SpaceX’s reusable rockets make space travel much cheaper

Emma Flickinger Feb 27, 2017

Launching things into space is expensive — really expensive. A rocket costs more than a commercial jet. But unlike jets that make thousands of trips before being retired, rockets are used only once because of the extreme stress and temperatures involved in leaving and re-entering the atmosphere.

SpaceX wants to change that. Founder Elon Musk believes that reusable rockets will eliminate the prohibitive cost of space travel and allow space travel to become commonplace.

Most modern rockets are multi-stage, built of multiple parts that each have their own engines and fuel. When each stage runs out of fuel, it falls back to Earth, and the next stage begins burning its propellant. The lighter mass makes it easier to accelerate the payload to escape velocity. This system works well for getting things into space, but isn’t very efficient or cost-effective. The jettisoned rocket stages essentially become trash, cluttering Earth’s orbit or polluting its oceans. New rockets are then constructed for tens of millions of dollars.

SpaceX’s rockets don’t operate this way. After separating from the payload, instead of falling back to Earth, the first stage rocket decelerates itself with bursts of fuel and uses fins to steer onto a landing platform. When reusable rockets become commonplace and are more widely adopted, according to Musk, these landing platforms will be autonomous pods floating in the ocean. The first successful landing of a SpaceX Falcon 9 rocket was in December 2015. However, the first successful rocket water landing was in April 2016. This week, a Falcon rocket was the first private rocket to launch from the historic NASA launch pad at the Kennedy Space Center in Cape Canaveral, Florida.

The idea behind reusable rockets seems simple enough, so why is this concept just now being tested? Traditional launch systems are designed to maximize performance and reliability. Government designers and engineers prioritize the safe completion of the intended mission on the first try over sustainability or efficiency. As former NASA administrator Alan Stern explains, “[The Department of Defense] doesn’t care whether it costs $100 million or $300 million ... what they want is a guarantee it’s going to work.” And these systems do work. The Atlas V launch vehicle, sometimes called “the world’s most reliable rocket,” uses a different type of rocket for each stage, with up to three different kinds of propellant. This made the rockets extremely powerful and precise, but largely expensive to manufacture and fuel.

The Falcon rocket is designed to minimize cost — a liberty SpaceX can take as a private company. All its engines are the same kind, running on liquid oxygen and RP1, a fuel made from refined kerosene.

The Falcon’s two stages are the same diameter and made from an aluminum-lithium alloy. The use of the same material for each stage reduces manufacturing costs. SpaceX also keeps costs down by manufacturing its own engines in-house. The Merlin engines designed for the Falcon use a needle-like device called a pintle to inject propellant to the combustion chamber.

According to Tom Mueller, SpaceX propulsion chief, it’s cheaper than typical rocket engines, which use a spray instead, and also less likely to cause explosions or other combustion-related accidents. The company also developed its own reusable, cost-effective heat shield technology, PICA-X, with help from NASA.

PICA-X, Merlin engines, and every other component of the Falcon rockets are designed to be as durable as possible to withstand reuse for trips back to Earth, journeys to the moon, and travel beyond. Musk’s ultimate goal is to use his rockets to settle humans on Mars by 2030. This will only be a possibility with quick innovation.