AORV
The smallest of the AORV's (Automated Orbital Resupply Vehicles), the Belle ORV’s main advantage - and disadvantage - is its size. Built on a Belle A upper stage, the pressurized cargo container can be launched on relatively small and cheap launchers. Best suited for frequent supply missions or where timeliness is a priority.
Designed to maximize use of existing technology, the Augustus RRV (Rendezvous Resupply Vehicle) reuses the service module and most of the exterior command module hardware of the Leo CSM. In place of crew, it is filled with an autonomous avionics package and pressurized supply pallets. It has a reasonable volume and can be flown on the same launch systems as the Leo CSM. Fitted with a parachute and heatshield, it can also be used to return precious experiment data to the surface. The Block II variant features an APAS docking port and additionally the Block IIB uses the 1.5m diameter "Malhena" Service Module.
The Rhea ORV is based on the Titan Transtage and is large enough to mount a MOS-DM Docking Mechanism, allowing crew to travel in and out of the pressurized compartment without conducting an EVA. Having both pressurised and unpressurised containers, it can send up experiment palettes and hardware to be mounted to the outside of the station as well as supplies. The downside is its size and weight, as it requires a relatively large and expensive launch vehicle.
The Aardvark is the Apollo programme's answer to an autonomous resupply vehicle. Designed primarily to service the ETS Spacelab, the Block I has a pressurised container for cargo deliveries and trash removal, whilst the Block II adds an unpressurised compartment for shipping hardware and components to the station. A cut down variants without cargo also serves as a tug for manoeuvring space station modules into position.
