Superconductivity and carbon nanotubes, are Type I, while almost all impure and compound superconductors are Type II. Conversely, a spinning superconductor generates a magnetic field, precisely aligned with the spin axis. The effect, the London moment, was put to good use in Gravity Probe B. This experiment measured the magnetic fields of four superconducting gyroscopes to determine their spin axes. This was critical to the experiment since it is one of the few ways to accurately determine the spin axis of an otherwise featureless sphere. Superconductivity was discovered on April 8, 1911 by Heike Kamerlingh Onnes, who was studying the resistance
Heike John Aachen and earned a doctorate in 1987. In the same year she was selected as one of five West German astronaut candidates for the Spacelab D-2 mission, along with Hans Schlegel, Ulrich Walter, Gerhard Thiele and Renate Brümmer. She served as Cap com during the D-2 mission in 1993, but was never assigned to a spaceflight herself. After retiring as an astronaut, she became a professional pilot for Lufthansa. She is married to astronaut Hans Schlegel. Heike John Heike John (now Heike Walpot; born 19 June 1960) is a retired German swimmer and former astronaut candidate. She won a bronze