New look BFS from SpaceX

SpaceX has announced its first paying passenger for a circumlunar flight.  Well, not quite the first.  There had been plans to do it with the Dragon capsule, but this was cancelled when SpaceX switched to the BFR/BFS as its workhorse rocket.  The flight in a BFS will certainly be much more comfortable than it would have been in the Crew Dragon.

In a recent address to graduate students in Madrid, Gwynne Shotwell, SpaceX's CEO mentioned that the first "hopper" tests of the BFS had slipped from early 2019 towards the end of the year, so the moon trip won't be happening until 2020.  (A reminder of the current Mars timetable:  two cargo vessels for the December 8th 2022 opposition, 2 crewed vessels and two cargo vessels for the January 16th 2025 opposition.  Since oppositions occur only every 2 years, you wouldn't want to miss one.)

When asked about space tourism as a source of revenue for SpaceX she replied   “[Space] tourism is inevitable but [SpaceX] doesn’t want to do it too soon”, the goal is to launch “test pilots before families”, but then added that an announcement was expected soon.

For us SpaceX tragics, however, it's the strong hint of design changes which is much more interesting.

BFS circumnavigating the moon.  Source: SpaceX

Nearly overshadowing SpaceX’s intriguing lunar tourism contract, the photo included with official announcement features a BFR spaceship (BFS for short) that has rather dramatically departed from SpaceX renders of BFR and BFS dating back to late 2017 and early 2018. Most notably, the spaceship’s delta wing has been removed in its entirety, replaced by a triangular layout of three fins and what appear to be forward canards (control surfaces most commonly used to improve aerodynamic stability). Those apparent canards could also potentially act as a sort of stand in to the grid fins present on both BFR and Falcon boosters.

This new render also implies a logical relocation of the ship’s landing legs from external pods to the tips of its new wings, and may even betray some sort of hinge mechanism on the bottom two wings, perhaps meant to allow BFS to safely land on its trio of wingtips while still preserving the inherent aerodynamic stability of BFR 2017’s delta-wing.

Finally, the most significant change is found at the spaceship’s rear, where a new configuration of seven Raptor engines – by all appearances the version of the engine optimized for sea level performance – is surrounded by a mysterious ring of white or grey panels, perhaps a form of heat-shielding or maybe something else entirely. The lack of vacuum-optimized Raptors is arguably the most surprising feature of this unexpected announcement, either pointing to some sort of brash ‘artistic license’ (less likely given Musk’s tweet response) or a drastic departure from traditional rocket design, doing away with expanded vacuum nozzles for some more exotic solution.

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Musk was pretty dismissive about wings/fins in his earliest comments on interplanetary space vehicles, because, he argued, many places we want to visit don't have atmospheres, and so wings would be useless.  On the other hand, Earth and Mars do have atmospheres, and atmospheres also make landing more complicated, so some sort of aerodynamic controls in addition to cold-gas thrusters would be helpful.  In fact, this is what the grid-fins used on the Falcon 9 do.  They would be useless on the moon but are essential on Earth.  Since there will be one basic design of the workhorse BFS with just limited changes between the crewed, fuel and cargo versions, it seems sensible to include fins, even if they can't be used on the moon.  It shows just how driven by facts Musk is that despite his initial opposition he has changed his mind.

In his second presentation about the BFR, at the 2017 International Aeronautical Congress in Adelaide, Musk said that a moon landing would require the BFS to be refuelled in orbit.  However, if the ship doesn't actually land on the moon, and has a small payload (one person!) perhaps it can do it from Earth.  The first stage will deliver it to high elliptical orbit orbit and then it will fly to the moon, orbit the moon, and return to earth using its own fuel.  Or maybe, SpaceX intends to refuel it in orbit, which would require constructing one first stage and two second stages, the BFS and its tanker version of the BFS (the BFT?)

People consistently underestimate Musk.  He tends to achieve what he sets out to do--even if it's later than he initially said.  When Shotwell assures us that “something terrible [would] have to happen at SpaceX for us to not be on our way to Mars and back in 10 years,” I believe her.  But that could still mean slippage from the 2022/25 timetable to the 2025/2027 timetable.  SpaceX has lots of experience with the booster (first stage) of  the BFR.  The difficult part will be building the BFS, and making it safe for humans.  

Updated BFS design.  Source: Teslarati