American supremacy is on vacation
If we were willing to settle for the same level of safety as the space shuttle, there are commercial american companies that already have the capabilities of putting astronauts in space, delivering them to the ISS, and returning them to earth alive and no worse for wear.
However, if we want the system to be safer, to be sure of avoiding a Challenger-type accident again, then it's going to take between 2 and 3 years. Time is needed to develop effective emergency launch escape systems. It's hard to pull a capsule or a mini-shuttle off of a rocket that is rushing up from behind and not end up with flattened humans in the process.
