Nothing is simple in aerospace, and I'm sure there are things I'm missing. But generally speaking, an orbital vehicle becomes suborbital when it doesn't have en

Nothing is simple in aerospace, and I'm sure there are things I'm missing. But generally speaking, an orbital vehicle becomes suborbital when it doesn't have enough speed to not fall back to the Earth. There's re-entry to contend with, but that's a solvable issue. And then there's the payload, also solvable.