Plasma Stealth

[PhysicsMan]

Let’s start a list of the problems:

1. The outer hull has to standoff from the inner hull, and is therefore the de facto airframe,you’re your aerodynamics have gone to hell. Wing thickness is increased 2x the standoff distance and you have lost most of your lift and massively increased frontal resistance, if you can get off the ground at all.
2. No coverage over air intakes and exhaust. One appeal of ‘plasma stealth’ is that it is supposed to cover these areas.
3. Requires large hatches operable in flight for weapons bays, gun, cockpit, and refueling. The entire outer hull will have to be easily and quickly to remove and reattach for normal maintenance.
4. The cockpit canopy is a laminated plastic composite, not glass. Materials limitation:
   • Low impact resistance. Bird strikes happen, they just are not usually a problem unless it is the engine intake of cockpit canopy. Now it is the whole aircraft.
   • Material is a plastic, which means it is subject to permanent distortion from normal continuous loads (very low yield strength). Low tensile strength (relative to normal materials) requires small sections or large thicknesses.
   • Temperature limit bars use on leading edges, engine intakes, and engine exhaust.
5. Supporting structure for the outer hull as a source of discontinuities in plasma coverage and independent source of reflections.
6. Very high loading on all panels (14.7 psia / 1 bar at sea level) plus aerodynamic loads. Thickness will be MUCH greater than for cockpit canopy. In flat surfaces material will be under tension instead of compression.
7. There is much more, but I am too tired to keep list them.

So, NO the plane won’t work, and probably not the plasma either.

I never said it was easy to do, but none of the things you list is a showstopper, while some arguments are just strange. The aerodynamics doesn't have to suffer, the hollow outer layer doesn't need to change the shape, just follow it. Same goes for wings, nothing needs to be qualitatively different, including lift and air resistance. The example of cockpit glass (such plastics are a class of glass) is just an example of a transparent material, nothing more. Do you doubt that a material can be developed that is thinner, more heat, stress, and impact resistant and also transparent? We may not have it now but that's what makes it a problem for the future (near or far). The coverage of air intakes and exhaust with plasma is just nonsense. Hatches and disassembling is also not impossible, the plasma doesn't have to be in a single cavity, it can be in separate blocks.
Again, nothing listed here is impossible, so to say it can't be done is just shortsighted.

 

[My2Cents]

I never said it was easy to do, but none of the things you list is a showstopper, while some arguments are just strange. The aerodynamics doesn't have to suffer, the hollow outer layer doesn't need to change the shape, just follow it. Same goes for wings, nothing needs to be qualitatively different, including lift and air resistance.

How thick do you think that the gap for the plasma and the outer layer will be?

You are changing fundamental ratios between wing thickness and length, that changes the lift and stall characteristics. Thicker wings, larger frontal crosssection, more air has to move out of the way, ergo more drag, can’t be helped. Supersonic speeds also require thin wings. Subsonic transports use thick wings, supersonic aircraft need thin wings.

The example of cockpit glass (such plastics are a class of glass) is just an example of a transparent material, nothing more. Do you doubt that a material can be developed that is thinner, more heat, stress, and impact resistant and also transparent?

Plastics and glass are two entirely different things. Glass is an amorphous solid composed of small molecules, plastic is made from extremely large long chain carbon based linear molecules. Glass can be heat treated to be extremely hard, plastics are soft, cannot be heat treated, and scratch easily. Plastics are subject to plastic flow at all stress levels (No plastic flow is not unique to plastics, it is merely the range on the stress-strain diagram between where the material stops behaving elastically and permanently deforms instead, and the stress at which it ruptures/fails.).

A material that is more heat, stress, and impact resistant and also transparent (thinner is a function of mechanical properties, it is not a property itself)? Unlikely, transparency appears incompatible with the others. Best option is carbon nanotube reinforced composites, but those are opaque. They are also conductive so the signal can’t get through to the plasma.

The big problem is the huge inward forces created by the pressure differential. That are just incompatible with relatively flat surfaces.

