The frictions exerted during atmospheric reentry are enough to break spacecraft into comets of glowing slag if not properly mitigated—but otherwise. The Space Shuttle, when it was still operational, was designed to hit the outermost edges of Earth’s atmosphere traveling (~17,000 MPH), and then ride a wave of superheated plasma — created because the frictional forces are so great that literally they tear the surrounding air apart at the molecular level — down in the atmosphere until the airfoils regain their effectiveness.
“Using atmospheric drag is the most effective method of decelerating a spacecraft.” To survive those intense temperatures of 3000 degrees F, the Shuttle would melt and drift away, taking extra heat with them, but for tomorrow’s reusable spacecraft, NASA has something better in mind, .
NASA has scheduled a launch window of November 9 for the LOFTID mission. It will fly alongside a new NOAA “polar weather satellite.” After the satellite separates from the Atlas rocket’s upper stage, LOFTID will deploy and inflate into low Earth orbit before re-entry.
“One of the biggest differences is before we do suborbital testing, at about 5,600 miles per hour, or 2.5 kilometers per second, which is already difficult,” said Steve Hughes, LOFTID aircraft lead at NASA’s Langley Research Center. “But with LOFTID, we’ll be coming in at almost 18,000 miles per hour, or 8 kilometers per second. That’s about three times faster, but that means nine times more energy.”
The LOFTID Heat Shield offers four levels of protection against all that energy. The outer layer is made of ceramic and silicon carbide yarn woven into fabric on the same types of industrial looms that make jeans. The second and third layers are two types of insulation, they are there to protect the fourth layer – the actual inflatable parts. Everything is stacked on a series of concentric rings — themselves made from a woven polymer ten times stronger than steel by weight — that will help guide the expansion of the shield.
NASA has been developing Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology for more than a decade. LOFTID (Low-Earth Orbit Flight Test of an Inflatable Decelerator) is the latest iteration of this technology, a new kind of heat shield that potentially avoids many of the problems NASA has with the current generation of rigid airfoils. These hard shields have a hard limit on their size, dictated by the diameter of the missile fairing. Soft air shells do not face this limitation and can extend well beyond the edge of the shroud, allowing NASA to protect larger and heavier payloads as they enter the atmosphere.
This is especially important for our future solar system exploration plans because the other issue with current heat shields is that they only work in Earth’s atmosphere. You’re trying to put something the size of the Space Shuttle on the surface of Mars, and that exercise will end up with your spacecraft a very large streak on the Red Planet — or a very small crater if you’re particularly unlucky. The Martian atmosphere is simply not thick enough to create sufficient friction against modern-sized heat shields to safely slow the Shuttle’s descent. So NASA is testing an inflatable that is.
When it begins its descent, LOFTID will travel at more than 25 times the speed of sound. NASA hopes that by the end, LOFTID will be crawling along at a relative 609 MPH. Throughout its flight, the test shield’s onboard data recorder will transmit the most relevant sensor and video data, while storing as much as possible on board in a launchable recorder. If all goes according to plan, the LOFTID shield will slow down enough to deploy a landing chute before sitting in the Pacific Ocean before recovery by ULA.
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