The Vostok spacecraft utilized an ejector seat to bail out the cosmonaut in the event of a low-altitude launch failure, as well as during reentry, however it would probably have been ineffective in the first 20 seconds after liftoff when the altitude would be too low for the parachute to deploy. Inspired by the Mercury LES, Soviet designers began work on a similar system in 1962. This included developing a complex sensing system to monitor various launch vehicle parameters and trigger an abort if a booster malfunction occurred. Based on data from R-7 launches over the years, engineers developed a list of the most likely failure modes for the vehicle and could narrow down abort conditions to premature separation of a strap-on booster, low engine thrust, loss of combustion chamber pressure, or loss of booster guidance. The Spacecraft Abort System (SAS; ) could also be manually activated from the ground, but unlike American spacecraft, there was no way for the cosmonauts to trigger it themselves.