The Orion Planetary design was to be launched from ground.
http://www.astronautix.com/o/orionplanetary.html
It "was" 41 m in diameter and 50 m high, and as we can see, not even close to a real project state, just a conceptual design.
Orion appeared with no purpose, and was officially developed and funded from budget as a pure orbital craft.
Various temporary early ideas were in between.
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It became a political issue on the Treaty signing, when the whole project was closed.
And as we can see http://www.astronautix.com/o/orionsaturnv.html
the really funded engineering project was 10 m in diameter to match Saturn V, which became its launch booster when the project got enough mature to think about that.
And they had to cut their dreams from 41..130 m down to 10 m actually designed.
Because expectations vs reality.
Every asymmetric ion distribution does, and the Orion charge is designed to be as extremely asymmetric as possible (because of direct blast).
It's the most EMP nuke among the nukes.
Pure fission plays no role, as it also must be asymmetric for the Orion-like propulsion.
It does, but is a waste of fissile materials.