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Post by scooter on Nov 16, 2005 20:53:30 GMT -4
I'm reading them. Look what I just found. As you know, Armstrong had less then 30 seconds of fuel left before landing. The audio clip of his landing evidences this. Read this link at 113:01:15 and it says he had 50 seconds of fuel left. www.hq.nasa.gov/alsj/a17/a17.landing.htmlAlso, neil was on the surface of the moon for for at least 5 seconds before shutting the engine down, and despite the engine thrusting 3000 pounds of thust there is no crater. I believe the lower number reflects time to an abort call. (low fuel, abort back to the CSM). The higher number was the actual fuel remaining...I'll take a romp to, again, my fav link and check the consumables section in the Mission Report... Gene Krantz, when talking about the landing, said that, when he heard Aldrin's "picking up some dust" call, knew full well that, whatever the controllers said or did, this crew was going for the landing. The long trajectory, the rocky landing site they had to fly past, it was quite a tense time. There was hard ground/dirt under the dust, very hard to penetrate with the core sample tube. The widely expanded exhaust plume could not have dug a crater in this ground. Jay has a whole discussion of it on his Clavius site. There was some discoloration, but no crater, just blowing surface dust. It's like putting the hose attachment on your hose on a wider pattern vs a straight stream....it's all about nozzle expansion pattern. Vaccuum makes for "overexpansion" of the plume from the nozzle. Good reading, Dave
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Post by Moon Man on Nov 16, 2005 21:07:39 GMT -4
Apparently it started out at 10,000 pounds of thrust and as the fuel was burnt and the lander became lighter the thrust was reduced to 3000 pounds.
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Post by scooter on Nov 16, 2005 22:00:15 GMT -4
From the Apollo 11 mission report...
Descent stage fuel load at launch: 6975lbs, oxidizer 11209lbs, total 18184lbs Consumed fuel 6724lbs, oxidizer 10690 total 17414lbs
Also, a timeline was shown indicating engine firing time remaining...the low fuel light came on at 116 sec remaining, engine cutoff was at 45 seconds remaining, landing go/no-go decision point (abort) was at 20 seconds (25 seconds after they landed), then the fuel depletion point 20 seconds after that. They has a little cushion there, but not much.
Batteries...at ascent stage liftoff, the descent batteries has used 1055 amp/hours of a 1600 amp/hr capacity. At ascent stage jettison, 336 of the 592 amp/hrs had been consumed. It was a short mission for the LM, thus the ample power reserves that went unused.
Due to the overflight of the bad landing site, and the general downrange error of the landing trajectory, Mike Collins never did get a visual sighting of the lander. It would be cool if a future orbiter could get some shots, I'd love to see the boulder strewn crater thay flew over...
Dave
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Post by Data Cable on Nov 17, 2005 1:10:51 GMT -4
Trying to keep this on the topic of thermodynamics... It was also mentioned that they dump their human waste in space and it froze. As others have pointed out, repeatedly, water in a vacuum does not freeze or boil because "space" is cold or hot. I posted this link in the debate thread. Have you read it? Would a glass of water in space freeze or boil?Yes, an object in space will be heated if the sun's rays are absorbed by that object and converted to energy (heat), not because the empty space around it is "hot."
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Post by PhantomWolf on Nov 17, 2005 2:18:26 GMT -4
Also, neil was on the surface of the moon for for at least 5 seconds before shutting the engine down, and despite the engine thrusting 3000 pounds of thust there is no crater.
Actually there were only 3 secs between Buzz calling contact and Armstrong calling engine shutdown. The contact light come on when the landing probes hit and they were 5'7" feet long, so they still had to drop five and half feet in that 3 secs. I'll note here that both Neil and Buzz commented on the lack of crater.
From ALSJ
102:45:40 Aldrin: Contact Light. [The probes hanging from three of the footpads have touched the surface. Each of them is 67 inches (1.73 meters) long. The ladder strut doesn't have a probe.] [Aldrin - "We asked that they take it off."]
[Journal Contributor Harald Kucharek notes that Apollo 11 photo S69-32396, taken on 4 April 1969, shows Eagle with a probe attached to the plus-Z footpad. This indicates that the probe was removed after that date. The probe attachment is highlighted in a detail.]
