[rtkwe]

All the operating human launch systems are just capsules meant to either free fly or dock at a station, they don't have airlocks to let people out so using them for a Hubble repair would require a lot of modification and danger to use the whole capsule as an airlock. [0]

[0] Except Soyuz I guess their orbital module would allow you to keep the descent module pressurized but it's still way outside the design so there's no telling if the module would remain operational.

[jccooper]

Soyuz has been used for spacewalks before, and the cabin is tolerant of vacuum. They haven't done that in ages, so it's possible that's been optimized out, but I'd suspect that requirement's been respected over the years.

[rtkwe]

Neat, didn't know that. There are of course other issues like how do you keep them in proximity while you do the work that could stretch days, ships don't usually free fly that close to each other for long the Hubble missions done with the shuttle all included hard captures of Hubble with the Shuttles.