What relevance would me answering the satellite questions make?
Someone on here said that my claim that a large spy satellite which had been spotted spying over Japan was false and that satellites could not possibly stay stationary over one country.

Ill remind you of what was said.

First of all JayUtah commented that ‘It's not as easy to hide a satellite as Sibrel believes.’

To which I replied :'Perhaps you could tell this to China who only recently discovered a huge American spy satellite watching over them.'

Jay Utah came back with:'Hogwash. Reconaissance satellites are continuously in various altitude orbits at high inclinations, passing over most of the earth's surface at any one time. It is impossible according to orbital mechanics to make a recon satellite "hover" over some particular part of the earth.'

And someone else commented that it would be impossible to position a satellite over one country.

To prove my point and inform you all of the event I not only posted an article by a someone who has worked with NASA in the past, relating to the story, I also posted a link (which I copied and pasted part of) to illustrate that I was in fact correct in believing that a satellite could stay in orbit above a particular spot.

The problem that you pointed out was actually a mistake about geostationary/geosynchronous satellites on the site that I linked to and not my own.

You can hardly accuse me of not answering this particular question.

I have now written to Mr. Oberg to explain further and hope to receive a reply soon.

I hope you'll take his word for it more than mine. check out his website at http://www.jamesoberg.com/


Thankyou

CosmicDave

What relevance would me answering the satellite questions make?

It would substantiate your claim that you actually know something about satellites and orbits.

Someone on here said that my claim that a large spy satellite which had been spotted spying over Japan was false and that satellites could not possibly stay stationary over one country.

No, that spy satellites could not possibly do that. The statement you quote from me clearly establishes that.

... I also posted a link (which I copied and pasted part of) to illustrate that I was in fact correct in believing that a satellite could stay in orbit above a particular spot.

You started talking about spy satellites and then tried to support your statement with evidence that has nothing to do with spy satellites. And if were able to answer the questions I put to you (which you obviously can't) you would know why your examples were irrelevant. But you can't, so you don't.

The problem that you pointed out was actually a mistake about geostationary/geosynchronous satellites on the site that I linked to and not my own.

But you didn't catch the mistake. You reproduced it as if it were God's own truth about satellites. In fact you can't tell which of your sources are reliable and which are not. This is the hallmark of someone dabbling in matters he doesn't understand.

I hope you'll take his word for it more than mine.

But our argument is not with him; it's with you. And you -- not Mr. Oberg -- are the one putting on airs and pretending you know more about these topics than we. Therefore it is from you that we demand explanations.

You have a habit of reproducing other people's arguments without really understanding them. You pretend that parroting them makes you seem intelligent. But as soon as you run into a little trouble from people who do understand those arguments, and in fact know why they're wrong, you try to shift responsibility elsewhere.

You're no different than any of the other conspiracy theorists who tout their iron-clad proof of this or that, but when you ask them a few simple questions to test their knowledge, then out come the excuses why they don't have to submit to such tests. There are those reading here who have in their possession my answers to these questions and who can vouch for my ability to answer them and discuss them (and any others) to any required degree of detail.

You, sir, are a complete fraud and it's been made painfully apparent here. The eight questions I asked you would have taken you less than ten minutes to answer if you really knew anything about satellites or orbital mechanics. And had you been able to answer them, few people would have had cause to further question your expertise. But apparently you prefer to be suspected as a charlatan rather than open your mouth and remove all doubt.

I say put up or shut up.

After having a look about Mr. Oberg's page I can only hope you included a link to your site in your message.
[img]/phpBB/images/smiles/icon_smile.gif[/img]

NO Satellite can maintain position over Japan (without constantly using up maneuvering fuel, and that would run out mighty quick.) Japan is completely north of the equator. Geostationary satellites must remain above a spot *on* the equator, and geosynchronous satellites must balance their time north and south of the equator (a ground trace would look something like the figure-8 of the analemma.)

(Andre Norton, if memory serves, wrote a science fiction novel entitled "World of Three Rings." One cover artist obligingly drew a picture of a world with three separate Saturn-like rings -- stacked parallel to one another like pancakes. This is, unfortunately, wholly impossible!)

Silas

Yes, me and Mr Oberg have had our differences in the past. But, just because we may not have agreed then does not mean that I will just fob off everything he has to say in the future, which seems to be the case with you and me.

This arguement just seems to be going around and around in circles because I drop a little information and then someone says, 'hang on a minute, prove it'. So, off I go, I find an article to answer the persons accusation that satellites cannot hover over a particular place. Then I post an article by a highly qualified person who works in the aerospace industry to substantiate my claim of the spy satellite over Japan, and you still say that I am a fraud.

I want to say at this point by the way that at no point did I or the article I posted mention that the satellite was hovering, it was someone on here who said that a satellite couldn't hover, hence why I posted the article about geostational satellites. The two are unrelated.

