of the chimney, so as to induce a partial vacuum and pull air through the fire, also worked better. Single-tube boilers created too much suction and tended to shower burning cinders from the chimney. The angled steam cylinders improved stability compared to a vertical orientation, and developed into the horizontal orientation that became the standard for all steam locomotives.
Other features, such as a wooden cask to hold the water supply, steel-rimmed wooden wheels and a tall, iron chimney, were hardly new for the period. At nearly six tons, including the tender, weight reduction was clearly not a priority. But Rocket still reached a then record-breaking 30mph unladen.
Rocket was designed to win the competition set by the board of the Liverpool and Manchester Railway Company to determine the best means of powering locomotives on their newly opened railway. What would Stephenson have made of today’s land speed record that exists simply for the technical challenge of breaking it, and, more specifically, the Bloodhound SSC record attempt?
Apart from the concept of supersonic velocity, which was not a known phenomena in the early 1800s, he would not recognise most of the materials. Unlike Rocket, power-to-weight ratio in Bloodhound is critical. It requires high strength-to-weight materials like titanium wheels and carbon fibre composite body panels, not to mention Teflon and aluminium to contain the rocket fuel oxidiser.
One irony that I think would have struck him is that, unlike Rocket which was fuelled by coal, Bloodhound really will have rocket propulsion using a synthetic rubber hydroxyl-terminated polybutadiene as the primary fuel. I am also certain he would agree that projects like Rocket and Bloodhound do not just make technical breakthroughs, they also inspire the public and young people to take up careers in science and engineering.
If society is to meet the conflicting challenges of secure, sustainable, low cost and low carbon energy, this really is a necessity.