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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 internall

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 7y 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 7y ago
  Yep! It's called TEB (Triethylborane). More info here: https://en.wikipedia.org/wiki/Triethylborane 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.
  - jazzyjackson 7y ago
    I don’t know anything about afterburners, if it’s the same fuel as the usual engine, what about it needs to be lit with a lower temperature fuel? I always assumed afterburners just meant opening the throttle up but there must be more to it
    - jabl 7y ago
      > I always assumed afterburners just meant opening the throttle up but there must be more to it No, as the name implies it's literally pouring in fuel after the turbine, in the exhaust. The exhaust is hot, yes, but cooler than the combustion chambers (which reside in between the turbine and compressor). So if you have some special fuel that's very hard to ignite then maybe you need some help to get the afterburning started.
coolspot 7y ago
Most military helicopters having some ways of masking IR signature: https://www.sciencedirect.com/science/article/pii/S1000936114000168 https://www.sciencedirect.com/science/article/pii/S100093611...
- austinheap 7y ago
  1960s designs cannot be masked against modern FLIR arrays so old rotorcraft still in service are just retrofitted to discourage detection.
- decoyworker 7y ago
  https://en.wikipedia.org/wiki/Common_Infrared_Countermeasures_program 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.
blackflame7000 7y ago
It depends. If its regular Cesium 133 then it's harmless compared to Cesium 137.
taneq 7y 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.
- DuskStar 7y 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 https://en.wikipedia.org/wiki/Future_Vertical_Lift
- Daniel_sk 7y 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.
  - snowwrestler 7y ago
    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 7y ago
      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.
tempguy9999 7y 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.
- pineconeInMyAss 7y ago
  >engineer: hey wouldn't it be cool if ... >tempguy9999: https://www.youtube.com/watch?v=WWaLxFIVX1s https://www.youtube.com/watch?v=WWaLxFIVX1s thank you for your service, noble internet warrior!
- jacobush 7y ago
  You comment is toxic but from a technical aspect, really cool. I choose to overlook it.
  - tempguy9999 7y ago
    Your comment went so far over my head I knew none of it, only the faintest settling of toxic caesium particulates in my lungs gave me any clue it was ever there.
cafebabbe 7y ago
"I know it's toxic but from a technical aspect, that is really cool" is a great alternative HN tagline

vvanders 7y 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 7y ago
Yep! It's called TEB (Triethylborane). More info here: https://en.wikipedia.org/wiki/Triethylborane 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.
- jazzyjackson 7y ago
  I don’t know anything about afterburners, if it’s the same fuel as the usual engine, what about it needs to be lit with a lower temperature fuel? I always assumed afterburners just meant opening the throttle up but there must be more to it
  - jabl 7y ago
    > I always assumed afterburners just meant opening the throttle up but there must be more to it No, as the name implies it's literally pouring in fuel after the turbine, in the exhaust. The exhaust is hot, yes, but cooler than the combustion chambers (which reside in between the turbine and compressor). So if you have some special fuel that's very hard to ignite then maybe you need some help to get the afterburning started.

coolspot 7y ago

Most military helicopters having some ways of masking IR signature: https://www.sciencedirect.com/science/article/pii/S1000936114000168 https://www.sciencedirect.com/science/article/pii/S100093611...

austinheap 7y ago
1960s designs cannot be masked against modern FLIR arrays so old rotorcraft still in service are just retrofitted to discourage detection.
decoyworker 7y ago
https://en.wikipedia.org/wiki/Common_Infrared_Countermeasures_program 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.

blackflame7000 7y ago

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

taneq 7y 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.

DuskStar 7y 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 https://en.wikipedia.org/wiki/Future_Vertical_Lift
Daniel_sk 7y 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.
- snowwrestler 7y ago
  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 7y ago
    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.

tempguy9999 7y 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.

pineconeInMyAss 7y ago
>engineer: hey wouldn't it be cool if ... >tempguy9999: https://www.youtube.com/watch?v=WWaLxFIVX1s https://www.youtube.com/watch?v=WWaLxFIVX1s thank you for your service, noble internet warrior!
jacobush 7y ago
You comment is toxic but from a technical aspect, really cool. I choose to overlook it.
- tempguy9999 7y ago
  Your comment went so far over my head I knew none of it, only the faintest settling of toxic caesium particulates in my lungs gave me any clue it was ever there.

cafebabbe 7y ago

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