I've been reading up on plasma flow control, which is pretty fascinating. It looks like there are some near-term opportunities for plasma flow control on commercial airplanes (on the leading edge of wings) to improve efficiency.
This is pretty "out there." Conceptually it makes sense but the comment in the article that carrying along a power supply to make this practical cuts back on the efficiency.
That said, the idea of super heating the air in front of the leading edge so that the dense air in front goes around seems pretty amazing. But I am not sure I understand how the same super heated air doesn't result in the same heating they were trying to avoid.
Only this time in air and using plasma instead of pressurized gas - preatty high tech. As for the power source, I guess they could use chemical lasers. Also the faster it can get the less time the lasers need to run.
Yes, It is actually. I wound up pretty far down this rabbit hole while learning about re-entry dynamics.
The issue with “normal” hypersonic drag is the pressure shock front is “attached” to the surface of your “plane”. Which means that location is subjected to the thermal loads induced by the shockwave compression. What they discovered back in the early days of manned space flight (and icbm development) was that there is a relationship between how pointy you make something and the detachment of that shockwave. The bi-conic space capsule shape were all familiar with from the Gemini and Apollo program pushes the hypersonic shock wave completely off the surface!
This means that you have way less heat to work deal with... but that shape is ideal for re-entry, when your trying to slow down. Not for when your trying to go faster. As a result there’s been heaps of aerodynamic engineering research since the 60s on how to get similar detached shock fronts while maintaining aerodynamic control over the vehicle.
All jokes aside, the other outcome was the realisation that by artificially inducing a plasma at a lower temperature in front of the airframe they could both aim to control the shape, composition and temperature of the plasma while also improving aerodynamic control, and minimising plasma heating and RF blocking, radar signature, all while still benefiting from the re-entry like effect of pushing the heated shock front entirely off the airframe. There’s been a fair bit of small scale wind tunnel testing over the years, some of which is available in the NASA technical reports server archives.
I'm sure there's been at least research in this area since the 1980s - I remember hearing about it when I worked in the Defence industry on weapons systems in the early 2000s as an improvement over the default static "Spike" on existing high-mach-number vehicles (ICBMs for example)...
As mentioned in the other comment, Supercavitation for torpedoes have existed for a while, which in some ways can likely be argued to be similar (altering the medium the body is in to reduce drag).
Could this idea work for rockets leaving earth? Use a ground based laser to create a hole in the atmosphere then fly a rocket thru it to space.
Edit: Some quick research seems to indicate that atmospheric drag is a relatively small part of the overall energy budget in a space launch - perhaps only 10%. So probably not worth the effort.
10% is a huge reduction and would significantly add up to cost savings with the potential it compounds savings. I think it’s certainly a possibility. Might eventually be a focus for Space X.
I always thought the issue here is the difficulty getting radio waves through plasma for these weapons. So once the plasma is turned on, it's radio silence/the device is on it's own. There would be no GPS getting through, so if the trajectory is off you can't fix it. Has there been any success in getting EM through plasma?
Yes:
Sha, Y. X., Zhang, H. L., Guo, X. Y., & Xia, M. Y. (2019). Analyses of electromagnetic properties of a hypersonic object with plasma sheath. IEEE Transactions on Antennas and Propagation, 67(4), 2470-2481.
So if they are moving this idea forward, it suggests they've succeeded at solving plasma blindness I would assume. What does "non-kinetic components' survival" mean?
I saw a city bus flashing a message along the lines of "stop the spread" / "wear a mask" along with the usual other stuff, and I just kind had a sense of unreality, as if I were dreaming about a science fiction movie or story that I'd seen. A frighteningly plausible plague or zombie movie. I mean, I'd gotten used to it, but then I suddenly flash back to the perspective of a year ago, or ten, or twenty.
An idea I had, which I will never use to write an SF novel, but anyone is welcome to steal, though it's kind of dumb and definitely not well grounded in science, is...suppose that humans are all the intelligence there is in the universe, and in the near future, something is going to wipe us out, maybe some kind of wibbly-wobbly quantum observer effect is making probabilities spread out and become fuzzier in advance, the closer we get to the event. I'm kind of imagining that the wave functions are all sort of un collapsing as we get closer to their being no observers.
As if there was an improbability generator a la Douglas Adams, but due to a purely natural effect of physics.
I can see how this reduced drag on solid parts, but does it not also operate as an engine? The laser energy is projected forwards to hit molecules of air out in front of the aircraft. Those molecules are heated and so expand (the shockwave) but are they also not accelerated forwards? Yes, the laser is effectively pushing the air out of the way, but is that energy more or less than the energy needed to push the air away using mechanical force? Ie is putting energy into the laser more efficient than simply using that energy to increase the power of the engines?
