Law of the Third Best

Systems architects and systems engineers charged with bringing a new capability into successful operation must decide what strategy to follow to select from possible technology/design approaches. On major efforts, such as the Spacefaring America Initiative will be, there will a plethora of ideas proposed. These will range from the use of existing solutions to truly fanciful ideas. What strategy to use to select from the range of choices is the first and one of the most important decisions the systems architect and systems engineering team will make. Here, history provides valuable guidance.

During World War I, using dirigibles, Germany attacked England from the air. As these dirigibles could fly higher than many of the military fighter aircraft of the day, they were somewhat invulnerable to attack giving them free reign to attack England. Especially at night, this was a significant threat. Eventually, capabilities were developed to counter this threat—superchargers for the engines and tracer rounds for the guns—but England was sensitized to the threat of air attacks.

In the years leading up to World War II, as military aircraft improved, the revitalized German air force began to develop longer-range bombers. To be able to counter the threat they posed, the ability to detect the incoming bombers prior to their arrival was needed. This was necessary to enable fighter aircraft to be scrambled to climb and intercept the bombers. At that time, the only way to detect bombers was to see or hear them. Despite attempts to improve on this capability, they were not able to reach needed performance. A British engineer, Sir Robert Watson-Watt, was charged with finding a better solution based on his earlier research into using radio transmission and reception to detect aircraft at a distance—England’s first early-warning radar system against air attack.  In describing how he was successful in developing this system in a short period of time, he outlined what has come to be called Watson-Watt’s “Law of the Third Best”. This provides a rationale for logically selecting between technological alternatives. Every systems architect and systems engineer should understand and practice this law.