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Post by ajv on Jul 28, 2009 20:40:29 GMT -4
Obviously the 390 on the astronautix.com page should be a 360. But the summary doesn't quite agree with the details from the Mission Report (18M): 6.2.2.2.1
It was discovered postreentry that a part of the preretrofire update calculation was in error by approximately 7.89°. This quantity, which references the longitudinal (Xe) axis of the spacecraft coordinate system to Greenwich, was computed incorrectly in the real-time program at MCC-H. The net result of this error was that at retrofire the spacecraft computer was instructed that the spacecraft was at 187.44° west from Greenwich when, in fact, it was at 195.33° west. Thus, to the onboard computer, the spacecraft appeared to be overshooting the target, and the computer displayed corrections for the situation, resulting in a zero-lift indication and an actual undershoot. The MCC-H computer program was correct as written. An earth's rotation rate of 360.98° per day is used in the program which requires that the total elapsed time from G.m.t. midnight, prior to launch, be inserted to derive the spacecraft present position relative to the earth. The 7.89° error resulted from an omission of the elapsed number of days in the G.m.t. of retrofire term. Now misprogrammed with an erroneous rotation rate of the earth is a quite a different description of the error than the mission report's omission of the elapsed number of days. But the effect is the same: 360° vs 360.98°. However, I'm having difficulty getting the figures to add up. But it does work if we take the omission of the elapsed number of days literally - i.e. number of days excluding hours:minutes:seconds. Launch occurred at 1965-08-21 14:00:00 GMT (rounded to the nearest second). Retro-fire occurred at 190:27:43 GET. So retro-fire occurred at 204:27:43 after midnight on 1965-08-21. i.e. 8 days + 12:27:43. The actual solar/siderial ratio (86400/86164) is 360.986°. And 8 * (360.986° - 360°) gives us the reported 7.888° figure. I'm not very happy about the elapsed number of days being taken so literally but we don't actually know how the computer was programmed. It would certainly be possible for the program to separate the days calculation from the HH:MM:SS part.
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Post by ajv on Jul 17, 2009 19:53:30 GMT -4
BTW - can someone point out to me exactly where on the picture the smaller detail is taken from?
The LM is about 35% down from the top and near the extreme right hand side of the full image. Specifically about (4705,18230) of the full size (5064x52224) image.
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Post by ajv on Jul 16, 2009 21:36:14 GMT -4
James DeRuvo of Conversations with Apollo is running an Apollo 11 podcast starting at 19:00 PDT (02:00 UTC). www.talkshoe.com/tc/57606
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Post by ajv on Jun 12, 2009 17:17:40 GMT -4
The cover of David Mindell's book Digital Apollo shows a CGI of the interior of the LM at 520 feet with the 1202 alarm indicator. You can see the computer display in the high resolution image of the cover.
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Post by ajv on Apr 17, 2009 16:04:42 GMT -4
I don't know of any HTML representation of the dot notation.ṁ is Unicode character x1e41 (LATIN SMALL LETTER M WITH DOT ABOVE) and can be embedded in HTML with the sequence ṁ It could be used to simulate the mathematical construct. Of course it will depend on whether the forum software and your browser and computer system can display that character. The management is not responsible for how the first character in this paragraph renders in your browser.The right® solution is to use the MathML standard to embed equations but few browsers currently support it either (e.g. a late model Firefox will handle it). In MathML, the embedded code would be like: <mover accent="true"> <mi> m </mi> <mo> . </mo> </mover> which is a bit clunky but you're meant to use a function editor to create it.
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Post by ajv on Mar 13, 2009 15:42:22 GMT -4
The Apollo 9 flight transcript has the deorbit burn at 10 days, 32 minutes and 15 seconds GET. The mission report records it as 31 minutes and 15 seconds.
Anyone know which is correct?
C'mon, Evan. I'm only up to day one! :-)
I have noticed several discrepancies between the mission report and the transcripts but in this case it appears the technical transcript is wrong.
Re: the technical flight transcript on page (154/3). Although the transmission sequence appears to be correct some of the times are certainly wrong (and indeed skip backwards):
240:29:17 2 minutes 240:30:15 60 seconds 240:31:15 30 seconds 240:31:17 15 seconds 240:32:05 10, 9, ... 240:32:15 Retrofire 240:32:48 ... Burn looks good ... 240:32:14 Residuals are zero. 240:32:27 High-speed tracking shows it's a good burn. 240:34:16 3 minutes
The time in the onboard CM transcript for the High-speed tracking comment agrees with the 240:32:27 figure so the times are probably back in sync by then.
The -2 minute, -60 second and +3 minute calls all indicate an actual burn time of around 240:31:15.
