Read the September/11-17/2007 issue of the periodical FLIGHT INTERNATIONAL,
page-11, if you can get hold of it.

In the article...Burt Rutan reveals improvements being made to the upcoming
White Knight II (WK2) carrier aircraft, and the Space Ship Two (SS2) rocketplane.
The design improvements will be made public next January.
Suffice it to say that one design improvement will elliminate the dangerous roll
characteristics experienced by SS1.

The tragic explosion this summer that claimed three lives will not delay the
"roll-out" of the White Knight II carrier plane during the first half of next year.
The test-flights for WK2 will take place sometime duuring the summer or autumn
of 2008.

Yes, the powered flight-tests for the SS2 spaceplane will be delayed until sometime in
2009, but that should not prevent drop glide-tests being performed before the end of next year.

While the loss of three lives is tragic, they did not die in vain; the explosion of nitrous-oxide
may have resulted from the fact that temperatures that July day at the Mojave Desert site
were above 100 degrees Fahrenheit; and nitrous-oxide becomes dangerously volatile
above 98 degrees Fahrenheit....There's a simple safety solution to that danger/problem.

BTW, Burt Rutan is not a rash and impatient project manager and developer.
He knows that NASA's space shuttles have a 1/70 chance of killing someone.
He wants his Virgin Galactic spaceplane/carrier plane system to be at least 100 times safer;
maybe even 600 times safer, matching the safety statistics for American passenger-carrying
aircraft in 1931 [Ford Trimotor, Sikorsky flying boats], when you had a 1/33.000 statistical
chance of dying in flight.

Jacob