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R.Wreck
SFN Regular
USA
1191 Posts |
 Posted - 10/10/2005 : 15:40:50 [Permalink]
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quote:
quote:
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Originally posted by breakballs
Don't say absurdities
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That grammar would have nailed it for me, even if I hadn't checked and found these two usernames posting from the same Italian ISP. What are the odds...?
Mama mia!! You mean breakballs is a puppet del calzino? |
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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filthy
SFN Die Hard
USA
14408 Posts |
Posted - 10/10/2005 : 15:50:56 [Permalink]
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quote:
Originally posted by breakballs
quote:
Originally posted by filthy
Coke and Pepsi. et al, are poisonous substances and are not to be found in my house. I used a can of beer, and yes, it was full (although I've yet to try it with a tallboy). It was done thus: I took a big, plastic funnel and sawed off the spout. Into this, I attached a short piece of 7/8 inch dowel. To that, I glued on a scrap of plywood. The can sat on the plywood with the funnel hanging down over my hand, held up by my finger tip. It worked nicely, and the reason I went through all this is to make sure I could do it before I put forth the idea. If it hadn't worked initally, I'd have simply added weight to the funnel rim until it did work.
The lander worked the same way, except in place of a funnel, it had gyroscopes and thrusters.
Do not sell, the science short. Many problems that look vastly complicated actually have quite simple solutions.
Try to balance it without the funnel.
Don't say absurdities
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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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sts60
Skeptic Friend
141 Posts |
Posted - 10/10/2005 : 15:58:19 [Permalink]
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Some truth here. It is an unstable system in need of control. That's why the lm had control thrusters.
Actually, the LM wasn't really unstable, not in sense of a basketball balanced on a fingertip, or an inherently unstable aircraft like the X-29. If a torque was applied, it would rotate, but so will any spacecraft (like the Space Shuttle, or a Soyuz or Shenzhou capsule, or the Apollo CM). That's why it had sensors, a control computer, a gimbaled descent stage engine, and, of course, attitude thrusters. |
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Jumbo
New Member
24 Posts |
Posted - 10/11/2005 : 06:00:56 [Permalink]
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Also its not the same as balancing a can on your finger. That aplies 1 force in 1 direction only and is relatively unstable.
The shape of the LM engine means that propellant didnt shoot out in 1 thin line but in a plume. This means that there are several forces acting in several directions the sum of which is generaly upwards. This means that as the LM pitches or rolls the force upwards doesnt drop off as quickly as in the coke can simulation making it more stable than the can.
Add in a relatively sophisticated control and guidance system and the type of pilot who can stick their jet into the 3 wire of a pitching and rolling carrier in a storm at night only seeing the deck in the final seconds and the LM becomes very very flyable. |
The mind is not a vessel to be filled but a fire to be lighted |
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filthy
SFN Die Hard
USA
14408 Posts |
Posted - 10/11/2005 : 07:04:45 [Permalink]
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quote:
Originally posted by Jumbo
Also its not the same as balancing a can on your finger. That aplies 1 force in 1 direction only and is relatively unstable.
The shape of the LM engine means that propellant didnt shoot out in 1 thin line but in a plume. This means that there are several forces acting in several directions the sum of which is generaly upwards. This means that as the LM pitches or rolls the force upwards doesnt drop off as quickly as in the coke can simulation making it more stable than the can.
Add in a relatively sophisticated control and guidance system and the type of pilot who can stick their jet into the 3 wire of a pitching and rolling carrier in a storm at night only seeing the deck in the final seconds and the LM becomes very very flyable.
In short, a well engineered funnel, writ large.
bbbb, me old sock, would you like to borrow my funnel? It's out in the shed, and I can go and get it if you'd like to be among the few, the proud, the brave that can balance a beer/coke can on his flippin' finger. The wooden parts are still on it and I don't need it anymore -- it's no longer of any use for funneling.
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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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Dr. Mabuse
Septic Fiend
Sweden
9691 Posts |
Posted - 10/11/2005 : 08:24:32 [Permalink]
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quote:
Originally posted by Jumbo
Also its not the same as balancing a can on your finger. That aplies 1 force in 1 direction only and is relatively unstable.
The shape of the LM engine means that propellant didnt shoot out in 1 thin line but in a plume. This means that there are several forces acting in several directions the sum of which is generaly upwards. This means that as the LM pitches or rolls the force upwards doesnt drop off as quickly as in the coke can simulation making it more stable than the can.
That's not really an accurate description.
