What could be more patriotic than a shuttle launch on the Fourth of July?

Six years ago, the STS-121 crew of the space shuttle Discovery celebrated Independence Day with the ultimate in fireworks, burning through the mid-afternoon sky on their way to the International Space Station. The launch was very eagerly anticipate -- the first in roughly a year and only the second in the last three and a half years. It was a long-awaited event brought to spectacular life to mark a patriotic celebration. It couldn't have been planned any better.

And, in fact, it wasn't.

If things had gone according to plan, there would have been no Fourth of July launch for STS-121; the shuttle should have already docked with the space station by July 4, rather than just then be leaving the ground.

The story started years earlier. In February 2003, NASA had lost the space shuttle Columbia during re-entry. For two and a half years, the space shuttle fleet was grounded as engineers worked to determine the problems that had caused the loss of Columbia and her STS-107 crew, and to address those issues so that the shuttle could fly safely again. Visitors to the U.S. Space & Rocket Center can learn more about what happened to Columbia and what was done to address those issues in a collection of artifacts about the tragedy.

The investigation and efforts to fix the problems came to a culmination in July 2005, when Discovery launched on the STS-114 "Return To Flight" mission, intended to demonstrate that the fixes had been successful and the shuttle was ready to resume the assembly of the International Space Station. Unfortunately, the mission proved just the opposite. During the STS-114 launch, foam came off of the shuttle's external fuel tank; the same issue that had led to the loss of Columbia. Fortunately, the foam did not damage the orbiter (and the crew would have been better prepared to deal with it if it had), but it still demonstrated that there was more work to do. Another "Return to Flight" mission was added to the schedule, dubbed STS-121 since the 115 through 120 missions had already been planned.

The work took yet another year, and in July 2006, a year after STS-114 and three and a half years after STS-107, the STS-121 crew was ready to fly, attempting once again to prove that the shuttle was as safe as possible.

Engineers and mission planners had all signed off. Discovery would be ready to go on July 1, 2006.

But for all the members of the NASA team that had approved the launch date, the weather still had to concur before the shuttle could fly.

A huge crowd had gathered on the Florida "Space Coast" on Saturday, July 1, for the launch, excited to see the shuttle fly again after so long. That afternoon, they left the coast disappointed -- the weather violated launch rules at the end of the countdown, and the launch was pushed back a day.

The next day, on July 2, a much, much smaller crowd returned to try again. Some of those who had been there the day before had been disappointed by the scrub and hadn't come back. Others were discouraged by the weather conditions that day -- while the weather had looked good to the average viewer most of the time on the 1st, it was very clearly bad on the 2nd, with rain falling in the hours leading up to the scheduled launch time, and not anticipated to improve. The astronauts and launch complex crew continued with preparations anyway, until finally the time came to take the important step of closing and sealing the crew cabin hatch. The orbiter called over to launch control to find out whether there was any point in continuing. Launch control told them they could go ahead and get out of the vehicle -- launch was scrubbed yet again.

No launch attempt was made the next day, and on the attempt the following day, things went perfectly, and Discovery roared into space spectacularly. It was an amazing launch, and the fact that it occurred on the Fourth of July made it seem that much more special.

Every once and a while, things go perfectly according to plan.

But other times, things only seem perfect because of the little speed bumps that made them end up that way.

Contributing Author: David Hitt