CEO Elon Musk revealed that SpaceX shattered a worldwide rocket record during a recent Raptor engine test, hitting the crucial Starship component past year-old performance goals.
On August 17, the SpaceX CEO unexpectedly published a photo of a Raptor test and a corresponding graph showing the engine room pressure, confirming that the company had successfully driven the engine to record levels. Musk says an unspecified Raptor – possibly serial number 39 (SN39) – briefly reached a main combustion chamber pressure of 330 bar (~ 4800 psi) during a controlled fire – and remained intact after shutting down.
Outside of laboratory tests for subscale, the highest known combustion chamber known for full-scale, orbital-class rocketry was achieved by the Soviet Union in the 1980s with the RD-701 engine. Although the exceptionally unique motor was canceled before it could be used, it apparently reached pressures of 290-300 bar in one mode of operation. Now, however, SpaceX and its Raptor engine appear the new world record holders – and by an enormous margin.
The new crown of Raptor comes roughly 18 months after Elon Musk revealed that the engine had the Soviet RD-270 with much higher stationary combustion (FFSC) with a higher sustained chamber pressure (~ 257 bar vs 255 bar). A few days later the same Raptor went even further, crossing the Russian RD-180 engine its working pressure of 257 bar with a height of 268 bar. Still, it took SpaceX 6-12 months to refine Raptor into an engine capable of operating even close to that pressure for more than ~ 10 seconds. In July and August 2019, Raptor engine SN6 flew twice on Starhopper, culminating in a ~ 60-second, 150-meter hop, which ended with the engine itself almost seconds before it came to destruction.
Almost exactly one year later, Raptor SN27 launched on Starship SN5 on the same 150-meter trajectory and proved to be error-free. SN27 hardly exposes a stutterer like flare, SN27 never came close to the flamethrower-like death penalty that Raptor SN6 suffered in August 2019. In short, SpaceX continued to do what SpaceX does best, and continually refined prototypes into increasingly polished end products .
Originally announced in 2016 as a methane / oxygen completed stage combustion engine with an operating combustion chamber pressure of 300 bar (4350 psi), Raptor’s performance on August 17 means that SpaceX has already exceeded one of its performance targets. Of course, the pressure of the combustion chamber is significant, but still far less important than engine life, limitation duration limits, and reusability in the context of Starship. SpaceX would probably not print the room pressure envelope if it were unsure about many other important attributes of Raptor, but it is not yet known if Raptor ever burned for longer than ~ 90 seconds.
However, if Raptor can actually maintain room pressures of 330 bar without damaging itself, the milestone could mean that SpaceX already has the maximum pressure of Raptor boosting from ~ 200 metric tons to ~ 225 metric tons (440,000-500,000 lbf.) For Starship and Super Heavy, that 10% increase in steering could easily translate to a 5-10% increase in loadload to job per launch.
To get job, though, Raptor still has ways to go. For Super Heavy to complete a normal launch, SpaceX Raptor production will have to expand dramatically (~ 31 engines per booster) and ensure Raptor can operate reliably for 3-5+ minutes and re-reign on the fly multiple times. For Starship, SpaceX – at least – needs Raptor adults until it can burn 5-10 minutes continuously to reach a job. The company will likely also need to finish developing a custom vacuum-optimized version of Raptor for efficient orbital Starship flights.
Given just how quiet SpaceX is about most Raptor milestones, chances are the company has already made substantial progress along these lines. For example, Starship SN8 – already well on its way to completion – will probably be the first prototype to fly with three Raptor engines and will require the ability to stop and start these engines in flight to perform full fidelity 20 km (~ 12.5 mi) takeoff and landing tests. Even just maintaining 330 bar for 10-100+ seconds without destroying the engine are likely several Raptor iterations gone. Still, given SpaceX’s track record, all of these milestones are probably just a matter of time and perseverance.
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