Aerogel is regarded as the lightest solid in the world. Due to its high specific surface area and low thermal conductivity, it is widely used in thermal protection materials for aerospace vehicles. In 1999, NASA developed a silica aerogel with a density of 3 mg/cm³, which was the lightest solid material at that time. However, the brittleness and humidity sensitivity of silica aerogel materials have limited their application. For many years, NASA has been supporting research on durable aerogels. 
Silica aerogel material 
Based on the demand for a lightweight and flexible supersonic inflatable aerodynamic decelerator material for spacecraft landing, researchers at NASA's Glenn Research Center (GRC) first conducted a study on using polymer-reinforced silica aerogel to enhance its durability. They found that polymer-reinforced silica aerogel has double the density and a 30% to 50% reduction in specific surface area compared to silica aerogel, but its strength has increased by two orders of magnitude. 
Polymer-reinforced silica aerogel enhances durability. 
Despite this, its strength still failed to meet the requirements of deceleration materials for spacecraft. Subsequently, in collaboration with the University of Akron, polyimide aerogels cross-linked with octaaminopropyl (POSS) were developed, resulting in a polyimide aerogel with a density of 0.12 g/cm³ and a porosity of 90%. This material can withstand a temperature of 1100 °F for 90 seconds, ensuring it does not burn upon entering the atmosphere; its strength is five times that of polymer-reinforced silica aerogels, and it can be made thinner (0.5 mm) to meet the requirement of being foldable and storable in spacecraft, effectively overcoming the shortcomings of silica aerogels in terms of weight, cost, flexibility, and durability. 
Flexible polyimide aerogel 
Based on aerogel and fiber materials, NASA has begun to develop multifunctional composite materials that can meet the requirements of structural and thermal protection materials for spacecraft. For instance, researchers at NASA's Kennedy Space Center (KSC) have developed a manufacturing method for multifunctional aerogel/fiber hybrid laminated composites. By choosing different fiber layers (such as polyester, carbon fiber, Kevlar® fiber, Spectra® fiber, Innegra fiber or their combinations), different thicknesses of aerogel layers, and different composite structures, composites with different functions or multiple functions can be produced. This lightweight and high-strength multifunctional composite material can meet the requirements of aerospace vehicles in terms of thermal protection, impact resistance, energy absorption, and sound absorption, and can be applied in many fields such as automobiles, ships, buildings, liquefied natural gas transportation, sports equipment, and military protection. 
Aerospace application case: Inflatable decelerator 
To realize the manned Mars landing program, NASA is developing heavy-lift transportation technology. The Hypersonic Inflatable Aerodynamic Decelerator (HIAD) is a solution that can provide payload and volume benefits for spacecraft braking. In 2006, NASA launched a project called "Advanced Inflatable Decelerators for Atmospheric Entry" (PAIDAE) and developed a HIAD with a diameter of 3 to 12 meters, consisting of an outer layer, an insulating layer, and an airtight layer. 
Civilian cases: Outdoor clothing and equipment 
In 2015, FLEXcon obtained a license for this flexible aerogel technology from NASA GRC and collaborated with Blueshift, which was also conducting research and development on polyimide aerogels, to produce this NASA high-specification aerogel material on a larger scale. Besides pipe insulation products for use in extreme environments, FLEXcon is also developing high-end outdoor products made of polyimide aerogels, such as outdoor clothing, gloves, shoes and boots, and tents. 
(Source: Textile Review)