CAPE CANAVERAL, Fla. -- NASA opened an exhibit Friday honouring the astronauts in the Apollo 1 fire -- 50 years to the day they died.

The hatch from the burned spacecraft is the main draw. It had been concealed, along with the capsule, for a half-century. On Friday's anniversary, the hatch that trapped Gus Grissom, Ed White and Roger Chaffee inside their capsule at the launch pad finally went on display.

The public exhibit at Kennedy Space Center also includes the redesigned hatch on the spacecraft that sent men to the moon. Twenty-four astronauts flew to the moon during the late 1960s and early 1970s, and 12 walked its surface.

Families of the Apollo 1 crew got a private tour Wednesday and attended a memorial Thursday. They were back for Friday morning's grand opening and had one last event: an early evening ceremony at the abandoned pad where the accident occurred at 6:31 p.m. on Jan. 27, 1967.

Relatives of Grissom, White and Chaffee filled four long rows of black-draped chairs in front of the exhibit, along with Apollo astronauts Tom Stafford and Charlie Duke, and NASA dignitaries. Astronauts from the space shuttle and station era stood on the sidelines, along with space centre workers, past and present, and a few tourists.

As he joined others in walking through the exhibit, Kennedy's associate director Kelvin Manning said the message still rings true these many decades later, as NASA looks ahead to the commercial space effort and eventual journeys to Mars.

"We want to honour the crew," he said. "We also want people to pause ... we want to understand the risks so we can ensure our astronauts' safety."