Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

thedrive.com

Post reply on HN
Print view View original

31–40 of 160 posts

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

#31

Post by taneq »

tlb wrote: post #7

> 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.…

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".

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

#32

Post by taneq »

VonGuard wrote: post #29
tlb wrote: post #7

> 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.…

I have visions of exploding journalists.... For Reference: https://www.youtube.com/watch?v=m55kgyApYrY

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

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

#33

Post by mNovak »

tlb wrote: post #7

> 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.…

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.

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

#34

Post by CamperBob2 »

taneq wrote: post #31
tlb wrote: post #7

> 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.…

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".

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

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

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

#35

Post by taneq »

syntaxing wrote: post #5

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.

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.

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

#36

Post by ridgeguy »

tlb wrote: post #7

> 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.…

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)

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

#37

Post by saagarjha »

jhayward wrote: post #30
treggle wrote: post #11

Of course, because nothing matters more than getting the advantage. Same line of thinking that results in depleted uranium tank shells.

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.

More bad news: we still put it in avgas.

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

#39

Post by nabla9 »

mNovak wrote: post #33
tlb wrote: post #7

> 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.…

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.

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

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

#40

Post by DuskStar »

taneq wrote: post #35
syntaxing wrote: post #5

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.

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.

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

Post reply on HN