Low Observability · 10:15am Mar 1st, 2015
More frequently, though incorrectly, referred to as stealth.
And if you don't learn the difference, beavers and songbirds will kidnap you whether you're wearing your low observability suit or not.
Stealth implies invisibility. Low Observability (LO) is both more accurate and lends itself to include many technologies and techniques.
When you hear about this stuff, something like the radar-evading F-22 fighter jet probably comes to mind:
But there’s a lot more to both LO and the platforms it applies to.
The history of LO begins with camouflage. More sensitive sensors than human eyeballs required better counters than just painting things different colors.
LO can benefit just about anything, but it's mostly been driven by aviation. Not only do radars respond better to high-flying targets than surface targets, but airplanes lose more of their speed advantage when they can be detected hundreds of miles away.
During World War Two, the military experimented with making aircraft brighter by putting lights on them. Project Yehudi sounded crazy, but making an aircraft brighter against a bright sky actually did help.
A picture of Yehudi Lights on a Grumman Avenger. "Yehudi" is a Hebrew name, probably just picked as a random word to name the project.
The lights were never adopted because the invention of radar made planes easier to spot and at longer ranges.
That doesn’t mean deceptive lighting doesn’t have its place. You can rig lights on your aircraft carrier to make it look like a fishing boat. If you run with no lights at all, you are much less observable.
However, it’s not all about hardware. You have to be smart about how you use it and develop tactics that complement the equipment. Your fishing boat can’t launch aircraft. The F-22 has a really great radar, but if the pilot turns it on, the enemy can detect the signal.
Still, it’s mostly about hardware. Let’s talk about that.
Since we’re talking about radar, a way to compare the observability of various platforms is with radar cross-section (RCS). This is a rough guide to how large the thing appears on a radar screen, usually measured in square meters. A one square meter piece of metal has an RCS of one square meter.
The primary factor in RCS is overall size. A large B-52 bomber has an RCS of about 100 meters squared. A small MiG-21 fighter jet from about the same era has an RCS of about 3 meters squared. To really trim down RCS, though, you need advanced designs.
Check out this crazy-looking airplane:
F-117 Nighthawk
The faceted surface helps it evade radar. Remember how radar works: the system sends out a pulse of energy that bounces off the target and returns to the receiver. The F-117 is shaped so that when radar hits it, it bounces away in another direction.
Despite being slightly larger than the previously mentioned MiG-21, the F-117 is estimated to have an RCS equal to a small fraction of a square meter. For fun, let’s call it basketball sized or about 1/10 of a square meter. That’s a heck of a lot harder to detect than even the MiG’s 3 square meters, which is probably about twice the size of the door of the room you’re currently in.
Also note a few other things: The sawtooth edges around the F-117 canopy make it so there isn’t a straight line to reflect radar on the front of the aircraft. The engine intakes are covered with a screen. The holes in the screen are sized so that radar waves of certain frequencies can’t pass through them. (see my blog Electromagnetic Radiation for more on this)
LO shaping is not a new idea. Look at this picture of an A-12, predecessor to the SR-71. Note the sawtoothing on the edges of the fuselage. This picture was taken in 1962.
It’s only recently that we’ve come up with better materials and manufacturing. Reflecting radar waves in a different direction is nice, but if you have a radar absorbent material (RAM), it does as advertised and reflects less, no matter the direction. The F-22 still has a reflective shape, but not to the same extreme as the F-117. The RAM it’s coated in is better, and is not as susceptible to weathering. The F-22 is a better, more durable aircraft because of advances in materials, not necessarily advances in shaping.
Having said that, it’s very difficult to get something that is LO in every direction. So you compromise, figuring out where a threat is likely to be. Look at this picture of an F-22:
Notice how the leading edges of the aircraft are all perfectly parallel to each other. The designers purposely made it more visible on radar in that one direction, in order to make it less observable in most other directions.
This feeds back into my prior comment about tactics. F-22 pilots probably have to do things a little differently than those who fly other kinds of aircraft.
Speaking of other kinds of aircraft, I’ll throw in this picture of the B-2 bomber:
Aside from sawteeth everywhere, notice how the engine exhausts end while there’s still plenty of fuselage left. This helps the hot exhaust cool down, but also shields it from anyone observing on the ground. It can also cut down on noise. Being hard to detect with radar is great, but someone hearing or seeing the plane could still blow its cover.
As LO becomes more common, heat-seeking missiles could become a counter to radar-evading planes. Dedicated Infrared Search and Track (IRST) systems on fighters are becoming more popular. The F/A-18 Super Hornet is testing one right now.
Super Hornet – because I can’t go one blog without posting Navy jets. Also, sawteeth on the landing gear doors. The Super Hornet isn’t low observable per se, but it’s new enough and incorporates enough tricks that it can be considered lower observable, at perhaps 1 square meter.
We may not be able to make a perfectly invisible jet, but making a jet harder to find gives us more options. We can push deeper into enemy territory, make it harder for missiles to get a lock, or create lots of cool conspiracy theories for people who watch the skies around Area 51.
