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sts60
Skeptic Friend
141 Posts |
 Posted - 09/12/2005 : 14:34:16 [Permalink]
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It's not so simple to understand that a body at rest has different tolerance for imbalance than a body in motion.
I believe what you mean by this is that there's a different tolerance for imbalance for a body under acceleration than one under rest. Please correct me if I'm wrong.
The fact is, if the thrust is misaligned in a spacecraft, a certain angular acceleration will be imparted as long as the thrust continues to be misaligned to the center of mass. On a fairly massive vehicle like the LM, a small misalignment will only produce a small angular acceleration. Once the thrust stops, or is no longer misaligned, the angular velocity no longer increases.
Of course, the LM was built with a low center of gravity and was a pretty stable flying machine to begin with. It had two methods of correcting pitch and yaw rates: the gimballed descent motor and the RCS thrusters about the ascent stage. Both were controlled by the flight computer under the guidance of the pilot.
A pretty good discussion of the LM stability, including a very simple problem in rotational kinematics, can be found at
http://apollohoax.proboards21.com/index.cgi?board=theories&action=display&thread=1115413692&page=1. One poster kept saying the LM was unstable, etc. but failed to understand even the most basic physical concepts, despite repeated explanations, and ignored multiple detailed explanations of the LM systems; he was also incapable of solving the very simple problem posed by JayUtah. But you may find it instructive (not to mention... familiar). |
| Edited by - sts60 on 09/12/2005 14:36:26 |
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filthy
SFN Die Hard
USA
14408 Posts |
Posted - 09/12/2005 : 14:53:52 [Permalink]
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quote:
Try to balance on your forefinger a coke can.
I have already demonstrated how to do this -- were you not paying attention?
What nonsense!
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"What luck for rulers that men do not think." -- Adolf Hitler (1889 - 1945)
"If only we could impeach on the basis of criminal stupidity, 90% of the Rethuglicans and half of the Democrats would be thrown out of office." ~~ P.Z. Myres
"The default position of human nature is to punch the other guy in the face and take his stuff." ~~ Dude
Brother Boot Knife of Warm Humanitarianism,
and Crypto-Communist! 
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R.Wreck
SFN Regular
USA
1191 Posts |
Posted - 09/12/2005 : 14:59:33 [Permalink]
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quote:
Imagine to fly thrusted by your powerful farts. You would fall down in one second.
I did 3 seconds once. The secret is lots of beer, a super grande burrito, and a half dozen hard boiled eggs. Bigbrain, you are obviously part of the anti-flatulence-powered-flight conspiracy! And you are confuted! Again! |
The foundation of morality is to . . . give up pretending to believe that for which there is no evidence, and repeating unintelligible propositions about things beyond the possibliities of knowledge.
T. H. Huxley
The Cattle Prod of Enlightened Compassion
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furshur
SFN Regular
USA
1536 Posts |
Posted - 09/13/2005 : 05:09:52 [Permalink]
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BIGBRAIN I have supplied you with a video of a Neil Armstrong flying a craft that you say cannot fly. Why do you ignore that evidence and try to balance soda cans on your finger. Are you stupid or something?
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If I knew then what I know now then I would know more now than I know. |
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Valiant Dancer
Forum Goalie
USA
4826 Posts |
Posted - 09/13/2005 : 07:47:50 [Permalink]
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quote:
Originally posted by sts60
It's not so simple to understand that a body at rest has different tolerance for imbalance than a body in motion.
I believe what you mean by this is that there's a different tolerance for imbalance for a body under acceleration than one under rest. Please correct me if I'm wrong.
Nope. You're spot on here.
quote:
The fact is, if the thrust is misaligned in a spacecraft, a certain angular acceleration will be imparted as long as the thrust continues to be misaligned to the center of mass. On a fairly massive vehicle like the LM, a small misalignment will only produce a small angular acceleration. Once the thrust stops, or is no longer misaligned, the angular velocity no longer increases.
Of course, the LM was built with a low center of gravity and was a pretty stable flying machine to begin with. It had two methods of correcting pitch and yaw rates: the gimballed descent motor and the RCS thrusters about the ascent stage. Both were controlled by the flight computer under the guidance of the pilot.
