|
|
Post by JayUtah on Nov 17, 2005 17:50:04 GMT -4
The ascent thruster produced a flame when it is said a flame would not be seen in space.
Ignition transient.
The fuel mixture is the same used on other applications that produce exhaust fumes prior to lift off.
That's because nitrogen tetroxide is pre-injected and it reacts chemically with air. That produces smoke. If you watch N204/hydrazine combustion a few seconds after liftoff, you see that there is no smoke and almost no flame -- even in air.
Pre-injected oxidizer creates an initial imbalance in fuel mixture. Incomplete combustion occurs, producing intermediate products that aren't there in steady-state combustion. They incandesce. That's the ignition transient.
Ambient pressure resists plume dispersion. If the plume is kept columnar, it's kept hot and thus incandescent. In a vacuum, the plume disperses too rapidly to retain enough heat to maintain incandescence. Even RP-1 plumes, which are full of particulates and bright yellow-orange, are almost invisible at steady state in a vacuum.
The panning up so quickly was not possible.
Why not?
The camera would've been huge.
Why?
...you can in fact find info on how large cameras were back in 1969.
Studio cameras, yes.
Studio cameras of the 1960s contained three separate vidicon tubes and associated optics. They were also built to optimize for best image quality, knowing that they would be heavy. Studio cameras today are still very large and heavy compared to consumer camcorders. I can go on at length on the reasons why -- chiefly for ease of service and repair.
The Apollo cameras used only one vidicon and achieved color using a spinning color wheel and a field-sequential signal format. The camera used a smaller vidicon and did not have as many features or quality factors as a studio camera.
This is just basic engineering. The prime requirement drives the design, and other requirements are relaxed to accommodate it. If the prime requirement is size and weight, you engineer for size and weight and punt a little on quality or other aspects.
The gentleman to start this thread has worked in the biz for several years and he's questioning it as well.
But I'll bet he hasn't studied the Apollo designs either. I've worked in the television industry too. I can discuss the differences between Apollo TV cameras and professional studio TV cameras.
The flag was planted by hand.
Bzzt.
After Apollo 11 the flag staff was redesigned. It came in two segments that were threaded together, and the bottom was given a sharp point. The bottom portion was hammered firmly into the ground using a geology hammer. Then the top part was screwed into it.
How deep it was might be evidenced on the video when they planted it, I'm not sure.
So you haven't seen the video? Yet you presume to speak authoritatively about how the flag was planted and how deep?
This is why you can't be taken seriously. You don't differentiate between substantiable fact and wild speculation. You just presume that somewhere there's evidence that applies to your argument. But you don't consider that we've already seen that evidence and know better than you.
I say the flag pole bend over because that is what the video evidence depicts.
No, that's how you interpret what you're seeing. The flag is not being seen from directly above. Therefore not all apparent motion or deflection you see can be attributed to physical flag bending.
No doubt the staff did flex a bit in response to the plume loading. But it is important how much it is alleged to have flexed. If it flexed 45 degrees then it would indeed be odd for it to remain standing. But if it flexed only 5 degrees then it's not a big deal. So if you're the one arguing that the flag flexed too much to be credible, then you have the burden of proof to analyze and compute how far it actually moved, and then argue that this is excessive. Otherwise you're just begging the question.
I don't know but maybe you do; how many pounds of thrust did the ascent rocket produce upon lift off..?
3,500 lbf total at the exit plane. However, that's not how much fluid pressure would strike the flag. The plume density decreases according to the square of the distance. And only a very small amount of the total plume would hit the flag because the flag is only in one direction and the plume spreads roughly evenly in all directions as it impinges on the top of the descent stage.
|
|
|
|
Post by Jason Thompson on Nov 17, 2005 18:01:42 GMT -4
Jason, yes, it produced a flame but it is only seen after the module lifted off a few feet. There is no flame seen in any video while the ascent module is still sitting on the descent module.
There is a bright flash at the second all that mylar is blasted off. However, the flame produced by the propellants in the LM ascent stage once steady state combustion is achieved is near enough transparent.
I have seen the clip.
Then answer the question. What exactly blasts the mylar insulation all over the place if not rocket exhaust?
It would take a large amount of chemicals to lift it off so fast, as it's heavy, even in lunar atmosphere. Do I have the diameter of the pipe, the chemical compounds reserached, the test results varified, etc., etc, to make this claim..? No I don't, it's simply my theory.
And there's the crux of our whole problem with you and your arguments, Moon Man. Please do try to take this onboard:
you are applying your limited understanding to producing theories about how mechanical systems operate, but such operation is not a matter of theory but of verifiable fact.
