
Nasa Set to Demonstrate X-Ray Communications in Space - zeristor
https://www.nasa.gov/feature/goddard/2019/nasa-set-to-demonstrate-x-ray-communications-in-space
======
madengr
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
molecular scale. So going to higher frequencies has its limits.

I don’t know what the equivalent gain of these large, optical telescopes are,
but they seem to suffer from the same problems.

The plasma penetration must the the real objective. You can get thru the
plasma with standard RF, it just takes lots more power, or lower data rate,
but a low reset beacon is feasible, just not voice comms.

~~~
jbay808
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.

~~~
madengr
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](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.

------
zeristor
As ever Scott Manley made me do it:

[https://www.youtube.com/watch?v=e4nXU1xF_Tg](https://www.youtube.com/watch?v=e4nXU1xF_Tg)

------
kijin
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?

~~~
Causality1
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.

------
zeristor
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.

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

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

~~~
copperx
What kind of metal? I thought X-rays couldn't penetrate lead.

------
coin
NASA not Nasa. It’s an acronym not a word.

~~~
zeristor
This a NASA article on a NASA web site

~~~
ComputerGuru
Yes, and (now, at least) the linked article has NASA capitalized in the title.
(Unless you intended to reply to @tntn)

------
fithisux
CancerComm

------
ambicapter
> XCOM

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

~~~
KingFelix
Also

[https://www.xcom-labs.com/](https://www.xcom-labs.com/)

And of course

Https://www.x.com

~~~
SkyMarshal
Link for the lazy:

[https://www.x.com/](https://www.x.com/)

(just put a trailing / at the end)

