The SR-71's predecessor used cesium-laced fuel to create radar-absorbing exhaust

https://www.thedrive.com/the-war-zone/29787/the-sr-71-blackbirds-predecessor-created-plasma-stealth-by-burning-cesium-laced-fuel

by ivanech • 7 years ago

308 139 7 years ago

thedrive.com

liability• 7 years ago

That's one hell of a "chemtrail"!

robohoe• 7 years ago

If you're curious about the development of Oxcart as well as Area-51, check out Amy Jacobson's Area 51 book[1]. Appears like a solid detail of Skunkworks and spy plane history.

[1] https://www.amazon.com/Area-51-Uncensored-Americas-Military/...

syntaxing• 7 years ago

I know it's toxic but from a technical aspect, that is really cool. I remember reading that the Apache Helicopter (I think?) can redirect it's exhaust internally temporarily to become invisible to heat seekers. Some of these technologies are super fun to read about.

vvanders• 7 years ago

Some of the stuff to restart the afterburners was pretty nasty too. I think it was one of the hypergolic families if I remember correctly.

IcePenguin• 7 years ago

Yep! It's called TEB (Triethylborane). More info here: https://en.wikipedia.org/wiki/Triethylborane

JP-7 has a very high ignition temperature (it was actually used as a coolant/heat sink for the rest of the aircraft), so TEB combusting once it hit the air is used to light the engines.

SR-71s only had a limited amount of TEB to use each flight. I believe it was 13 shots per engine. TEB was used each time the engines were lit and also when afterburners were lit. While the SR-71's routes were built around refueling, the number of TEB shots remaining were the true limiting factor of the SR-71's flight time.

coolspot• 7 years ago

Most military helicopters having some ways of masking IR signature: https://www.sciencedirect.com/science/article/pii/S100093611...

austinheap4• 7 years ago

1960s designs cannot be masked against modern FLIR arrays so old rotorcraft still in service are just retrofitted to discourage detection.

decoyworker• 7 years ago

https://en.wikipedia.org/wiki/Common_Infrared_Countermeasure...

Infrared guidance systems in heat-seeking missiles are designed to track strong sources of infrared radiation
Directional IRCM, or DIRCM, allows for a countermeasures laser to be targeted directly at an incoming IR threat.

blackflame70006• 7 years ago

It depends. If its regular Cesium 133 then it's harmless compared to Cesium 137.

taneq3• 7 years ago

The Comanche vented its turbine exhaust into the wash from the tail rotor, iirc, to make it harder to spot. It also used a 5-blade rotor instead of the traditional 2-blade rotor in order to make it quieter. There's a bunch of cool things we could do to make helicopters more stealthy if we cared enough.

DuskStar5• 7 years ago

And if you look at the US Army's Future Vertical Lift competition, [0] you can see some indications that those techs might make it into our future helicopters.

0: https://en.wikipedia.org/wiki/Future_Vertical_Lift

Daniel_sk• 7 years ago

There is some stealth helicopter model that is secret and was used in the operation to kill Osama, it may be a heavily modified UH-60.

tempguy99992• 7 years ago

I know it's toxic but from a technical aspect, that is really cool.

People who think like this make want to cry. Those who can see the consequences and choose to overlook them.

jacobush4• 7 years ago

You comment is toxic but from a technical aspect, really cool. I choose to overlook it.

cafebabbe• 7 years ago

"I know it's toxic but from a technical aspect, that is really cool"

is a great alternative HN tagline

skunkworker• 7 years ago

If you haven't read it, Skunk Works: A Personal Memoir of My Years at Lockheed by Ben Rich is a pretty fun read into the U2, A-12 Oxcart, SR-71, Sea Shadow and other craft. And has a lot of good stories from pilots.

But the ultimate SR-71 book would be Sled Driver: Flying the World's Fastest Jet.

galangalalgol2• 7 years ago

The sr-71 gets all the glory but go look at some of the aircraft that lost competitions. The convair kingfish that lost to the 71 was decades ahead. It lost for a number of reasons, some valid, some not. The f-22 competitor was super interesting as well.

aidenn0• 7 years ago

Yeah, the YF-23 wins a lot of cool points on looks alone[1], and it was faster and stealthier than the F-22. Taking the -22 was probably the right choice given that it was lower risk and absurdly better than anything it's likely to encounter in its operational life.

1: https://en.wikipedia.org/wiki/Northrop_YF-23#/media/File:YF-...

nunb• 7 years ago

YF-23 actually looked futuristic, the F-22 looks like a mild modernization of the F-15/18

justin66• 7 years ago

The convair kingfish that lost to the 71 was decades ahead.

It was never built, let alone flown.

selectodude• 7 years ago

The Convair Kingfish never actually existed and the A12 flew higher, farther, cost far less and Convair couldn’t put an aircraft in the air on time or on budget to save their lives.

1986• 7 years ago

I actually just finished reading Rich's book, it's both interesting and entertaining.

dboreham• 7 years ago

Funny story: decades ago I bought a copy of Sled Driver. I think it was in that remainder/coffee book section of the book store near the front, so it was probably $10.

