Shenzhou 7?

[Jason Thompson]

Exactly. What most HBs fail to grasp in addition to that is that some things [/i]do[/i] still work the same way. To them it's an either/or situation. Either everything works the same way or nothing does, and hence when we say their understanding of, say, interpreting how far something on the Moon is in the absence of familiar cues is flawed, and then go on to describe the behaviour of light, they act incredulous that we can say on the one had that standard familiar things don't work and then on the other hand use a standard familiar thing to make another argument.

[Donnie B.]

bobdude,

Don't be fooled by the tides, which are often (misleadingly) described as being caused by the Moon's pull on the Earth.  In fact, the tides are caused by the gravity gradient, similar to the effect on long objects that Jason mentioned.

In fact, tides are a pretty interesting thing to learn about.  The Earth causes tides on the Moon, too, and the Moon's tide affects the solid rock of the Earth as well as the oceans (just not as dramatically).

[ka9q]

you know, I was thinking - with the relation of the ship to the Earth in the video (Earth 'above' the Astronaut), wouldn't the pull of Earth's gravity cause these items to 'float up'?

As Jason Thompson pointed out, there is something called a "gravity gradient". It is present only when you're close to a massive body (e.g., in low earth orbit) and even then the effect is very small. It tends to cause a long, skinny object to orient itself along the local vertical.

Probably the best known (and certainly one of the largest) gravity-gradient stabilized object is Luna, our moon. It has aligned one of its axes along the earth's gravity gradient so that one side always faces the earth.

This is why NASA refers to the environment on the ISS (in a very low earth orbit) as "microgravity" rather than "zero gravity". Only points at the same altitude as the ISS's center of mass are in true free fall. A point on (or in) the ISS at a higher altitude would tend to orbit slightly slower and a point at a lower altitude would tend to orbit slightly faster but they're all dragged along by the rigid structure. This slight force is experienced as "microgravity".

Some spacecraft are gravity-gradient stabilized, a few deploy a mass on the end of a long boom to increase the effect. It can be tricky because there's no atmospheric friction to stop oscillations, so some sort of active damping is required.

[bobdude11]

 This is why I come to this site. I learn more in one or two posts from the experts than I believe I can with a Google hunt …

[gwiz]

It can be tricky because there's no atmospheric friction to stop oscillations, so some sort of active damping is required.

Damping can be passive, for instance using magnetic materials that slow the oscillations as they move through the earth's field.

[cjameshuff]

Damping can be passive, for instance using magnetic materials that slow the oscillations as they move through the earth's field.

Or internal friction/mechanical hysteresis. A lossy spring will do the job even in high orbits or orbits around bodies that lack strong magnetic fields.

[ka9q]

I'm not up on the latest implementations, but back in the early 1980s the UoSAT-Oscar-9 spacecraft had a boom and mass to attain gravity gradient stabilization. I remember them having a lot of trouble trying to damp out the oscillations. Maybe it's gotten easier since, especially with better on-board computers and attitude sensors. I should look at this again.

[cjameshuff]

I'm not up on the latest implementations, but back in the early 1980s the UoSAT-Oscar-9 spacecraft had a boom and mass to attain gravity gradient stabilization. I remember them having a lot of trouble trying to damp out the oscillations. Maybe it's gotten easier since, especially with better on-board computers and attitude sensors. I should look at this again.

From what I've found, UoSAT 1/Oscar 9 had a deployment failure...a magnetometer cable snagged and prevented the gravity gradient boom from extending. It and UoSAT 2 used active damping via electromagnets, and I haven't found anything indicating unusual troubles with the system.

[ka9q]

I think you're right -- it's been a while. Active damping did help a lot on the later Surrey spacecraft.

[ka9q]

This is a topic I'm still interested in, as many small amateur satellites are still flown with little or no attitude control capability. This forces the use of simple antennas on the lower VHF and UHF frequency bands, and while they're nominally omnidirectional in fact they tend to have some rather deep nulls. This has forced me to make my modulation and error correction schemes extremely robust against fading, and that comes at a cost in data rate.

If we could cheaply and reliably keep one side facing earth at all times, we could use more directional (i.e., higher gain) antennas on the microwave bands and achieve much higher data rates.

[gwiz]

From what I've found, UoSAT 1/Oscar 9 had a deployment failure...a magnetometer cable snagged and prevented the gravity gradient boom from extending. It and UoSAT 2 used active damping via electromagnets, and I haven't found anything indicating unusual troubles with the system.

Apart from the boom failure, it suffered early comms problems which prevented commands being sent for several months.  In all, it took about a year to achieve stabilisation.

