Russian Physicists Solve Radio Black-Out Problem for Re-Entering Spacecraft

http://www.technologyreview.com/blog/arxiv/26222/

by Anon84 • 16 years ago

138 36 16 years ago

It reminds me of the Navy's sea water antenna system (http://www.public.navy.mil/spawar/Pacific/TechTransfer/Produ...).

I know nothing about this thing, but I would have thought the plasma would be on the underside of the craft, allowing any antennae on the top to communicate with a satellite that could relay everything to/from the ground station.

radu_floricica• 16 years ago

I'm guessing it's not going straight down, and most of the speed is actually on the x axis. The atmosphere is how much? 50 km? While the descent path is most likely counted in thousands.

jared314• 16 years ago

Wouldn't the plasma flow around the craft from bottom to top like a bubble?

lutorm• 16 years ago

Yeah, it does.

igravious3• 16 years ago

That should read Theoretically Solve but I admire the ingenuity nonetheless and hope that the road from theory to practice is short and uneventful.

A shame this hack has military applications, it would be nice if every now and again scientists patented their discoveries and precluded military use in doing so. [ Please don't downvote me for expressing this sentiment :) ]

viraptor• 16 years ago

I thought there was a clause making all technology available for national defence, regardless of patents... but can't find the source. Anyone?

vyrotek• 16 years ago

I've heard this too. A quick search found a book briefly covering the topic. I couldn't find an official source.

As a matter of public policy - national defense trumps patents - http://bit.ly/faNGT3

igravious3• 16 years ago

That may be true in the US but what about in other jurisdictions? I mean doctor's have the Hippocrates oath of do no harm to the patient but (and not to come over all tree-hugging peacenik like) why do chemists/bioengineers/physicists not have a similar oath with respect to the our species or other species in general or the planet in its entirety? But I guess the scientists do the theorizing and the engineers and coders build weaponize or apply the theoretical results in military applications so what good would it do ... Hmm, maybe the New Year is making me come over all compassionate and fuzzy :)

jerf• 16 years ago

Pretty hard to lock down a communications technology to "no military use". What are they going to do, ask pretty please don't do that with a cherry on top?

igravious3• 16 years ago

I know, right?! Like I said elsewhere, I'm probably letting the warm fuzzies of the holiday season get the better of me.

Is there even any precedent for this? Also, I seem to remember a quote from the mathematician Hardy boasting that he loved working in pure number theory because it had no application (military or otherwise) to the real world. Fast forward 50 years and pure number theory is widely used in encryption technologies ... so you just never know.

Anyway, and this might be cynical but a system that is used to imposing its will down the barrel of a gun will surely just take what they want regardless of the prohibitions.

I am reminded of the blessing that accompanies the public domain Sqlite. http://www.sqlite.org/different.html

  May you do good and not evil
  May you find forgiveness for yourself and forgive others
  May you share freely, never taking more than you give.

Evil is such a comic book superhero word nowadays but I wonder how many times Sqlite has been put to nefarious ends.

sliverstorm• 16 years ago

What do you do then when Country X ignores the patent and incorperates it into THEIR military? Your idea sounds like voluntarily hobbling yourself for idealistic reasons.

fish2000• 16 years ago

The article says that one of the potential military applications would be the ability to disarm or redirect a weapon as it reenters the atmosphere -- Having taken the same topical look at the article that you have, I am not sure why you think that is a categorically bad thing to implement, from any standpoint. I mean, you could make the case that having that capacity will make the fingers that rest on the big red buttons all the itchier... if you wanted to be all ad hominem about things. I for one think that gapingly general fiat mandates like the one you propose are just as potentially damaging as any weapon.

CamperBob• 16 years ago

This is a silly and naive sentiment, akin to "This new factoring algorithm has DRM-breaking applications. We'd better outlaw it."

