How To Take Down an F-117 | Hacker News Reader

How To Take Down an F-117

strategypage.com

46 pointsjscore33 comments

We recently discussed this in another thread, but one of the low observability (stealth) characteristics of the F-117 was a reduced radar cross section (visibility) using flat sections of fuselage in a faceted manner.

This was calculated by hand by Skunk Works engineers. They didn't have the benefit of computerized physical modeling back then. They were able to reduce the radar visibility to a size about that of a bird (it's actually a little larger, iirc).

My understanding with Zoltan is that he just looked birds flying at 500-600mph. He claims that he invented all this complex, custom gear accompanied by advanced-sounding jargon, but the US military dismissed it as hyperbole (which Zoltan is known for).

The B-2 had the benefit of computer-aided physical modeling which explains it's lack of facets. The B-1 and B-52 also have low observability characteristics to reduce their radar and infrared characteristics (although they aren't known as "stealth" aircraft).

I think that stealth aircraft as we know them are largely obsolete. Hence, the increased focus on UAVs and satellites. I have some ideas about where to go next, but the costs would make the B-2 look like a Girl Scout cookie sale.

Disclaimer: I worked on many of the above-mentioned aircraft.

>The B-1 and B-52 also have low observability characteristics

I'd challenge the B-52 bit. The airframe had pretty well reached its final form by 1950. Radar was still in its infancy, let alone radar countermeasures. The plane is all radar-inviting angles (like the giant vertical stab), and there wasn't even an attempt to shield the engine exhausts from IR sensors, as IR homing weapons didn't exist at the time. I'd go so far as to say the B-52 is about as high-observable as an airplane gets.

Edit: Maybe you mean active countermeasures?

You are correct about the airframe, but the airframe wasn't what I was referring to.

http://en.wikipedia.org/wiki/Radar-absorbent_material

Active countermeasures aren't very stealthy except when you're attacking a specific detection system.

Declassified info from 1945 :) page 21 shows some jamming equipment for a B-17. Page 24 even has some spoof equipment for when you want to pretend you brought some friends along.

http://www.scribd.com/doc/33263034/WWII-Radar-Countermeasure...

PS: And it just keeps going and going. It's crazy to think how far the cat and mouse game was even all the way back then.

+blink+

Tell us more about you?

Specifically, how about an AMA?

I had to Google "AMA". Now I get it.

You can ask me anything and I'll do my best to answer. I'm still pretty guarded about info, perhaps unnecessarily, because I'm not sure what is and isn't ok to chat about anymore.

15 years ago, photographs like these would be a big no no:

http://en.wikipedia.org/wiki/File:20061027-6_b2cockpit-1-515...

http://en.wikipedia.org/wiki/File:B-52_lower_deck.jpg

This was apparently publicized at some point, as well:

http://en.wikipedia.org/wiki/AGM-129_ACM (which I view as the precursor to modern UAVs)

This was calculated by hand by Skunk Works engineers. They didn't have the benefit of computerized physical modeling back then.

Half true.

Stealth had been known to be theoretically possible [edit] for a long time. I want to say the critical ideas date to papers in the 1930's, but I'm not sure on that. I do know there were flying attempts at it in the 40's. [/edit] But nobody could really pull it off due to the sheer computation required.

Stealth happened when computers got good enough. The critical breakthrough was a computer program. Not a full blown physical model, mind you; a very specific program to solve a very specific mathematical problem created by a very clever mathematician.

But a computer program nonetheless.

-----------

http://www.456fis.org/F-117_STORY.htm

   In early 1975, the initial Skunk Works Project Team 
   consisted of Ed Martin (Project Manager), Dick Schemer 
   and Denys Overholser. Overholser had recalled a 
   discussion with his then boss, Bill Schroeder, some years 
   earlier, concerning the mathematics and physics of 
   optical scattering. The two had concluded that detectable 
   signatures could be minimized utilizing a shape composed 
   of the smallest number of properly orientated flat 
   panels. In addition, Schroeder believed that it was 
   possible to develop and resolve a mathematical equation 
   capable of calculating analytically, the reflection from 
   a triangular flat panel; this in turn he hypothesized 
   could be applied in a calculation relating to RCS. 
   Overholser had hired his former boss out of retirement 
   and as Schroeder's mathematical computations became 
   available, Overholser and his team of two engineers were 
   able to use these to write the computer program that 
   could evaluate the RCS of prospective design submissions 
   nominated by Dick Scherrer and his group of preliminary 
   design engineers. Derys and his team worked night and 
   day, and in just five weeks produced an RCS prediction 
   program known as 'Echo 1'. The resultant model was a 
   faceted delta wing design which had more than its share 
   of skeptics within the Skunk Works, some in aerodynamics 
   referring to the shape as 'the Hopeless Diamond'.

