Joined: May 2005 Gender: Male Posts: 4,620 Location: Lost Deimos Moonbase
Re: Playdor shows off his lack of scientific knowl « Reply #1320 on Jan 29, 2012, 3:57pm »
I'm not overly sure that banning was the correct choice, however it sort of amazes me that even to the end, playdor could not concieve that his arguement was so badly wrong that destroying it point by point was, well pointless. When he clearly could not understand the difference between Force, Pressure, and Velocity, well no amount of explaination is going to help him.
It must be fun to lead a life completely unburdened by reality. -- JayUtah
"On two occasions, I have been asked, 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?' I am not able to rightly apprehend the kind of confusion of ideas that could provoke such a question." -- Charles Babbage (1791-1871)
When he clearly could not understand the difference between Force, Pressure, and Velocity, well no amount of explaination is going to help him.
Not understanding the simplest scientific concepts was bad enough (how frakking hard is it to understand f=ma???) but when numerous people tried to teach him and guide him to the proper science he completely ignored it. Good riddance.
I blame the Internet. Some people are so stupid they think if they are smart enough to operate a browser then they are smart enough to understand all the information displayed on that browser.
"Show us a photo of either the descent or the ascent rockets firing and the exhaust plume. And exactly how does a space craft fly when "The engine is NOT ON"" -Stelios at the DIF Google search this site
Joined: May 2005 Gender: Male Posts: 3,072 Location: Dayton, Ohio
Re: Playdor shows off his lack of scientific knowl « Reply #1322 on Jan 29, 2012, 5:34pm »
I know Playdor is history and will never respond to any of this, but for the record I’d like to count the ways he was wrong.
Quote:
If the lem descent rocket engine exhaust plume expands out by 22 degrees. Plume would be expanded to a diameter of 35 feet, 40 feet past the end of rocket nozzle. A 35 foot diameter circle has an area of 962 square feet
Incorrect. According to the Apollo Spacecraft News Reference prepared by Grumman, the nozzle exit diameter was 63 inches. Expanding at a half-cone angle of 22 degrees would produce a diameter of 37.57 feet at a distance of 40 feet. A 37.57-feet diameter circle has an area of 1,109 square feet.
Furthermore, “lem” is incorrect. It’s LM.
Quote:
At 2 feet from the nozzle the exhaust plume would expand to a diameter of 4.6 feet, a circle having 16.6 square foot surface area.
Incorrect. Expanding at the same a half-cone angle of 22 degrees, the diameter 2 feet from the nozzle exit would be 6.87 feet, which gives an area of 37.1 square feet.
Quote:
FORCE applied to this 16.6 square foot area would be 962 square feet / 16.6 square feet or a (FORCE X 58)
Although the above math is correct, the numbers are wrong. The correct ratio is 1109 / 37.1 = 30.
Quote:
(FORCE X 58) being applied to the 16.6 square foot area compared to lem moving regolith at 40 feet with (FORCE X 1)
Regolith is the layer of material covering the solid bedrock, and is composed of dust, soil, broken rock and other related material. At 40 feet the exhaust stream moved only some of the powdery surface dust. To say “regolith” was moved is misleading.
Quote:
Note-> if exhaust expansion is 30 degrees as someone posted, then at 40 feet, diameter = 49 feet, having surface area of 1885 feet square. FORCE applied to area 2 feet from nozzle (22.9 square foot area) would be 1885 square feet / 22.9 square feet or (FORCE X 82)
Incorrect. At 40 feet the diameter is 51.44 feet and the area 2,078 square feet. At two feet the diameter is 7.56 feet and the area 44.9 square feet. The ratio is 2078 / 44.9 = 46.
Quote:
Note-> At 40 feet EAGLE was descending so rocket engine had to be throttled back more then when landing so the FORCE applied must actually be even higher then stated.
Incorrect. As long as the rate of descent is constant, the thrust must be equal to the weight of the LM. The weight of the LM at 40 feet was greater than at landing due to a larger fuel load. Therefore, the thrust needed to maintain a constant rate of decent at 40 feet is more than the thrust needed to hover just a few feet above the surface.
