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JayUtah
2001-Nov-15, 03:07 PM
I'm told this month's Mensa publication contains these hoax-related questions allegedly asked by Mensans.

From one person:

1. The tremendous height of the Saturn V launch vehicle was attributed to the amount of fuel needed to escape Earth's gravity. Given the fact that the moon's gravity is 1/6th that of the Earth, you'd need something 1/6th the height of the Saturn V to blast off from the moon. So how did the Eagle lift off?

2. Once achieving escape velocity when leaving the Earth, the Apollo would need to lose 5/6th of its velocity in order to be captured by the moon's gravity and swing into orbit. The spacecraft is moving at a velocity that prevents the Earth's gravity from pulling it back down - so unless they "put on the brakes" they certainly aren't going to be captured by the moon's gravity. However, all three stages of the Saturn V had been dropped - only the LEM remained.

3. How do humans survive at the top of a rocket? The space shuttle is fairly well isolated from the heat of its boosters, but no so with Saturn and its command module. At launch they had to spray lots of water on the launch pad to keep the concrete from cracking. Metal is a great conductor of heat. What kept the astronauts cool? Did they have a zillion air conditioners in the command module?

And from a different person:

4. Since studies estimate that the walls of the Apollo craft would have to be between six to eight inches thick with lead, how did we manage to send our astronauts through the Van Allen radiation belts without them receiving lethal doses of radiation? The Apollo craft walls were merely millimeters thick.

ToSeek
2001-Nov-15, 03:20 PM
Isn't Mensa supposed to be an organization for smart people?

Kaptain K
2001-Nov-15, 03:28 PM
I.Q. is like the numbers on a measuring cup. The numbers show only the capacity. Also, quality is at least as important as quantity. A bucket full of mud is still full of mud.

ToSeek
2001-Nov-15, 03:33 PM
I'm sure I'm preaching to the choir here, but I have got to respond to some of this nonsense.



On 2001-11-15 10:07, JayUtah wrote:
I'm told this month's Mensa publication contains these hoax-related questions allegedly asked by Mensans.

From one person:

1. The tremendous height of the Saturn V launch vehicle was attributed to the amount of fuel needed to escape Earth's gravity. Given the fact that the moon's gravity is 1/6th that of the Earth, you'd need something 1/6th the height of the Saturn V to blast off from the moon. So how did the Eagle lift off?



This is a total non sequitur. The Saturn V is so big because it needs to send a huge amount of payload (its third stage and the command and lunar modules) to the moon. Even a rocket as small as a Delta is capable of giving its payload escape velocity.

The lunar module, on the other hand, only needs to deal with its upper stage and only needs to get that into lunar orbit, not out of lunar orbit.

ToSeek
2001-Nov-15, 03:36 PM
On 2001-11-15 10:07, JayUtah wrote:

2. Once achieving escape velocity when leaving the Earth, the Apollo would need to lose 5/6th of its velocity in order to be captured by the moon's gravity and swing into orbit. The spacecraft is moving at a velocity that prevents the Earth's gravity from pulling it back down - so unless they "put on the brakes" they certainly aren't going to be captured by the moon's gravity. However, all three stages of the Saturn V had been dropped - only the LEM remained.



First off, it's not true that only the LM (the correct acronym) remained: the command and service modules were along, too. Second, the spacecraft was significantly slowed down by earth's gravity since the force that sent it outward was only slightly more than the minimum needed to get it to the moon. Thus, the service module engine was quite capable of "putting on the brakes."

ToSeek
2001-Nov-15, 03:41 PM
On 2001-11-15 10:07, JayUtah wrote:

3. How do humans survive at the top of a rocket? The space shuttle is fairly well isolated from the heat of its boosters, but no so with Saturn and its command module. At launch they had to spray lots of water on the launch pad to keep the concrete from cracking. Metal is a great conductor of heat. What kept the astronauts cool? Did they have a zillion air conditioners in the command module?



By the same reasoning, a guy operating a blowtorch or a flamethrower has serious problems. Simply, the heat is being thrown out away from the spacecraft, not towards it.

I won't even bother to mention the millions of pounds of cryogenic liquids between the first stage engines and the spacecraft - I think the greater issue would be how to keep the astronauts warm under the circumstances, not cold.

JayUtah
2001-Nov-15, 03:46 PM
My membership in Mensa lasted less than one year, precisely because of the climate at the meetings. After a while it became apparent to me that these were people so stuck on their self-perception of intelligence in some areas that they were blinded to their ignorance in others. They'd go around confidently expounding utter nonsense just because they didn't want to admit ignorance of a pertinent fact.

What's the line from The Englishman Who Went Up A Hill And Came Down A Mountain? "We may be twp (i.e., stupid), but we're not so twp that we don't know we're twp."

Some of these people are precisely the type who can talk for three hours about hyperspatial manifolds and Grand Unification, and then go out and put oil in their car radiators.

SeanF
2001-Nov-15, 05:30 PM
Wasn't it an episode of Frasier where he took a date to a plane'arium*, but there was a group from Mensa there who kept asking the presenter questions to which the answer was "Uranus," ("Are any other planets similar in size and composition to Neptune?" "Yes, Neptune is similar in size and composition to Uranus.") and giggling like little kids?

*That's a planetarium, for those of you who don't watch South Park. Ever since seeing that particular episode, I simply cannot pronounce the "t" in that word!

ToSeek
2001-Nov-15, 05:43 PM
On 2001-11-15 12:30, SeanF wrote:
Wasn't it an episode of Frasier where he took a date to a plane'arium*, but there was a group from Mensa there who kept asking the presenter questions to which the answer was "Uranus," ("Are any other planets similar in size and composition to Neptune?" "Yes, Neptune is similar in size and composition to Uranus.") and giggling like little kids?



My wife was a Mensa member for a little while and took me to meetings, and that's about the sense of humor I remember encountering, except their favorite phrase was "joint meeting," which they accompanied with puffing on an imaginary, um, cigarette.

Hat Monster
2001-Nov-15, 07:40 PM
Okay, I'll just take this apart piece by piece and sell it on as the scrap it is.
(here's guessing this board supports UBB code)


1. The tremendous height of the Saturn V launch vehicle was attributed to the amount of fuel needed to escape Earth's gravity. Given the fact that the moon's gravity is 1/6th that of the Earth, you'd need something 1/6th the height of the Saturn V to blast off from the moon. So how did the Eagle lift off?

Bear in mind that one extra pound of weight means 40lb of fuel. More fuel is more weight.
Earth is bigger than the moon. Eagle had to reach Lunar Orbit. SaturnV had to reach Earth orbit (and cope with atmospheric drag) and also then ESCAPE from Earth orbit. Eagle did not.


2. Once achieving escape velocity when leaving the Earth, the Apollo would need to lose 5/6th of its velocity in order to be captured by the moon's gravity and swing into orbit. The spacecraft is moving at a velocity that prevents the Earth's gravity from pulling it back down - so unless they "put on the brakes" they certainly aren't going to be captured by the moon's gravity. However, all three stages of the Saturn V had been dropped - only the LEM remained.

LEM + Command Module + Service Module.
Recap basic Newtonian physics. You're making these up and claiming false authority.


3. How do humans survive at the top of a rocket? The space shuttle is fairly well isolated from the heat of its boosters, but no so with Saturn and its command module. At launch they had to spray lots of water on the launch pad to keep the concrete from cracking. Metal is a great conductor of heat. What kept the astronauts cool? Did they have a zillion air conditioners in the command module?

What metal? The half a foot of metal that wasn't even solid? And pray explain how the ceramic engine nozzles were going to conduct heat to the metal?

And from a different person:


4. Since studies estimate that the walls of the Apollo craft would have to be between six to eight inches thick with lead, how did we manage to send our astronauts through the Van Allen radiation belts without them receiving lethal doses of radiation? The Apollo craft walls were merely millimeters thick.

No studies indicated that. That's a lie. Like I said, this is all made up. The Van Allen belts are thickest at the poles. Apollo escaped pretty close to the equator for this reason. At the poles, they are also more energetic. At the equator, they're mainly beta particles and alpha particles. An inch of aluminium will stop all beta particles. A sheet of paper does the same to alpha particles. Apollo had not millimeters (how can a few mm of metal support it's own weight?) but inches. Like I say, this is all made up.

Wiley
2001-Nov-15, 08:10 PM
On 2001-11-15 14:40, Hat Monster wrote:
Bear in mind that one extra pound of weight means 40lb of fuel. More fuel is more weight.
Earth is bigger than the moon. Eagle had to reach Lunar Orbit. SaturnV had to reach Earth orbit (and cope with atmospheric drag) and also then ESCAPE from Earth orbit. Eagle did not.


I think the air resistance must be huge. A cyclist going 20 mph expends 90% of his or her energy overcoming are resistance. Of course cyclists don't have to overcome gravity (I refuse to cycle uphill) but I'd still wager that air resistance will be significant.

Mr. X
2001-Nov-15, 08:54 PM
My wife was a Mensa member for a little while and took me to meetings, and that's about the sense of humor I remember encountering, except their favorite phrase was "joint meeting," which they accompanied with puffing on an imaginary, um, cigarette.

