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Plasma Resonance Could Overcome Radio Silence For Returning Spacecraft
Zothecula points out this article about a workaround for a long-standing problem with space-flight communications: some of the most cruicial time of a re-entry is also time when the craft cannot send data to or receive instructions from the ground controllers. From the article: Returning spacecraft hit the atmosphere at over five times the speed of sound, generating a sheath of superheated ionized plasma that blocks radio communications during the critical minutes of reentry. It's a problem that's vexed space agencies for decades, but researchers at China's Harbin Institute of Technology are developing a new method of piercing the plasma and maintaining communications.
This means coupling the craft's antenna to that plasma sheath, "[causing] the sheath to act as an inductor. Together, they create a resonant circuit."
I am a Chinese
Although I do not enjoy the attitude displayed by those racists towards the Chinese, I do hope that there are even more of them --- the more of them look down on us, the more of them won't even notice what we have accomplished
We Chinese have a saying --- stay low but work diligently
In other words, the more we stay under the radar the more we can progress without Obama and his anti-Chinese gang looking over our shoulders
This way you don't need to rely on a satellite for communication. Cheaper, less to go wrong. A low cost improvement.
const int one = 65536; (Silvermoon, Texture.cs)
SJW, n: "Someone I don't like, and by the way I'm a fuckwit" - AC
The article specifies that spacecraft re-enters at about 5 times the speed of sound.
1) The spacecraft on low Earth orbit have orbital velocities of about 8km/sec, and the speed of sound is about 0.34 km/sec. That makes the spacecraft about 23 times faster than sound on re-entry. I remember reading bout the Columbia disaster, that the shuttle entered the atmosphere at about 26 times the speed of sound. That makes sense, as the potential energy of the above-atmosphere orbit is transformed into kinetic energy at the altitude of hitting the atmosphere.
For the Apollo spacecraft, they re-entered at even higher speed, close to the Earth escape velocity of 11.2km/sec. That makes them about 33 time faster than sound.
2) The plasma sheet forms a very narrow cone with the spacecraft at the tip of it, effectively enveloping the spacecraft. The angle is given by:
sin \theta = speed of sound / speed of spacecraft.
At mach 23 it is about 6 degrees. Plus the plasma is turbulent, so it is very difficult to aim a signal along this cone and hit a satellite.