Anyone have any idea how much horizontal distance the grid fins add to the F9 descent? ie if it was coming down vertically from apogee (yes, I know it doesn't do that), how much lateral movement could the fins provide before landing?
According to some SpaceX data, they can tilt the stage 20degs, but once tilted that imparts an acceleration to the stage, so it's not as simple as 20 degrees from apogee. I think.
Bare minimum a substantial % of total altitude.I would think 1/3 of altitude should be a sure thing.Its possible its as much as 1:1 or even more.Just as a reference, Skydivers can track glide 1:1 very easily, the pros can exceed 2:1 (that's without the winged suits).An important question to even try to use this logic is how high grid finds have full authority.Even if a 20 degree deflection is possible, it probably isn't at hypersonic speeds (might scorch the stage lateral skin too seriously).The important aspect is once lateral movement is established, the fins job is much easier to sustain that motion.
Bare minimum a substantial % of total altitude.I would think 1/3 of altitude should be a sure thing.Its possible its as much as 1:1 or even more.
Quote from: macpacheco on 01/06/2016 07:26 amBare minimum a substantial % of total altitude.I would think 1/3 of altitude should be a sure thing.Its possible its as much as 1:1 or even more.Just as a reference, Skydivers can track glide 1:1 very easily, the pros can exceed 2:1 (that's without the winged suits).An important question to even try to use this logic is how high grid finds have full authority.Even if a 20 degree deflection is possible, it probably isn't at hypersonic speeds (might scorch the stage lateral skin too seriously).The important aspect is once lateral movement is established, the fins job is much easier to sustain that motion.Not. even. close. They are just steering fins at the tail like an arrow. Not wings.
The grid fins are doing a lot of work, just to keep the thing steady.
For reference, an SRB recovery attempt (granted, in that example the CoM is higher up, but the shape is similar).
It's a bit more complicated than an aerodynamic bomb being steered to the target. This is a blunt shaped 50m long grain silo coming down at ludicrous speed. The grid fins are doing a lot of work, just to keep the thing steady.For reference, an SRB recovery attempt (granted, in that example the CoM is higher up, but the shape is similar).