Why Satellites Don't Fall: The Gravity and Velocity Balance Keeping Them in Orbit

Every satellite currently circling Earth is in freefall. The International Space Station, India's IRNSS NavIC constellation, the GSAT communication birds, all of them are dropping toward the planet right now, at every moment, without pause. The reason they don't hit the ground has nothing to do with escaping gravity. Gravity is still pulling them, hard. The reason is geometry.
At roughly 7.9 kilometres per second, the speed needed to maintain a low Earth orbit, a satellite moves so fast horizontally that by the time it has fallen five metres toward the surface, Earth's own curvature has dropped away five metres beneath it. The ground keeps retreating. The satellite keeps falling. The two never meet. An orbit is not a place where gravity stops. It is a speed at which falling becomes a permanent condition.
Isaac Newton described this with a thought experiment long before any rocket existed: a cannonball fired fast enough from a mountaintop would circle the planet rather than land on it. The cannonball in that thought experiment and the GSAT-30 communication satellite parked above the Indian Ocean are doing exactly the same thing. The scale is different. The physics is identical.Not all satellites orbit at the same height, and altitude changes the speed required to stay up. This seems backwards at first, you'd expect higher orbits to need more speed, the way a car needs more engine to climb a hill. The opposite is true.
Closer to Earth, gravity is stronger, so a satellite needs to move faster to keep outrunning the pull. The ISS orbits at about 408 kilometres and travels at roughly 7.66 km/s, completing one lap of the planet every 92 minutes. Go higher and gravity weakens, so less velocity is needed to maintain the curve. At 35,786 kilometres above the equator, geostationary orbit, a satellite needs only about 3.07 km/s. At that speed and that altitude, one orbit takes exactly 24 hours. From the ground, the satellite appears to hang motionless in the sky, which is why every GSAT and INSAT satellite ISRO uses for television and weather sits in this band. A dish antenna pointed at one of them never needs to move.

Between these two extremes sits medium Earth orbit, where GPS and navigation constellations operate, including NavIC. Each altitude band is a deliberate engineering choice, not a default setting. The altitude determines the orbital period, the coverage area, the signal delay, and how much fuel it costs to get there and stay.The challenge of a rocket launch is not altitude. Any firework reaches a few kilometres. The challenge is speed. A rocket that goes straight up and stops accelerating will simply fall back down. To place a spacecraft in orbit, the rocket must tilt and spend most of its fuel building horizontal velocity, not height.
ISRO's PSLV and GSLV launch vehicles lift off from Sriharikota on the Andhra Pradesh coast and follow a curved trajectory over the Bay of Bengal, trading vertical climb for horizontal acceleration as each stage burns out. By the time the payload separates, it is moving sideways at several kilometres per second. That sideways speed is the orbit. The altitude is just where the orbit happens to be.

Mangalyaan, India's Mars Orbiter Mission launched in November 2013, illustrated this in a particularly elegant way. The spacecraft could not reach Mars escape velocity in a single burn from Sriharikota. Instead, ISRO performed six Earth-bound orbit-raising manoeuvres over 25 days, each one adding speed at the right point in the orbit until Mangalyaan had enough velocity to break free of Earth's gravity entirely and coast toward Mars. Aditya-L1, ISRO's solar observatory launched in 2023, followed the same patient strategy, multiple loops around Earth before heading to the L1 Lagrange point 1.5 million kilometres away. Getting up is not one event. It is a sequence of carefully timed accelerations.Even a perfectly circular orbit decays. At 400 kilometres, where the ISS operates, the atmosphere has not ended, it has only thinned to a near-vacuum. That near-vacuum still contains enough molecules to create drag, and drag bleeds velocity. As velocity drops, the orbit shrinks. The ISS loses roughly two kilometres of altitude per month to atmospheric drag and requires periodic reboosts from visiting spacecraft, including Roscosmos Progress cargo ships and, increasingly, commercial vehicles, to maintain its station.
Lower satellites decay faster. Chandrayaan-1, India's first lunar mission, entered lunar orbit in 2008 and was eventually lost to communication failure, but the spacecraft itself remained in lunar orbit for years afterward, the Moon's thin exosphere creates almost no drag. Earth-orbiting satellites in very low orbits, some imaging and reconnaissance spacecraft fly below 300 kilometres, can reenter within months without propulsion to compensate.

At geostationary altitude, drag is negligible. A satellite there could theoretically remain in orbit for millions of years. This creates its own problem: a dead satellite at 35,786 kilometres cannot be removed by atmospheric decay. It just stays there, a piece of orbital debris in the most commercially valuable band of space. The standard solution is a graveyard orbit, a parking band roughly 300 kilometres above geostationary altitude where decommissioned spacecraft are boosted at the end of their operational lives, clearing the lane for successors.
Speed is the only reason a satellite does not fall, and friction is the only reason it cannot stay forever. Every orbit is a negotiation between those two facts, the velocity that creates the orbit and the drag that slowly dismantles it. Every mission timeline, from a six-month low-Earth-orbit stint to a decades-long geostationary posting, is built around how long that negotiation can hold.