In 2015, one of the Falcon 9 rockets manufactured by SpaceX failed to launch properly. The first theory as to its demise was that a manufacturing defect had taken place. After careful research by NASA, it seems to be more likely that the incident was related to a design flaw. The mission in question is that of CRS-7. This mission meant to send the Dragon cargo unit to the International Space Station. SpaceX initiated an investigation to find out the nature of the problem, while NASA’s Launch Services Program performed their own.
As the teams made efforts to look into the situation, it proved difficult. The explosion happened exactly 139 seconds into the mission. It has been determined that the explosion began in the second stage oxygen tank. The sudden nature of the event initially made for more questions than answers. Usually, there are some preliminary signs leading to the issue. After careful consideration, it has been determined that a composite overwrapped pressure vessel (COPV) was the most likely cause. This COPV was filled with helium and is thought to have loosened from its resting place and headed upwards towards the top of the oxygen tank. When it hit the top dome of the tank, the impact may have caused the explosion.
The disagreement between NASA and SpaceX is related to the reasoning behind why the COPV became loose in the first place. SpaceX placed the blame on the defect of a bolt, referred to as a “rod end,” and discontinued use of the product in their future rockets. NASA concurs with the possible manufacturing defect, while also suggesting the possibility of faulty installation. NASA is also open to other theories about the event, and they believe a mistake in the design was part of the problem.
NASA is questioning the quality of the stainless steel used to manufacture the rod end. There are different grades of stainless steel, and the one used for space equipment is usually aerospace grade. SpaceX chose to use industrial grade for the rod end. The proper safety rating is not applied to this product, and it has not been tested for use in space, or launch related activity. NASA has released a formal statement, requesting that SpaceX reconsider its use of commercial products. NASA indicated that several parts of the Falcon 9 CRS-7, and possibly others, have been manufactured with commercial grade parts. This leaves them susceptible to the same fate. This could be even more serious if humans had been involved in the launch. Thankfully, this mission only involved cargo. SpaceX claimed that all issues have since been resolved.
If NASA approves of the efforts made by SpaceX, the next launch of cargo to the International Space Station should take off with a Falcon 9 CRS-14. A Transiting Exoplanet Survey Satellite (TESS) is also planned for takeoff. There is some speculation as to why the report on the 2015 incident is just now being brought to light. NASA simply stated that it required a written account of the incident. NASA mentioned their continued collaboration with SpaceX was due in part to the prompt attention to the resolution of the issues mentioned. A January 2016 launch also used a Falcon 9 rocket. This launce included the Jason-3 Earth observation satellite. At this time, the incident report has been of interest to Congress, and more information has been requested.