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Post by scooter on Nov 10, 2009 12:41:21 GMT -4
fm, If you watch NASA TV during a shuttle mission, you will see the map that shows the ground track of the vehicle, the wavy line centered on the equator. The "wave" is a ground track reflection of the orbital inclination. The Apollo missions had a "wave that went about 30 degrees above and below the equator, vs the 48 degree "wave" of the shuttle going to the ISS. An equatorial orbit would reflect a line along the equator. A geostationary (ala Directv sat) would show, ideally, a dot.
Now, these depictions are accurate for near circular orbits. Eccentric orbits result in strange groundtracks, the Molnyia (sp?) being a classic in orbit design. The Apollo trans-lunar ground track was interesting. It started it's burn around the equator, on a northeast heading. It accellerated rapidly northeast and by the end or the approx 5 min burn was well along towards the 30N latitude. The higher (in altitude) it got, the longer it remained at this high latitude. This high latitude, combined with the southerly offset of the VAB in the western hemisphere (VAB centered around mag poles, not geographic), had the flight going through the thinner, weaker northern edge of the belts.
The free simulator "Orbiter" is a great way to see how this works, and is a fun way to learn some orbital mechanics. It's really easy to see how they designed the trans lunar trajectory to do this.
It's basic rocket science, but it's great fun to learn. (ETA...fm, did you even read the answers to the questions in your illustration??)
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Post by JayUtah on Nov 10, 2009 13:03:14 GMT -4
Im seeing it in 3D.No, you're seeing it in 1D. You consider only geodetic altitude. You are not even remotely considering either the transfer orbit or the belts as three-dimensional entities oriented variously in three dimensions. In other words, it doesn't help at all with my questions.Your questions all presume that your understanding of the geometry is complete and correct. It is not, and you resist all efforts to be educated. Lets make it simple...No, that's your problem: you're trying to make it simple. Let's make it correct instead. do any of you dispute the information I quoted from NASA that for about 4 to 5 hours the Apollo 11 craft was within the range of the Van Allen Belts?I dismiss any statement that includes the phrase "in range of the Van Allen belts." What is that supposed to mean from an astrophysics standpoint? Belts that circle our entire Earth except at the poles?No, I dispute "except at the poles," because it is inexact. Latitude, longitude, and geodetic altitude are the three most important variables that describe the exposure profile of the trapped radiation belts. There is an enormous amount of variance, and you are simply ignoring it. Sounds like a situation where the shortest distance between point A and B is a straight line.No orbit is ever a straight line. The inclinations of the translunar trajectories are published. The orbital elements are published. You may either use the exact publish figures, in which case you will have your answer regarding the Van Allen belts; or you may continue to embarrass yourself by handwaving about straight lines. Im just not seeing any evidence that the Apollo craft left Earth and made some big longitudinal curve to go over the belts...Then you need to study how orbits work. The translunar trajectory for each mission had a certain inclination. When you work that out and plot it against the positions of the Van Allen belts, then you will see it. Stubbornly trying to reduce the problem to your level of understanding does not produce evidence of fakery. ...thats should be easier to look at since it was basically a straight path, right?No. No orbit is ever a straight line. The return portion of the transfer orbit -- the transearth trajectory -- was largely the same as the departure trajectory. Thats more than 2 hours going through the VABs or 3 hours and 30 minutes if you want to use the 40.000 mile distance.No. You are still considering the problem only in the one dimension: geodetic altitude. That is as wrong as it can possibly be. Until someone can show me different...We've been doing nothing but that. You keep rejecting it and trying to substitute your own simplistic understanding. Please endeavor to learn something about orbital mechanics. Tell you the truth, I wouldn't be surprised if they found radiation belts around the moon as well.Since the Moon has no significant magnetic field, I can't imagine how that would occur. And that pretty much explains why you don't understand much about the geometry of Earth's trapped radiation belts. Talk about cherry picking quotes, comparing this to published...What about that quote is cherry-picked? It is Van Allen's direct, solicited response to you and your "hoaxers." ...show me where he published a scientific paper or article where he reverses his previous published claims prior to Apollo.He didn't reverse anything. You are the one cherry-picking quotes from his earliest papers and trying to claim that this means he believes Apollo couldn't have happened. It is you who draws the connection between Van Allen's pre-Apollo work and the feasibility of Apollo. Therefore it is to you that we turn to for justification. You have the burden to prove