Yes—Aperture can work with referenced originals rather than storing originals inside the library bundle.

For new imports, Aperture’s import options let you choose where originals are stored: inside the library, in their current location, or in a specific location. To keep originals on an external drive, import them to a specific location or leave them in their current location and have Aperture reference them.

For photos already managed inside the library, use Relocate Original. That moves the original files to a new folder while preserving Aperture’s references to them.

One important limitation: this applies to original files. Aperture still keeps its database and adjustment data in the library, so it won’t become completely empty. But if your main concern is the large original image files, referenced storage plus Relocate Original is the approach you want.