Can you sacrifice the same permanent to pay costs for two different spells or abilities simultaneously?

No, you cannot sacrifice the same permanent to pay for two different costs at the same time. When you sacrifice a permanent as a cost, it is immediately moved to the graveyard as part of paying that cost. Once it is gone, it no longer exists on the battlefield and cannot be sacrificed again.

This is grounded in CR 118.12, which states that costs are paid in full before an effect happens, and CR 701.17a, which defines sacrificing as moving a permanent you control from the battlefield to your graveyard. The moment the sacrifice is completed for the first cost, the permanent no longer exists.

Even in situations where two triggered abilities trigger at the same time and both demand a sacrifice cost, you must choose a different permanent for each or simply be unable to pay one of the costs. You cannot reuse the same object once it has left the battlefield.

Concrete example: You control a single Ornithopter and two triggered abilities both require you to sacrifice an artifact. When the triggers resolve one at a time (CR 603.3), you may sacrifice the Ornithopter to pay for the first trigger. When the second trigger then asks you to pay, the Ornithopter is already in the graveyard — it is no longer a battlefield permanent you control — so you cannot sacrifice it again.

In short, each sacrifice cost requires a distinct, living permanent on the battlefield at the time the cost is paid (CR 118.12, 701.17a). Sharing one permanent across two costs is never legal.