In what is anticipated to be the first of many such occasions, SpaceX has conducted the all-important static fire on Monday of the first stage of the Falcon 9 rocket that will be tasked with lofting the SES-10 mission to orbit next week. Of historic importance is the fact that this first stage has already launched a mission – marking the first time that SpaceX will refly the first stage of a Falcon 9 rocket.
Static fire – the road to launch No Earlier Than 29 March:
The static fire process for SpaceX and its Falcon 9 rocket is one of the last critical components in the pre-launch flow ahead of liftoff.
For SES-10, the Falcon 9 and mated second stage moved to the launch pad on top of the TEL (Transporter Erector Launcher) and taken to vertical at historic launch complex 39A.
Once the Falcon 9 was vertical, technicians and engineers completed all of the connections between the TEL/launch mount and LC-39A and proceeded into countdown operations on Monday morning.
For this particular static fire, SpaceX had a six-hour window.
KSC security personnel established roadblocks on the main roads leading to LC-39A and KSC Emergency Operations Command (EOC) were activated and on stand ready to assist in the “extreme, unlikely event of an anomaly”, notes an SES-10 Mission Update package available on L2.
Once into countdown operations, the Falcon 9 was filled with its RP1 and LOX fuel and oxidizer and run through the same series of steps as it will encounter in its actual countdown.
The nine Merlin 1D engines at the base of the Falcon 9 first stage – Core #1021 – then ignited for a multi-second firing sequence.
Usually, Falcon 9 static fires result in a 3.5 second engine firing – taking the vehicle right up to the nominal T0 point in the count – at which point all 9 engines are shut down and the vehicle is secured.
However, the static fire for SES-10 might be slightly longer – in the 5-second range – as was seen with the previous SES mission, SES-9, launched by a Falcon 9 rocket last year. Visuals of the firing suggested the test did last for five seconds.
Regardless of the duration of the planned static fire, the event provided SpaceX with valuable data and a wet dress rehearsal for the actual launch – which is now slated for Thursday, 30 March in a window extending from 1800 to 2030 EDT.
The SES-10 mission had, earlier this month, been slated for No Earlier Than (NET) 27 March – with a static fire NET now as 24 March. However, a tight schedule has slipped the mission twice ahead of the Static Fire.
LC-39A held up extremely well from the Echostar XXIII launch and would have been able to support a 27 March launch. However, the first impact was due to ongoing delays with an Atlas V rocket from United Launch Alliance which is slated to launch the OA7 Cygnus mission for Orbital ATK.
When ULA noted that they needed additional time to fix a Ground Support Equipment (GSE) issue, SpaceX agreed to delay the SES-10 launch by two days to allow ULA the 27 March date for a mission to launch supplies to the International Space Station.
When ULA subsequently announced that the Atlas V mission was being delayed indefinitely to fix a new hydraulic issue, this time with the Atlas V booster, SpaceX opted not to pull the launch of SES-10 back to 27 March and instead hold the 29 March date after all of their schedules and workflows for personnel, the rocket, and the ASDS (Autonomous Spaceport Drone Ship) Of Course I Still Love You (OCISLY) barge had been realigned accordingly.
A tight schedule resulted in the Static Fire and launch date slipping one additional day respectively.
Making history – Reusing a Falcon 9 core stage for the first time:
The history of Core #1021 stretches back far, in terms of what has to date been normal with Falcon 9 launches.
For the first time in its storied history, Core 1021 fired up for its first hot fire test at SpaceX’s McGregor, Texas, test facility on 5 February 2016.
Following the full duration hot fire, the core suffered an incident on 8 February during follow-up testing when a GSE-related incident damaged most of the stage’s engine nozzles.
The damage was repaired at McGregor, and the stage was shipped to Cape Canaveral by the end of March 2016.
After its arrival at SLC-40, Core 1021 was transported into the Horizontal Integration Facility (HIF) and prepared for mating with its second stage and CRS-8 Dragon payload.
On 5 April, the core’s nine engines lit for the 3.5 second static fire on SLC-40.
Three days later, the engines once again roared to life as Core 1021 launched with the CRS-8 mission to the ISS.
After 2 minutes 42 seconds of flight, the engines shut down, and Core 1021 separated from the second stage – which continued to sail into orbit.
After separation, Core 1021 performed a Boostback Burn to set up its reentry into the atmosphere and place it onto the proper course for landing on the ASDS OCISLY barge.
