How far up do satiliites need to go to stay in Earth's orbit?

Answer 1

There's no hard lower limit for orbiting. "Staying" in orbit needs to be defined by time aloft. Air resistance removes orbital energy; the lower the altitude the denser the air and the more rapidly energy is removed. If you get a streamlined projectile up to orbital velocity at 150 km altitude it might make it through one orbit before crashing. One study (ref.) found a range of 30 to ~200 days lifetime for a 375 km altitude orbit. (The variability is due to the fact that solar radiation, which varies over an 11-year cycle, "expands" the atmosphere.) The HST orbits at about 565 km altitude and needs a small (several feet/sec) velocity increase (reboost) every few years. Geosynchronous satellites are far higher (~36,000 km altitude) and the atmosphere is virtually nonexistent, so these orbits are very long-lived. Orbital lifetime depends not only on air density but also on the satellite's "ballistic coefficient" (mass divided by [frontal area * drag coefficient]); a lower coefficient means more deceleration and a shorter orbital lifetime for a given initial altitude.
EDIT: About orbits and speed: A few answers have referred to the fact that you need to have the speed necessary for orbit at the particular altitude. While that's true, I assume the question is about orbital lifetime, not getting into orbit in the first place. If you're in a high orbit that is decaying due to energy loss, what happens is you gradually descend to lower orbits and your speed increases so you continue to have the velocity needed for orbiting at the new altitude. It's automatic, it's a form of the potential-to-kinetic energy trade we see every day here on the ground. Left unboosted, orbiting objects encountering air drag descend in a spiraling orbit whose rate of descent increases as radius decreases.

Answer 2

It depends. If they are traveling very fast, they can be pretty close. If they are traveling slowly, they need to be far away. There is a balance where they travel at the same speed the earth is rotating. this distance is the most commonly used for satellites. I'm not sure what distance that is. But consider the moon orbits like a satellite, and it orbits about every 28 days.

Answer 3

is very - confident it would. in case you prefer to get into very technical there may be a delicate distinction in the baricentre between solar and Earth yet not something to make any important distinction. Now an important exchange in the solar's mass might heavily effect the earth's orbit yet a metamorphosis in the Earth's mass does not make a distinction. right this is the math. The tension of gravity between 2 gadgets is given by making use of the equation F = G m1 m2 / r^2 enable's say m1 is the mass of the solar and make contact with it M. enable's say m2 is the mass of the Earth and make contact with it m. we've rewritten our equation F = G Mm/r^2. the place G is Newton's gravitational consistent and r is the centre to centre distance between the two a lot. Now we would prefer to renowned the acceleration using gravity how can we link acceleration to tension of gravity? of course F = ma the place F is the stress of gravity and m is the mass to be speeded up and a is the acceleration. you're asking concerning the accelration of the Earth so m is the mass of the Earth. Combining the two equations. F =G Mm/r^2 and F = ma we get ma = GMm/r^2 now we are able to divide by by making use of m (consequently cancelling out the mass of the earth, or regardless of mass is contemporary technique acceleration). a = GM/r^2 the reality that the mass of the item being speeded up is cancelled out skill that a human with mass 70kgs and an area station with a mass of 450000 kg will fall to earth (or subsequently orbit the earth that's a similar element) on a similar fee that's why astronauts inspite of having mass are weightless in low earth orbit using fact they are accelerating in the direction of earth on a similar fee as one yet another. you ought to take Jupiter and stick it the place Earth is and its orbit around the solar would be a similar using fact the Earth's.

Answer 4

i dont know if you can consider the Space Station a satelite, but it orbits the earth at an altitude of ~350 kilometers, but needs to be going 17,500 mph to do so.

Answer 5

I think they can orbit at 150 miles

Answer 6

That is determined by the speed and mass of your vehicle. You need to be above the atmosphere so that you can travel at speeds upward of 25000 MPH.

Answer 7

The moon spins one time on its axis for every reveloution around the earth i believe. that would be why you see only one side

Answer 8

About 26000 miles.

Answer 9

6500 Km i beleive!