that all those quotes from the late 1950s are Van Allen trying to prove that Apollo was impossible. Since Van Allen worked on the Apollo project, I think you're going to have a hard time. where does he retract the dangers of the VABs in the quote?He doesn't retract the danger. He repudiates your understanding of the danger. That's the problem. You don't let the notion enter your head that you might just possibly be wrong about Van Allen's early (or later) work on the trapped radiation environment. This last quote from him is Van Allen gently correcting that understanding. But apparently you're too stubborn to be corrected by an eminent scientist. ...when every scientist says...Please give the names of three qualified, practicing, degreed astrophysicists who clearly state that the Apollo missions were fake and clearly state that it is the Van Allen belts that are the reason they must have been faked. Put up or shut up. Anyway, I have to give this to the hoaxers...And who elected you the arbiter of these principles? You clearly don't understand anything about the standard models of trapped radiation. You clearly don't understand anything about magnetic fields. You clearly don't understand anything about orbital mechanics. And you clearly don't accept the opinion of an eminent scientist in the field, speaking directly about your beliefs. You are as ignorant and biased as they come. Your awarding of points as if you are some dispassionate judge in the matter is just silly. (vague remark)The remark is not vague. It very clearly, very explicitly, very directly tells you that you don't know what you're talking about. Sorry, for me its the end of that discussion.As well it should be, if you're going to directly contradict the explicit statement of the man upon whose work you have attempted to make a case.
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Bob B.
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Post by Bob B. on Nov 10, 2009 13:27:42 GMT -4
…and do not show the 1.5 orbit around the Earth. The parking orbit around Earth is irrelevant to the issue. This orbit was well below the belts and was no more dangerous than any earth-orbit mission before or after Apollo. Lets make it simple, do any of you dispute the information I quoted from NASA that for about 4 to 5 hours the Apollo 11 craft was within the range of the Van Allen Belts? I’ll agree that after about 4 hours the spacecraft reached a distance that is approximately equal to the radiation belts’ maximum distance from Earth. However, I don’t agree with your simplification that the spacecraft within the radiation belts for this duration. It is a more complex three-dimensional problem. Belts that circle our entire Earth except at the poles? ...but that are not homogeneous. The radiation belts are more intense in regions near the magnetic equator. Im just not seeing any evidence that the Apollo craft left Earth and made some big longitudinal curve to go over the belts, skimming them, and back down to the moon vrs a straight line to or maybe a latitudinal curve. I pointed out in my previous post that the drawing posted by Jason is incorrect in that it places the moon in the wrong position. Please read reply #99. Every picture shows this: What you don’t see in that illustration is that the Earth’s magnetic equator is inclined to the plane of the spacecraft’s trajectory. The spacecraft was able to skirt above or below the most intense zones in the radiation belts, thus largely circumventing the problem. Anyway, what about the return flight, did that take an hour through the belts? thats should be easier to look at since it was basically a straight path, right? The return trip is essential the same as the outward trip, except in reverse. Thats more than 2 hours going through the VABs or 3 hours and 30 minutes if you want to use the 40.000 mile distance. I dont see anything here under an hour. Until someone can show me different, I count up to six possible hours in the VAB coming and going. Yes, but through what part of the belts? You are still failing to see that the radiation belts are not the same everywhere. Even if they where “in the VAB” for six hours, that is no big deal if they were passing through the low intensity fringes.
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Post by gillianren on Nov 10, 2009 14:12:55 GMT -4
I find this "NASA wouldn't send out astronauts unless they knew it was completely safe" argument to be a little tiresome. There is very little in this world that could be classed as "completely safe". Getting into my car and driving into the office every day is a risky business - it only takes one idiot to do something stupid and you can end up in the hospital (or worse), as my parents can testify. For heaven's sake, even just saying home isn't completely safe! Nothing is. Yes, I've nearly been run down in the road while crossing the street, but I've also nearly injured both myself and my cat by stepping on him in a dark hallway. My boyfriend burned his hand taken a pizza out of the oven the other night. And we're supposed to believe that NASA wouldn't strap people to a bomb and shoot them into orbit until it could be completely safe? What ignorance!
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Post by nedd on Nov 10, 2009 14:56:33 GMT -4
Per miles traveled per person, I would think that space travel is a very safe mode of transport.
