VLD meaning in Space Science ?

A very-low-drag bullet (VLD) is primarily a small arms ballistics development of the 1980s–1990s, driven by shooters' desire for bullets with higher degrees of accuracy and kinetic efficiency, especially at extended ranges. To achieve this, the projectile must minimize air resistance in flight. Demand has been greatest from military snipers and long-range target shooters, including F-class and benchrest competitors, but hunters have also benefited. Most VLD bullets are used in rifles. VLD bullets typically have a ballistic coefficient greater than 0.5, although the threshold is undefined.

Bullets with a lower drag coefficient decelerate less rapidly. A low drag coefficient flattens the projectile's trajectory and also markedly decreases the lateral drift caused by crosswinds. The higher impact velocity of bullets with low drag coefficients means they retain more kinetic energy.