« UNUM 3.1: Updated to Unicode 12.1.0, UTF-8 Support Added | Main | Reading List: Collapse »

Sunday, February 2, 2020

Reading List: Sonic Wind

Ryan, Craig. Sonic Wind. New York: Livewright Publishing, 2018. ISBN 978-0-631-49191-0.
Prior to the 1920s, most aircraft pilots had no means of escape in case of mechanical failure or accident. During World War I, one out of every eight combat pilots was shot down or killed in a crash. Germany experimented with cumbersome parachutes stored in bags in a compartment behind the pilot, but these often failed to deploy properly if the plane was in a spin or became tangled in the aircraft structure after deployment. Still, they did save the lives of a number of German pilots. (On the other hand, one of them was Hermann Göring.) Allied pilots were not issued parachutes because their commanders feared the loss of planes more than pilots, and worried pilots would jump rather than try to save a damaged plane.

From the start of World War II, military aircrews were routinely issued parachutes, and backpack or seat pack parachutes with ripcord deployment had become highly reliable. As the war progressed and aircraft performance rapidly increased, it became clear that although parachutes could save air crew, physically escaping from a damaged plane at high velocities and altitudes was a formidable problem. The U.S. P-51 Mustang, of which more than 15,000 were built, cruised at 580 km/hour and had a maximum speed of 700 km/hour. It was physically impossible for a pilot to escape from the cockpit into such a wind blast, and even if they managed to do so, they would likely be torn apart by collision with the fuselage or tail an instant later. A pilot's only hope was that the plane would slow to a speed at which escape was possible before crashing into the ground, bursting into flames, or disintegrating.

In 1944, when the Nazi Luftwaffe introduced the first operational jet fighter, the Messerschmitt Me 262, capable of 900 km/hour flight, they experimented with explosive-powered ejection seats, but never installed them in this front-line fighter. After the war, with each generation of jet fighters flying faster and higher than the previous, and supersonic performance becoming routine, ejection seats became standard equipment in fighter and high performance bomber aircraft, and saved many lives. Still, by the mid-1950s, one in four pilots who tried to eject was killed in the attempt. It was widely believed that the forces of blasting a pilot out of the cockpit, rapid deceleration by atmospheric friction, and wind blast at transonic and supersonic speeds were simply too much for the human body to endure. Some aircraft designers envisioned “escape capsules” in which the entire crew cabin would be ejected and recovered, but these systems were seen to be (and proved when tried) heavy and potentially unreliable.

John Paul Stapp's family came from the Hill Country of south central Texas, but he was born in Brazil in 1910 while his parents were Baptist missionaries there. After high school in Texas, he enrolled in Baylor University in Waco, initially studying music but then switching his major to pre-med. Upon graduation in 1931 with a major in zoology and minor in chemistry, he found that in the depths of the Depression there was no hope of affording medical school, so he enrolled in an M.A. program in biophysics, occasionally dining on pigeons he trapped on the roof of the biology building and grilled over Bunsen burners in the laboratory. He then entered a Ph.D. program in biophysics at the University of Texas, Austin, receiving his doctorate in 1940. Before leaving Austin, he was accepted by the medical school at the University of Minnesota, which promised him employment as a research assistant and instructor to fund his tuition.

In October 1940, with the possibility that war in Europe and the Pacific might entangle the country, the U.S. began military conscription. When the numbers were drawn from the fishbowl, Stapp's was 15th from the top. As a medical student, he received an initial deferment, but when it expired he joined the regular Army under a special program for medical students. While completing medical school, he would receive private's pay of US$ 32 a month (around US$7000 a year in today's money), which would help enormously with tuition and expenses. In December 1943 Stapp received his M.D. degree and passed the Minnesota medical board examination. He was commissioned as a second lieutenant in the Army Medical Corps and placed on suspended active duty for his internship in a hospital in Duluth, Minnesota, where he delivered 200 babies and assisted in 225 surgeries. He found he delighted in emergency and hands-on medicine. In the fall of 1944 he went on full active duty and began training in field medicine. After training, he was assigned as a medical officer at Lincoln Army Air Field in Nebraska, where he would combine graduate training with hospital work.

