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The Bad Astronomer
2002-Jan-19, 11:48 PM
This morning, I taped an interview with the Pax TV show "Encounters with the Unexplained". It was about the Hoax of course. It was interesting; given the topics covered and the actual text, I think there is a chance the show will actually be fair! I have no idea, of course, until I see the final edit, but I tried to phrase what I was saying so that "creative editing" would be difficult (a la the Fox show). I don't know when it'll air, but probably in either late March or April. I'll send out a note when I find out.

Chuck
2002-Jan-21, 05:52 AM
I've seen a couple of episodes of "Encounter". My impression is that they're mission is to prove that biblical events actually happened as described by the bible. I don't expect anything remotely fair.

JayUtah
2002-Jan-22, 04:18 PM
Well, it's "in the can" now, so we can just hope for the best and be prepared to close ranks if necessary.

While I believe the Hare Krishna folks have an institutional problem with the moon landings (their cosmology contradicts it), I can't imagine why Christians would want to treat the subject in any way other than scientifically. Several of the astronauts were devout Christians, and Jim Irwin left the astronaut corps to found a Christian ministry.

Chuck
2002-Jan-22, 04:36 PM
I'd be surprised if they deny that the moon landings took place. I just wonder how they'll use the interview to support their own theories.

SpacedOut
2002-Mar-14, 07:50 PM
Just a reminder: The show will air on Sunday March 17.
I'm sure there will be a lot to discuss come Monday!!!

James
2002-Mar-17, 06:15 PM
I've got my VCR set and ready.

Anybody who misses it can send $20 American S & H to...

JayUtah
2002-Mar-17, 09:14 PM
DirecTV's synopsis reads:


"Did We Land a Man on the Moon?; Who Wrote the Bible?" Skeptics say Apollo 11's landing on the moon was fabricated; researchers try to identify the Bible's authors."

JayUtah
2002-Mar-18, 02:50 AM
Well done, B.A.

By the commercial I was very dismayed. It seemed as if this would be just another unrestricted soapbox for the hoax crowd. But after the commercial they seemed to have balanced the scales.

Some notes:

Kaysing is still talking, "based on my experience at Rocketdyne." Did anyone tell PAX he was the librarian?

I felt the focus on Kubrick was a little odd. I enjoy his films and generally agree with what was said, but it's very easy to rebut an argument that Kubrick had the expertise to stage a moon landing convincingly. See my page http://www.clavius.org/movies.html

I was a little dismayed that the editors led from the question of 1960s technology right into Sibrel's first comment. It makes it sound like Sibrel is a relatively dispassionate video expert expressing his opinion.

Kaysing's claim that he has seen 10,000 pound engines at Rocketdyne throwing boulders across canyons is pure bulldeleted, pardon the language. Just one 757 engine is on the order of 50,000 pounds thrust, and you don't see them digging down to bedrock.

I am going to quibble with B.A.'s discussion of thrust. To say that a rocket engine develops 2,500 pounds of thrust is not the same as saying the exhaust plume exerts a force of 2,500 on an underlying surface. But do not despair; the actual pressure is much lower. See my work in progress: http://www.clavius.org/techexhaust.html

The discussion of the Sibrel footage was a bit disjointed. I expected Sibrel to make the cutout argument, but he stopped short and argued only the window outline argument. I think the rebuttal went well. It would have been better had PAX supplemented the explanation by shuttle footage.

Kaysing's argument that high-temperature ovens could be used to produce any type of rock is, of course, pure garbage. I don't think the refutation worked as well here, and it's likely because B.A. didn't know the specific argument that would be made. All rocks are produced in high temperature environments, including those that are known to be from earth and those known to be from the moon.

I think PAX struck a blow in our favor when they closed by implying that nothing will change the conspiracists' opinions. Kaysing is quoted as saying nothing will change his mind now. This is a departure from his opinion on the Fox program wherein he said that if a photo could be taken of Apollo remnants, he would recant.

As a final note, I love the globes on the desk. Can you score me a moon globe?


<font size=-1>[ This Message was edited by: The Bad Astronomer on 2002-03-17 22:08 ]</font>

James
2002-Mar-18, 03:56 AM
I just saw the show on tape.

IMO, Kaysing is just a doddering old fool who should be pumped full of drugs(if he isn't already) and stuck in a nursing home for the rest of his life.

