WASHINGTON — SpaceX will provide an update Sept. 28 on the progress it’s making on its next-generation Starship vehicle, including plans to start flying a prototype in as soon as a month.

Elon Musk, founder and chief executive of the company, is set to discuss work on Starship in a presentation at the company’s South Texas test site at Boca Chica, near Brownsville, Texas. The event is expected to be webcast, although the company hasn’t disclosed specifics.

Musk, meanwhile, has been providing updates from the Boca Chica site as crews there work to assemble the first Starship prototype, called Mark 1. In recent days Musk has been tweeting images of the vehicle, including a view of its three Raptor engines installed in the base of the vehicle.

An earlier prototype, Starhopper, flew Aug. 27 from the site, ascending to an altitude of 150 meters before landing on a neighboring pad a minute after takeoff. That vehicle, powered by a single Raptor engine, won’t fly again, with the company instead using it as an engine test stand.

Three Raptors on a Starship pic.twitter.com/UrRiD62EVk — Elon Musk (@elonmusk) September 26, 2019

The Starship Mark 1 vehicle being built at Boca Chica will start flying in the near future on high-altitude test flights. “This is quite a complex beast, but hopefully within a month or so,” Musk said Sept. 26 when asked on Twitter when he expected the vehicle to make its first flight.

This is quite a complex beast, but hopefully within a month or so — Elon Musk (@elonmusk) September 26, 2019

That schedule is likely dependent on not just the technical progress the company makes on the vehicle, but also getting approvals, such as an experimental permit or launch license from the Federal Aviation Administration. The Starhopper test flight was pushed back because of challenges modifying SpaceX’s existing FAA permit for the vehicle because of hazard analyses. The FAA did ultimately modify the permit, but allowed only a single flight to 150 meters altitude and greatly increased the company’s third-party liability requirement.

Musk has also discussed some design changes to the vehicle he’s expected to elaborate upon at the upcoming presentation. The Mark 1 vehicle has two fins and six landing legs, a departure from prior designs that had three fins, with landing legs incorporated into them. The six landing legs, he tweeted, provide “redundancy for landing on unimproved surfaces,” he said.

As for the two fins, Musk said that choice was driven by vehicle mass. “Current analysis, which I’m not fully bought into, suggests that 2 rear fins with separate airframe-mounted legs will be lighter, so this is the plan for Mk1/Mk2,” he tweeted. Mark 2 is a separate Starship prototype SpaceX is building in parallel in Cocoa, Florida, near Cape Canaveral.

Current analysis, which I’m not fully bought into, suggests that 2 rear fins with separate airframe-mounted legs will be lighter, so this is the plan for Mk1/Mk2 — Elon Musk (@elonmusk) September 22, 2019

The vehicle has smaller fins at the top of the vehicle as well. “Nose tip has forward movable fins, cold gas attitude control thrusters, header tanks for landing, composite pressure vessels, several large batteries, etc.,” he said, whose mass is intended to balance the Raptor engines and fins at the base of the vehicle.

The entire mass of the vehicle is about 200 tons “dry,” or unfueled, and 1,400 tons when filled with liquid oxygen and methane propellants, Musk said. That dry mass, though, will go down in future versions, with SpaceX “aiming for 120 [tons] by Mk4 or Mk5.”

While Starship will perform vertical takeoffs and landings from both Boca Chica and the Kennedy Space Center, where SpaceX plans to test fly the Mark 2 version of Starship, the vehicle will eventually be the upper stage launched on a large booster called Super Heavy. Musk, though, said that developing Super Heavy, which will have more than 30 Raptor engines, will be less challenging to build than Starship.

“Super Heavy rocket will be much like Falcon 9,” Musk tweeted, “but the Ship is a strange combination of Dragon, F9 & a skydiver.”