SAN DIEGO -- Preliminary renderings unveiled this week by the San Diego Chargers for a new stadium downtown show a retractable roof and artificial turf field for the $1.8 billion project.

If approved by voters in November, Chargers stadium advisor Fred Maas said the earliest a stadium could get completed is 2021.

“If all the stars and the moon were aligned -- which I’ve rarely seen in San Diego -- but if they were, I would like to think that we could be playing in the 2021-22 season,” Maas said.

Manica architecture is serving as the team’s architectural firm for the project.

According to Mass, there was a lot of back and forth in the organization on whether the new stadium would have a grass field, like Qualcomm Stadium, or a more practical synthetic turf field.

“It’s been an internal debate here, as you can imagine,” Maas said. “Obviously, the football folks want a grass field. We have some of our fans and sponsors that want an open-air stadium. It’s San Diego, remember. But you have to make concessions to make this work.

“We think we’ve kind of reached a really fair compromise of the design elements to really accomplish a facility that is more than just 10 days a year.”

Maas said the team looked at other alternatives, including a movable grass field like University of Phoenix Stadium uses for the Arizona Cardinals, but there’s not enough room to make the mechanics work.

So, as it stands now, tentatively the stadium will have a turf field. Maas said the main issue is covering the field for convention use without destroying the grass.

Chargers general manager Tom Telesco said he had no problem with his players performing on fake grass.

“I don’t think I should be picky or choosy with it, No. 1,” Telesco said. “No. 2, I kind of know where I stand in the pecking order. If they say we will play on FieldTurf, then it’s FieldTurf. If they say grass, it’s grass.”

In terms of the stadium room design, Maas said the Chargers’ stadium will more closely resemble the configuration of Dallas Cowboys’ facility, AT&T Stadium, which also has a retractable roof.

The roof at the Chargers' stadium will be made of the same material used for the Minnesota Vikings new facility, U.S. Bank Stadium.

The Vikings used ethylene-tetraflouroethylene, or ETFE – a plastic-like material that is transparent but can be treated to be translucent, is extremely light weight, very durable and resistant to corrosion.

Maas said because of the tight footprint, the stadium will be much more intimate than Qualcomm Stadium, with fans right on the field. Maas said the stadium can expand to 75,000 for Super Bowls, but also could serve as an intimate setting for San Diego State football games or a Major League Soccer franchise, similar to the way CenturyLink Field is used for the Seattle Sounders.

Stadium design accommodates 100,000 square feet of open exhibit space with a 200-foot ceiling, so the stadium could host boat shows and other events the current convention center space could not host, Maas said.

Maas believes it’s not unreasonable to assume the new facility could host 200 to 250 non-football days a year, and it’s one of the reasons the Chargers decided to put a retractable roof on the preliminary renderings for the project.