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Post by ka9q on Jul 30, 2010 19:04:01 GMT -4
One of the reasons I've gotten interested in the Apollo "hoax" is that I'm fascinated with the people who promote it. Why do they do it? I'm an engineer, not a psychiatrist or psychologist so my theories along these lines are purely the speculations of an amateur.
But I do think I've picked up some insights. And one of them is that the conspiracy theorist doesn't ask questions because of an honest interest in the answers. To them, questions are weapons.
Automatic weapons, that is. They rarely (if ever) like the answers so they'll ask them over and over, hoping that either the answer will change or the other party will eventually get tired of the whole affair and storm off.
If the answer changes, they can edit it into a video that proclaims that so-and-so can't keep his answers straight. And if the target simply gets tired, the CT will edit that into a video that claims "See! He refuses to answer the question. He obviously has something to hide!"
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Post by ka9q on Jul 30, 2010 14:07:46 GMT -4
I'd love a chance to see that exhibition again. Well, check out the Apollo Lunar Surface Journal! It doesn't have every Apollo photo in high resolution, but it has many of them. And quite a few have been joined into panoramas. You will need a big display (and some 3D glasses) to get the most from them, but they will knock your socks off. I never really had an idea of what it must be like to stand on the moon before I saw these more recent digital scans. Stare at them for a while and you just might start to feel like you're there.
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Post by ka9q on Jul 29, 2010 21:47:55 GMT -4
If the SPS had failed, wouldn't they have enough delta-V in the SM RCS to deorbit?
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Post by ka9q on Jul 29, 2010 17:25:10 GMT -4
I suppose you could have the lo res beam back for immediate look see and store the full res on whatever media on the moon and bring it back or beam back up of the hi res stuff during rest periods. Yes, that's exactly what I had in mind. The Apollo Unified S-Band System was an analog system, with separate subcarriers (channels) for voice, telemetry, etc. Today's version would be a single high speed digital link carrying an Internet Protocol packet stream. Priorities would be assigned to each application so that link bandwidth would never go to waste if there's something waiting to be sent.
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Post by ka9q on Jul 29, 2010 3:58:53 GMT -4
Well, yes, though generally when people refer to "digital camera" without qualification, they mean a still camera. Though have you seen the films taken with the 16mm DAC movie camera? They are quite spectacular. I had both in mind. At the risk of reopening the film-vs-digital debate, my personal take is that film is often overrated. It's not just a matter of resolution; film has other artifacts (surface defects, grain, etc) that digital sensors generally don't have. It's also easy to forget one of digital's big practical advantages: the ability of the photographer to check the results right after taking the picture, while there's still an opportunity to reshoot if necessary. But the real advantage of going back to the moon with digital still cameras would be that with the right linkup WE could see those still pictures in near real time. As stunning as much of the Apollo 70mm photography is, until only a few years ago I'd only seen a small sampling, and that only after generations of duping and printing. Only when the new digital scans started to appear, 30+ years after the fact, did I get to see most of those pictures, and close to their original quality.
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Post by ka9q on Jul 28, 2010 15:56:28 GMT -4
I think I found the information you were looking for. On page 5-4 of that report, the upper right plot in Figure 5-3 shows stage flow rate vs time, and the upper left graph shows thrust vs time. Thrust rises from about 34.7 MN to 40 MN at inboard cutoff, and flow rate increases from 13,200 kg/s to 13,420 kg/s or thereabouts at inboard cutoff, by eye from the plots. The plots also give mixture ratio and Isp as a function of time during S-IC flight.
The whole report is full of stuff like that. You really need it for your analysis.
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Post by ka9q on Jul 28, 2010 15:46:14 GMT -4
The reports you're looking for are titled, e.g., Saturn V Launch Vehicle Flight Evaluation Report - AS-506 - Apollo 11 Mission, and come out of Marshall SFC. The report number for that particular report is NASA TM X-62558.
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Post by ka9q on Jul 28, 2010 15:13:17 GMT -4
Who knows the cause of Irwin's heart problems? Remember he and Scott both had cardiac arrhythmias after a very long day that had them do an EVA and an ascent. The apparent cause, besides over-exertion, was dehydration that led to hypokalemia (low potassium levels). That was the reason for the potassium-fortified orange drinks on the Apollo 16 mission that led to John Young's famous open-mike complaints...
Gene Kranz talks about this incident in "Failure Is Not An Option". He said he had chills listening to the A/G circuit because the crew seemed so dangerously out of sync with what was going on. He also learned that the flight surgeons had noticed the EKG irregularities but didn't report them right away to the flight director out of misguided concerns about medical privacy. I could only agree strongly with Kranz.
