Having coverage of an area by satellite is fine, but the observed can know when you can watch and when you can't. This has been used to advantage by hiding from the sats. Change an orbit and they can't hide until that change is known. It happens.
-- Rick
On Wed, 27 Jan 2016 20:27:59 -0500, rickman Gave us:
You mean like these?
Or this 'guy'?
Or these 'more advanced' guys?
Are you talking about slower velocity or longer orbit time?
Dan
The data I have seen says both. That is what I said above. The lower orbits have both a shorter period and a faster velocity. Seems counter intuitive that the velocity would be faster in the lower orbits. Mercury orbits at a 60% faster velocity than Earth and Neptune at 18% the velocity than Earth.
-- Rick
Changing the orbit inclination is really expensive. For a 450 km circular orbit, changing the inclination requires 133 m/s delta_v. A few single degree changes or a 10 degree change and the fuel is exhausted.
For elliptical orbits, the change is done at apogeum, since the delta_v also depends on actual speed. When launching from high latitudes to geosynchronous orbit, the booster puts the satellite to something like 400 x 40000 km orbit with inclination similar to the launch site latitude. At the top of the GTO orbit, the satellite motor changes the orbital inclination to 0 degrees and rounds the orbit to
36000 km circular. Sometimes this motor and the small station keeping thrusters use the same storable fuel tank. Thus, if the booster does a good job, less fuel is needed to reach the geosynchronous orbit and the saved fuel can be used for station keeping, extending the satellite usable lifetime.
Very similar, conceptually, to a spinning dancer/skater: if they extend their arms (increase radius) the spinning slows & vice versa...
-- Cheers, Chris.
I'm amazed that you know so much about military sats. What clearance level do you hold?
-- Rick
Not really. That is simply conservation of momentum. That does not apply when changing orbits by expending fuel.
-- Rick
On Thu, 28 Jan 2016 02:02:08 -0500, rickman Gave us: snip
How would you know? And if that was some lame attempt at sarcasm... how would you know?
Sometimes you make some pretty stupid statements. IF he had one, he could not mention it, nor would he.
Because to be in orbit that low they would have to be moving at thousands of miles per hour and would be burning up the place by air friction.
I think someone would notice.
On Thu, 28 Jan 2016 02:03:29 -0500, rickman Gave us:
Orbiting masses retain orbital altitude by moving at a rate which nearly throws them out of orbit, yet keeps them also at the verge of diving toward the gravitational attractor of the spheroid they orbit.
There are decaying moons around Saturn which will eventually fall into the planet. The moons of Mars are also on a decaying orbit.
We place satellite (masses) very close to our spheroid. It takes a high velocity (orbital) to keep them at a fixed (geosynchronous) station, or at a fixed (orbital altitude). It is referred to as "free fall condition".
The ISS does not perform a lot of velocity alteration maneuvers because we already have it moving along pretty fast. It runs at about
17,000 MPH. That is 4.76 miles per second, or 7.6-7.7 km/s (around 27 500 km/h).The ISS maintains an orbit with an altitude of between 330 and 435 km (205 and 270 mi) by means of reboost maneuvers using the engines of the Zvezda module or visiting spacecraft. It completes 15.54 orbits per day
So you think that the military has some wonder weapons that could even break the laws of physics ?
Those figures for the 450 km orbit was taken from a book published in
1986, so not so much "rocket science" even at that time.The required delta_v can be calculated from
delta_v = v_o * 2 * sin (alpha/2)
in which v_o is the orbital velocity and alpha is the required change in inclination.
Nothing you have shown says anything about the amount of fuel the sats have.
The real point is that you don't know so much about them. If you did, you wouldn't be able to talk about it.
-- Rick
That knowledge has nothing to do with military, it is just physics.
It appears that some people think "the military can do anything" but in fact they have to operate within the laws of physics. Sometimes claims are made that are beyond that, but that can only happen when there is secrecy or ignorance involved.
This makes no sense. Orbits like this have a period of about 2 hours, and it will take weeks to move the satellites around to set your optimum time to a value that is only modulo 2 hours.
Sorry for you, but it is correct. You need to make more study of how those constellations (like GNSS and Iridium) are built. Until then I am no longer prepared to discuss with you.
On Thu, 28 Jan 2016 03:10:54 -0500, rickman Gave us:
Hence you obviously know nothing about them, since you are acting like you do and are talking about it.
Look at the mass ratio:
This information has been public knowledge for just a century :-)
See Kepler's Laws:
-- Grizzly H.
Indeed. It is all "fairly easy" to calculate. As a radio amateur who has used amateur satellites and has visited colloquiums where people explained the methods used to determine and change orbits, I know that "rocket science" is not always as complicated as people generally believe (certainly not this part of it), and also that people often overestimate what can be achieved.
(we all know the story about "star wars" and that we did not hear about it any more after a while...)
There are *many* useful orbits and they're not all "modulo 2 hours".
Google "sun synchronous" orbits to get a clue. It's one of the more useful ones for spy sats. .and yes, they are moved to interesting spots at will.
Clueless.
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