Stapp had been fascinated by aviation and the exploits of pioneers such as Charles Lindbergh and the stratospheric balloon explorers of the 1930s, and found working at an air base fascinating, sometimes arranging to ride along in training missions with crews he'd treated in the hospital. In April 1945 he was accepted by the Army School of Aviation Medicine in San Antonio, where he and his class of 150 received intense instruction in all aspects of human physiology relating to flight. After graduation and a variety of assignments as a medical officer, he was promoted to captain and invited to apply to the Aero Medical Laboratory at Wright Field in Dayton, Ohio for a research position in the Biophysics Branch. On the one hand, this was an ideal position for the intellectually curious Stapp, as it would combine his Ph.D. work and M.D. career. On the other, he had only eight months remaining in his service commitment, and he had long planned to leave the Army to pursue a career as a private physician. Stapp opted for the challenge and took the post at Wright.

Starting work, he was assigned to the pilot escape technology program as a “project engineer”. He protested, “I'm a doctor, not an engineer!”, but settled into the work and, being fluent in German, was assigned to review 1200 pages of captured German documents relating to crew ejection systems and their effects upon human subjects. Stapp was appalled by the Nazis' callous human experimentation, but, when informed that the Army intended to destroy the documents after his study was complete, took the initiative to preserve them, both for their scientific content and as evidence of the crimes of those whose research produced it.

The German research and the work of the branch in which Stapp worked had begun to persuade him that the human body was far more robust than had been assumed by aircraft designers and those exploring escape systems. It was well established by experiments in centrifuges at Wright and other laboratories that the maximum long-term human tolerance for acceleration (g-force) without special equipment or training was around six times that of Earth's gravity, or 6 g. Beyond that, subjects would lose consciousness, experience tissue damage due to lack of blood flow, or structural damage to the skeleton and/or internal organs. However, a pilot ejecting from a high performance aircraft experienced something entirely different from a subject riding in a centrifuge. Instead of a steady crush by, say, 6 g, the pilot would be subjected to much higher accelerations, perhaps on the order of 20—40 g, with an onset of acceleration (“jerk”) of 500 g per second. The initial blast of the mortar or rockets firing the seat out of the cockpit would be followed by a sharp pulse of deceleration as the pilot was braked from flight speed by air friction, during which he would be subjected to wind blast potentially ten times as strong as any hurricane. Was this survivable at all, and if so, what techniques and protective equipment might increase a pilot's chances of enduring the ordeal?

While pondering these problems and thinking about ways to research possible solutions under controlled conditions, Stapp undertook another challenge: providing supplemental oxygen to crews at very high altitudes. Stapp volunteered as a test subject as well as medical supervisor and began flight tests with a liquid oxygen breathing system on high altitude B-17 flights. Crews flying at these altitudes in unpressurised aircraft during World War II and afterward had frequently experienced symptoms similar to “the bends” (decompression sickness) which struck divers who ascended too quickly from deep waters. Stapp diagnosed the cause as identical: nitrogen dissolved in the blood coming out of solution as bubbles and pooling in joints and other bodily tissues. He devised a procedure of oxygen pre-breathing, where crews would breathe pure oxygen for half an hour before taking off on a high altitude mission, which completely eliminated the decompression symptoms. The identical procedure is used today by astronauts before they begin extravehicular activities in space suits using pure oxygen at low pressure.

