"On June 28, 2015, following a nominal liftoff, Falcon 9 experienced an overpressure event in the upper stage liquid oxygen tank approximately 139 seconds into flight, resulting in loss of mission."-- SpaceX statement

File
Last microseconds of NASA's Commercial Resupply mission CRS-7. Photo: NASA

When Orbital ATK's (NYSE:OA) Antares rocket exploded in the skies over Wallops Island, Va., last year, fingers pointed immediately at the rocket's engine maker, Russia's now-defunct Kuznetsov Design Bureau, as the culprit. Fixing blame for NASA's latest rocket disaster, however, won't be as easy.

And that's good news for Elon Musk's SpaceX.

What went wrong for SpaceX
As described by SpaceX in a statement released this week, everything was going swimmingly for its CRS-7 (Commercial Resupply mission No. 7) mission when it first lifted off from Cape Canaveral. For 139 glorious seconds, everything was "nominal." The rocket's first stage performed perfectly. Its Dragon space capsule remained intact, and even "survived the second stage event," and "continued to communicate until the vehicle dropped below the horizon and out of range."

So far as SpaceX can tell, the problems began when one single part within the Falcon 9 rocket's second stage failed, causing the now-infamous SpaceXplosion.

Strut

An aerospace strut like the one that failed aboard CRS-7. It doesn't look like much, but just one faulty strut brought down SpaceX's Falcon 9 rocket. Illustration: Swedish strut supplier SKF Group

Specifically, it appears that a two-foot-long steel strut -- one of several hundred built into the Falcon 9, responsible for holding the rocket's helium tanks in place -- snapped in half, failing under 2,000 pounds of stress, despite being designed to withstand 10,000 pounds. What happened next is uncertain. But with two pieces of hardware rattling around within a pressurized metal tube straining under more than three "Gs" of acceleration -- plus a loose helium bottle they were supposed to hold in place possibly tossed into the mix -- it probably wasn't good.

Long story short, the rocket blew up -- but it was neither the rocket's fault, nor the fault of the rocket maker, SpaceX.

Round up the usual suspects
Rather, SpaceX is (tentatively) placing the blame on a supplier of metal struts that it declines to name. Multiple companies supply such struts to the aerospace industry, including Sweden's SKF Group (whose strut is pictured above), Goodrich Aerospace, and even SpaceX rival Boeing (NYSE:BA). Wherever SpaceX bought its faulty strut, the company says the part seemed sound when installed -- but apparently wasn't. Subsequent tests of other struts in SpaceX's inventory have revealed instances of "weakness in the material." This suggests a quality-control issue that could have originated with the strut's manufacturer ... or even farther up the supply chain, at the factory that smelted the metal used to make the strut.

SpaceX is taking steps to ensure no more bad struts make their way onto SpaceX spaceships in the future. The company is switching suppliers, first of all, which may eliminate the problem at its source. SpaceX is also instituting "additional hardware quality audits ... to further ensure all parts received perform as expected per their certification documentation." And just in case, it's upping the tolerances on the parts it buys, to ensure each strut "has an even higher margin of safety."

What it means for SpaceX ... and for its rivals
All of this will take time, of course. Combined with the time needed to finalize its review of the "SpaceXplosion", and confirm it was indeed a faulty strut that caused the disaster, SpaceX says it's probably going to have to push off its next Falcon 9 flight into September.

According to Elon Musk, CEO of SpaceX, the delay will cost the company "hundreds of millions" in lost revenue, but will result in a safer spacecraft and happier customers in the long run.

Crucially, the fact that CRS-7 exploded not because of a design flaw, but because of a single faulty part, should allay concerns that SpaceX is a riskier rocket company than rivals Boeing (NYSE:BA) and Lockheed Martin (NYSE:LMT) -- whose United Launch Alliance joint venture has successfully launched its last 96 rockets into space without losing even one. While ULA's record certainly shines brighter than SpaceX's today, it appears SpaceX's Falcon 9 design is sound. The company just needs to tighten up its quality control over the parts its suppliers are sending.

Granted, this may increase costs somewhat, and narrow SpaceX's cost advantage over rockets launched by ULA. But it will still be cheaper than having to redesign the entire Falcon 9 rocket to fix a design flaw. And with SpaceX rocket launches starting out with as much as a four-to-one price advantage over ULA rockets, SpaceX can probably afford to nudge its costs a bit higher in the interests of safety.

Long story short, SpaceX is still in this game. Don't count the company out after one mishap.

Spacex Launch
Most of the time, SpaceX rocket launches look like this. Photo: SpaceX

Fool contributor Rich Smith does not own shares of, nor is he short, any company named above. You can find him on Motley Fool CAPS, publicly pontificating under the handle TMFDitty, where he's currently ranked No. 338 out of more than 75,000 rated members.

The Motley Fool recommends Orbital ATK. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.