Hatches and disassembling is also not impossible, the plasma doesn't have to be in a single cavity, it can be in separate blocks.

You need a structure to support and stiffen the outer hull. That structure will create gaps in the plasma exposing reflective surfaces. So you need a double layer, maybe even triple. Good news is that the surface in between the layers will only have to support its own weight under say 10 G’s, so fairly thin.

Again, nothing listed here is impossible, so to say it can't be done is just shortsighted.

Actually, as an engineer I can say that it is almost certainly impossible unless you can supply either a couple tons of unobtainium and handwavium, or come up with a way to position and support the outer hull by non-material means.

 

[PhysicsMan]

How thick do you think that the gap for the plasma and the outer layer will be?

You are changing fundamental ratios between wing thickness and length, that changes the lift and stall characteristics. Thicker wings, larger frontal crosssection, more air has to move out of the way, ergo more drag, can’t be helped. Supersonic speeds also require thin wings. Subsonic transports use thick wings, supersonic aircraft need thin wings.

Plastics and glass are two entirely different things. Glass is an amorphous solid composed of small molecules, plastic is made from extremely large long chain carbon based linear molecules. Glass can be heat treated to be extremely hard, plastics are soft, cannot be heat treated, and scratch easily. Plastics are subject to plastic flow at all stress levels (No plastic flow is not unique to plastics, it is merely the range on the stress-strain diagram between where the material stops behaving elastically and permanently deforms instead, and the stress at which it ruptures/fails.).

A material that is more heat, stress, and impact resistant and also transparent (thinner is a function of mechanical properties, it is not a property itself)? Unlikely, transparency appears incompatible with the others. Best option is carbon nanotube reinforced composites, but those are opaque. They are also conductive so the signal can’t get through to the plasma.

The big problem is the huge inward forces created by the pressure differential. That are just incompatible with relatively flat surfaces.

You need a structure to support and stiffen the outer hull. That structure will create gaps in the plasma exposing reflective surfaces. So you need a double layer, maybe even triple. Good news is that the surface in between the layers will only have to support its own weight under say 10 G’s, so fairly thin.

Actually, as an engineer I can say that it is almost certainly impossible unless you can supply either a couple tons of unobtainium and handwavium, or come up with a way to position and support the outer hull by non-material means.

I think you misunderstand what dimensions we're talking about here. The plasma can flow through a very thin cavity. The cavity can be paper thin. None of the issues you talk about - aerodynamics, wings, surfaces buckling in - none of that has to necessarily suffer. It's more a matter of the outer hull materials. Plastics may not be the best choice (please stop arguing about plastics not being glasses, they are. The term "glass" that you're using is good for household items. In physics plastics are glasses), but there are different possible options, including different plastics, the science of which is tremendously wide and varied. And don't confuse optical transparency with "radar" transparency. One can only apply term transparency in relation to specific radar frequencies, so whether a material is transparent to a radar (or can be engineered to be such) or not is far from being as obvious as you suggest it to be. And conductivity per se has nothing to do with whether plasma can be housed in a material or not.
As to the gaps in plasma, it's a minor engineering issue that can be taken care of with some geometry adjustments, and definitely shouldn't make it into the topic of feasibility of this technology.
Things may seem impossible if one doesn't understand them well, but as more is learned and more material science progresses, opinions change from "impossible" to "almost impossible" and then to reality.

 

[AlfaSigma]

If one rids of requirements for supersonic flight, high g, integral spheric coverage, ideal plasma gas, something worthwhile may actually still be achieved.

For example take a hypothetical attack aircraft somewhat like the Bird of Prey, put EM (laser? microwaves?) emitters (or reflectors for a source in the fuselage) at the low points of the wings, targeting a point under the nose, below. The beams excite the air passing through creating a shroud of ionized air forward and below the aircraft, sufficiently separated from the aircraft, masking it from ground radars during an approach to the target.

Granted it isn't total invisibility, and the beam would have to be optimized for certain air conditions and the visible glow would limit operation to daytime, but it seems simple enough, it can be turned on and off, it shouldn't require special materials, it could be designed to be redirectable and use more reflectors and sources.

