Yesterday 05:54 PM
(This post was last modified: Yesterday 05:59 PM by C C.)
https://www.popsci.com/technology/plane-...paceplane/
EXCERPTS: Because Earth’s atmosphere doesn’t have an abrupt end—it just thins until traces of it drift past the moon—von Kármán offered a practical demarcation point. A wing works by pushing air down; the thinner the atmosphere, the faster the wing must move to push enough of it. Climb high enough, von Kármán reasoned, and a wing would have to fly so fast to hold its own weight up that it would already be traveling at orbital speed—roughly 17,500 miles per hour at the bottom of low Earth orbit, or 100 miles above the surface. At that velocity, a wing becomes moot. The object isn’t being held aloft by air pressure at all; it’s continuously falling, tugged by Earth’s gravity, but moving sideways fast enough to keep missing Earth. Too slow and it spirals back down; too fast and it sails off into space.
Von Kármán calculated that crossover at around 50 miles up, though the number drifts with fluctuations in atmospheric density. In the 1960s, the Fédération Aéronautique Internationale rounded it to 100 kilometers, or 62 miles. NASA and the Air Force still use 50 miles. Regardless of the precise figure, it has become known as the edge of space, a turbulent shoreline where the physics of flying shift dramatically. Although no treaty has ever made it official, the Kármán line serves as the conventional divide between aviation law and space law, where wings serve no purpose in keeping an object aloft—only speed matters.
Getting to space requires altitude, but staying there requires speed. The gap between them is where the dream of the spaceplane has always faltered, beginning with the novel machine Crossfield helped design in the 1950s.
[...] A cross between a rocket and a plane, the engineers building the X-15 called it a “missile with a cockpit,” Griswold reported in a 1958 preview for Popular Science. Like a rocket, the plane was mostly a fuel tank. Like a plane, its stubby wings and tail fins enabled it to negotiate Earth’s atmosphere. The vessel’s most telling feature, however, was its twin sets of flight controls: one for navigating air, the other for space. As the plane approached the Kármán line, the pilot switched from traditional airplane controls to jets of superheated steam in the nose and wings, pointing the airplane with thrusters, just like a spacecraft.
[...] Air Force pilot Bob White took the X-15 to space first, reaching 314,750 feet in July 1962, earning the first astronaut wings ever awarded to a winged aircraft pilot. NASA pilot Joe Walker flew the X-15 to 354,200 feet in August 1963—67 miles up, an altitude no winged aircraft has beaten, and one of only two X-15 flights to clear the Kármán line. Air Force pilot Pete Knight pushed the X-15 to Mach 6.7 in October 1967, still the fastest a piloted airplane has ever flown. In all, 13 flights crossed 50 miles—space’s threshold by NASA’s standards. Eight pilots earned astronaut wings, among them a NASA research pilot named Neil Armstrong... (MORE - details)
EXCERPTS: Because Earth’s atmosphere doesn’t have an abrupt end—it just thins until traces of it drift past the moon—von Kármán offered a practical demarcation point. A wing works by pushing air down; the thinner the atmosphere, the faster the wing must move to push enough of it. Climb high enough, von Kármán reasoned, and a wing would have to fly so fast to hold its own weight up that it would already be traveling at orbital speed—roughly 17,500 miles per hour at the bottom of low Earth orbit, or 100 miles above the surface. At that velocity, a wing becomes moot. The object isn’t being held aloft by air pressure at all; it’s continuously falling, tugged by Earth’s gravity, but moving sideways fast enough to keep missing Earth. Too slow and it spirals back down; too fast and it sails off into space.
Von Kármán calculated that crossover at around 50 miles up, though the number drifts with fluctuations in atmospheric density. In the 1960s, the Fédération Aéronautique Internationale rounded it to 100 kilometers, or 62 miles. NASA and the Air Force still use 50 miles. Regardless of the precise figure, it has become known as the edge of space, a turbulent shoreline where the physics of flying shift dramatically. Although no treaty has ever made it official, the Kármán line serves as the conventional divide between aviation law and space law, where wings serve no purpose in keeping an object aloft—only speed matters.
Getting to space requires altitude, but staying there requires speed. The gap between them is where the dream of the spaceplane has always faltered, beginning with the novel machine Crossfield helped design in the 1950s.
[...] A cross between a rocket and a plane, the engineers building the X-15 called it a “missile with a cockpit,” Griswold reported in a 1958 preview for Popular Science. Like a rocket, the plane was mostly a fuel tank. Like a plane, its stubby wings and tail fins enabled it to negotiate Earth’s atmosphere. The vessel’s most telling feature, however, was its twin sets of flight controls: one for navigating air, the other for space. As the plane approached the Kármán line, the pilot switched from traditional airplane controls to jets of superheated steam in the nose and wings, pointing the airplane with thrusters, just like a spacecraft.
[...] Air Force pilot Bob White took the X-15 to space first, reaching 314,750 feet in July 1962, earning the first astronaut wings ever awarded to a winged aircraft pilot. NASA pilot Joe Walker flew the X-15 to 354,200 feet in August 1963—67 miles up, an altitude no winged aircraft has beaten, and one of only two X-15 flights to clear the Kármán line. Air Force pilot Pete Knight pushed the X-15 to Mach 6.7 in October 1967, still the fastest a piloted airplane has ever flown. In all, 13 flights crossed 50 miles—space’s threshold by NASA’s standards. Eight pilots earned astronaut wings, among them a NASA research pilot named Neil Armstrong... (MORE - details)
