There are a whole bunch of items that you'd want to add to a cargo Dragon to make it fit for human travel. IMHO, the two standout items are launch abort handling and docking, but there are a whole bunch of other stuff you'd want as well (in terms of life support, advanced communications, etc.).
On these two items:
NASA doesn't want crew in the Dragon capsule until it has a launch abort system (LAS) that would let it get away from a failing booster rocket. The current design involves much stronger versions of the orbital thrusters; this is scheduled for tests this summer.
Also, the cargo Dragon doesn't currently dock autonomously with the ISS; instead, it effectively parks itself close enough for the station's robot arm to grab it and move it to a berthing port. When Dragon leaves, the process is reversed --- meaning that the arm and its support systems need to be operating in order for the spacecraft to leave. In normal operations, that's manageable --- but one of the things you want in a crew transport is that it be able to leave a failing station quickly in an emergency. The berthing arrangement doesn't really suit.
NASA is planning to deal with that by adding new docking hardware to the station, and mounting compatible hardware on the Commercial Crew vehicles (whoever winds up winning that competition). But the hardware isn't there yet; it's actually scheduled to go up on Dragon cargo flights next year.
Comments
There are a whole bunch of items that you'd want to add to a cargo Dragon to make it fit for human travel. IMHO, the two standout items are launch abort handling and docking, but there are a whole bunch of other stuff you'd want as well (in terms of life support, advanced communications, etc.).
On these two items:
NASA doesn't want crew in the Dragon capsule until it has a launch abort system (LAS) that would let it get away from a failing booster rocket. The current design involves much stronger versions of the orbital thrusters; this is scheduled for tests this summer.
Also, the cargo Dragon doesn't currently dock autonomously with the ISS; instead, it effectively parks itself close enough for the station's robot arm to grab it and move it to a berthing port. When Dragon leaves, the process is reversed --- meaning that the arm and its support systems need to be operating in order for the spacecraft to leave. In normal operations, that's manageable --- but one of the things you want in a crew transport is that it be able to leave a failing station quickly in an emergency. The berthing arrangement doesn't really suit.
NASA is planning to deal with that by adding new docking hardware to the station, and mounting compatible hardware on the Commercial Crew vehicles (whoever winds up winning that competition). But the hardware isn't there yet; it's actually scheduled to go up on Dragon cargo flights next year.