Skepticism
Nobody outside JP Aerospace seems to know how the problems of high drag and low lift/drag ratios that are very typically found at hypersonic speeds might be overcome in such a vehicle, and a large degree of skepticism exists.
An orbital, thermosphere, or even mesosphere airship would face many practical and theoretical challenges and would represent a remarkable technical achievement.
Read more about this topic: Orbital Airship
Famous quotes containing the word skepticism:
“No actual skeptic, so far as I know, has claimed to disbelieve in an objective world. Skepticism is not a denial of belief, but rather a denial of rational grounds for belief.”
—William Pepperell Montague (1842–1910)