Why are GPS satellites easier to launch than Geostationary satellites?

Answer 1

The further away from the planet a satellite is, the longer the orbit. So satellites in low earth orbit - from about 120 to about 600 miles up - orbit the Earth in about 90 to 100 minutes, doing 15-18 orbits per day. The International Space Station, for example, is about 150 miles up, and appears to ZIP across the sky. The Space Shuttle can get up to "LEO" or "low Earth orbit".

Higher orbits take longer. One of the most useful orbits is about 22,500 miles up, so that the satellite takes 24 hours to go around the Earth one time. The means that the satellite is orbiting the Earth at the same speed that the Earth itself is turning, so that the satellite appears to remain in the same place all the time. This is called "geo-synchronous" from the Latin words for "Earth" and "same time". Communications satellites and TV satellites are commonly in "geosych" orbits. The Shuttle cannot make it to geosynch altitude, for lack of fuel. So comsats headed to geosynch orbits are launched from the Shuttle with special booster rockets, or are launched from unmanned "heavy lift" rockets.

Answer 2

The best answer is simply: That's the way gravity works.

If you take Newton's deceptively simple formula for the gravitational force

between two masses, and if you have enough geometry and calculus to

massage the formula around, look at it from different angles, and follow it

through to some of its implications, then some wonderful things happen.

The first result is that all of Kepler's laws of planetary motion fall out on the

table, and you no longer have to ask "Why do the planets do that ?" They

do everything they do because that's the way gravity works.

You also discover that neither the size of the orbit nor the speed in orbit depends

on the mass of the orbiting body. The speed depends only on the size of the orbit.

You're happy about this because it means that an astronaut can do a "space walk" ...

separating himself from his spacecraft but still staying in the same Earth orbit that

the spacecraft is in, so that he doesn't go sailing away from the spacecraft just

because he has less mass.

And you also discover the strange fact that the larger the orbit, the slower the

orbiting body moves. An astronaut on a space walk in low-earth-orbit is orbiting

faster than the moon is!

It's just the way gravity works.

Answer 3

The International Space Station is in a "low Earth orbit" about 180 miles up. It takes about 90 minutes, so the ISS orbits at about 18,000 miles per hour.

The Earth's orbit around the Sun varies a little because it is an elliptical orbit, not perfectly circular. But on average, the Earth is going about 67,000 miles per hour in its orbit around the Sun.

Answer 4

Every mass object, in a closed orbit around another object on account of their mutual gravitational

attraction, moves faster at the points in its orbit where it's closer to the central body. The best way

to explain the reason is: Because that's the way gravity works.

When you take Newton's laws of motion and massage them mathematically to see where they take you,

they lead to several interesting places, including:

-- Stable, elliptical orbits, which behave according to . . .

-- Kepler's Laws. Kepler derived them empirically, from analysis of Tycho's observations.

But Newton's laws show mathematically why it must work that way.

-- Higher speed at smaller orbital distances

Answer 5

GPS satellites are easier to launch than geostationary satellites because they orbit at a lower altitude, requiring less energy to reach. Additionally, GPS satellites operate in a constellation, meaning that multiple satellites work together to provide coverage, reducing the need for individual satellites to cover large areas like geostationary satellites do.

Answer 6

Geosynchronous satellites are launched into much higher orbits. That requires more fuel, which requires bigger rockets.