An increase in thrust is needed only when the rate of descent is decreased, and this would be only a momentary increase. Returning to a constant rate of decent requires the engine to be throttled back to a thrust equal to the LM’s weight.
Quote:
lem uses 18,000 pounds of thrust
Incorrect. The maximum thrust of the engine was about 10,000 lbf.
Quote:
to land the 18,000 pound lem
Incorrect. The mass of Eagle at lunar landing was 16,153.2 lbm. Its weight in lunar gravity was only about 2,674 lbf.
Quote:
at two feet that is 18,000 pounds / 16.6 square feet = 1084 pounds pressure per sq foot from the 1191 degree F supersonic exhaust stream. (post #126 - 1191 degree F)
Although the division is correct, the numbers are not. Simply correcting the numbers gives 2674 lbf / 37.1 sq.ft. = 72 psf. However, it is incorrect to assume the pressure is equal to the thrust divided by the contact area. Dynamic pressure, q, is equal to ρv2/2, where ρ is the gas density and v is the velocity.
In round numbers, the mass ejection rate of the LM’s engine at landing was about 4 kg/s and the exhaust velocity was about 3,000 m/s. If the contact area is 3.45 m2 (37.1 ft2), then the volume of gas impacting this area each second is 3.45 x 3000 = 10,350 m3. Therefore, the gas density is 4 / 10350 = 0.00039 kg/m3. Calculating the dynamic pressure we have,
q = 0.00039 x 30002 / 2 = 1,755 pascals (37 psf)
Quote:
if you are inclined to adjust for gravity, you would also have to adjust the weight of the regolith by 1/6 in moons gravity. 3,000 pounds of thrust / 16.6 square feet =181 pounds of thrust per square foot. So 181 pounds per sq foot pressure would be applied to regolith adjusted to 1/6 weight.
Incorrect. See response above.
Quote:
because of the impingement of the 1191 F supersonic exhaust by the surface of the moon, the truer value for the pounds of pressure is significantly higher then stated.
Incorrect. See response above.
Furthermore, 1191o F was an estimate of the gas temperature at the nozzle exit, not at the lunar surface.
Quote:
point is that this is enormous pressure.
“Enormous” is a rather subjective term. 37 psf is the same dynamic pressure as produced by a 120 mph wind at sea level on Earth. I’ve heard of hurricane force winds picking up some sand, but soil erosion on a large scale is really not a characteristic of short duration winds of this strength.
Quote:
Ralph Rene was absolutely correct, the PRESSURE from the leaf blower just needed to be defined. it is 181 pounds per square foot applied to regolith weighing 1/6 of what it would on earth. or 1084 pounds per square foot on earth.
1084 pounds of pressure would move boulders across a desert floor, as stated by Bill Kaysing.
I still don’t understand the point of bringing up Rene and Kaysing in this context if not to claim that the engine exhaust should have formed a crater. If playdor’s intention was otherwise, then I don’t know where he was headed with this discussion.
Quote:
at 2 feet the FORCE of the gas is now 58 times stronger and carries with it the FORCE of a gas moving at 580 mph
how big of a crater do you think it would make?
Proof that playdor was referring to crater formation despite his later backpedaling.
Quote:
the EAGLE could not have actually landed with the rocket engine running because of this back pressure.
A quantitative and quantified argument is required for further comment.
Yes, I have heard of back pressure. However, you're the first person who has suggested that it is insurmountable.
How does a Harrier land, if it cannot be manipulated so that the weight of the vehicle exceeds any upward force?
As playdor wont be answering your question, here's my shot at it.
Basically, when a jet strikes a surface, it flows radially outward along the surface. This is what happens with the single nozzle of the LM, and it doesn't create significant back-pressure. In an atmosphere, the outflow actually induces a flow in the air between itself and the aircraft that sucks the aircraft down.
