A defensive shield, commonly referred to as simply a shield and sometimes as a Holtzman shield, was a protective energy field that could surround the person who wore it.
Technical Information Edit
A shield was produced by a Holtzman generator, the field deriving from Phase One of the suspensor-nullification effect. Shields can be calibrated to permit the passage of matter below given speeds. This is vital in personal defense shields, as one would suffocate within a shield that did not admit atmospheric gasses. Depending on the shield's setting, the object's speed while passing through the shield would range from six to nine centimeters per second. A shield could also be set to cover either the left or right side of a person if the specific need for it arose.
Shields used to protect installations can and usually do have far lower penetration velocities, as life support technologies can be used to recycle atmosphere while the shield is active.
However, if a lasgun beam hit a Holtzman field, it would result in sub-atomic fusion and a nuclear explosion. The center of this blast was determined by random chance; sometimes it would originate within the shield, sometimes within the laser weapon, sometimes both.
With the widespread use of shields, anyone of even minimal importance wore a body shield to protect against criminals, assassins, and accidents. Such a practice made the use of projectile weapons and thrown blades partly obsolete. The only effective combat method was the deft use and careful precision of a handheld dagger, if moved slowly enough. New styles of fencing and knife fighting were developed to take advantage of this one small vulnerability.
By the time of Muad'dib, when thinking machines had long ceased to be a threat, the shield had been adopted for use in personal defense. These shields were form-fitting energy fields which permitted penetration only by objects that moved below a pre-set velocity. As one would be unable to breathe within a shield that did not permit atmospheric gases to penetrate it, man-portable shields had a relatively high penetration velocity, approximately six to ten centimeters per second. However, shields for ships and planetary installations could and often did have extremely low penetration velocities, as artificial life support technologies could be utilized while the shield was active.
Thus, using lasguns in a shielded environment resulted in military and environmental catastrophe, though at least one commander (Duncan Idaho) has used this phenomenon deliberately as a discouragement to his enemies.
On Arrakis, a shield never lasted long because of the planet's conditions. A shield could only remain active for short periods because its harmonic vibrations would attract a sandworm. Unlike a sandworm attracted by a thumper or other means, a sandworm attracted by a shield would be even more dangerous than normal, as something specific in Holtzman energy infuriates them.
Behind the ScenesEdit
The Holtzman Shield is a potent literary device: it makes some directed-energy weaponry impossible against any worthwhile opponent, and also proves traditional projectile-based firearms and missiles ineffective, adding to the feudal atmosphere, and enforces the usage of mêlée weaponry despite other more advanced technology.