A major question for SpaceX’s end of year manifest appears to be gaining some answers as the company aims to debut its Falcon Heavy rocket in the late-December time period. The schedule for Falcon Heavy has been a fluid campaign as operations to bring SLC-40 back into operation took major priority this year following the activation and historically high use of LC-39A to ramp up and maintain SpaceX’s impressive launch cadence.
Falcon Heavy – a late-December debut:
This year alone has already seen 12 launches from the SpaceX-leased pad, with two more – Zuma and Falcon Heavy – planned before year end.
Currently, all three cores for Falcon Heavy’s first stage are inside the Horizontal Integration Facility (HIF) outside the perimeter of LC-39A at the Kennedy Space Center, as is the second stage.
Also present in the HIF is the brand new core that will launch the Zuma mission for Northrop Grumman on NET 15 November 2017 in the launch window that extends from 20:00-22:00 EST (01:00-03:00 UTC on 16 November).
Once Zuma is off the ground, Falcon 9 single stick launches will largely move back to SLC-40 starting with the CRS-13 Dragon launch to the International Space Station, set for No Earlier Than (NET) 4 December.
That move will free Pad-A for the final round of work needed to finish configuring the Transporter/Erector/Launcher (TEL) for Falcon Heavy.
The main work involves the Falcon 9 east/west hold down clamps, which have to be removed as their presence overlaps with the positioning of the Falcon Heavy side-mounted cores’ engines.
Those east/west hold down clamps are currently installed on inserts to the TEL reaction frame, and once removed will create the needed exhaust holes for the side-mounted FH cores.
However, the sheer weight of the Falcon Heavy necessitates the installation of compression bridges that will help hold and distribute the weight of Falcon Heavy.
These two compression bridges will be mounted to the same points on the reaction frame of the TEL that the east/west Falcon 9 hold down clamps are currently bolted to.
Importantly, the compression bridges are not hold down clamps.
Rather, they are specially designed pedestals that a portion of the mating brackets bolting the side cores of the Falcon Heavy to the central core will rest on top of. (See image to left for visual.)
This remaining work to the TEL comes after months of working between launches and during the range-imposed downtime in July.
At the beginning of summer, a total of 60 days of work to finalize Pad-A for Falcon Heavy were needed.
Falcon Heavy verification and validation testing – last steps before launch:
Once the TEL is ready, SpaceX will undertake a series of tests – known as verification and validation – for Falcon Heavy.
The Falcon Heavy’s static fire will be the first time 27 Merlin 1D engines are lit together.
Due to thrust torque (a thrust-induced rotation) scenario that could destroy or severely damage the octawebs at the base of each Falcon core that house the Merlin 1D engines, the Falcon Heavy’s 27 engines will not be lit simultaneously like the Falcon 9 engines.
Instead, Falcon Heavy will take a page from the Space Shuttle’s book and will employ a staggered start sequence – like main engine start on Shuttle where each main engine started 120 milliseconds after the previous.
For Falcon Heavy, it is understood that two engines will be lit simultaneously followed by the next two… and so on until all 27 are up and running.
While SpaceX has ample experience lighting all nine engines of the Falcon 9 simultaneously, with every Falcon 9 going through a full duration hot fire at McGregor followed by a static fire on the launch pad before all nine engines are lit a third time for launch, no company in the U.S. rocket industry has experience lighting 27 engines at the same time.
While each of the three Falcon Heavy debut cores – two flight-proven cores for the side-mounted boosters (boosters B1023 and B1025) and a new core for the central core (booster B1033) – have undergone hot fire testing at McGregor, they were all fired separately because the Texas test site is not built to accommodate three cores at the same time.
This means SpaceX will not gain a full understanding of how all 27 engines light until the more-crucial-than-usual static fire at LC-39A at Kennedy.
When it launches, Falcon Heavy will produce 5.13 million lbf at liftoff, increasing to 5.549 million lbf as the vehicle ascends into vacuum and will become the world’s most-powerful rocket.
(Images: SpaceX, Brady Kennison for NASASpaceFlight.com, Gary Blair at McGregor, and L2 artist Nathan Koga – The full hi-res gallery of Nathan’s (SpaceX Dragon to MCT, SLS, Commercial Crew and more) L2 images can be *found here*))