>>1305751Speaking of Ariane 5 being human rated:
All the way back in 2013, it was looking like SLS might never be actually approved to fly, and there was a lot of speculation of what on earth could launch it. It was around this time that ESA got into the collaboration with NASA with the Orion capsule, the only thing to survive the Constellation Program, and ESA proposed the use of the ATV's service module for the Orion. It became the European Service Module, and that, along with Orion, are the only parts of SLS which are completed and ready....
In 2013, ESA and CNES proposed the use of Ariane 5 for human spaceflight missions to the Moon, especially if SLS was considered a paper rocket in 2013. The proposals were looked into, and it was suggested that Ariane 5 with a ECS upper stage (cryogenic fueled) could do missions to the Deep Space Gateway and missions to the Moon.
NASA rejected this proposal, however, and decided to instead press ahead with SLS development.
Now, Ariane 6 is on the horizon. While it's not human rated, with the way things are now, the only thing which really needs to be done to make it so, would be software alterations to allow for safe abort conditions. Meanwhile, SLS is in development hell, as Boeing has announced a signficant delay, maybe up to 2 years on the main cryogenic booster stage of SLS. This means that SLS won't be ready in time for EM-1. Falcon Heavy is too narrow a diameter and Delta IV Heavy won't have the lift capability.