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Post by ka9q on Jul 28, 2010 15:01:54 GMT -4
I'm not sure they would do much better, those Hasselblads took good pictures. A more spectacular question is going back to Hadley with modern climbing gear.Well...maybe. A digital HDTV camera would certainly be a marked improvement over the analog sequential color camera on the rover. And yeah, some safe way to descend into the Rille would be really neat. I have stared at pictures of the Rille trying to get a sense of scale, but it's nearly impossible. Seeing the astronauts as small dots at the bottom from a camera on the rim would help drive that scale home. My other favorite Apollo pictures include the long shots from Apollo 17 showing the LM sitting on the plain a long distance away. Made me appreciate just how much confidence they had developed in their EMUs (suits & PLSS & OPS). I know they had the buddy hose to share cooling water. And I think Gene Cernan pointed out that the guy with the failed PLSS would have two OPS if necessary, not just one, but still...the thought of racing back to the LM over that distance is the stuff of nightmares.
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Post by ka9q on Jul 28, 2010 14:52:12 GMT -4
I first took a snapshot of a simulated descent stage (quite well detailed 3D model) sitting on the lunar surface at Tranquility Base (exact coordinates, with simulated landmarks as well). Very nice work! One question - did you account for the angle at which the LMs sat on the surface? They were usually a few degrees off level, and the actual figures are given in the mission reports. I don't know if this will make much difference in the resulting shadows, but it just might at the lower sun elevations.
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Post by ka9q on Jul 28, 2010 14:43:59 GMT -4
I've looked at that picture too. My initial inclination was to see if it could be some sort of reflection or optical illusion, but the bell has a dark, nonreflective surface.
I put a lot of weight on the cosmonauts' report. Eyes that were actually there are a lot more reliable than a single photograph taken at a single instant. I do wish they'd said something at the time, because there was no way of knowing if it would have affected the operation of the SPS.
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Post by ka9q on Jul 28, 2010 14:40:10 GMT -4
Supposedly Amazon will ship my copy "real soon now", but it's been that way for a long time. I was getting really tired of having to tell Amazon "Yes, keep the order open" over and over.
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Post by ka9q on Jul 28, 2010 14:38:04 GMT -4
Yes, I believe you're right about pumps but we don't know the details of the F-1 turbopumps.
As I recall, the Saturn V flight reports discuss things like pump speed and inlet and outlet pressures. It might be worth scanning them for ideas. You have copies, right? They're separate from the mission reports.
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Post by ka9q on Jul 27, 2010 18:33:48 GMT -4
After shelving the project for several months, I finally got around to finishing my Saturn V launch simulation. Very nice work, Bob! You wonder why the propellant flow rate increased during the S-IC and S-II flights, and speculate that it was caused by the increase in longitudinal acceleration increasing the pump inlet pressures. I think this is almost certainly the case. The trouble both stages had with pogo lends further weight to this theory - pogo happens when the propellant flow rate (and thrust) increases with acceleration even when you don't want it to. The "fix" for pogo on the S-IC involved adding a helium pressurized "accumulator" to the propellant line. This would have dampened out rapid changes in inlet pressure due to the inertia of the propellant in the lines, but I don't think it would have changed the average flow rate vs acceleration. So the effect would still be there. As I recall, pogo on the S-II was never really solved; it was simply avoided by shutting down the inboard engine early (yet it still happened on Apollo 13). By limiting peak acceleration as the stage lost mass, that would have reduced the magnitude of the effect on thrust. But it would still be there. Maybe it's worth comparing the pump inlet pressures to the pressures maintained in the tank ullages vs the pressure due to the (accelerated) weights of the propellants. Remember that the head of propellant in each tank decreases as it empties.
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Post by ka9q on Jul 27, 2010 18:03:26 GMT -4
Good points about extremely low density of LH2, the fuel for the J-2s on the S-II and S-IVB. And you're right that not every upper stage burns LH2. A rich mixture is more likely to benefit Isp in a LH2-burning engine because of the low molecular weight of LH2.
Hypergolic upper stages are still fairly common, especially when a coast phase is required because they're especially easy to restart. But the general trend seems to be toward LH2-burning upper stages because of their nearly unbeatable Isps. (What's better? LH2 + LF2 - liquid fluorine? I hope nobody ever flies that.) The Falcon is a singular (?) recent exception that burns kerosine in its upper stage.
I've seen the tank size/weight argument given for why the S-IC burned kerosene rather than LH2. But what about thrust/weight? During first stage flight the Saturn V achieved 4 g (and had to be limited there by shutting down an engine) despite being considerably more massive than the upper stages, which only achieved about 2 g, max. The kerosene-burning F1s seemed to be optimized for thrust while the LH2-burning J2s were optimized for Isp, and that's as it should be since gravity losses are most significant during first stage flight.
You see the same principle in the widespread use of solid rocket boosters during first stage flight. Solids can achieve high thrust/weight ratios more easily than liquid fueled rockets, though their Isps are again limited.
I believe the SPS on the Apollo CSM also had a propellant utilization valve. Because that engine was hypergolic, I suppose it was continually adjusted to maintain a single, fixed and optimum fuel/oxidizer ratio.
I don't recall reading about any PU valves on the LM.
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