Timeline: A Brief History of SpaceX's Reusable Rocket Launches

Sending satellites, supplies and people into space is expensive—especially considering the fact that most rockets made to launch them there are designed to burn up as they re-enter the Earth's atmosphere. That's why one of SpaceX's key goals is to develop reusable rockets, which the company calls "a feat that will transform space exploration by delivering highly reliable vehicles at radically reduced costs."

SpaceX was founded in 2002 by Elon Musk, the entrepreneur who had previously co-founded PayPal and helped start the electric car company Tesla soon after. SpaceX's ultimate aim is to allow humans to travel to and inhabit other planets in the solar system—but an integral step toward this space travel revolution is to reduce the prohibitive costs involved.

"If one can figure out how to effectively reuse rockets just like airplanes, the cost of access to space will be reduced by as much as a factor of a hundred," Musk says on the company's website, in a post titled "Reusability: The Key to Making Human Life Multi-Planetary." "A fully reusable vehicle has never been done before. That really is the fundamental breakthrough needed to revolutionize access to space."

The company's attempts to launch and land rockets in one piece have made headlines throughout the last year. A Falcon 9 rocket—named after the Millennium Falcon from Star Wars and the nine engines that power the rocket's first stage, which SpaceX wants to land unscathed—achieved a successful vertical landing for the first time in late December 2015, amid several other attempts that ended in explosions and one that started that way.

Here are some of the highlights, to date, on the road to making reusable rockets a reality.

June 4, 2010: The inaugural launch of a Falcon 9 rocket (this after five launches of a previous vehicle called the Falcon 1), and SpaceX's first from Cape Canaveral, Florida, successfully sends into orbit the Dragon Spacecraft Qualification Unit, a prototype of the capsule designed to carry supplies and eventually astronauts to the International Space Station (ISS).

April 18, 2014: SpaceX launches a Falcon 9 rocket for a third resupply mission to the ISS, this time with landing legs, and becomes "the first to successfully perform a controlled ocean splashdown," according to the MIT Technology Review. The soft touchdown is a step toward landing on a solid surface.

January 6, 2015: The Falcon 9 rocket launch—the fifth resupply mission to the ISS but the first that would attempt to stick a landing—is canceled one minute before takeoff.

January 10, 2015: The first attempt to achieve the vertical landing of a Falcon 9 rocket onto a solid surface, in this case an "autonomous spaceport drone ship" floating in the ocean near the Cape Canaveral launch site, ends in a crash.

February 11, 2015: The Deep Space Climate Observatory (DSCOVR) satellite is launched aboard a Falcon 9 rocket, but rough seas prevent the drone ship from going out to receive an attempted landing.

April 14, 2015: The company tries again. Just as in the January attempt, the Dragon cargo capsule detaches successfully to make its way to the ISS. The first stage of the rocket—which SpaceX is trying to land intact—hits its mark on the floating barge. But it lands "too hard for survival," as Musk explains in a tweet. The rocket "just barely [failed] to stick the landing," according to SpaceX.

June 28, 2015: A Falcon 9 rocket explodes and disintegrates shortly after launch, due to, Musk later tweets, "an overpressure event in the upper stage liquid oxygen tank." SpaceX's president and chief operating officer, Gwynne Shotwell, says future launches will be suspended, most likely "a number of months," while the company conducts an investigation with oversight from the Federal Aviation Administration.

November 23, 2015: Blue Origin, the private space company founded by Amazon's Jeff Bezos, launches and lands its New Shepard rocket. "You've seen a lot of rockets lift off, but you've never seen one land," Bezos told Good Morning America. Blue Origin is reportedly the first to achieve the vertical landing of a rocket—intact and potentially reusable—after sending it into outer space. Musk tweets his congratulations the next day but quickly sends out additional missives that minimize the significance of the Blue Origin success.

December 21, 2015: SpaceX successfully lands a rocket upright for the first time, albeit on land rather than on the floating platform. "11 satellites deployed to target orbit and Falcon has landed back at Cape Canaveral," Musk tweets. "Welcome back, baby!"

It's Bezos' turn to tweet his congratulations, but his choice of words reads more backhanded than wholehearted. Several responses along the same theme seem to imply that SpaceX's achievement is more impressive.

January 17, 2016: SpaceX launches the Jason-3 satellite for NASA, which will measure the height of the ocean surface, aboard a Falcon 9 rocket. The first stage lands at a good speed, Musk says, but one of the legs didn't latch, causing it to fall over and subsequently explode. It's "definitely harder to land on a ship," he says.

Soon after Sunday's launch, Musk tweets out his predictions for landing successes in the next two years:

SpaceX has a long list of future missions listed on its site, but the entries do not indicate which will include landing attempts on land or on the drone ship.