I have NEVER claimed that I am a satellite expert, but know from my little knowledge that satellites can stay stationary as is common in the use of TV satellites (of which I commented). It is JayUtah's theory that someone cannot comment if they don't work in that field which is complete crap. I said that a spy satellite had been spotted spying on Japan and I'm then accused of lying.

This is not a lie and I have posted the evidence.

I said 'Perhaps you could tell this to China who only recently discovered a huge American spy satellite watching over them.'

This is the first part of the article again so read it carefully.
_______________________________
Okayama - A group of japanese astronomers watching the heavens around the clock to spot any sign of huge asteroids and comets apparently found an undisclosed spy satellite, they announced Thursday.

The unidentified object was spotted at the Japan Spaceguard Association's observation center in Bisei, Okayama prefecture, in december last year.

Officials of the association said they have since studied a list of over 8,000 man-made objects in space compiled by the north american aerospace defense command (norad), but it was not registered despite its massive size -- the satellite has a diameter of 50 meters.

Aerospace engineering specialist Nobuo Nakatomi said the object was likely to be a spy satellite.
_____________________________

I hope that this fully explains what has happened during this particular subject and that you can see that I have, once again, been misquoted or misunderstood.


Cheers,

Cosmic Dave

Silas,
How does Japan receive satellite TV then if satellites cannot stay stationary above it?

Think about it.

I hope someone on here is going to take him to task like they have me.

[Re c-dave on japanese TV] The satellites aren't above Japan. They're approximately above the equator, and any dish in Japan looking at these birds is looking up and south. The southernmost island in the Japanese chain is roughly 29 deg. North.

[Re the triple-ring planet]Yeah, and in that movie, "Pitch Black", they show a planet with a beautiful (and quite impossible) double-stack ring.

cosmicdave, if you don't want to answer Jay's questions to help establish your bona fides, would you care to answer my one single question about your claim on the AGC?

Yes, me and Mr Oberg have had our differences in the past...
I like that. "The President and I have had our differences in the past..." If pressed, I can come up with a list of other major figures with which I have had differences [img]/phpBB/images/smiles/icon_smile.gif[/img]

<font size=-1>[ This Message was edited by: sts60 on 2002-06-06 17:32 ]</font>

Because the satellite IS NOT hovering over Japan! It is over the equator, but is at such a high altitude, it has an entire hemisphere in it's line of sight. Sure, near the edge of the hemisphere the signal won't be as clear as it would be at nadir.

Jeezzzzzzzz

You really really do NOT get it, do you?

CJSF

__________________
Two years ago moved from my town
I was looking up past the city lights
But the city lights got in my way

See the constellation ride across the sky
No cigar, no lady on his arm
Just a guy made of dots and lines

-from "See The Constellation"
by They Might Be Giants

I would assume a satellite at equatorial GSO would be able to receive and transmit signals from a place as far north as Japan, considering GSOs have to be placed farther out. There wouldn't be a problem with line-to-site.


Adam

Why? He's right, as you would have learned if you had listened to the answers people here were giving you rather than playing a childish game of contridiction and evasion.

Now answer the post above...
I don't see anyone coming forward and agreeing that you all misread what I had to say.

Thats all for now, I haven't the time to stay on here all night and answer questions that you probably wont believe anyway.

Goodnight.

CD, you have this annoying habit of dragging the discussion, kicking and screaming, away from the topic at hand when you are stuck.

Allow me to drag it back.

You and your ilk say humans cannot travel beyond the Van Allen belts. Because of this and other factors, NASA decided to fake the lunar landings by leaving the astronauts in orbit during the flight. However, we then point out that it would impossible to put something as large as the CM into orbit without it being seen.

You then come up with "proof" that something can be hidden in orbit, a news article that states Japanese astronomers have found a spy statellite in orbit, the launch of which was never reported.

My first thought is that your article proves our point, in that a secret spy satellite is discovered in orbit, easily seen in binoculars, no less.

But then you launch into a lenghty diversion discussing geosynchronous satellites (incorrectly), but never coming back to the original problem, which is, how to hide the CM in orbit.

So now the ball is in your court. All you have to do is tell us how NASA hid the spacecraft.



<font size=-1>[ This Message was edited by: Tomblvd on 2002-06-06 17:45 ]</font>

Yeah, I just bet you have.

BTW, did anyone else notice that Mr. Oberg had "Bad Astronomy" as the third listing on his links page? [img]/phpBB/images/smiles/icon_smile.gif[/img]

Hi, John,

Gotta quibble a bit here.

First, the Saturn 5 did in fact have its own independent guidance system (though I don't know if it used a computer exactly like the AGC or some other approach). The S-V did in fact control its own flight from liftoff to orbit without the need for ground control (though the controllers could intervene and override if necessary). The first couple S-V launches were unmanned and got themselves into orbit just fine (despite the fact that they had some serious engine problems on the second and third stages).

