The opening of Christopher Nolan’s “Interstellar” is still almost three weeks away, but tickets for the space adventure are going fast.

Like all of Nolan’s projects, “Interstellar” remains cloaked in secrecy. Its plot is a mystery besides a few clues that it will center on an ecological cataclysm on earth and wormholes. It’s not a sequel, it’s not based on a young adult bestseller or a toy. Instead, it’s a wholly original concept.

After the success of “The Dark Knight” films and “Inception,” Nolan has become a brand in and of himself and “Interstellar” is performing as well as popular franchise pictures.

The picture is looking at a debut of more than $50 million based on early tracking and that number could rise as reviews roll in, television commercials become ubiquitous and word-of-mouth increases. An opening in the range of “Gravity’s” $55.8 million seems achievable, even though Disney’s animated “Big Hero 6” opens the same weekend and is also generating excitement with potential ticket-buyers.

Fandango reports that pre-sales for the picture are outpacing “Inception” at a similar point in its sales cycle and last summer’s sci-fi hit “Dawn of the Planet of the Apes,” which debuted to $62.8 million and $72.6 million, respectively. It has been one of the online ticketer’s top performers since going on sale on Oct. 1, and often appears among the top five most popular movies. MovieTickets.com says it has seen similar results.

“I fully expect to be sold out through the weekend,” said Tom Stephenson, CEO of Look Cinemas, which reports that Tuesday and Wednesday night showings are already booked. “I’m a big Chris Nolan fan, so I expected the response would be great, but to have sell outs this early is incredible.”

The film stars Matthew McConaughey, Anne Hathaway and Jessica Chastain and is being distributed stateside by Paramount with Warner Bros. handling the foreign rollout. Nolan brought the film in on time and $10 million under its $175 million budget, according to an individual with knowledge of the production.

“Interstellar” is also unusual in that it is being presented in a wide variety of formats. Nolan shot the film on film, which he believes provides more visually dynamic, lustrous images than digital cameras. It will be projected digitally, but also in 35mm and 70mm film formats and in Imax 70 mm.

Tickets to shows in those formats have been a particularly hot commodity and early Imax and 70 mm screenings of the film are starting to sell out in many major theaters. The TCL Chinese Theatre, which boasts the world’s largest Imax screen complete with a 900-seat auditorium, moved thousands of tickets within two hours of making them available. “Interstellar” holds the theater’s record as its biggest pre-seller ever.

“You want to see it right,” said Alwyn Hight Kushner, president and COO of the TCL Chinese Theatre. “This is a big event movie. You can’t watch it on a TV screen. It’s not a Netflix movie. It’s a real film that you need to see in cinemas.”

Some Imax theaters have added 3 and 3:30 a.m. screenings following Tuesday midnight shows, as well as 8 a.m. showtimes on Wednesday to keep up with the demand.

Showing “Interstellar” in 70 mm has required a financial commitment on the part of theater owners. Brian Schultz, CEO of Studio Movie Grill, is paying $35,000 a screen for the projectors. However, Nolan has gone out of his way to express his gratitude to exhibitors who made the investment, even calling Schultz personally to thank him.

“We thought it was prank,” said Schultz. “He was really appreciative that we put in the effort to restore units and support his vision. … But if Christopher Nolan wants to show a movie in film, we’re going to show it that way.”

Schultz’s decision to screen “Interstellar” in 70 mm has commercial benefits as he reports that he’s nearly sold out through the first weekend, but there are also drawbacks to success.

“We’re down to literally front rows for the entire first week,” he said. “My daughter was excited about ‘Interstellar’ and wanted to have a party, but we waited too long. They were up for one day and we weren’t able to get enough tickets.”

Like a lot of moviegoers, Schultz’s daughter will have to wait a week to see what the fuss is about.