A pretty good discussion of the LM stability, including a very simple problem in rotational kinematics, can be found at
http://apollohoax.proboards21.com/index.cgi?board=theories&action=display&thread=1115413692&page=1. One poster kept saying the LM was unstable, etc. but failed to understand even the most basic physical concepts, despite repeated explanations, and ignored multiple detailed explanations of the LM systems; he was also incapable of solving the very simple problem posed by JayUtah. But you may find it instructive (not to mention... familiar).
One question. What was the angular limits to the gimballed engine? Are we talking about 45 degrees from center or less? (That is from the center position how far in any direction could the gimballed engine rotate) I think I see yet another problem with bigdopes Coke can analogy. |
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ktesibios
SFN Regular
USA
505 Posts |
Posted - 09/13/2005 : 09:13:52 [Permalink]
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Well, according to http://apollo.spaceborn.dk/descent_engine.html the LM descent engine had these characteristics:
quote:
Technical Info
Full Thrust: 42976.6 N
Throttleable between: 4676.4 and 28058.4 N
Specific Impulse: 300 s
Propellants: Aerozine 50 and Nitrogen Tetroxide
Propellant Feed: (Super Critical) Helium Pressure Fed
Gimballed over: +/- 6 degrees in 2 axes
However, there's no need to look for yet more faults in bigmouth's coke can analogy. It's wrong for the simple reason that while the finger and coke can are in two independent inertial frames, a spacecraft and its engine are in a single frame. Therefore a comparison between the two situations is invalid from the beginning.
The problems of attitude control and the consequences of off-center thrust are exactly the same for any body in free fall, whether it be near the Esrth's surface, near the Moon's surface or halfway to Alpha Centauri. This has been explained to bigmouth over and over and over again, to no avail. He simply ignores any information which he does not want to hear, slags the messenger and repeats his phony talking point yet again. (Familiar behavior. I suppose we could take it as evidence that there are Republicans in Italy.)
Check out the Apollohoax thread sts60 referenced. You might enjoy taking a crack at the problem JayUtah posed for bigmouth's previous incarnation. It's on page 10. The answer is on page 12. It's a problem in high school level Newtonian physics- the kind even an iggerant uneddicated studio rat like me can work out.
Have fun, but bigmouth's craps need no further confutation. He's simply a troll with a very limited repertoire, which was exhausted long ago. |
"The Republican agenda is to turn the United States into a third-world shithole." -P.Z.Myers |
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bigbrain
BANNED
409 Posts |
Posted - 09/13/2005 : 12:45:33 [Permalink]
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---------------------------------------------------------------------
Originally posted by ktesibios
Technical Info
Full Thrust: 42976.6 N
Throttleable between: 4676.4 and 28058.4 N
Specific Impulse: 300 s
Propellants: Aerozine 50 and Nitrogen Tetroxide
Propellant Feed: (Super Critical) Helium Pressure Fed
Gimballed over: +/- 6 degrees in 2 axes ---------------------------------------------------------------------
Go here please
http://www.answers.com/topic/apollo-lunar-module
"The total mass of the module was 15,264 kg with the majority of that (10,334 kg) in the descent stage".
15,264 kg : 6 = 2,544 kg
If the rocket engine is "throttleable between: 4676.4 and 28058.4 N"
2,805 kg - 2,544 kg = 261 kg
The power of throttleable rocket engine is only about 10% bigger than the weight of Lunar Module.
If you go at http://www.flyingcirkus.com you will notice that power of airplanes' engine able to stay in hovering close to the ground is 50% - 75% bigger than the weight of airplanes...
...because you need big power to escape from dangerous situations.
A power 10% bigger than the weight of Lunar Module is ridiculous.
Also +/- 6 degrees in 2 axes is ridiculous.
Airplains able to stay in hovering close to the ground have mobile surfaces that can move 45 - 60 degrees
  
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"Obsequium amicos, veritas odium parit" (Flattery gets friends, truth hatred)
Publius Terentius Afer, "Terence", Roman dramatist
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Subjectmatter
Skeptic Friend
173 Posts |
Posted - 09/13/2005 : 13:16:54 [Permalink]
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When did the lunar model need to stay hovering over the ground?