Going back in the transcripts, at 236:01:34 in the technical transcript and the PAO transcript, Ron Evans reads up the maneuver PAD with the time of ignition as 240:31:13.78 and a burn duration of 11.6 and a little later the PAO repeats the figure. The PAO repeats it again (filling air time) at around 236:54.
In the Mission Report, table 3-I reports the time as 240:31:14.9 and table 8.6-II reports the time to a hundredth of a seconds as: 240:31:14.84. The Mission Report supplement 2 (GNC) (Table 4.1) reports the start time at 240:31:14.890 for 11.700s.
At this point I would use the 240:31:15 figure. The times in the technical transcript are clearly wrong around the burn time.
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Post by ajv on Mar 8, 2009 14:40:48 GMT -4
I'm pleased to announce the first release of the Apollo 9 Flight Journal. This was a great test flight and I'm very happy to have been given the opportunity to work on the Flight Journal. The journal currently has the merged transcripts for the first day: launch, transposition and docking, the first SPS test burn and a star sighting test. More detailed journal commentary is planned. Any comments or feedback is appreciated.
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Post by ajv on Dec 31, 2008 14:08:03 GMT -4
I'm going to have to get those DVDs.
Ok, for those of you who have the Saturn I&IB DVD set, who has sat through the entire 25 minutes of the SA-203 tank interior sequence without fast-forwarding?
Sheepishly raises hand.
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Post by ajv on Oct 23, 2008 6:52:34 GMT -4
I've just got back from a interactive show developed and presented by a small local theatre. The concept was that the audience members were the MOCR personnel (White team) during the flight of Apollo 13. First, one audience member (Sara) was drafted onto the flight crew at the last minute due to Mattingly's medical scare. Later, while we were milling around the foyer, the crew wearing pressure suits walked through the crowd and boarded the CM to applause from the onlookers. Then we made our way into the MOCR. Every seat had a designation (I was SYSTEMS) and a console with a half-dozen buttons and switches as well as various indicators (every console was different). Some consoles had headphones for monitoring communication loops (e.g. from the spacecraft crew), others had small built-in TVs. There were two large screens in the room, previous mission patches on the walls, an American flag hanging down and even a portrait of Nixon in one corner. We each had a White Team Manual. The MOCR was run by the Gene Kranz (played by Jason Whyte) and a junior flight director "Michael" (played by Michael Whalley). They took us through the some system checks (we all had to confirm our status when our station was called), countdown and launch. Occasionally the screens would run various clips. Pre-launch, they used some of the Apollo 13 live TV. Sometimes we had live (black & white) pictures of our crew from inside Odyssey. The launch was shown with the screens showing different angles of a Saturn V launch. During boost we saw various shots of separation and staging. Occasionally they would show a TV program with Cronkite (played by Peter Elliot) explaining what was happening at that stage of the mission or an interview with Marilyn Lovell (played by Rachen Forman). Sometimes the main screens displayed computer displays (fuel cell status, oxygen tank pressures etc.) While the main screens were in use the small console TVs were displaying other information or the downlink TV. One minor gripe was that they injected the Quindar Tones randomly in the audio downlinks but I think only people like us would notice that sort of thing. During the launch we got the early S-II inboard engine out which we had to handle under the guidance of the flight directors. Some audience members had find and read out checklists details. Others had to report on system conditions. etc. Later some people had to "work the problem" during a T&D issue which was flown and successfully docked by the backup CMP, Sara. During the TV show the MOCR worked through a checklist which included the decision to stir the cryo tanks. There was a bang onboard and the TV picture broke up. There were lots of flashing indicators and alarms. Sara the CMP reported that they had a problem. The data indicated that they were losing oxygen and the fuel cells and Lovell reported that they were venting something into space. The decision was made to transfer the crew into Aquarius. We ran a procedure to fire the DPS to put Apollo 13 back on a free-return trajectory. It was clear from reports by Surgeon and from people monitoring the onboard loops that Haise was ill. Later, as you probably guess, we had a CO2 warning. Some members of the MOCR worked with Michael to devise a procedure for using the LiOH canisters and then one of the audience members read up the instructions to the crew who had to construct the same device. Meanwhile the rest of us had to work on the power up procedures. We got 4 variables values from around the room and then various teams had to plug the values into a few (simple) equations. After checking that the values were correct we fed the information back when it was requested and Sara set and confirmed the values onboard. During re-entry we had some people timing the LOS but the time came and went. Finally we got TV coverage of the parachutes and a few minutes later the crew emerged to great applause from the MOCR personnel. It was a great show. The audience had to talk with each other and cooperate in solving the tasks and the flight directors kept the production running smoothly. Go along if you get a chance to see it. Apollo 13: Mission ControlBATS Theatre Wellington, New Zealand Saturday 18 October - Saturday 1 November
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Post by ajv on Aug 30, 2008 14:18:21 GMT -4
Nice work again, Bob! I'm not sure about the equigravisphere definition. I would prefer to make a distinction between (literally) an "equal gravity" surface and the (arbitrary) transition between coordinate systems ("the Moon's sphere of infuence"). Combining the two senses has historically meant confusion by writers and conspiracy theorists alike. On the other hand, in the Apollo 12 transcript the PAO says: Apollo 12 entered the Moon's sphere of influence or equigravisphere at 68 hours, 30 minutes 22 seconds. which as we've seen is actually the 40000 (statute) mile mark. One thing that has been lost in your transition to the (great) animation is the nice snapshot of the instant where the spacecraft passed the 40000 mile point showing how far off the center-line the trajectory was at the point where they entered the Moon's sphere of influence.
