, coolest regions a few hundred (blue).)
HOT STUFF COMING THROUGH:
Computer modeling by Krishnendu Sinha of the Indian Institute of Technology Bombay shows the heat flow a space capsule might generate during reentry. Hottest regions exceed 6,000 degrees Celsius (white, purple and red), coolest regions a few hundred (blue).
Image: Krishnendu Sinha Itt Bombay
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The frustrating communications blackout that can occur when a spacecraft reenters the atmosphere caused some tense moments in the earlier years of the space age—perhaps most memorably during the crippled Apollo 13 mission. But the phenomenon could also affect communications with new aircraft and weapons systems being contemplated now by the U.S. Air Force, which hopes to find ways to pierce the blackout.
The problem arises when a speeding vehicle heats the air in front of it, ionizing it into plasma that blocks radio transmissions. It resembles the shock waves created when an airplane hits Mach 1 and breaks the sound barrier. In the case of reentering spacecraft and hypersonic aircraft, the plasma-shock boundaries form at speeds of about Mach 10. The space shuttle avoids the blackout because the craft’s broad underside leaves an open area in the plasma plume trailing behind, enabling communications and telemetry data to be relayed to Earth through a network of satellites. But smaller craft are completely engulfed by the plasma.
That has concerned the air force, which plans to develop flight systems, perhaps including hypersonic missiles, surveillance craft and even manned craft that could top Mach 10. “Our standard paradigm [in the test and evaluation world] is we have a vehicle in the air and people on the ground and there’s a telemetry stream of data coming down so people can monitor the vehicle,” explains researcher Charles H. Jones of the Edwards Flight Test Center. Besides severing contact between the test craft and the ground, a plasma blackout also blocks the self-destruct signal that is sometimes necessary when a test vehicle strays off course.
Another crucial concern involves satellite navigation signals. “The military’s becoming ever more dependent on GPS systems,” notes Mark Lewis, a University of Maryland aerospace engineer and former air force chief scientist. Jones agrees, writing in the final report of a 2006 conference in Boston sponsored by the Air Force Office of Scientific Research (AFOSR) on the blackout problem: “Reception of GPS is the most critical capability for which we need to find a solution.... GPS is also the most difficult problem due to its innately weak signal.”
Jones has been something of a voice in the wilderness on the problem. “Mach 10 designs aren’t that common” just yet, he notes, and so “for a lot of people it’s not a pressing issue.” But as new higher-speed concepts in what he calls the “plasmasonic” Mach 10 realm begin to appear, the phenomenon is attracting more attention.
The 2006 conference revealed no lack of possible solutions. Ideas include designing the configuration of the craft so as to minimize the resulting plasmasonic sheath; building an “air spike” at the front of the leading edge that would protrude outside the plasma; finding frequency bands that might not be affected by the ionization; simply bullying through it with an enormously powerful transmitter; and using electrophilic injection, which means dispersing a deionizing substance, most likely water, into the plasma sheath to disrupt it. More exotic ideas involve employing high-powered lasers or ejecting a series of tiny relay devices, akin to messages in a bottle.
Although all the proposed solutions are theoretically feasible, Lewis notes that “the question then is, Are they practical from an engineering standpoint?” The water-injection idea, for example, was actually attempted back in the 1960s, during the Gemini program. But an operational version would require carrying far too much water to be practical.
A variation of electrophilic injection might be a strong contender, however, using a heat shield made of an ablative material that vaporizes parts of itself and deionizes the plasma. “In terms of an engineering solution, that seems like the simplest,” Jones says. Meanwhile Lewis considers himself “a stone agnostic. We’ve got a number of avenues to explore, and I think we’re still at the point where all those avenues should be on the table.” Jones has noted that a combination of techniques most likely will be required to meet all anticipated applications.
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33 Comments
Add CommentI don't see what the big deal is, can't you just use a laser?
Reply | Report Abuse | Link to thisI'm pretty sure it's above the plasma frequency, and something narrowband like a semiconductor laser should be visible through the plasma sheath.
As for testing, I seem to remember a 100 MW arcjet at NASA Ames for testing in such regimes.