A cigarette with certain select herbs inside, for flavour of course.

Oh my, I didn't know Mensa was so low-brow. This is even worse than those South Park Mensa-Uranus jokes.

I guess it's as someone said it's quantity not quality, to them a tanker of sewers liquid and that slime that drips below dumps is better than a glass of water. Their choice, I know which one I'd choose though.

Russ
2001-Nov-15, 10:12 PM
This list of question confirms my rather low opinion of Mensa. My one brush with them came when I lived in Chicago. The guy in the apartment across from mine was a member. When he found my IQ to be above their threshold he invited me to a meeting. My observation was, most of them would have had to get smarter to be blathering morons. About half were 10 pound of ego in a 5 pound bag and spent the evening trying to intelectually humilliate everyone else.

But other than that, I had a great time! I Didn't join.

JayUtah
2001-Nov-15, 10:26 PM
As I've mentioned elsewhere on this forum, Ralph Rene was a Mensan, before they kicked him out. Rene is one of the moon hoax "experts", having written a book where he smugly points out all the allegedly fatal flaws in the Apollo program. Mensa disowned him after he wrote a book in which he claimed, despite any relevant education on his part, that both Einstein and Newton were charlatan physicists.

Question 4 applies to Rene's major thesis, which is that the radiation in the Van Allen belts and beyond would have cooked the astronauts instantly.

Who was it who said, "I would never belong to an organization that would have me as a member"?

My favorite quote relating to Mensa comes from Will Rogers: "We're all ignorant. We're just ignorant about different things."

David Simmons
2001-Nov-15, 11:19 PM
On 2001-11-15 17:26, JayUtah wrote:

Who was it who said, "I would never belong to an organization that would have me as a member"?



Groucho Marx. But it was probably originated by one of his writers.

In the interest of completeness, the entire line (as given by a couple of Groucho Web Sites) was, "I sent the club a wire stating, 'Please accept my resignation.' I don't want to belong to any club that will accept me as a member."



<font size=-1>[ This Message was edited by: The Bad Astronomer on 2001-11-15 21:43 ]</font>

The Bad Astronomer
2001-Nov-16, 02:44 AM
David-- I edited the post a bit; it got bollixed up. I hope that's okay.

The Rat
2001-Nov-16, 03:19 AM
Mensa continues to prove Bailey's Second Law; There is no relationship between the three virtues of intelligence, education, and wisdom.

I have taken Mensa's tests and passed with flying colours, but see no reason to join. I've met Mensa members who couldn't change a fuse if their life depended on it.

Oh, by the way, my first law is;

Necessity may be the mother of invention, but laziness is usually the father.

Dave Bailey, aka The Rat

Simon
2001-Nov-16, 08:25 AM
The Van Allen belts are thickest at the poles. Apollo escaped pretty close to the equator for this reason. At the poles, they are also more energetic. At the equator, they're mainly beta particles and alpha particles.

Thickest at the poles? Are you sure? I don't know a whole lot about it, but all of the pictures I've seen of the Van Allen belts are, well, belts. As in, around the equator. And since they're held there and energized by the Earth's magnetic field, I would think that at the poles any energetic particles would spiral down and cause aurorae, though I'm not an expert on that either.



I think the air resistance must be huge. A cyclist going 20 mph expends 90% of his or her energy overcoming are resistance. Of course cyclists don't have to overcome gravity (I refuse to cycle uphill) but I'd still wager that air resistance will be significant.
I think a conical rocket made out of smooth metal is a bit more aerodynamic than a cyclist. And it would also get above most of the atmosphere pretty quickly, as in before the first stage seperated. So air resistance is still a factor, but it hardly uses up 90% of the energy.

James
2001-Nov-16, 11:30 AM
On 2001-11-15 22:19, The Rat wrote:

Oh, by the way, my first law is;

Necessity may be the mother of invention, but laziness is usually the father.

-The Rat

That's good, Rat. /phpBB/images/smiles/icon_smile.gif Mind if I take it? /phpBB/images/smiles/icon_confused.gif

The Rat
2001-Nov-16, 02:36 PM
On 2001-11-16 06:30, James wrote:


On 2001-11-15 22:19, The Rat wrote:

Oh, by the way, my first law is;

Necessity may be the mother of invention, but laziness is usually the father.

-The Rat

That's good, Rat. /phpBB/images/smiles/icon_smile.gif Mind if I take it? /phpBB/images/smiles/icon_confused.gif



Go ahead. Just call it 'Bailey's first law'

ToSeek
2001-Nov-16, 02:57 PM
On 2001-11-15 15:10, Wiley wrote:

I think the air resistance must be huge. A cyclist going 20 mph expends 90% of his or her energy overcoming are resistance. Of course cyclists don't have to overcome gravity (I refuse to cycle uphill) but I'd still wager that air resistance will be significant.


Actually, in the space systems class I'm taking now, the section on calculating velocity after launch doesn't even consider the effects of aerodynamic drag. All it says is that for most launches the attempt is to get above most of the atmosphere before doing most of the acceleration.

Wiley
2001-Nov-16, 04:58 PM
On 2001-11-16 09:57, ToSeek wrote:


On 2001-11-15 15:10, Wiley wrote:

I think the air resistance must be huge. A cyclist going 20 mph expends 90% of his or her energy overcoming are resistance. Of course cyclists don't have to overcome gravity (I refuse to cycle uphill) but I'd still wager that air resistance will be significant.


Actually, in the space systems class I'm taking now, the section on calculating velocity after launch doesn't even consider the effects of aerodynamic drag. All it says is that for most launches the attempt is to get above most of the atmosphere before doing most of the acceleration.


While in the atmosphere, what is the speed? If I recall correctly, aerodynamic drag is proportional to velocity cubed.

Also what level (sophmore, junior, grad) is the class? Air resistance is very hard to quantify, so in lower level classes, it's ignored.

Thanks,

Mnemonia
2001-Nov-16, 05:15 PM
1. The tremendous height of the Saturn V launch vehicle was attributed to the amount of fuel needed to escape Earth's gravity. Given the fact that the moon's gravity is 1/6th that of the Earth, you'd need something 1/6th the height of the Saturn V to blast off from the moon. So how did the Eagle lift off?


I'm willing to bet everything I own that the LMs are quite a bit less massive than 1/6th their fully fuel-loaded Saturn rockets, thus it takes less force to propel them into orbit, and thus less fuel. If the lander was 100 times less massive it would only take 1/100th as much fuel, and be approximately 1/100th in size just to leave Earth. (That is, were its engines powerful enough to do so.) One would think that it would require even less to liftoff from the Moon.




2. Once achieving escape velocity when leaving the Earth, the Apollo would need to lose 5/6th of its velocity in order to be captured by the moon's gravity and swing into orbit. The spacecraft is moving at a velocity that prevents the Earth's gravity from pulling it back down - so unless they "put on the brakes" they certainly aren't going to be captured by the moon's gravity. However, all three stages of the Saturn V had been dropped - only the LEM remained.


When you throw a baseball up, does it keep going? No, it SLOWS and falls back down. As the LM gets farther from Earth it slows down becuase gravity is trying to pull it back. A baseball has no brakes to make it fall back down and neither did the LM/Command/Service Module. It may have been going too fast to fall all the way back down anytime soon, but certainly enough to be slowed over such a great distance as that between the Earth and Moon. NASA simply calculkated what the correct deorbiting speed would need ot be to avoid shooting past the moon, not so difficult to put Sir Issac Newton in the drivers seat. (If you think about it this means the spacecrafts were at thier lowest velocity at the Lagrange point, and then sped up as the moons gravity pulled them more strongly than the Earth's. Thus the speed was not constant throughout the journey, and Mensa incorrectly assumes it is. Shame on them.)

Chip
2001-Nov-16, 06:09 PM
On 2001-11-15 18:19, David Simmons wrote:


On 2001-11-15 17:26, JayUtah wrote:

Who was it who said, "I would never belong to an organization that would have me as a member"?



Groucho Marx. But it was probably originated by one of his writers.

In the interest of completeness, the entire line (as given by a couple of Groucho Web Sites) was, "I sent the club a wire stating, 'Please accept my resignation.' I don't want to belong to any club that will accept me as a member."
<font size=-1>[ This Message was edited by: The Bad Astronomer on 2001-11-15 21:43 ]</font>


I was a member for a while too. Still am I guess. (Haven't gone to the meetings recently.) Not all "Mensans" are naive, but some will do until a naive person comes along.
BTW - the reason the Astronauts did not get overheated in the Apollo Command Module was because it wasn't hot in there, being positioned above the rocket engine rather than beneath it.

Thanks for quoting my favorite quote!
Chip /phpBB/images/smiles/icon_smile.gif

ToSeek
2001-Nov-16, 07:02 PM
On 2001-11-16 11:58, Wiley wrote:

Also what level (sophmore, junior, grad) is the class? Air resistance is very hard to quantify, so in lower level classes, it's ignored.

