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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."
How do you climb the tech ladder? The logical way is that first you learn from what others have done, and reproduce it.
What's logical about that?
Then, when you are caught up, you start to lead.
Why are they catching up? Did Chinese just pop into existence 20 years ago?
And with a billion people, the Chinese have their share , or maybe more than their share, of first class brains.
And far less than their share of results.
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.