Apollo Discussions > The Reality of Apollo
Back-up plan for Apollo
Glom:
--- Quote from: ka9q on April 07, 2012, 08:16:25 PM ---
--- Quote from: Donnie B. on April 07, 2012, 06:37:22 PM ---It's a wild thought, though -- imagine a manned liftoff from one pad while the big Saturn was already sitting on a nearby pad, all set to go (or vice versa). Shades of (dare I say it) Armageddon!
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Or Skylab...?
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Thank you. And Skylab had the sense to not put the two space vehicles right next to each other.
Bob B.:
--- Quote from: ka9q on April 07, 2012, 08:13:17 PM ---In reality the earth's density is not uniform; it has liquid and solid iron cores that are even denser than iron on the surface because they're under extreme compression. So gravity actually reaches a peak at the surface of the outer core of 10.62 m/s^2 (about 1.08g) before dropping to zero at the center. But this still wouldn't give the dramatic effect of my black hole at the center.
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Where did you find that 10.62 m/s2 number? A couple years ago I modelled Earth's interior to estimate gravity versus depth and I arrived at a number very close to that right at the surface of the outer iron core. I didn't expect such a result when I started, so it's good to see data that appears to confirm my numbers.
Here's the original thread in which this was discussed:
http://apollohoax.proboards.com/index.cgi?board=theories&action=display&thread=2964&page=3
ka9q:
--- Quote from: Bob B. on April 09, 2012, 02:26:20 PM ---Where did you find that 10.62 m/s2 number?
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Via Google, of course. I didn't hang onto the link, so if you published it on the web, your result might have been the one that I found. So don't use it as confirmation. :-)
I do remember the person did a fairly straightforward if brute-force numerical integration, working through the earth as a series of concentric shells, each shell having a uniform composition that changed with depth. I had remembered seeing something like this result a while ago, but I wasn't sure of the actual acceleration value.
ka9q:
--- Quote from: Donnie B. on April 07, 2012, 06:23:04 PM ---The ICU still managed to get the S-IVB into orbit... in a most unconventional manner. It was actually thrusting backwards at engine cutoff.
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Are you sure about that? It's hard for me to conceive of a reason why the IU would flip the stack around. That would only happen if there had been an overspeed, but this was an underspeed.
I do remember reading that in the LM guidance equations it was possible for the LM to invert during descent if one of the phases (probably the braking phase) had been carried too far, because it was targeted for a specific point in space and normally switched to the next program (probably the approach phase) before actually reaching it. Remember, computers (like many humans) lack any notion of common sense.
Donnie B.:
--- Quote from: ka9q on April 11, 2012, 07:28:07 AM ---
--- Quote from: Donnie B. on April 07, 2012, 06:23:04 PM ---The ICU still managed to get the S-IVB into orbit... in a most unconventional manner. It was actually thrusting backwards at engine cutoff.
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Are you sure about that? It's hard for me to conceive of a reason why the IU would flip the stack around. That would only happen if there had been an overspeed, but this was an underspeed.
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You made me go and look it up!
This is regarding Apollo 6, the second all-up unmanned test of a Saturn V. The quote is taken from Apollo: The Race To the Moon by Murray and Cox, one of my favorite references -- it's more focused on the flight controller side of things than the astronauts', and has an excellent chapter on A13 (among many other things).
--- Quote ---After the two [S-II] engines had gone out, the vehicle had maintained a pitched-up attitude known as "chi-freeze" for far longer than it would have under ordinary circumstances. "Well, the S-IVB lit up," [FIDO Jay] Greene recalled, "and the first thing it said was, 'Omigod, I've got too much altitude.' And so it pointed its nose straight at the center of the earth." This battle between the guidance system and the gimbal limits on the engine continued for about eighty seconds, with Greene getting closer and closer to calling an abort of his own. When the S-IVB finally gave up trying to get to the altitude it wanted, it had a flight-path angle that was unacceptably low. "So then the little devil said, 'Well, this is bad, I've got to pick up the flight-path angle,' so it started pitching up, and as it started pitching up it said, 'Now I'm overspeed,' so it actually went into orbit thrusting backward."
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Nothing like a little IU anthropomorphizing to brighten a FIDO's day.
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