LAS CRUCES, N.M. — A day after NASA indicated its willingness to proceed with plans to add a commercial module to the International Space Station, two companies provided updates on proposals to supply such a module.

In back-to-back presentations at the International Symposium for Personal and Commercial Spaceflight (ISPCS) here Oct. 12, Axiom Space and Bigelow Aerospace said they’re proceeding with development of modules that could be added to the ISS as soon as 2020, depending on how NASA decides to select a module to add to the station.

Michael Baine, lead design engineer at Axiom Space, said that the company has completed a systems requirements review of its proposed module and plans to start a preliminary design review in December. The company has raised an undisclosed seed round of investment to support that work.

That module, he said, would be the largest module on the ISS. “It’s comparable to taking the U.S. laboratory module and Node 2 and putting them together,” he said. The module will have its own propulsion to allow it to dock with the station on its own after launch. It will also have its own life support and power systems, enabling it to support up to seven people at a time.

Axiom envisions the module later detaching from the ISS once the space station is retired and forming the core of a commercial space station with the addition of other modules and related elements. “The Axiom plan is to start with a module, but then eventually leave ISS after end of life,” he said, “and then bring a lot of that science and core mission of the ISS with it to a new commercial space station.”

Bigelow Aerospace is moving ahead with plans announced earlier this year to have two of its B330 expandable modules ready for launch by 2020, with the option of installing one of them on the ISS. Robert Bigelow, chief executive of Bigelow Aerospace, said the company is currently working on a series of ground test articles that will allow the company to “leave our mistakes on the ground” prior to launching the B330 modules.

Bigelow has been working on expandable module technology for more than 15 years, but believes that the crew transportation systems needed to make commercial space stations viable are finally ready. “I have throttled my company back and fourth two or three times because of the transportation problem,” he said. “This is the first time that I have ever really decided that it looks like it’s close enough.”

A key issue for both companies, either for commercial ISS modules or standalone space stations, is getting the modules launched. Baine said that the large size of the their module limits their launch options, and that the company is “notionally” considering SpaceX’s Falcon Heavy to launch it.

Bigelow said it’s planning to use the most powerful version of the Atlas 5 to launch its B330 modules, under an agreement his company announced with United Launch Alliance earlier this year. Bigelow said, though, that the company’s funds currently only cover the development the B330 modules, and not their launch.

Bigelow said the company may pay for the launches through either revenue from customers for those modules, or by taking in new investors. “It could be countries, it could be large companies, it could be people who aren’t even affiliated with the space world,” he said of potential investors.

Axiom Space and Bigelow Aerospace are two of 11 companies that responded in August to a NASA request for information (RFI) about adding a commercial module to the ISS, making use of a docking port currently occupied by the experimental BEAM module built by Bigelow Aerospace for NASA. In a blog post published on the NASA web site Oct. 11, NASA Administrator Charles Bolden and John Holdren, director of the White House’s Office of Science and Technology Policy, said that the responses to the RFI led NASA to decide to move ahead with plans to offer that port to commercial users.

The agency is still evaluating the responses to the RFI, said Bill Gerstenmaier, NASA associate administrator for human exploration and operations, in an Oct. 12 speech at ISPCS. A challenge, he said, is figuring out how to best make that single docking port available given the interest from several companies. “We’re honestly struggling with that right now,” he said, adding NASA should provide more details about its plans by the end of the year.

“It’s going to be very interesting how they’re going to do that,” said Baine. He noted Axiom’s proposed module will have several docking ports of its own so that additional modules or spacecraft could dock to it. “We’re giving back more than we’re taking.”