[Edit: Fact check]

The computer's were important not just for calculating the shape of the airframe, but how to fly the damn thing. You could in theory calculate the F-117 (but not the B2's) frame by hand. But flying the F-117 -or any stealth airframe - requires computer guidance.

In act, the prototype (Have Blue) just recycled some extra flight computers from the F-16 (which is unstable in one axis... the F-117 is unstable in all three).

More info here: http://en.wikipedia.org/wiki/Zolt%C3%A1n_Dani

Looks like Zoltan is a baker now in his home village in Serbia after retiring from the military.

If he was a US general, he'd have a book, do media tours all over the country, and perhaps even run for office.

He was a colonel, not a general. And even then, the US has hundreds of generals and admirals, most of which just retire and go on to a quiet 2nd career or retirement. The ones you see on CNN are the exception.

This article is really hard to read. It basically boils down to:

"He developed some ideas on how to beat stealth, based on the fact that the technology didn't make the F-117 invisible to radar, just very to get, and keep, a good idea of exactly where the aircraft was. Zoltan figured out how to tweak his radars to get a better lock on stealth type targets. This has not been discussed open"

I wish they went into more detail as to how they did that.

I would be interested to learn that as well, but that's not what "it basically boils down to." There was a considerable amount of effort in avoiding countermeasures against his radar and detection systems. He beat the stealth planes just as much by out-stealthing them on the ground as by de-stealthing them in the air. I find that just as interesting, and possibly more valuable.

Perhaps something along the lines of "Use the radar to look for the bird flying at 600mph"...

I'm not sure why andyv was downvoted, other than the fact he quoted me in a prior thread without citation? ;)

This is the conclusion the US military drew and was corroborated by Ben Rich (the "father" of the F-117) in his book.

I wish they went into more detail as to how they did that.

Well, you should expect practical information on beating stealth to be about as easy to come by as practical information on building nuclear weapons. That said, the wikipedia entry for Nighthawk has a little more information:

http://en.wikipedia.org/wiki/F-117_Nighthawk#Combat_losses

    According to NATO Commander Wesley Clark and other NATO 
    generals, Yugoslav air defenses detected F-117s by 
    operating their radars on unusually long wavelengths, 
    making the aircraft visible to radar for brief periods. 
    It is also possible that the aircraft was visible due to 
    a disruption of its radar signature caused by open bomb-
    bay doors. This was the justification given by Colonel 
    Dani in a 2007 interview.

And http://en.wikipedia.org/wiki/Stealth_technology#Radar_stealt... has information about stealth technology counters in general, the sort of thing you might find in a radar engineering handbook.

Personally, I think this bit was the key: The Serbs had spies outside the Italian airbase most of the bombers operated from. When the bombers took off, the information on what aircraft they, and how many, quickly made it to Zoltan and the other battery commanders.

My guess is, if you know how many airplanes are on their way and at what time, you can prepare. Knowing the ground speed, you can estimate when they're going to be above you and quickly light up your radar, take a pot shot, and then turn it off and scoot.

Previous discussion: http://news.ycombinator.com/item?id=799494

So he used training and tactics - isn't that rather unsporting? I thought the idea was we only flew expensive aircraft against people living in caves (or at weddings) or at least stuck to bombing those with no anti-aircraft ability.

Poor people shooting back at $Bn aircraft just isn't fair.

Who said it was unsporting?

I have to check, but I thought they used AAA to take the F-117 down. If so, such things are statistical - put enough metal in a volume of space suspected of having a plane, rinse, repeat.

If he had the intel to guestimate the location or path of a plane, it's just a matter of time before the thing gets hit.

update: some searching revealed that low-frequency/old radars picked it up and some form of SAM got it. But there were bullet holes in the wing, too. If there was a hostile fighter up, that would work if it could be guided close enough. I've read previously that old/low-freq radars would be more effective as they weren't what was modeled when the thing was built.

The stuff's not magic, although the press and popular literature makes it out as such. Far better to fly things w/o a pilot, as holding missile fragments for hostage doesn't generate much interest.

It was the missile. However, he did know where to point it well ahead of time before firing. As the article mentions, he used visual cueing and short-range shots to minimize the time his radars were transmitting.