Speaking of advanced technology, radars are becoming better, and could eventually make LO obsolete. Information sharing with datalinks between platforms will be more important as time goes on, but it will become harder to pass signals back and forth while staying undetectable. There's also been talk about using plasma fields to absorb radar waves. It’ll be interesting to see how everything plays out in the future. If radars get too good, jamming could become the only way to defeat them.
In a way, jamming is a kind of LO. Not a subtle kind, but blinding the enemy radar does deny them the opportunity to shoot at you. This again feeds back to using heat-seekers.
It’s a cycle. One technology advances and requires others to advance to beat it. LO also requires constant maintenance to ensure that there are no loose screws or weathered coatings that might cause degrades.
To be final, LO is about blending equipment and procedures. You have to have the whole package to make it work: design, materials, and tactics.
Of course, all this is irrelevant to your story because ponies don’t have radar.
Not with that attitude they don't
2839849 I've never seen a MASH/MLP crossover...
2839852 So what you are saying is that there is room in the market for that...
There's a fabric being developed that makes people partially transparent.
Edit: That F-22 shock diamond!
Maybe they have locate object spells, and to evade them your plane has to look like something that could never possibly fly?
"no flying creatures on the crystal ball, but apparently we're being attacked by a flight of supersonic lawn darts?"
Dang, I was hoping for actual camoflauge and stuff like razzle dazzle. The thing about lights was really cool, though. That's a really innovative idea.
Also, no mention of the F-35 at all.
2840203 Yeah, I think cammo is a whole other blog. This focused on beyond-visual-range stuff.
I hear that the F-35 second hardest to see aircraft in the world. The first is the F-22. But there's a lot about the F-35 that I'll believe when it's proven.
The F-117 is special to my family as my uncle worked on it
2839852
Dude... there is one, give me a moment... Healing for a Spell
Human LO in terms of campaint:
Paint the dark parts of your face (sunken areas like eyes, ears, neck etc) with light colours, and the non sunken parts with dark colours.
This gives you a much less defined look, meaning you look more natural.
Also never use black. Almost nothing in nature is black.
Think you could do one about Dazzle camo?
Hm, I am a bit late to the party here, but there are several important factors that are going to kill LO aircraft in the next few decades.
The first is LIDAR which is a lot like RADAR, but it uses lasers in other parts of the electromagnetic spectrum to detect objects which can allow it to bypass RAM coatings. This could obviously be defeated similarly to radar, but doing so adds another band the coating needs to deal with which is going to cause problems and could get to the point where it is unmanageable if the detector uses a tunable laser capable of operating in a wide range of frequencies.
The second is Doppler Radar. While this technology has been around for a while to observe weather, I think it will get a lot of interest from the military in the future for the simple reason that it can detect a stealth aircraft by detecting the air it displaces as it moves. Even if you can make an aircraft that is truly invisible to radar, physics demands that it has to displace air to fly so you can always spot it by the effect it has on the atmosphere. This may not be good enough to pinpoint it exactly enough to hit with a gun or missile, but it can definitely locate it accurately enough to use other methods of target acquisition to hit it.
The third is optical video processing. While it may seem primitive, computers and video cameras are to the point where we could realistically use optical tracking to guide a missile to a target. No aircraft to date has been built with any way to defeat this technology, although countermeasures are being developed for ground systems so they could theoretically be moved to aircraft if necessary.
The fourth is thermal imaging. While there are ways to defeat heat seeking weapons looking for the very hot jet exhaust by cooling it down on its way out, the physics of flight will cause the skin of the aircraft to heat up even at relatively low speed so thermal imaging technologies developed for ground applications could be used to locate aircraft detected with Doppler Radar for a combined engagement system which operates purely on the physics of flight which makes it impossible to avoid detection.
When you combine these trends with the emergence of effective hardkill missile defenses, I think the sixth generation fighters are going to look radically different from what we are seeing now with lasers to shoot down incoming missiles, large missile capacities to attempt to saturate defensive systems, and an increased focus on short range engagements to minimize missile flight time and exploit systems like guns and lasers which cannot be intercepted. The really strange thing about this is that the A-10 might actually wind up being a better air superiority fighter than the F-35 and even the F-22 in a few decades because of how hard it will be to shoot down an A-10 when you fortify its already robust defenses with an anti-missile laser and hang a huge number of Sidewinders off its plentiful weapon pylons.
3318143 It's interesting to think about. We could advance in sensors to the point that it's not even worth trying to hide anymore, in which case the laser A-10 would become king, or we could advance in jamming to the point that nobody can see anything except with the naked eye.
I once thought about doing a story involving a war in the South China Sea, where, through a combination of space warfare eliminating everyone's comms and navigation satellites and hugely powerful jammers on all sides, modern ships were left to duke it out old school, within visual range.
3318173 The thing is, you can also use a jammer to get an approximate location of an aircraft even if you cannot use it to fully guide in an anti-radiation missile. Once it gets close, it can just switch to optical homing with a camera to get a good clean hit so jamming is not an ultimate solution. That puts you back to the lasers and close combat, although you would probably want something with more raw speed than the A-10, especially because those airframes are wearing out and will have to be retired soon weather we have a functional replacement for them or not.
But yeah, it is definitely interesting to think about and it will be very interesting to see how things wind up shaking out in a few decades.