The best way in handling in this situation is that in order for the astronaut to be able to get back to the shuttle is that he or she should take an object from his or her tool belt and to be thrown out away from the shuttle. This will allow her to weight lightly and safely return to the shuttle and would be easier for his or her to do so.
You can find your answer here www.rsc.org/education/teachers/resources/jesei/minerals/students.htm
Answer:
y = 17,89 m
Explanation:
Let us fixate the reference point in top of the building, from where the watermelon is thrown down. We will assume also that the positive axis of our system points up. We describe the watermelon’s motion with the equation:

Clearing the equation so we isolate y we have that:

Making a substitution with the values from the statement we have:
]
So, this skyscraper is about 17,89 m tall; which is not very tall for a skyscraper but who am I to judge. 17,89 m is also the displacement of the watermelon from the point it was thrown down.
I hope everything was clear with my explanation. If I can help with anything else, just let me know. Have an awesome day :D