Maybe you should read the article before posting? Both points are covered... 1) it's been proposed already, there are still issues there 2) it's still expensive, and nobody wants to fund research for a "potential future issue"
Reply | Report Abuse | Link to thisOkay, we're talking communication at a distance. Telephones won't work 'cause the plasma would melt the cord. Cell Phones won't work because the E/M of the plasma attenuates almost all the E/M spectrum. Smoke signals would conceivably work but only one way: capsule to outside. So. the barrier is the plasma and it needs to be manipulated somehow to allow two way flow of data. How about an environment that would make the plasma respond to E/M signals (not that stupid water in the ablate idea, just dumb, that one, and not promising at all. Sounds like a hint for study/grant money to me) No I think the following will work marvelously and can fit small to large vehicles
Reply | Report Abuse | Link to thisSome of my background is in Magnetrons. They operate by passing intelligence through a magnetic field by interpreting the resultant spin of the electron population. The same can be done outside a space craft employing electro-magnets. Modulate the magnetic fields and as the plasma passes through the modulated field, it will acquire the intelligence of the modulation. The trick is to figure out what form that adoption and subsequent release of intelligence will express it self as. I'm at first thinking along the lines of television static, somewhere in the UHF band. Modulate the Mag field the plasma flows through at 100MHz and it should radiate itself away as the plasma cools. Yes that represents a delay, but it is still getting data through. Also, the inward freq shift may be different than the outward freq shift.
What about a long, thin trailing wire antenna similar to those used by aircraft (even submarines, but for different reasons)?? A high temperature metal wire deployed behind the craft far enough might provide an antenna.
Reply | Report Abuse | Link to thisHow about dropping behind a vehicle a steam of small data recordings with transmit capabilities ?
Reply | Report Abuse | Link to thislowndes: Problem: the multi-Kilowatt power level of the electric static of the plasma.
Reply | Report Abuse | Link to thisKatoom: That's the same as the smoke signal, it only works one way.
Why not try high power modulated light? It works two-way and is mathematically possible.
Reply | Report Abuse | Link to this--
Reply | Report Abuse | Link to thisok, but, which capsule?
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the NASA's Orion?
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Orion needs a rocket to fly!
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but the Ares-1 is already DEAD
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http://ow.ly/K1UO
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As part of my pursuit for a solution to the plasmasonic communications problem I have collected a list of potential techniques. Let me address some of the suggestions in these comments.
Reply | Report Abuse | Link to thisThe use of lasers or modulated light are, in general, forms of optical comm. Ive never talked to an optical comm. expert to discuss how feasible it is. However, putting the laser on the plane raises energy and safety concerns. A common form of optical comm. reflects a laser off a device on the vehicle that transmits bits by changing color rapidly. This puts the energy burden on the ground. Another concern is that most optical comm. is in the infrared. Leading edge temperatures of the vehicle can by 4000 C and the plasma can be 8000 C. Ive been surprised by people telling me that, even at these velocities, tracking is not a problem.
The use of ground testing facilities such as wind tunnels (arcjet or other) or plasma chambers can provide some testing ability but does not provide flight test ability. The other problem with current ground test facilities is that they do not generate the plasma densities expected in plasmasonic flight.
In terms of deionization ablation, water is not practical because of the quantities needed. But work on other materials has already shown theoretic potential.
One of the techniques I have on my list is plasma modulation but Ive never had anyone provide more detail on the technique. The use of magnatrons sounds similar to this. The big question, which is identified in the comment, is how do you encode the signal and retrieve it? There are also weight and power issues with this. More details on this approach would be welcome.
The use of a trailing wire antenna is not currently on my list, but I will add it. This approach is currently used to obtain ambient atmospheric conditions (e.g., pressure outside the flow field of the vehicle.) The big problem is that a wire flaps uncontrollably. The solution has been to use a trailing cone that stabilizes it. Its not clear to me that this is feasible at plasmasonic velocities when considering the required length and material strength. There may also be distortion of the signal as the wire goes through the electromagnetic environment of the plasma.
The concern I have with relay ejection is: What happens to the relays after ejection?
