Our top two stories this week have been the troubles encountered by NASA's Curiosity rover and SpaceX's Dragon capsule. Both faced unexpected, but not mission-threatening problems, so how have they fared?
After a flawless launch aboard the Falcon 9 rocket, Dragon faced trouble with its maneuvering thrusters. Three of the four thrusters failed to properly activate, stranding the ship in Earth orbit, but unable to approach the International Space Station. Analysis showed that the malfunction was due to a stuck propellant valve restricting flow of fuel to the mini-rockets. SpaceX engineers initiated a "pressure hammering" of the valve by rapidly trying to open and close it. This action eventually freed the valve, restoring proper functionality to all four thrusters. Dragon has now successfully docked with the ISS and completed its mission of delivering supplies and equipment to the astronauts there. While such a malfunction is a bit troubling for a new spacecraft design like Dragon, I was far more impressed with the ability of SpaceX to diagnose and solve the problem in such a way to restore full functionality. Even the best designs will suffer malfunctions - what counts is the ability to recover.
While Dragon was hampered with mechanical failures, Curiosity has suffered software problems. Late last week the Mars rover was placed in safe mode in response to issues with its memory banks. While in safe mode, Curiosity can continue communicating with Earth and performing critical functions, but all science operations are suspended. Fortunately, Curiosity carries two identical computers for just these sorts of circumstances. It will take time to fully diagnose the problems afflicting the "A" computer, so late today flight engineers successfully transferred control of the rover to the "B" computer. After information about the state of the rover is programmed into this system, it will allow Curiosity to continue its mission shortly. Again, adaptability has carried the day. The Mars Science Laboratory (Curiosity's real name) team must be a bit nervous about this development, however. Unless the issue turns out to be a common software problem, it's a bit unnerving for one of the rover's computers to fail so early in the mission. I'll keep my fingers crossed!