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I was just watching The Right Stuff for the 100th time,and I've always wondered what is that hose spewing flame/burning propellant out of the bottom of the rocket. It's definitely not an engine,and why would the engineers have designed it that way. I have attached an image.atlas carrying John Glenn into orbit

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  • $\begingroup$ It's already been answered. Knowledge is power. Thank you for responding. Since John and All of The Merc 7 were with us for many years after the program ended,it's nice to know that what appears to be thrust, is in fact a device to keep the rocket motor from blowing up. $\endgroup$ – Ray G Feb 9 at 16:46
  • $\begingroup$ Naturally I lost the link, but somewhere SpaceX has posted a very detailed discussion of the evolution of engine design. $\endgroup$ – Carl Witthoft Feb 10 at 14:08
  • $\begingroup$ @CarlWitthoft if you should ever come across that again, I'd love to see it. But as Stephen J. Gould said about evolution (paraphrased) "It's not a ladder, it's a bush." $\endgroup$ – Organic Marble Feb 10 at 14:52
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    $\begingroup$ @OrganicMarble found it everydayastronaut.com/raptor-engine $\endgroup$ – Carl Witthoft Feb 10 at 16:52
  • $\begingroup$ @CarlWitthoft many thanks! $\endgroup$ – Organic Marble Feb 10 at 17:07
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It's the turbopump exhaust from the booster (jettisonable) engines.

enter image description here

From Spacecraft and Boosters by Gatland p. 222-224

Exhaust stack discharges fuel-rich efflux outside reverse aerodynamic flow at base of missile

In other words, the main purpose of the long duct is to get the fuel-rich turbopump exhaust away from the bottom of the vehicle to prevent it being trapped there by recirculation and potentially igniting.

The sustainer engine turbopump exhaust goes into its nozzle instead using an "aspirator", you can see that duct marked #41 on the schematic.

It looks like there were several variants of the design over the Atlas program. There's lots of good information on this page including this schematic

enter image description here

and this photograph.

enter image description here

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    $\begingroup$ Thank you so much. That has driven me crazy ever since I first saw the movie,documentaries,or any video footage of the Atlas in operation. For the extreme novice such as me that only knows the basics of rocketry,you would expect the thrust to be coming only from the engine bells and nowhere else. It's a comfort to know,as history confirmed,that it was not a malfunction. :) $\endgroup$ – Ray G Feb 9 at 16:34
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    $\begingroup$ Thank you very much Christopher James Huff. What I find most amazing is how little the average joe,(including myself) knows about the technology that allowed us to reach our country's ( the USA) to reach the moon in 68. It tells me that it's time to hit the books. $\endgroup$ – Ray G Feb 10 at 0:11
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    $\begingroup$ @RayG and now you'll always notice the turbine exhaust for the fuel pumps in every rocket launch.... $\endgroup$ – Criggie Feb 10 at 1:21
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    $\begingroup$ @RayG engine bells/thrust nozzles with Special Fins inside to keep the exhaust from producing vortices that could allow the engine to explode Do you mean the baffles on the injector plate? $\endgroup$ – zovits Feb 10 at 11:12
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    $\begingroup$ well, @Criggie, those that don't use closed cycle engines, and those that don't use the exhaust for film cooling. $\endgroup$ – JCRM Feb 11 at 11:16

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