Second, the launch of a booster from pad to orbit is most definitely *not* a descent run backwards, except in the trivial sense of "running the film backwards". Not, that is, unless you can figure out a way for the booster to steadily fill its fuel tanks as it descends!

But I undestand that you were referring specifically to the problem of guidance. I submit that the S-V had more than enough "intelligence" to control its attitude and trajectory during launch, but I wouldn't try to argue that this is a problem equivalent to performing a landing.

OK, looked around and found the source article. It was not written by James Oberg, but as far as I can tell was from the newspaper Manichi Shimbun, April 4:
http://mdn.mainichi.co.jp/news/archi...dm024000c.html

This article claims a "diameter" of 50 meters, which is ridculous. A satellite might have a solar array span around that big, though.

- If the bird is "visible in the southeast sky", then it is a geosynchronous satellite.
- If they didn't just make a mistake with a commercial comsat, or some sort of weather satellite, then it could be a secret bird.
- It's not an imager if it's a classified bird in geosynchronous orbit. It could theoretically be a sigint (doubtful), or perhaps an IR warning satellite like DSP.
- At best, cosmicdave's assertion that it is "watching over" Japan (he corrected himself, then switched back and forth in later posts) is a funny way to say it. A geosynchronous bird "watches over" a big chunk of longitudinal hemisphere, not just one little island chain.Jay pointed out that reconnaisance satellites (a term which generally refers to high-resolution imagers) are moving in low orbits. To someone unfamiliar with satellite operations, I concede this might sound like "satellites can't stay over one spot". In any case, this satellite is not really over Japan. But let's move on.Well, the article wasn't by someone who worked with NASA in the past; it wasn't written by James Oberg. A satellite can't stay in orbit over any particular spot, only ones over the equator (roughly speaking).

Cosmicdave, you incorporated the quoted article into your argument. It's not nice to blame your source for a mistake. And, in fact, the article didn't make any explicit mistakes of fact other than the "50 meters" figure.

Yes, you did answer the question, after a fashion."Geostationary", not "geostational". But that's not the same thing as "geosynchronous". Anyway, to repeat, the article was not by James Oberg as you alleged, and the satellite wasn't really over Japan.

No one here has called you a fraud. But your arguments and knowledge of the topic are faulty.You have repeatedly belittled the knowledge of people who are for-real satellite experts. This tends to come across as someone who thinks they know better, i.e., who thinks they themselves are a bigger expert.

Jay has not said that people can't comment if they don't work in a field. But he has pretty much said that people need to know what they're talking about if they dispute an expert's opinion on a technical matter in that expert's field.

Your post about the satellite isn't a lie, but the article doesn't really support your contention that the bird is "spying on Japan". Maybe it is, but what I've read about it suggests that at most it's gathering signals or looking for launches over a vast region, far larger than Japan.

Going back to what started it all:
cosmicdave brought up the "spy satellite" as support for the notion that Apollo radio transmissions were faked by an Earth-orbiting (non-translunar, Jay!) satellite. We have pointed out that that is physically impossible. So whether or not it's easy to "hide" a satellite in LEO, or GEO, is a moot point anyway.

cosmicdave, now that I have answered your post per your request: Do you now understand that Apollo radio signals could not have been faked by such a satellite?


<font size=-1>[ This Message was edited by: sts60 on 2002-06-06 19:21 ]</font>

Donnie B., I know, I know. Maybe I should have said similar problem. The similarity is that the vehicle was to follow a predefined path. The guidance system of the Saturn V also have to control 11 different engines, staging, avoiding the tower, wind sheer, etc. It also had to correct for premature engine shutdowns, plus various abort modes. Nobody seems to question that the Saturn V could get to orbit, even the HB's. With this complex system, the SIVB plus the CSM and LM had to get to a certain height, at a certain speed and in a certain direction. Add to this the complexity of having to respond to the lightening fuel load, and it's no mean feat.

The AGC on the LM had to control a single engine, following a predetermined path, allow for fuel use, conpensate for fuel 'slosh' (on 11), and arrive somewhere near the lunar surface with enough fuel to land and not too fast. All this with no wind sheer, and minimal abort options (basically, cut loose the descent stage and haul a** back to orbit). To my mind, getting a Saturn V into orbit automatically (which the HBs admit is possible) is much more difficult than landing on the Moon with the help of the AGC.

How odd. Most HBs seem obstinate and incorrect, but this is the first one I can recall who actually seemed incapable of grasping simple concepts. The rest of them at least argue that physics is wrong or something that lends an air of internal consistency.

CD seems like he's honestly too stupid to understand.

