Abstract: On the non-powder two-stage light gas gun facilities, high-velocity impact experiments were carried out to analyze the effects of bumper lateral size on the damage to Whipple shield and explore the feasibility of using bumper whose size is smaller than that of rear wall on Whipple shield in high-velocity impact tests. The configuration of Whipple shields consisted of 1-mm-thickness bumpers and 3-mm-thickness rear wall with 10-cm space between the bumper and the rear wall. The bumpers were 2A12 aluminum square plates with different side lines such as 8, 12, 16 and 20 cm. The rear wall was 5A06 Aluminum square plate with 20-cm side lines. All tests were performed by shooting aluminum projectile 4 mm in diameter at the velocity ranging from 1.45 to 1.71 km/s. Test results show that the mean velocity of 6 projectiles impacting on the Whipple shields is independent of bumper size when the perforation percentage of rear wall was over 80. It is found that the diameters of perforation holes both in front and in back of bumper are independent of bumper size too. However, the deflection on the bumper surface is dependent on bumper size obviously.