Editor's Note: (Leroy Chiao is a former NASA astronaut and commander aboard the International Space Station. During his 15-year career, he flew four missions into space, three times on space shuttles and once as the copilot of a Russian Soyuz spacecraft to the International Space Station. On that flight, he served as the commander of Expedition 10, a six-and-a-half month mission. He has performed six spacewalks, in both US and Russian spacesuits, and has logged nearly 230 days in space. The opinions expressed in this commentary are solely those of the author. )
(CNN) The dream of flight began with early humans, who watched birds dart back and forth and soar high above. This dream extended to spaceflight, as humans realized that there is more above than just our sky, that the stars are like our sun and that there are planets orbiting those stars.
For me, the dream of spaceflight started at an early age. We were just taking the first steps to fly into space by the time I was old enough to understand what was happening. I watched with excitement as America planned the Apollo missions, which would fly us to the moon.
Then, tragedy struck, with the Apollo I fire. Astronauts Gus Grissom, Ed White and Roger Chaffee were killed in their spacecraft, while still on the ground during what was supposed to be a routine test. The nation was in shock. We had never lost astronauts before.
True to form, NASA thoroughly investigated the accident, lessons were learned, changes were made and we flew again, launching the crew of Apollo 7 into orbit less than two years later, and flying Apollo 11 to the moon less than a year after that.
This helps to put into perspective what happened Thursday.
A SpaceX Falcon 9 rocket and payload were lost on the launch pad during preparations for a routine test. During propellant loading for a hot-fire test to check engines and the fuel system, something went wrong and there was a catastrophic explosion, which completely destroyed the vehicle and damaged the pad. Thankfully, nobody was hurt.
Nearly 50 years separate the Apollo I fire and this mishap.
Why do we still lose rockets, spacecraft, and sometimes crew? The fact is that we have advanced the state of the art, but the physics haven't changed, and they won't.
To accelerate a spacecraft to Earth orbital speed of about 17,500 mph takes a lot of energy. There are a lot of moving parts and propellant involved. And risks. Those fundamental risks won't change much until we make a major breakthrough in propulsion technology that makes delivery of that energy more safe and reliable.
As with other mishaps, I have no doubt that the investigation will be thorough and that the root cause of the failure will be determined. Lessons will be learned, fixes made, and SpaceX will fly again.
Failures are not, and should not, be taken lightly. We do not simply accept that they are just going to happen. But everyone must understand that what is being undertaken here is complex and difficult. Risks are managed and reduced as much as is practical, but they can never be zero. The only way to make them zero is to not try at all.
People often ask me how I felt about the risks when I climbed into space shuttles and a Soyuz spacecraft for launch. To be sure, I knew that the risks were real. The space shuttle was the most complex and capable spacecraft ever built and operated. We lost two spacecraft during the life of the program, along with 14 crew members.
Soyuz has also had its share of mishaps and near misses. But, I made peace with myself before each flight. I knew that everyone working on the program had done his and her best to make sure that the risks were managed as best as possible, but that they were not zero, and never would be. I believed that what I was venturing off to do was worth the risk.
So, yes, this is a big setback for SpaceX, but these dedicated people will pick up the pieces and move forward. This is what can-do people are about. We are not quitters. We will continue to push the boundaries and take managed risks to do so. We believe that it is worth it.