Molecules in the plume may have different vectors, but all of them together is equal to one single large vector acting through the thruster.
And it is definitely not the reason why you can't compare the LM to balancing an item, basketball or coke-can on your finger.
If the thruster isn't aligned perfectly through the center of the LM's center of mass, there will be some torque, wanting to rotate the LM. This torque will be constant, since the thruster is attached to the LM.
In case of the coke-can or the basketball, as time goes and the can/ball tips, the mis-alignment of the "balancing" force will increase, which also means the torque will increase, and the rotating acceleration will increase until it hits the point of no return, and falls off the finger. Since the LM's torque is constant, there will always be time enough to fire one of the stabilisation thrusters to compensate for the torque. Or use the flight stick (or whatever control-means) to adjust the thruster's alignment.
Another problem with the analogy is that the torque produced by the LM's thruster is so much lower compared to the mass of the LM, that the rotational acceleration is very low. In the case of the coke-can, the torque produced by the vector offset is so great when compared to the can's mass that the rotational acceleration becomes unmanageable way too fast. It's easier to balance a broom-stick, because the alignment offset will always be so much smaller.
(Edit: some spelling fixes) |
Dr. Mabuse - "When the going gets tough, the tough get Duct-tape..."
Dr. Mabuse whisper.mp3
"Equivocation is not just a job, for a creationist it's a way of life..." Dr. Mabuse
Support American Troops in Iraq:
Send them unarmed civilians for target practice..
Collateralmurder. |
| Edited by - Dr. Mabuse on 10/11/2005 08:28:26 |
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furshur
SFN Regular
USA
1536 Posts |
Posted - 10/11/2005 : 09:06:52 [Permalink]
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quote:
I agree with bigbrain. I am a helicopter pilot.
A rocket can't land going backwards.
It can't use its rocket engine as a brake, it would wag its top and it would become uncontrollable.
Hey mr. helicopter pilot, then how is this movie possible???????
http://www.dfrc.nasa.gov/Gallery/Movie/LLRV/Small/EM-0019-01.mov
GOLLY!!!
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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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breakballs
Sockpuppet
53 Posts |
Posted - 10/11/2005 : 12:57:49 [Permalink]
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quote:
Originally posted by Dr. Mabuse
Since the LM's torque is constant, there will always be time enough to fire one of the stabilisation thrusters to compensate for the torque. Or use the flight stick (or whatever control-means) to adjust the thruster's alignment.
Helicopter is very difficult to fly but the thrust is at the top.
Put one rocket engine under your chair that can swing and try to stay vertical.
"there will always be time enough to fire one of the stabilisation thrusters to compensate for the torque".
No, there will be no time to avoid crash.
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THE BEST HELICOPTER PILOT IN THE WORLD |
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filthy
SFN Die Hard
USA
14408 Posts |
Posted - 10/11/2005 : 13:14:50 [Permalink]
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quote:
Originally posted by breakballs
quote:
Originally posted by Dr. Mabuse
Since the LM's torque is constant, there will always be time enough to fire one of the stabilisation thrusters to compensate for the torque. Or use the flight stick (or whatever control-means) to adjust the thruster's alignment.
Helicopter is very difficult to fly but the thrust is at the top.
Put one rocket engine under your chair that can swing and try to stay vertical.
"there will always be time enough to fire one of the stabilisation thrusters to compensate for the torque".
No, there will be no time to avoid crash.
On a slow decent in 1/6 earth gravity?
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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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furshur
SFN Regular
USA
1536 Posts |
Posted - 10/11/2005 : 13:56:57 [Permalink]
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quote:
Helicopter is very difficult to fly but the thrust is at the top.
Put one rocket engine under your chair that can swing and try to stay vertical.
"there will always be time enough to fire one of the stabilisation thrusters to compensate for the torque".
No, there will be no time to avoid crash.
BreakBalls you are a buffoon who is saying craps.
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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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Dr. Mabuse
Septic Fiend
Sweden
9691 Posts |
Posted - 10/11/2005 : 14:42:44 [Permalink]
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quote:
Originally posted by breakballs
quote:
Originally posted by Dr. Mabuse
Since the LM's torque is constant, there will always be time enough to fire one of the stabilisation thrusters to compensate for the torque. Or use the flight stick (or whatever control-means) to adjust the thruster's alignment.
Helicopter is very difficult to fly but the thrust is at the top.
It doesn't matter that the thrust is on top or bottom. It's the force of the thrust multiplied with the perpendicular distance of the thrust-vector to the center of mass that produce the torque that makes the object (helicopter or Lunar Module) rotate.
