The first 9-meter (29.5-foot) diameter composite propellant tank dome for SpaceX’s full-scale BFR spaceship prototype has been spotted more or less complete at the company’s temporary Port of Los Angeles facility, unambiguous evidence that SpaceX is continuing to rapidly fabricate major components of its next-generation rocket.
Speaking at a dedicated BFR update event in mid-September, CEO Elon Musk foreshadowed as much, and recent updates have reiterated just how committed SpaceX is to BFR and just how keen the company is to waste no time at all.
“We’ve built the first cylinder section…and we’ll be building the domes and the engine section soon.” – SpaceX CEO Elon Musk, September 2018
During that September 17th presentation, Musk did not parse his words despite a self-admitted tendency to look at SpaceX’s development program timelines (Falcon 9, Falcon Heavy, Dragon, BFR) through rose-tinted glasses. Just two months after he uttered the quote above, SpaceX has visibly either finished or nearly finished a 9-meter diameter BFR spaceship (BFS) tank dome.
Due to SpaceX’s opaque treatment of development programs (both literally for the tent and figuratively for official updates), it’s possible that this may even the second dome completed so far. Either way, it can be extrapolated – assuming that the layout of BFR 2017 is generally representative of BFR 2018 – that the first spaceship prototype will require two or three roughly identical tank domes. If the common-dome tank layout is basically the same (disclaimer: it might be quite different), then SpaceX may end up mounting BFS’ 7 Raptor engines almost directly to the rear of the bottom tank dome, requiring either significant structural reinforcement or a second uniquely-engineer and optimized dome.
Judging from SpaceX’s and Musk’s desire to make reusable rockets as reliable as (if not even more reliable than) commercial airliners, the safest form of mass-transit humans have created, it seems more likely than not that Raptor and BFR will continue SpaceX’s practice of quite literally surrounding each engine with thrust-transmitting structures that simultaneously act as armored shields. In the event that a Merlin engine fails on Falcon 9 or Heavy, each booster’s octaweb contains nine separate armored chambers that exist to isolate each engine in the event of a catastrophic failure. In fact, a Merlin failure – the only such in-flight failure known – during SpaceX’s CRS-1 Dragon launch in 2012 demonstrated the efficacy of this design, preventing the failure of just one of nine engines from causing total mission failure.
Rise of the ‘hexaweb’?
To replicate that design strategy on BFR (both booster and spaceship) would be an act of simple pragmatism – it’s always preferable to design for survivability and reliability than to couch launch and mission success primarily on the reliability of individual components. Because SpaceX chose not to share similarly detailed cutaways of BFR’s updated 2018 design, it’s unclear if the spaceship’s engine section (“hexaweb”, to borrow from “octaweb”) has changed dramatically.
Given the unexpected decision to move entirely away from a version of Raptor specifically optimized for vacuum operation for BFR’s first iteration, as well as the new presence of ~90 cubic meters of storage bins around the circumference of the spaceship’s aft, it’s possible that SpaceX will opt for a design more reminiscent of the Falcon family’s octaweb.
Regardless, the appearance of a completed BFS tank dome is a major development on the vehicle’s path to integrated testing and paves the way for the fabrication of additional tank domes, barrel sections, engine sections, and more. Particularly obvious and noteworthy will be the fabrication of the prototype spaceship’s pointed cone-shaped nose section, its large tripod fins/wings/legs, and its two forward canard wings.
With all three fins/wings installed, BFS – in its current iteration – would have an unbelievable circumference of ~67 meters (220 feet) and a ‘finspan’ of perhaps 21 meters (~70 feet) tip to tip. BFS is going to be a very hard spaceship to hide.