I apologize for what would be ad hominem in a debate. But this isn't a debate. It's really quite painful to read.

I now find myself wondering... I'd assumed HBs were simply deluded or misinformed. I surely did not know how to answer all their arguments prior to coming to this site. I hadn't considered the possibility that some of them are simply incapable of learning.

What a depressing thought.

(Ss this is rather un-astronomy related, feel free to delete it if it is deemed inappropriate. I will do so myself if others (besides CD) wish.)

While it is a touch ad hominem, it's true...

In terms of general rhetoric, there are lots of ways to be wrong. Since I spend a lot of time doing exactly that (i.e., being wrong) I've found the best approach is to admit it, apologize, learn the lesson, and move on.

That is morally difficult for some people; instead of attributing it to stupidity, I think it should be seen as a moral stance. Sort of like John Wayne never backing down from a gunfight in a movie...

I was once in a political discussion where someone said that a candidate had won a "majority." In fact, it had been a plurality. No big deal, right? The guy refused to accept his error. He went down fighting. No dictionary citation, no political resource, no one's word was good enough. He was actually trying to redefine the word to his own meaning rather than merely acknowledge a trivial error, for which anyone would readily have forgiven him.

It doesn't have much to do with astronomy, or even science, but it is at the heart of civil debate, and it also cuts very deep into the issue of the role of public discourse in the pursuit of truth.

Our good host, the Bad Astronomer, has banned people for saying, "You fool," but never for posting foolish ideas. The former is moderation; the latter is mere censorship.

(By the way, the world is flat. Just thought you'd like to know...) (grin!)

Silas

cosmicdave,

back on the locked thread you told me to go look up your explanation as to why the guidance computer could not have done its stated job. Sorry, but I missed that initially. Since then, I have looked on your site, and this is what I found:

28) In 1969 computer chips had not been invented. The maximum computer memory was 256k, and this was housed in a large air conditioned building. In 2002 a top of the range computer requires at least 64 Mb of memory to run a simulated Moon landing, and that does not include the memory required to take off again once landed. The alleged computer on board Apollo 11 had 32k of memory. That's the equivalent of a simple calculator.

This is not an explanation, but rather a statement of personal incredulity. This is inadequate for convincing those of us with actual flight computer experience. Do you actually have an explanation on your site, or anywhere else, that I missed?

28) In 1969 computer chips had not been invented. The maximum computer memory was 256k, and this was housed in a large air conditioned building. In 2002 a top of the range computer requires at least 64 Mb of memory to run a simulated Moon landing, and that does not include the memory required to take off again once landed. The alleged computer on board Apollo 11 had 32k of memory. That's the equivalent of a simple calculator.

A Moon landing simulator, such as the excelent EL3D, uses lots of computer power because it's having to simulated the environment and the hardware as well. Look at driving sims. They require loads of memory and a fast vid card, because all the terrain and the behaviour of the car has to be generated by the computer, as well as any 'control' software. My own car has no computer. The engine is made of metal. It makes it's own noise. The steering wheel is connected to the front wheels mechanically. Cables operate the throttle. Hydraulics operate the brakes. My own mid eared computer supplies the navigational data. The landscape I drive through is supplied by an outside contractor.

This is one of CDs sillier arguments.

I find an article to answer the persons accusation that satellites cannot hover over a particular place.

I said reconnaissance satellites cannot hover over a particular place. Your article talks about a completely different type of satellite. You cannot seem to demonstrate that you know the difference between them and why they're different. As usual, you're simply pulling up something you think is relevant, but which has nothing to do with what you're talking about.

Then I post an article by a highly qualified person who works in the aerospace industry ...

You have no idea what his qualifications are, and you wouldn't answer my questions regarding them. U.S. reconnaissance satellite technology is some of the most closely guarded technology that exists. Yet some guy over Japan is all of a sudden an expert in it? How did he acquire his expertise?

Further, just about the only thing that we know about those satellites is their size and mass. And that doesn't resemble the description.

Further, the "expert" gives an opinion which is thoroughly disproven by every single orbital mechanics textbook that exists, and principles of physics that go back to Kepler!

Had you been thinking critically and had you known anything about the sciences involved, you would have been able to evaluate the reliability of this "expert's" opinion. Not only do you seem uninterested in thinking critically yourself, you seem uninterested when other people try to do it for you.

... at no point did I or the article I posted mention that the satellite was hovering

The article said specifically that the object could be seen with binoculars or the naked eye in a certain specific place in the night sky. You don't say something is in a certain place if it's whipping from one horizon to another in a matter of two or three minutes.

Further, the whole issue arose from your argument that a low-earth-orbiting satellite could be made to appear in the same place in the sky, and that the command module could orbit unseen.

Further, you still haven't told us how something in geostationary orbit can be seen from earth.