This torque is constant through time as the LM rotates. In the Coke-balancing-act the torque increases with time.
Both my examples are valid, and I will not concede to defeat of argument until you can mathematically prove that there will be no time to correct thruster misalignment.
quote:
Put one rocket engine under your chair that can swing and try to stay vertical.
The analogy is uncorrect because the proportions of the thrust compared to the torque-resistance of the mass, and the thust-vector-offset is not proportional to the LM.
Anyone but you understand that you can I can balance a broomstick on my finger. The proportions of mass, torque, and thrust-vector are closer.
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Dr. Mabuse - "When the going gets tough, the tough get Duct-tape..."
Dr. Mabuse whisper.mp3
"Equivocation is not just a job, for a creationist it's a way of life..." Dr. Mabuse
Support American Troops in Iraq:
Send them unarmed civilians for target practice..
Collateralmurder. |
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Starman
SFN Regular
Sweden
1613 Posts |
Posted - 10/11/2005 : 23:49:51 [Permalink]
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quote:
Originally posted by breakballs
Put one rocket engine under your chair that can swing and try to stay vertical.
Interesting experiment. Can I Add a gyro, a few control thrusters and a computer?quote:
"there will always be time enough to fire one of the stabilisation thrusters to compensate for the torque".
No, there will be no time to avoid crash.
Why?
Numbers please!
Your unsupported claims are worthless.
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breakballs
Sockpuppet
53 Posts |
Posted - 10/12/2005 : 03:26:30 [Permalink]
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quote:
Originally posted by Starman
quote:
Originally posted by breakballs
Put one rocket engine under your chair that can swing and try to stay vertical.
Interesting experiment. Can I Add a gyro, a few control thrusters and a computer?quote:
"there will always be time enough to fire one of the stabilisation thrusters to compensate for the torque".
No, there will be no time to avoid crash.
Why?
Numbers please!
Your unsupported claims are worthless.
Computers in 1969 were bigger than your living room. |
THE BEST HELICOPTER PILOT IN THE WORLD |
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filthy
SFN Die Hard
USA
14408 Posts |
Posted - 10/12/2005 : 03:49:30 [Permalink]
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quote:
Originally posted by breakballs
quote:
Originally posted by Starman
quote:
Originally posted by breakballs
Put one rocket engine under your chair that can swing and try to stay vertical.
Interesting experiment. Can I Add a gyro, a few control thrusters and a computer?quote:
"there will always be time enough to fire one of the stabilisation thrusters to compensate for the torque".
No, there will be no time to avoid crash.
Why?
Numbers please!
Your unsupported claims are worthless.
Computers in 1969 were bigger than your living room.
You don't bother to research anything, do you?
quote:
computers
The computer technology didn't exist in the 1960s to make the Apollo guidance computer.
This goes along with the general discussion about the state of technology available to NASA in the 1960s. But since computer capability has compounded many fold since Apollo, it is sometimes treated separately.
As with the general level of technology, conspracists often try to compare the availability and sophistication of consumer computing equipment with that available to NASA. Computer companies of the 1950s and 1960s had to produce general purpose computers at a cost that would attract business and scientific customers. NASA had to solve only one problem -- guidance -- and could easily afford to have a custom system designed and built for them using cutting edge components and techniques.
We could today, if we wanted, produce very fuel-efficient automobiles that would go for hundreds of thousands of miles without any regular service or mechanical breakdown. Unfortunately that car would cost well over a million dollars a unit, and would therefore be out of reach of most consumers. And so automobile companies produce vehicles more tailored to the economy of their intended customer. As a result the level of technology lags behind what would be achievable if money were no object.
The question to ask is not what kinds of computers were available in IBM's color brochures, but what kind of computer was available to NASA with its essentially bottomless pockets.
emphasis mine.
So all NASA needed was a one trick computer that would fit in a suitcase, not IBM's current top of the line. What they ended up with worked quite well, thank you.
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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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Starman
SFN Regular
Sweden
1613 Posts |
Posted - 10/12/2005 : 04:44:14 [Permalink]
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quote:
Originally posted by breakballsquote:
Originally posted by Starman
Numbers please!
Your unsupported claims are worthless.
Computers in 1969 were bigger than your living room.
Again, your unsupported claims are worthless.
The obviously false ones are pathetic.
Btw, why should the control system need an "advanced" computer? What kind of control function do you think we need?
Numbers please! |
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