The Life-Saving Q-Ball of Apollo

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XolveJohn

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Strange. Airspeed guidance? They had a bunch of gyros in one of the adapter rings for course feed back.

Why did they need this unconventional sensor? I have NEVER heard of ANY rocket being guided this way.

I can see for an abort, but a good old inertial platform is the traditional means, still used today.
 

burkefj

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I believe that's the same thing or similar to the X-15 nose sensor to measure angle of attack and angle of sideslip.
 
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Sooner Boomer

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I seem to recall that "q" is not simply aerodynamic (or atmospheric) pressure, but rather the pressure differential.
 

georgegassaway

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I could not get the "comments" area to display, a problem I've had with Youtube for the last week or so (shows a list of other videos below it rather than on the right side).

Anyway, went to her website and entered a comment there to let her know the LES had one big 26" solid motor with four angled nozzles. Not four individual motors. Included links to two drawings.

I'm impressed at how much she does get right, posting so often with such a wide range of infromation.
As there's SO much detail to learn that is hard for most other than people who mainly research just one or two rocket types over years, or plain were exposed to if they were alive during Apollo and devoured everything available at the time (I remembered seeing video if the Q-Ball cover popping off before ignition). As opposed to a younger person trying to learn SO much about everything across the board.
 
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burkefj

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Yeah, the video of the qball cover coming off was neat I've never seen that before, and did not know there was a qball in the escape tower.
 
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I believe that's the same thing or similar to the X-15 nose sensor to measure angle of attack and angle of sideslip.
I believe that the Q Ball on the X-15 served as the prototype and proof of concept for its use on the Saturn, if I am remembering it correctly. But the X-15 did use the Q Ball. Early flights didn't use it because it was not ready yet. There is a pretty famous photo out there of one of the trial units sitting on a tripod just a few feet behind a F-100 in full afterburner, with the Q Ball glowing bright orange.

Found it!
 
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OverTheTop

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I seem to recall that "q" is not simply aerodynamic (or atmospheric) pressure, but rather the pressure differential.
q is actually the dynamic pressure. The pressure related to the object moving through the fluid (air in this case). q = half rho velocity^2 (rho is the air density)

A pitot static tube actually takes this dynamic pressure from the tip (which also includes a static pressure from the surrounding air added to it) and subtracts the static pressure, from a port at 90deg to the airflow (no dynamic, therefore only static) to get just the dynamic pressure. Pitot tubes lose their accuracy as they go away from directly facing the airflow.

In the case of the X-15 the nose ball swiveled (servo controlled) to have the nose port always directly facing the airstream (directly behind the stagnation point), regardless of AoA or sideslip of the rest of the craft. Can't remember where the static ports were for this, but I think they were back on the airframe somewhere IIRC.

[edit]: Found a nice little pdf on it here: https://www.nasa.gov/centers/dryden/pdf/87711main_H-374.pdf
 
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Steven

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So all I need to do is stick a Q-Tip on my LES and I'm set.
 
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