Thanks,


It's theoretically a graduate-level class, though with the Johns Hopkins engineering night school, the levels are sometimes kind of bogus. Also, it's just an overview course, so we don't go into a whole lot of depth. (In this semester alone, we're discussing system engineering, astrodynamics, propulsion, space environment, launch systems, attitude determination and control, and space power systems.)

J-Man
2001-Nov-16, 10:27 PM
> 2. Once achieving escape velocity when leaving the Earth, the Apollo would need to lose 5/6th of its velocity in order to be captured by the moon's gravity and swing into orbit. The spacecraft is moving at a velocity that prevents the Earth's gravity from pulling it back down - so unless they "put on the brakes" they certainly aren't going to be captured by the moon's gravity. However, all three stages of the Saturn V had been dropped - only the LEM remained.


J-Man says:
Actually, I believe, the CSM/LM were put into a free-return trajectory during the translunar burn. That means if they never fired the SM rocket they would return to earth. (Basically a figure 8 around the moon and earth. Good thing for 13.) They never actually reached earth escape velocity. They had to slow down (speed up? depends what direction you're talking about...) only to establish a near-circular lunar orbit. The earth was slowing them down before they even took off... and continued "pulling" them back the whole time.

That was my nitpick for the day... you guys are doing alright with the rest of it...

Wiley
2001-Nov-16, 11:14 PM
On 2001-11-16 14:02, ToSeek wrote:


On 2001-11-16 11:58, Wiley wrote:

Also what level (sophmore, junior, grad) is the class? Air resistance is very hard to quantify, so in lower level classes, it's ignored.

Thanks,


It's theoretically a graduate-level class, though with the Johns Hopkins engineering night school, the levels are sometimes kind of bogus. Also, it's just an overview course, so we don't go into a whole lot of depth. (In this semester alone, we're discussing system engineering, astrodynamics, propulsion, space environment, launch systems, attitude determination and control, and space power systems.)


If aerodynamic drag is important, I would've thought they would mention it in grad survey class. Mayhap it's not too important.

Donnie B.
2001-Nov-17, 12:11 AM
On 2001-11-16 17:27, J-Man wrote:

Actually, I believe, the CSM/LM were put into a free-return trajectory during the translunar burn. That means if they never fired the SM rocket they would return to earth. (Basically a figure 8 around the moon and earth. Good thing for 13.)



Ironically, Apollo 13 was the first moon shot in which the spacecraft was not on a free-return trajectory. This was true at the time of the accident, and once they had things somewhat stabilized, they used the descent stage engine to put the ship back on a free-return track.

The reason they were not on free return had to do with their targeted landing site. If they'd been on free return they couldn't have achieved the correct lunar orbit to put them on line for the Fra Mauro site.

Hat Monster
2001-Nov-19, 03:45 PM
Aerodynamic forces should be close to negligible. As the rocket gets higher, it gets faster since it's always under acceleration. As the rocket gets higher, air gets thinner.
So when the craft is in the thick tropospheric air, it's velocity is quite low. It's only ten miles to travel up and a rocket does that in less than a minute. It's once they get in the stratosphere and beyond that the real speeds start to be reached. Up there, there's precious little air to do any resisting.

The main reason for the vast size of the rocket is that as you add more weight to be lifted, you need more fuel. More fuel means bigger fuel tanks. Bigger fuel tanks mean more weight. More weight means more fuel. More fuel means bigger fuel tanks. Bigger fuel tanks mean more weight. More weight means more fuel. More fuel means bigger fuel tanks. Bigger fuel tanks mean more weight. More weight means more fuel, ad nauseatum.

Eventually, it levels off so that once you have a craft capable of reaching LEO then the payload needs 40x it's own weight in fuel and other weight extra on to the launch weight. That's on top of the fuel and engine power needed to get the craft itself into orbit, neglecting the payload.

SaturnV was capable of launching the Apollo Service Module, Command Module and LEM completely clear of Earth. That means that the rocket could lift the combined weight of those three modules, no mean feat, and drop them off anywhere in the solar system. We used it to take us to the moon. The SaturnV would have done for Mars, but technology of the day couldn't have kept the astronauts alive that long.

The LEM on the other hand, didn't even have to escape the moon. It just had to reach a low lunar orbit, which isn't a difficult thing to do in the 1/6th gravity and the designed low mass of the LEM. Many cheap enthusiast rockets could get themselves into lunar orbit from the lunar surface quite easily.

Wally
2001-Nov-19, 04:47 PM
[quote]
On 2001-11-15 14:40, Hat Monster wrote:
Bear in mind that one extra pound of weight means 40lb of fuel. More fuel is more weight.
Earth is bigger than the moon. Eagle had to reach Lunar Orbit. SaturnV had to reach Earth orbit (and cope with atmospheric drag) and also then ESCAPE from Earth orbit. Eagle did not.
[quote]

Is it really accurate to say that the Apollo spacecrafts "escaped" from Earth's orbit? Isn't it true that they were simply placed into a highly eliptical Earth orbit that in fact brought it within the affects of Moon's gravity, at which time it slowed down enough to be captured in a lunar orbit? Point is, it never really "escapes" Earth's orbit, right? The fact that they remain in Earth orbit (albeit, a highly eliptical one)explains why they experience weightlessness during the whole journey. Am I correct here?

JayUtah
2001-Nov-19, 05:47 PM
Isn't it true that they were simply placed into a highly eliptical Earth orbit that in fact brought it within the affects of Moon's gravity, at which time it slowed down enough to be captured in a lunar orbit?

Yes, essentially.

Of course to be accurate, a spacecraft is within the effects of the moon's gravity while it's sitting on the launch pad. Those effects are just overshadowed by other effects such as the gravity of more massive, nearer objects.

The translunar trajectory was, in essence, a highly eccentric orbit which brought the spacecraft into a velocity state where the moon's gravity, at a certain point, became more powerful than the earth's gravity, and therefore had a more profound effect on the spacecraft's trajectory than the earth's.

This was done for mission planning purposes. The Saturn V had enough capacity to achieve escape velocity with the Apollo payload. It was just safer to stick with the trajectory that offered the most opportunities to recover from failure.

The fact that they remain in Earth orbit (albeit, a highly eliptical one)explains why they experience weightlessness during the whole journey.

They experience weightlessness because they and their spacecraft follow identical trajectories. It doesn't matter whether you characterize that trajectory as orbital or interplanetary. Ask an orbital mechanics expert and he'll say everything's an orbit. They would have been weightless the whole time even had they reached escape velocity.

Weightlessness is something of an illusion. On earth the gravity pulls you down against the floor, so you feel pressure there. It pulls the contents of your stomach downward, but your stomach structurally prevents it from going where gravity wants it to go. Hence you feel pressure there. Without your stomach there, your lunch would pursue a different trajectory than that imposed on it.

When everything's gone ballistic, gravity is still acting on everything the same as it was. There's no such thing as "zero gravity". But because your stomach and its contents are following identical ballistic trajectories and are being accelerated equally by gravity, the net force between your stomach and its contents doesn't exist.

About half of all new astronauts find their stomachs and the contents thereof trying to pursue different trajectories for reasons having more to do with physiology than with gravity and ballistics.

ToSeek
2001-Nov-19, 05:49 PM
On 2001-11-19 11:47, Wally wrote:

Is it really accurate to say that the Apollo spacecrafts "escaped" from Earth's orbit? Isn't it true that they were simply placed into a highly eliptical Earth orbit that in fact brought it within the affects of Moon's gravity, at which time it slowed down enough to be captured in a lunar orbit? Point is, it never really "escapes" Earth's orbit, right? The fact that they remain in Earth orbit (albeit, a highly eliptical one)explains why they experience weightlessness during the whole journey. Am I correct here?



I think you're correct on the first item, that the Apollo spacecraft didn't reach true escape velocity but just close enough to make it to the moon on a timely basis. (Apollo 11's "escape" velocity was 35,579 feet per second, while Mars Global Surveyor's escape velocity - an actual escape velocity - was 37,563 fps.)

You are wrong about weightlessness, however. Weightlessness occurs wherever both the astronaut and the spacecraft are subject only to gravititational forces. If the astronauts were going to Mars (and not under acceleration), they'd still be weightless.

Wally
2001-Nov-20, 11:38 AM
"wrong" is such an ugly term! /phpBB/images/smiles/icon_wink.gif Actually, I think I just understated my point. . . that being that the craft (and anyone inside for that matter) is always under the gravitational influence of something, regardless of where it's at, and therefore can be considered in orbit around whichever mass has the most influence at the time. As JayUtah aply stated. . . "everything's an orbit" in the eyes of orbital mechanics. Thanks guys!

Irishman
2001-Nov-20, 07:23 PM
(Crappy software just deleted this a second time.)

"Weightlessness" and "zero gravity" are misnomers. The conventional definition of "weight" is the pull of gravity. Astronauts experience practically as much pull of gravity as people on the surface of the earth.

The difference is that the astronaut's evironment falls with them.

What we feel as gravity, is really all the tensions of our body resisting the pull. The ground pushes up on our feet, which holds the skeleton erect, and the organs all hang from the skeleton by tendons or by the skin enclosing the whole body or by the muscles connected to the frame. When a person is in free fall (i.e. skydiving - neglecting wind resistance), they do not experience the reaction force of all those tensions between the tendons and muscles and skin on the organs.

