Space Exploration Technologies launched another Dragon capsule this morning, heading for the International Space Station. The launch of the Falcon 9 rocket was perfect, but the Dragon capsule has experienced some anomalies. SpaceX mission controllers have had trouble getting some of the thrusters online.

SpaceX founder Elon Musk explained the problem in a message to his Twitter followers: “Issue with Dragon thruster pods. System inhibiting three of four from initializing. About to command inhibit override.”

SpaceX now reports that vital signs on a second thruster pod are “trending positive.” When SpaceX has at least two pods restored, it will begin manuevering the capsule toward the space station. The loss of some thrusters could result a later-than-planned arrival at the space station. In the worst case, if SpaceX can’t get the second thruster pod working, the mission could be a total loss.

Some people have said that Dragon flights are becoming “routine,” but spaceflight will never be routine until we have reusable vehicles.

Expendable rocket and capsule: “We have a problem with our thrusters and can’t dock with the space station. Looks like we’ll have to abort the mission, lose the vehicle, the payload, and the $100 million customer payment. Space-station crew won’t have clean underwear for another three months. Life is tough.”

Reusable spacecraft: “We have a problem with our thrusters and can’t dock with the space station. Looks like we’ll have to return to base, call in the mechanics, and fly the mission again tomorrow. Space-station crew won’t have fresh sushi for another night. Life is tough.”

Because they don’t throw away expensive hardware, reusable vehicles can also afford more testing and redundancy. So, anomalies are less likely to occur and better tolerated when they do occur. For the most common failures, reusable vehicles are not only “fail safe” but “fail operational.” Most airline passengers are unaware of how often airliners suffer equipment failures in flight. Airliners have enough redundancy that when a piece of hardware fails, the pilots simply shut it down and report the failure to mechanics when the plane lands. Spaceflight needs to evolve to the same point.

Again, we’re just saying.