Today they sell for $200-$350 used.

Due losing track of the first copy, buying a second one (when they were available new), then finding the first copy, I have two copies and high hopes of them funding my retirement..

cyberferret• 7 years ago

I've got a copy of one of the first print runs that a friend gave me decades ago. About 10 years ago, I use to see them on eBay for up to $3000, but the prices have dropped recently as I believe they had another print run done.

tlb• 7 years ago

It’s also not clear from the available records how much [cesium] was necessary per gallon of [jet fuel]

Come on, you lazy reporter! Go find a jet engine and some cesium and a radar reflectometer and make a graph of reflectance vs. cesium content.

Presumably, some engineer at Lockheed in the late 50s got exactly that assignment, with a budget. There would be a notebook with a table of numbers and a hand-drawn graph. Those would be amazing to see.

VonGuard• 7 years ago

I have visions of exploding journalists....

For Reference: https://www.youtube.com/watch?v=m55kgyApYrY

taneq3• 7 years ago

Do you have visions in higher than 240p? :S

taneq3• 7 years ago

I would love to see some kind of web database of old engineering notebooks like this, surely there are enough now kicking around in boxes of "grandad's junk".

CamperBob2• 7 years ago

A nice one from Tektronix, c. 1979, just surfaced:

http://w140.com/tekwiki/images/b/bd/Tek_7854_design_team.pdf

faizshah2• 7 years ago

Some cool ones here: https://www.computerhistory.org/collections/fairchild/

Would be cool to see some old notebooks from Bell Labs tho like Ritchie or Thompson. I just found some old AT&T training manuals on Perl, TCP/IP, Bash, C and Unix internals, they are really cool.

mNovak• 7 years ago

I realize this is a joke, but just wanted to add that Rogoway is a consistently great and thorough writer on defense subjects. I've been reading his stuff since the Foxtrot Alpha days.

nabla9• 7 years ago

I completely different view. Rogoway's is not into critical thinking or good analysis. He is also deeply into monetizing Navy-UFO conspiracy.

ridgeguy• 7 years ago

Well, what I could find quickly comes from the 1960s, out of Avco Laboratories and the Naval Research Labs:

"Plasma Diagnostics in Supersonic Flow Containing Cesium and Potassium" [1] Burn Cs in a rocket engine, check for absorption up to 70 GHz (or cps, in those days). Looks like fun work.

[1] https://ieeexplore.ieee.org/document/4323385 (paywalled)

Kliment• 7 years ago

https://sci-hub.tw/https://ieeexplore.ieee.org/document/4323... (anti-paywalled)

treggle• 7 years ago

Of course, because nothing matters more than getting the advantage.

Same line of thinking that results in depleted uranium tank shells.

amluto• 7 years ago

Cesium (in the +1 state) appears to be barely toxic at all. Wikipedia puts its LD50 around that of sodium. Cesium metal is extraordinarily dangerous, but it’s so reactive that none of it will survive long enough to get anywhere near the ground.

blackflame70006• 7 years ago

Yea it's Cesium 137 that everyone worries about and it comes from splitting uranium.

jhayward• 7 years ago

I have some bad news. We used to put tetraethyl lead in automobile fuel and then burn it in cities next to homes and schools.

saagarjha• 7 years ago

More bad news: we still put it in avgas.

dr_dshiv• 7 years ago

And when we took the lead away, crime dropped like 50% https://en.m.wikipedia.org/wiki/Lead%E2%80%93crime_hypothesi...

DuskStar5• 7 years ago

Same line of thinking that results in depleted uranium tank shells.

Yeah, since neither was particularly toxic, and both offered significant performance gains over the alternatives. (Uranium is extremely dense, self-sharpens on impact instead of mushrooming, and catches fire after penetration giving you an incendiary payload for free. Supposedly, nothing else comes close for tank rounds)

regularfry3• 7 years ago

Uranium is... not nice stuff. I wouldn't classify it as "not particularly toxic". https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2819790/

jabl6• 7 years ago

Several western countries use tungsten instead of DU. Apparently largely due to the political issues anything uranium brings.

jabl6• 7 years ago

Apparently back in the day they were seriously considering ClF5 as the next generation oxidizer for rocket propellants. Implying that the rocket exhaust would to a large extent consist of HF and HCl. Yikes!

mnw21cam• 7 years ago

ITYM ClF3 (Chlorine Trifluoride) which earned the now famous description "hypergolic with test engineers". https://blogs.sciencemag.org/pipeline/archives/2008/02/26/sa...

Equally funny is where someone thought that it would be a wonderful idea to burn mercaptans in a rocket, which wasn't quite as toxic, but caused the test site to become a no-go zone just from the unbearable stench.

leeoniya• 7 years ago

my favorite A-12 read:

https://www.otherhand.org/home-page/area-51-and-other-strang...

that whole site is full of awesome accounts of his adventures out west.

willvarfar3• 7 years ago

My favorite A12 talk:

https://www.youtube.com/watch?v=MGdxpqqsHl8

Frank Murray's talk is full of great facts, insight, yarns and stuff. Still as sharp as a tack.