You're simply in way over your head here, and it's time to admit that you really don't know what you're talking about. E.g.,

I have NEVER claimed that I am a satellite expert, but know from my little knowledge ...

From your "little knowledge" you presume to pass judgment on whether anyone else is a satellite expert. That's pure arrogance, and it brands you a crackpot.

And you don't seem very interested in acquiring any more knowledge about satellites or orbits, yet you insist on talking about them and insisting that you're right.

It is JayUtah's theory that someone cannot comment if they don't work in that field which is complete crap.

I'll be the judge of what is and is not my theory, thank you.

I have no problem with you commenting on whatever you want. I have a problem with you treating people arrogantly when they take issue with your frequently ignorant statements, and with simply insisting that you're right despite all educational efforts to point out your mistakes.

I have a problem with you calling others' knowledge and expertise into question when you aren't qualified to judge them.

As I said, I will be happy to explain anything you want about these topics, so long as you refrain from your arrogance and from simply trying to "score" off me.

I said 'Perhaps you could tell this to China who only recently discovered a huge American spy satellite watching over them.'

But the "this" you're talking about is the general subject of orbital mechanics and trajectory as it relates to how the Apollo missions may have been falsified, and the specific subject of whether you can hide something in orbit.

Then it turns out the evidentiary value of this entire statement turns out to hinge upon one person's opinion which makes no sense. And when we tried to explain to you why it made no sense, you went off on your little tantrum about how little you thought I or anyone else here knew about satellites.

I hope that this fully explains what has happened during this particular subject and that you can see that I have, once again, been misquoted or misunderstood.

It does not fully explain anything. It only supplies a revisionist attempt at an excuse for your arrogant behavior. You questioned my understanding and expertise, when now by your own admission we discover that you are the one who has little expertise. I think an apology from you is in order.

Since you admit to knowing little about satellites, I do not accept any of your arguments regarding whether any sort of orbiting unmanned spacecraft could be or was used as a communications relay. I reject your argument that the CM could have remained unnoticed in low earth orbit.

If you would like to supply arguments to support these claims, I will hear them.

How does Japan receive satellite TV then if satellites cannot stay stationary above it?

Research the answers to questions 1, 5, and 8 and you'll have your answer.

Think about it.

I assure you I have expended considerable thought toward this problem.

I hope someone on here is going to take him to task like they have me.

I assure you I am taken to task here when I am wrong. This is what separates we "skeptics" from conspiracy theorists. You like to call us a bunch of back-patters, but in fact we quite happily find mistakes in each other's statements and arguments.

However in this case I am not wrong.

I haven't the time to stay on here all night and answer questions that you probably wont believe anyway.

Well, I understand taking the night off. I myself took a nice brisk hike up in the mountains. It's not so much that you don't post much. It's what you choose to say when you do post.

You'll find people here will believe you if:

1. you provide clear, well-reasoned, logical arguments for your points,

2. you refrain from arrogance (and I will do the same),

3. you make a clear distinction between what is your opinion and what you believe can be shown objectively,

4. you respect the expertise of your opponents,

5. you accept the possibility that your statements may be proven wrong.

First, the Saturn 5 did in fact have its own independent guidance system (though I don't know if it used a computer exactly like the AGC or some other approach).

Some other approach. The LVDC was a digital computer which operated through a series of controllers to manage things like flight dynamics, environment, and staging.

It was not generally considered a good idea to slave the Saturn V to the Apollo spacecraft guidance system because the Saturn V design presumed it would operate also with "dumb" payloads.

The LVDC is a major improvement over prior rockets in trimming the development schedule. The computer and its sensors and telemetry could essentially carry on a conversation with ground computers and this greatly simplified diagnosing problems.

This article claims a "diameter" of 50 meters, which is ridculous. A satellite might have a solar array span around that big, though.

Not really. The "wings" on the Boeing 601HP -- the current workhorse of the comsat industry -- are 26 meters from tip to tip.

The biggest reconnaissance satellite uses an AFP-5500 bus/chassis to house the KH-11 optical system. Based on photogrammetric measurements of the shipping container, it can be no longer than 43 feet, and based on photogrammetric measurements of the payload shrouds during launch it can be no longer than 48 feet. (This is obviously unreliable data since the manufacturer will confirm only very rough statistics on the APF chassis.)

If the bird is "visible in the southeast sky", then it is a geosynchronous satellite.

And therefore too far away to see with either binoculars or the naked eye. This begs the question of whether it's a satellite at all.

To someone unfamiliar with satellite operations, I concede this might sound like "satellites can't stay over one spot".

Agreed, but I chose my words carefully in order to accurately represent my intent. It was clear C. Dave intended to discuss a recon satellite, and I made a specific assertion about recon satellites. C. Dave ignored my careful wording and brought up an irrelevant counter-example. That would have been a simple mistake, easily corrected. But C. Dave chose to carry his argument further and verbally hop around with glee at the belief he had outsmarted me.