In general, most of the techniques suggested here do not solve the GPS problem (the trailing antenna might.) And some of these are less practical during operations (vs. test) due to infrastructure needs.
Finally, Im conflicted as to whether I should put smoke signals on my list.
Thanks for the discussion.
Boy, isn't radio an interesting subject? My first was a crystal,inductor antenna, ground wire and ear plug!
Reply | Report Abuse | Link to thisThank you for coming into the conversation Mr. Jones. It is so pleasing to know that someone getting paid to do a job isn't threatened by offered help. I commend you sir and hope for all of us that this is no longer an issue to be puzzled over in the near future.
In a magnetron (high power pulsed coaxial), the magnetic feild remains constant while the electric field is modulated. This crossing of fields takes place in the low frequency range (audio to well, pretty much audio (1000 pulses per second).As the electrons flow at this frequency through the M field they gain a spin which adds energy to them. When they pass near a ground potential cavity that has each side of the cavity 'relativistically' more positive than the adjacent cavity, they give up that energy and along with it the audio imposed on them by the pulse train. Giving you, as an example, 5 megaHertz mictowaves in pulses at a 1k hz rate. If the plasma field (I assume the plasma is most heavily positive ions) tat electric field could be crossed with a modulated magnetic field. (I do beleive that mag feilds can be built and collapsed at a 1000 times per second rate)(what the hell even 100 collapses a second is modulation of a sort). As RF communications impinge on the field, either from within or without, the intelligence should carry along with it to the other side. I worked at Varian Beverly Microwave in Beverly Mass. They are now called CCP industries (Google magnetrons and CCP Industries) They on line have a basic well conceived description of basic coax maggie theory. Some other high power magnetron sites are on the web too and for lenghthy studies go there, but for a good quick idea of what I'm talking about, go to CCP. I invented the voice coil tuned, anything goes ditherwise coax tube for them. That was the adaption of a magnetic field that modulated in the audio range (voice coil) to the steady state mag field of the reaction vacuum. Some very interesting mixes of closely toned freqs were produced (beating the pulse rep rate to the voice coil tune rate) And I do think it can be tested in a ground based plasma generator.
Capsules now with no talk ability weight zero, capsules with talk ability zero plus some equipment. There's no getting something for nothing. A brute force mag modulator would weigh around 100 lbs and the ancillary equipment with computerchips etc, may add a pound to that.The people at SciAm have my email address and if need be show r
Damn text limitations.
Reply | Report Abuse | Link to thisOkay, Hey, people at SciAm, if he wants them, I give my permission to give Mr. Charles H. Jones my email address or my home address which you can find at my hard copy subscription data. Merry Christmas, Mr. Jones.
Correction which I couldn't edit out of the prior post because of that text limit . It is just CPI in Beverly Mass 1-978-922-6000 and ask to speak to Don Coleman, GM.
As I think about it a little more, If not the solution, a magnetron could be built that could act as a plasma lab for you (of course swapping protons for electrons). Most magnetrons now use permanent magnets to generate the gauss field. BUT, the original ones designed in 1940 needed to use electro-magnets because there was no known mag material at the time to give dense enough field strength. If you built a maggie that had sensitive electro- magnet on it, you could see if you could pick up the intelligence imposed on the electric pulse to the anode cathode through the magnet power supply. Yes, by gosh by golly, Eureka That would show, demonstrate the technology feasibility and allow a platform to easily perform improvement experiments on. When they build it for you i'd like to run the maggie modulator if you don't mind (Besides the voice coil tuned maggie, I set up the first operational vibration of a 2MW crossfields amplifier (another possibility that CPI can talk to you about) and I was the one who outlined the equipment set up, oversaw assembly and turned up the powerwhen we tested. I would love to do it again.
Reply | Report Abuse | Link to thisGlad to see you found something new that lets you put your fertile mind to use.I wish you much success in solving this problem,wish I could imput some sugestions about the subject,but I know little about it.I will do some research and be back.
Reply | Report Abuse | Link to thisFertile mind? jack.123 are implying I'm full of sh*t?
Reply | Report Abuse | Link to thisOf course not, your abilitys far exceed mine as we both know,I am sorry that you feel my mistate was some how against your person. I will not bother you again.
