Meteoroids are debris from earlier eras in our solar system. They can be leftovers from planets that never formed or remains of ancient collisions. When these bits rock and metal enter our atmosphere, they become meteors. Since they travel at speeds of several kilometers per second, they create incredibly strong shock waves off their bow once they’re in the atmosphere. These shock waves are so strong that they rip the air molecules apart and create a hot plasma that can scorch the outside of the meteor. That plasma also glows, which is why meteors look like a streak of light from the ground. Any remains that make it to the ground are known as meteorites, and they have some pretty awesome features. Check out the full Brain Scoop episode below to learn some of the typical (and not so typical!) characteristics of meteorites. (Image and video credit: The Brain Scoop/Field Museum)
Tag: re-entry
Re-Entry
Atmospheric re-entry subjects vehicles to extreme conditions. At high Mach numbers, the leading shock wave compresses the air so strongly that it reaches temperatures hotter than the surface of the sun. At these temperatures, oxygen and nitrogen molecules in the air dissociate, bathing a vehicle in a plasma of ionized gas molecules. Often these atoms chemically react with the surface materials of a vehicle causing ablation that removes mass from the vehicle while helping protect the vehicle substructure from re-entry heating. Tests in specialized ground facilities like arc-jet plasma tunnels are necessary to develop thermal protection systems capable of shielding a vehicle during hypersonic flight. (Image credit: D. Ponseggi/NASA)
Feathering on SpaceShipTwo
Virgin Galactic and Scaled Composites recently performed their first feathered flight with SpaceShipTwo, which is on track to be the first commercial spaceship. Feathering is a re-entry technique devised by Scaled Composites founder Burt Rutan:
Once out of the atmosphere the entire tail structure of the spaceship can be rotated upwards to about 65º. The feathered configuration allows an automatic control of attitude with the fuselage parallel to the horizon. This creates very high drag as the spacecraft descends through the upper regions of the atmosphere. The feather configuration is also highly stable, effectively giving the pilot a hands-free re-entry capability, something that has not been possible on spacecraft before, without resorting to computer controlled fly-by-wire systems. The combination of high drag and low weight (due to the very light materials used to construct the vehicle) mean that the skin temperature during re-entry stays very low compared to previous manned spacecraft and thermal protection systems such as heat shields or tiles are not needed. During a full sub-orbital spaceflight, at around 70,000ft following re-entry, the feather lowers to its original configuration and the spaceship becomes a glider for the flight back to the spaceport runway. #
Though it works well for decelerating from sub-orbital speeds, feathering is sadly not useful for orbiting spacecraft due to the much higher kinetic energies that have to be dissipated.
