What's the point of building a 20 km stratosphere-scraper for monkeys? One would most likely use it as a launch platform: I would guess a capsule leaving a 20 km long evacuated linear driver won't be subject to such harsh conditions as at sea level.
Michael S. Lorrey writes:
> If you are building a 20 km tall building it certainly wouldn't do to
> have the pressure at the top floors equal to the outside atmospheric
> pressure. And building it airtight to maintain a 3km pressure level
> would necessitate enough added weight that you'll be reaching
> diminishing returns at some point.