Of course the Apollo missions weren't completely safe - they had an abort tower, and reserve parachutes, and who knows what fail-safes and contingency plans were in place in the event something goes wrong. If it was completely safe, why bother having any of that stuff?
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Post by scooter on Nov 10, 2009 15:36:04 GMT -4
[quote author=fm board=theories thread=2614 post=75312 time=1257866947 Anyway, I have to give this to the hoaxers 2 (published quotes) to 1 (vague remark) regarding Van Allen until we find something more to support the opposite. Sorry, for me its the end of that discussion. spacemath.gsfc.nasa.gov/weekly/3Page7.pdffrom the link you provided here... "4. Some people believe that the Apollo moon landings were a hoax because astronauts would have been instantly killed in the radiation belts. According to the US Occupation Safety and Health Agency (OSHA) a lethal radiation dosage is 300 Rads in one hour. What is your answer to the 'moon landing hoax' believers? Note: According to radiation dosimeters carried by Apollo astronauts, their total dosage for the entire trip to the moon and return was not more than 2 Rads over 6 days. The total dosage for the trip is only 11.4 Rads in 52.8 minutes. Because 52.8 minutes is equal to 0.88 hours, his is equal to a dosage of 11.4 Rads / 0.88 hours = 13 Rads in one hour, which is well below the 300 Rads in one hour that is considered to be lethal. Also, this radiation exposure would be for an astronaut outside the spacecraft during the transit through the belts. The radiation shielding inside the spacecraft cuts down the 13 Rads/hour exposure so that it is completely harmless. Space Math spacemath.gsfc.nasa.gov" The link YOU posted gives you the answer... [/quote]
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Bob B.
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Post by Bob B. on Nov 10, 2009 16:20:41 GMT -4
spacemath.gsfc.nasa.gov/weekly/3Page7.pdffrom the link you provided here... "4. Some people believe that the Apollo moon landings were a hoax because astronauts would have been instantly killed in the radiation belts. According to the US Occupation Safety and Health Agency (OSHA) a lethal radiation dosage is 300 Rads in one hour. What is your answer to the 'moon landing hoax' believers? Note: According to radiation dosimeters carried by Apollo astronauts, their total dosage for the entire trip to the moon and return was not more than 2 Rads over 6 days. The total dosage for the trip is only 11.4 Rads in 52.8 minutes. Because 52.8 minutes is equal to 0.88 hours, his is equal to a dosage of 11.4 Rads / 0.88 hours = 13 Rads in one hour, which is well below the 300 Rads in one hour that is considered to be lethal. Also, this radiation exposure would be for an astronaut outside the spacecraft during the transit through the belts. The radiation shielding inside the spacecraft cuts down the 13 Rads/hour exposure so that it is completely harmless. Space Math http://spacemath.gsfc.nasa.gov" That page does a pretty nice job debunking this nonsense about the deadly radiation belts, but I'd like to point out a couple things. First, the 25,000 km/hr velocity is an rough average used to simplify the calculation, and is about what the spacecraft will be traveling at the midpoint distance of 4 earth radii. By the time the spacecraft reaches 4 radii, it has already traversed nearly all the orange region. This means the spacecraft is moving faster than 25,000 km/hr as it moves through the orange area. Thus, the exposure time in the most intense region is actually shorter than that calculated, thereby resulting in a lower dose. Second, the inclination of the spacecraft trajectory (black bar) is drawn at an angle of approximately 23 degrees. During Apollo, the spacecraft following trajectories with inclinations varying from 28.5 to 32.5 degrees, with an average of about 30.8 degrees. If the black bar is repositioned to the correct angle, the radiation dose is significantly reduced.
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Post by Jason Thompson on Nov 10, 2009 17:41:10 GMT -4
OK, here's a better sketch. Still not perfect but my time is limited and my 3D rendering skills even more so. The justification for the features of this image: Earth's rotational axis, and hence its equatorial plane, is tilted 23.4 degrees relative to the plane of the ecliptic. The van Allen belts, being formed by the the Earth's magentic field, are aligned along the Earth's geomagnetic plane, which is itself inclined about 11 degrees to the Earth's equator. This displacement happens to be southward for the US, so on the US side of the world the plane of the belts lies south of the equator by about 11 degrees. Apollo 11 launched in the middle of July, so the Earth's north pole would be tilted towards the Sun (the Sun is to the right in the diagram). The Moon was close to new at this time, so the spacecraft TLI orbit carried it in the direction of the Sun. Apollo 11 initiated TLI from an orbit inclined 32.5 degrees from the Earth's equator. You can see from the sketch that this inclination carries it through only the less intense regions of the belts. It bypasses the really intense regions almost entirely, and is out of any area that may be considered part of the belts well before it would be had it launched off in the same plane as the belts. This is hopefully illustrative of why you cannot simply consider altitude as the defining factor of whether or not they are in the belts. Yes, the belts may well extend several earth radii, but not in the same direction as the spacecraft was travelling.