[Apollo 11 photograph AS11-40-5921 shows the area under the Descent Stage. A gouge mark made by the probe hanging down from the minus-Y (south) footpad is directly under the engine bell, a graphic demonstration that the spacecraft was drifitng left during the final seconds.]
[Armstrong, from the 1969 Technical Debrief - "We continued to touchdown with a slight left translation. I couldn't precisely determine (the moment of) touchdown. Buzz called lunar contact, but I never saw the lunar contact lights."]
[Aldrin, from the 1969 Technical Debrief - "I called contact light."]
[Armstrong, from the 1969 Technical Debrief - "I'm sure you did, but I didn't hear it, nor did I see it."]
102:45:43 Armstrong (on-board): Shutdown 102:45:44 Aldrin: Okay. Engine Stop.
[Neil had planned to shut the engine down when the contact light came on, but didn't manage to do it.] [Armstrong, from the 1969 Technical Debrief - "I heard Buzz say something about contact, and I was spring-loaded to the stop engine position, but I really don't know...whether the engine-off signal was before (footpad) contact. In any event, the engine shutdown was not very high above the surface."]
[Armstrong - "We actually had the engine running until touchdown. Not that that was intended, necessarily. It was a very gentle touchdown. It was hard to tell when we were on."]
[Aldrin - "You wouldn't describe it as 'rock' (as in, 'dropping like a rock'). It was a sensation of settling."]
[Some of the other crews shut down 'in the air' (meaning 'prior to touchdown') and had a noticeable bump when they hit.]
[Aldrin - (Joking) "Well, they didn't want to jump so far to the ladder."]
[Readers should note that, although the Moon has no atmosphere, many of the astronauts used expression like 'in the air' to mean 'off the ground' and, after some thought, I have decided to follow their usage.]
[Armstrong, from the 1969 Technical Debrief - "The touchdown itself was relatively smooth; there was no tendency toward tipping over that I could feel. It just settled down like a helicopter on the ground, and landed."]
[On a final note about engine shutdown, Ken Glover calls attention to the following from an interview done with Neil on 19 September 2001 by historians Stephen Ambrose and Douglas Brinkley at NASA Johnson.]
[Brinkley: "Was there anything about your Moon walk and collecting of rocks and the like that surprised you at that time when you were on the Moon, like, 'I did not expect to encounter this,' or, 'I did not expect it to look like this'? Or included in that, the view of the rest of space from the Moon must have been quite an awesome thing to experience."]
[Armstrong: "I was surprised by a number of things, and I'm not sure (I can) recall them all now. I was surprised by the apparent closeness of the horizon. I was surprised by the trajectory of dust that you kicked up with your boot, and I was surprised that even though logic would have told me that there shouldn't be any, there was no dust when you kicked. You never had a cloud of dust there. That's a product of having an atmosphere, and when you don't have an atmosphere, you don't have any clouds of dust."]
["I was absolutely dumbfounded when I shut the rocket engine off and the particles that were going out radially from the bottom of the engine fell all the way out over the horizon, and when I shut the engine off, they just raced out over the horizon and instantaneously disappeared, you know, just like it had been shut off for a week. That was remarkable. I'd never seen that. I'd never seen anything like that. And logic says, yes, that's the way it ought to be there, but I hadn't thought about it and I was surprised."]
......
109:26:16 Armstrong: Okay. The descent engine did not leave a crater of any size. It has about 1 foot clearance on the ground. We're essentially on a very level place here. I can see some evidence of rays emanating from the descent engine, but a very insignificant amount.
.....
109:45:45 Armstrong: You're standing on a rock, a big rock there now. (Long Pause)
109:46:01 Aldrin: This pad sure didn't (garbled).
109:46:05 Armstrong: No. It didn't.
109:46:08 Aldrin: There's absolutely no crater there at all from the engine.
109:46:10 Armstrong: Nope.
109:46:12 Aldrin: I wonder if (garbled) right under the engine is where the probe might have hit. (Garbled) like that.
109:46:25 Armstrong: Yeah, I think that's a good representation of our sideways velocity at touchdown there: that hole that the probe...
