While Major suffered from G lock, the symptoms of hypoxia didn't end his life. Instead, it was the ultimate impact with the ground. Impacts are deadly because they take the concepts of force we've already learned about, and take them even further rather than constant accelerations for long periods of time. Rapid accelerations in very short amounts of time produce force is so strong that they produce trauma. These forces, when applied to the human body, will break bones and cartilage and then crush soft tissue organs. To best understand this concept, let's go back to the equation of force and acceleration. Force equals mass times acceleration. If we remember that, slowing down is still acceleration just in the negative direction. Then slowing down also requires a force going opposite the direction of movement. When you're traveling at hundreds or thousands of miles per hour possible in a jet craft, suddenly slowing down is a major life threat. If we consider a car crash without a seat belt, the crash will send you flying into your windshield, and your head will collide with the windshield or the brick wall in front of your car, causing the rest of your body to suddenly stop. Your head will need to bear the full force of the crash to stop your whole body. If you're slowing down from 65 mph to zero in the span of point.one seconds, that is a negative acceleration in the Z direction of 30GS. For the average person weighing roughly 150 lb. That means your skull is experiencing 25,000 newtons of force in that point one seconds. The femur, the longest bone in the body found in the leg will be crushed by 4000 Newtons. The much less strong frontal bone of the human skull will have a 50% chance of fracturing at a force of 2000 newtons. So at these extremes, trauma is inevitable as the hard bones which protect the other organs are cracked, and then the necessary lungs. Heart, brain and spine are irreversibly destroyed. The arteries and veins of the circulatory system may even be destroyed, leading to blood loss and hypovolemic shock. When crashes are experienced, There are two ways to mitigate the worst of the trauma impact attenuation and head and neck restraints. The first impact attenuation involves decelerating the person over a longer period of time, thinking back to the car crash. If we can make the crash take just one second, the acceleration and force will be cut down by a factor of ten. In cars we achieve this attenuation with airbags, and an aluminum frame air bags give you a soft object to sink into rather than a rigid metal, which allows for more time to slow to a stop. Modern cars are made with aluminum frames and bumpers which will crumple so that the crash will take longer, compared to a steel frame heavyweight from the 1950s. Your car will be ruined, but you will have a much higher chance of survival. The other major component is head and neck restraints, or in other words, seatbelts. Seatbelts first work by applying a force to the whole chest rather than the delicate head, neck and spine. They also distribute the force over a whole region of the body, rather than a single point in the skull, having to experience all the force of deceleration. Why is the neck and spine so important to protect? Well damage to the neck and spine can lead to neurogenic shock, where the spine cannot provide a signal to the arteries to remain vasoconstricted. Accordingly the whole body vasodilates and a massive drop in blood pressure occurs often irreversibly. This special form of distributive shock is called neurogenic shock. Now, thinking to aerospace, the same rules apply for a car crash except the speeds are increased. A jet craft breaking the sound barrier will exceed speeds of 767 mph or 12 times the car crash scenario. Air Force pilots utilize seatbelts, cushion seats and are additionally trained to conduct emergency landings that land at shallow angles, that ensure that the crash landings take as long as possible. If the inevitable landing is too sudden or too fast, an ejection seat with parachutes become necessary. Major G lock meant that despite his training, he was not able to adjust or eject in time, resulting in a fatal crash. Finally, spacecrafts will most often see deceleration during landing and missions maximize the time it takes to land The Orion spacecraft. The plan return capsule for the Artemus missions to the moon are designed to slow down from 25,000 mph while traveling in space. Which is nearly 400 times faster than a hypothetical car to have a safe landing in the ocean. To achieve this incredible feat, Orion will enter Earth's atmosphere, Which provides resistance in the form of drag across several minutes to slowly bring the Orion capsule down to 300 mph. At this speed, 11 parachutes are deployed, slowing the descent down to 20 mph before a safe water landing can occur. In this way, impact attenuation is used and accelerations and forces are never massive. During this whole process, the astronauts will be wearing their seatbelts and helmets for further safety. This process is survivable because it takes minutes to hours rather than seconds, illustrating that the difference between a dangerous landing and a safe one is just more time
