CNN Video screenshot by Eric Mack/CNET

It's perhaps the nerdiest troll war ever. SpaceX CEO Elon Musk and NASA administrator Jim Bridenstine have been clapping back at each other over spacecraft, and it's getting pretty epic.

It all began when Bridenstine put out a statement on Twitter ahead of Musk's big reveal of his new Starship rocket prototype Saturday. This is the huge new craft Musk sees as empowering his magnum opus: a city on Mars. But Bridenstine was quite the party pooper with this troll job:

"I am looking forward to the SpaceX announcement tomorrow. In the meantime, Commercial Crew is years behind schedule. NASA expects to see the same level of enthusiasm focused on the investments of the American taxpayer. It's time to deliver."

Commercial Crew involves SpaceX and Boeing developing spacecraft that can ferry astronauts from US soil to the International Space Station.

Musk addressed the NASA head's gentle parental nagging during his Starship update from Texas Saturday, saying, "From a SpaceX resource standpoint, our resources are overwhelmingly on Falcon and Dragon (Crew Dragon is part of NASA's Commercial Crew program) ... It was really quite a small percentage of SpaceX that did Starship."

But after he left the stage, Musk turned it up to full burn mode in an interview with CNN when he was asked to respond to Bridenstine's tweet once again.

“Jim Bridenstine said, quote, Commercial Crew is years behind schedule & it’s time to deliver. Did you take that ...”



“Did he say Commercial Crew or SLS?”



This is it. The finest burn in history. @elonmusk 😀 pic.twitter.com/lvlnzvIXbt — Viv (@flcnhvy) September 29, 2019

"Did he (Bridenstine) say Commercial Crew or SLS?" Musk asked with full-on snark before mugging his best troll face for the camera and cracking himself up for nearly 10 seconds.

The joke here is that Musk is referring to NASA's next-generation Space Launch System, which is over budget and years overdue. So much so, in fact, that there's been talk of NASA just cutting its losses, canceling SLS and contracting with SpaceX for future SLS launches, like the planned Artemis mission to return to the moon.

"Everything in aerospace is years behind, OK?" Musk went on to say. "Relatively speaking, which one is more late ... we're really going as fast as we can make it go."

Bridenstine's spokesperson sent the following statement when asked for a response to Musk's comments:

"Administrator Bridenstine is working to make the agency and its commercial partners accountable for cost and schedule, in addition to safely carrying out NASA's missions. Bridenstine continues to emphasize that the return of launches of American astronauts, on American rockets and spacecraft, from American soil should be the top priority for NASA's Commercial Crew partners."

Now playing: Watch this: Elon Musk unveils SpaceX Starship rocket, UK pushes for...

Musk had hoped to send the first astronauts to the International Space Station in a Crew Dragon earlier this year, but a testing mishap on the ground led to the explosion of a Crew Dragon unit and set back that timeline. No one was hurt in the explosion.

Musk's sick comeback is fair, but so is Bridenstine's original questioning of Musk's priorities. SpaceX's success as a business over the past 17 years has come thanks in large part to NASA's continued support in the form of several huge contracts.

It's fun and maybe even satisfying on a certain level to see the two biggest names in the rocket game engage in a real-life rap battle, but in the end both of the delayed spacecraft being used as rhetorical ammunition were paid for with American taxpayers' dollars. In other words, in this war of words, it's really the public that's losing.

Originally published Sept. 30.

Update, Oct. 1, 11:31 a.m. PT: Adds comment from Bridenstine's office.