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Post by ajv on Aug 24, 2008 19:08:44 GMT -4
Nice work, Bob.
To close the circle (pun intended) on this thing would it be possible to add an overlay of the equigravisphere and the 40000 statute mile circle to your plot?
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Post by ajv on Aug 24, 2008 0:11:05 GMT -4
It appears that Apollo 8 was hyperbolic. In Apollo 8 mission report. Supplement 1: Trajectory reconstruction and postflight analysis ( PDF) page 37 they list the position & velocity vectors and for good measure the classical orbital elements for the CSM after MCC-4. (They actually list two sets of vectors in order to compare the RTCC and HOPE (tracking) solutions.) Here are the HOPE/TRW values: Coordinate System | MCI (Moon-centered! :-)) | TIME | GET 061:06:36.000 | X | -20404652.9 ft | Y | 105320326.2 ft | Z | 77026255.9 ft | XDOT | 1029.5138 ft/s | YDOT | -3193.5495 ft/s | ZDOT | -2366.2278 ft/s | SMA | -12162039.3 ft | ECC | 1.533236 | INC | 165.847 deg | NODE | 50.507 deg | ARG PERIAPSIS | 229.258 deg | TRUE ANOMALY | -124.826 deg | PERIOD | --- | APOASIS | --- | PERIAPSIS | 128.84 nautical miles above reference sphere |
Note the eccentricity: 1.533236. And the lack of an orbital period. Note also that at 25012 statue miles we're inside the moon-centric sphere. However, presumably the periapsis from these values doesn't take into account Earth perturbations or something because the predicted pericynthion reported at 061:29 was 62.3 nautical miles rather than the 128.84 above. Bob, perhaps you could push these figures into your orbital simulator and see what happens. I think the coordinate definition is on page 5.1-31 of the Guidance System Operations Plan but just planting the capsule at r travelling at v might be quite instructive.
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Post by ajv on Aug 23, 2008 1:44:40 GMT -4
I've done some more investigation into the Lunar Sphere of Influence issue. The links section of the yaAGC website contains a collection of (large) PDF documents describing many of the onboard computer programs. In the document R-577: Guidance System Operations Plan for Manned CM Earth Orbital and Lunar Missions Using Program Colossus 1 (Rev. 237) and Program Colossus 1A (Rev. 249). we find the following paragraph: This [Basic Reference] coordinate system is shifted from earth-centered to moon-centered when the estimated vehicle position from the moon first falls below a specified value rSPH, and is likewise shifted from moon-centered to earth-centered when the estimated vehicle position from the moon exceeds rSPH. This procedure is described in Section 5.2.2.6 and Fig 2.2-3. Section 5.1.4.1 (page 5.1-31) On page 5.9-1 we find the definition of r SPHrSPH m[eters] 64,373,760 [Reference 14] [Comment 3] In the actual Colossus Build 249 source code (PDF page 1334) we can see the value defined: RSPHERE 2DEC 64373.76 E3 B-29
The definition in the Luminary 1C, Build 131 source code (PDF page 1245) is identical. Incidentally, yes, the Apollo Computers internals used metric values which were converted to feet and nautical miles etc. for presentation to the crew. So, what is the value 64,373,760m? Is it a complicated-to-describe, hard-to-determine value calculated by solving a complex equation based on the Earth's mass and the Moon's mass and the Earth/Moon distance at that particular instant during the mission? No. 64,373,760 m is equal to 40,000 (statute) miles exactly. 40,000 miles EXACTLY! i.e. someone said "Let's use the value 40,000 statue miles - what's that in meters?" Incidentally, the Reference 14 above is to Astronautical Guidance, Richard H. Battin, McGraw Hill Book Co, 1964 and note 3 says: The quantity rSPH is the radius of a sphere that approximates the surface of influence of the Moon as given in Fig 1.3 of Reference 14. So r SPH is just an arbitrary value, inside of which they switch from the Earth-based coordinate system to the Moon-based system. And after plotting the surfaces it's not a very good approximation to the equigravisphere. But that doesn't mean it's a bad surface to use for switching coordinate systems. Ok, so why does the PAO in Apollo 11 report that the sphere of influence was crossed when the spacecraft was 33,822 nautical miles from the moon? 33,822 nautical miles is 38,921 statute miles not 40,000. Is the FIDO on the ground using a different definition? A definition based on some complicated, hard-to-determine value calculated by solving ...? To answer that, let's look at the PAO reports of the sphere of influence event from some of the other missions: Apollo 8: 33820 nautical miles Apollo 11: 33822 nautical miles Apollo 16: 33821 nautical miles What is the first thing that strikes you about these numbers? It's that they're all the same. In each of these three missions the location of the lunar sphere of influence change is