###Federation starships despite their appearance of near-infinite energy, expend the bulk of that energy in three ways, offensive weapons, defensive shielding and energy manipulation on-board ship for environmental controls, internal gravity, and inertial dampeners. Of the three, defense utilizes a great deal of the energy generated.

 - Technically, the shields are always up albeit in a reduced energy configuration. The deflector array is always in operation as long as the ship is in space, deflecting particles of matter which could have disastrous effects on the ship or its crew. This technology is commonly known as the navigational deflector.

>**[The navigational deflector][1]** (also known just as the deflector, the deflector array, the deflector dish, the main deflector or the nav deflector for short) was a component of many starships, and was used to deflect space debris, asteroids, microscopic particles and other objects that might have collided with the ship. At warp speed the deflector was virtually indispensable for most starships as even the most minute particle could cause serious damage to a ship when it was traveling at superluminal velocities.

 - This low-intensity shielding, however is not the same as the main shields which protect the ship against attacks from spaceships and other potential threats. These shields require an enormous power drain on the ship's energy supplies and are thus only utilized when the ship is under attack, in an extreme environment, or attempting to prevent transporter-based technology from entering the ship.

 - Since the drain on ship's power is both considerable and requires significant crew to manage and maintain power management, raising the deflector screens to a defensive posture requires a call to red alert to bring out the proper crew and to set the ship up for proper emergency energy management.


  [1]: http://en.memory-alpha.wikia.com/wiki/Navigational_deflector