Scenarios for QKD in space. Possible satellite-based QKD implementations. 1. Ground-to-space, where the photon source is on the ground and the satellite only carries detectors. 2. Space-to-ground, where the satellite carries a source and detectors. 3. A platform that can beam down to two ground stations simultaneously. 4. Inter-satellite QKD which could be the building block for a long baseline test of quantum correlations. To enable configurations 2-4 with Bell violation-type measurements, a source of entangled photons in space must be demonstrated.