Earlier, T o d d P a t t i s t wrote:

The main problem is that it's hard to pressurize a leaky
cockpit without an engine.

A couple years ago when I was putting together a business plan for a
Perlan competitor I did design studies and a couple of low-dollar
experiments that explored several ways of reducing leakage to very
managable rates. Given those leakage rates, it seemed quite feasable to
supply pressurization from compressed gas reservoirs for a twelve-hour
flight profile.

I wonder what they did for the Spaceship One? Of course, their flight
profile is relatively brief...

Bob K.