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SpaceX Starship prototype days away from first Raptor static fire test

3 min read

SpaceX’s latest Starship appears to be just a few days away from becoming the first full-scale prototype to attempt a static fire test with a functional Raptor engine, potentially setting the rocket up for a hop test in the near future.

On April 26th, SpaceX teams successfully filled the fourth full-scale Starship prototype with ~1000 metric tons (~2.2 million lb) of liquid nitrogen, pressurized it to roughly 5 bar (70 psi), and exerted hundreds of tons of force on its “thrust puck” engine section with hydraulic rams. Every part of the test appears to have been completed without issue, making Starship SN4 the first to pass cryogenic proof testing and graduate to riskier tests.

Since then, SpaceX technicians and engineers have been carefully inspecting Starship and likely cleaning its cavernous propellant tanks, while also preparing a lone Raptor engine for installation. By all appearances, that engine installation milestone could occur anytime within the next 24 hours and based on public road closure schedules, the first static fire attempt could occur just a day (or less) later.

SpaceX’s latest Starship prototype could be just a few days away from its first Raptor static fire test. (LabPadre)

Capable of producing at least 200 metric tons (~450,000 lbf) of thrust, SpaceX CEO Elon Musk recently revealed that Starship SN4 will only have one Raptor engine installed. Instead, the first multi-engine static fire and flight tests are planned for its successor, Starship SN5, with SN4 apparently set to feature an asymmetric engine layout.

Starship SN4’s thrust structure and engine section are pictured here on April 12th, confirming that it’s nominally designed to host three engines. (NASASpaceflight – bocachicagal)

Designed for three engines in a triangle formation, Starship’s existing engine section and thrust structure (thrust puck) would need an inefficient one-off redesign or heavy modifications to allow a single Raptor engine to be installed directly in the center of the rocket. Unsurprisingly, SpaceX chose not to waste resources on a one-off addition to a serial prototype. Instead, if Starship survives static fire testing and the asymmetric stress that will create, the rocket may apparently attempt to launch and land with the same setup.

This would very likely result in Starship SN4 both lifting off and landing at an angle, effectively drifting its way off the launch mount and onto an adjacent landing pad.

Raptor performs a static fire test in McGregor, Texas. (SpaceX)
Starship SN4 could soon attempt to replicate Starhopper’s spectacular 150m hop. (SpaceX)

Before that potentially bizarre flight test and the static fire that must precede it, however, SN4 must also complete the first full-scale Starship wet dress rehearsal (WDR), referring to the process of fully fueling a rocket and performing a launch countdown without actually launching. It’s likely that SpaceX plans to roll Starship SN4’s WDR directly into a static fire test, meaning that the massive rocket could ignite a Raptor engine as early as Friday, May 1st.

Stay tuned for visual confirmation of Raptor engine installation on Starship SN4!

SpaceX Starship prototype days away from first Raptor static fire test

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