Falcon Heavy has two side boosters that are essentially standard Falcon 9 lower stage with a nose cone, along with a black interstage, as seen below.

enter image description here

But the renders that SpaceX shows of Falcon Heavy show no black interstage, as seen below.

enter image description here

Why the difference?

  • 9
    $\begingroup$ +1 nominating for the "longest question" award! $\endgroup$ – uhoh Mar 30 at 0:42
  • $\begingroup$ SpaceX artwork has been known not to be representative. $\endgroup$ – Hobbes Mar 30 at 9:30
  • $\begingroup$ The one they've got is known to work, and Heavy is sufficiently low demand and turn around time that it is adequate for the task? $\endgroup$ – JCRM Mar 30 at 9:35

The black section of the interstage is improved thermal protection added with the Block 5 version of the Falcon 9, just to increase booster reusability since the second stage engine often charred it a bit. The Falcon Heavy core is constructed very differently to a Falcon 9, however. The interstage features the upper struts connecting the two boosters to the core, which you can see folding inward on separation, so structurally it needs to accommodate that assembly and also bear the heavy stresses imparted by the boosters themselves. This likely meant there wasn't room for the improved thermal protection in design, and since it's far less critical, it was left out.

The main Block 5 features incorporated with the Falcon Heavy are the improved engine performance, grid fins, and landing legs.


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