It's not nice to blame your source for a mistake.

Except that I did quote his excerpt in a manner which might indicate I believed it came from him. As I've explained, I know it was from an external source. But we know it was not a reliable source because it got a simple fact wrong. In turn, C. Dave did not catch the error, meaning he wouldn't necessarily have known whether an external site on this subject was authoritative or relevant.

No one here has called you a fraud.

Not true. I called him both a fraud and a charlatan. I regret the ad hominem sentiment and apologize for any offense. By that statement I meant simply that I believe C. Dave is pretending to be something he's not. He wants to be perceived as some kind of expert or authority on matters involving Apollo, when he clearly is not. Further, he demonstrates no small animosity toward genuine expertise, and this behavior could be interpreted as intentional concealment.

Jay has not said that people can't comment if they don't work in a field. But he has pretty much said that people need to know what they're talking about if they dispute an expert's opinion on a technical matter in that expert's field.

Thank you. I'm glad my "theory" is apparent to at least one other person.

So whether or not it's easy to "hide" a satellite in LEO, or GEO, is a moot point anyway.

Well, yes and no. It's irrelevant to the point of whether a spaceborne relay could have been used. It's not irrelevant to whether the CM with the astronauts in it could have been in low earth orbit, hence the blue glow.

In his post dated 2002-06-06 16:40, Cosmicdave wrote:

"geostational satellites"

Good grief. Not only does he know NOTHING about satellites and orbits, he can't even get the terminology right. That other bit about Japanese TV was priceless. He just digs a bigger hole for himself every time he postulates nonsensical garbage like that. Dave, you seem to be on an endless quest to parade your ignorance in front of the entire board and anyone else who might be reading. You are clearly a man of incomparable stupidity. Guys, maybe it's time we washed our hands of this babbling waste of cyberspace. (apologies BA, if this is too harsh - but this guy is getting really tedious).

JB

(edited to add date of quote and corr. sp)
_________________
"Nowhere in all space or on a thousand worlds will there be men to share our loneliness..."

- Loren Eisely, "The Immense Journey" 1956


<font size=-1>[ This Message was edited by: Jovianboy on 2002-06-07 00:01 ]</font>

Back to computers, eh?

(Quoting C. Dave)
In 1969 computer chips had not been invented.

Depends on what you mean by "computer chips". Integrated circuits were invented at about the same time Kennedy issued his challenge to go to the moon. By 1965 they were a product line you could order out of a catalogue. By 1968 commercial computers made from integrated circuits were easily available. In fact, by 1969 the AGC was no longer state of the art. That's because manrated computer designs have to be frozen early for testing.

The maximum computer memory was 256k

No. The IBM 360 could have as much as a megabyte. In any case, this is largely irrelevant because a guidance computer doesn't need a lot of RAM. The program is not stored in RAM, and only needs RAM to hold the state vector and any intermediate results that can't be stored in registers or in the ALU.

The Polaris Mark II digital guidance computer (1961) had 12 words of RAM. Not kilobytes, not megabytes -- 12 14-bit words. It worked just fine and was entrusted with the guidance of a nuclear warhead.

and this was housed in a large air conditioned building.

Not in a building, but in a room. And if you walk through that room and look at what those big boxes are for, you'll find that most of them have nothing to do with a guidance computer. Those boxes are disk and tape drives for storing and reading back large amounts of data, controllers, printers, and various input/output devices.

The aforementioned Polaris Mark II is smaller than my laptop.

I remember writing programs on punch cards in Fortran on a 4-megabyte machine, uphill in the snow both ways. I can vouch for what we could make those beasts do.

In 2002 a top of the range computer ...

... is completely irrelevant to the problem of guidance computers. Comparing special-purpose and general-purpose computers is worse than apples and oranges.

requires at least 64 Mb of memory to run a simulated Moon landing

Thanks to overly complicated operating systems and wasteful programming practices. Not to mention the demand from users for photo-realistic, texture-mapped simulation.

This question can be dismissed simply on the basis that realistically simulating a dynamics problem in full whiz-bang mode is much more difficult than controlling an actual spacecraft in the actual dynamics situation.

In any case, it's completely backwards to say "it takes" 64 MB to support a lunar landing simulation. It's more accurate to say the programmers of today's lunar landing simulations know their programs will be running on a machines with around 64 MB of memory. Today's computers are much more powerful, and so today's software developers add more bells and whistles.

It takes many megabytes to run Microsoft Office, but I can remember doing similar tasks on personal computers that could have no more that 640 KB of main memory. The programs then were primitive in comparison, but that's not the issue. We got by -- that was the issue. The features of the software were dictated by the features of the hardware.

