Author Topic: Merlin and RD-180 engines  (Read 376 times)

Offline smartcooky

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Re: Merlin and RD-180 engines
« Reply #15 on: May 08, 2022, 12:40:59 AM »

The Octaweb: Suffers more heat exposure than any other part of the booster (except the engine bells)
- On Block 4, the entire octaweb was welded. This made it hard for the maintenance crews to replace it since welding literally made it part of the entire booster shell. It also needed to be cut off and refitted by welding if an engine had to be changed. Also, it is more difficult to maintain due to the brittleness of the joints - every joint has to be crack-tested
- On Block 5, the octaweb is bolted. No welding cracks to check for, but I imagine the bolt holes would still be checked. If an engine change is needed, it can be easily be unbolted, removed and refitted. Bolted octawebs also make it easier for Falcon Heavy. They are strengthened to withstand the additional stress the thrust. Previously, the centre core would require a one-off manufactured octaweb, and modifications to those on the side boosters. Now, they just have a set of three strengthened octawebs, one for the centre core, and two for the side boosters, and just swap them over.

Interesting name they chose, I would have thought that nanoweb would have been the choice.

...why? What about it is "nano"?

The Merlin engines also use a somewhat unusual pintle injector. The Merlin engines have a quite clear lineage, with many design features in common with the FASTRAC engine (which itself never got developed into a flight-ready engine) and extensive development between the Merlin 1A and the current Merlin 1D. The Merlin 1A and 1B weren't even regeneratively cooled, they used ablative chambers and nozzles. The notion that they just copied their engines from someone else is complete nonsense.

I was thinking that the first stage has 9 engines, thus the nano.  If that is incorrect then whatever the next increment from octo then.

That would be a "nonaweb". The "nano" prefix means "small", usually on the order of molecular structures, or "one billionth" when used as a SI prefix. A nanoweb would be something you image with an electron microscope.
That is precisely why I have in my post
If that is incorrect then whatever the next increment from octo then.

Its called the octaweb because its shape, not for the number of engines it supports. It is an 8 sided web-like structure supporting the 8 outer engines.

Count em'

If there was no engine in the middle, or if there were three smaller engines in a cluster in the middle it would still be called the octaweb.

FYI, Falcon 9 V1.0 had nine engines in a 3 x 3 grid - this was changed to a welded octaweb design in v1.1, and to a bolted octaweb design in V1.2 Block 5

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