Why so long between Orion missions?

[Ranb]

I'm reading on Wikipedia that EM-1, the circumlunar mission will be in 2018 with EM-2 in 2021.  While the EM-2 mission sounds very interesting, why the long periods of time between each?

Ranb

[cjameshuff]

It simply won't be ready for a manned mission before 2021. This latest test didn't have the launcher or service module, or even a complete capsule. EM-1 would be another test flight of an incomplete system, using a Block 1 SLS with a substitute upper stage. EM-2 would be the first flight of a complete system.

[Ranb]

Thanks.

[AstroBrant]

It simply won't be ready for a manned mission before 2021. This latest test didn't have the launcher or service module, or even a complete capsule. EM-1 would be another test flight of an incomplete system, using a Block 1 SLS with a substitute upper stage. EM-2 would be the first flight of a complete system.

Yeah, but it's frustrating. I'm kinda on a clock, here. My bypasses are 15 years old.