
The SR-71's predecessor used cesium-laced fuel to create radar-absorbing exhaust - ivanech
https://www.thedrive.com/the-war-zone/29787/the-sr-71-blackbirds-predecessor-created-plasma-stealth-by-burning-cesium-laced-fuel
======
tlb
> 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.

~~~
taneq
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".

~~~
faizshah
Some cool ones here:
[https://www.computerhistory.org/collections/fairchild/](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.

~~~
_jal
Along the same lines, my bedside-book for the last few months has been
Engineering and Operations in the Bell System[1].

It is... from another time. Both the quality of the engineering and the
quality of the documentation simply don't happen anymore outside of very
narrow niches.

And then you look at the Death Star now, and their core competency is
lobbying. Priorities certainly have changed.

[1] [https://www.worldcat.org/title/engineering-and-operations-
in...](https://www.worldcat.org/title/engineering-and-operations-in-the-bell-
system/oclc/11756737)

~~~
exikyut
Engineering_and_Operations_in_the_Bell_System_2ed_1984.pdf (47MB):
[http://bitsavers.trailing-
edge.com/communications/westernEle...](http://bitsavers.trailing-
edge.com/communications/westernElectric/books/Engineering_and_Operations_in_the_Bell_System_2ed_1984.pdf)

Also at (previews faster):
[https://archive.org/details/bitsavers_westernEleEngineeringa...](https://archive.org/details/bitsavers_westernEleEngineeringandOperationsintheBellSystem2_49741719)

~~~
faizshah
Great find! Found some new bed time reading :D

------
skunkworker
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.

~~~
galangalalgol
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
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-...](https://en.wikipedia.org/wiki/Northrop_YF-23#/media/File:YF-23_top_view.jpg)

~~~
mgarfias
Funny, the way i remember it happening: both YF-22s were lost do to mishaps,
the YF-23 was faster, stealthier, and just as maneuverable without the
vectored thrust. The AF wanted the -23, but the chairman of the senate armed
services committee was from Georgia, where Lockheed promised to build the -22.
and the history got rewritten.

Source: Dad was part of the YF-23 program at northrop and lost his gog when
the project was shitcanned. yes, still bitter almost 30 years later.

~~~
close04
> the way i remember it happening: both YF-22s were lost do to mishaps

Seems they're museums pieces now and look relatively unscathed. [0][1]

> The two YF-23 prototypes were museum exhibits as of 2010

[0]
[https://en.wikipedia.org/wiki/Northrop_YF-23#/media/File:YF-...](https://en.wikipedia.org/wiki/Northrop_YF-23#/media/File:YF-23_PAV-2_%22Spider%22_Static.jpg)

[1]
[https://en.wikipedia.org/wiki/Northrop_YF-23#/media/File:YF-...](https://en.wikipedia.org/wiki/Northrop_YF-23#/media/File:YF-23_in_the_restoration_area_of_the_usaf_museum.jpg)

~~~
dkersten
> both YF-22s were lost

> The two YF-23 prototypes were museum exhibits

The 22's were lost, the 23's were museum exhibits, not the same planes.

~~~
close04
My bad, my brain read it as “the 23s were lost”. Sleep deprivation at its
best.

------
nullc
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.

~~~
dschuetz
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.

~~~
nullc
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.

------
jpmattia
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
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.

------
syntaxing
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.

~~~
taneq
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.

~~~
Daniel_sk
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.

~~~
snowwrestler
My recollection is that the contemporary reporting was pretty specific about
what it was: an existing chopper with stealth tech grafted on. Something about
that (the weight or shape) reduced lift and led to a crash landing during the
mission.

Some Google around NYTimes would probably turn up the details.

~~~
showerst
The story I heard at the time was that it was a combination of the stealth
helicopters having lousy low-hover performance, and that during training
they'd mocked a nearby solid wall up with a chain-link fence, which led to
picking a poor landing zone.

------
myth_drannon
We need to give a proper credit to the Soviet physicist Petr Ufimtsev
([https://en.wikipedia.org/wiki/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
> _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.

------
liability
That's one hell of a "chemtrail"!

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

------
robohoe
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/...](https://www.amazon.com/Area-51-Uncensored-Americas-
Military/dp/0316202304/ref=sr_1_fkmr1_1?keywords=Area+51+Amy+jacobson&qid=1568341816&s=gateway&sr=8-1-fkmr1)

------
exabrial
> 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

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

------
manigandham
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...](https://www.history.com/specials/secrets-in-the-sky-the-untold-story-
of-skunk-works)

------
leeoniya
my favorite A-12 read:

[https://www.otherhand.org/home-page/area-51-and-other-
strang...](https://www.otherhand.org/home-page/area-51-and-other-strange-
places/bluefire-main/bluefire/the-hunt-for-928/)

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

~~~
willvarfar
My favorite A12 talk:

[https://www.youtube.com/watch?v=MGdxpqqsHl8](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 ;)

------
hsnewman
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](https://en.wikipedia.org/wiki/Chemtrail_conspiracy_theory)

------
ohiovr
Isn't caesium kind of hugely expensive?

~~~
mannykannot
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.

------
AleksReed
)

~~~
ravroid
You raise an excellent point.

~~~
jacobush
That though, was a mere footnote

------
kyoledemon17
Great

------
efrafa
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](https://www.youtube.com/watch?v=ILop3Kn3JO8)

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

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

~~~
DuskStar
> 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)

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

~~~
astine
True, but the alternative is tungsten, which is not much better in terms of
toxicity:

[https://www.atsdr.cdc.gov/toxprofiles/tp186.pdf](https://www.atsdr.cdc.gov/toxprofiles/tp186.pdf)

The problem here is that armor piercing rounds need to be made of heavy metals
in order to work and heavy metals are generally toxic. Even lead, which old
fashioned bullets and shells are made of is toxic.

~~~
regularfry
Uranium is more likely to distribute that toxicity in a convenient dust cloud,
though. Tungsten and lead for the most part stay in one piece on impact.

