Using this for CAS/TAS conversions:
https://aerotoolbox.com/airspeed-conversions/
And
L = 0.5 * CL * Rho * v^2 * S
Or
S = L / (0.5 * CL * Rho * v^2)
Or
v = SQRT (L/(0.5 * CL * Rho * S))
Bad aerodynamic quality wing, so assume CL=1
At 130K ft altitude, Rho is less than 1% of the sea level (assume 0.5%), so Rho = 0.005 * 1.2 = 0.006 kg/m3
With 90 km/h TAS (let's make it easy and assume 108 km/h = 30 m/s), gives a CAS of 1.7 m/s.
Assume a required lift of 50kg.
Results in S = 50 / (0.5 * 1 * 0.006 * 1.7 * 1.7) = 5767 m2 (yeah ...)
To compare, a Cessna 172 at sea level (weight 1200 kg, assumed stall speed 20 m/s):
S = 1200 / (0.5 * 1.2 * 1.2 * 20 * 20) = 4 m2 wing surface
The actual Cessna wing surface is a little bigger, though the magnitude is correct.
The glide bomb with a more reasonable wing surface of 2 m2, gives a CAS at 130K ft altitude:
v = Sqrt ( 50 / (0.5 * 1 * 0.006 * 2)) = 91 m/s
TAS = 810 m/s
Also ridiculous, supersonic.
And, we have the challenge of getting from CAS = 0 m/s when the balloon bursts to a flyable CAS. Given the high TAS, a huge amount of (potential) energy needs to be converted into kinetic energy (the TAS), before the thing starts flying.
The Orcs launch their Glide bombs from a fighter yet, at high speeds, so, the glide bomb launch is assured to be in a "wings flying" condition.
Please correct me, when I am wrong.
Another item to keep in mind is, that when the aerodynamic speed CAS is low, the TAS is very high at high altitudes, resulting in high inertial loads on the frame structure, when the frame is maneuvering or experiencing turbulence.