40% less than the maximum payload capability of White Knight II at 50,000ft
But what is that, you may well ask, and how on Earth did you find that out?
On the afternoon of 23 January Virgin Galactic president Will Whitehorn said to me in a one-on-one interview , "White Knight II has the [payload] capacity for 40% more weight than SpaceShipTwo is."
I think WK2's payload capacity is 13,600kg (30,000lb)
So that makes SS2's mass, drum roll please, 9,740kg or 21,428lb
So why am I so ready to pick 30,000lb as the WK2 capacity?
I actually got the original WK2 payload capacity figure from an individual from the Swedish Space Corporation (SSC) when I was at the SSC/Virgin Kiruna, Sweden spaceport event last year
SSC wanted to launch sounding rockets from WK2 over Sweden's Esrange test site in its northern latitudes and so they had been told the payload capability. At first Galactic did not want to confirm this but have since
On Wednesday this week Will Whitehorn's exact words in my one-on-one interview were that WK2 could "carry more than 30,000lb to 50,000ft"
(However at the UK's Rutherford Appleton Laboratory space event last year Whitehorn said that it could carry 30,000kg, yes I mean kilograms, but then he did not reply to my email asking for clarification)
But despite all that I prefer to stick with the SSC official's statement. Why?
When I asked Will what the landing speed of SS2 was he said "at least 115kt". Did that mean 300kt I asked. "No", he said, laughing, "that would be too much." So now you understand the game that is being played
For commercial reasons they don't want to give exact figures but when potential customers blab them there is a standard public relations reaction of fudging the issue
With the evidence I have I will say that while WK2 can carry 30,000lb to 50,000ft, safely, I admit that when needed perhaps, as a guess, it could probably pull 2,000lb more but it will be pushing the envelope
Other facts I know that bolster this view are that;
Whitehorn told me that WK2 will, when not mated with SS2, be able to carry out a "viking departure". To put that in layman's terms it is where the aircraft climbs vertically, on its tail, immediately after taking off
And the reason for four engines for WK2 is that there is a requirement for an engine out capability. Alex Tai told me they wanted an 'on take-off' engine out capability last year