Author Topic: What degree of manual control did the Apollo astronauts have prior to TLI?  (Read 2877 times)

Offline JayUtah

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Re: What degree of manual control did the Apollo astronauts have prior to TLI?
« Reply #30 on: January 31, 2017, 12:04:57 PM »
I seem to remember reading somewhere that the flow of air between the Orbiter and the ET turned out to be more dangerous than designers had expected, and this alone might have caused the destruction of Columbia in the first Shuttle mission.

Is this true or am I mistaken?

There were a few overpressure instances that were not expected, so that part is true.  Whether any of the post-flight anomalies attributed to the overpressure, including loss of TPS tiles, would have had catastrophic consequences if they had been more severe is anyone's guess.

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With only a lay knowledge of aerodynamics I get the impression that some of the air passing off the nose of the ET would funnel between the Orbiter and ET, and in the process get compressed as the space narrowed...

Yes.  There's an overpressure hotspot on the ET just forward of the bipod.  This corresponds to the contour of the orbiter's forward underside.  It's actually worse between the SRB nosecones and the ET, and those zones sort of blend together.

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...and on top of that be disrupted by the struts and pipes connecting the two

The LOX feedline really doesn't really affect the flow much, which is a bit counterintuitive.  There are some local discontinuities.  But the bipod itself wreaks havoc.  The overpressure doesn't extend farther aft on the ET than the bipod, which tells me there's a fair amount of turbulent flow aft of the bipod, and I'd attribute it to the bipod's effect on the flow.  I think that has implications more for STS-107 than for STS-1.
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Online Geordie

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I'm aware that the Apollo astronauts, on trans-lunar coast, used the 'optics' (sextant) to determine position, compute course, and then apply correction.

To what extent did they have manual control prior to this? Was there any element of them actually 'steering' the craft at any point from launch to TLI?

Quote from: Woods, W. David.

LIFT-OFF [...]
 
  At the center of the abort decision was the commander[....] If two cues from the EDS called for an abort[...she would] twist the handle in her left hand counterclockwise, activating the appropriate sequence to leave a malfunctioning launch vehicle behind[....]

  The EDS was responsible for lighting a cluster of indicators that showed whether each engine was running at full thrust, whether the rocket was veering too fast and whether the Saturn's guidance system still knew which way was up. In the latter case, from Apollo 11 onwards, if the commander saw that the Saturn was incapable of guiding itself, she had the option of twisting the T-handle clockwise to pass control of the entire rocket to the spacecraft, and if that was also failing, she could manually guide it to orbit[....]

  The Saturn V took care of its own guidance and [...]the crew had little to do except to keep a careful watch over it. This they did by running Program 11 on their computer, which displayed their speed, height and how rapidly that height was changing. P11 also drove their displays to show what their attitude should be throughout the ascent, so that any deviation could be seen. Should the commander have to take over control of the Saturn, she would fly it by following the the cues given by P11.

  [...] The decision to control the Saturn V from its own instrument unit instead of using the capabilities of the command module's guidance system [...] was dramatically shown to be a fortuitous decision when the Apollo 12 was struck by lightning only 36 seconds after [lift-off....]

  Later in the mission Dick Gordon laughed about the experience. "The launch was almost as good as me getting to fly the Saturn V into orbit." His was only the second Saturn equipped to allow the commander to fly manually into orbit - a contingency that, while never called upon, would have been welcomed by the hot-shot commanders within the astronaut corps.

  Woods, W. David. How Apollo Flew to the Moon  pp. 70-73.



  All of this is in the book prior to the section entitled "SECOND STAGE".

.           She's on fire\  And she burns through the night at the speed of light\
             She's on fire\  With the heat of the beat right beneath her feet\
              She's on fire\  And the name of the game is to fuel her flame\
               She's on fire, fire, fire, fire, fire!

Online Geordie

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  All of this is in the book prior to the section titled "SECOND STAGE".
  In fact, it's all contained in the sub-section titled "Abort mode one-alpha".
Quote from: Woods, W. David
  The first 42 seconds of the flight up to a height of about 3 kilometres was flown in abort mode one-alpha[....]
Later in the mission Dick Gordon laughed about the experience.
  Oops, I put Dick Gordon, the Apollo 12 CMP, rather than Pete Conrad, the commander.

  Here's a link to the book's website: How Apollo Flew to the Moon
« Last Edit: May 07, 2017, 12:41:59 PM by Geordie »
.           She's on fire\  And she burns through the night at the speed of light\
             She's on fire\  With the heat of the beat right beneath her feet\
              She's on fire\  And the name of the game is to fuel her flame\
               She's on fire, fire, fire, fire, fire!

Offline Everett

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Sooo, if my take on this thread is correct...

In the event of Saturn V launch to orbit guidance system failure, it 'could' be flown manually, and this would consist of essentially "follow the pointer" on the ADI (is it still called that on rockets?), and keeping the line painted on the ball indicating attitude aligned under the needle indicating desired attitude, with inputs filtered to keep roll/pitch/yaw rates low, using the CSM's guidance system?

And in the event of an outboard F-1 failure, the stack would break up before the abort system could fire? Which of course would still trigger the LES tower, and the capsule would be pulled clear, even if not quite in the original direction?

(I recall reading a study done to determine that in the event of a high altitude stack breakup, the CM would aerodynamically assume either "bottom down, parachutes up" or "bottom up, parachutes down, impact ground" position. And the pilot would have maybe 20-40?? (It was a long time ago) seconds to orient it correctly. It was difficult to use outside references to do so, but they did discover a different method they relied on the capsule's response to control inputs when it first entered the atmosphere, and having something like a 15-20 second period where that could be used and the CM RCS was still powerful enough and the air thin enough to flip the orientation if it was the wrong one. Likely the main downside of the CM compared to the Soyuz capsule - Soyuz was aerodynamically self-righting, including on reentry. IIRC, it 'also' had to be, as it had no RCS in the capsule proper.)

Offline ka9q

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Yes, I believe your take on manual control of the Saturn V is pretty much correct. A lot still has to work for this to be possible, however. The CSM's guidance and control system and its communication links with the Saturn have to be fully functional, the rates have to be low enough (before atmospheric exit) that the emergency detection system hasn't already commanded an abort, and most importantly the Saturn's engines have to be functional. Given the redundancy in the Saturn's IU, a failure in an engine gimbal (like the dreaded "hardover") seems much more likely than a guidance failure that leaves the whole stack in a state where it can still be manually steered successfully into orbit.
« Last Edit: June 02, 2017, 03:25:53 AM by ka9q »

Offline ka9q

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That's an interesting question of properly orienting the CM after an abort. Remember there were numerous abort "modes" for each phase of flight (you hear the Capcom calling them off to the commander as they step through them). Assuming you're talking about an abort on first stage flight around max-Q, the most dangerous time,  my understanding is that the LES was expected to reorient the CM after pulling it free from the rest of the stack. Depending on air density it could use either the canards and/or the CM's RCS. It's also possible that deploying the drogue chutes would reorient the CM if it were falling nose first; they seem to be a popular way to stabilize the attitude of a  falling object that's still too high and too fast for main chutes to be used.