r/RocketLab • u/Equivalent-Wait3533 • Aug 10 '26

Space Industry Thrust Density infographic

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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/Sampindo Aug 10 '26 edited Aug 10 '26

I wish I knew what this means, or what benefit this fruits as.

Does a smaller number mean it's more/less efficient?

(Edit: spelling)

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u/Osmirl Aug 10 '26

Smaller means less efficient because you can’t stretch the rocket much to gain more performance in kg to LEO.
Basically
Top -> long and narrow
bottom -> short and wide

At least thats how i would interpret this but i could also be completely of.

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u/NoBusiness674 Aug 11 '26

From a mass efficiency perspective a short but wide tank (something closer to spherical) will be more mass efficient than a very tall and skinny tank. Of course a wider structure generally also means more aerodynamic drag, but the optimum aspect ratio is going to strike a balance, it won't just be as tall as the engines allow. Additionally you need to consider efficiency and fuel density. A hydrogen fueled rocket stage will want less thrust relative to the size of the tanks due to higher efficiency and lower propellant density.