Unlike the Solid Rocket Boosters, external tanks were not re-used. The Block 1 will use 5-segment solid rocket boosters producing of thrust at liftoff. The boost phase was four of the Nike Ajax boosters strapped together. In August 2018, the first tests of the solid rocket boosters were made. Each missile is launched by 4 solid-fueled strap-on rocket boosters. Up to nine strap-on solid rocket boosters (SRBs) could be fitted. One of the solid rocket boosters was hit by a door. Despite this, his parents declined the administration of subsequent tetanus boosters or other vaccinations. Stacking of the Solid Rocket Boosters (SRBs) began 9 September 1996. Stacking of the solid rocket boosters (SRB) began on 11 July 2008. These were in the aerospace fields of missiles and space boosters. Steel was used for the space shuttle boosters. Addition of strap-on boosters for heavier satellites would increase the price. All layouts of solid boosters are symmetrical. Previous flights had used zero, two, or three solid boosters, but never five.