The reason astronauts are said to be weighless is because (a) they do not experience those resistance forces (i.e. the feeling of weight); and (b) they do not observe the visual behavior of weight, falling with respect to their environment. But that is an illusion. As astronaut on the space station is falling every bit as much as a skydiver falls after stepping out of the plane. The only difference is that the astronaut has a significant sideways velocity, fast enough that they fly past the edge of the Earth before they fall down to the surface, so to speak.

Here's a visual of what I mean. Project the Earth as a flat disk. Assume gravity is a uniform field pulling down from under the disk, such that it pulls above the disk and also beside the disk to some referent below the disk. Now drop a skydiver from above the center of the disk. With negligible sideways velocity (and neglecting air resistance), he falls straight onto the disk. Until he opens his parachute and increases drag. Now take an astronaut from above the skydiver and drop her, but throw her sideways really hard. As she falls, she translates to the side until she falls past the edge of the Earth. That is exactly what happens with an orbit. Except the disk is a sphere, and the gravity pulls toward the center of the sphere. The velocity still is the reason the astronaut does not bounce off the ground.

Wally
2001-Nov-21, 11:30 AM
I've always preferred the "super duper cannon on top of the really tall mountain" analogy. Shoot the ball parallel to the ground with enough force to get it a quarter of the way around the earth, and you begin to see how it's ballistic path almost matches the curve of the Earth. Increase the charge so the next shot travels half way around the Earth, and it becomes more evident. Now, use a full charge, and the ball's sideways velocity causes the curved decent tragetory to exactly match the curve of Earth. Voila! the ball's in orbit.

Taks
2001-Nov-23, 05:58 PM
I'm willing to bet everything I own that the LMs are quite a bit less massive than 1/6th their fully fuel-loaded Saturn rockets, thus it takes less force to propel them into orbit, and thus less fuel. If the lander was 100 times less massive it would only take 1/100th as much fuel, and be approximately 1/100th in size just to leave Earth. (That is, were its engines powerful enough to do so.) One would think that it would require even less to liftoff from the Moon.


Actually, it wouldn't it even take less than 1/100th as much fuel if the LM were 1/100th as massive? Rather, I don't think fuel and payload scale linearly with respect to each other as increasing payload, increases the amount of fuel required, which adds extra payload and so on. Perhaps a square relationship?

Not sure, but just a guess /phpBB/images/smiles/icon_smile.gif

Mark

I edited this to get quote formatted properly--tBA

<font size=-1>[ This Message was edited by: The Bad Astronomer on 2001-11-23 15:24 ]</font>

Mnemonia
2001-Nov-26, 02:11 PM
On 2001-11-23 12:58, Taks wrote:


I'm willing to bet everything I own that the LMs are quite a bit less massive than 1/6th their fully fuel-loaded Saturn rockets, thus it takes less force to propel them into orbit, and thus less fuel. If the lander was 100 times less massive it would only take 1/100th as much fuel, and be approximately 1/100th in size just to leave Earth. (That is, were its engines powerful enough to do so.) One would think that it would require even less to liftoff from the Moon.


Actually, it wouldn't it even take less than 1/100th as much fuel if the LM were 1/100th as massive? Rather, I don't think fuel and payload scale linearly with respect to each other as increasing payload, increases the amount of fuel required, which adds extra payload and so on. Perhaps a square relationship?

Not sure, but just a guess /phpBB/images/smiles/icon_smile.gif

Mark


Granted, I simplified the problem quite a bit. Only if the LM had to put out as much thrust (i.e. opposing force) as the Saturn booster would it require 1/100th the fuel if it was 1/100th as massive. Suffices to say it most certainly does not - the poor thing would have been broken apart accelerating that fast.

2001-Dec-02, 07:18 AM
On 2001-11-15 10:20, ToSeek wrote:
Isn't Mensa supposed to be an organization for smart people?


You are missing the point. Smart people should be able to figure these things out on their own. That is why it is on an "exam," not a "FAQ."

ToSeek
2001-Dec-03, 03:59 PM
On 2001-12-02 02:18, Rosen1 wrote:


On 2001-11-15 10:20, ToSeek wrote:
Isn't Mensa supposed to be an organization for smart people?


You are missing the point. Smart people should be able to figure these things out on their own. That is why it is on an "exam," not a "FAQ."


My impression was that these were serious questions being asked by people who honestly did not know the answer or thought that they were evidence of a hoax.

Squirm
2001-Dec-04, 11:55 PM
Jay: My favorite quote relating to Mensa comes from Will Rogers: "We're all ignorant. We're just ignorant about different things."

"<u>Be humble</u>, we're all ignorant. We're just ignorant about different things."

ToSeek
2001-Dec-05, 03:34 PM
On 2001-12-04 18:55, Squirm wrote:
Jay: My favorite quote relating to Mensa comes from Will Rogers: "We're all ignorant. We're just ignorant about different things."

"<u>Be humble</u>, we're all ignorant. We're just ignorant about different things."



Except for the Bad Astronomer himself, of course. /phpBB/images/smiles/icon_wink.gif


<font size=-1>[ This Message was edited by: ToSeek on 2001-12-05 10:35 ]</font>

Kaptain K
2001-Dec-05, 03:45 PM
Are you saying that the BA is ignorant in all things? /phpBB/images/smiles/icon_confused.gif

Donnie B.
2001-Dec-05, 06:25 PM
On 2001-12-05 10:45, Kaptain K wrote:
Are you saying that the BA is ignorant in all things? /phpBB/images/smiles/icon_confused.gif



Maybe he's saying the BA isn't humble... /phpBB/images/smiles/icon_smile.gif

The Bad Astronomer
2001-Dec-05, 09:17 PM
I think I'll stay out of this and let you hash this out!

ToSeek
2001-Dec-05, 10:14 PM
On 2001-12-05 13:25, Donnie B. wrote:


On 2001-12-05 10:45, Kaptain K wrote:
Are you saying that the BA is ignorant in all things? /phpBB/images/smiles/icon_confused.gif



Maybe he's saying the BA isn't humble... /phpBB/images/smiles/icon_smile.gif


I was of course acknowledging that the BA is all-knowing but manages to remain charmingly humble nonetheless. /phpBB/images/smiles/icon_wink.gif

GrapesOfWrath
2001-Dec-06, 06:44 AM
On 2001-12-05 16:17, The Bad Astronomer wrote:
I think I'll stay out of this and let you hash this out!

And wise too!

Donnie B.
2001-Dec-06, 10:42 AM
[Hands out tissues for purposes of nose wiping...] /phpBB/images/smiles/icon_smile.gif

ljbrs
2001-Dec-12, 02:50 AM
My membership in Mensa lasted less than one year, precisely because of the climate at the meetings. After a while it became apparent to me that these were people so stuck on their self-perception of intelligence in some areas that they were blinded to their ignorance in others. They'd go around confidently expounding utter nonsense just because they didn't want to admit ignorance of a pertinent fact.

What's the line from The Englishman Who Went Up A Hill And Came Down A Mountain? "We may be twp (i.e., stupid), but we're not so twp that we don't know we're twp."

Some of these people are precisely the type who can talk for three hours about hyperspatial manifolds and Grand Unification, and then go out and put oil in their car radiators.

Richard Feynman (considered to be the greatest American physicist) had a reported I.Q. of 123 (Stanford-Binet, since that was the I.Q. test given in high schools at that time). He would never have been admitted to Mensa, but he was truly brilliant.

That said, however, there are many knowledgeable people in Mensa. They do not stand out, because a high score on an I.Q. test does not qualify as great knowledge. A high I.Q. merely is an aptitude and not a *given*. People with brains which never are used, or which are used foolishly, remain ignorant. What you folks were discussing, in fact, was that the people with the high I.Q.s who showed ignorance, were not properly educated. They still had good mental capacities, but those mental capacities were never used and/or were misdirected in the direction of baloney. What a waste...

There are a great number of knowledgeable people in Mensa. As in any group of people, there are bound to be various abilities. The single criterion for being a Mensa member is a high I.Q. score (in the top 2%) on one of many possible tests. I.Q. tests taken in the past (such as some earlier S.A.T., G.R.E., etc.) were really I.Q. tests (before they became performance exams [probably superior to I.Q. tests in the sense of measuring knowledge]) can be, and are, regularly used for admittance into Mensa.

There are very many interesting people in Mensa. The most vocally foolish ones may sound or behave like imbeciles, but the test does not measure anything other than what it measures.

I.Q. is a measurement of potential of some kind or another. Obviously it did not measure Richard Feynman's superior abilities, so the test is flawed in that it did not measure his superior level of brilliance.

I happen to belong to a local Mensa group where there are a number of intelligent and knowledgeable people. I also belong to many other organizations where I.Q. is not a question, but where there are equally knowledgeable people. In my local group, the emphasis is directed away from pseudoscience. Most of the silly ones stay home from meetings.

I personally believe that perfection is a state of growth.