[cjameshuff]

If we could cheaply and reliably keep one side facing earth at all times, we could use more directional (i.e., higher gain) antennas on the microwave bands and achieve much higher data rates.

One of the harder problems is that a gravity-gradient stabilized craft has two stable positions, and it's a bit tricky to get it to settle into the desired one. However, even if you let it flip into one of the two orientations at random, this could still be used to keep nulls in the pattern away from the ground and allow use of an antenna with some gain...

[VincentMcConnell]

Greetings to the people of the ApolloHoax.net forums. There are a few reasons I am posting here today, and I feel it necessary to make a long, official statement of sincerity for actions taken many, many months ago.
My name, as you know, is Vincent McConnell and I was once a poster here on these forums. However, things became complicated, as can be seen in the contents of this thread, and I left under the context that I didn't want to deal with this anymore. To let the record state, I never conducted any experiments concluding any one stance on the Chinese Space Program and its missions. So before I am asked how "that underwater experiment went", I want to announce publicly that no such experiment ever took place. Regardless, I feel it has become necessary to make my official statement here, where I was kind of "run-off" the forums. I lost interest in the Chinese space program and the arguments surrounding it many months ago and my position on the Shenzhou missions (even to me) has become completely irrelevant. Whether China put a man in space or not, I simply don't care. There are a number of people who were personally offended by remarks I made questioning their scientific integrity, and for each and every one of those remarks, I officially apologize and ask for forgiveness. I was in a "conspiracy mood" at the time and no longer agree with statements made that directly insult or offend another user of these forums.
Apollohoax.net for me is about Apollo, and I have chosen to keep it that way. I will hereby cease to make mentions of conspiracy theories surrounding anything but Apollo. And to further go into detail, I don't subscribe to any conspiracy theory at this time. There were users, whose names I don't remember, that I challenged openly and I angered moderators of these boards. As said, I would like to make an official apology for that. Shenzhou 7, since it needs to be addressed one final time, cannot be concluded by me or anyone else as fake, because I have simply not done the proper experiments to arrive at that conclusion. Scientifically, I had no reason to state so emphatically that these missions were faked in a swimming pool.
Shenzhou 5, I have openly regarded as being completely real, because scenes from the mission show evidence of free-fall for more than a minute at a time. As Shenzhou 5 clearly put a man in space, it would be foolish to suggest anything other than the official story for Shenzhou 7 without crack evidence.

Tempers will probably be high with my return to this page and my attempt to patch things up, and that is fully understandable. I will be available via PM and this thread to answer all questions personally regarding my conduct more than half a year ago. In addition, if there is anyone that feels I need to make a named apology to them, please let me know, and I will do so. I would like to wrap this ridiculous controversy up once and for all. In hindsight, leaving such an excellent forum for such a stupid reason was a dumb idea, and I would like to just distance myself from arguments about the Chinese space program. My number one goal here will be to make counter-arguments against the Apollo Moon Hoax Theory and discuss the technicalities of spaceflight (orbital mechanics/rocket science).
So this post is certainly not the end here -- because there are going to be a  lot of skeptical users who are going to want to tell me to fock off.

-Vincent McConnell.

[Andromeda]

Vincent, you were not "run off" the forums.  You were asked to present your evidence and back up your claims, a rule which everyone who posts here is expected to adhere to.

I appreciate your apology, but I think perhaps you don't really understand why people got annoyed.  Your tone in the post above sounds very high and mighty and it might be that attitude which puts people's backs up.  I appreciate that might not be your intent and I do not say these things to injure you, but merely to be open and honest about why I think your relationships with others on the board might be a bit strained.  If I am the only one who feels this way about your tone, then I withdraw my comments and apologise.

[Jason Thompson]

Well thank you for that rather verbose apology, Vincent. However:

I feel it has become necessary to make my official statement here, where I was kind of "run-off" the forums.

You were never 'run off' the forum. Your arguments were challenged as with anyone else here. At any point you could have withdrawn them or simply conceded. You left of your own volition. No-one here made any effort to make you leave.

I angered moderators of these boards.

Lunar Orbit is the one and only moderator here.

Tempers will probably be high with my return to this page and my attempt to patch things up, and that is fully understandable.

I don't think tempers will be high at all.

So this post is certainly not the end here -- because there are going to be a  lot of skeptical users who are going to want to tell me to fock off.

Why would you say that? I see no reason why you shouldn't be welcomed back, provided you keep to the same rules of conduct expected of everyone, namely be polite and back your arguments up with evidence. The only thing that got people wound up in this thread was your inability to provide the evidence and your attitude to people trying to show you where and why you were incorrect. You've apologised for that so it's done and we'll move on.