The four nozzles of the Harrier are a bit different, since in the region between the nozzles, the outflows from the individual nozzles are inflows from the point of view of the aircraft. This means that the flows converge and form a rising plume or fountain from the centre. This impinges on the underside of the aircraft, so there is a back-pressure that pushes the aircraft up. This is actually a valuable feature for countering the suck-down effect and braking the descent. http://on-target-aviation.com/Assetts/images/Harrier_HOVER%20DIAGRAM%20CAG.jpg The later variants of the Harrier had vanes on the undersurface to contain the plume and add to the effect. http://lh5.ggpht.com/_cTaLGgz4Ru8/SFC_X7x1ClI/AAAAAAAAGCk/3CTZYMOrU3g/AV8B.jpg
Well, I understand basically how it works. But playdor (perhaps in an effort to say, "I'm not talking about craters! Honestly, I'm not!") seemed to be suggesting that you simiply couldn't get down. That if the LM was exerting a force, any force, downwards, the "back pressure" would keep it away from the surface, and the only way to land would be to cut the force entirely.
In his thought-experiment with the hose, he didn't seem to recognize that you can put the nozzle of the hose right against the surface of the wall, if the water pressure is low enough. Or, if you're landing the LM, you throttle back the force until it no longer compensates for the effect of gravity.
PErhaps I misunderstood his point, but I was trying to get him to explain further how "backpressure" eliminated any possible landing using downward force.
In his thought-experiment with the hose, he didn't seem to recognize that you can put the nozzle of the hose right against the surface of the wall, if the water pressure is low enough. Or, if you're landing the LM, you throttle back the force until it no longer compensates for the effect of gravity.
PErhaps I misunderstood his point, but I was trying to get him to explain further how "backpressure" eliminated any possible landing using downward force.
His basic problem with this was his grasping at straws as evidenced through reasoning by analogy. He didn't really grasp the physics involved and could not have told us any more. But we need to ask anyway, just in case.
I blame the Internet. Some people are so stupid they think if they are smart enough to operate a browser then they are smart enough to understand all the information displayed on that browser.
They go well beyond that -- they think they're smart enough to have proved wrong any information on that browser they don't happen to like for various ideological reasons.
What happened to all Playdors posts? they vanished.
I was reading the thread and all of a sudden there are only replies.
You're right. The thread is much shorter now too and the Playdor posts are missing from his JFK thread. It is possible for one to go back and delete all posts in the account one is logged in to. It is a pity to loose the original source for his hoax claims. It looks like we will have to rely on our quotes of his post.
Joined: May 2005 Gender: Male Posts: 3,122 Location: Space City, Texas
Re: Playdor's thread « Reply #1328 on Feb 2, 2012, 8:58am »
Looking at his account profile shows a last login date at Jan 29, 2012, 12:11am, the day he was banned. While it says he made 669 posts, there is no recent activity. A search of for posts by his name turns up no activity at all.
The very powerful and the very stupid have one thing in common: They don't alter their views to fit the facts, they alter the facts to fit their views." The Doctor, Doctor Who: The Face of Evil.
Joined: May 2005 Gender: Male Posts: 3,144 Location: Hamilton, Ontario
Re: Playdor's thread « Reply #1330 on Feb 2, 2012, 9:06am »
I'm not sure what's going on. According to the security logs only one post has been deleted since I banned Playdor, and it wasn't in this thread or the JFK thread. So even if Playdor managed to log in after I banned him, there would be a record of him deleting his posts.
I think it must be a glitch with the forum software. I'll send a message to Proboards Support about it.
"Earth diameter is 7,900 miles, and Moon diameter is 2,160 miles. It takes on average 90 minutes to complete one Earth orbit, so one Moon orbit should take roughly 25 minutes." - Sam "NasaScam" Colby
"you data is still open for interpretation, after all a NASA employee might of wipe a booger or dropped a hair on it" - showtime
Joined: May 2005 Gender: Male Posts: 3,144 Location: Hamilton, Ontario
Re: Playdor's thread « Reply #1333 on Feb 3, 2012, 1:32am »
Just so the conspiracy theorists out there know I didn't delete Playdor's posts, here's a screenshot of the forum logs with some explanations for some of the events (I blurred the IP addresses).
Re: Playdor's thread « Reply #1334 on Feb 3, 2012, 10:26am »
Weird and weird. Perhaps this wasn't a bug, perhaps it was an intentional attack? Playdor may have been an admitted incompetent (except dirt, he claimed he knew dirt) at all things related to Apollo, but maybe he was better at computer perversion?
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