exactly the same value. Have you ever had one of those "it's staring you in the face" moments? Take the value 33821 nautical miles from the moon Convert to statue miles 38920 statute miles from the moon And then add the radius of the moon: 1080 statute miles 40000 statute miles from the center of the moon So the only significance of time and location when the PAO mentions that "we'll be crossing into the sphere of influence of the moon" is that the spacecraft is currently crossing the arbitrary 40,000 mile line. The 40,000 value remains the same over all the Apollo lunar expeditions. It's hard coded into the AGC programs. It's not based on a deep analysis of the particular trajectory and it's not the point where the magnitude of the gravitational forces are equal. It's just the point to switch coordinate systems. Oh, and it means that whenever the PAO says they're such-and-such nautical miles from the Moon they're actually reading from a figure that is the distance to the theoretical surface of the Moon not to the center. Oh 2, this means that my "single mistake" calculation in the John Lear thread actually needs two mistakes. It's a mistake to subtract rather than add the Moon's diameter.
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Post by ajv on Aug 21, 2008 18:15:02 GMT -4
The figure of 43495 appears in the Time article dated July 25, 1969 At a point 43,495 miles from the moon, lunar gravity exerted a force equal to the gravity of the earth, then some 200,000 miles distant. Beyond that crest, lunar gravity predominated, and Apollo was on the "downhill" leg of its journey. A GIANT LEAP FOR MANKIND, Time, July 25, 1969. Here is a possible explanation for the 43495 figure. It requires only a single mistake by the writer. At GET 061:39 the Apollo 11 PAO reports the following: This is Apollo Control at 61 hours, 39 minutes. We've had no further conversation with the crew since our last report. Flight Surgeon says there is no indication at this time that they have begun to sleep, but we expect they'll be getting to sleep here shortly. Coming up in less than 10 seconds now, we'll be crossing into the sphere of influence of the moon. A computational changeover will be made here in Mission Control. At this point as the moon's gravitational force becomes the dominant effect on the spacecraft trajectory, and our displays will shift from Earth reference to moon reference. At that point, which occurred a few seconds ago, the spacecraft was at a distance of 186,437 nautical miles from Earth, and 33,822 nautical miles from the moon. The velocity with respect to the Earth was 2990 feet per second, and with respect to the moon, about 3272 feet per second. The passive thermal control mode that was set up for the second time by the crew appears to be holding well at this point, and all spacecraft systems are functioning normally. Mission going very smoothly. At 61 hours, 41 minutes, this is Apollo Control, Houston.
In the Mission Director's Summary Report, dated 24 July 1969: The spacecraft passed into the moon's sphere of influence at 61:39:55 GET. At that time, the distance from the spacecraft to earth was 186,436 NM and its distance from the moon was 33,823 NM. The velocity was 2,990 feet per second (fps) relative to earth and 3,775 fps relative to the moon.
The Moon's diameter (from page 81 of the Apollo 11 press kit) is 2160 (statute) miles. According to the same press kit (page 249) the conversion factor from nautical miles to statue miles is 1.1508. I'm using the press kit figures because that's what the writer could have used. Note: the live PAO reported 33822 nautical miles with the value changing by 0.62 NM/second. The later report used 33823 nautical miles. Let's try to reproduce the Time calculation using 33823 NM. Now, taking the figure of 33823 we want to subtract the radius of the moon which we have in statute miles. 33823 * 1.15 = 38896 I'm using 1.15 because that's the precision of my slide rule (this is the 60's, people!) and because of the same precision my slide rule gives me the answer of 38900. I now subtract the radius of the moon 38900 - 1080 = 37820 So the spacecraft was 37820 miles above the surface of the moon. But because all NASA figures are in nautical miles we need to convert to statute miles for our readers. 37820 * 1.15 = 43493 which my handy-dandy slide rule shows as 43495. This explanation of the 43495 figure only requires a single calculation error by the writer. It's also quite possible that if the calculations were performed by different people at different times they did not notice the misapplication of the units.
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Post by ajv on Jun 18, 2008 2:22:06 GMT -4
Well, we don't have too many members who have talked to astronauts on the way to the Moon so we're probably now up to a total of one.
Welcome, Mike!
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