[DonRotolo]

My direct knowledge is limited, but here is what I believe to be accurate.

The center hub design appears to have been done that way to limit the stresses from thermally-induced dimension changes. If that were solid, the spokes would rip out of the outer shell when it cooled. The way it is done it can flex a little.

Investment casting made with an expanded polystyrene blank (in the gross shape you need) surrounded by sand could make this. Specifically called lost-foam casting, the idea is to pack sand around your styrofoam blank, fill it with hot metal (vaporizing the foam). The sand is reused, but the foam is lost. OK for low volumes and relatively coarse surface finishes. This is how things like high-end lighting fixtures are cast. The sand is re-used. Higher-end shops can make net-shape castings needing minimal machining with this process.

Sand casting uses a hard blank, the sand retains the shape as it's pulled off the blank - you can't make undercuts like this. You can use a foam insert for undercuts, but mixed castings like that are specialty stuff. This is how a large bell is cast. Again, the sand is re-used.

If you have selected a vendor, or find a potential vendor, ask THEM how they'd make it, especially ask if it is too large for lost-foam. It might not be.

Remember in the design to consider how the metal will get in, and how the air will get out. Usually you pour 20-30% more metal just to fill the sprues and vents. Air bubbles would be bad. Design these in from the start.