WASHINGTON — One patent attorney said a recently approved Blue Origin patent for landing rockets on water-going barges stands a good chance of being overturned, thanks to a review initiated by Space Exploration Technologies Corp. — the company closest to actually using the technique Blue Origin wants to protect.

Examiners approved U.S. Patent 8678321, “Sea landing of space launch vehicles and associated systems and methods,” on March 25, giving Kent, Washington-based Blue Origin the rights to an invention that Hawthorne, California-based SpaceX claims in an Aug. 25 petition for review is “old hat” in the rocket-engineering world.

“The patent granted is, in my opinion and in SpaceX’s counsel’s opinion, invalid,” said Andrew Rush, a Jacksonville, Florida-based patent attorney who blogs about space-related intellectual property matters at IPinSpace.com and helped Mojave, California-based Masten Space Systems implement an intellectual property development program during a 2011 internship. “The applications Blue Origin filed were pretty aggressive and pretty broad and written, SpaceX alleges, without a high degree of knowledge and sophistication about the space industry.”

Key for SpaceX, Rush said, is the provision of U.S. patent law that says the mere description of an invention in the public sphere is enough to block another would-be inventor from patenting it. In other words, Blue Origin’s patent “treads on technology that existed way before Blue Origin filed for the patent application,” and should therefore be struck down.

A possible knockout blow for Blue Origin’s patent is a sea-landing system described by Japanese inventor Yoshiyuki Ishijima in a collection of papers, “Re-entry and Terminal Guidance for Vertical-Landing TSTO (Two-Stage to Orbit),” published in 1998 by the American Institute of Aeronautics and Astronautics. In its petition for a so-called inter partes review, SpaceX makes heavy reference to those papers and others published before the 2009 filing date on Blue Origin’s patent application.

The system Blue Origin received a patent for, and the one described in the Ishijima papers, calls for launching a multistage rocket and, after first-stage separation, steering the detached core down to a floating platform for a tail-first powered landing. In July, SpaceX indicated it might be ready to try a maneuver like that as soon as December as part of a NASA cargo launch to the space station. A late December launch — for Fort Lee, New Jersey-based satellite operator Orbcomm — is another candidate for a barge landing, SpaceX said following its last launch for Orbcomm in July.

Still unsettled is the question of whether the inventors listed on Blue Origin’s patent application, which include Amazon.com and Blue Origin founder Jeff Bezos, knew about any of the documents referenced in SpaceX’s filing prior to seeking a patent in 2009.

“The inventor doesn’t have a responsibility to go out and look for prior art, but if he does find prior art, he has to tell the patent office,” Rush said. “So If Jeff Bezos was aware of this paper SpaceX is citing, he would have had a responsibility to give a copy of that paper to the patent office because it is relevant to his technology. He would have had to do that at the time he applied for the patent.”

Neither SpaceX spokesman John Taylor nor Blue Origin spokeswoman Brooke Crawford would comment for this story. Scott Talbot, a Reston, Virginia-based attorney for Cooley LLP, the firm that prepared SpaceX’s request for an inter partes review, also declined to comment.

At its current pace, Blue Origin would seem to be years away from attempting to land a reusable rocket at sea. Founded in 2000, Blue Origin has conducted six suborbital test flights, the latest of which ended in an explosive failure in 2011 in the skies above the company’s test range in Culberson County, Texas, about 55 kilometers north of the small town of Van Horn, Texas.

That is something SpaceX founder and Chief Executive Elon Musk, whose company has at least 17 reusability experiments under its belt, has chided Blue Origin about in the past. Late last year, Musk pointed out that “Blue Origin has not yet succeeded in creating a reliable suborbital spacecraft, despite spending over 10 years in development.”

SpaceX, on the other hand, has practiced rocket recovery maneuvers several times during revenue launches, including two in which the company steered the core stage of its Falcon 9 rocket to a simulated landing at sea following launches this year for NASA and Orbcomm.

Since 2012, SpaceX has also has also conducted 13 low-altitude test flights at its experimental rocket range near McGregor, Texas. Eight of these were with the company’s Grasshopper vertical-takeoff, vertical-landing test rig, Grasshopper. The remaining five were with the F9R, essentially a Grasshopper adapted to mimic the features of the Falcon 9 1.1 rocket SpaceX put into service in 2013.