This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Researchers from Tokyo Metropolitan University have created a new system to test magnetohydrodynamic aerobraking for spacecraft reentering the atmosphere. Their platform generates intense magnetic fields with a powerful electromagnet as a miniature vessel is hit with a shock wave traveling at over seven kilometers per second (4.3 miles per second).
The magnets reached far higher fields than previous work with permanent magnets and are a crucial stepping stone toward tests with real vessels in the atmosphere. When spacecraft reenter the atmosphere, they are hit by shock waves exceeding several kilometers per second that heat the air at the vessel surface to several thousand degrees. To counter this intense heating, current technologies use heat-resistant tiles and sacrificial material that help dissipate heat and protect the craft.
While reliable, this approach has serious limitations, increasing weight, surface wear, cost and repair times. This is especially limiting as demand increases for reusable vessels. A promising technology for overcoming these challenges is magnetohydrodynamic aerobraking (MHD).
By applying a magnetic field to the weakly ionized plasma at the shock wave, the ultrahot shock layer can be expanded and pushed away from the craft surface. Not only does this reduce the flow of heat into the vessel, but it can increase aerodynamic drag, slowing the craft down. While previous work strongly supports this method, testing such systems is a major challenge.
Experiments usually involve putting a permanent magnet inside a small test model and hitting it with a shock wave, but this design makes it difficult to systematically test different field strengths and shapes. To enable engineers to test a wider range of magnetic fields, a team led by Associate Professor Kohei Shimamura of Tokyo Metropolitan University has engineered a new system using a powerful electromagnet mounted inside a small model. The electromagnet is formed by a customizable set of coils and powered by a pulse-forming network (PFN), which hits it with an intense pulse of current, generating a strong field for a short period of time.
In a test, the model is hit by a shock wave traveling at over seven kilometers per second (4.3 miles per second) for tens of microseconds in a hypersonic expansion tube, a ground-based facility for testing aircraft and spacecraft in extreme environments. The team designed the system to track the arrival of the shock wave and precisely synchronize the magnetic field to its duration, reaching field strengths significantly exceeding those possible with a permanent neodymium magnet. A high-speed camera was also synchronized to the shock wave to record the light given off by the heated shock wave layer (or "self-emission" layer).
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