# What objects can & can't penetrate ground based shield generators?

At the battle of Hoth - shields had to be lowered to allow a transport to leave.

However, apparently AT-AT's, which are large, were able to walk through them (unless they got inside the shields when the shields were lowered to let a transport leave - which isn't stated anywhere).

Battle droids walked through ground based shields at the Battle of Naboo.

Just what is the logic - is there a size limit? Can small ships penetrate shields? If so why don't we ever see that and why can't larger ships? If not - why can AT-AT's and droids?

using the gungans' shields as an example, the shields stop anything entering them that are moving faster then X speed. these are kinetic shields which is why the droids must walk into the shields before attacking. a ship leaving the atmosphere must reach a certain speed to break through and into space, which is why if their shield was similar to the gungans aka a kinetic shield that speed needed by the transport ships was to fast. to a kinetic shield size maters not, as long as its moving under the barrier threshold. From another post blasterspeed speculates that a blaster shot is moving at 150meters per second. that translates into around 350 miles per hour. so the kinetic barrier is at least stopping things moving that fast, however i would hazard to guess it is stopping things moving closer to 75 miles per hour, as thats one of the lowest speeds an airplane can fly out, hence preventing air vehicles from entering the shield. ( thats assuming a tie fighter can fly that slow i guess they could slowly fall into the shield as long as they were under the speed threshold however it would be difficult, plus all the rebel guns shooting you while you came to a halt. )

edit, after relooking at the blaster speed question, another person says they actualy are moving at 35 meters/second which is about 75 mile per hour, agreeing with my minimum flight speed.

• startrek and dune also use kinetic shields. its the most common type of sci-fi shield. Commented Dec 18, 2014 at 19:53
• Dune talks about the kinetic limits the most out of any scifi ive read, as it was something the characters had to learn to get around when fighting an opponent wearing a personal shield. the other shields are specifically energy shields that block X type of energy, such as the borgs personal shield as picard is able to bypass the energy shields using a tommy gun in first contact. Commented Dec 18, 2014 at 20:04
• I think at least in the (old) movie of Dune there was a kind of slow projektile that was used one time to bypass the shield to the surprise of the shield wearer. I would assume that the weapon industry of the star wars empire would have developed "slow bombs" to bombard targets under ground shields, too. So I think there must be more than just a speed limit. I'm not sure why, but my impression was, that the shield was not reaching the ground and following the terrain so the AT-AT and other ground forces were able to walk in under the shield border. Commented Dec 19, 2014 at 12:53
• @Hothie non of the dune movie were accurate. so you can discount about 90% of what you see in the movies lol. (their some of the worst book to movie adaptations) Commented Dec 19, 2014 at 14:09
• When ship takes off it is accelerating from 0 - so even if it can't fly slowly - it could just take off during acceleration through the shield. Basically it makes no sense. Commented Dec 19, 2014 at 20:30