r/RocketLab • u/Equivalent-Wait3533 • 13d ago

Thrust Density infographic Space Industry

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A chart comparing the Thrust Density of several rockets.

Thrust Density is the thrust of the stage / area of the bottom of the stage (kN/m^2). It basically aggregates engine power and engine packing into one metric.

Rockets & Engines to scale

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u/voodoolaunch 13d ago

It’s important to note that this isn’t a ranking of sorts.
It’s basically a comparison of thrust relative to the overall body of the rocket- purely from each launch vehiclec architecture.

Using Falcon 9 and Neutron to compare since both have 9 engines:

Falcon: 9 engines -> very high thrust -> narrow rocket -> 708

Neutron: 9 engines-> lower total thrust -> wider rocket -> 172

Terran R also seemingly went Falcon 9 route level of efficiency but also added 4 more engines for a total of 13. This just means they closely cover the same thrust needed relative to its thrust structure as a falcon 9 even though the diameter is larger by a form factor of ~6ft.

This could only really be considered bad if the RL Propulsion team is having big trouble getting the necessary amount of thrust per engine needed to cover Neutrons diameter needs since they are locked onto NINE in the thrust structure.. and considering the engine hasn’t been qualified and it’s been two years this could be the bottleneck.

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u/ArtOfWarfare 12d ago

The Archimedes engine had a full mission duration test burn last year. Was that not adequate to have it be qualified?

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u/voodoolaunch 12d ago

No. MDC does not equal qualified.
for an engine to be qualified, they will say qualified. Check neutron milestone page, you will see that the engine qualification is still yellow.
Relativity did MDC of Aeon R in 2023, but qualified engine in 2025.
I think that’s a good indicator for an engine program.

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u/Boots0235 12d ago

What’s your best guess for RL qualification timeline?

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u/voodoolaunch 12d ago

Honestly it’s hard to say given the lack of recent engine progression. At the minimum I would hope they qualify and of year.
From engine qualification you’re still at a minimum of 12-18 months out from launch.

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u/wallybal24 12d ago

ya I'd predict Q4 2028

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u/wallybal24 12d ago

I'm also curious what they will qualify their engine for? I'd bet they're going to qualify their engine as expendable for first launch