Of course, now I am going to get it for admitting to Mensa membership. I just wanted to set the record somewhat straight. I go to Mensa meetings in my area because many of the members are so very interesting AND KNOWLEDGEABLE. They treat women very well, also. Females in Mensa are able to have great discussions on any topic without any male chauvinistic baloney being mixed into the discussions.

ljbrs /phpBB/images/smiles/icon_smile.gif /phpBB/images/smiles/icon_biggrin.gif

NottyImp
2001-Dec-12, 10:09 AM
"I.Q. is a measurement of potential of some kind or another. Obviously it did not measure Richard Feynman's superior abilities, so the test is flawed in that it did not measure his superior level of brilliance."

As somebody once said (I paraphrase): "Your IQ score is nothing more than a measure of how good you are at IQ tests, and nothing else."

dgavin
2001-Dec-12, 02:03 PM
Radiation Shielding...

Something occurred to me, that would give an 'accurate' estimate of the amount of material it would take to shield the astronaughts from any radiation from the van allen belts.

I still am as a civilian, but when in the USArmy i worked for a time in germany, (83-86) where our computer system was contained inside two 10 ton trailers (the long single trailers mac trucks haul around) that were attached by an umbilical.

The specifications of these trailers, and the umbilical between them were rather intresting. The outer skin of the trailers were a compite of metals and ceramics, that was semi-rigid. it could be dented, but barely, it tended to push back to it's shape. If the specs were right the composite is stroger by an order of 4 then titanium. The insulation and frame of the trailers was also intresting. The frame was composed of the composite also, with a thin coating of lead. The insulation, was a lead coated fiberous compound, (not fiber glass).

The umbilical was made of the same material used in the N.B.C. suits, (i have no information on what that is), but 1/4 of it is all thats needed to block 99% of radiation in a contaminated area.

Total lead in one van? less then 1/2 ton.

With the umbilical dedatched quickly, the doors sealed, and the AC's turned on to not exaust air, and the internal oxegen tanks turned on, each van could protect about 5 people inside, from a 10 kton tactical nuke landing as close as a 1000 yards away. The trailers might roll from the forch if the blast hit side on, but could sustatian that force, and the rolling. The trailers had extract straps on them that people could use to lash themselfs against the walls, as well as lash lose equipment down.

The Trailers were also rated as survivable from a 100 megton blast from 2 miles+ distance from ground zero. The dose of radiation recived from each cenerio by people inside the trailers was the equivielent of about 6 medical x-rays, as long as they got the trailers sealed.

Comparing the Van allen belts to the radiation of a 100meg ton bomb at 2 miles, is like comparing the hover dam to the sun.

In it's simplest terms the amount of lead needed to shield the astronaughts is negligible. A coat of leaded paint would of been suffient, not to mention that most metals have some radiation shielding qualities, and that leaded paint would of been unneeded.

Wyz_sub10
2001-Dec-12, 03:56 PM
I just wanted to add that, not only was I a Mensa member as well (1.5 years), but I was also the national editor for their newsletter in Canada.

Let me just say that I have never met such an irrational, arrogant and vicious group of people in my life.

Honestly, I met maybe 2 or 3 people that I enjoyed speaking with. The Apollo questions do not surprise me. When I was editor I received articles on how healing touch and prayer cure illness, how the pyramids are actually over 10,000 years old, how Jesus was a devout astrologer, how the possession of child pornography is unfairly targetted as a criminal act, and countless articles on the joys of masturbation.

The executive was dysfunctional and the memebership erratic.

In short, if you're a smart guy or gal and like to engage in serious debate or discuss interest issues, find a good bulletin board or better yet, some interesting friends.

ToSeek
2001-Dec-12, 05:10 PM
On 2001-12-12 10:56, Wyz_sub10 wrote:

Let me just say that I have never met such an irrational, arrogant and vicious group of people in my life.


Don't hold back now - tell us what you really think. /phpBB/images/smiles/icon_smile.gif

Wyz_sub10
2001-Dec-13, 07:48 PM
Well, I shouldn't sound so bitter. I'm not. There were some really, really good people there.

But I think that too many of them were used to being "the smartest" - at work, in school, in their families, whatever.

Now, all of a sudden, they have to deal with people who have had that very same experience. Let me tell you, this did not bode well for the decision-making process at the executive level. Lots of backbiting, lots of wild accusations and rhetoric.

Hey, I know I can be as arrogant as the next guy or gal, but I like to think that I'm not an a$$ about it. Maybe others would disagree. /phpBB/images/smiles/icon_smile.gif

ToSeek
2001-Dec-14, 06:16 PM
On 2001-12-13 14:48, Wyz_sub10 wrote:
But I think that too many of them were used to being "the smartest" - at work, in school, in their families, whatever.

Now, all of a sudden, they have to deal with people who have had that very same experience. Let me tell you, this did not bode well for the decision-making process at the executive level. Lots of backbiting, lots of wild accusations and rhetoric.


Interesting thought on the social dynamics there - that hadn't occurred to me before. And they're probably more used to using their smarts to get their way than their social skills.

<font size=-1>[ This Message was edited by: ToSeek on 2001-12-14 13:16 ]</font>

JayUtah
2001-Dec-14, 07:20 PM
Michael Collins cites the urge to excel as one of the reasons for Buzz Aldrin's emotional difficulties following the Apollo 11 mission. Aldrin had been to the Air Force, West Point, MIT, and NASA. None of these is a particularly forgiving environment. They all push you to excel. And Buzz had apparently grown up in a family environment that prized pre-eminence.

Once you've walked on the moon, how are you going to top that? At age 40 Buzz discovered he was at the top of the mountain, but didn't know how to do anything except climb mountains.

I think part of the Mensa social dynamic might be the arrogance which arises from confidence taken too far. But some of it might be the Buzz Aldrin factor -- that people who are habitually expected to excel will do whatever they have to in order to excel. Put them in an environment where excellence is harder and they have problems.

ToSeek
2001-Dec-17, 03:08 PM
On 2001-12-14 14:20, JayUtah wrote:
I think part of the Mensa social dynamic might be the arrogance which arises from confidence taken too far. But some of it might be the Buzz Aldrin factor -- that people who are habitually expected to excel will do whatever they have to in order to excel. Put them in an environment where excellence is harder and they have problems.


This may also help explain why pro athletes have a generally poor reputation with regard to character: these are people who have been stars all their lives, but once they get to the pros they're with other people who have also been stars all their lives. It's not as easy any more.

Thumper
2002-Jan-09, 12:36 PM
Hello all,
This is my first post so I'll try to be brief, not make too much of a fool of myself, and not insult anyone. The BA has a wonderful website and only recently have I been enjoying your posts. And learning alot. Back to topic: Mnemonia is correct about the varying speeds of the LM-CM-SM stack as it heads towards the moon. The third stage booster gives the ships enough velocity to leave Earth orbit and head towards the moon. I can't remember the exact speed that they reach at maximum. The astronauts snag the LM as they separate from the booster and coast to the moon. They continually decelerate until they reach what they refer to as the "moon's sphere of influence". Here they start to accelerate towards the moon. This point is roughly (very roughly) three quarters of the way there. I think they have slowed to something like 2400 miles per hour before the moon's gravity starts to speed them back up.

Most but not all Apollo missions were on a "free return" trajectory meaning that if they'd done nothing, they would have whipped around the moon and headed straight back to Earth. A retrograde braking action by the service engine slows them enough to let the moon "capture" them in orbit. The reverse happens on the return trip. The service engine fires and gives them enough velocity to escape lunar orbit where they decelerate until they re-enter the Earth's sphere of influence.

Andrew Chaikin has a wonderful book about the space program called "A Man on the Moon" that explains many of these procedures in easy to read, enjoyable text. From this book, Tom Hanks and HBO made the series "From the Earth to the Moon" which would be in my DVD player at all times if I didn't think my wife would divorce me. Also the book "Lost Moon" (Apollo 13) has great information about some of the nuts and bolts of space travel.

Again, without trying to be insulting, it seems the questions from Mensa were fairly ignorant. There are plenty of sources one can use to find out many of the facts these questions seem to ignore. Keep up the good work. And I have made a fool of myself: I didn't realize there were two more pages of thread when I posted mine. Should have kept my mouth shut...

_________________
When in doubt, stand on it - Stroker Ace

Thump

<font size=-1>[ This Message was edited by: thumper on 2002-01-09 10:28 ]</font>

JayUtah
2002-Jan-09, 04:57 PM
I can't remember the exact speed that they reach at maximum.

The maximum earth-fixed velocity achieved by Apollo 11 was 34,229.7 feet per second. This occurred at the instant the J-2 engine on the S-IVB stage shut down after its second burn.

The astronauts snag the LM as they separate from the booster and coast to the moon.

Sure, and those burns are actually factored into the flight dynamics. For example, the command module pilot was expected to execute a 1 fps separation and distancing maneuver upon release from the S-IVB spacecraft adapter. All that goes into the computer.

They continually decelerate until they reach what they refer to as the "moon's sphere of influence".

While this phrase has meaning in cislunar flight dynamics, it's somewhat confusing to the layman. Those who experience ocean tides can testify that the moon's "sphere of influence" extends all the way to the earth's surface. The spacecraft is affected by the moon's gravity while sitting idle on the launch pad.