Anyway, on to the review:

When I saw that PAX TV had said that Kaysing as a Rocketdyne "engineer", I was like, bull fritters. I didn't remember what he was, but I knew he wasn't an engineer(he was a librarian. Thanks, JayUtah). The first half of the show had too much of Kaysing just yakking. I just fast forwarded through the parts where either the VO or the idjits were talking. When BA was talking, I stopped what I was doing and paid 100% attention to you... /phpBB/images/smiles/icon_wink.gif Just kidding. /phpBB/images/smiles/icon_smile.gif I just watched the parts with BA in them.

Finally, IMO, Sibrel needs to get a life. He's young, he's got a chance to meet someone who'll knock some sense into him...Nah.

odysseus0101
2002-Mar-18, 04:10 AM
Jay,

Have you thought of producing a video? Just wondering...

JayUtah
2002-Mar-18, 04:19 AM
When I saw that PAX TV had said that Kaysing as a Rocketdyne "engineer", I was like, bull fritters.

Yes. Apparently the forum rules don't allow what I believe to be the most descriptive words for Kaysing's arguments, so "fritters" will have to approximate it. That's what you get for writing a review right after you see something. /phpBB/images/smiles/icon_smile.gif

Seriously, 10,000 lbf won't even lift two Ford Explorers in earth gravity. It simply ain't that much thrust. I'm sure Kaysing saw some powerful engines at Rocketdyne, but the LM descent engine wasn't one of them.

I didn't remember what he was, but I knew he wasn't an engineer(he was a librarian. Thanks, JayUtah).

To be specific he was the head of technical publications and a technical writer. Speaking as an engineer who has spent his career dealing with technical writers: technical writers are not engineers.

Kaysing says he had a security clearance, and I have no reason to doubt him. He would have needed such a clearance in order to handle the secret documents -- even if he didn't understand them.

Finally, IMO, Sibrel needs to get a life. He's young, he's got a chance to meet someone who'll knock some sense into him.

Why would he do that? If he forgot all his moon hoax stuff then nobody would want to interview him. He likes being the center of attention, even if it's to say, "Please oh please oh please buy my video, I've spent half a million dollars on it."

JayUtah
2002-Mar-18, 04:24 AM
Have you thought of producing a video?

Yes, I have. I don't have the skills myself to do it professionally, but I could easily serve as an advisor to a professional filmmaker who wanted to do it. I haven't really pursued any contacts on that.

Right now I'm concentrating on the web site, and I'm beginning a book on the subject of the moon hoax. Perhaps with those accomplishments completed I can attract the attention of a filmmaker -- and more importantly, someone who will pay for it. Producing a video of sufficient quality would be a very expensive proposal.

AstroMike
2002-Mar-18, 04:41 AM
Another of Kaysing's favorite arguments in his own words is: "In the late '50s, when I was at Rocketdyne, they did a feasibility study on astronauts landing on the moon. They found that the chance of success was something like .0017 percent. In other words, it was hopeless." This is nothing but pure crap in my opinion. I think the feasibility studies were done in the mid-60's.
_________________
"The contemplation of celestial things will make man both speak and think more sublimely and magnificently when he descends to human affairs." -Marcus Cicero

<font size=-1>[ This Message was edited by: AstroMike on 2002-03-17 23:42 ]</font>

jrkeller
2002-Mar-18, 05:07 AM
Here's a few things that I noticed.

Kaysing's claim about the descent engine made me laugh. First of all, the temperature of the exhaust products was not 5000F. I believe that the maximum temperature was around 2500F, which drops off after it expands through the engine bell and then into the vacuum.

I think Phil just used the 2500 lbf force on the surface as not to confuse the average viewer. One only needs to go the clavis.org site to see how complex the analysis is. I've sent Phil a few e-mails over the past year or so and I know he knows that all of the 2500 pounds of thrust does not impact the surface.

I also found the NASA ovens to make the moon rocks a real joke. About a year ago, he was on Fox News and said that the moon rocks were meteorites that were collected by Werhner Von Braun when he visited Antartica in Jan 1969. I kid you not.

Even if NASA had the capability to "make rocks" in an oven, here are two things to consider.

1. All of the exposed rocks that were collected have a surface feature called "zap pits." These are micro-craters that are only visible under microscope. I have two geologist friends who have handled moon rocks (using three sets of gloves) and their comment to me was that they know of no way that zap pits can be made on Earth.