The LM weight is known and documented. The thrust you get from mixing the two chemicals used as propellants is known and verifiable today by anyone who works in rocketry within or outside of NASA, or anyone with a detailed knowledge of chemistry. Therefore, it can be calculated how much propellant would be required to accelerate the LM ascent stage from the lunar surface to orbit. You make up your theories based on some fuzzy notions about weight and expect the rest of us to take them seriously when you could actually go out and find out the real figures for yourself. If you are not prepared to put in the research needed to back up a claim based on science and engineering, don't expect a bunch of scientists and engineers to take your theory seriously.
can you confirm that the camera was built in 1972..? Maybe you can but you haven't done so in this message and yet you bash me for saying something without providing the proof you claim I am required to provide before opening my mouth.
You are absolutely correct. I should have checked when the camera was built, not when it was used. I apologise.
However, my point still stands that you stated how far into the surface the flag had been planted, used it as a basis for arguing, then admitted you actually did not know how far into the ground the flag had been planted because you had not seen the clip. That undermines your argument every bit as much as my error does mine.
|
|
|
|
Post by AstroSmurf on Nov 17, 2005 18:13:04 GMT -4
You're correct in that there's no ignition switch - the propellants (Aerozine 50 and dinitrogen tetroxide) were chosen specifically because they ignite upon contact so there would be fewer possible malfunctions. When you say that it takes off straight away, have you watched the film with freeze-frame and attempted to measure how far it's moved with time? I think you'll find that it accelerates upwards at a fairly smooth rate, even though it's fairly quick. And I think you mean lunar gravity, not atmosphere.
The hypergolic propellants chosen burn with a nearly invisible flame. If you can find some footage of a Titan II launch (it uses the same propellants), you'll see that the flame is a nearly transparent, slightly pinkish colour. If you view that against a dark background, it's not all that surprising that it wouldn't be visible. In the Apollo 17 footage, you can't see it until you are watching almost straight up into the engine bell.
As for Wikipedia, *anyone* can edit the information there. It's a good place to familiarise yourself with a subject, but it shouldn't be used as an authoritative source. Please do read the link provided - that will bring you up to speed on a lot of topics that are already covered so we don't have to go over them again.
|
|
|
|
Post by Count Zero on Nov 17, 2005 18:28:53 GMT -4
There is a thermal shield between the ascent and descent modules. The ascent thruster produced a flame when it is said a flame would not be seen in space. There was no exhaust (maybe not the right word) prior to lift off like on every other NASA rocket -- it just took off -- 3, 2, 1 lift off. The fuel mixture is the same used on other applications that produce exhaust fumes prior to lift off. No one ever said it is impossible to see a flame in a vacuum; flames are just much less visible in a vacuum. I have always maintained that a brief flash of light can be seen under the LM’s engine for about a second just as the ascent stage lifts off the descent stage. There is also something known as an ignition transient, at which time the flame is more easily visible. This occurs very briefly at engine ignition when the oxidizer to fuel ratio has not yet settled in to its optimum steady state mixture. Some rocket engines take longer to reach full power than others. For example, the LOX/LH2 Space Shuttle Main Engines and the Saturn V's F-1 engines took several seconds to reach full power. During this build-up & stabilizing period, the rocket is clamped to the pad to keep it from lifting up and settling back down, possibly hitting something with a nozzle (this happened several times in the early days, until we learned the hold-down trick). When the engine reaches full thrust, they blow the clamps and let her fly. Some rockets reach max thrust very quickly. These don't need to be held-down. A fine example of these are the Space Shuttle's Solid Rocket Boosters. They are so fast that the same signal that tells them to ignite also releases the hold-down clamps. SRB ignition and liftoff are simultaneous. The LM hypergolic Ascent Propulsion System (APS) reaches max thrust in a fraction of a second. There's no need to hold it down, so the explosive bolts that hold the ascent stage to the descent stage are blown at ignition. Again, ignition and liftoff are simultaneous. The second stage of the Delta rocket is a modified version of the same rocket the LM APS used. Here is a video of a Delta II launch. Staging occurs just over half-way into the clip. Notice that just after the first stage separates, there is an ignition transient that lasts just a fraction of a second, then the flame is basically invisible. This is almost exactly what we see in the LM ascent video. |
|
|
|
Post by JayUtah on Nov 17, 2005 18:31:01 GMT -4