If we could draw a straight line between the center of the earth and the center of the moon, there would be a point along that line at which the gravity of the earth and moon balance out. Points beyond this would be considered within the moon's sphere of influence because the moon's gravity would dominate.

But if we consider the three-dimensional problem of translunar trajectories, and recall that gravity is a vector quantity (a tensor, really), we discover that deciding where the "moon's sphere of influence" begins is very difficult. The vector sum of the earth's and moon's gravity changes magnitude and direction smoothly throughout the translunar coast.

So the "moon's sphere of influence" has less to do with orbital mechanics and gravitational physics and more do to with the way the spacecraft's navigational software was written. Mission planners arbitrarily decided on a point at which the spacecraft would stop navigating in an earth-centered framework and start using the moon as its central reference. Theoretically this could have happened at any point along the way, but a specific point was chosen.

On Apollo 8 the changeover produced a slight discrepancy in the spacecraft's idea of its location. The dead reckoning errors had accumulated to the point where the changeover made the spacecraft appear to "jump" instantly from one point in space to another. When this was explained to the press, they got it wrong and reported that the spacecraft had experienced a jolt. This has lead to the widespread (and incorrect) belief among conspiracy theorists that an authentic lunar mission would experience such a jolt.

I think they have slowed to something like 2400 miles per hour before the moon's gravity starts to speed them back up.

That sounds about right. I have the exact figure somewhere but it's not immediately at my fingertips.

The analogy is not unlike coasting over a hill in your car. You gun the engine for a brief time and coast to the top, slowing all the while. You know as you pass the brink your car will begin to accelerate again. But to keep it from falling backwards you make sure you pass the brink with just a little extra speed. You don't want your velocity to be zero as you arrive at the brink; you want to have some forward momentum.

Most people are surprised to learn that the Saturn V was actually capable of getting the astronauts to the moon faster. By the time the S-IVB (third stage) had finished its job, there was still fuel in the tanks. They could have burned to depletion and sped up the process. But in doing so they would have imparted velocity that would need to be shed in order to effect a lunar orbit capture. Or worse, it would have required additional fuel for a direct abort.

Most but not all Apollo missions were on a "free return" trajectory meaning that if they'd done nothing, they would have whipped around the moon and headed straight back to Earth.

Apollos 8, 10, 11, and 12 used the free return trajectory. All the rest used various hybrid trajectories. All the trajectories involved velocities too great for natural lunar orbital capture. The principle difference between the free-return and hybrid trajectories is the direction in which the spacecraft leaves the vicinit of the moon.

It is common to portray these trajectories as two-dimensional constructs when in fact they have rather complicated three-dimensional geometry. The hybrid trajectories enter lunar orbit with an inclination which gives access to a greater portion of the lunar surface, and therefore greater access to attractive landing sites. But this inclined orbit means that a circumlunar spacecraft will be flung away along an inclination which misses the earth.

A retrograde braking action by the service engine slows them enough to let the moon "capture" them in orbit.

The LOI-1 burn, or capture burn, bled off 2,924.1 fps of velocity for Apollo 11. This puts the spacecraft in a somewhat elliptical orbit (60 nm by 170 nm). To circularize the orbit, the LOI-2 or circularization burn is also performed in retrograde at pericynthion. It reduces velocity by 157.8 fps and produces a 53x66 nautical mile orbit.

The two basic ways to circularize an orbit are to perform a retrograde burn at periapsis or a posigrade burn at apoapsis.

The service engine fires and gives them enough velocity to escape lunar orbit where they decelerate until they re-enter the Earth's sphere of influence.

3,292.7 fps for this burn on Apollo 11. Why this is more than the LOI-1 burn is left as an exercise for the reader.

... if I didn't think my wife would divorce me.

A sad footnote to the Apollo program is the high rate of divorce and stress-related mental illness incurred by those who worked on it. We may never know the true human toll of the lunar landings.

Again, without trying to be insulting, it seems the questions from Mensa were fairly ignorant.

Colossally ignorant, in my opinion. I expect better from people who bill themselves as the cream of the intellectual crop.

But I'm more convinced that these are not necessarily serious questions. You must recall that the Mensa journal is, above all, a journal. And an editor's job is, above all, to increase the readership of his publication. In some cases this means publishing something controversial or intentionally inflammatory so as to cultivate interest in the publication.

ToSeek
2002-Jan-09, 05:38 PM
On 2002-01-09 11:57, JayUtah wrote:
You must recall that the Mensa journal is, above all, a journal. And an editor's job is, above all, to increase the readership of his publication. In some cases this means publishing something controversial or intentionally inflammatory so as to cultivate interest in the publication.



Wasn't one of the more noted HBers once a columnist for the national Mensa magazine? Maybe that's why he was there!

JayUtah
2002-Jan-09, 05:41 PM
Ralph Rene, author of "NASA Mooned America", was a Mensan, but I do not know if he ever held any position that would give him access their national publication. Rene was expelled from the group and has not associated with them for some time.

ToSeek
2002-Jan-09, 05:56 PM
On 2002-01-09 12:41, JayUtah wrote:
Ralph Rene, author of "NASA Mooned America", was a Mensan, but I do not know if he ever held any position that would give him access their national publication. Rene was expelled from the group and has not associated with them for some time.



His bio (which I just found) mentions a column for "various Mensa publications," but doesn't specify which one.

Wiley
2002-Jan-09, 11:55 PM
I'm now officially tempted to join Mensa to see if it is as bad as y'all say.

(You may now try to disuade me.)

Thumper
2002-Jan-09, 11:56 PM
Thank you JayUtah for the welcome. I did say I'd try to be brief. Therefore I left out many of the specifics. Some of which, like you said, would have to be looked up. The "sphere of influence" language came from memory from both "Lost Moon" and "A Man on the Moon". But I agree that all bodies of mass are always acting on all other bodies of mass no matter what the distance.

The big point is that even if one doesn't know the facts off hand, they are easily accessible especially in this web environment.

I feel honored by the welcome.

ljbrs
2002-Jan-10, 02:18 AM
Actually, a great many of the members of Mensa are just wonderful, but I belong to the best of the groups in the country (voted as such). Most of the lectures at meetings and *gatherings* are on great topics. It is not the only group to which I belong and one meeting a month works well for me. Mensans are not all arrogant and they are, as a rule, very nice and friendly. I am picky about the friends I make, so I tend to have a great time wherever I am. There are people in Mensa with whom I can discuss just about any topic without running into baloney. Of course, there are some who are true believers, but I avoid them and such silliness. I do not run into many male chauvinists in Mensa, so I value the group on that score.

I belong to many other local groups, most of which are subject-oriented (such as amateur astronomy, physics lectures, symphony music, skepticism, etc). I think there are silly people in any group. Silly people are easy to avoid. Of course, one person's *silly person* is another person's *genius* -- so I decide my interests and my friends according to my taste for myself and let others decide their interests and their tastes for themselves. One of my favorite people was physicist (and Nobel Prize Winner) Richard Feynman (who was a REAL GENIUS). So, IQ is not that meaningful to me.

ljbrs /phpBB/images/smiles/icon_smile.gif /phpBB/images/smiles/icon_biggrin.gif /phpBB/images/smiles/icon_wink.gif

Lung
2002-Jan-10, 02:25 AM
The height of Saturn V attributed to gravity? /phpBB/images/smiles/icon_eek.gif Did they stay up all night thinking of that one? /phpBB/images/smiles/icon_rolleyes.gif It's mass was (payload vs fuel), but it's dimensions related to aerodynamics, among other things. Strange that such a no-brainer would come from Mensa!

From the stupidity of the questions, perhaps they should be called Densa /phpBB/images/smiles/icon_biggrin.gif

Silas
2002-Jan-10, 03:51 PM
On 2002-01-09 18:55, Wiley wrote:
I'm now officially tempted to join Mensa to see if it is as bad as y'all say.

(You may now try to disuade me.)



Dissuade, heck: do it! Let us know what you find!

(I would, but, um, er... My... You know... Isn't big enough... Blush...)

Silas

Thumper
2002-Jan-11, 10:56 AM
Just for curiosity sake, what kinds of tests do you take and how high do you have to score to become an esteemed member?

I know, I know, if I have to ask.......

<font size=-1>[ This Message was edited by: thumper on 2002-02-04 06:38 ]</font>

Wiley
2002-Jan-16, 11:15 PM
On 2002-01-11 05:56, Thumper wrote:
Just for curiosity sake, what kids of tests do you take and how high do you have to score to become an esteemed member?

I know, I know, if I have to ask.......


You need to in the top 2%, and this typically translates into an IQ of about 130. (This is very test dependent.) They also accept GRE scores and you would need to average about 625 on each section.

I'm very sceptical of IQ tests. I have taken a psychologist administered test and a standardized test, and the difference between the two was over 30 points. One of these test has some whopping error bars - I assume its the one that gave the lower score. /phpBB/images/smiles/icon_smile.gif

I'm also very sceptical of IQ in general. I recommend Stevie Gould's book, "The Mismeasure of Man". I think this is one of those "must read" books. And its not just a "must read"for those people who are interested in science, but its a "must read" for everybody.

