The initial speed of the flare on the vertical axis `V_(0y)` is equal the the upward speed of the shuttle. The flare is released from an initial height of `H =100 m` m and its motion is uniform accelerated with the acceleration `-g` downwards (because of the flare form the resistance of the air can be neglected). For the uniform accelerated motion, the relation between space, initial speed and acceleration is
`H = V_(0y)*t - (g*t^2)/2`
`V_(0y)*t = H+(g*t^2)/2`
`V_(0y) = H/t +(g*t)/2 =100/8.5 +9.81*8.5/2 =53.46 m/s`
The upward velocity of the flare (Shuttle) at the time of its release is 53.46 m/s.