There is no flame seen in any video while the ascent module is still sitting on the descent module.Nor should there be. For Earth launches we purposely hold the rocket down for a few seconds after the engine ignites. For multiple-engine boosters this is so we can let all the engines reach equal thrust. For all boosters it's so we can work through the ignition transient and reach steady state, and give the controller computer time to make sure the engine is functioning normally. Pressure-fed engines like the APS have very short ignition transients. The APS transient is roughly a third of a second. The steering jets have transients measured in milliseconds. Large engines, like those used on Earth-launch boosters, are pump-fed. It takes about six seconds for the SSME fuel pumps to come up to full speed, and about 8 seconds for the F-1 fuel pumps to reach full speed. It is dangerous to let the rocket go before the engines reach steady state because guidance is a problem. It would take a large amount of chemicals to lift it off so fast, as it's heavy, even in lunar atmosphere.Handwaving. Do I have the diameter of the pipe, the chemical compounds reserached, the test results varified, etc., etc, to make this claim..? No I don't, it's simply my theory.It's a theory based on absolutely nothing except your predetermined desire not to believe that Apollo was possible. You have no justification for any of your expectations, no expertise in rocketry, and no hard facts. You simply say it should be a certain way, wasn't, and therefore is false. Bob and I are both qualified to make rocket propulsion computations, and we have both independently made the computations necessary to validate the APS behavior. Further, the Apollo LM APS design was built by various companies in various revisions up to the mid-1980s and used as a successful upper stage motor. Its flight characteristics are well known. I'm not sure if the camera was capable of panning so quickly. I don't believe it was.3 degrees per second. The LRV was parked about 100 meters away from the LM. Can I scientifically prove it beyond a shadow of a doubt..? No, I cannot.You can't provide any proof of any kind. You supply only expressions of disbelief. That's the problem. You arrive at your disbelief with no proof whatsoever. How are we to avoid concluding that you just believe what you want to believe and facts be damned? Bob, some Abers have claimed you cannot see a flame. Maybe no one on here claimed this but it was been claimed.Because the video frame is so indistinct it's difficult to say whether we're seeing a flash from the engine or perhaps sunlight glinting off something. It is reasonable to expect a flash occurred, because near-duplicates of the ascent engine have a visible transient in a vacuum. science.ksc.nasa.gov/cgi-bin/rrg2.pl?video/payloads/missions/mars-odyssey/mars2001-launch.rmWatch the film until the interstage drops away and the second stage ignites. But it may not be reasonable to expect that flash to be visible in a video that includes other things. I do not believe you would be able to see any flame or flash proir to live off because the ascent module is sitting on the descent module. You only see te flame once it has litfed off.That may or may not be true. Once the ascent stage has cleared the debris, the transient is long over. And you would only see visible flame during the transient, or if -- as occurs much later in the video -- you are looking directly up the nozzle into the thrust chamber. But actually the maximum thrust ever developed by an engine occurs about two-thirds of the way through the transient. So the ship will expierience about 5-10% more thrust than nominal right at ignition. Why would the thread starter lie just to ask a question or make a comment..?To make the question or comment seem more significant or damaging.
|
|
Bob B.
Bob the Excel Guru?
Posts: 3,072
|
Post by Bob B. on Nov 17, 2005 18:38:39 GMT -4
The hypergolic propellants chosen burn with a nearly invisible flame. If you can find some footage of a Titan II launch (it uses the same propellants), you'll see that the flame is a nearly transparent Here a Titan II launch:  The exhaust coming from the engines is almost completely transparent. It is most visible where the two exhaust streams impinge on each other. The LM has a single engine so this wouldn't happen in that case. Please don't be fooled by the white 'cloud' at the bottom of the frame. That is a stream of water being sprayed onto the pad and not part of the exhaust stream. Also note how the exhaust streams stay in a tight column. In a vacuum the exhaust quickly expands outward, thus greatly reducing its visibility. |
|
|
|
Post by Count Zero on Nov 17, 2005 19:08:39 GMT -4
Is anyone selling "I ToSeeked Jay" t-shirts? ;D
|
|
|
|
Post by Moon Man on Nov 17, 2005 19:17:10 GMT -4
Thanks for the replies and questions. I will answer them eventually. I'm taking a break and reading for a while. Jay, I love the handwaving remark. I first saw it used on BA's board. Any idea who coined that term..?
|
|
|
|
Post by JayUtah on Nov 17, 2005 19:58:24 GMT -4
"Handwaving" is a pretty common term, although I use it more than other people. I learned it while teaching college classes. A "handwaving explanation" is a brief explanation that only makes references to concepts that relate to a question without explaining any of the relationships in detail or offering proof. Teachers use it to save time in lessons, so that they don't derail a good line of thought.
The "bad" kind of handwaving is what is often offered by pseudoscientists who hope that the listener simply gets the impression that the proponent knows what he's talking about and should be trusted.
