25 novembre 2019 |
International,
Aérospatial
The U.S. government is pushing into hypersonic weapons in a big way, with at least five different weapons programs currently in development. Nanotechnology is shaping up to be a key tech that will enable delivery systems to survive traveling through the atmosphere at Mach 5 and above, with carbon nanotubes showing promise as strong, lightweight material that rapidly sheds heat.
Hypersonic weapons are weapons that travel at incredible speeds through the atmosphere. Hypersonics start at Mach 5 (3,836 miles an hour), or five times the speed of sound. Pushing an object through the air at really, really fast speeds creates a unique problem: as speed increases, the friction from the object passing through air also increases.
This friction generates heat. The skin of the SR-71 Blackbird strategic reconnaissance jet and the fasted manned airplane ever built regularly warmed to up to 500 degrees Fahrenheit at Mach 3. The X-15 rocket plane, flown during the 1960s, reached temperatures of 1200 Fahrenheit as it flew to Mach 6. At Mach 10, the friction is enough to “melt the toughest steel,” while at Mach 20, the temperature reaches an astounding 17,000 Fahrenheit. Eventually, hypersonic weapons could reach Mach 24.
Scientists and engineers understand how to handle traditional air friction problems thanks to the technical challenges of spacecraft and nuclear warheads re-entering the atmosphere. But a missile warhead de-orbiting over an enemy target is only exposed to heat for a handful of minutes, as it transitions from space to the atmosphere and finally smashes into its target. A hypersonic weapon, on the other hand, spends its entire flight within the atmosphere and is exposed to high heat the entire time.
An article at DefenseOne describes how scientists are working with carbon nanotubes to solve the heat issue. Scientists at Florida State University's High-Performance Materials Institute are looking into using carbon nanotubes as a construction material for hypersonic weapons. Carbon nanotubes are a synthetic material consisting of carbon tubes with a diameter as small as one nanometer. Carbon nanotubes are stronger than steel and insulate against heat. Now, researchers have discovered that soaking carbon nanotubes in phenol can increase their ability to disperse heat by one-sixth, allowing less nanomaterials to be used for the same job.
What does this mean for hypersonic weapons? It means that materials that can stand the heat and stresses of hypersonic, atmospheric travel are on the way, and that hypersonic weapon designers could even safely achieve higher speeds by using thicker layers of the stuff.
https://www.popularmechanics.com/military/research/a29847271/us-military-nanotech/
