LAUNCH DAY Coverage with video links begins here:http://forum.nasaspaceflight.com/index.php?topic=27391.270
DOCKING Coverage begins here:http://forum.nasaspaceflight.com/index.php?topic=27391.msg917866#msg917866
MANUAL DOCKING TEST Coverage begins here:http://forum.nasaspaceflight.com/index.php?topic=27391.855
RE-ENTRY AND LANDING Coverage begins here:http://forum.nasaspaceflight.com/index.php?topic=27391.975
At the suggestion of TonyQ last week, I have now had a chance to do (in the words of a cricket commentator many years ago) some mental arithmetic with a pocket calculator to see when it is reasonable to expect the Shenzhou 9 launch. Any such calculations must come with a health warning because I am looking at the decay rate of Tiangong 1 and future decay rates are difficult to predict with accuracy because we do not know how the upper atmosphere's density will vary.
Anyway, here goes.
I looked at three periods of Tiangong 1 decay, as follows: dates are given as days of the year, and then the orbital period at that time is shown:
Period 1 278.8187 - 91.3725 min to 298.7771 - 91.2010 min
mean decay rate is -0.008593 min/day
Period 2 308.4507 - 91.2259 min to 319.2649 - 91.1595 min
mean decay rate is -0.006140 min/day
Period 3 322.5959 - 92.0136 min to 331.1051 - 91.9699 min
mean decay rate is -0.005136 min/day
For part of Period 2 Shenzhou 8 was attached and this will have affected the decay rate. So I have used only the decay rates for Periods 1 and 3. The geometric mean of these is -0.006643 min/day.
The 31 circuit repeating orbit period is ~91.20 minutes, so the orbital period has to drop from 91.9699 minutes: with the mean decay rate this will take 115.9 days from day 331.1051 in 2011, which brings us to day 82 in 2012, which is March 22.
So these ball-park calculations suggest that the launch of Shenzhou 9 in the final third of March 2012 is a reasonable expectation.
Please do not remind me if this turns out to be wrong!!!!!
(Have I missed any horrendous typos? - apologies if I have!)