Billionaires truly have more money than they know what to do with, and as such go into a number of different directions when it comes to finding outlets for it. Bill Gates plans on giving as much as he can to charity, feeling like his wealth will be better used in these endeavors. Bernard Arnault has an art collection with paintings from Picasso and Van Gogh. Warren Buffett claims to be very frugal, eating at McDonald's.

If there's a notable common choice among several billionaires, though, it's space. There are a few different mega-rich people who have taken up space travel as their pet cause, continually claiming that they'll be the one to make space tourism a reality. Many of them have dreamed of space since they were children; some of them even remember the space race of old and want to create a new race for this generation.

Of course, that race has stalled out a bit at times. Billionaires tend to be overly hubristic in their claims, whether for publicity or truly believing it themselves. But as it turns out, making good rockets is pretty hard, and not every expectation has been met. But progress, even if it hasn't been as fast as these guys and their fans want, has been made.

Here are four of the world's billionaires who have sought to turn space travel into a reality.

Elon Musk: SpaceX and Mars

Who else could this have started with? Elon Musk has easily been the most prominent billionaire to get invested in the space race -- in part because he clearly loves the attention. But he has also had a consistent goal with his company SpaceX from the very beginning: colonizing Mars. Musk wants human life on Mars, and to do that, humans need adequate transportation into space.

Musk's enthusiasm for creating a new space race (and being the face of it) have led to more excitement about space travel and colonizing other planets than there has been in possibly decades. SpaceX, valued at over $20 billion, has blown up a lot since its initial creation. Problem is, so have a lot of the rockets.

The years 2006, 2007, and 2008 each saw their own separate SpaceX rockets explode occur relatively shortly after take-off. It took years after these failures for Musk and SpaceX to rebuild their respective reputations, but even after that, the company wasn't free of failures. In 2016, a SpaceX rocket exploded during fueling -- it never even got to launch! Musk later put out a compilation video of his "favorite" SpaceX explosions as a PR spin, but that's a lot of money spent on a lot of rockets that blew up almost immediately.

SpaceX founder Elon Musk wants to colonize Mars.

SpaceX's 2018 launch of a Falcon 9 rocket also included a spy satellite that became detached and was destroyed, causing some additional skepticism even though an internal probe later determined the company was not responsible.

SpaceX has taken lessons from these failures, though, and seen some additional successes as a result. The company has successfully landed 16 rockets, with one 2017 Falcon 9 launch making it into space to deploya satellite before successfully making the landing. In February 2018, SpaceX launched the Falcon Heavy complete with a Tesla car inside. Two of the Falcon Heavy's "cores" (booster rockets) successfully landed, but the center core was lost. That's still a mostly successful mission. It's hard to tell how close SpaceX is to any actual space travel with citizens, but they've made a lot of strides the past couple of years.

Jeff Bezos: Blue Origin

Amazon founder Jeff Bezos isn't as much a face of the space race as Musk is, but that's by choice. Bezos' space company Blue Origin actually predates SpaceX, as the Amazon chief founded the firm in 2000. But Bezos and the company have chosen to stay more behind the scenes as they develop their technology.

As a result, their successes rather than their failures often come as more of a shock. For example, Blue Origin's first rocket, the New Shepard, successfully launched to 329,839 feet in 2015 and then made a soft landing. After barely a peep from Bezos's company, it suddenly beat SpaceX in having a rocket successfully soft-land from space. In fact, the New Shepard went on to make a total of five such successful landings.

Bezos has never claimed to have colonization ambitions, but instead wants to give people safe, more-efficient, affordable access to space. Multiple successful landings have also shown hope that the company can create reusable rockets.

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Amazon founder Jeff Bezos wants to give affordable space travel a thumbs-up.

Blue Origin's newest project, the New Glenn, is being designed for orbital flights (New Shepard flights are suborbital) and the company hopes to get its first rocket aloft by 2020. That's pretty optimistic for Blue Origin -- and the company is still claiming that it might be sending tourists into space by 2018's end.

But Blue Origin has failed plenty before. In 2011, a Blue Origin rocket failed during a test flight, and in 2017, the company tweeted about issues with a BE-4 engine. Even then, however, problems with the BE-4 (which will power the New Glenn) didn't seem to get in the way of any timelines, and later tests have proven more successful. If Blue Origin has had any catastrophic setbacks of any kind, the company has been tight-lipped about it. If the program hasn't, that's quite the track record in such a dangerous field.

Richard Branson: Virgin Galactic

Richard Branson was doing Musk's shtick long before Musk was, declaring space tourism an inevitability even before Virgin Galactic's inception in 2004. But despite continually receiving funding for his endeavors (most recently $1 billion from Saudi Arabia), Branson's space-flight successes haven't been as grand as Musk's or Bezos' -- and his failures have been far more catastrophic.

While a Branson-sponsored SpaceShipOne rocket privately built by Scaled Composites successfully flew into suborbital space twice in one week, its VSS Enterprise SpaceShipTwo rocket broke apart and crashed in October 2014. One pilot was killed, while the other was significantly injured. The U.S. National Transportation Safety Board (NTSB) pointed to the ship's "feather" system, which was controlled by levers and meant to reposition the tail wings to slow down the rocket during re-entry from space.

Virgin Galactic founder Richard Branson doesn't just like Jet Skis. He's also building spaceships.

While it was determined a crew member unlocked the feather system prematurely, the NTSB deemed the safety mechanisms put into place by ship builder Scaled Composites showed their "failure to consider and protect against human error."

It would be years before they attempted anything similar. The newer SpaceShipTwo vehicle, VSS Unity, did not even have a glide test until 2016. Seven glide tests later, it took an actual test flight and landed safely after successful deployment of the feather system. Branson tweeted that the company was "back on track" as a result. Still, the tragic 2014 crash and the failure to prevent it still looms large over Branson's space-tourism endeavors.

Paul Allen: Stratolaunch

The SpaceShipOne rocket that successfully flew twice in one week might have been sponsored by Branson, but it was first backed by Microsoft co-founder Paul Allen.

Allen dreamed as a child in the 1950s and '60s of being an astronaut, but had to settle for co-founding Microsoft, owning multiple professional-sports teams and making billions of dollars. However, that dream of going into space seems to have stayed with Allen, who's putting in his own work to make commercial space travel a reality. He's just taking a more outside-the-box approach than the others.

Allen founded Stratolaunch Systems in 2011, describing it on the company Web site as "an air-launch platform to make access to space more convenient, reliable, and routine." In more informal language? Staratolaunch making really big planes to send things into space.

Seattle Seahawks owner Paul Allen wants to win not just the Super Bowl, but also the billionaires' space race.

The Stratolaunch plane has a 385o-foot wingspan and a center-wing location where payloads that add up to 500,000 pounds can be attached. It has two cockpits and requires six jet engines. Should the craft prove successful, it could send satellites into space.

The first big stride for the Stratolaunch came in late 2017, when the company put it through a taxi test on the Mojave Air and Space Port Runway. The test found some of its basic systems like steering and braking to be successfully operating. More taxi tests are planned, and should they go similarly well, Stratolaunch Systems intends to make its first test flight in summer 2018. When that happens, we'll know much more about the future of these aircraft.