JayUtah
2002-Jan-16, 11:40 PM
The fad over I.Q. has generally disappeared because it is becoming more apparent that intelligence is not something which can be effectively defined, much less measured by tests which are known to contain social biases and instrumentational ambiguity.

For example, my sister took a placement test when she was four years old, attempting to enter kindergarten early. She failed because she gave the wrong answer to the question, "If I divide an orange in half, how many pieces are there?" Her answer was eight, referring to the average number of segments -- four in each half. The "correct" answer was, of course, two. According to the test she was a moron. But how many four-year-olds are astute enough to notice and remember the number of segments in a typical orange?

And as I mentioned earlier in this thread, "intelligent" people are not infrequently possessed of some rather interesting dysfunctions. Some Mensans can speak for hours on, say, hyperspatial manifolds and the nature of the universe. Then they go out to the garage and pour oil in their car radiators. You could argue that the ability to function in daily life is a more valuable mental skill than the ability to manipulate esoteric concepts.

The Curtmudgeon
2002-Jan-17, 12:12 AM
I haven't really been paying that much attention to this thread, although I've enjoyed some of the barbed comments about people's experience with Mensans, which mostly tally with my personal experiences. I spend a great deal of my "free" time with a non-IQ-related interest group that by pure coincidence (I can think of no other explanation) had a significant overlap with the local Mensa group several years ago while I was on the board; nearly one and all of us non-Mensans in the org had a field-day with the apparent lack of common sense among the Mensans.

Quite a number of Jovian years ago, I did express some interest in Mensa, only to find that there was already an organisation, either Four Sigma or else Sigma Four, which was formed by people who wouldn't waste their time with Mensa because of the general snobbishness and such therein. The kicker was that, because it was the snooty behaviour that ticked them off, they decided to base their organisation on a requirement that would disqualify most Mensans, so that they could have some collective fun by keeping the Mensans out. They required an IQ score such that, while Mensa allows approximately 2% of the populace by IQ, 4S or S4 would only accept about 2% of people who qualified for Mensa. But other than their disdain for Mensa "bigots", they seemed like a much better-rounded and fun group.

Does anyone know if that group is still around? I've not heard of them in donkeys' years (my donkey died sometime back when "Keep Cool with Coolidge" was a front-runner).

The (not to boast, but I could have joined--I think) Curtmudgeon

ToSeek
2002-Jan-17, 02:35 PM
On 2002-01-16 19:12, The Curtmudgeon wrote:

Does anyone know if that group is still around? I've not heard of them in donkeys' years (my donkey died sometime back when "Keep Cool with Coolidge" was a front-runner).


According to a couple of websites, including this one (http://s-2000.com/hi-iq/societies/society_facts.html), the Four Sigma Society is inactive.

There are some others listed if you still want to be an IQ snob. /phpBB/images/smiles/icon_wink.gif

Wiley
2002-Jan-18, 08:33 PM
On 2002-01-10 10:51, Silas wrote:
Dissuade, heck: do it! Let us know what you find!

(I would, but, um, er... My... You know... Isn't big enough... Blush...)

Silas


Well, my social experiment may have come to a premature end.

Since my IQ tests are over 20 years old, I dought I'll be find the psychologist who administered 'em to certify 'em. I can't find my GRE scores and I can't order new ones since they are over five years old. Thus my only option appears to be to sit for Mensa's test. This would require time and money on my part; hence, the premature end. /phpBB/images/smiles/icon_frown.gif /phpBB/images/smiles/icon_smile.gif

<font size=-1>[ This Message was edited by: Wiley on 2002-01-18 15:33 ]</font>

Wyz_sub10
2002-Jan-22, 05:00 PM
Curtmudgeon,

Four Sigma is still around as far as I know (a friend in NYC used to bug me to join - that was as recently as last summer).

For the record, I *did* meet a few good people in Mensa, and I'm sure there are many more that I did not have the pleasure of meeting).

Still, the atmosphere just wasn't fun, and there was a lot of pettiness. Why spend your precious free time doing something unpleasant?

chuckle
2006-Sep-03, 02:49 PM
surely the way to answer this query is to say 'what does each manifestation of the space-craft need to carry at each point and for what purpose?' This is almost surely best calculated in reverse from end to start.

Simplifying (and probably getting wrong) the many actual "burn" and "separation" stages (including potential abort burn stages) the Saturn 5 rocket had to lift off the ground...

1) fuel to allow any deceleration burn of the final earth re-entry module from velocity at the end of the (gravity influenced) transit from moon to the velocity necessary to renter earth's atmosphere
+2) fuel to accelerate the earth re-entry module (including fuel#1) from the lunar orbit to decent velocity to make trip back to earth
+3) fuel to lift (top section) of lunar module (2 crew) from moon surface to orbit
+4) fuel to decelerate and control lunar lander (including fuel#3) during landing on moon
+5) fuel to decelerate lunar lander (including fuels#3-4) from orbit into decent*
+6) fuel to decelerate various lunar module elements (including fuels#1-5) from velocity when reaching moon to lunar orbital velocity
+7) fuel to accelerate all modules travelling to moon (including fuel#1-6) from near earth orbit velocity (assuming such an orbit was involved - not sure) to velocity required to reach moon in reasonable time (subject to fluctuations in speed caused by gravitational fields)
+8) fuel to lift all successive main rocket stages (including the various lunar-travelling vehicles plus fuel#1-7) from the earths surface to near earth orbit (minus weight of successive rocket stages after the point where dropping away).

Contrasting (8), which is requirement for Saturn 5, with (5), which is the requirement for the lunar landing vehicle (albeit before it leaves part of itself behind on the moon), there is clearly a huge discrepancy caused in part by the compound nature of the fuel requirements. Also surely the relative arithmetical relationship between the "strengths" of the two gravities (? 1/6) is compounded by the fact that any burn required to reach/leave near-orbit has to be somewhat longer (as well as stronger) for earth.

Clearly these cumulative / exponential effects are what the editors of Mensa would have been hoping to get members to recognise and comment upon in their responses. They are reminiscent of those sort of "how many trips does it take to ferry a fox, a chimpanzee and a water buffalo across a desert with a bicycle built for three?" sort of problems which you used to get in puzzle books for kids.

*Possibly the lunar lander module could have been decelerated (to start "falling" from orbit) by "burns" carried out by the orbiting module whilst they were still linked together (meaning the lander itself would not have had to be "big enough" to carry that extra bit of deceleration fuel itself, but meaning that the orbiting module would have had to burn again after separation to stop itself from falling too and restore its orbit). This is probably overcomplicated and almost certainly less fuel efficient overall, but I can't figure that out as its a trade-off between the extra fuel (and capacity) used by the orbiter slowing and speeding itself (unnecessarily) against the fuel required for the lander to carry that extra "deceleration fuel"-capacity down to the surface. I suspect that the latter is probably marginal and still the most efficient overall (especially since it then leaves behind it's descent gear). Either way the relevant 'capacity' has to be conveyed to the moon (with the fuel implications that has). If the lander does its own deceleration that capacity also has to be lowered in a controlled way to the surface, but if the orbiter does the deceleration then that bit of capacity may also have to be brought back to earth orbit. If the deceleration burn is short but uses lots of fuel then it may work out cheaper to make the orbiter do it. Unfortunately I think it takes a rocket scientist to work that out...

Grashtel
2006-Sep-03, 08:24 PM
Um, Chuckle you do realise that you are replying to thread that is over four years old?

Faultline
2006-Sep-03, 09:50 PM
Yes, spaceflights between planetary bodies are far more complex than just "point and shoot".

It's even more complex than just "escape Earth orbit and fly to the moon, then insert into lunar orbit."

Science fiction makes it seem easy.

"There's nothing routine about flying to the moon,"
Tom Hanks (as Jim Lovell)

Faultline
2006-Sep-03, 09:52 PM
Heck, I didn't realize it either!

hello people
2006-Sep-03, 10:43 PM
Isn't Mensa supposed to be an organization for smart people?

Ho, ho! Dr Spock with the wit!!

Gillianren
2006-Sep-04, 12:50 AM
Ho, ho! Dr Spock with the wit!!

Mr. Spock. Dr. Spock was a pediatrician.

Dwight
2006-Sep-04, 12:56 AM
This whole discussion of IQ tests reminds me of the MASH episode where Klinger tries to get into a Military Acedemy, and must do an IQ-style test. Responding to a division question involving portions of beans, he cries out "What kind of mother only feeds their family beans??"

publiusr
2006-Oct-03, 11:17 PM
Good question.

We've always had blowhards in Academia. (the ones making Nasa Chief' Mike Griffin's life a living hell for example)

I want to go in a slightly different direction. Would great leaders of the past be criminals today--and would folks who have found their way into power today be serfs in yesteryear?

Could Newton have written the Principia with cell phone intrusions.