From the German documents he studied, Stapp had become convinced that the tool he needed to study crew escape was a rocket propelled sled, running on rails, with a brake mechanism that could be adjusted to provide a precisely calibrated deceleration profile. When he learned that the Army was planning to build such a device at Muroc Army Air Base in California, he arranged to be put in charge of Project MX-981 with a charter to study the “effects of deceleration forces of high magnitude on man”. He arrived at Muroc in March 1947, along with eight crash test dummies to be used in the experiments. If Muroc (now Edwards Air Force Base) of the era was legendary for its Wild West accommodations (Chuck Yeager would not make his first supersonic flight there until October of that year), the North Base, where Stapp's project was located, was something out of Death Valley Days. When Stapp arrived to meet his team of contractors from Northrop Corporation they struck the always buttoned-down Stapp like a “band of pirates”. He also discovered the site had no electricity, no running water, no telephone, and no usable buildings. The Army, preoccupied with its glamourous high speed aviation projects, had neither interest in what amounted to a rocket powered train with a very short track, nor much inclination to provide it the necessary resources. Stapp commenced what he came to call the Battle of Muroc, mastering the ancient military art of scrounging and exchanging favours to get the material he needed and the work done.

As he settled in at Muroc and became acquainted with his fellow denizens of the desert, he was appalled to learn that the Army provided medical care only for active duty personnel, and that civilian contractors and families of servicemen, even the exalted test pilots, had to drive 45 miles to the nearest clinic. He began to provide informal medical care to all comers, often making house calls in the evening hours on his wheezing scooter, in return for home cooked dinners. This built up a network of people who owed him favours, which he was ready to call in when he needed something. He called this the “Curbstone Clinic”, and would continue the practice throughout his career. After some shaky starts and spectacular failures due to unreliable surplus JATO rockets, the equipment was ready to begin experiments with crash test dummies.

Stapp had always intended that the tests with dummies would be simply a qualification phase for later tests with human and animal subjects, and he would ask no volunteer to do something he wouldn't try himself. Starting in December, 1947, Stapp personally made increasingly ambitious runs on the sled, starting at “only” 10 g deceleration and building to 35 g with an onset jerk of 1000 g/second. The runs left him dizzy and aching, but very much alive and quick to recover. Although far from approximating the conditions of ejection from a supersonic fighter, he had already demonstrated that the Air Force's requirements for cockpit seats and crew restraints, often designed around a 6 g maximum shock, were inadequate and deadly. Stapp was about to start making waves, and some of the push-back would be daunting. He was ordered to cease all human experimentation for at least three months.

Many Air Force officers (for the Air Force had been founded in September 1947 and taken charge of the base) would have saluted and returned to testing with instrumented dummies. Stapp, instead, figured out how to obtain thirty adult chimpanzees, along with the facilities needed to house and feed them, and resumed his testing, with anæsthetised animals, up to the limits of survival. Stapp was, and remained throughout his career, a strong advocate for the value of animal experimentation. It was a grim business, but at the time Muroc was frequently losing test pilots at the rate of one a week, and Stapp believed that many of these fatalities were unnecessary and could be avoided with proper escape and survival equipment, which could only be qualified through animal and cautious human experimentation.

By September 1949, approval to resume human testing was given, and Stapp prepared for new, more ambitious runs, with the subject facing forward on the sled instead of backward as before, which would more accurately simulate the forces in an ejection or crash and expose him directly to air blast. He rapidly ramped up the runs, reaching 32 g without permanent injury. To avoid alarm on the part of his superiors in Dayton, a “slight error” was introduced in the reports he sent: all g loads from the runs were accidentally divided by two.

Meanwhile, Stapp was ramping up his lobbying for safer seats in Air Force transport planes, arguing that the existing 6 g forward facing seats and belts were next to useless in many survivable crashes. Finally, with the support of twenty Air Force generals, in 1950 the Air Force adopted a new rear-facing standard seat and belt rated for 16 g which weighed only two pounds more than those it replaced. The 16 g requirement (although not the rearward-facing orientation, which proved unacceptable to paying customers) remains the standard for airliner seats today, seven decades later.

