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Plasma Resonance Could Overcome Radio Silence For Returning Spacecraft

Posted by timothy on from the don't-keep-that-all-bottled-up dept.

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."

5 of 62 comments (clear)

  1. Re:Oh Boy Chinese Science by PeterM+from+Berkeley · · Score: 3, Insightful

    The Chinese are getting better every year, year in and year out. How do you climb the tech ladder? The logical way is that first you learn from what others have done, and reproduce it. Then, when you are caught up, you start to lead.

    And with a billion people, the Chinese have their share , or maybe more than their share, of first class brains. Their culture doesn't sneer at science, either.

    The Chinese are on the fast track to being the dominant world power if their own misgovernment doesn't screw them up.

    --PM

  2. Re:Star Trek solution, eh? by St.Creed · · Score: 4, Insightful

    what can be done in that precise stage so the comunication channel becomes the difference between live and death?

    We can send telemetry, making a difference between life and death for the *next* crew to go up.

    --
    Therefore, by the (faulty) logic you're using, you're just a cow with a keyboard - osu-neko (2604)
  3. What issue? by Dereck1701 · · Score: 3, Informative

    I thought this was no longer an issue? I think continuous communication had been in use for over a decade with the space shuttle before the end of the program. The solution was to use satellites, being on the other side of the plasma sheath, as relays to communicate between a reentering craft and the ground..

    1. Re:What issue? by AmiMoJo · · Score: 3, Interesting

      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
  4. Couple of things by Laxator2 · · Score: 3, Interesting

    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.