Also: the mass of the module doesn't change just because it is on the moon. You are using the wrong units. |
Sibling Atom Bomb of Couteous Debate |
| Edited by - Subjectmatter on 09/13/2005 13:18:13 |
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Valiant Dancer
Forum Goalie
USA
4826 Posts |
Posted - 09/13/2005 : 13:52:29 [Permalink]
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quote:
Originally posted by bigbrain
---------------------------------------------------------------------
Originally posted by ktesibios
Technical Info
Full Thrust: 42976.6 N
Throttleable between: 4676.4 and 28058.4 N
Specific Impulse: 300 s
Propellants: Aerozine 50 and Nitrogen Tetroxide
Propellant Feed: (Super Critical) Helium Pressure Fed
Gimballed over: +/- 6 degrees in 2 axes ---------------------------------------------------------------------
Go here please
http://www.answers.com/topic/apollo-lunar-module
"The total mass of the module was 15,264 kg with the majority of that (10,334 kg) in the descent stage".
15,264 kg : 6 = 2,544 kg
If the rocket engine is "throttleable between: 4676.4 and 28058.4 N"
2,805 kg - 2,544 kg = 261 kg
The power of throttleable rocket engine is only about 10% bigger than the weight of Lunar Module.
If you go at http://www.flyingcirkus.com you will notice that power of airplanes' engine able to stay in hovering close to the ground is 50% - 75% bigger than the weight of airplanes...
...because you need big power to escape from dangerous situations.
A power 10% bigger than the weight of Lunar Module is ridiculous.
Also +/- 6 degrees in 2 axes is ridiculous.
Airplains able to stay in hovering close to the ground have mobile surfaces that can move 45 - 60 degrees
Bigdope, you are neglecting that the LM didn't ever hover. |
Cthulhu/Asmodeus when you're tired of voting for the lesser of two evils
Brother Cutlass of Reasoned Discussion |
| Edited by - Valiant Dancer on 09/13/2005 13:53:57 |
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Dry_vby
Skeptic Friend
Australia
249 Posts |
Posted - 09/13/2005 : 15:35:09 [Permalink]
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.....and we wait, dear reader, for the bigbrainwave tsunami to break over our logic once more.
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"I'll go along with the charade
Until I can think my way out.
I know it was all a big joke
Whatever it was about."
Bob Dylan
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ktesibios
SFN Regular
USA
505 Posts |
Posted - 09/13/2005 : 17:24:41 [Permalink]
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A thrust of 28058.4N will accelerate a mass of 15264kg at just about 1.838 m/s^2.
The mean acceleration of lunar gravity at the lunar surface is 1.622 m/s^2.
Therefore the LM descent engine had enough thrust to overcome the Moon's gravity and hover, or even ascend.
The full thrust of 42976.2N would provide an acceleration of about 2.816 m/s^2. Remember also that as the LM descended, it consumed fuel, reducing its mass. 8165 kg of the descent stage's mass was propellants. The descent was planned to land on the Moon with only about 306 kg of fuel remaining in the descent stage (see http://history.nasa.gov/alsj/nasa-tnd-6846pt.1.pdf). Apollo 11 cut it even closer than that; their remaining descent stage fuel was calculated at between 7 and 17 seconds worth after the landing ( see http://history.nasa.gov/SP-4223/ch11.htm ).
Once again, bigmouth has demonstrated that he doesn't know the difference between an airplane in Earth's atmosphere and a rocket in space and that he hasn't anything of substance to say, or indeed anything at all to say except puerile jeering.
But what can we expect from a mere troll who makes up his craps as he goes along?  |
"The Republican agenda is to turn the United States into a third-world shithole." -P.Z.Myers |
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calladus
New Member
2 Posts |
Posted - 09/13/2005 : 18:18:38 [Permalink]
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Does bigbrain believe that the current Space Shuttle works? How about the International Space Station? Satellites? Hubble Telescope?
