NASA Honors Fallen Astronauts in 'Day of Remembrance' Ceremonies Today

To honor the upcoming anniversaries of three deadly disasters that claimed the lives of 17 NASA astronauts over the years, the space agency will host its annual Day of Remembrance ceremony at Arlington National Cemetery in Virginia today (Jan. 25).

This time of year is always somber for NASA, with the anniversaries of the Apollo 1 fire, the explosion of the space shuttle Challenger and the loss of the space shuttle Columbia all happening over the span of just five days.

These tragic accidents occurred decades apart, and the fact that their anniversaries are so close together is just a coincidence. Every year, NASA takes this depressing streak of anniversaries as an opportunity to honor all of the lives that have been lost over the course of its human-spaceflight program. [Fallen Heroes of Space Exploration: A Memorial (Gallery)]

During today's ceremony, NASA acting Administrator Robert Lightfoot and other senior officials will lead an observance starting at 10:25 a.m. EST (1525 GMT) followed by a wreath-laying ceremony at the Tomb of the Unknown Soldier.

"Various NASA centers also will hold observances on and leading up to the Day of Remembrance for the public, employees and the families of those lost in service to America's space program, including Johnson Space Center in Houston and Marshall Space Flight Center, in Huntsville, Alabama," NASA officials said in a statement.

At Kennedy Space Center in Florida, the Astronauts Memorial Foundation will host a ceremony in which daughters, sons and widows of the fallen astronauts will speak. Astronaut Eileen Collins, NASA's first female space shuttle commander, will also speak at this event. Members of the public are welcome to attend.

NASA TV will not broadcast these events, but those who cannot attend can learn more about the Day of Remembrance in a special multimedia presentation that the agency published online this week.

The three tragedies

The first fatal accident to ever befall NASA astronauts happened before the crew members even made it to their scheduled launch date. On Jan. 27, 1967, during a prelaunch rehearsal test about a month before their planned launch, a fire erupted inside the Apollo command module. Trapped inside were all-star astronauts Gus Grissom, Ed White and Roger Chaffee.

Investigators later determined that the cause of the fire was totally preventable and was rooted in flaws in the spacecraft's design. An electrical spark started the fire, and combustible materials inside the spacecraft — combined with a pure-oxygen atmosphere — caused the fire to spread rapidly. The doors of the command module were built to open inward, which prevented the astronauts from opening the door as fire consumed the spacecraft. [Photos of the Apollo 1 Fire: NASA's First Disaster]

Then 19 years later, tragedy struck again. On Jan. 28, 1986, the space shuttle Challenger exploded 73 seconds after lifting off from Kennedy Space Center. All seven crewmembers (five NASA astronauts and two payload specialists) were killed as the shuttle disintegrated over the Atlantic Ocean. Investigators once again blamed the accident on design flaws. Specifically, a device known as an O-ring, which was designed to separate the sections of the rocket booster, had failed due to cold temperatures on the morning of the launch.

NASA made design changes after the Challenger disaster in an attempt to make the space shuttle safer. Seventeen years passed before the next fatal space shuttle disaster. On Feb. 1, 2003, the space shuttle Columbia broke apart as it returned to Earth after a two-week mission, killing the seven-person crew. This time, a piece of foam had broken off the shuttle's external fuel tank during launch and collided with the shuttle's left wing, damaging the heat shield. This didn't seem deadly at first — only when the spacecraft re-entered Earth's atmosphere did the extent of the problem become apparent.

Every time NASA has experienced tragic loss of human life during spaceflight missions, the agency has taken time to re-evaluate and redesign its spacecraft in order to prevent more tragedies like these from happening again. But spaceflight is inherently dangerous, and as all three of these incidents illustrate, potentially catastrophic issues are most easily recognized through hindsight.

 Email Hanneke Weitering at hweitering@space.com or follow her @hannekescience. Follow us @Spacedotcom, Facebookand Google+. Original article on Space.com.