simonshack wrote:Ok. But NASA told us that the pliers lost by one of their astronaughts (the guy repairing the solar panels) were expected to eventually "fall down to Earth - but we will me monitoring them by radar" (yes, I'm quoting the NASA experts). Now, weren't those pliers also orbiting in space without air resistance? Does the ISS have any propulsive means to keep it where it is (between 278 and 460km (wikipedia) for year after year? No. Do the pliers have that? No. I trust you get my drift.
Hence, the questions I would have here concern specifically the issue of propulsion outside of the Earth's atmosphere. Let us accept for now that a satellite may be sent up to a certain altitude where it gets caught up in a centrifugal force which keeps it reliably circling the Earth at high speed (or rest in geosynchronous orbit - at 36.000km from Earth - the alleged, favored altitude for communication and weather satellites). How exactly, I wonder, are these precise altitudes achieved? How do they stop a given satellite (launched by a rocket into this space vacuum devoid of air resistance) at its ideal altitude?
Simon: The detail about the pliers is odd. I am already on board with the ISS being probably fake, but let's say that maybe the pliers were described as 'falling' in the sense that they 'fell out' of orbit. Maybe they got some sort of kick and bounced off the ISS going in the wrong direction enough to start descending to a lower orbit and eventually plummeting into the atmosphere. Does that make sense? I don't know.
How precise altitudes are achieved? I don't know. How the drilling of a miles-deep well is achieved? How a huge bridge or building is built? With a lot of calculations, I suppose.
I think a satellite has its own motor that can be fired once or twice as required (not continuously) to get to the precise high orbit it needs. If a satellite is carried by a shuttle (assuming something like the shuttle was real), or rather by some other unmanned vector, to a low orbit, the transfer of orbit seem to happen in the following conditions (this comes from the page I had linked to already, along with other brief illustrations on how orbits work):
Elliptical Orbits: most orbits are not perfectly circular. All orbits are ellipses (flattened circles) with a high point (apogee) and a low point (perigee).
At apogee, when the satellite is farthest from the earth, it is going the slowest - it's ready to fall back toward the earth.
As the satellite falls it gains speed, and "overshoots" the earth, swinging quickly through perigee, then gaining altitude back toward apogee.
The satellite doesn't stay in orbit at the apogee distance because it isn't going fast enough when it reaches that point. It doesn't stay in orbit at the perigee distance because it's picked up so much speed by that point that it starts climbing again.
If we speed the satellite up while it's in low circular earth orbit it will go into elliptical orbit, heading up to apogee.
If we do nothing else, it will stay in this elliptical orbit, going from apogee to perigee and back again.
BUT, if we fire a rocket motor when the satellite's at apogee, and speed it up to the required circular orbit speed, it will stay at that altitude in circular orbit. Firing a rocket motor at apogee is called "apogee kick", and the motor is called the "apogee kick motor".
I don't know if the above is correct or accurate. I know it stands for a scientific brief explanation of how satellites achieve their orbit. I am sure dozens of other sources on the web can be found.
Dcopymope: you say "what’s making these satellites move in this manner can’t be rocket motors as we know them, then they must be using some technology that we don’t know about".
Again with the "secret science".
How the Moon does not fall onto the earth? Once again: space void. Once you don't have air resistance, there is nothing stopping those objects from going. As I said: satellites orbit planets, planets keep orbiting the sun and nothing stops them. Not only that, but apparently they can grow in size over the billion of years as they attract rocks from outer space, or diminish in size as they smash against each other. And yet all through this they keep on orbiting the damn sun. They have no alien secret propulsion system either.
It is probably fair to say that it is by observing planets and comets that humans figured out how artificial satellites could work.
Hoi, as to your question about Hubble slowing down, I don't know. Can you quote the exact source for this? I don't think any satellite can ever slow down, unless to descend to a lower orbit, considering that it is the speed that keeps it in orbit. I am trying to read somewhere about the exposure times for the Hubble, but so far no luck. Something about how the hubble locks onto a target can be read here: http://science.howstuffworks.com/hubble6.htm
Hubble's Fine Guidance Sensors help keep the telescope fixed on its target by sighting on guide stars. Two of the three sensors find guide stars around the target within their respective fields of view. Once found, they lock onto the guide stars and send information to the flight computer to keep the guide stars within their field of view. The sensors are more sensitive than the gyroscopes, but the combination of gyroscopes and the sensors can keep the HST fixed on a target for hours, despite the telescope's orbital motion.
I read elsewhere (on wickedpedia I think) that despite the fast orbiting and the earth getting in the way, there are certain limited portions of the sky (towards north and south, probably, as the hubble circles around the equator) that are always available to the telescope, I guess those can work for the long exposure times that are needed.