Billionaire technology entrepreneurs Elon Musk (PayPal, Tesla) and Jeff Bezos (Amazon) are engaged in a patent dispute involving a method for making it practical to reuse rockets.

As reported by the Washington Post, Bezos’s space company, Blue Origin, owns a patent for “sea landing of space launch vehicles and associated systems and methods.”

The patent, granted in March 2014, describes a way to land a booster stage rocket on a platform at sea in order to reuse it for another launch.

Bezos and two other inventors are named in the patent application.

Recycle, Reuse

The advantages of the method are described in the patent application:

Despite the rapid advances in manned and unmanned space flight, delivering astronauts, satellites, and other payloads to space continues to be an expensive proposition. One reason for this is that most conventional launch vehicles are only used once, and hence are referred to as “expendable launch vehicles” or “ELVs.” The advantages of reusable launch vehicles (RLVs) include the potential of providing low cost access to space.

Although Bezos owns the patent for the method, Musk’s SpaceX company was the first to actually attempt using it.

In January, the attempt to recover the rocket failed — the booster hit the barge platform that the company calls an “autonomous spaceport droneship” but exploded.

“Close, but no cigar this time,” tweeted Musk.

Despite its initial failure to recover its booster rocket, SpaceX was still the first commercial company to resupply the International Space Station.

Musk’s company challenged Bezos’s patent via a request for Inter Partes review, saying that the idea of landing a rocket booster on a floating platform significantly predated Bezos’s patent application.

Old News?

According to SpaceX’s filings with the US Patent Trial and Appeal Board (PTAB), “The ‘rocket science’ claimed in the ‘321 patent was, at best, ‘old hat’ by 2009.”

Administrative law judges at the PTAB sided with SpaceX, sending the matter to a full administrative hearing before the PTAB. This does not mean that SpaceX is sure to prevail, but it does mean that its odds of invalidating the patent have increased.

Blue Origin and SpaceX are among the companies competing to win a NASA contract to transport US astronauts to the International Space Station.

Since the US space shuttle program was retired in 2011, the US has often resorted to sending astronauts into space by “hitchhiking” on Russian spacecraft.