There are lots of other interviews with A12 and SR71 and other interesting planes on youtube.

Be warned: an HNer could lose days browsing there ;)

exabrial• 7 years ago

Though there is no indication that A-50 used a radioactive cesium isotope, the compound is toxic and it's unclear how hazardous the complete mixture may have been

dschuetz2• 7 years ago

I think, adding anything radioactive to jetfuel even with decay halflifes of some days would leave a detectable trail.

nullc2• 7 years ago

My experience with cesium is that everyone thinks its radioactive. It isn't-- like many common elements there is a radioactive isotope, but that is not what would have been used here.

I speculate this worked by the highly reactive cesium ionizing the air. Similar things have been done with doping rocket fuels with metals to stimulate lightning strikes.

Presumably most of the cesium would end up reacted very quickly, I don't know what the products would be but plenty of obvious candidates like cesium carbonate appear to be non-toxic.

dschuetz2• 7 years ago

Well, you are correct in just some cases. Caesium has only one stable isotope, so beside the actual Caesium and Caesium-133 everything else has ß-decay. Unless you are burning 100% refined Caesium, there is always a chance that you are also burning its radioactive isotopes.

nullc2• 7 years ago

All the isotopes of Cs other than 133 exist only in negligible amounts in nature. So sure, perhaps there would be a trace amount of something else-- but that is true of anything.

ohiovr2• 7 years ago

Caesium is the easiest metal to ionize. It also has a fairly low work function. So it is easy to turn the metal into a plasma.

AleksReed• 7 years ago

)

ravroid• 7 years ago

You raise an excellent point.

jacobush4• 7 years ago

That though, was a mere footnote

manigandham• 7 years ago

There’s a fantastic recent special on the history channel about the Skunk Works, Kelly Johnson, and the development of the SR-71

Secrets in the Sky: The Untold Story of Skunk Works: https://www.history.com/specials/secrets-in-the-sky-the-unto...

kyoledemon17• 7 years ago

Great

ohiovr2• 7 years ago

Isn't caesium kind of hugely expensive?

mannykannot• 7 years ago

The original source of this additive (or the raw materials for it) was a waste product from detergent manufacture. When that method of detergent production was discontinued, they needed to set up an alternative source, which no doubt raised the cost, but everything about the A12 / SR71 was hugely expensive.

iflypropplanes• 7 years ago

For those in NYC, there is an A-12 on display on the deck of the Intrepid. 100% worth the visit

hsnewman• 7 years ago

I've heard chem trail conspiracy theories, it seems that there is a hint of truth in them, but still ridiculous. https://en.wikipedia.org/wiki/Chemtrail_conspiracy_theory

myth_drannon• 7 years ago

We need to give a proper credit to the Soviet physicist Petr Ufimtsev (https://en.wikipedia.org/wiki/Petr_Ufimtsev) who's published papers in 60's on reflection of electromagnetic waves were read by Lockheed Martin engineers and that started the stealth program.

dev_dull• 7 years ago

He gained permission to publish his research results internationally because they were considered to be of no significant military or economic value.

A decision I'm sure the Soviet Union would quickly come to regret.

jpmattia• 7 years ago

I would love to know the thinking behind this method.

Off the top of my head: They are adding Cesium ("screw the environment, I have to escape my pursuer") to the engine in order to leave a plasmonic plume. The plasma, which occurs because the electrons in Cesium are stripped off in the heat of the engine, absorbs microwaves (ie, radar) because of the expected cyclotron physics of a free-electron gas.

However as an electronic countermeasure, I do not see the point. The plasmonic plume will absorb the microwaves where the rest of the plane will continue to reflect it. To my thinking, the is exactly what you do not want to do: You've reduced the microwave signal where the plane is not present, and done nothing to the signal where the plane is present. So you've improved the signal-to-noise for the enemy, which are providing guidance for anti-aircraft missiles.

Considering how many years this program went on for, my thinking must be wrong. Maybe anti-aircraft missiles of the era did not intercept from oblique angles (which takes serious computation and sensors) but could only hit from behind (where the plume would attenuate a signal)?

AWildC182• 7 years ago

For these kinds of radars, there won't really be any signal against the sky and, lets be honest here, nothing is going to be looking at the SR-71 from a top down aspect. In a tail chase situation though, a missile would have to fly straight at the exhaust which would give the aircraft some cover.

There's a bit of reading between the lines that needs to be done here though. The aircraft is already shaped to deflect radar waves from a tail or nose on aspect but the part that's very hard to 'stealth' is the insides of the engines, especially from the rear aspect. Turbine blades and all the other geometry inside tends to act like a radar disco-ball and leaves even many modern aircraft vulnerable. By making the exhaust radar absorbent you fix this issue.

blakes• 7 years ago

Apparently in some aircraft, the radar cross section of the exhaust is easier to spot than the aircraft itself.

efrafa• 7 years ago

Not really related to the article, but this short speed story with SR-71 Pilot is so fun!

https://www.youtube.com/watch?v=ILop3Kn3JO8

The SR-71's predecessor used cesium-laced fuel to create radar-absorbing exhaust

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