I've been doing a lot recently with microcontrolled embedded systems. We can cram a great deal of functionality into a very small amount of memory by ommitting irrelevancies like scanner drivers, AOL Instant Messenger, MS Windows, and the host of other cruft that clogs the typical home system.

that does not include the memory required to take off again once landed.

But would that have required, say, twice as much memory? No, of course not. Maybe a smidge more. More likely the programmer simply didn't want to program an ascent because the descent took long enough.

The entire argument smacks of someone who doesn't really know much about computers. Laymen have a real problem trying to characterize the performance of their computers in meaningful and accurate terms. They believe things like a 32 MB computer is only half as "powerful" as a 64 MB computer. Or that they can directly compare the performance of an X MHz PowerPC and and X MHz Pentium by comapring the megahertzage.

The alleged computer on board Apollo 11 had 32k of memory. That's the equivalent of a simple calculator.

No, a "simple calculator" is the four-function beast I bought in 1973 for $100. Today's calculators and PDAs have huge memory sizes and sophisticated programming, but again we're talking about apples and oranges.

The final AGC model had 36,864 words of read-only "rope" memory and 2,048 words of magnetic core RAM. (A word had 15 significant bits.) It was built with about 5,000 integrated circuits.

This configuration is very consistent with the design of an embedded system, and with a digital autopilot specifically. You want lots of ROM to hold the program, and just enough RAM to hold intermediate results.

Now I have a printed copy of the AGC source code, and I can verify that it does what it says it does and that it would fit in 36 K words.

C. Dave will have to prove to me that what I can see with my own eyes is wrong.


<font size=-1>[ This Message was edited by: JayUtah on 2002-06-09 21:58 ]</font>

Oh, man, you're taking me back! 1973, a TI calculator, with a Square Root function! I was in heaven!

I used it to simulate orbits, using the very, very simplest model of duplicating the previous velocity vector and adding a gravity vector. I drew the niftiest little ellipses and occasional hyperbolas.

Our cosmic correspondent could do better with a four-banger with square root, and an honest approach to the facts, than with the entire resources of the internet and a closed mind.

BTW, I think I know most of the answers to your quiz on orbits, but there were a couple of questions that I might have gotten wrong. Post the answers, please!

Silas

Okay, C. Dave has indicated he has but a "little knowledge" of satellites and doesn't appear to want to tackle my questions. I guess that means we can roll out the answers now for those of you playing at home.

1. What is the orbital velocity of a 4,000 kg satellite in geostationary orbit?

First, disregard the mass -- it's a decoy fact and doesn't affect the answer. But the notion that it does matter is one of the common mistakes made by novices. If the mass of satellites in identical orbits affected the velocity, all those communication satellites, all with different masses, would be bumping into each other.

There are a couple of ways you can compute the answer. By far the easiest is to note that it's a circular orbit with a known size and period. It's basic circular motion.

Now there are two gotchas in this problem. At first you'd be tempted to compute the circumference of a circle whose radius is 22,236 miles and divide that by 24 hours.

Unfortunately the magic number of 22,236 miles is the altitude of the orbit above the earth's surface, not its radius. To get the radius of the circle you have to add the equatorial radius of the earth, generally 3,693 miles for a grand total of 26,199 miles. The circumference is 164,613 miles, to the nearest mile.

So divide by 24 hours, right?

Not quite. That's a solar day, the amount of time in which the earth rotates to the same position relative to the direction of the sun. But because the earth scoots along its orbit about a degree in that time, a solar day is actually about 361&deg; of rotation.

If you measure the rotation relative to a distant star, you get closer to the amount of time it takes for exactly 360&deg; of rotation. And that's the measurement you're after. You want the satellite's orbit to exactly match the actual rotation of the earth, not the rotation we perceive from its surface relative to the sun.

A sidereal day (the true rotation) is about 23 hours, 56 minutes, and 4 seconds long, or 23.9344 hours. Thus the orbital velocity of any satellite in geostationary orbit is 6,877.67 miles per hour.

2. Name a satellite which is in geosynchronous, but not geostationary, orbit. Also, name a satellite which is in geostationary, but not geosychronous orbit.

There are dozens and dozens of satellites in geosynchronous but not geostationary orbits. Most notably are the NASA TDRS satellites. This was a simple matter of looking something up and knowing it when you see it.

The second part of the question is a trick question, obviously. All anyone had to do to answer this one correctly was pay attention to my prior post where geostationary was defined as a subset of geosynchronous. Therefore there can't possibly be -- by definition -- a geostationary satellite that is not also geosynchronous.

3. During insertion in geostationary orbit, why does the COP manuever come after the transfer manuever?

Launching a satellite into geostationary orbit from, say, the Kennedy Space Center involves first boosting the satellite into a parking orbit, transferring to an orbit of appropriate altitude, circularizing that orbit, and then shifting the plane of the orbit to be coincident with the equator. In modern launches some of these steps can be combined. But you still have to know what each step accomplishes.