What about that for plasma stealth?

 

[PhysicsMan]

If one rids of requirements for supersonic flight, high g, integral spheric coverage, ideal plasma gas, something worthwhile may actually still be achieved.

For example take a hypothetical attack aircraft somewhat like the Bird of Prey, put EM (laser? microwaves?) emitters (or reflectors for a source in the fuselage) at the low points of the wings, targeting a point under the nose, below. The beams excite the air passing through creating a shroud of ionized air forward and below the aircraft, sufficiently separated from the aircraft, masking it from ground radars during an approach to the target.

Granted it isn't total invisibility, and the beam would have to be optimized for certain air conditions and the visible glow would limit operation to daytime, but it seems simple enough, it can be turned on and off, it shouldn't require special materials, it could be designed to be redirectable and use more reflectors and sources.

What about that for plasma stealth?

This is in some important ways technologically more difficult to accomplish.
When plasma is generated within a cavity it can be done by high frequency EM field generation (microwave or RF, for example) very easily. and it requires reasonably low levels of power and energy. What you're talking about is different - probably not possible to generate (and sustain) with the above methods. You would need to employ high power/energy generation methods to produce very high direct current flows to achieve sustained plasma of outside air. This would be VERY energy consuming, requiring current generators difficult to imagine in a small plane.
It's possible, but not easily doable in practice (even compared to the cavity plasma method), and the coverage would be limited.

 

[AlfaSigma]

This is in some important ways technologically more difficult to accomplish.
When plasma is generated within a cavity it can be done by high frequency EM field generation (microwave or RF, for example) very easily. and it requires reasonably low levels of power and energy. What you're talking about is different - probably not possible to generate (and sustain) with the above methods. You would need to employ high power/energy generation methods to produce very high direct current flows to achieve sustained plasma of outside air. This would be VERY energy consuming, requiring current generators difficult to imagine in a small plane.
It's possible, but not easily doable in practice (even compared to the cavity plasma method), and the coverage would be limited.

What coverage are you referring to towards the end of your post?

Could you elaborate on the power requirement issue?
What is the power requirement for a 0.2mm diameter laser beam to ionize the air crossing it over a length of 10m? How long after would it recompose?

 

[Dodger67]

Plasmas produce EM radiation across a wide range of wavelenths.

Instead of hiding an aircraft, a plasma would actually light it up! They are also quite effective reflectors of radio frequencies from VHF upwards.
In short a plasma increases visibility (in the radar and optical sense) instead of reducing it.

 

[PhysicsMan]

What coverage are you referring to towards the end of your post?

Could you elaborate on the power requirement issue?
What is the power requirement for a 0.2mm diameter laser beam to ionize the air crossing it over a length of 10m? How long after would it recompose?

If direct current/arc/other direct flow discharges are used than the power required would have to be significant. For a single laser beam like you mention it may not be so high but a 0.2 mm beam produces a 0.2 mm beam of plasma - not much plasma for the purpose. A much more elaborate system would have to be employed to make use of laser generated plasma. If the laser beam is off, the plasma turns off in a small fraction of a second.

 

[PhysicsMan]

Plasmas produce EM radiation across a wide range of wavelenths.

Instead of hiding an aircraft, a plasma would actually light it up! They are also quite effective reflectors of radio frequencies from VHF upwards.
In short a plasma increases visibility (in the radar and optical sense) instead of reducing it.

The idea is that the active radar signals can be manipulated using plasma, changing the reflected beam properties, making it difficult to collect the signal. Most radars (other than the long range ones) use wavelengths that can be manipulated by plasma, hence the interest.

