I've been reading about the Auxiliary Power Unit (APU) on the Ariane 6 upper stage and am looking for a schematic showing how it's integrated into the stage.

From Thermal Control of the Cryogenic Upper Stage of Ariane 6 I found this, but it only mentions the APU as being located on the ViTF, but does not call it out on the drawing.

enter image description here

The video Ariane 6 APU system - video presentation includes this, but it's not very helpful.

enter image description here

Does anyone know of a schematic that shows clearly how the APU is integrated into the upper stage?


1 Answer 1


I found a doctoral dissertation that discusses the possibility of increasing the thrust of the two nozzles (TAPUs) of the APU on Ariane 6's upper stage. The drawings in the dissertation when combined with the two spherical tanks in one of the illustrations you've found should hopefully help:

plan view
3d view
Source: Gradetzke, Malte. Investigation of an Aerospike based GOX/GH2 Dual-Mode-Thruster system for a liquid propellant upper stage. Diss. Universität Stuttgart, 2020.

Note: the first and third drawings above are from "Classified internal documents" from "Arianegroup Bremen", so they're as good as they publicly come.

The TAPU nozzles are easy to spot in most photos. Based on the spherical tanks and the two TAPUs I've circled below, I've added an arrow to what I conclude is the APU:

esa photo
Source: ESA (use link for full resolution)

  • 1
    $\begingroup$ Great stuff, better than I expected. Thanks for the link to the paper. $\endgroup$ Commented May 20, 2023 at 11:52

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