109:46:30 Aldrin: I see that probe over on the minus-Y (south) strut (garbled) broken off and bent back up.
109:46:40 Armstrong: It did, didn't it? The other two both bent over. (Long Pause)
-------------
Also during the post-EVA rest time, Neil sort of jury-jigged himself over the engine cover, while Buzz curled up behind the engine cover, though neither got much if any sleep by their own admission. They made the recommedation of the hammocks used in later missions.
from ALSJ
[At 115.50, Public Affairs reports that the Surgeon doesn't believe that Neil is closer to sleep than "dozing". Buzz is not being monitored. In orbit, Collins is sound asleep. At 119.50, Public Affairs reports that Neil has not been sleeping. His heart rate occasionally drops into the 50s - the "sleep range" - but does not stay low.]
[Armstrong - "We had one pump..."]
[Aldrin - "I don't remember being troubled too much by the noise."]
[Armstrong - "I think it was my position (that) was bothered by the noise more than yours, because you were on the floor - right? - and I was on the engine cover with a loop that'd I rigged up of some kind to hold my legs, hanging from something up there. And my head was back to the rear of the cabin and there was a glycol pump or a water pump or something very close to where my head was. But the temperature control was probably the most troublesome."]
[Armstrong - "Yeah, I suspended them. I rigged up a loop to hold my legs. And the other thing was (that) the Earth was coming through the AOT (Alignment Optical Telescope). (Chuckling) We had blinds over the windows and so on, but the Earth was coming through the AOT. We were all settled down and we realized that we still had a light source coming from something. We rigged up something to hang something over the top of the AOT to cut that out."]
[The accompanying photo by Stacey O'Brien shows her husband, Journal Contributor Frank O'Brien, lying on the floor of a LM simulator on display at the Cradle of Aviation Museum.]
[Aldrin - "We tried it with the helmets off, at first, but that didn't...We thought we might, somehow, be warmer with the helmets on and we probably ended up that way."]
[Armstrong - "I don't remember a pressure point problem."]
[Aldrin - "If there was, you'd move some way to avoid it."]
[Armstrong - "(The quality of the rest) was poor in my case."]
[Aldrin - "I'd say the same thing."]
[Armstrong - "And for a lot of physical reasons that I mention (in the tech debrief, see below); and also, I'm sure, just the (problem of) getting unwound from the excitement of that day was contributing, too."]
[Aldrin - "I guess I may have mentioned it before but, maybe again, it seems almost inconceivable that you can't afford to monitor two people. It seems a little hokey for a nation to be sending people to the Moon..."]
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Post by Moon Man on Nov 17, 2005 3:19:45 GMT -4
Is there anyone who can confirm the actual temperature 3000 lbs of thrust created..?
Data, I didnot read the link earlier but I did this time. So much too read and so little time. Thanks for posting it.
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Post by Data Cable on Nov 17, 2005 3:29:48 GMT -4
Is there anyone who can confirm the actual temperature 3000 lbs of thrust created..? Temperature cannot be calculated from thrust. Is there anything you don't understand about it?
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Post by PhantomWolf on Nov 17, 2005 4:41:21 GMT -4
Is there anyone who can confirm the actual temperature 3000 lbs of thrust created..?
While I don't have the figures in front of me, it's possible to work it out using a derivative Ideal Gas Equation;
P1V1/T1 = P2V2/T2
where:
P1 = Pressure in chamber V1 = Volume in chamber T1 = Temperature in Chamber P2 = Pressure at Surface V2 = Volume at Surface T2 = Temperature at Surface
While you might not be able to see it due to having trouble with Maths equations, as the pressure of the column lowers and the volume expands, the Temperature drops. I'd suspect, though without figures I can't prove, that by the time it hit the surface it was no more than a few hundred degrees.
For example if we assume that the Volume merely doubles and the Pressure halves (I suspect that this is low side for the real event) then what we see is that an assumed temperature of 2000°C in the chamber would drop to 500°C outside of it. Again, these figures aren't supposed to be correct, I'm merely using them to show how with just small changes in volume and pressure that the exhuast can rapidly lose its temperature.
edited to add: Heh, serves me right for not reading the question properly, I was assuming that he wanted to know how hot the 3,000 pounds of thrust was. How much heat it creates is a nonsence question because thrust doesn't create heat. You can have compressed air producing 3,000 pounds of thrust at room temperature. However I'm leaving my response above as an answer to the temperture of the thrust plume (which is what I thought was asked, lol.)