In June, 1951, Stapp made his final run on the MX-981 sled at what was now Edwards Air Force Base, decelerating from 180 miles per hour (290 km/h) to zero in 31 feet (9.45 metres), at 45.4 g, a force comparable to many aircraft and automobile accidents. The limits of the 2000 foot track (and the human body) had been reached. But Stapp was not done: the frontier of higher speeds remained. Shortly thereafter, he was promoted to lieutenant colonel and given command of what was called the Special Projects Section of the Biophysics Branch of the Aero Medical Laboratory. He was reassigned to Holloman Air Force Base in New Mexico, where the Air Force was expanding its existing 3500 foot rocket sled track to 15,000 feet (4.6 km), allowing testing at supersonic speeds. (The Holloman High Speed Test Track remains in service today, having been extended in a series of upgrades over the years to a total of 50,917 feet (15.5 km) and a maximum speed of Mach 8.6, or 2.9 km/sec [6453 miles per hour].)

Northrop was also contractor for the Holloman sled, and devised a water brake system which would be more reliable and permit any desired deceleration profile to be configured for a test. An upgraded instrumentation system would record photographic and acceleration measurements with much better precision than anything at Edwards. The new sled was believed to be easily capable of supersonic speeds and was named Sonic Wind. By March 1954, the preliminary testing was complete and Stapp boarded the sled. He experienced a 12 g acceleration to the peak speed of 421 miles per hour, then 22 g deceleration to a full stop, all in less than eight seconds. He walked away, albeit a little wobbly. He had easily broken the previous land speed record of 402 miles per hour and become “the fastest man on Earth.” But he was not done.

On December 10th, 1954, Stapp rode Sonic Wind, powered by nine solid rocket motors. Five seconds later, he was travelling at 639 miles per hour, faster than the .45 ACP round fired by the M1911A1 service pistol he was issued as an officer, around Mach 0.85 at the elevation of Holloman. The water brakes brought him to a stop in 1.37 seconds, a deceleration of 46.2 g. He survived, walked away (albeit just few steps to the ambulance), and although suffering from vision problems for some time afterward, experienced no lasting consequences. It was estimated that the forces he survived were equivalent to those from ejecting at an altitude of 36,000 feet from an airplane travelling at 1800 miles per hour (Mach 2.7). As this was faster than any plane the Air Force had in service or on the drawing board, he proved that, given a suitable ejection seat, restraints, and survival equipment, pilots could escape and survive even under these extreme circumstances. The Big Run, as it came to be called, would be Stapp's last ride on a rocket sled and the last human experiment on the Holloman track. He had achieved the goal he set for himself in 1947: to demonstrate that crew survival in high performance aircraft accidents was a matter of creative and careful engineering, not the limits of the human body. The manned land speed record set on the Big Run would stand until October 1983, when Richard Noble's jet powered Thrust2 car set a new record of 650.88 miles per hour in the Nevada desert. Stapp remarked at the time that Noble had gone faster but had not, however, stopped from that speed in less than a second and a half.

From the early days of Stapp's work on human tolerance to deceleration, he was acutely aware that the forces experienced by air crew in crashes were essentially identical to those in automobile accidents. As a physician interested in public health issues, he had noted that the Air Force was losing more personnel killed in car crashes than in airplane accidents. When the Military Air Transport Service (MATS) adopted his recommendation and installed 16 g aft-facing seats in its planes, deaths and injuries from crashes had fallen by two-thirds. By the mid 1950s, the U.S. was suffering around 35,000 fatalities per year in automobile accidents—comparable to a medium-sized war—year in and year out, yet next to nothing had been done to make automobiles crash resistant and protect their occupants in case of an accident. Even the simplest precaution of providing lap belts, standard in aviation for decades, had not been taken; seats were prone to come loose and fly forward even in mild impacts; steering columns and dashboards seemed almost designed to impale drivers and passengers; and “safety” glass often shredded the flesh of those projected through it in a collision.

In 1954, Stapp turned some of his celebrity as the fastest man on Earth toward the issue of automobile safety and organised, in conjunction with the Society of Automotive Engineers (SAE), the first Automobile Crash Research Field Demonstration and Conference, which was attended by representatives of all of the major auto manufacturers, medical professional societies, and public health researchers. Stapp and the SAE insisted that the press be excluded: he wanted engineers from the automakers free to speak without fear their candid statements about the safety of their employers' products would be reported sensationally. Stapp conducted a demonstration in which a car was towed into a fixed barrier at 40 miles an hour with two dummies wearing restraints and two others just sitting in the seats. The belted dummies would have walked away, while the others flew into the barrier and would have almost certainly been killed. It was at this conference that many of the attendees first heard the term “second collision”. In car crashes, it was often not the crash of the car into another car or a barrier that killed the occupants: it was their colliding with dangerous items within the vehicle after flying loose following the initial impact.