2. The claim that the moon rocks were made on Earth and no one could tell if they were from the moon or not is false. During the solidication process, the melt experiences severe natural convection heat transfer (hot parts of the liquid rise and cold parts sink due to buoyancy forces which are dependant on the local gravity field). The shape of the crystalline structure is directly related to this heat transfer process. On the moon natural convection would be much less, since the gravity is less, so the crystalline structure would be much different. Some one with experience could easily tell a fake moon rock by looking at a cross section of the rock.

Just so you know, I did my Ph.D. dissertation on melting and soldification processes.

Maybe it's just wishful thinking, but it seemed to me that PAX let Kaysing and Siebrel hang themselves with thier whacky claims.

JayUtah
2002-Mar-18, 01:32 PM
This is nothing but pure crap in my opinion. I think the feasibility studies were done in the mid-60's.

Some were, no doubt, especially the serious ones intended to explore different long-term plans. But that doesn't necessarily preclude that Rocketdyne and other companies may have done their own studies earlier. The date Kaysing gives for his report is 1959. But unfortunately we are not permitted to examine the report itself. I wonder if Rocketdyne would release it, if it exists. It's not likely to be classified, and they wouldn't give away any trade secrets by doing it.

The problem with any feasibility study done in 1959 is the amount of guesswork that would have to go into it. At that time manned spaceflight was still unrealized. Large-scale boosters had yet to be designed and built. Not much was known about the moon. The authors of such a study would certainly know how confident it was, and how much of the final opinion was based on guesses or estimates that could change radically. But a layman like Kaysing would not necessarily understand what the conclusion depended on.

Whether the report existed or not, it's not unreasonable to suppose that a dismal opinion was floating around Rocketdyne in 1959.

Chuck
2002-Mar-18, 01:49 PM
Well, I'm convinced. NASA faked the moon landings and wrote the bible.

JayUtah
2002-Mar-18, 02:10 PM
I believe that the maximum temperature was around 2500F

The RCS plume deflectors were designed for a temperature of either 1800 F or 2800 F, I forget exactly which. Same fuel, same combustion.

which drops off after it expands through the engine bell and then into the vacuum.

The nozzle ratio alone on the DPS is something like 40:1. So the temperature at the exit plane, ignoring heat loss through radiation and convection to the nozzle itself, will be only a fraction of the chamber temperature.

I think Phil just used the 2500 lbf force on the surface as not to confuse the average viewer.

That would have to be the case. Phil and I discussed this some months ago, before I made the computations, and never reached a precise conclusion about what was an appropriate method. That's what led me to tackle the problem for real on Clavius. At the time I lacked certain necessary values like the mass flow rate and the density of the exhaust product. But after banging my head suitably on the desk I devised methods for reliably estimating them.

Having made those computations (and still refining them), I have no idea yet how to reduce that to a sound bite for a lay audience. A lay audience could be made to understand the concepts without difficulty, but the devil is in the details -- specifically the quantitative details. How you compute the exhaust pressure is largely irrelevant to the debate if you don't put numbers into the computation. And once you start dealing with numbers you've gone beyond the scope of a sound bite on a television show.

Reluctant as I am to exchange one inaccurate model for another, I can't really see how Phil could have made a physically accurate, quantitative rebuttal in the 30-or-so seconds of the average couch potato's attention span. This is why I quibble rather than object.

Inaccuracies aside, I think he touched on the important elements:

1. The DPS had to be throttled down; 10,000 lbf thrust is not appropriate for touchdown.

2. The force is spread out over a 4+ foot circle.

3. Such a distributed force has quantitative paragons in the lay-familiar world.

4. Even if the hoax believers' model of gas impingement were correct, their argument fails quantitatively. This cannot be overestimated. It's one thing to show that their model is incorrect. It's another thing to show that they can't even competently employ their own model.

We have to recall that the hoax theorists have the burden of proof to demonstrate that their expectation of a crater is based on physics and not sensationalism.

As you can see on Clavius I take a progressive approach. My first stab at quantization is simply to compare the LM engine to other engines the layman might be familiar with -- the Harrier, a 747, etc. This helps the reader evaluate the credibility of Kaysing's purported observations. Then there are the more quantitative arguments culminating in the detailed estimates which I assume most readers won't be interested in.

I know he knows that all of the 2500 pounds of thrust does not impact the surface.

As do I. I just wanted to stress the difference between a 2,500 lbf thrust rating, and pressure from the gas on an underlying surface. The two are not equivalent concepts because one derives from momentum (linear treatment of velocity) and the other derives from kinetic energy (second-order treatment of velocity). Even people on our side get this wrong.

The shape of the crystalline structure is directly related to this heat transfer process.