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Post by PhantomWolf on Nov 17, 2005 4:51:48 GMT -4
By the way. Today I was with a group, most of who left school around year 11 (at 16) and none of whom have had any formal training in physics, in fact one of them asked me what physics was. They did however cotton on to the idea that a vaccum can't have a temperature in about 30 seconds. While originally they almost all considered that space should be cold, when it was pointed out to them that temperature is purely a property of matter, they all answered that in that case a vaccum could not have a temperature.
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Post by Moon Man on Nov 17, 2005 4:53:32 GMT -4
Is there anyone who can confirm the actual temperature 3000 lbs of thrust created..? Temperature cannot be calculated from thrust. Is there anything you don't understand about it? I understand the premise when I read it but if you asked me to explain it to you I couldn't do it yet without reading it again. I'm soaking up way too much information lately. I'm learning and understanding some of this science but admit not everything registers as of yet. Thanks for posting it though. You know what I love about this board..? People from all countries post here around the clock. You know what I hate about this board..? People from all countries post here around the clock. It keeps me up at night...Ha!
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Post by Moon Man on Nov 17, 2005 4:57:42 GMT -4
By the way. Today I was with a group, most of who left school around year 11 (at 16) and none of whom have had any formal training in physics, in fact one of them asked me what physics was. They did however cotton on to the idea that a vaccum can't have a temperature in about 30 seconds. While originally they almost all considered that space should be cold, when it was pointed out to them that temperature is purely a property of matter, they all answered that in that case a vaccum could not have a temperature. Thanks for posting that and making me feel dumb..Ha! Thank you for posting the temps in regards to 3000 lbs of thrust. Can you tell me what you think the temp would be with respect to 10,000 pounds of thrust..?
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Post by PhantomWolf on Nov 17, 2005 5:38:50 GMT -4
Thanks for posting that and making me feel dumb..Ha!It wasn't supposed to make you feel dumb, just show that it's not a hard concept to get if you are willing to accept even though you might not fully understand it. The temperatrure of a vaccum is in the same bin as the colour of a vaccum. Thank you for posting the temps in regards to 3000 lbs of thrust. Can you tell me what you think the temp would be with respect to 10,000 pounds of thrust..?I wouldn't expect that the gas in the chamber any different in temperature at 10,000 pounds to when it is at 3,000. The fuel still has the same combustion temperature and that's the main determining factor. About all I'd expect is that the plume outside the engine would likely cool slightly slower because with the greater thrust and thus material, I'd expect the plume to disapate slower and so the pressure to remain higher for a longer period.
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Post by sts60 on Nov 17, 2005 9:45:25 GMT -4
I'd imagine that the combustion chamber temperature might increase somewhat, though, due to the greater heat produced by the greater reaction rate.
MM, just to echo what PW said, you can get thrust from a rocket without any heat at all, such as from cold-gas thrusters. It's all just stuff under pressure being directed out a nozzle, and you can see it not only in certain space applications but also on the ground - letting go a balloon, a toy water rocket, or more dangerously a cylinder of compressed gas which is dropped, breaking the valve.
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Post by Jason Thompson on Nov 17, 2005 10:04:28 GMT -4
a cylinder of compressed gas which is dropped, breaking the valve
I worked with a guy who saw this happen once. The cylinder of nitrogen was dropped off the back of the delivery truck. The valve broke off, and apparently the cylinder itself was eventually found in a field two miles away!
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Post by sts60 on Nov 17, 2005 11:54:47 GMT -4
Consider also a cold gas in a sealed container which is heated up. This has become a very real hazard for firefighters at car fires, since gas struts are used more than ever in cars. Good old PV = nRT at work again; when T goes up greatly due to the fire, so does the pressure in the strut cylinder, and they fail all too often. One FF had a hood strut rocket off right through his leg at a car fire (he recovered).
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