Technically Soyuz can return a small amount of cargo, but it is extremely weight and volume limited. I couldn't find a precise figure, but it looks like it can return at most 50kg or so of cargo, in addition to crew.
Dragon can return about 2500kg in total (though it is quite volume limited), and has special facilities such as cargo racks that can support, for example, a powered freezer to hold scientific samples requiring such facilities.
None of the other operational vehicles -- Progress, Cygnus or HTV -- have any cargo return capability.
So the quote is correct in two respects: firstly, Soyuz isn't generally considered a "cargo vehicle"; and if you expand that definition, Soyuz can only carry an extremely small amount of a limited subset of possible return cargo that does not include the most interesting payloads such as frozen biological samples.
When the Commercial Crew vehicles become operational in the next couple of years they will also provide some cargo return capability, but that isn't their primary purpose and will be fairly limited under most circumstances.
The second round of the Commercial Cargo program -- CRS2 -- has selected Sierra Nevada Corporation's Dream Chaser in addition to Dragon and Cygnus. Dream Chaser is a spaceplane that will provide substantial cargo return capability by landing on a runway. This will subject the payload to lower g-forces than Dragon and allow for a very short interval between leaving the station and cargo offloading and processing on the ground. Such capabilites will be extremely useful for returning delicate and time-sensitive experiments.
So, until Dream Chaser becomes operational, almost all cargo return capability will be provided by Dragon; and right now, the cargo that is returned not on Dragon is on the order of a rounding error.
Thanks, that's interesting! Do you know if the future upgrades to Dragon with propulsive landing for the crew return will provide similar capabilities for fast landing at bases as the Dream Chaser?
First flights of Dragon 2 will splash down under parachute because NASA is nervous about propulsive landing. When propulsive landing happens (probably at CCAFS) we'll see how fast can the capsule be decontaminated (superdraco uses hydrazine fuel, will need something like this: https://www.wired.com/images_blogs/dangerroom/2011/11/120310...).
Dragon can return about 2500kg in total (though it is quite volume limited), and has special facilities such as cargo racks that can support, for example, a powered freezer to hold scientific samples requiring such facilities.
None of the other operational vehicles -- Progress, Cygnus or HTV -- have any cargo return capability.
So the quote is correct in two respects: firstly, Soyuz isn't generally considered a "cargo vehicle"; and if you expand that definition, Soyuz can only carry an extremely small amount of a limited subset of possible return cargo that does not include the most interesting payloads such as frozen biological samples.
When the Commercial Crew vehicles become operational in the next couple of years they will also provide some cargo return capability, but that isn't their primary purpose and will be fairly limited under most circumstances.
The second round of the Commercial Cargo program -- CRS2 -- has selected Sierra Nevada Corporation's Dream Chaser in addition to Dragon and Cygnus. Dream Chaser is a spaceplane that will provide substantial cargo return capability by landing on a runway. This will subject the payload to lower g-forces than Dragon and allow for a very short interval between leaving the station and cargo offloading and processing on the ground. Such capabilites will be extremely useful for returning delicate and time-sensitive experiments.
So, until Dream Chaser becomes operational, almost all cargo return capability will be provided by Dragon; and right now, the cargo that is returned not on Dragon is on the order of a rounding error.