 

[gf0012-aust]

If direct current/arc/other direct flow discharges are used than the power required would have to be significant. For a single laser beam like you mention it may not be so high but a 0.2 mm beam produces a 0.2 mm beam of plasma - not much plasma for the purpose. A much more elaborate system would have to be employed to make use of laser generated plasma. If the laser beam is off, the plasma turns off in a small fraction of a second.

spectrum analysers detect and report anomalies within micro seconds - its one of the issues that My2Cents and I have been trying to allude to.

a plasma shield is a reflector across a range of different wave forms, its an anomaly in itself

we know this from real world testing across various institutions including DARPA, NAVSEA, ex DERA, DSTO etc....

in fact plasma generation will be picked up by a range of current organisational (not public domain) cyber management tools

 

[PhysicsMan]

spectrum analysers detect and report anomalies within micro seconds - its one of the issues that My2Cents and I have been trying to allude to.

a plasma shield is a reflector across a range of different wave forms, its an anomaly in itself

we know this from real world testing across various institutions including DARPA, NAVSEA, ex DERA, DSTO etc....

in fact plasma generation will be picked up by a range of current organisational (not public domain) cyber management tools

Yep. It's not going to make one invisible. It's a technology with lots of problems, but perhaps it could find use against targeting radars, a range where it works well.
On the generators signature. This varies depending on the kind of plasma in question. For instance, RF-generated plasma may be less susceptible to detection. In a so-called down-stream plasma configuration, the generator is located in a separate compartment, with the plasma delivered into the target chamber through a connecting tube or a cavity. That way the generator, with all of its emissions, can be completely hidden inside the plane body.

 

[StingrayOZ]

I don't see any practical way of using plasma "stealth" in a conventional air plane.

Even if you were invisible to radar its going to stand out like dogs balls (IR and other).It may also result in a much greater retaliation. If you flew over the usa/russia/china in your stealth plasma spy plane, Im sure at quick first glance its going to look somewhat like an ICBM re-entry (or something weird) and I wouldn't be surprised to see MAD style launch and scrambling everything to take it down.

Its interesting, perhaps in space there might be a more functional use for it where you don't need to worry about lifting surfaces etc.

 

[gf0012-aust]

Even if you were invisible to radar its going to stand out like dogs balls (IR and other).It may also result in a much greater retaliation. If you flew over the usa/russia/china in your stealth plasma spy plane, Im sure at quick first glance its going to look somewhat like an ICBM re-entry (or something weird) and I wouldn't be surprised to see MAD style launch and scrambling everything to take it down.

I can see the watchkeeper now... "wtf is a martin logan electrostat doing flying at mach 1 at ground level, let's send someone up for a look....?"

 

[StingrayOZ]

Well if its not being tracked by radar it might be difficult or slow to get a speed or heading at least an accurate one. Various systems would be looking for some key identifiers, it would be detectable, just not by radar.

If someone was to deploy (or look likely to deploy) ICBM with sub Mach terminal guidance (to improve accuracy? to evade terminal ballistic interception? Acquire moving targets? Can't say Im an expert but then again who would talk about what anyone is doing at that end of the business). Then looking like something coming out of hypersonic speeds would be bad.

However space can be a huge volume and using radar is a great way to search large volumes where as visual or Ir etc would not be nearly as quick. A small satellite stealthed by layer of plasma would be one tricky object to pick out.

 

[gf0012-aust]

However space can be a huge volume and using radar is a great way to search large volumes where as visual or Ir etc would not be nearly as quick. A small satellite stealthed by layer of plasma would be one tricky object to pick out.

anything that moves is in brutal terms a transducer. energy management/usage triggers detection. without going into greater detail, the algorithms pick up anomalies in a known backdrop. as in "wtf is causing that cyclic anomaly" - and then pattern matching kicks in, and then the signals forensics kick in etc.....

anything that has energy in an orbit (ie something that track management comes to grips with on a regular basis) will be identified because it creates a vacuum in its own right. not a vacuum in the literal sense but a vacuum in the sense that it becomes a traceable anomaly.

I've seen some spectacular catches by watchkeepers - it's a craft for some.

