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Nasa Set to Demonstrate X-Ray Communications in Space

nasa.gov

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Re: Nasa Set to Demonstrate X-Ray Communications in Space

#11

Post by jbay808 »

madengr wrote: post #9

Will be interesting to see what they use for a receiving antenna. 90 dBi gain is about the limit for single aperture reflector antennas at RF, as you contended with structure deformation at low frequencies, then surface roughness at high frequencies, not to mention tracking a fast moving object with that precision to keep it in the beam width. At X-rays, I don’t know how you would focus it as the roughness is in on a…

Even to x-rays, smooth surfaces become reflective at grazing incidence, so you can make mirrors that are constructed on that principle. Not simple to do, but not impossible either.

Re: Nasa Set to Demonstrate X-Ray Communications in Space

#12

Post by madengr »

jbay808 wrote: post #11
madengr wrote: post #9

Will be interesting to see what they use for a receiving antenna. 90 dBi gain is about the limit for single aperture reflector antennas at RF, as you contended with structure deformation at low frequencies, then surface roughness at high frequencies, not to mention tracking a fast moving object with that precision to keep it in the beam width. At X-rays, I don’t know how you would focus it as the roughness is in on a…

Even to x-rays, smooth surfaces become reflective at grazing incidence, so you can make mirrors that are constructed on that principle. Not simple to do, but not impossible either.

The gain falls off as the RMS surface roughness becomes a fraction of a wavelength; see figure 1 here:

https://arxiv.org/pdf/1007.4600.pdf

So it would be interesting to see how that effects it. I suppose a crystal fractured along the lattice for an atomically smooth surface.

Re: Nasa Set to Demonstrate X-Ray Communications in Space

#13

Post by nine_k »

amelius wrote: post #4
zeristor wrote: post #2

A wild idea I had never even thought of, X-rays are of high enough frequncy that they can penetrate the plasmasheath of high velocity vehicles. Seemingly this is for hypersonic transport, and rentry vehicles, my mind is quite boggled.

What is the mechanism by which a plasmasheath blocks radiowaves, and why would x-rays be an exception?

This is similar to how a metal box blocks radio waves, and how x rays can still penetrate it.

Re: Nasa Set to Demonstrate X-Ray Communications in Space

#15

Post by eternauta3k »

kijin wrote: post #6
amelius wrote: post #4

Earlier quoted context omitted.

What is the mechanism by which a plasmasheath blocks radiowaves, and why would x-rays be an exception?

https://www.researchgate.net/post/How_does_the_plasma_sheath... > an electromagnetic wave can penetrate the plasma if the wave frequency f is higher than the electron plasma frequency. X-rays have a much higher frequency (i.e. much higher energy) than the radio waves we normally use for communications, so it can punch through the noise of charged particles that makes up plasma.

I believe it's not a matter of "noise". Rather, metals and plasma are conductive up to a certain frequency. Beyond that frequency, resistance goes up and the material becomes transparent. This is basically because the electrons can't "keep up" with the electric field's oscillation so they are ineffective at screening it.

Re: Nasa Set to Demonstrate X-Ray Communications in Space

#18

Post by SkyMarshal »

KingFelix wrote: post #10
ambicapter wrote: post #8

> XCOM I love it (For those not aware, https://en.wikipedia.org/wiki/XCOM:_Enemy_Unknown )

Also https://www.xcom-labs.com/ And of course Https://www.x.com

Link for the lazy:

https://www.x.com/

(just put a trailing / at the end)

Re: Nasa Set to Demonstrate X-Ray Communications in Space

#19

Post by Causality1 »

kijin wrote: post #5

Are there any health concerns about using X-ray constantly for communications? For example, should astronauts performing EVAs take care to avoid the area around the antenna? Or is there enough ionizing radiation in space already that adding some X-ray in the mix won't make any difference?

That would depend on the transmit power, but in short, you wouldn't want to be outside the vehicle for a long time when the transmitter is on. A typical x-ray machine emits about twenty watts of x-ray power when in use with a typical shutter speed of 1/10 to 1/2 of a second. There's no data about how much power NASA is using in this experiment or how much a production model transmitter would use, but ground-to-ISS transmission over FM can be done with a 25-watt transmitter.

Now, the x-ray transmitter wouldn't be focused the right way to send maximum radiation into an astronaut and it would have a reduced duty cycle because it's not just a simple x-ray flashlight, but giving it an hour-long bear hug while it's in use would be a very bad idea.

Of course the most relevant point is that the vast majority of spaceships don't have humans on them.

Re: Nasa Set to Demonstrate X-Ray Communications in Space

#20

Post by xioxox »

madengr wrote: post #9

Will be interesting to see what they use for a receiving antenna. 90 dBi gain is about the limit for single aperture reflector antennas at RF, as you contended with structure deformation at low frequencies, then surface roughness at high frequencies, not to mention tracking a fast moving object with that precision to keep it in the beam width. At X-rays, I don’t know how you would focus it as the roughness is in on a…

In X-ray astronomy we often use Wolter Type 1 optics based on grazing incidence. These can be made with various techniques depending on the spatial accuracy (point spread function) required, e.g. foils for low accuracy or even stacked silicon wafers planned for the Athena telescope. The effective area of the telescope is smaller than the physical mirror size as everything has to be reflected at grazing incidence. We often use CCDs to detect the X-rays.
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