juvva wrote:I remember reading somewhere ( need to dig up the source), that the landing strategy is now changed. The engine in the center will be on and firing all the way to touch down(no free fall).
ISRO animations on youtube show the central engine, thrusting all the way down to the surface, upto touch down....
FWIW: (Disclaimer: I do not know exact details of landing strategy but..)
- Landing strategy basics hasn't changed from months of extensive calculations/testing/checking/double_checking etc..As we know, it is not changed at spur of the moment or as we go - not the basic strategy.
- Particulars, of course, will change, as designed by last phase calculations after camera(s) has found the exact 'suitable site' within the landing-site ellipse (pre selected area of about 10-20 km area of ellipse shape land). No one knows the exact place yet and no one will know before Vikram decides.
- Calculate exact velocity vector, distance, and gravitation acc of moon at that point from on-board navigational computer.
- Feed exact delta-V data needed to on-board inertial guidance system so that impact velocity is zero (or as close to zero as possible). (For this, the engine can run all the way to touch-down or switch off a little earlier (in case the velocity is negative and lunar acc will make it zero at height=0).
Everything has to work nearly perfectly as there is very little room for error. There is very little time to react and try it again. (In Apollo's language, IIRC they called is "dead man's curve" .. after that you do not have luxury to go up and try again.. if you did not get it right then you will be dead).
I do remember watching Apollo 11 - when they landed the famous "Houston, Tranquility Base here. The Eagle has landed." was answered "Roger, copy that.." but the tension in even the mission control's voice was audible for people to notice. (Normally people there speak without emotion but that relief in the voice was noticeable in this case)