SpaceX achieved a major milestone on Wednesday, firing up the 27 engines at the base of Falcon Heavy in an event that will help solidify the target launch date for the rocket’s maiden voyage – which will send Elon Musk’s Tesla Roadster on a journey to heliocentric Mars orbit. Falcon Heavy’s first ever Static Fire took place at 12:30 pm Eastern.
Several previous attempts to conduct the test during a long static fire windows had not managed to proceed towards the actual firing up on the engines.
A milestone of RP-1 and LOX being loaded into the vehicle had been achieved, with several prop loading tests taking place over the last few weeks.
Crucially for this static fire milestone, SpaceX has approached the attempts as a Wet Dress Rehearsal – everything but engine ignition – with a potential to proceed into a static fire should everything be perfect. Therefore, the tests began with propellant being pumped into all three first stage cores and the second stage without an initial intention to light the Falcon Heavy’s engines – exactly like the two Wet Dress Rehearsals performed last week at SLC-40 ahead of Zuma’s launch.
Although SpaceX has visibly conducted prop load tests, the company was yet to confirm if a full cycle WDR has been conducted. However, SpaceX never comment on such tests, with their first note likely to come after the Static Fire itself has taken place, and a quick look review of the test has been completed. This is also SpaceX’s standard approach to Falcon 9 tests.
Most of the delays for the Static Fire test have been related to the GSE (Ground Support Equipment), such as the Tail Service Masts (TSMs) and/or the hold down clamps. The large TEL has undergone a large modification to cater for the Falcon Heavy, so issues relating to the GSE is not unexpected and a clear sign as to why these tests are taking place.
An Atlas V taking priority on the Eastern Range assets and a short government shutdown have also caused minor delays.
Wednesday’s attempt followed the same approach. If, and only if, everything proceeded perfectly with fueling and the entirety of the Wet Dress Rehearsal would SpaceX then roll the test directly into a static fire, lighting all 27 engines at the base of the massive rocket while keeping it firmly clamped to the launch mount and TEL (Transporter/Erector/Launcher) at Pad 39A at the Kennedy Space Center.
On Wednesday this happened.
— Chris G – NSF (@ChrisG_NSF) January 24, 2018
Given the dynamic and new nature of Falcon Heavy’s engine start sequence and initial run, it was understood that the static fire was to last an impressive 12 seconds – much longer than the customary three to seven second duration range as has been used on flight proven booster mission (of which Falcon Heavy has two flight proven boosters) static fires and missions of national security importance.
This appeared to be the close to duration during the actual firing, although SpaceX’s official video was clearly edited.
First static fire test of Falcon Heavy complete—one step closer to first test flight! pic.twitter.com/EZF4JOT8e4
— SpaceX (@SpaceX) January 24, 2018
The Static Fire test is a culmination of a great deal of work on Falcon Heavy, not the least of which involved the configuration of LC-39A at the Kennedy Space Center to host the world’s most powerful rocket – a role the pad is well accustomed to, having hosted Saturn V and the Space Shuttle fleet (the world’s most powerful rockets at their respective times) from 1967 to 2011.
The vast majority of work to prepare LC-39A for Falcon Heavy occurred during the pad’s transition from the Shuttle era to its host role for the Falcon family. When Falcon 9 flights began off 39A in February 2017, SpaceX stated that 60 days worth of work remained – primarily with the TEL, electrical lines, plumbing and sound suppression water system – to finalize the pad for Falcon Heavy.
The original plan at the beginning of 2017 was to save all that work until SLC-40’s reactivation in August. As that pad’s rebuild took longer than anticipated, SpaceX found an ability to perform almost all of the 60 days worth of work between Falcon 9 missions – aided greatly by a one month stand down in launch operations due to planned range maintenance by the 45th Space Wing in July.
By October, SpaceX had impressively shaved all work down to just 21 days. By mid-November, they had reduced that to just 14 days, with all remaining work not possible until the clandestine Zuma satellite launched in mid-November and launch operations transferred to SLC-40 in early December.
