# Stealth-bombers and contrails

**URL:** <https://boards.straightdope.com/t/stealth-bombers-and-contrails/333237>\
**Category:** Factual Questions\
**Created:** [November 29, 2005, 6:01pm UTC](https://boards.straightdope.com/t/stealth-bombers-and-contrails/333237 "2005-11-29T18:01:00Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Dead\_Battery](https://avatars.discourse-cdn.com/v4/letter/d/b38774/32.png) [@Dead\_Battery](https://boards.straightdope.com/u/Dead_Battery)\
**Post date:** [November 29, 2005, 6:01pm UTC](https://boards.straightdope.com/t/stealth-bombers-and-contrails/333237/1 "2005-11-29T18:01:00Z")

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I saw a couple of fighter-jets of some kind flying way high the other day, could barely hear them, but the contrails were a dead giveaway (that was how I noticed them in the first place), and I got to wondering: do stealth-bombers have some system or device to prevent contrails being formed?

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**Author:** ![thinksnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thinksnow/32/2849_2.png) [@thinksnow](https://boards.straightdope.com/u/thinksnow)\
**Post date:** [November 29, 2005, 6:22pm UTC](https://boards.straightdope.com/t/stealth-bombers-and-contrails/333237/2 "2005-11-29T18:22:22Z")

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> [@Dead Battery](#):
>
> I saw a couple of fighter-jets of some kind flying way high the other day, could barely hear them, but the contrails were a dead giveaway (that was how I noticed them in the first place), and I got to wondering: do stealth-bombers have some system or device to prevent contrails being formed?

[Yes](http://www.vectorsite.net/avb2.html):

> [@](#):
>
> The exhaust is mixed with airflow obtained through the boundary layer splitter slot to reduce the infrared signature. The aircraft was also designed to eliminate its contrail, with a tank outboard of the main landing gear to store a chemical that would be mixed with the exhaust flow to suppressed the formation of a contrail. This scheme wasn’t actually used in practice, with a “lidar” (laser radar) system instead eventually developed to detect the formation of a contrail and alert the pilot to descend to lower altitude.

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**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\
**Post date:** [November 29, 2005, 6:54pm UTC](https://boards.straightdope.com/t/stealth-bombers-and-contrails/333237/3 "2005-11-29T18:54:20Z")

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Also, it turns out that contrails aren’t a serious problem for stealth planes.

Contrails can’t be seen until the plane is close; by then it’s too late to keep the stealth plane away from your critical airfield, factory, whatever. And probably too late to scramble your defensive fighter planes, also.

Contrails are visible to human eyes, but not to the radars of anti-aircraft guns or missiles. The ‘stealth’ is their near-invisibility to these radars. No doubt an aiming system could be built using video scanning for contrails, given enough time & money. But it would be subject to the same limit as above: it would only ‘see’ the enemy planes contrails when the plane was already overhead – too late.

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**Author:** ![butler1850](https://avatars.discourse-cdn.com/v4/letter/b/779978/32.png) [@butler1850](https://boards.straightdope.com/u/butler1850)\
**Post date:** [November 29, 2005, 6:57pm UTC](https://boards.straightdope.com/t/stealth-bombers-and-contrails/333237/4 "2005-11-29T18:57:43Z")

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In addition to all of the great information above, ‘stealth’ aircraft also generally fly at night, so barring considerable light from the moon, these contrails (if produced) would be less visable under normal operational conditions.