If you’re on top of a launch tower and something goes wrong with your rocket, you’re going to want to get away pretty quickly.

With that in mind, Boeing and the United Launch Alliance (ULA) have unveiled their Emergency Egress System (EES), a zip line for astronauts to escape from a launch tower in the case of an emergency.

This is intended for upcoming launches of the Boeing CST-100 Starliner, which will fly atop an Atlas V rocket from Cape Canaveral’s Space Launch Complex 41 in Florida. Launches are scheduled to begin next year.

Four zip lines have been installed, which will take people from the top of the pad 52 meters (172 feet) up to a point on the ground 410 meters (1,340 feet) away in 30 seconds, at speeds of up to 64 km/h (40 mph). There will be 20 seats on the EES, which supports the crew of up to seven and any other personnel still on the launch tower.

^{Neow. Via YouTube/collectSpace}

The idea of using zip lines is not completely new. The Shuttle used a slide wire basket system, while Apollo had similar zip lines. None were ever used in an emergency, though. “The systems have never been needed in an emergency, but are required in case a condition develops before launch that prohibits those on the tower from taking the elevator down to safety,” NASA noted in a statement.

Boeing’s lines are equipped with specially designed seats that can hold astronauts in bulky spacesuits. Handles can be used to control the speed as well.

It should be noted this is different to a Launch Abort System, thrusters used to catapult the crew capsule rapidly away from the rocket in the case of a major emergency, like an impending explosion. The EES would be used in the minutes leading up to the launch.

Boeing is developing the Starliner alongside SpaceX’s Dragon capsule for use by NASA to transport astronauts to the International Space Station (ISS). Both are expected to fly for the first time next year without a crew, with crewed launches to follow.

But it’s good to know that, if an accident does occur prior to those manned launches, there’s an effective – and fun – way to get the crew to safety.