SpaceX conducts Falcon 9 test; AMOS-6 investigation narrows
As SpaceX narrows on a second stage COPV (Composite Overwrapped Pressure Vessel) as the cause of the AMOS-6 static fire pad failure on 1 September, the company is pressing ahead with hot fire operations on a new first stages at its McGregor, Texas, facility. The new booster is set to power what SpaceX hopes will be a December mission from the soon-to-be-christened LC-39A at the Kennedy Space Center in Florida.
McGregor preps core stages for upcoming missions:
While SpaceX continues to work its investigation of the AMOS-6 static fire pad failure, the company has made sufficient progress on its fault tree and resolution toward Return To Flight (RTF) to begin the next critical phase for the upcoming missions to follow the AMOS-6 mishap.
Currently, a Falcon 9 first stage is understood to be patiently waiting at Vandenberg Air Force Base in California. It is believed this Falcon 9 will launch the first mission since the AMOS-6 incident on a December launch that may involve the Iridium NEXT flight.
Meanwhile, a new first stage was spotted at McGregor, erected on the test stand. A hot fire of the nine core stage Merlin 1D engines was conducted on Tuesday, although SpaceX is yet to confirm the event.
It is possible – although not confirmed – this booster will be involved with the first launch from SpaceX’s Pad 39A at the Kennedy Space Center (KSC).
A placeholder date of December 17 was cited on planning Cape documentation over a week ago. The mission was cited as for Echostar-23, although – as expected – SpaceX is yet to provide specifics to its upcoming manifest until after the AMOS-6 investigation has concluded.
Also at McGregor, though currently in storage, is another first stage. It is possible this stage may be used for the CRS-10 Dragon launch, also from 39A.
At present, it is understood that Pad-39A’s final conversion is the primary driving factor toward Echostar-23’s launch, aside from official wrap-up and clearance of the AMOS-6 investigation.
Should a NET 17 December launch date hold, the Echostar-23 mission would lift off from pad 39A at 23:30 EST – the first launch from the pad since 8 July 2011 when Atlantis closed out the Shuttle program.
Following Echostar-23, SpaceX will then prepare Pad-39A for the CRS-10 mission to the International Space Station in January 2017.
SLC-40, which was damaged in the AMOS-6 explosion, isn’t expected to be back in action until at least the second quarter of 2017.
AMOS-6 investigations replicates failure:
As core stage preparations at McGregor heat up, SpaceX is closing in on the failure mechanism and mode for the 1 September static fire failure of the Falcon 9 that was supposed to launch the AMOS-6 satellite to orbit.
According to a company statement on 28 October, “The Accident Investigation Team continues to make progress in examining the anomaly on September 1 that led to the loss of a Falcon 9 and its payload at Launch Complex 40 (LC-40), Cape Canaveral Air Force Station, Florida.
“Since the incident, investigators from SpaceX, the FAA, NASA, the US Air Force and industry experts have been working methodically through an extensive fault tree to investigate all plausible causes. As part of this, we have conducted tests at our facility in McGregor, Texas, attempting to replicate as closely as possible the conditions that may have led to the mishap.”
What is now confirmed is that the investigation teams have made “significant progress” in eliminating and narrowing elements of the fault tree – with the team now focused on a breach of the cryogenic helium system on the second stage liquid oxygen (LOX) tank.
“The root cause of the breach has not yet been confirmed, but attention has continued to narrow to one of the three COPVs inside the LOX tank.”
A COPV is a lightweight tank that consists of a thin, non-structural liner (that acts as a barrier between the fluid inside the tank and the composite to prevent leaks) that’s wrapped with a structural fiber composite.
Usually, a protective shell is also applied to protect the COPV against impact damage.
Failure of a second stage COPV on the AMOS-6 Falcon 9, while devastating, nonetheless provided another reminder to the dangers COPVs carry over their lightweight benefits.
COPV dangers to spaceflight are well-known not just to the unmanned launch vehicle families but also to the human-carrying Space Shuttle fleet.
Following the loss of Shuttle Columbia, two COPVs aboard Orbiter Atlantis were found to be at “high risk” of a rupture/bust failure.
New procedures were subsequently implemented throughout the Shuttle program to mitigate the risk of a COPV burst failure – which was identified as a possible COPV failure mechanism without a precipitating leak of the vessel.
The two high-risk COPVs on Atlantis were eventually replaced, and Discovery and Endeavour flew out their COPV sets through an overall end of program risk of a 1 in 489 chance of a COPV failure resulting in a Loss Of Vehicle (LOV) or Loss Of Crew and Vehicle (LOCV) event.
Importantly for SpaceX, “Through extensive testing in Texas, SpaceX has shown that it can re-create a COPV failure entirely through helium loading conditions. These conditions are mainly affected by the temperature and pressure of the helium being loaded.”
Recreation of the failure was deemed essential for SpaceX in determining the root cause of the AMOS-6 failure – an element that was complicated by a lack of data due to the short timeline of the failure event at only 93 milliseconds from first signs of an anomaly to loss of data.
With the failure now replicated, “SpaceX’s efforts are now focused on two areas – finding the exact root cause, and developing improved helium loading conditions that allow SpaceX to reliably load Falcon 9.”
As always, the final results of the investigation and the exact improvement plan for helium loading will drive the eventual RTF launch for SpaceX.
If the company does meet its internal goal of launching the Iridium mission from Vandenberg in December, the RTF will mark an impressive turnaround from failure to recovery and will be one of the quickest RTFs in modern rocketry history – beating SpaceX’s already impressive 6-month recovery effort from the CRS-7 failure in late June 2015 to RTF on the Orbcomm 2 mission in December of that same year.
However, even if SpaceX is not ready for RTF until January 2017, both of the company’s pads at Vandenberg and the Kennedy Space Center are expected to be ready to support what will be a busy salvo of missions as the company catches up on its manifest obligations.
(Images: SpaceX, USLaunchReport, NASA and L2 – including NSF L2 member Gary Blair (McGregor Testing) Amos-6 Failure Evaluation video by Jay Deshetler and photo by NSF member Bennett – (http://scarborough.photoshelter.com/))