I just want to know.
During the Apollo missions, Amateur Radio enthusiasts would use directional antenna to pick up transmissions from the spacecraft while they were in LUNAR ORBIT. Gee - point your directional antenna a little bit away, and you'll miss it!
What about those Amateur Radio enthusiasts who communicate with the Shuttle or the ISS using directional antenna? (I got to listen to STS-64 with a hand made directional antenna and a hand held radio - when I bumped the tripod, I lost the signal until I could get it reoriented again. Plus I had to keep adjusting it - it was too improvised for me to attempt a contact.
What about my Direct TV dish satellite antenna? If I mis-aim it, I lose my TV signal.
What, exactly, have I been aiming at all this time if it isn't a satellite? When I listen to a Shuttle mission, just who am I listening to?
Perhaps it's little green men?
- Calladus |
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Dry_vby
Skeptic Friend
Australia
249 Posts |
Posted - 09/13/2005 : 18:26:01 [Permalink]
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Hi calladus, and welcome.
These and many other questions have been asked of bigpain over a number of threads each containing a huge number of pages.
I doubt that you'll get an answer, and even if you do, it probably won't make sense.
Many have been chipping away at the stone that is bigpains ignorance, with no discernable effect.
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"I'll go along with the charade
Until I can think my way out.
I know it was all a big joke
Whatever it was about."
Bob Dylan
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filthy
SFN Die Hard
USA
14408 Posts |
Posted - 09/14/2005 : 02:09:45 [Permalink]
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Hey bigbrain, dig this:
THE JAXA BUFFOONS ARE GOING TO FAKE-LAND A PROBE ON AN ASTEROID!!!!
quote:
Japan's Probe Within 12 Miles of Asteroid
TOKYO (AP) - Bringing Japan's most complex space mission near its climax, a probe is within 12 miles of an asteroid almost 180 million miles from Earth in an unprecedented rendezvous designed to retrieve rocks from its surface.
The Hayabusa probe, launched in May 2003, will hover around the asteroid for about three months before making its brief landing to recover the samples in early November. The asteroid is located between Earth and Mars.
"The mission is going very smoothly and proceeding as planned," Atsushi Wako, a spokesman for JAXA, Japan's space agency, said Tuesday.
The asteroid, informally named Itokawa, after Hideo Itokawa, the father of rocket science in Japan, is only 2,300 feet long and 1,000 feet wide, and has a gravitational pull one-one-hundred-thousandth of Earth's.
I've no doubt that you easily can confute this swindle with the pictures the probe is alledgly sending back. Just draw some lines on them....
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"What luck for rulers that men do not think." -- Adolf Hitler (1889 - 1945)
"If only we could impeach on the basis of criminal stupidity, 90% of the Rethuglicans and half of the Democrats would be thrown out of office." ~~ P.Z. Myres
"The default position of human nature is to punch the other guy in the face and take his stuff." ~~ Dude
Brother Boot Knife of Warm Humanitarianism,
and Crypto-Communist!
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bigbrain
BANNED
409 Posts |
Posted - 09/14/2005 : 02:21:49 [Permalink]
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You would have land on the moon with a rocket that, instead of going forward, has gone backwards.
You would have come back from the moon with a capsule made of stell and aluminum alloys protected by a ridiculous plastic coating during the impact with atmosphere at 5,000 °F - 10,000 °F
Only children believe in Xmas pop.
You are gullible people.
You would have to read a book written by an Italian scientist, Silvio Ceccato, who has demonstrated that about all the news we can hear from radio, TV, magazines, newspapers, or talking with people in general, things stay this way:
1/3 of the news is false
1/3 of the news is true
1/3 is a huddle of false and true news
Reflect, think, consider, ponder on things.
How can you think to protect a capsule made of steel and aluminum alloys WITH A SMALL PLASTIC COATING in its friction with atmosphere in which temperature is 5,000 °F - 10,000 °F 
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"Obsequium amicos, veritas odium parit" (Flattery gets friends, truth hatred)
Publius Terentius Afer, "Terence", Roman dramatist
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