What's The Difference Between A Rocket And A Space Shuttle?

With SpaceX now launching its reusable Falcon 9 rocket up to several times a week, the U.S. company has quickly become a giant of global spaceflight.

This is a far cry from the days of America's Space Shuttle, which launched an average of 4.5 times a year during its lifetime between 1981 and 2011. People sometimes use the terms "rocket" and "Space Shuttle" interchangeably, but there's an important difference between the two.

A rocket is the launch vehicle that carries a crew or payload to space, while the Space Shuttle was a specific reusable orbiter that used rockets to get to orbit before returning to land like an airplane. Put simply, the rocket is the delivery system, while the Space Shuttle is the vehicle riding on it.

If you watch a Space Shuttle launch, you can clearly see its two side rockets powering the vehicle to space. After a couple of minutes, when the Space Shuttle is well on its way, these two side boosters detach and fall into the ocean before being recovered for reuse.

Meanwhile, the Space Shuttle's three integrated rocket engines continue to propel the vehicle into orbit. Similarly, a Falcon 9 launch involves the first-stage rocket booster powering the upper stage, including the crew or payload, toward space. Like the Space Shuttle, the booster detaches from the rest of the vehicle, but instead of being recovered from the ocean, it lands upright back on Earth.

Modern rockets like SpaceX's Falcon 9 comprise a first stage and an upper stage supporting the crew capsule or payload, which sits atop the vehicle. The Space Shuttle had three main components: two side rocket boosters that fell away and were later recovered, an external fuel tank that was discarded, and the plane-like section for the crew. The shuttle launched in a similar way to conventional rockets, using rocket engines to thrust upward to escape Earth's gravity.

But differences emerge once a mission starts. The shuttle, for example, released its two rocket boosters and fuel tank before reaching orbit, whereas Falcon 9's first stage returns to Earth for reuse, and the upper stage delivers the crew capsule to orbit before separating from it.

Coming home, the shuttle reentered Earth's atmosphere at high speed, with the underside heat shield resisting the extreme temperatures. It then glided like a plane toward its destination, landing on a runway before deploying brakes and a parachute system to bring it to a stop.

After 30 years of operations, the U.S space agency's final Space Shuttle mission took place in 2011. Becoming one of NASA's most expensive space projects ever, it found the system too costly to maintain. Safety was also an ongoing concern following two tragic accidents — Challenger in 1986 and Columbia in 2003 — in which all of the crew members perished.

To reduce spending, NASA encouraged private firms to start making commercial rockets to carry crews to orbit in separate capsules — similar to how the space agency sent astronauts to orbit in the Gemini and Apollo programs in the 1960s and 70s.