Despite keeping the conference out of the press, word of Stapp's vocal advocacy of automobile safety quickly reached the auto manufacturers, who were concerned both about the marketing impact of the public becoming aware not only of the high level of deaths on the highways but also the inherent (and unnecessary) danger of their products to those who bought them, and also the bottom-line impact of potential government-imposed safety mandates. Auto state congressmen got the message, and the Air Force heard it from them: the Air Force threatened to zero out aeromedical research funding unless car crash testing was terminated. It was.

Still, the conferences continued (they would eventually be renamed “Stapp Car Crash Conferences”), and Stapp became a regular witness before congressional committees investigating automobile safety. Testifying about whether it was appropriate for Air Force funds to be used in studying car crashes, in 1957 he said, “I have done autopsies on aircrew members who died in airplane crashes. I have also performed autopsies on aircrew members who died in car crashes. The only conclusion I could come to is that they were just as dead after a car crash as they were after an airplane crash.” He went on to note that simply mandating seatbelts in Air Force ground vehicles would save around 125 lives a year, and if they were installed and used by the occupants of all cars in the U.S., around 20,000 lives—more than half the death toll—could be saved. When he appeared before congress, he bore not only the credentials of a medical doctor, Ph.D. in biophysics, Air Force colonel, but the man who had survived more violent decelerations equivalent to a car crash than any other human.

It was not until the 1960s that a series of mandates were adopted in the U.S. which required seat belts, first in the front seat and eventually for all passengers. Testifying in 1963 at a hearing to establish a National Accident Prevention Center, Stapp noted that the Air Force, which had already adopted and required the use of seat belts, had reduced fatalities in ground vehicle accidents by 50% with savings estimated at US$ 12 million per year. In September 1966, President Lyndon Johnson signed two bills, the National Traffic and Motor Vehicle Safety Act and the Highway Safety Act, creating federal agencies to research vehicle safety and mandate standards. Standing behind the president was Colonel John Paul Stapp: the long battle was, if not won, at least joined.

Stapp had hoped for a final promotion to flag rank before retirement, but concluded he had stepped on too many toes and ignored too many Pentagon directives during his career to ever wear that star. In 1967, he was loaned by the Air Force to the National Highway Traffic Safety Administration to continue his auto safety research. He retired from the Air Force in 1970 with the rank of full colonel and in 1973 left what he had come to call the “District of Corruption” to return to New Mexico. He continued to attend and participate in the Stapp Car Crash Conferences, his last being the Forty-Third in 1999. He died at his home in Alamogordo, New Mexico in November that year at the age of 89.

In his later years, John Paul Stapp referred to the survivors of car crashes who would have died without the equipment designed and eventually mandated because of his research as “the ghosts that never happened”. In 1947, when Stapp began his research on deceleration and crash survival, motor vehicle deaths in the U.S. were 8.41 per 100 million vehicle miles travelled (VMT). When he retired from the Air Force in 1970, after adoption of the first round of seat belt and auto design standards, they had fallen to 4.74 (which covers the entire fleet, many of which were made before the adoption of the new standards). At the time of his death in 1999, fatalities per 100 million VMT were 1.55, an improvement in safety of more than a factor of five. Now, Stapp was not solely responsible for this, but it was his putting his own life on the line which showed that crashes many considered “unsurvivable” were nothing of the sort with proper engineering and knowledge of human physiology. There are thousands of aircrew and tens or hundreds of thousands of “ghosts that never happened” who owe their lives to John Paul Stapp. Maybe you know one; maybe you are one. It's worth a moment remembering and giving thanks to the largely forgotten man who saved them.

Posted at February 2, 2020 17:00