This was followed by an automated Entry Burn and then a single-engine landing burn.
With a live view from a chase plane, Core 1021 eased onto OCISLY 8 minutes 35 seconds after liftoff while the 2nd stage continued to power the CRS-8 Dragon to orbit.
Landing on OCISLY marked the first successful drone ship landing of a Falcon 9 core and the second overall successful core stage landing for the company.
Interestingly enough, Core 1021 could have performed a Return To Launch Site landing at LZ-1 – like the ORBCOMM-2 core had in December 2015; however, SpaceX opted to land Core 1021 on the ASDS barge instead to prove beyond doubt that barge landings and recoveries were possible.
After securing Core 1021 on the barge, the duo set sail back for Port Canaveral.
Once in Port, the core was removed from OCISLY and engineers removed its landing legs before the whole core was rotated horizontal and loaded onto a transport trailer – where it was then taken from Port Canaveral to the HIF at LC-39A.
At the HIF, months of inspections, engine removals, and studies commenced.
Originally, Core 1021 was destined for multiple hot fires as part of SpaceX’s concerted effort to learn as much as possible from a returned core before committing any core to reflight.
The originally announced plan called for Core 1021 to undergo 10 firings over the course of several months.
At this same time, it was not known with certainty where Core 1021 would undergo these 10 test firings – with some hopes being that those firings could occur at LC-39A with McGregor as a backup.
However, as more and more cores hit their landing marks and were recovered, it was decided that Core 1021 was not the best choice for the 10 post-flight firings.
That job went to Core 1022 that launched the JCSAT-14 mission and performed a successful reentry and landing at its maximum operational and heating limits – so much so that SpaceX didn’t really expect Core 1022 to successfully reenter and land, thus making it a perfect battled-hardened test article.
Post-flight inspections of the JCSAT-14 core immediately ruled out its ability to fly again, but as Elon Musk noted, the core became the “life leader for ground tests to confirm others are good.”
After initial evaluations inside the LC-39A HIF, Core 1022 was wrapped up and transported to McGregor.
In July, it was hoisted onto the Falcon 9 test stand and topped with a special cap to provide simulated weight for a second stage to aid in the data acquisition process.
Notably, Core 1022 was not the first core to see a second life – as the ORBCOMM-2 core was previously static fired on SLC-40 on 14 January 2016 to provide an initial set of data points on a previously-flown core.
On 28 July 2016, Core 1022 came back to life, conducting a 2 minute 30 second full duration hot fire test.
This was followed by two more full duration hot fires over the next two days.
After being removed from the test stand to make room for another core, Core 1022 was then returned to the stand and fired up several more times.
All of these tests on an already flown, maximally stressed F9 core provided crucial data for SpaceX on the health of returned F9 cores, how their systems responded to multiple firings and cryo tanking cycles, and gave a good baseline for the number of times each system can potentially be reused.
Importantly, it proved – through data – that the stages could be reflown.
However, even before Core 1022 was put through its paces at McGregor, SpaceX announced on 16 July 2016 its intentions to use the CRS-8 Core, #1021, for the first Falcon 9 reflight – though no specific mission was formally announced.
In August 2016, the SES corporation confirmed that their SES-10 mission would be the first one to use an already flown Falcon 9 core.
At this point, SES-10 was scheduled for a “contractual window between mid-October and mid-November 2016.”
Just days after this announcement, the AMOS-6 static fire ended with a conflagration event and the destruction of that Falcon 9 and the AMOS-6 satellite and resulted in significant damage to SLC-40.
With the Falcon 9 grounded as an investigation took place, SES-10’s place in the manifest shuffled as the Falcon 9 launch order was redesigned.
By January 2017, just after a successful Falcon 9 Return To Flight mission from Vandenberg Air Force Base, California, Core 1021 was at Mcgregor and installed on the Falcon 9 test stand.
The core was loaded with propellant, and its nine Merlin 1D engines were fired for a full duration hot fire test – as part of a standard pre-launch flow.
The core was then transported back to the Kennedy Space Center and moved into the HIF for final flight processing.
Despite the passage of nearly one year between flights, Core 1021 was refurbished in just four months, as Gwynne Shotwell stated earlier this month.
Looking ahead to launch, SpaceX will attempt to recover the Core 1021 at sea with OCISLY.
If SpaceX can successfully recover Core 1021 again, it will not only be an historic achievement, but will provide even more data on how Falcon 9 core stages fare during reflight events.
(Images: SpaceX; ULA)