For example, you say that the LM requires lots of chemicals to achieve liftoff, even in lunar gravity, because the LM is heavy. Well, those are all quantitative questions that would require quantitative answers. And your comment glosses over many details such as the potency of the chemicals in question. You might be hoping that merely making reference to the weight of the LM and downplaying the effects of lesser lunar gravity, a reader might agree with you that lunar liftoff seems improbable. But you haven't really solved the math to which you allude; you just imply that it would work out in your favor.
|
|
|
|
Post by PhantomWolf on Nov 18, 2005 2:28:45 GMT -4
I'd point out that while nothing to do with the fuels used in the LM, other engines have transparent flame to, the most famous being the SSME (Space Shutle Main Engine.)
|
|
|
|
Post by Moon Man on Nov 18, 2005 4:12:44 GMT -4
"Handwaving" is a pretty common term, although I use it more than other people. I learned it while teaching college classes. A "handwaving explanation" is a brief explanation that only makes references to concepts that relate to a question without explaining any of the relationships in detail or offering proof. Teachers use it to save time in lessons, so that they don't derail a good line of thought. The "bad" kind of handwaving is what is often offered by pseudoscientists who hope that the listener simply gets the impression that the proponent knows what he's talking about and should be trusted. For example, you say that the LM requires lots of chemicals to achieve liftoff, even in lunar gravity, because the LM is heavy. Well, those are all quantitative questions that would require quantitative answers. And your comment glosses over many details such as the potency of the chemicals in question. You might be hoping that merely making reference to the weight of the LM and downplaying the effects of lesser lunar gravity, a reader might agree with you that lunar liftoff seems improbable. But you haven't really solved the math to which you allude; you just imply that it would work out in your favor. This was going to be my closing argument in the Great Moon Man Debate but I will make it now. At lift-off from the Moon, the Apollo 17 Ascent Stage weighed 10,997 pounds, including about 240 pounds of rock and soil samples About half (5261 pounds) of the total weight was propellant. www.hq.nasa.gov/office/pao/History/alsj/apollo.engin.htmlThis weight might not include the weight of the two astronauts so we may need to add another 320 pounds or so. Therefore, they needed 5261 pounds of chemicals mixed in order to lift off or NASA would not have added so much propellant, as weight was an issue in every facet of the mission. Clearly this amount of chemicals was not mixed and added to the engine in 2, 3 or 5 seconds. We would need the diameter specs on the pipes or hoses to prove it was not possible to add this much propellant this quickly. We would also need the specs on the pump or other device that delivered the propellant. Like many of the other issues I've cited I bet these specs are not available. Clearly the wee flame we see is not from 5261 pounds of chemicals igniting.  Also compelling is the fact that the ascent stage and descent stage were attached together upon landing. They were secured together somehow. I cannot find any data how they were secured. Most importantly, the two stages were required to be unlatched prior to lift off, since only the ascent module lifts off. Unlatching them would've required the astronauts to conduct this task, since nobody else was on the moon to do it. The conversation log evidences that they did not do so at anytime, thus proving beyond any doubt, and without further showing, that this was all a hoax. www.hq.nasa.gov/alsj/a17/a17.trvlm3.htmlwww.hq.nasa.gov/alsj/a17/a17j.html |
|
|
|
Post by gwiz on Nov 18, 2005 4:41:36 GMT -4
...they needed 5261 pounds of chemicals mixed in order to lift off or NASA would not have added so much propellant, as weight was an issue in every facet of the mission. Clearly this amount of chemicals was not mixed and added to the engine in 2, 3 or 5 seconds. We would need the diameter specs on the pipes or hoses to prove it was not possible to add this much propellant this quickly. We would also need the specs on the pump or other device that delivered the propellant. Like many of the other issues I've cited I bet these specs are not available. Clearly the wee flame we see is not from 5261 pounds of chemicals igniting. Oh dear, oh dear, he gets worse. The 5261 lbs of propellant isn't burnt at once, but gradually over the several minutes of the ascent burn. There are no pumps, the motor is pressure fed. Ypu just open a valve in each propellant line and the flow starts. And he claims the numbers aren't available when what he means is that he can't be bothered to search for them. |
|
|
|
Post by Fnord Fred on Nov 18, 2005 4:58:46 GMT -4
