This is an impossible question, unless taken absolutely literally. If your question was how much speed do you (meaning me) need, then that is possible to answer. However, since you meant how much speed does "one" need to hit it, that's impossible to say. It depends on many factors, such as height of skier, weight of skier, the clothes the skier is wearing, and more. The amount of drag the skier experiences in the air is unique to each person. Your question truly has no purpose, except perhaps to elicit the answer "fast".