Mass Value Report for May 2024

Starship prepares for another test flight, while Elon Musk is worries about Starship reuse and competition may be on the horizon.

In just a few days, Starship test flight IFT-4 will hopefully launch. The vehicle is stacked and SpaceX recently conducted a wet dress rehearsal. Liftoff is set for 5th June.

Credit: SpaceX

The main objective of this flight is for the ship to survive reentry - on IFT-3 a loss of attitude control caused the ship to burn up high in the atmosphere. A secondary objective is to have the booster perform a soft landing in the ocean, which failed last time due to several of the engines shutting down early during the boostback burn due to a blockage and then not relighting, causing the booster to crash.

The ascent of IFT-3 was flawless, arguably making Starship already a proven expendable booster. But as was made clear by Elon Musk at a recent presentation, if used in such a capacity it would only have a payload to LEO of around 50 tonnes. It wasn’t stated if this was due to excess dry mass, engine performance not being there yet, or the dynamics of the particular test flight - but whatever the reason, Starship still needs to prove itself in the target payload capacity of 100+ tonnes.

Before getting deep into the Starship program and its competitors, first lets look at how its sister rocket is getting on.

Falcon Cadence

In an an event with the NASA Administrator Bill Nelson earlier this year, SpaceX COO Gwynne Shotwell announced the updated target of 148 flights this year. The 13 flights in May, building on 12 flights in April, puts the central projection for yearly flights at 143, but 148 is well within the margin of error.

In the same interview, Nelson mentioned a target of 200 launches 2025. This would only be a 35% increase on this year if 148 flights is achieved, compared to a rate of 43% over the last few years. To continue 43% growth, there would need to be 212 flights in 2025 and over 300 in 2026.

It could be that 200 is the cadence limit of Falcon 9 - the weather scrubs of January already indicate some scaling difficulties, as does the rate of manufacture of upper stages. But it being a round number doesn’t necessarily make it the case. SpaceX are manufacturing a new droneship, and a fit of the logistic curve, which would assume a smooth rather than abrupt end to growth, suggests 300 launches per year is closer to the mark, meaning almost 5000 tonnes per year at current average payload masses.

To put this into perspective, during the peak of the Apollo program NASA launched 5 Saturn V rockets between December 1968 and November 1969. Their nominal LEO payload together was 700 metric tonnes - although using mass value is better for comparing a Moon rocket to a LEO launch vehicle which bumps the 5 Saturn Vs up to approximately 1000 metric tonnes equivalent. Falcon 9 has already beat that by a factor of 3, and may end up beating it by a factor of 5.

Regardless of what happens with Starship, SpaceX have already revolutionised space launch. Falcon achieved in reality the kind of low cost, cadence and mass to orbit that the Space Shuttle promised, but was never able to deliver.

Starship and Artemis

If the Falcon 9 flight rate did level off at 200 per year, there would have to be 6 Starship launches next year rising to 59 by 2028 to maintain growth rates. On the assumption that SpaceX wants to maintain such a pace (they pretty much have to in order to meet Musk’s target for Mars) then an imminent flattening of the Falcon 9 growth curve would show up in aggressive plans for Starship flight rates - but there is some evidence which has emerged that they do not think that such a rapid growth curve is needed.