On Monday, September 17th, SpaceX CEO, Elon Musk, provided an update on the company’s massive Big Falcon Rocket (BFR) and Big Falcon Ship (BFS – previously referred to simply as “the ship” or “the spaceship”), and revealed the first fare-paying passenger who will supposedly fly around the Moon aboard a BFS some time in the 2020s.
BFR has been in development since 2012/13. Designed to be fully reusable, it was initially referred to as the Mars Colonial Transport (MCT) – reflecting the company’s intention to use it to send humans to Mars. In 2016, SpaceX revealed the first formal design for the vehicle, which had been renamed the Interplanetary Transport System (ITS) to reflect the fact it could fulfil a number of roles. At that time, the vehicle – comprising a first stage booster and upper stage spaceship – was to be a 12 metre (39 ft) diameter, 122 m (400 ft) tall monster. By 2017, it had been renamed the BFR (for “Big Falcon Rocket”), and redesigned to be 9 m (29.5 ft) in diameter and 106 m (347 ft) tall.
With the 2018 presentation, Musk revealed further design changes to the system, most notably with the upper stage spaceship, the BFS, some of which give it very retro rocket ship look.
|Left: The evolution of the BFR from 2016 (as the ITS) to 2018; renderings via the Everyday Astronaut. Right: an animated comparison between the 2017 BFS and the 3-finned 2018 variant (from an idea by Overlook Horizon).|
In particular, the BFS now sports three large fins at its rear end. All three are intended to be landing legs – the BFS being designed to land vertically – with two of them actuated to move up and down as flight control surfaces during atmospheric decent. These are matched by two forward actuated canards, also designed to provide aerodynamic control during a descent through an atmosphere.
Two less obvious changes are an increase forward payload section and the design of the nose area of the vehicle, which includes a much larger forward “canopy” design than previous iterations, and an update to the BFS’s motors. Originally designed to be powered by 7 of the new SpaceX Raptor engine optimised for vacuum operations, the BFS will now initially be powered by seven of the same Raptor motors that will be used on the vehicle’s first stage (which uses a total of 31), optimised for thrust in an atmosphere.
Elements of the first BFR system have been under construction for the last 12-18 months. These include one of the fuel tanks, and the initial hull rings, and Musk claims that the company hope to have the first BFS prototype ready for initial “hopper flights” – lifting itself off the ground under thrust and then landing again – by the end of 2019. SpaceX then plan to run high altitude testing of BFS in 2020, together with initial flights of the core stage as well.
Overall, the goal is to have the first BFR / BFS combination ready for orbital flight tests in 2021, building towards the flight around the Moon, which the company has earmarked for 2023.
This is an incredibly ambitious time frame, and SpaceX would appear to have some significant engineering challenges to overcome. For example, by combining the landing legs with control surfaces, how are they going to ensure the craft can land sufficiently gently on another surface without damaging the mechanisms designed to move the fins, which will be required when the vehicle returns to earth.
While there was always a risk that landing struts (as were originally going to be used with BFS) might suffer damage as a result of a “hard” landing on the Moon or Mars, integrating landing systems into surfaces vital to the vehicle’s (and a crew’s) safe return to Earth as planned by SpaceX, would appear to add further complexity to the vehicle – or call for contingencies to be able to transfer a returning crew to another vehicle on their return to Earth orbit should one of systems use to actuate the fins suffer damage when landing on the Moon or Mars.
Another of the questions from where is BFR is likely to be launched. When initially revealed with a 12-metre diameter, it required a purpose-built launch facility. But with the core now reduced to a 9 metre diameter, BFR could in theory be launched from the SpaceX facilities at Launch Complex 39A, Kennedy Space Centre (KSC), Florida.
In discussing plans, Musk revealed a final decision on BFR launch facilities has yet to be made, and hinted it might even initially fly from a floating platform. This was an idea first put forward in one of the company’s promotional videos for the system, suggesting it could fly up to 100 people between New York City harbour and Shanghai harbour in 40 minutes. This, simply put, will not happen – because the idea doesn’t work either economically or practically.