Theoretically you could do the "change-of-plane" (COP) while in the parking orbit, then transfer out to geosynchronous altitude and circularize. Novices will intuitively select to do it that way, but it's bad.

The foremost rule of orbital mechanics is that altitude and velocity are very strictly connected. Kepler's third law covers this. The lower the orbit the faster the orbital velocity.

Two different orbital planes will intersect at a line, and that line will intersect the initial orbit (parking orbit in this case) at two points (see below). You change planes at one of these points by simply burning the engine to adjust the velocity vector at that point so that it now lies in the desired orbital plane.

You can do this with simple velocity vectors. If you launch into a 32&deg; parking orbit from KSC and want to go into equatorial orbit, the starting vector points up (or possibly down) at 32&deg; and the desired velocity vector would be of that same magnitude, but at a 0&deg; angle. Subtract the vectors and that gives you the direction of the velocity change.

Now in a parking orbit of around 17,000 mph (at typical shuttle altitude) a plane change of 32&deg; would require a correction vector with a magnitude of about 9,000 mph.

If you wait until you're out in geosynchronous orbit and circularized, the same plane change to geostationary orbit would require a burn of only 3,791 mph magnitude.

So the answer is that you do the burns in that order because the COP will then require only about a third the fuel as doing it in parking orbit.

4. Two satellites are to be place in a circular low earth orbit at exactly the same altitude. One has a mass of 1,000 kg. The other has a mass of 3,000 kg. Which one must orbit faster in order to retain its orbit?

Another trick question, but one easily answered by anyone who has made any reasonably serious study of orbits. The mass of the orbiter does not determine its velocity, only its altitude. The answer is that they will orbit at exactly the same velocity.

The issue of altitude versus velocity is a key concept in understanding why LEO orbiters cannot "hover".

5. What is meant by "orbital inclination"?

We have already used this concept in connection with the change-of-plane discussion. Every orbit lies in a plane that passes through the center of mass of its primary. It cannot be otherwise.

The inclination of an orbit is the angle that its plane forms with a reference plane that also passes through the primary's center of mass. For earth orbits we use the earth's equator as the reference plane.

The latitude of the launch site determines the minimum inclination of the initial orbit. By launching due east you establish an orbit whose inclination is identical to the latitude of the launch site. Varying the azimuth north or south increases the inclination in both cases. If you want a smaller inclination you must do a plane change after the orbit is established.

At least one KH-11 reconnaissance satellite is in a 97.1&deg; orbit. It may seem odd to have an inclination greater than 90 degrees, but this indicates a retrograde orbit. Spy satellites orbit "backwards".

The ISS is in a 59&deg; orbit so that it can be reached easily from Russian launch sites, which are at a higher latitude. This requires a northeastern launch trajectory when the space shuttle rendezvouses with it. (Bonus question: Why wouldn't a southeastern shuttle launch trajectory work?)

The inclination and altitude determine the satellite's ground track, which in turn determines the ephemerides (risings and settings) visible from some point on earth. An LEO orbiter that passed over Japan would be in a fairly high inclination orbit. Geostationary satellites are in an orbit of zero inclination.

6. What are the two nodes of an orbit?

Again, we have already used this concept. Two different orbital planes intersect at a line, and that line intersects the orbit at two points. Those are the nodes. There is an "ascending node" and a "descending node", depending on the direction of the passage through the reference plane.

The nodes are important because there is obviously an infinite number of orbits of a particular inclination. Inclination and the direction of the nodes are two of the parameters used to describe orbits uniquely.

7. Name two methods for circularizing an elliptical orbit.

1. Posigrade in-plane manuever at apoapsis (the "apogee kick").

2. Retrograde in-plane manuever at periapsis.

The choice depends on which apsis is at the desired orbital altitude. The magnitude of the manuever is that required to produce a delta-v computed from the actual velocity at that point and the theoretical velocity of a circular orbit with that altitude.

8. What is the relationship of an orbit's major axis to its period?

We have answered this above. Kepler's third law strictly relates an orbit's altitude to its period. The major axis (radius, in the case of circular orbits) relates to the altitude. That would have been a sufficient answer.

The exact formula is

P = ( ( 2 * pi ) / sqrt( mu ) ) * a^(3/2)

where P is the period, a is the semi-major axis (one-half the major axis), pi is the customary value, and mu is the gravitational parameter of the earth: its mass times G, the universal gravitation constant.

So how did everyone do?

Better then I expected to. Nos. two, four, five and six right and two questions wrong (nos. one and eight) that I'm kicking myself for.

Thanks for that! Very well explained and I learned quite a bit.