Joseph Kerwin, an astronaut- physician who investigated the cause of death for the crew. You can follow senior writer Clara Moskowitz on Twitter ClaraMoskowitz.The astronauts probably survived the explosion and breakup of the shuttle orbiter and could have had 6 to 15 seconds of вЂіuseful consciousnessвЂі inside the crew compartment after the blast, said Dr. 'A lot of the lessons learned in this business are written in blood, and if we don't learn from them, those people died in vain.' 'It's a time to reflect and it's a time to remember those people who have sacrificed to get us where we are,' Garan told.

Veteran shuttle astronaut Ron Garan, who is slated to fly to the International Space Station in March aboard a Russian Soyuz spacecraft, said the anniversaries of Challenger and the other accidents highlight the lessons learned from those events. The calamity led to a thorough redesign of the Apollo capsule before any subsequent missions. In addition, the latched and pressurized hatch of the capsule was not designed for a quick escape. In particular, a review board determined that the presence of large amounts of Velcro and other flammable materials made the capsule extremely vulnerable to fire. The Apollo 1 fire, the first fatal accident for NASA astronauts, was eventually attributed to a number of design and construction flaws in the space capsule. 'People were trying to do their job to the best of their ability it's just that there were holes in their outlook.'

'It certainly was a total misunderstanding of the loss of foam and the damage it could do to the space shuttle orbiter,' Hale said. While engineers at the time didn't believe that the lightweight foam could inflict damage on the reinforced surfaces of the wing, tests later showed that, at the relative speed at which the foam was falling during launch, it probably punched a hole about the size of a dinner plate in one of the wing's panels, allowing hot plasma to damage its internal structure.ДЇew suspected during Columbia's two weeks in orbit that the shuttle had been harmed, and space shuttle crews now conduct a thorough examination of their orbiter's heat shield after every launch to make sure foam or other debris hasn't damaged the vehicle. An investigation found that a relatively small chunk of foam insulation from the shuttle's external tank had fallen off during liftoff 16 days earlier and struck the leading edge of the orbiter's left wing. We didn't fully investigate that to the extent we really needed to.'Д¬olumbia was destroyed when the shuttle's heat shield failed to protect it from the intense heat of re-entry to Earth's atmosphere. In almost all accidents, if you look back, there are indications ahead of the actual accident that something wasn't operating exactly the way we thought it was. When you see some small little event that appears innocuous or doesn't appear like a big deal, to really investigate that item that occurred. 'Another way to think of that it is to stay curious. 'The major lesson is really, I say to the team, 'Stay hungry,'' said Bill Gerstenmaier, NASA's associate administrator for space operations. Many in the spaceflight industry say the anniversaries are a reminder to stay vigilant for potential pitfalls and keep striving to make space travel as safe as possible. 'We wished that we had the foresight to stand up collectively and say, 'Look, it's too cold a day to launch, we just ought to wait for a warmer day.' In retrospect it seems so simple at the time, it just didn't happen.' 'The problem was a design flaw, complicated by the weather situation which was unrecognized at the time by the appropriate managers,' Hale said. The right solid rocket booster separated from the shuttle, and the fuel tank broke apart, causing the orbiter to be torn apart by aerodynamic stresses. An investigation board concluded that cold weather prevented a rubber O-ring from maintaining its seal, allowing hot gas to leak and damage the shuttle's external fuel tank and the hardware attaching the booster to the vehicle. The loss of Challenger was later attributed to a failed seal on one of the space shuttle's solid rocket boosters. NASA Administrator Charles Bolden and Deputy Administrator Lori Garver laid a wreath at Arlington National Cemetery in Virginia.

NASA held an agency-wide Day of Remembrance yesterday for the three fallen crews.

Space shuttle challenger