For a company that rarely reveals anything without explicit intent, a February 28th video posted by SpaceX during the lead-up to Crew Dragon’s launch debut featured a surprise cameo: two Block 5 side boosters meant to support Falcon Heavy’s commercial debut and second launch ever.
Likely a subtle nod to close observers and fans, the inclusion of Falcon Heavy is a perfect bit of foreshadowing for the next launch set to occur from Pad 39A after Crew Dragon’s flawless orbital debut. As of now, Falcon Heavy Flight 2 is settling in on a potential launch as early as the first week of April, although delays during the rocket’s critical preflight processing and static fire test are about as likely as they were during the vehicle’s inaugural mission. If the rocket’s first launch and booster recoveries are fully successful, both side boosters (and perhaps the center core) could fly for a second time as few as two months later in June 2019.
A number of photos taken by Instagram users visiting Kennedy Space Center appear to indicate that SpaceX has more or less completed the reconfiguration of Pad 39A’s transporter/erector (T/E), modifying the base with additional hold-down clamps to account for three Falcon boosters instead of the usual one. Ten days after the successful launch of Falcon 9 B1051 in support of Crew Dragon’s first mission to orbit, it’s likely that additional work remains to ensure that 39A is fully refurbished and reconfigured for Falcon Heavy.
For the heavy-lift rocket’s commercial debut and second flight ever, SpaceX is likely to be exceptionally cautious and methodical in their preflight preparations. This is especially necessary due to the fact that Falcon Heavy Flight 2 differs dramatically from Falcon Heavy’s demo configuration, degrading the applicability of some aspects of the data gathered during the rocket’s largely successful test flight.
Most notably, all three first stage boosters will be Block 5 variants on their first flights, whereas Flight 1’s first stage featured two flight-proven Block 2 boosters (B1023 and B1025) and one new Block 3 booster (B1033). Additionally, the center core – B1033 – was lost during a landing anomaly that prevented the booster from reigniting its engine for a landing burn, cutting off another valuable source of data that would have served to better inform engineers on the performance of Falcon Heavy’s complex and previously unproven mechanical stage separation mechanisms.
Falcon 9 Block 5 is a fairly radical departure from the Block 2 and 3 variants SpaceX based Falcon Heavy’s initial design on. It’s possible that the rocket’s engineers were able to at least set up that design and manufacturing work on a safe path to forward compatibility, but it’s equally possible that so much work was focused on simply getting the vehicle past its launch debut that compatibility with Falcon 9 Block 4 and 5 was pushed well into the periphery. Considering the fact that it has now been more than a year since Falcon Heavy’s February 6th, 2018 debut, the latter eventuality offers a much better fit. Nevertheless, with a solid 13-14 additional months of redesign and testing complete, it seems that SpaceX is keen to get its super heavy-lift launch vehicle back on the horse, so to speak.
The specific changes made in Falcon 9 Block 4 is unclear aside from a general improvement in Merlin 1D and MVac performance, as well as significant upgrades to Falcon 9’s upper stage, likely focused on US military and NASA requirements for long-coast capabilities on unique mission profiles. Most significantly, Falcon 9 Block 5 transitioned the SpaceX rocket to a radically different primary thrust structure (also known as the octaweb), replacing welded assemblies with bolted assemblies wherever possible. This simultaneously allows for easier repairs and modifications, improves ease of manufacture, and increases the structure’s overall strength, a critical benefit for Falcon Heavy’s heavily-stressed center core. Meanwhile, Falcon 9 Block 5 moved from Full Thrust’s (Block 3/4) maximum 6800 kN (1,530,000 lbf) of thrust to more than 7600 kN (1,710,000 lbf), an increase of roughly 12%. Combined with Block 5’s focus on extreme reusability, SpaceX engineers and technicians likely had to do a huge amount of work to leap from Falcon Heavy Flight 1 to Flight 2.
Aside from the presence of both Falcon Heavy side boosters, both of which were spotted arriving in Florida by local observers, the first Block 5 Falcon Heavy center core also very likely arrived within the last few months, followed rapidly by can be assumed to be the mission’s fairing and Falcon upper stage. Falcon Heavy’s commercial debut will see the rocket attempt to place communications satellite Arabsat 6A – weighing around 6000 kg (13,200 lb) – into a high-energy geostationary orbit, either direct-to-GEO or a transfer (GTO) variety.
If all goes according to plan, SpaceX will attempt to turn around Falcon Heavy’s Block 5 side boosters (B1052 and B1053) for Falcon Heavy’s third launch – the USAF’s STP-2 mission – as few as 60-80 days later, June 2019. According to NASASpaceflight, STP-2 will fly with a new center core (presumed to be B1057) instead of reusing Arabsat 6A’s well-cooked B1055 booster.
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