For the last few years, SpaceX has made waves with its Falcon 9 rockets. After multiple false starts, the company has successfully landed its rockets post-launch, helping to pave the way towards a reusable technology platform that would substantially reduce launch costs. Now, the company has found another gem, albeit inadvertently — its Falcon 9 rocket is capable of producing far more thrust than it was originally rated for.
In and of itself, this isn’t unusual. Engines often improve over time and manuals and documentation are designed to compensate for this. The reason the old Space Shuttle’s RS-25 engine was rated for 104.5% thrust as standard and up to 111% thrust in an emergency was because of improvements to the base design and a better understanding of its capabilities.
It might seem nonsensical to refer to an engine producing 104.5% of rated thrust as standard, but there’s a logic behind it. When the engine was designed, it was rated for 100% thrust and all of the various documentation and manuals refer to that number. Recalibrating the engine for a “new” 100% rated thrust level would have made it unclear whether any given document was referring to the original thrust of the RS-25 or its later capabilities. Using numbers in excess of 100% made it clear what absolute thrust level was being discussed.
SpaceX’s newly revised payload figures for the Falcon 9 and upcoming Falcon Heavy aren’t a matter of a few percent, however. Previously, the Falcon 9 was rated to carry roughly 15 tons to Low Earth Orbit (LEO) and 5.3 tons to geosynchronous transfer orbit (GTO). As of now, the company is claiming it can lift 25.1 tons to LEO and 9.15 tons to GTO. That’s an increase of 71% over previous figures.
SpaceX was already working on later versions of the Falcon 9 engine with higher levels of performance, but Musk has stated that these uprated thrust figures aren’t the result of any changes to the engine or its capabilities.
This seems a touch unlikely. It makes sense SpaceX would continue to iterate towards better performance, and that the company might find that some of its original estimates for maximum payload were based on overly conservative performance and safety estimates. Given the cost and difficulty of launching objects into space, it makes sense to start with enormous safety margins and then relax them over time as you develop a better understanding for how the spacecraft performs. A 1.73x performance gain means that SpaceX is basically launching 73% more rocket per rocket.
Last week, Musk was talking about launching a mission to Mars by 2018 — these new capabilities and ratings will definitely help SpaceX meet that goal.
The other thing SpaceX’s launch capabilities may do is cut into the available market for the Space Launch System (SLS). As currently envisioned, the SLS will debut in a Block I configuration capable of launching up ~77 tons to LEO (70,000kg).
Right now, the huge capability increases have only been applied to Falcon 9 — while Musk did increase the rated specification for the Falcon Heavy, the increases have been much smaller, from 58 tons to roughly 60 tons. It’s not yet clear if the Falcon Heavy will inherit the full increase from the smaller Falcon 9 — but if it did, it could put the SLS Block I out of a job. Even a 20% payload increase for Falcon Heavy would put it on par with the initial Block I goals.
There’s no chance that the SLS will actually be canceled, of course; Congress is much too fond of using NASA as a jobs program to actually do that. It’ll be interesting to see if SpaceX can bring these improvements to the Falcon Heavy.