A duo of rocket spottings on November 9th and 10th confirm that SpaceX’s next Falcon Heavy rocket – an amalgamation of three Falcon 9 boosters, an upper stage, and extensive modifications – is already in the late stages of manufacturing and is nearing the beginning of integrated structural and static fire testing.

As of now, this Falcon Heavy side booster could end up supporting either or both of two near-term launch contracts in place for the rocket, communications satellite Arabsat 6A or the US Air Force’s second Space Test Program (STP-2) launch

SpaceX's second Falcon Heavy is slowly but surely coming together 😀 https://t.co/AYJsQ8Mld5

— Eric Ralph (@13ericralph31) November 13, 2018

The question of the hour – at least for Falcon Heavy – is which of those two available payloads will be atop the rocket on its first truly commercial launch. While suboptimal, a few general characteristics of each payload, SpaceX’s history of commercial launches, and Falcon Heavy itself can offer a hint or two.

Triple the rocket, triple the trouble

Thanks in large part to the fact that the first integrated Falcon Heavy was composed of two relatively old Falcon 9 booster variants and a center core that was quite literally a one-off rocket, the process of reenginering and building another Falcon Heavy rocket off of the family’s newest Block 5 variant has likely been far harder than simply building another Falcon Heavy. Although all three original Falcon Heavy boosters (B1023, B1025, and B1033) were in the same league as Block 5, their Block 2 and Block 3 hardware was designed for approximately 10% less thrust and are almost entirely different vehicles from the perspective of structures and avionics.

Perhaps even more importantly, it’s unknown whether Falcon Heavy Block 1 (for lack of a better descriptor) was designed with serious reusability in mind, at least in the same sense as Falcon 9 Block 5 was. For instance, a major portion of the rocket’s extreme complexity and difficulties lies in the basic need to transmit three times as much thrust through the center core. To do that and do it without rocket-powered separation mechanisms, SpaceX had to develop structural attachments and connections capable of surviving unbelievable mechanical and thermal stresses for minutes on end.

Clearly, this was an unfathomably difficult problem to solve in such a manner that Falcon Heavy would work at all the first time. Factor in the strategic need for those same components to survive repeated cycles of those stresses with minimal refurbishment in between and the problem at hand likely becomes a magnitude more difficult, at least. In large part, this helps to explain why there will end up being a minimum of 11-12 months between Falcon Heavy’s first and second launches.

Arabsat or STP?

Over the course of SpaceX’s last 2-3 years of commercial launch activity, the company and its customers have demonstrated time and time again a reliable pattern: commercial customers (in the sense of private entities) are far more willing to take risks with new technologies than SpaceX’s government customers. NASA’s Commercial Resupply Services is the exception for the latter group but also has no Falcon Heavy launch contracts. For Falcon Heavy, there are thus main three options at hand.

1. Arabsat 6A launches first with 1-2 flight-proven boosters; the Air Force’s STP-2 mission flies on an all-new Falcon Heavy 4-6 months later.
2. SpaceX builds entirely new Falcon Heavy rockets for both customers, requiring four new side boosters and two new center cores.
3. STP-2 launches first on an all-new Falcon Heavy; Arabsat 6A launches second on the first flight-proven Falcon Heavy after 6+ months of additional delays.

Arabsat is far more likely to accept – for a significant discount – a ride aboard the first flight-proven Falcon Heavy, especially if it means preventing more major launch delays. If the Falcon Heavy side booster spotted eastbound last week is a refurbished Block 5 booster rather than a new rocket, than option 1 is the easy choice for most probable outcome. The real pack leader for Falcon Heavy Flight 2, however, will be the completion of a new Block 5 center core and its shipment to Texas for structural and static fire testing.

Time will tell. For now, a completed Falcon Heavy side booster is the best sign yet that SpaceX may manage the rocket’s second launch in the first quarter of 2019, whichever launch that may be.