Why a kilogram in orbit costs so much
A rocket must accelerate not only its payload but also the fuel needed to lift that payload. And because the fuel itself has mass, the rocket needs still more fuel to carry it. This compounding demand is a consequence of the rocket equation: gaining speed requires carrying propellant, while carrying that propellant makes the vehicle heavier.
The rocket also has to reach orbital speed, not merely rise above the atmosphere. Near Earth, orbit means moving sideways fast enough to keep falling around the planet rather than back to the ground. Much of a launch vehicle’s effort goes toward reaching that speed, overcoming gravity and air resistance along the way.
The rocket is mostly a chain of tradeoffs
Engineers manage the mass problem with staging. When a lower stage has used its fuel, the rocket drops that stage’s empty tanks and engines. The remaining vehicle no longer has to accelerate that dead weight. But stages, engines and the structures connecting them still add mass, and every component must survive intense vibration, heat and acceleration.
That is why payload capacity is only part of a launch’s economics. A rocket, launch site and ground equipment require substantial investment whether a flight carries a small satellite or a larger one. Operators spread some of those costs across each mission, while payload limits constrain how much can be sold on a given flight. The price per kilogram therefore reflects both the rocket’s physical limits and the expense of preparing and operating the launch system.
Why sharing a launch can help
When several satellites can travel together, they can share the cost of one rocket and its launch operations. But they must fit within the vehicle’s capacity and meet compatible schedules and orbital requirements. A kilogram is expensive not simply because it is heavy, but because getting it into the right orbit consumes scarce rocket capacity and a carefully engineered mission.
