5 ms·

Allegedly it creates a plasma shield which has a radar-shielding effect, in addition to reducing drag (and maybe actually moving the air). But yeah, you'd think

by nkoren 10y ago

Allegedly it creates a plasma shield which has a radar-shielding effect, in addition to reducing drag (and maybe actually moving the air). But yeah, you'd think that the RF signature would be unmistakable...

hengheng 10y ago
A radar-shielding plasma shield sounds a bit like having a speaker wall to mask conversations.
- jacquesm 10y ago
  Welcome to 'anti-sound': https://en.wikipedia.org/wiki/Active_noise_control https://en.wikipedia.org/wiki/Active_noise_control If the 'wail' is carefully tuned to the original forces dragging on the craft it might actually work.
- ridgeguy 10y ago
  More like a sonic absorber. Plasmas are electrical conductors. The electric field of an incident radar wave couples to electrons and ions that compose the plasma and drives currents. This ends up dissipating the radar energy as heat. It's the same result as if the radar hit a poor electrical conductor like carbon-loaded plastic: not much reflection (cause of poor conductivity), but creation of internal currents that dissipate radar energy as heat. It's a resistive dummy load for the radar energy. This plasma-as-conductor thing can lead to some really interesting antennas. [1] Fill a long plastic tube with an easily ionized gas, and connect the output of your radio transmitter to it. When you want to transmit, ionize the gas column with a high voltage, low current discharge. Voila, you have a nice conductive column to radiate your RF from. Finished with transmission, switch off ionization power. Antenna is then electrically gone. Very important if you're on a battlefield, being hunted by things that can find antennas made out of metal. Your plasma antenna can be there and gone in a millisecond. Phased-array models exist, too. [1] https://en.wikipedia.org/wiki/Plasma_antenna https://en.wikipedia.org/wiki/Plasma_antenna
sandworm101 10y ago
Drop the plasma. What is has are, potentially, some directional antennas capable of attacking inbound radar. But imho it doesn't have even that. This is 1980s/90s tech. It's a quiet bird, as opposed to something like and EW/weasel jamming platform. I doubt it does anything active. Now it may have some conductive material meant to absorb and play tricks with RF, giving the appearance of some magnetic shield, but I don't think it is deliberately broadcasting, at least not in any omnidirectional way remotely similar to a force field. One active trick is does do, and has been confirmed by ATCs all over the place, is transmit transponder data as if it were a commercial aircraft while in civilian/peaceful air space. This prevents enemy spies from detecting a mission launch and direction, but has raised concerns amongst legal minds. It's akin to a soldier wearing civilian cloths while travelling behind the lines ... but such principals seems to be falling by the wayside these days.
- paulmd 10y ago
  "Directional antennas for attacking inbound radar" is essentially what all jamming does. You send emissions of your own that mess up the returns from the radar. This can be as simple as just blasting noise to make the return indistinguishable from the noise, but the ability to send "false" returns has been around for quite a while. I wouldn't be surprised to hear that they could send an out-of-phase signal to cancel the pulse (like noise-cancelling headphones), but the catch would be that the signal probably wouldn't be perfectly cancelled except in a specific direction (back towards the source) and you could probably detect that. As such I would be surprised to see it on the B-2. The other thing is that when stealth aircraft are in civilian space they attach/deploy radar targets that give the aircraft a perceptible return for safety's sake. Un-deploying a radar target would look the same on radar as deploying a "stealth field" so that could be an origin of the rumor...
  - sandworm101 10y ago
    They don't 'deploy' anything. There are no radar reflectors. They just turn on their transponders and anti-collision gear (ACAS). Civilian radar doesn't generally detect reflected energy. It just listens for transponders, which are infinitely more powerful than any reflections. Turn those off and civilian ATC is practically blind whether you are a stealth bomber or 747.

by nkoren 10y ago

hengheng 10y ago

A radar-shielding plasma shield sounds a bit like having a speaker wall to mask conversations.

jacquesm 10y ago
Welcome to 'anti-sound': https://en.wikipedia.org/wiki/Active_noise_control https://en.wikipedia.org/wiki/Active_noise_control If the 'wail' is carefully tuned to the original forces dragging on the craft it might actually work.
ridgeguy 10y ago
More like a sonic absorber. Plasmas are electrical conductors. The electric field of an incident radar wave couples to electrons and ions that compose the plasma and drives currents. This ends up dissipating the radar energy as heat. It's the same result as if the radar hit a poor electrical conductor like carbon-loaded plastic: not much reflection (cause of poor conductivity), but creation of internal currents that dissipate radar energy as heat. It's a resistive dummy load for the radar energy. This plasma-as-conductor thing can lead to some really interesting antennas. [1] Fill a long plastic tube with an easily ionized gas, and connect the output of your radio transmitter to it. When you want to transmit, ionize the gas column with a high voltage, low current discharge. Voila, you have a nice conductive column to radiate your RF from. Finished with transmission, switch off ionization power. Antenna is then electrically gone. Very important if you're on a battlefield, being hunted by things that can find antennas made out of metal. Your plasma antenna can be there and gone in a millisecond. Phased-array models exist, too. [1] https://en.wikipedia.org/wiki/Plasma_antenna https://en.wikipedia.org/wiki/Plasma_antenna

sandworm101 10y ago

Drop the plasma. What is has are, potentially, some directional antennas capable of attacking inbound radar. But imho it doesn't have even that. This is 1980s/90s tech. It's a quiet bird, as opposed to something like and EW/weasel jamming platform. I doubt it does anything active. Now it may have some conductive material meant to absorb and play tricks with RF, giving the appearance of some magnetic shield, but I don't think it is deliberately broadcasting, at least not in any omnidirectional way remotely similar to a force field. One active trick is does do, and has been confirmed by ATCs all over the place, is transmit transponder data as if it were a commercial aircraft while in civilian/peaceful air space. This prevents enemy spies from detecting a mission launch and direction, but has raised concerns amongst legal minds. It's akin to a soldier wearing civilian cloths while travelling behind the lines ... but such principals seems to be falling by the wayside these days.

paulmd 10y ago
"Directional antennas for attacking inbound radar" is essentially what all jamming does. You send emissions of your own that mess up the returns from the radar. This can be as simple as just blasting noise to make the return indistinguishable from the noise, but the ability to send "false" returns has been around for quite a while. I wouldn't be surprised to hear that they could send an out-of-phase signal to cancel the pulse (like noise-cancelling headphones), but the catch would be that the signal probably wouldn't be perfectly cancelled except in a specific direction (back towards the source) and you could probably detect that. As such I would be surprised to see it on the B-2. The other thing is that when stealth aircraft are in civilian space they attach/deploy radar targets that give the aircraft a perceptible return for safety's sake. Un-deploying a radar target would look the same on radar as deploying a "stealth field" so that could be an origin of the rumor...
- sandworm101 10y ago
  They don't 'deploy' anything. There are no radar reflectors. They just turn on their transponders and anti-collision gear (ACAS). Civilian radar doesn't generally detect reflected energy. It just listens for transponders, which are infinitely more powerful than any reflections. Turn those off and civilian ATC is practically blind whether you are a stealth bomber or 747.