Photo: U.S. Air Force
The rocket sled is a system that was made to experiment with G-forces in the fifties.In its simplest form, a rocket sled consists of a chair attached to a sled on a long stretch of railroad track with a rocket engine strapped to the back. The rocket ignites, the sled fires forward, the chair and occupant go along for the ride.
Some of the classic adages about reliability, technology and dependability were coined by the men who either climbed in or analysed the sleds, including “Murphy’s Law” and “Stapp’s Law.”
Aerospace conventional wisdom up to the late forties held that human beings could only withstand forces up to around 18 g-forces without dying. Colonel John Stapp, a doctor in the newly-formed Air Force, set out to prove this was nonsense.
The railroad track at Muroc Army Air Field -- now Edwards Air Force Base -- was 2,000 feet long with a 45 foot hydraulic breaking system. It was originally designed to test the German V-1 rocket. The sled weighed 1,500 lbs, could hold a person and had room for a number of rocket engines in the rear.
At first the Gee Whiz was tested with a crash test dummy, known as Oscar Eightball. Eightball would suffer a violent ejection that sent him flying 700 feet, as well as other work-related 'injuries.'
These problems were fixed, however, and then they strapped a chimpanzee in the seat.
Finally they needed a human volunteer.
After 35 unmanned test runs, John Stapp himself rode the sled with a single rocket propelling it, hitting 10 Gs of force in the process.
He was hooked.
Within months, Stapp had hit 35 Gs of force, blowing away the previously believed 18 G fatality point. The research changed the way aeroplanes were designed nearly immediately, accounting for additional safety measures and new capabilities.
Captain Ed Murphy, an Air Force Engineer, briefly came out to Edwards Air Force base to try to test some sensors he had created on the sled run. He believed that they would grant quantifiable insight into the amount of force applied to Stapp during deceleration.
An assistant installed the sensors on the restraints and -- while the exact details of the event remain contested -- something went wrong.
From here on out, keep in mind that the story has been told and retold from a number of different people and is likely full of apocrypha, rumour, and different people taking credit. Here's the most consistent story we could find, with all the dubious bits excised.
By either malfunction, mistakes in wiring, or an error setting the system up, the gauges that Murphy had installed had no readout after Stapp's run on the sled.
At that point, Murphy -- either out of anger at the assistant who configured the device or as a commentary on engineering and design -- said something to the nature of 'If there's any way they can do it wrong, they will,' according to a witness.
After a test failure, the result was spread around the staff rather quickly. Murphy's sensor failure and subsequent quip were no exception. The notion was eventually distilled to a catchier 'If anything can go wrong, it will.'
The team began applying it as a maxim in favour of defensive design, a wry 'expect the unexpected' of engineering. Some have attributed the popularity to Stapp, a prolific coiner of phrases at the time, but it was indelibly ascribed to Murphy.
The key moment where it entered the mainstream was at a press conference Stapp was holding. When asked how such dangerous testing had never caused a fatality, Stapp commented that he and his team always kept Murphy's Law in mind when working, and planned to prevent mistakes. The rest is history.
Colonel Stapp was himself a prolific coiner of phrases, and is said to have been the true push behind Murphy's Law. Either way, Stapp's Law, written during the rocket sled tests, states that 'The universal aptitude for ineptitude makes any human accomplishment an incredible miracle.'
Murphy would go on to work for various private contractors over the course of his successful career in aerospace engineering. He worked on the crew escape systems of many of the experimental aircraft developed during the Cold War.
He worked on the F-4 Phantom II, the SR-71 Blackbird, the B-1 Lancer, life support systems for the Apollo missions, and some work on the Apache helicopter.
Stapp would go on to hit 46 Gs of force on his final run, hitting 632 miles per hour and claiming the title of the 'Fastest Man Alive.' By that point, his eyes were bleeding and he nearly blacked out. Needless to say, the previous notion of G force limit was long gone.
He would go on to advocate for seat belts in cars. After his long career as a human crash test dummy, Stapp would stand in the room with Ralph Nader when Lyndon B. Johnson signed the bill that made seat belts mandatory in vehicles. His work provided the hard science behind future tests of instant deceleration.
Stapp would later be inducted into both the National and International Aviation Halls of Fame for his work on G forces.
Murphy's son has deflected against the more humorous uses of the phrase, arguing that it remains prudent design protocol. The adage has gone on to spawn possibly hundreds of similar named laws, many of which similarly ironically observe the perverse logic of the universe.
Murphy died in 1990 at the age of 72.
Stapp, despite the then-unheard of forces his fragile body voluntarily endured, would go on to live to the age of 89, dying in his home due to natural causes. A foundation in his honour is funded in part by GM and gives scholarships to promising automotive engineers.
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