SpaceX aims to start flight-testing key design components of its Mars-settling spaceship next year, company founder and CEO Elon Musk said.

The plan involves upgrading the upper stage of SpaceX's workhorse Falcon 9 rocket "to be like a mini BFR Ship," Musk said via Twitter Wednesday (Nov. 7).

"Aiming for orbital flight by June," he said in another tweet. [The BFR in Images: SpaceX's Giant Spaceship for Mars & Beyond]

The BFR, or Big Falcon Rocket, is the giant, reusable launcher SpaceX is developing to help settle Mars and perform a variety of other spaceflight feats. Each rocket will be topped by a 100-person spaceship (the BFS), which will be capable of completing many roundtrip journeys to the Red Planet, Musk has said.

An artist's illustration showing SpaceX BFR spaceships on the surface of Mars. (Image credit: SpaceX)

The upcoming Falcon 9 modification will apparently help SpaceX better understand some of the more demanding flight regimes the BFS will experience.

"Ultra light heat shield & high Mach control surfaces are what we can't test well without orbital entry," Musk said in another tweet.

The newly redesigned upper stage won't make a propulsive landing here on Earth, as about 30 Falcon 9 first stages have done to date (and as the BFS will do on the surface of Mars, the moon and other cosmic destinations), Musk said.

"I think we have a handle on propulsive landings," he tweeted. In yet another tweet, he added that SpaceX is building a "BFR dev ship to do supersonic through landing tests in Boca Chica, Texas." That site in South Texas will be the company's hub for BFR and BFS testing, SpaceX representatives have said.

If everything goes well with BFR-BFS development, the duo could begin carrying people to Mars by the mid-2020s, according to Musk. The long-term goal is to help establish a million-person city on the Red Planet — ideally, within the next 50 to 100 years.

SpaceX envisions handing over all of its spaceflight work to the BFR and BFS eventually. The system will be able to do all that SpaceX asks of it, from launching satellites to Earth orbit to cleaning up space junk to ferrying people on superfast "point to point" trips here on Earth, Musk has said.

Mike Wall's book about the search for alien life, "Out There," will be published on Nov. 13 by Grand Central Publishing. Follow him on Twitter @michaeldwall. Follow us @Spacedotcom or Facebook. Originally published on Space.com.