Vernier thruster

A vernier thruster is a thruster used on a spacecraft for attitude control. It is a smaller thrust motor than main attitude control motors and is used for fine adjustments to the attitude or velocity of a spacecraft. A vernier rocket is a smaller rocket engine used for attitude control in conjunction with a larger spacecraft propulsion engine. Due to their weight and the extra plumbing required for their operation, vernier rockets are seldom used.[1] Vernier thrusters are used when spacecraft control requirements, such as maneuvering during docking with other spacecraft, dictate a wide range of different thrust levels for attitude or velocity control. Main attitude control thrusters are used for larger movements, verniers for minor adjustments.

As an alternative, larger thrusters which can fire for very short durations or pulses may be fitted instead.

The Space Shuttle's reaction control system had six vernier engines or thrusters.[2] During STS-130 commander Zamka and pilot Terry Virts used the space shuttle Endeavour's vernier thrusters to reboost the International Space Station to its correct altitude.

See also

References

  1. ^ "Rocket Control: Examples of Controls". NASA's Glenn Research Center. http://microgravity.grc.nasa.gov/education/rocket/rktcontrl.html. Retrieved December 30, 2011. 
  2. ^ "Reaction Control Systems". NASA Kennedy Spaceflight Center. unknown. http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-rcs.html. Retrieved 2011-10-03. "The flight crew can select primary or vernier RCS thrusters for attitude control in orbit. Normally, the vernier thrusters are selected for on-orbit attitude hold. ... The forward RCS has 14 primary and two vernier engines. The aft RCS has 12 primary and two vernier engines in each pod. The primary RCS engines provide 870 pounds of vacuum thrust each, and the vernier RCS engines provide 24 pounds of vacuum thrust each. The oxidizer-to-fuel ratio for each engine is 1.6-to-1. The nominal chamber pressure of the primary engines is 152 psia. For each vernier engine, it is 110 psia."