Simple and robust

The Soviet space program's physics was the same, but their implementation differed from the US's

The launcher used by Russia today appears almost identical to the original R7 and is imbued with Soviet design simplicity. Not least its ignition system.

With five rocket motors and 20 combustion chambers, as well as 12 smaller engines used for steering, it’s essential that all the engines light at the same time. If not, fuel could pour out of an unlit engine and cause a potentially catastrophic explosion.

This synchronicity is achieved by using giant matches. Once the Soyuz is on its launch gantry, engineers place sticks of birch wood with two pyrotechnic electric ignitors on the end into the rocket nozzles. These are bound together with brass wire.

Just before launch, the ignitors fire and the flame burns through the wire. When all the wires are severed it indicates that there is a burning flame within each nozzle and it’s safe to open the propellent valves. The system ensures that fuel is only released when these giant matches are all lit.