The final 14 days worth of work could not proceed until all missions off 39A were complete because two of Falcon 9’s four hold down clamps had to be cut out from the TEL’s reaction frame – an operation that would eliminate the ability to launch single stick Falcon 9 missions from the pad in preparation for Falcon Heavy’s debut.
During its construction, Pad-A’s TEL was specifically designed to service both Falcon 9 and Falcon Heavy rockets – a configuration that required the east-west aligned hold down clamps of the Falcon 9 to be removable. The single stick Falcon 9 is held onto the launch pad by four hold down clamps – which on Pad-A are aligned to the cardinal directions: north, south, east, and west.
The east/west Falcon 9 hold down clamps have to be removed for Falcon Heavy as their presence overlaps with the Heavy’s side-mounted cores’ engines. Thus, those east/west hold downs are installed on removable inserts to the TEL’s reaction frame. Once removed, the needed space and exhaust holes for the side-mounted Falcon Heavy cores are present.
It is understood that when the east-west hold down inserts were initially constructed on the TEL reaction frame, they were not removable – thus they had to be physically cut away from the reaction frame in preparation for Falcon Heavy.
Now that they have been cut away, the removable inserts are designed to be reinstalled with relative ease, making Pad 39A easily configurable between Falcon 9 and Falcon Heavy – which will be highly important as Pad-A will serve as the launch pad for commercial crew operations later this year as well as host various single stick Falcon 9 missions to aid SpaceX’s busy 2018 manifest, which includes up to 30 missions.
For Falcon Heavy preps, once those east-west hold down inserts were removed, SpaceX needed to install two compression bridges at the base of the TEL’s reaction frame to help hold and distribute the Falcon Heavy’s weight. These two compression bridges were mounted to the same points on the reaction frame that the east/west hold down clamps had been bolted to.
The compression bridges are not hold down clamps but rather 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 below for visual.)
With all prep work completed, the TEL was rolled into the Horizontal Integration Facility (HIF) where the inaugural Falcon Heavy was mated to it. The TEL with Falcon Heavy then made the trip up the ramp to Pad 39A’s launch mount on 28 December 2017 for fit checks and electrical/data connection verification and validation ahead of the vehicle’s return to the HIF.
Now firmly back atop LC-39A, Falcon Heavy was prepared for its Wet Dress Rehearsal and static fire – a series of steps that will take Falcon Heavy through an entire launch countdown up to and including ignition of all 27 Merlin 1D engines at the base of the rocket.
The now-completed test will provide data not just on the ignition of all 27 engines but also verify and validate all of the electrical and data connections to the rocket, the pad’s ground support equipment systems, and cryogenic systems and propellant loading operations – which will mark the first time that three Falcon 9 cores and the second stage are fueled simultaneously.
With the Static Fire now complete – the first time 27 Merlin 1D engines have been lit together – reviews will continue to take place. To help the rocket during the testing, – 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 were not lit simultaneously like the Falcon 9 engines.
Instead, Falcon Heavy takes a page from the Space Shuttle’s book and employs a staggered start sequence – like main engine start on Shuttle where each main engine started 120 milliseconds after the previous – as seen in the slow motion engineering video below.
For Falcon Heavy, it is understood that two engines were lit simultaneously followed by the next two… and so on until all 27 were up and running. The timing of this ignition sequence was such that it looked simultaneous to the naked eye.
With the static fire is complete, teams reviewed the data collected during the test and to determine whether a second static fire is necessary before proceeding into the launch campaign.
Falcon Heavy hold-down firing this morning was good. Generated quite a thunderhead of steam. Launching in a week or so. pic.twitter.com/npaqatbNir
— Elon Musk (@elonmusk) January 24, 2018
Based on the official tweets that followed the test, Falcon Heavy is now into a launch flow and will target the first or second week of February for its maiden voyage.