Downvoted accordingly.

iwwr• 16 years ago

I stumbled onto this a while ago: http://en.wikipedia.org/wiki/Plasma_antenna

eps• 16 years ago

This might be a completely dumb idea and it must've been explored before, but how about attaching the antenna to a string and trailing it behind the ship at a considerable distance to clear the extent of the plasma shield. Is it that no string is strong or plasma-resistant enough?

elwin• 16 years ago

When re-entering, spacecraft are being decelerated, so anything towed behind the spacecraft will catch up with it. A rigid pole might work.

disponsible• 16 years ago

I think the plasma forms a complete enclosure, i.e. there is no "break" in its surface at the tail of the spacecraft. The pole will need to cross the surface of the plasma shield meaning an exposure to very high temperatures. OTOH the pole can be insulated the same way the front of the craft is. It looks doable in principle, so I wonder what other problems are there.

Could it be that extending the pole during the descent makes the design of the hull more complex and through that more fragile?

dstorrs3• 16 years ago

They mention this in the article, where they talk about extending an aerial out past the plasma sheath. They then say "this allows communication until the aerial ablates."

ortusdux• 16 years ago

It would seem to me that any antenna that extends outside the 'plasma bubble' would still be traveling at the same speeds and subject to the same problems as the shuttle.

pavel_lishin2• 16 years ago

Anyone else see a weird font used for double-F's?

http://i.imgur.com/EpolQ.png

chronomex• 16 years ago

The document uses a ligature ( http://www.fileformat.info/info/unicode/char/fb00/index.htm ) for ff. Apparently the font your browser uses by default doesn't have it. Some font replacement algorithm decided that the script font you're seeing is the closest! :-)

dstorrs3• 16 years ago

One thing they did not mention is that this solves the primary problem with orbital crowbars (fictionally called "Rods from God", "Thor", KEWs, and various other things). You could drop a kinetic warhead (basically a crowbar) from orbit to kill a tank / bunker / whatever, but you could also use them for a variety of peactime missions such as mining, emergency flood control (digging drainage ditches, causing controlled landslides), etc.

Each crowbar would need some sort of minimal steering system to account for atmospheric turbulence. This steering can't be locally controlled because the device can't see past the plasma sheath. It can't be remote controlled because the plasma sheath stops transmissions. With this new "plasma aerial" technology, you could steer each crowbar individually from the launcher platform.

borism2• 16 years ago

interesting! what kind of materials need to be used so that crowbar doesn't burn-up on reentry? isn't it a little bit more expensive than using traditional explosives?

dstorrs3• 16 years ago

If you made it out of steel, it would survive just fine -- there would be some ablation, but it would still get to the ground.

As to the "more expensive"...no, not really. Basically, it's just a crowbar with a simple camera and some fins on it. Using this technology it would trade in the camera for a radio back to the launch vehicle. You'd need all the same bits on a missile, plus more besides, and the missile would need to be larger.

gvb• 16 years ago

Trivia: the space shuttle avoids the blackout by its shape, which allows it to communicate upward to the TDRSS satellites.

http://en.wikipedia.org/wiki/Communications_blackout#Reentry...

"[T]he Shuttle can communicate with a Tracking and Data Relay Satellite during re-entry. This is because the shape of the Shuttle creates a "hole" in the ionized air envelope, at the tail end of the craft, through which it can communicate upwards to a satellite in orbit and thence to a ground station."

electromagnetic• 16 years ago

I sincerely thank you, it's something I've always wondered about but never put in the time to actually look it up.

TGJ• 16 years ago

One thing that has always seemed to rub me wrong in space exploration is the giant need to stay in touch with Earth. Supposedly the space shuttles are crewed by the great explorers of our time, but it always seems that everything is governed by people on the ground and not in the air.

Nick_C• 16 years ago

Basically it's resource management, both human and materials. I'll leave the human side out, but recommend Gene Kranz book Failure Is Not an Option for more info on why ground controllers are important.

It costs a huge amount of money (in fuel) to lift anything up, even just a kilo or two. You're better off lifting only a telemetry system and putting all the processing, display and engineering on the ground. That means having ground controllers to manage it.

Of course, in the early days, you couldn't physically fit computers in the capsule. Now we can, but it is still more economical to have most of it on the ground and just use radio to let the systems communicate.

Russian Physicists Solve Radio Black-Out Problem for Re-Entering Spacecraft

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