Hm, a few of these concepts are bubbling up through my memory from studying metallurgy in college. I recall that certain alloys (e.g., zinc and aluminum) cannot be made in gravity because of this and similar phenomena. They must be manufactured in the absence of gravity.

Some one with experience could easily tell a fake moon rock by looking at a cross section of the rock.

This is a key argument. Most of the hoax believers don't know anything about geology. And so they don't know what geologists know or how they know it. And upon that basis they make estimations of how geologists could be fooled.

Maybe it's just wishful thinking, but it seemed to me that PAX let Kaysing and Siebrel hang themselves with thier whacky claims.

I wouldn't go that far. Clearly the parting shot was in our favor. Any time you hear someone say, "Nothing will change my mind," you probably have a crackpot on your hands.

Wiley
2002-Mar-18, 02:45 PM
Overall I thought the coverage was fair. It felt like the producers gave Kaysing and Sibrel more air time than BA, but they had to give these guys rope (to hang themselves with). And BA did good job debunking their arguments in the allotted five to ten seconds segments.

This leads to a question. When watching the flag waving segment, the flag waving did not appear to me to be evidence of fakery but just the opposite. The motion of the flag appeared to be a perfect example of wave motion that would result when the astronauts twisted the pole into the ground. You even can see a perfect little whip at the unattached corner of the flag. Now on Earth, with air resistance, can you get this type of motion? I haven't gone out and tried twisting a flag into the ground, but I suspect you will not get this clean wave motion. Comments, anyone?

<font size=-1>[ This Message was edited by: Wiley on 2002-03-18 09:51 ]</font>

GrapesOfWrath
2002-Mar-18, 02:48 PM
On 2002-03-18 09:10, JayUtah wrote:
Inaccuracies aside, I think he touched on the important elements:

1. The DPS had to be throttled down; 10,000 lbf thrust is not appropriate for touchdown.
This point should be hammered at further. In the lunar gravity, the module is, what, 2500-3000 lbs? If the thrusters had provided 10,000 lbs thrust at the lunar surface, it would have taken off again!

Jim
2002-Mar-18, 03:12 PM
I watched (and taped... I may replay it later) the PAX show. It seemed the BA got short-changed some, but I'm prejudiced.

Two quick points:

1) Let's say that Rocketdyne really did calculate the chances of success at 0.0017% in 1959. So what? These are engineers we're talking about. Tell an engineer a problem is almost impossible to solve and all you do is get his juices flowing. The only problems really worth solving are the "impossible" kind.

And, that was 1959. The thing about technology is that it improves over time. (Idle query, what were the odds of successful powered flight in 1893?)

2) Any decent metallurgist or geologist knows all about melt processes and the factors that influence them. Trying to make a "moon rock" in an oven on earth is absurd. Believing it can be done simply illustrates a lack of knowledge of the subject.

JayUtah
2002-Mar-18, 03:17 PM
Now on Earth, with air resistance, can you get this type of motion?

No. I have done experiments with a flag which is as identical to the Apollo flags as can be obtained, and I cannot produce similar oscillations in earth gravity and atmosphere.

JayUtah
2002-Mar-18, 03:25 PM
This point should be hammered at further.

I agree, and I have. I royally pissed off David Percy by performing the physics calculations on his very web site. He edited away my comments and responded thus:

"[A]ccording to the published data, the LM had a descent engine capable of delivering not just 3,000lbs but over 10,000lbs of thrust. Given that weight was an issue, and every component was stripped to the minimum, then clearly the descent engine had a requirement for that amount of thrust to safely accomplish the task. Why is there a need to minimise the amount of thrust?"

Clearly Percy does not understand even the most basic fundamentals of jet propulsion, and therefore he is quite willing to ignore simple computations (i.e., thrust equal to weight) and rest his case on mere handwaving.

Chip
2002-Mar-18, 04:01 PM
On 2002-03-18 10:12, Jim wrote:
I watched (and taped... I may replay it later) the PAX show. It seemed the BA got short-changed some, but I'm prejudiced.


I watched the Bad Astronomer on PAX TV the other night too. As the show progressed, Phil gave very clear and well-thought answers to Kaysing. What a silly, sad fellow Kaysing is - to me at least. I also noticed that Sibrel preferred being interviewed next to some video equipment. (To enhance his credibility?) Of course the editing of the show overall was slanted toward "entertainment" (i.e. keeping the Moon hoax question alive, rather than putting it to rest).