320 Pounds for astronauts? This is the moon, remember - It's ~1/6 Earth Gravity. Even if their equipment weighed a hundred pounds each and they were 200 pounds (back on earth), that would only be ~100 pounds on the moon. Seeing as how the lunar ascent modules engine could only lift ~3500 lbs IIRC, I'd bet that the rest of your weight calculations are similarly about triple what they should be. Or at the very least, that's what the hoaxers would say if it was faked - it IS a pretty blatant f**kup to ignore. Not at once. Did you expect them to ignite it all at takeoff? Do you realize the kinds of technical problems involved in trying to get that much stuff to mix at once? Even if they could, the explosion would've blown the LM into bits. Assuming they overcame those minor difficulties, how would they correct their trajectory to meet up with the CM? When they launch a rocket from earth, do they burn all the propellant at once while it's still on the pad? No, they burn it for several minutes, at least. They have to adjust from going straight up to going parallel to the earth's surface. They also may have to do orbital correction burns, depending on how the initial launch went and how long they have to stay out there. Well, let's compare the options here: 1. A government conspiracy that has millions of people under it's control, capable of killing dissenters and/or fooling PHD'd scientists into thinking that the moon landings were legitimate, completely screwed the pooch and left out the LM Ascent Module Seperation phase from the conversation logs of every single mission. OR: 2. The seperation mechanism was either automatically triggered with the ascent engine, was triggered by the astronauts while they were triggering the ascent engine without mentioning it, or you just didn't read the convo logs correctly. Gee, you certainly hit a home-run there.  |
|
|
|
Post by colinr on Nov 18, 2005 4:59:45 GMT -4
I hesitate to weigh in - but that last posting re the Ascent stage operations was so full of misconceptions even I as a non technical person can spot them
!The Ascent/Descent stage was separated as part of the Ascent engine ignition process , by a series of explosive bolts , and guillotines which severed all connections between the 2 stages , all this occurred automatically - the use of such bolts has a long history in Aerospace operations
The Ascent engine did not use pumps - this being rejected early in the design , instead the system was pressurized helium, no moving parts -. The Ascent engine HAD to work , therefore engineers , real engineers , designed the system to be as simple as possible. The 2 main valves controlling the flow of propellant and oxidizer could , if necessary be operated manually if the solenoids controlling them failed.
MM - my i suggest you move away from your PC , just for a while and do something radical , READ SOME BOOKS - might I suggest starting with "Moon Lander - How we Developed the Apollo LM" by Thomas J Kelly - published by the Smithsonian press in 2001
this is beautifully written , quite complex, but fascinating work detailing the tortuous, and demanding process of designing and fabricating the world first true space craft - Kelly himself led the initial design team , and was instrumental in getting the vehicle built
No all the answers to the questions you have can be found on line ... Oh and if you're felling ambitions , try "the history of Manned Spaceflight" & "The Rocket" both by Dr David Baker - possible the most through overviews of launch vehicle design , and operations ever written
|
|
|
|
Post by Tanalia on Nov 18, 2005 5:00:18 GMT -4
This was going to be my closing argument in the Great Moon Man Debate but I will make it now. At lift-off from the Moon, the Apollo 17 Ascent Stage weighed 10,997 pounds, including about 240 pounds of rock and soil samples About half (5261 pounds) of the total weight was propellant. www.hq.nasa.gov/office/pao/History/alsj/apollo.engin.htmlThis weight might not include the weight of the two astronauts so we may need to add another 320 pounds or so. Therefore, they needed 5261 pounds of chemicals mixed in order to lift off or NASA would not have added so much propellant, as weight was an issue in every facet of the mission. Clearly this amount of chemicals was not mixed and added to the engine in 2, 3 or 5 seconds. We would need the diameter specs on the pipes or hoses to prove it was not possible to add this much propellant this quickly. We would also need the specs on the pump or other device that delivered the propellant. Like many of the other issues I've cited I bet these specs are not available. Clearly the wee flame we see is not from 5261 pounds of chemicals igniting. As gwiz, just pointed out, it's not all burned at once, any more than you use up a tankful of gas driving a car for a few seconds. The ascent and descent modules are connected by explosive bolts, which are pretty much just what they sound like - bolts with explosives so they can be destroyed by throwing a switch. Many parts of the craft had these, details at www.hq.nasa.gov/office/pao/History/alsj/tnD7141ApPyrotchnc.pdfThis: www.hq.nasa.gov/alsj/a17/a17.trvlm3.htmlis the wrong place to look, that is just returning to the LM after their 3rd excursion. From www.hq.nasa.gov/alsj/a17/a17j.htmlyou want the 'Return to Orbit' section, www.hq.nasa.gov/alsj/a17/a17.launch.html, where you can find:
187:59:44 Cernan: Okay, Master Arm is On. I've got two good lights.
[These lights indicate that the explosive bolts which they will fire to separate the Ascent Stage from the Descent Stage are ready to fire.]
The actual detonation was triggered along with the engine ignition, there would be no need to comment on it unless it failed, which would be rather obvious anyway... |
|