 

[StingrayOZ]

Depends how you want to operate it, if you have an object that you want to keep difficult to track and can change it orbit. I'm sure the tier 1 space players wouldn't be fooled but would make it harder for others who are just using radar to know when to hide or move. It would give a nice big return, then lose contact, orbit changed, then pops up again, then gone. Have a network of these buggers popping in and out giving multiple options and some one a headache. The concept would not to be untraceable, just a complete pain to trace and unpredictable.

I don't know if its practical but seems a whole lot more plausible than a stealth fighter made out of plastic or glass with a unblemished outer cavity acting like a big fluorescent light.

 

[PhysicsMan]

Depends how you want to operate it, if you have an object that you want to keep difficult to track and can change it orbit. I'm sure the tier 1 space players wouldn't be fooled but would make it harder for others who are just using radar to know when to hide or move. It would give a nice big return, then lose contact, orbit changed, then pops up again, then gone. Have a network of these buggers popping in and out giving multiple options and some one a headache. The concept would not to be untraceable, just a complete pain to trace and unpredictable.

I don't know if its practical but seems a whole lot more plausible than a stealth fighter made out of plastic or glass with a unblemished outer cavity acting like a big fluorescent light.

I am not an expert on plasma emission spectra, but I believe many plasmas emit in the UV/visible range, not getting into the longer wavelengths. If that is the case, than blocking such emissions is not a difficult task. I don't think it's correct to think of plasma as a source of huge amount of detectable radiation. At least, I don't think it is necessarily the case, with some engineering.

 

[gf0012-aust]

Depends how you want to operate it, if you have an object that you want to keep difficult to track and can change it orbit.

thats the theory.

however, anything that moves is using energy, and within that energy spectrum is a transducer.

as a transducer it's energy management system or its shielding causes an effect which track managers and watchkeepers identify or detect.

the same problem's have occurred with spectral cloaking. sure you can fool a given sensor, but track managers are not single solution systems

sensor 1,2,3 check co-ordinates a-b and all come back with variances, and if that variance demonstrates a degree of controlled behaviour, then its mapped against known objects in that space.

generating "wtf is that?"

can it be done - eventually, maybe - but NOT as portrayed in here.

GIS and INT track management capability would quite literally blow the socks off the general publics perceptions if they knew how capable it actually was. I've come across quite a few ex-civilian scientists who were left wide eyed when they were introduced into military sccience sandpits and ops areas.

the majority of stuff written about plasma stealth in a variety of forums is just abject nonsense sprinkled with technical mumbo jumbo to bluff an audience. populist science it may be, but its 99% of the time not science and more opinion based on a desire to have a silver bullet solution and thereby ignoring all the things that are done to track and manage objects identified as non friendly and/or unknown

plasma "stealth" looked at in isolation without involving how GIS/INT is done in hi-level militaries (less than 3), how spectrum analysis is done, materials science issues, materials science capabilities, behavioural science issues on how human factors impacts on how people perceive events and can be managed in an illusory fashion, etc... will always portray it in a seductive manner

the reality is different.

 

[StingrayOZ]

I would imagine they have some impressive capabilities. I know NASA has been keeping track of every object in space that's larger than I think 25mm in size since the late 80's using mostly radar. Paint flakes, nuts, debris etc So manned flight can avoid messy or dirty patches.

I would imagine the military would have an even better idea of what's up there using a variety of earth and space based sensors. Covering most wavelengths. I have limited exposure to what astronomers can do and I find that mind blowing. I would imagine with the far greater budget to work with and neat toys the capability would be even more so.

 

[PhysicsMan]

I would imagine they have some impressive capabilities. I know NASA has been keeping track of every object in space that's larger than I think 25mm in size since the late 80's using mostly radar. Paint flakes, nuts, debris etc So manned flight can avoid messy or dirty patches.

I would imagine the military would have an even better idea of what's up there using a variety of earth and space based sensors. Covering most wavelengths. I have limited exposure to what astronomers can do and I find that mind blowing. I would imagine with the far greater budget to work with and neat toys the capability would be even more so.

What astronomers do has very little to do with military's goals and methods/equipment. Military is just looking at orbital stuff mostly, using entirely different techniques from those used for space analysis.