Assumptions for the story: The rocket pack is not unlike the scenario of the movie when I was little, "Rocketeer," in terms of viability. I have hand-waved it in my story.
- The rocket pack should be assumed for this question to be unlimited in fuel and power without subjecting harm to the character.
- There is a maximum of 10 minutes of oxygen within the helmet apparatus, and my character can wear anything from slacks to ski gear.
Given an unlimited rocket without direct effects from the rocket onto the hero: In my story, I would like the character to achieve (1) very fast travel; and (2) very high travel.
For instance, I have a part where the hero rockets to a height of an airplane, but then descends. Also, must travel distances. While the rocket is hand-waved, the limitations to the human body aren't. The hero has access to clothes you'd find in the closet (including ski gear), the 'hand-waved' rocket, and the helmet allows for 10 minutes of oxygen and protection from exhaust of the hand-waved rocket. But not space gear and not protection from effects of speed, height, pressure, or anything else.
I can handle the storyline for logistics, politics, psychology, the rocketpack, etc.; this if about survivability. For the story, what are the speed and height constraints that my hero can survive, given that she can wear warm clothing, have oxygen for up to ten minutes and needs to fly around a lot. She will have to go far and high.
Wardrobe is considered modern day, household items, upper-income western lifestyle. The hero has a credit card and knows how to use it, but is no Elon Musk. The only sci-fi is the safe, hand-waved rocket-pack and helmet with oxygen.