I think the closest thing we had to a republic--with all its failings--was a real life Eureka...here:
http://en.wikipedia.org/wiki/Akademgorodok

I wonder what good come from here if funded again as in the past.


http://en.wikipedia.org/wiki/Russian_Academy_of_Sciences

tsig
2006-Oct-04, 01:59 AM
My membership in Mensa lasted less than one year, precisely because of the climate at the meetings. After a while it became apparent to me that these were people so stuck on their self-perception of intelligence in some areas that they were blinded to their ignorance in others. They'd go around confidently expounding utter nonsense just because they didn't want to admit ignorance of a pertinent fact.

What's the line from The Englishman Who Went Up A Hill And Came Down A Mountain? "We may be twp (i.e., stupid), but we're not so twp that we don't know we're twp."

Some of these people are precisely the type who can talk for three hours about hyperspatial manifolds and Grand Unification, and then go out and put oil in their car radiators.

And then get mad because it didn't work.

tsig
2006-Oct-04, 02:10 AM
If aerodynamic drag is important, I would've thought they would mention it in grad survey class. Mayhap it's not too important.

Once you make 7 miles a second the atmosphere means nothing. you are beyond it

Grashtel
2006-Oct-04, 04:00 AM
Once you make 7 miles a second the atmosphere means nothing. you are beyond it
Tell that to a meteorite, they come in at least that fast and have a tendancy to explode on hitting the denser parts of the atmosphere, and if they don't get a significant portion of their mass burn off during their passage.

gwiz
2006-Oct-04, 11:34 AM
This whole discussion of IQ tests reminds me of the MASH episode where Klinger tries to get into a Military Acedemy, and must do an IQ-style test. Responding to a division question involving portions of beans, he cries out "What kind of mother only feeds their family beans??"
In my youth I toyed with the idea of joining Mensa, but then they had a very public spat about the leadership which didn't impress me at all. I came to the conclusion that it was a society for people whose high IQ was the only thing going for them.

Tog
2006-Oct-04, 12:29 PM
My friend and I took the self scoring MENSA test in a restraunt one night. My score was right on the border but well within the "come on and take the real test" margins. Aside from the fact that it was $400 just to take the test, I had to ask what would be the point of joining. The best thing I could come up with was that it would look good on a resume. THen I found out that most people didn't know what MENSA even was. Not sure if I'd get in or not, but I really don't see a point in considering it any more.

aporetic_r
2006-Oct-04, 01:18 PM
My friend and I took the self scoring MENSA test in a restraunt one night. My score was right on the border but well within the "come on and take the real test" margins. Aside from the fact that it was $400 just to take the test, I had to ask what would be the point of joining. The best thing I could come up with was that it would look good on a resume. THen I found out that most people didn't know what MENSA even was. Not sure if I'd get in or not, but I really don't see a point in considering it any more.

Joining MESNA has always seemed to me similar to using ", Ph.D." after your name all the time. If you didn't do it, there'd be no other evidence that you're supposed to be smart.

Nicolas
2006-Oct-04, 01:23 PM
using ", Ph.D." after your name all the time.

:D

There's a Ph.D siting right next to me. He'd be more inclined to write "table football player" next to his name than Ph.D :D.

publiusr
2006-Oct-05, 08:24 PM
Ph. D

Post Hole Digger

tdn
2006-Oct-06, 07:26 PM
Aerodynamic forces should be close to negligible.
I'd have to disagree with this. You could check with residents of New Orleans to see what winds of that speed are capable of.

There is a formula to calculate drag, and it's mighty complex, but in model rocketry, at least, it's a huge factor. In fact I read that NASA consulted with model rocketeers to figure out drag. I don't think they did this for the Apollo program, however.

Maksutov
2006-Oct-06, 09:13 PM
Ph. D

Post Hole DiggerWow, a resurrected post not done by jkwhoever! :dance: http://img137.imageshack.us/img137/566/iconwink6tn.gif

Re MENSA, I've been a member on and off since 1968. A few meetings were enough to convince that there were too many people at those meetings who were overly impressed with themselves, something that makes a meeting long and boring, with pettiness as first order of business.

I've had interesting conversations by correspondence with a few MENSAns, but most folks at the meetings talk too much and say too little.

Besides this, the main reason for remaining a member was the monthly magazine whose "Letters to the Editor" section was a hoot. Most of the letters consisted of "I'm smarter than the author of that article and therefore I'm right!" followed next month by "I'm smarter than the author of that letter to the editor about that article and therefore I'm right!" and so on.

Speaking of humor, concerning that 4-year-old quote of a Groucho Marx quip even older, yes, Groucho had writers, but he also ad-libbed on a regular basis. One of the many anecdotes about George S. Kaufman takes place during a rehearsal of "Animal Crackers". Kaufman listened to the Marx Brothers have their way with his script before finally complaining: "Excuse me for interrupting, but I thought for a minute I actually heard a line I wrote."

http://img85.imageshack.us/img85/4590/naughtynr7.gif (http://imageshack.us)

JFM
2006-Oct-10, 05:38 AM
I was a MENSAN for years. Sheeesh what a bunch of thingies, &*%^$$$$%%%^ and boring.

Thing is, I live not 2 mile away from the HQ, so I see the leftovers almost daily.

MENSA. George street, Wolverhampton WV!..................I.....................No sense of humour. ALL trekkies/trekkers..............Stop me now!!!!!!

mugaliens
2006-Oct-16, 06:29 PM
I think the air resistance must be huge. A cyclist going 20 mph expends 90% of his or her energy overcoming are resistance. Of course cyclists don't have to overcome gravity (I refuse to cycle uphill) but I'd still wager that air resistance will be significant.

It is! I cycle 13 miles to work each day and live at the top of a fairly high (about 500') hill.

Needless to say, I get a bit of a workout on the way back home!

But you're right - at my average velocity, air resistance eats up 5.7 times, or about 82% of my energy. Going uphill, it's negligeable, but going downhill, it's eating up more than 95% of my energy.

The cool thing is that in the city, I'm usually passing cars rather than them passing me. :dance:

mugaliens
2006-Oct-16, 06:32 PM
After passing my test back in the 80s, I went to precisely three Mensa meetings before I realized IQ and common sense are neither negatively nor positively correlated.

Ask for the Ask Maralyn (sp?) column, thanks, but I'd rather not. I've spotted so many holes in her "answers" over the years that I can't even read Parade anymore.

mugaliens
2006-Oct-16, 08:06 PM
This is a total non sequitur. The Saturn V is so big because it needs to send a huge amount of payload (its third stage and the command and lunar modules) to the moon. Even a rocket as small as a Delta is capable of giving its payload escape velocity.

The lunar module, on the other hand, only needs to deal with its upper stage and only needs to get that into lunar orbit, not out of lunar orbit.

You raise an interesting question: What's the smallest total mass of a rocket, given current technology, that could escape Earth's orbit and reach the Moon? (non-landing - just to the mid-point). No payload - just the rocket and guidance system.

I would think there would have to be a practical limit due to atmospheric friction, but certainly the greater the g-forces it could withstand during acceleration, to a point, the less mass it would have to have. I say to a point for there's a tradeoff between energy efficiency with higher thrust and getting too fast too soon and loosing too much energy in the lower atmosphere.

Then again, the 250 kt AGM-69A SRAM (Short Range Attack Missile) launched by the likes of the venerable B-52 and the FB-111A could achieve greater than Mach 3 (first stage) and Mach (classified) (second stage) and travel a hundred miles in several minutes before hitting it's target.

Quite a feat for a 1,000 missile carrying a 200 kT W-69 thermonuclear warhead.

Especially in 1969.

Sigma_Orionis
2006-Oct-16, 09:58 PM
So? everyone knows that the US gets ALL its technology from Aliens :dance:

Larry Jacks
2006-Oct-16, 10:53 PM
You raise an interesting question: What's the smallest total mass of a rocket, given current technology, that could escape Earth's orbit and reach the Moon? (non-landing - just to the mid-point). No payload - just the rocket and guidance system.

That is an interesting question. My first thought is of the Pegasus XL (http://www.astronautix.com/lvs/pegsusxl.htm), only instead of having a payload into Earth orbit, you'd use added propellant for the upper stage. Would that be enough to reach the moon? With a solid fuel engine with an Isp of 240 seconds, perhaps not. What if you launched a small liquid fueled final stage with a higher Isp? That might work.

If you were going for the lowest possible mass, I think you'd need an air-launched liquid fuel rocket. With the higher Isp from the liquid fuel, it could be a lot less massive than the Pegasus but a lot more dangerous to the carrier aircraft.

I would think there would have to be a practical limit due to atmospheric friction, but certainly the greater the g-forces it could withstand during acceleration, to a point, the less mass it would have to have. I say to a point for there's a tradeoff between energy efficiency with higher thrust and getting too fast too soon and loosing too much energy in the lower atmosphere.

Everything in engineer is a tradeoff, especially for space vehicles. If you build a vehicle for higher G loadings, then you may gain some efficiencies. However, you'd also have some potentially significant weight penalties because you'd need a heavier structure to withstand the loads. If it is a solid fueled system, you might have to contend with a heavier casing to withstand higher internal pressures. Your avionics would need to be more rugged to withstand heavier G and vibration loads, too. Nothing is free.