[Image Courtesy of NASA]
The space shuttle, officially named the Space Transportation System (STS) is perhaps the most magnificent engineering marvel that humanity has ever created. The program was launched shortly after President Nixon announced NASA’s plan to develop a reusable space shuttle or space transportation system (STS). The plan prompted a massive overhaul of the Apollo program to develop a technology capable of resisting the intense heat and stress aircraft experience as they reenter Earth’s atmosphere while preserving the craft to be used multiple times. The space shuttle is the leading forefront in technology and a marvel of human engineering. It was used to expand fundamental laws and restrictions currently hindering humanity from deep space exploration. Its rise of knowledge would become one of the most significant achievements mankind has ever accomplished.
However, building the space shuttle challenged engineers across the world. On paper, it seemed inconceivable to create a spacecraft resilient enough to withstand reentry and be in a working condition after. Although, unphased by the challenge, engineers at NASA soon developed the Columbia, the first space shuttle which was to carry 11 astronauts and 27,000 kilograms into space atop a 56-meter tall rocket. While each orbiter was engineered to be used for 100 flights, the Columbia rocket infamously exploded on Feb. 1, 2003, when it broke up during reentry, killing all seven astronauts on board.
The Difficulties in Reentry
The most difficult and dangerous parts of space flight is reentry. Spacecraft engineers are challenged to develop a vehicle capable of withstanding the immense heat and force the orbiter undergoes. The orbiter must slow down from its initial speed of 28 000 kilometers per hour (9 times faster than an average rifle bullet!) to a much slower 300 km/h over a vertical 4oo kilometer distance. During reentry, the acceleration is so significant it undergoes as much as 7 times the force of gravity putting incredible strain on the aircraft. As the aircraft continues to fall through the Earth’s atmosphere a massive amount of drag causes the external parts of the orbiter to heat up to as much as 1,648°C.
Preventing the aircraft from becoming engulfed in flames requires several forms of tiles which are placed depending on the thermal requirements of the area. High-temperature reusable insulation tiles covered the underside with low-temperature tiles on the rest of the craft. The leading edges of the vehicle are reinforced with a carbon-carbon coating to prevent the craft from disintegrating. The main difference between the coating is the outer layer of the skin. Darker regions have a high heat transfer rate while the white surfaces excel at reflecting heat.
[Image Courtesy of NASA]
Despite having a craft that can withstand the extreme heat, the aircraft was also required to glide safely to the Earth with no external power. Of course, crafting such a vehicle was not an easy task. However, the dual delta wings provide just enough lift to enable the craft to glide, though it is often referred to as the flying brick.
It would seem intuitive to use a smooth surface to create a minimal amount of drag, however, NASA engineers resorted to a material with small gaps increasing turbulent flow to create a secondary air barrier to resist the heat. However, the resistance significantly impacts the aerodynamics of the shuttle, causing it to descend at virtually the same velocity of a human at terminal velocity- about 200km/h down at an altitude of about 3km. In comparison, it would be an equivalence of an airline pilot initiating a descent which takes only 2 minutes to hit the ground.
The immense rate of descent is surprisingly beneficial to reentering the atmosphere. The large swept back wings exhibit a large amount of lift which would cause the shuttle to skip off the atmosphere is it increases in density- similar to skipping a rock off of a pond. To counteract the force, a computer guidance sequence initiates a 60-degree pitch to cause the shuttle to plummet into the atmosphere.
The craft continuously slows down, however, the lift from the wings causes the aircraft to maintain a large velocity, much too fast if the shuttle was to land with a direct approach. The force of lift must be counteracted to achieve a safe level of speed, therefore, the shuttle is tilted onto its side causing the direction of lift to be perpendicular to the ground. Of course, the space shuttle is then put off course requiring it to be rotated 180-degrees to direct the force in the opposite direction. The aircraft continuously performs the maneuver until it straightens out 20 km from the runway allowing the commander to perform the final approach.
The commander lines up the module and drops the gears at the last possible moment. Without any thrust, there is only one attempt at landing. Opening the gears too soon creates a significant amount of drag that would cause the shuttle to stall and plummet to the Earth. Too much speed and the gears will collapse, similarly causing catastrophic failure.
Bret Copeland further explains the complications of landing the space shuttle.
The space shuttle is the beacon which led to the greatest achievement of humanity, installing a permanent space station which would continue to be occupied for nearly twenty years. The project has lead to significant advancements in knowledge and technologies, perhaps building the foundations which will propel the next mission to other worlds. It all, however, lies within the technologies and genius that went into engineering a spacecraft which could not only bring astronauts to space but safely back home in the same shuttle which was to be used many, many times.
Though many have lost their lives as they ventured beyond the Earths bounds, the space shuttle program has successfully launched more than 130 rockets and over 350 people into space aboard the most advanced, but worst aircraft in the world: The flying brick. It is through their daring bravery that will continue to push the forefront of space to unlock the secrets of the universe.