Holding Stronger
Aircraft have flown at nearly ten times the speed of sound and at high altitudes. Now, we are developing spacecraft that can land on other planets. For any of this to be possible, these craft have to be designed to withstand extreme forces. Engineers and scientists have to go beyond conventional solutions and develop new, innovative designs that survive extreme environments.
Designs of ground-based structures like bridges are dictated primarily by static loading forces due to gravity. Both static and dynamic forces drives the designs of airborne structures like airplanes and helicopters. Designs of space-based structures such as satellites are dictated primarily by dynamic loading forces due to launch and on-orbit operations. Engineers have to design aircraft and spacecraft structures to be light, but above all else, the structures have to be strong. They have to hold together despite high forces in flight.
Flutter Testing
Flutter can result in catastrophic failure of structure if not eliminated during the development of an aircraft design. Although engineers analyze structural designs for flutter phenomena, testing proves the adequacy of the design. Wind-tunnel testing is performed on sub-scale models that are dynamically scaled. Testing a proof-of-concept model is much safer than actually flying a new design. Also, many configurations can be tested along with potential fixes. Once the final design has been successfully tested, a prototype aircraft is built for flight testing.
We all know jets fly fast, but have you thought about what kind of forces a jet experiences when it lands and hits the ground going 150 miles an hour — or more? Jet landings on a carrier deck are even more challenging. That requires not only a strong jet, but a strong landing system. Therefore, engineers need to consider landing dynamics, impact loading, and structural integrity.
Landing on a flight deck is one the most difficult things a navy pilot will ever do. The flight deck only has about 500 feet of runway space for landing planes, which isn’t nearly enough for a conventional landing of the heavy, high-speed jets on U.S. carriers. To land on the flight deck, each plane has a tailhook, which is exactly what is sounds like — extended hook attached to the plane’s tail. The pilot’s goal is to snag the tailhook on an arresting wire, sturdy cables woven from high-tensile steel wire. The arresting wire system can stop a 54,000-pound aircraft traveling 150 miles per hour in only two seconds, in a 315-foot landing area. Now that’s holding strong!
Jet Landings
SRB Splashdown
Solid rocket boosters (SRBs) help propel our astronauts aboard the Space Shuttle outside Earth’s atmosphere, but these high-powered launch vehicles don’t make the whole trip. SRBs lift the shuttle to an altitude of 150,000 ft, and then they separate from the rest of the vehicle. Parachutes decelerate the SRBs and bring them back to land in the Atlantic Ocean about 122 nautical miles downrange from the launch site in Florida. 295 seconds later, the SRBs splash down into the water going at a rate of 55 miles per hour. Because of the parachutes, the SRBs impact the water with the nozzle end first. The burned-out housings remain afloat due to trapped air.