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Post by randombloke on Nov 10, 2009 19:06:55 GMT -4
What do you suppose are the odds that fm will: 1. Ignore Jason's excellent post and diagram 2. Complain about the geomagnetic offset because "North is North!" 3. Ask for the callsign/registration number of the ecliptic (aero)plane 4. All of the above?
P.S. Jason; thank you for that. It really crystallises a few things about the Earth's magnetic fields and spatial orientation that have seemed to flow past each other without making contact in my head for a while. P.P.S. Where is the Moon in relation to that diagram? Off to the right, of course, but somewhere near the Apollo orbital plane, yes?
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Post by Jason Thompson on Nov 10, 2009 20:14:05 GMT -4
The Moon's orbit is inclined about 5 degrees to the ecliptic, and judging by some simulators I've seen it was above the ecliptic plane at the time, so it's about halfway between the ecliptic and Apollo 11's orbital plane.
However, Bear in mind there is not a viewpoint that would actually allow you to look along all the planes as they are shown in that diagram. The moon's orbital plane would be inclined relative to the screen too, so that it would actually intersect that of Apollo 11. These things get very hard to draw in 3D.
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Bob B.
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Post by Bob B. on Nov 10, 2009 21:58:18 GMT -4
However, Bear in mind there is not a viewpoint that would actually allow you to look along all the planes as they are shown in that diagram. The moon's orbital plane would be inclined relative to the screen too, so that it would actually intersect that of Apollo 11. These things get very hard to draw in 3D. I think, also, Apollo 11's orbit is likely not exactly edge-on as shown in your illustation. As drawn, the argument of periapsis* is 90-degrees, which is probably not the case. Changing the argument of periapsis would tilt the orbital plane somewhat to our line-of-sight, making it possible for the trajectory to intersect the Moon. Of course, this might also cause the spacecraft to pass more deeply into the VAB. By the way, nice illustration, Jason. (* The angular distance between the ascending node and the point of periapsis.)
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Post by JayUtah on Nov 10, 2009 22:29:22 GMT -4
Bear in mind there is not a viewpoint that would actually allow you to look along all the planes as they are shown in that diagram.Yes, that's really the only criticism that can be mounted against your drawing. It expresses enough of the important orientation relationships so that one can see the problem is not so easy as it seems. But the important planes -- seen edge-on in this drawing -- don't really share the line of sight in common. These things get very hard to draw in 3D.And very hard to conceptualize in real life. That's why the best way to deal with them practically is to think of orbits as purely abstract mathematical entities and simply trust the math.
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Post by Jason Thompson on Nov 11, 2009 5:12:19 GMT -4
And that's why diagrams in press releases tend to simplfy things in order to make the idea accessible to the average reader. Those drawings, such as fm cited, are for illustrative purposes only, and can certainly not be used in any meaningful way to determine the spacecraft's actual trajectory.
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Post by echnaton on Nov 11, 2009 10:09:16 GMT -4
Nice drawing Jason. It helps clarify the problem, particularly when combined with Bob's and Jay's comments. Thanks.
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Bob B.
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Post by Bob B. on Nov 11, 2009 10:43:01 GMT -4
If I can find the time, I’d like to map Apollo 11’s trajectory to the Moon; perhaps plotting the spacecraft’s polar coordinates versus time. At present, I’m not sure I have all the orbital elements needed to do this. If I can figure out exactly when and where the spacecraft was on its outbound journey, we might be able to develop a pretty good estimate of the (unprotected) radiation dose. Apollo 11 initiated TLI from an orbit inclined 32.5 degrees from the Earth's equator. I’d like to add one note here… Although it is true TLI initiated from an orbit with an inclination of 32.5 degrees, the inclination of the trans-lunar orbit was 31.4 degrees.
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