Reply | Report Abuse | Link to thisNo,no jack.123. I only was making light of your choice of phrase and knew full well you intended no disreputation. Though sometimes I myself wonder from whence some of my s*it comes from. It's not always pretty nor brilliant.
Reply | Report Abuse | Link to thisOO, OO! Don't do that water in the ablate thingie! Remember Tunguska? You're talking about something like a comet supersonically pushing through the atmosphere, generating enough thermal energy to put any tritium or deuterium in the water to near the fusion point. I wouldn't even want to do any lab studies on that front. Might go BOOM!
Reply | Report Abuse | Link to thisMichael-Would a solid state maser solve some of the weight problems?I understand how you would use these technologies to transmit,but I am not sure how the craft would receive a measage?Hope it wasn't your work on magnetrons that caused the vision problems you that you have spoke of,and just wondering were the cavities of magnetrons you worked on cast or machined?
Reply | Report Abuse | Link to thiswhy not develop a communications device using quantum entanglement.
Reply | Report Abuse | Link to thisholzcman-Go to http;//www.sciam.com//article.cfm?id=entangled-photons-quantum-spookiness for a look at such a device,but I don't know if it can be adapted for this function.
Reply | Report Abuse | Link to thisThis in a way goes back to that problem I've mentioned a couple of times (I recall most recently at the atomic microscope article) that we are unable to develop anything to visually help us see through twenty feet of ocean water. We have developed ways to determine information at a distance under water using sonar and side scanning radar (That's a wonderful invention, thank you Mr. Edgerton of EG&G. His story is a marvel to rival Edison. He gave us stop action photography)
Reply | Report Abuse | Link to thisBack to the plasma. It is like a shower curtain and the underwater scenario. The material (in the curtain)is so dense that light is difused and attenuated in it's passing. By the time the photons from the originator get to the receiver, only a minute fraction still contain the information. I'm sure that some amount of signal does get through the plasma flow, but it would be so attenuated and the information shifted in meaning that to decipher the received signal would require it wet. Yoseveral amplifiers and the parallell processing of many computers. All that weight for something that we can now get in the size of a hearing aid? No, some new method needs be developed.
The ionic nature of the plasma is what I believe is mostly responsible for the shifting of data and loss of signal strength. If the signal path is shifted to a magnetic field during the brief passage through the plasma, it may arrive to the other side unchanged. It should work in both directions through the curtain. Sometimes if your curtain doesn't transmit the light efficiently due to say, surface scratches, temporary vision through is can be accomplished by getting it wet. You haven't changed the material through which you're passing the signal, but you have changed one aspect of getting the signal through and that would be the surface refraction coefficient. Once the curtain dries, you can't see through it again. I think that is how a signal can be gotten through the plasma. Change one of the parameters which are involved in the transmission. Go from electrical transmission to magnetic transmission. I'm also sure that the plasma has a small amount of magnetic property of its own, but should be very weak. That presents an avenue where we can overpower it easily. The best place would probably be dead center behind the heat shield and turn the capsule into a flaming bar magnet falling through the skies with the fields we can get to out in front of it. If the plasma field is a foot thick, we need an electromagnet that will generat a strong field to two feet.
jack.123, I see your point in the possible application of quantum entanglement as a communication device duting the blackout but also beneficially at all the other times that capsule communication is needed. The drawback as I see it is that that technology is a decade away. The Orion capsule is designed now and just needs its blackboxes designed. The mag mode reversal option could just be to take an off the shelf item and wire it backwards. No major research or development necessary(some though, yes).
Reply | Report Abuse | Link to thisI do feel that investigations and technological advancements should occur with entanglement. It has such great potential. Hopefully, something can come of it by the time the Apophis mission craft is in its design stage.
Mr. C Jones,
Reply | Report Abuse | Link to thisjack.123 is correct in that quantum entanglement may be applicable. Before a decision is made, the scientists at the site he referenced should be consulted to find out how far advanced they have developed their systems.
How is "ejecting a series of tiny relay devices" a feasible idea. Once the device is ejected it can only send data, it would have no way to transmit the commands back to the missile which is still engulfed in plasma.
