Posted for "Larry Henney" <lhenney@attg.net>:

 Jeff,
 
 It's not the whole answer but the Nov Sport Aviation article on page 38
 acknowledges that White Knight bleed air is ducted into SS1 for purposes
 such as keeping the nitrous oxide at 66F, engine bay, and mechanisms.
 The unstated inference might be that pressurization also comes from this
 bleed air.  This and another related statement  on page 37 "every aspect
 of the pressure system is digitally monitored, and any leak of any kind
 is instantly reported on the TONU" leads me to believe that they are
 totally sealed and only face a differential change in pressure after
 release from 50K.
 
 I'm sure some math genius could tell us how much atmosphere is left
 above 50K.  Perhaps SS1 is pressurized to let's say 5000' MSL upon
 release.  The question remains, to what altitude would the cabin climb
 when the outside pressure drops from 50K up to zero (space?).  And would
 my ears pop?
 
 Inquiring minds need to know.
 
 Larry
 

"""
 So, what is the cabin pressure differential inside SpaceShipOne?
 
 And how does it get this...bleed air of the engines...doubtful?  And
 how does it control it, so you don't get the full magilla at 50,000'
 and overpressurize your brains during the initial stage?
"""