This week marks the most somber seven days in NASA history as Brevard County remembers the fallen astronauts of Apollo 1 and space shuttles Challenger and Columbia.

NASA will mark the three tragedies at a ceremony at the Kennedy Space Center Visitor Complex on Friday, Jan. 31. KSC Director Bob Cabana will lay a wreath at the Space Mirror memorial, dedicated to all fallen astronauts and service members who died while helping further America's space program.

Seventeen astronauts died in three different tragedies over a nearly 50-year span, including one flight that never got off the ground -- the first manned mission of the Apollo program.

Apollo 1

On Jan. 27, 1967, the three-member crew of Apollo 1 -- Gus Grissom, Edward White and Roger Chaffee -- were inside the capsule during a dress rehearsal, when a fire ignited inside the oxygen-rich atmosphere, killing all three men.

The program was suspended for nearly two years to fix major flaws in the capsule's design.

Approximately 75 people, including Grissom's widow Betty, attended a ceremony to the 47th anniversary Monday.

Challenger

On Jan. 28, 1986, space shuttle Challenger lifted off on the well-publicized "Teacher in Space" mission. Among the seven-member crew was Christa McAuliffe, the first educator selected to go to orbit.

Then, 73 seconds after launch, a seal on one of the solid rocket boosters failed. The booster detached, the external tank broke apart, and the shuttle was destroyed.

"I came to realize I never really came to grips with it," says Hugh Harris, formerly of NASA Public Affairs.

Harris is now retired from NASA, but was working that fateful day. He said he and the staff began working round the clock to deal with the disaster seen by millions on live television.

Harris has written a book about the experience, Challenger: An American Tragedy - The Inside Store from Launch Control.

"What made Challenger grip the American people was that it was the first time we had people die during a spaceflight," said Harris.

Astronauts Ellison S. Onizuka, Greg Jarvis, Judy Resnik, Michael J. Smith, Dick Scobee and Ron McNair also died in the Challenger disaster.

Harris' e-book debuts online Tuesday, 28 years after the tragedy.

Columbia

Seventeen short years later, tragedy struck again.

On Feb. 1, 2003, Space shuttle Columbia was minutes away from landing at the Kennedy Space Center after a successful, 16-day mission, when the orbiter disintegrated over Texas, killing all seven astronauts on board: David M. Brown, Rick Husband, Laurel Clark, Kalpana Chawla, Michael P. Anderson, William McCool and Ilan Ramon, a payload specialist from the Israeli Space Agency.

Investigators later learned a piece of foam from the external tank struck the shuttle during liftoff.

Mourners are also expected to gather Saturday to remember the Columbia disaster 11 years later.