Henry Spencer said this quote

Supplying fuel for a Mars expedition from the lunar surface is often suggested, but it's hard to make it pay off - Moon bases are expensive, and just buying more rockets to launch fuel from Earth is relatively cheap.

~ Henry Spencer

The Orion capsule uses an escape system quite like that of the Apollo spacecraft in the 1960s and 70s: an 'escape tower' containing a solid-fuel rocket that will pull it up and away from Ares I in a pinch.

~ Henry Spencer

Whether solid rockets are more or less likely to fail than liquid-fuel rockets is debatable. More serious, though, is that when they do fail, it's usually violent and spectacular.

~ Henry Spencer

Sometimes people wonder why aeroplanes are so cheap and rockets are so expensive. Even the most superficial comparison shows one obvious difference: aeroplane engines use outside air to burn their fuel, while rockets have to carry their own oxidisers along.

~ Henry Spencer