Reply | Report Abuse | Link to thisI'm sorry, holzcman, I should have given you credit also for even bringing up the Entanglement possibility. Have either you or jack.123 read any of Orson Scott Card's "Ender's game" series? An important part of the technological set up for the whole series of books (well, three of them anyway, but read the others too) is entanglement communication. The future potential of the technology is exquisitely investigated and presented. Many Libraries have the series or I'm sure you can find any of them at Alibris used books on line for $1.99. Happy holidays to you all.
Reply | Report Abuse | Link to thisMichael-You are correct about holzcman having credit,I only suggested holzeman take a look at my ideas.As for Olson Scott Cards"Enders Game" no I have not read his books ,as for my ideas for a entanglement communication device,If Olson Scott Cards doesn't object to someone building one neither do I.I am going to read his books to make sure my ideas on this subject are unique,but I am sure or hope they are otherwise somebody would have built one already.Talking to the stars using this method would be a great feat indeed,or just talking to a spacecraft would be a plus.
Reply | Report Abuse | Link to thisOr, talking to friends.
Reply | Report Abuse | Link to thisMerry Christmas jack.123
Jack.123 and Holzcman, I don't want to sound like an ad but I really enjoyed reading these books. I'd rate them up there with Asimov's Foundation and Niven's Universe.
Reply | Report Abuse | Link to thisThe three books beginning the series are "Ender's Game", "Speaker for the Dead" and "Xenocide". The communications play a big part of 2 & 3 but 1 is a must read too.
Merry Chirstmas Michael and a Happy New Year.
Reply | Report Abuse | Link to thisjack.123,
Reply | Report Abuse | Link to thisI have loaded a pix of a tesseract I built. It is half of a mating pair. This is the male. I used it because it is more colorful. The female, even in heat, is a dull white which does not pic well goto::
http://www.myspace.com/514832025
I will be inputting some other things later. Like my model for the <xox> orbit.
Building on the tethered tail idea previously mentioned, but going from the other end...
Reply | Report Abuse | Link to thisWhat if a very thin (heat resistant!) antenna were to protrude from the nose at the angle of re-entry? e.g. could it project beyond the (relatively thin) plasma in front of the bulbous nose? If the presented surface area at the angle of re-entry were sufficiently small, would this reduce the air pressure at it's tip to reduce the heating (and plasma creation) enough to a. prevent the antenna vapourising, and b. pass a signal through it? It might also get around the heating and payload issues mentioned on page 31 of this article:
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD718428&Location=U2&doc=GetTRDoc.pdf
Alternatively, and more tenuously, could any of the energy loss during re-entry to harnessed to power a suitably powerful laser or magnetic equipment that could shape the plasma cone to allow a radio signal to pass through.
Kind regards
Paul Fretter
(an interested layman)
Paul,
Reply | Report Abuse | Link to thisI'm not an Atmospheric Dynamicist but my handle on that idea follows:
Picture the point of the probe being only one or two molecules wide. As the tip impinges on a molecule of oxygen at 27,000 mph, a little atomic explosion takes place. That's what you see in most shooting stars. Just a grain or two of silicon smashing into nitrogen at 70,000 mph and leaving a trail not of silicone particles for us to see but the disrupted atomic remains of the nitrogen. I tried re-reading the article and some of the postings. I'd thought someone mentioned what temperature the plasma registers at. I recall it being in the middle 10's of thousands of degrees. (50,000F?) That's why ablation works. It takes the atomic material that is being torn apart and sheds it revealing an as yet effected molecule. If your probe could be designed to "peel away" in layers and still be structurally of a harmonic wavelength of a signal , it might work, It would also be the most expensive component on the vehicle. . How does it get deployed? does it require a space walk to install it? That connection interface would fail immediately.
A little glimpse of the atom smashing that goes on can be seen here at the article about smashing a plate into the water to create supersonic air velocities (see Obsevations, Around 12-27-09).
Welcome to a Happy New Year.
why cant we build a space shuttle thats a flying wing so that they re-entry craft wont have a free fall becouse of the enormous lift produced, and the plasma will be formed only in the bottom surface
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