In other words, rather than use the laser to expand air in front of the craft, would it be more efficient to use the laser to expand air in the engine to increase thrust?
The calculation depends on the specific configuration of the vehicle, but yes, friction-reduction can be a better use of (some amount of) energy, rather than increased thrust.
E.g. hovercraft.
Edit: This concern is also addressed int he article.
>> He pointed out that efficiency is key to energy depositions for drag reduction, as the levels of drag reduction must be weighed against the added weight and power requirements. “The drag reduction system has to be more efficient than what you could get out of an engine or it doesn’t make sense to use drag reduction; you’d just build a bigger engine.”
"U.S. military is still the world’s top petroleum consumer and largest carbon polluter. Between 2001 and 2017, the five military branches collectively emitted 1.2 billion metric tons of carbon emissions, twice the annual output of all the passenger vehicles nationwide."
So in 17 years the US military emitted as much as the US passenger vehicles in 2 years? What exactly is their definition of “the world’s largest carbon polluter”?
If we're talking about large entities as polluters, more realistically China's coal industry is the world's worst carbon polluter by a dramatic margin. The global coal industry is half of all human-sourced CO2 output on the planet and China's coal industry is larger than the rest of the world's coal industry combined. Worst of all, they're aggressively adding a lot more coal plants to their grid.
Since at least the 1980s, many leading aerospace laboratories have explored the concept of "energy deposition" in order to reduce drag. This concept involves beaming energy in the form of laser filaments, electric arcs, or microwave radiation along the leading edges or just in front of an aircraft in order to condition the air to be more conducive to high-speed flight.
It's really cool stuff, straight up science fiction, we're living in the future and all that.
Buuuut wouldn't it be nice if all that Sciencing that is figuring out how to tightly control plasma in the most extreme of conditions was applied to something like, say, developing fusion reactors to solve our existential energy problems instead of making faster boom-booms that rain Revelations-style death and destruction down from the heavens?
I mean, don't get me wrong, some technologies can just be weaponized no matter what so bits of the fusion plasma research would still get siphoned off into some black budget somewhere. Let's be realistic here. But wouldn't it be nice if the knowledge trickle-down was going in the direction of solve-our-big-problems first, then worry about the self-apocalyptic boom-booms?
Think in terms of kinetic kill devices. Launched from orbit could cross atmosphere in an extremely short time at high angle giving basically no time to react. No warhead would be needed because it would be able to penetrate and kill anybody or anything within most existing standing structures.
Does one have anything to do with the other? Recent Gov announcement of materials or craft not from this world? Black Op Programs at Area 51? It's all very interesting.
>Department of Defense (DoD) funded laboratories have laid the groundwork for systems designed to literally sheathe an entire vehicle in laser and/or microwave-induced plasma in order to drastically reduce drag. If successfully developed, this concept may someday lead to new frontiers in speed and radical new forms of aerodynamic control and aircraft design.
>but it’s another thing entirely to attempt to intercept a projectile moving at speeds greater than five times the speed of sound while executing abrupt changes in trajectory.
The main revelation is that technology exists that is capable of performing flying maneuvers that shatter our perceptions of propulsion, flight controls, material science, and even physics. Let me underline this again for you, the Nimitz encounter with the Tic Tac proved that exotic technology that is widely thought of as the domain of science fiction actually exists. It is real. It isn't the result of altered perception, someone's lucid dream, a stray weather balloon, or swamp gas. Someone or something has crossed the technological Rubicon and has obtained what some would call the Holy Grail of aerospace engineering.
detonate the air in front of the wing, and surf the shockwave. This research happened in California by any chance?
Apologies if its addressed and i just missed it in the article; but doesn't this seem energy hungry? Like "what power source can we make fly that can do this output?"
It’s not as energy hungry as you might think because there’s a significant energy input due to the shockwave shedding thermal radiation and hot gas/plasma from its “inside” edge. The clever thing here is controlling the inside edge of the shock front as opposed to just letting it form as it would normally do and by controlling it to shift the shock front away from the airframe to reduce drag.
It also has potential to produce quieter drones. https://en.wikipedia.org/wiki/Plasma_actuator
Finally, I'm particularly interested in the use of large-volume plasma-based propulsion in airships. https://iopscience.iop.org/article/10.1088/1742-6596/825/1/0... "First Breakthrough for Future Air-Breathing Magneto-Plasma Propulsion Systems"