Some years ago, PBS's "Nova" did a wonderful program completely debunking the "Bermuda Triangle" legend. Since then, it hasn't completely gone away, but has diminished quite a bit since the 80s. I hope Nova creates another debunking episode including the Moon hoax stuff, but PBS looks at ratings too, and they won't do that unless the Moon hoax myth becomes more popular.

Andrew
2002-Mar-18, 04:18 PM
Percy: "...clearly the descent engine had a requirement for that amount of thrust to safely accomplish the task. Why is there a need to minimise the amount of thrust?"

I would presume that the engine had that extra capability in case they approached the surface too fast for whatever reason, therefore the seemingly(to some) larger than necessary thrust rating would give some margin for error. Am I correct?

Chuck
2002-Mar-18, 05:02 PM
They could have returned to orbit without touching down if something went wrong, so there was plenty of extra power.

Jim
2002-Mar-18, 05:04 PM
On 2002-03-18 11:18, Andrew wrote:
Percy: "...clearly the descent engine had a requirement for that amount of thrust to safely accomplish the task. Why is there a need to minimise the amount of thrust?"

I would presume that the engine had that extra capability in case they approached the surface too fast for whatever reason, therefore the seemingly(to some) larger than necessary thrust rating would give some margin for error. Am I correct?


Try this Lunar Lander simulator:

http://www.apolloarchive.com/lander.html

Set the controls to Full throttle and leave them there (as Percy seems to think was done). You'll descend about 2,000 feet, and then start climbing again.

If you don't throttle down, you can't land.

Try again, with the throttle set at 50%. You'll descend. Boy, will you descend.

If you don't throttle up, you'll crash.

JayUtah
2002-Mar-18, 05:29 PM
I would presume that the engine had that extra capability in case they approached the surface too fast for whatever reason

Yes. Recall that any spacecraft which burns fuel is thereby a variable-mass vehicle. At the start of the descent the LM is bloated with 17,000 lbm of descent fuel which is 90-95% expended by the end of the descent. The LM sheds nearly half its weight during the descent, much as a launch vehicle sheds weight on the ascent.

In the early stages of the descent the 10,000 lbf thrust would be necessary to produce a suitable change in velocity for the landing profile. As the forward motion of the LM shifts over to downward motion, and the descent engine is more in the conceptual role of carrying weight rather than propelling, by this time it has lightened to the point where the engine must be throttled way back. At high gate I believe the recommended thrust setting was 6,000 lbf, and of course at touchdown in was near 2,500 lbf.

The physics of descent to the lunar surface are very, very straightforward. Purely Newtonian. But the design of a trajectory, profile, and fuel budget are complicated by comparison. Most of us remember the initial "Lunar Lander" video game, a crude affair with a simple lever to control thrust and a knob to control attitude in one axis. The goal, of course, was to touch down with less than 3 fps vertical velocity. But you weren't given enough fuel to maintain 3 fps all the way down. You had to allow faster descent rates higher up.

The same is true for the lunar module. There isn't enough fuel to creep down. So the descent profile calls for fast descent rates at high altitude. The goal is to manage the rate of change in descent rate (the second derivative) so that your descent rate falls below the limit when your altitude is very small. This is all complicated by the fact that the LM is becoming lighter all the time, so you must constantly adjust the throttle.

In Apollo this process was controlled by the computer which had been programmed to vary the throttle to maintain the correct profile of diminishing descent rates. But the pilots also practiced controlling the throttle manually.

The high thrust setting was also useful in the orbital maneuvers that preceded the landing. The LM had to manuever into a precise pre-descent orbit, and it used the descent engine to do this. In orbital mechanics it's less problematic if changes in the velocity state happen quickly, such as would be accomplished by a large engine.

The suitable analogy is the high-performance car. A Yugo's engine is just as capable as a Viper's of holding the car at a particular speed. But a Viper can achieve that speed much faster, and in the space travel world that can sometimes make a big difference.

Wiley
2002-Mar-18, 07:04 PM
I don't know how many of y'all use Matlab, but I'll post this anyway. Richard Gran, one of the guys who designed the LM autopilot, updated the autopilot for Matlab/Simulink. The article can be found here (http://www.mathworks.com/company/newsletter/sum99/lunar_module.shtml). If you have Matlab/Simulink, you can download the Simulink model of the LM autopilot.

amstrad
2002-Mar-18, 07:31 PM
On 2002-03-18 14:04, Wiley wrote:
I don't know how many of y'all use Matlab, but I'll post this anyway. Richard Gran, one of the guys who designed the LM autopilot, updated the autopilot for Matlab/Simulink. The article can be found here (http://www.mathworks.com/company/newsletter/sum99/lunar_module.shtml). If you have Matlab/Simulink, you can download the Simulink model of the LM autopilot.