One thing this article didn't mention: when it came to predictability, NATO aircraft were the polar opposite of Zoltan--they often flew the same routes, at the same times, using the same radio callsigns, day in and day out. This made it very easy for him to predict where an airplane would be. In the case of the F-117, I have heard that the pilot made back-to-back passes over the same target and was shot down on the second pass.

I also heard an apocryphal story about Zoltan: After the war he was "debriefed" (not really an interrogation, since the war was over and he hadn't committed any war crimes, but not exactly a friendly chat, either) in order to learn his tactics. After a while, his interviewers realized that he believed that the NATO forces were so arrogant that they had deliberately tipped their hand to him: he couldn't understand any other plausible reason why they had been so bad at keeping secrets, especially in regards to the movements of their aircraft. When they tried to explain that they had thought they were practicing good security, he refused to believe them and accused them of lying--nobody could be THAT bad at keeping secrets!

I hadn't heard that story, but I think I'd believe it.

There are a few references around to how some of his intelligence network involved people sitting outside (military) airports in Italy and phoning in when F-117's were taking off.

There's a scene in Blackhawk Down where a similar thing happens. Aided has a kid sitting around near the airport with a cellphone who calls in when he sees all the helicopters take off. I can't find any references if this actually happened or not.

Of course, this type of situation is kind of hard to avoid. Making sure that there's no one within line of sight of the take off path of an airport is kind of hard if it's anywhere close to a populated area.

I just read a story written by Jeremy Clarkson where he visited Iraq. His transport arrived and departed in the middle of the night, lights off, so that spotters couldn't determine direction or type of aircraft. So it would seem that they are acutely aware of the issue.

Being predictable isn't easy to avoid. We put so much hardware in the sky, and quickly neutralize so many of the surface-to-air threats, that aircraft are far more likely to have a close call with another friendly aircraft than to be deliberately targeted. (Not true for rotary wing aircraft.) So they're predictable, because that's the easiest way to keep two airplanes from occupying the same piece of sky, because midair collision is the greater threat. There are other ways to deconflict traffic, since so little use is made of the real capabilities of modern electronics, but being predictable also allows military air traffic to fit into the civilian air traffic control system. It's a tradeoff, and following predictable procedures resolves it while simultaneously covering a lot of asses.

Of course, as soon as one sortie aborts for a SAM threat, a concerted effort should be put into finding the source (and redoubled if it isn't found but reports keep coming in). You can be as predictable as you like if you really do own the sky.

The NATO commanders often sent their bombers in along the same routes, and didn't make a big effort to find out if hotshots like Zoltan were down there

Important safety tip: the enemy always gets a vote.

You'd need an awful lot of "metal" to cover a moving "volume" of space for an aircraft doing 500-600 mph.

Actually you need less. If you have a piece of metal occupying the cross section area of an aircraft for a certain time interval - the faster the target the more chance it has of passing through the same space as the metal.

I'm not sure your math works out in the context of the velocities we're talking about. Unless you're talking about quantum stealth... oops, I've said too much! ;)

The writing is difficult to read, but the moral of the story is good: Effectiveness = Technology * People. Zoltan had good people to compensate for antiquated technology, whereas NATO had modern tech, but the human factor negated much of the tech advantage.

Also, the title is misleading. The article is more about how to hide than how to neutralize the F-117. Being nimble, using landlines, and understanding the enemy helped Zoltan outfox those who would try to stop him.

There was also this rumour going around that f117 can in fact be detected by passive systems Tamara and Vera. see http://72.52.208.92/~gbpprorg/mil/radar/tamara02.htm

Optimisation for stealth against bistatic and multistatic radar systems is a different problem from the monostatic case. The important thing is the split between the position of the transmitter and receiver. In the monostatic (transmitter and receiver in the same place) case, you need to optimise to reduce radar energy reflected back in the direction of the transmitter.

When the receiver and transmitter are split, this problem gets harder, because you need to optimise to reduce radar energy transmitted back in the direction that recievers are likely to be (or don't reflect any, but that's a different problem). This becomes even harder in multi-receiver systems, and even harder in multi-receiver-multi-transmitter systems. As computation power and communication bandwidth becomes cheaper, lower power, smaller and easier to hide, many of the assumptions used during the development of the current generation (and past generations) of stealth aircraft are becoming invalid.

Passive location systems, either secondary radars or systems using 'transmitters of opportunity' also reduce the effectiveness of anti-radiation weapons significantly.

The radar vs. stealth arms race continues.

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