Being a CS major I found this article fascinating. Thank you.

Oh... an Matlab is a fabulous piece of software. While I don't use it anymore, I used to be an AeroEng major where I used it almost everyday.

Donnie B.
2002-Mar-18, 08:15 PM
They needed the thrust to kill off the LM's orbital velocity. It takes more power to decelerate than it does to merely hover.

There are points during the descent profile when the engine power was much higher than it was just before landing. There's an optimal curve of engine power / fuel consumption.

(Trust me... I'm a veteran of many, many moon landings... on my old TI programmable calculator) /phpBB/images/smiles/icon_smile.gif

I have a question for Jay. I have read (in "Apollo: The Race to the Moon", I think) that there was a "no-abort interval" during the LM descent. For a period of some seconds (maybe half a minute), the failure of the descent engine would have been unrecoverable. Before or after that interval, the descent stage could have been discarded and the ascent engine used to get back up into orbit. But during that interval, the lander was both too low and descending too fast for a successful abort. My question is, was this true, and if so, why? Would the fuel budget have been prohibitively high otherwise?

JayUtah
2002-Mar-18, 09:21 PM
It takes more power to decelerate than it does to merely hover.

Absolutely, especially with all that fuel mass.

There's an optimal curve of engine power / fuel consumption.

Yes, and when you're trying to minimize your fuel load you find and fly that optimal curve.

there was a "no-abort interval" during the LM descent. ... My question is, was this true, and if so, why?

Yes, it's true.

A staged abort is where the descent motor is turned off, the thrust is allowed to decay to zero (to prevent recontact at jettison), the descent stage is jettisoned, and the ascent motor is fired to effect an ascent.

As soon as the descent engine is cut off, any upward thrust ceases. The spacecraft immediately begins to acquire downward velocity at 5.37 fps per second. The staging of the LM is not an instantaneous event, and every second that the LM is in free fall is an additional 5.37 fps that must be arrested and reversed by the ascent motor. Even if the LM were hovering, with no downward velocity, there is an altitude at which it would be too low to effect the staging before it hit the ground.

It is not so much a technical limitation as it is a physics limitation. Pilots face these kinds of limitations all the time. The "dead zone" of the LM is not unlike the decision altitude when landing a conventional aircraft. To land, you must fly low and slow. There is an altitude below which the airplane will not be able to pick up speed and climb before it hits the ground. So when you drop below that altitude you are committed to the landing -- for good or ill.

Having a more powerful ascent engine, or some faster physical means of separating the stages, would reduce, but not eliminate the dead zone. Every craft has an operational "envelope" -- safe boundaries on the parameters by which it operates -- and you have to learn them and avoid passing outside of them.

Donnie B.
2002-Mar-18, 11:40 PM
Yes, agreed. Of course, the possibility of a complete engine failure without any warning was small, especially as the engine was burning for quite some time before they got down to that dead zone.

Also, as I understand it, the descent stage engine was just about a simple as a throttleable rocket motor could be. Less to go wrong.

2002-Mar-19, 03:46 PM
<a name="20020319.9:36"> page 20020319.9:36 aka RED Orange
On 2002-03-17 21:50, JayUtah wrote:
Well done, B.A. <pre>
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hub@hubert.rain.com

<font size=-1>[ This Message was edited by: The Bad Astronomer on 2002-03-17 22:08 ]</font>
[/quote] it takes a lot of lines to do "PAID" so thanks for the memory

Peter B
2002-Mar-19, 10:20 PM
Just a little technical question here:

JayUtah said (in part): "...the rate of change in descent rate (the second derivative)..."

You have:

Displacement;
Speed, which is change in displacement over time; and
Acceleration, which is change in speed over time.

What's the term for a change in acceleration over time?

Andrew
2002-Mar-19, 10:26 PM
I beleive it's called Jolt. Or Jerk.

amstrad
2002-Mar-20, 12:14 AM
On 2002-03-19 17:26, Andrew wrote:
I beleive it's called Jolt. Or Jerk.


it may sound funny, but this is correct.

What is the term used for the third derivative of position? (http://www.public.iastate.edu/~physics/sci.physics/faq/jerk.html)