Tuesday, February 13, 2018

Launch Velocity of Third Stage for Orbital Launch

Multistage rockets are the only practical way to put objects into orbit because the weight of carrying empty tanks limits velocity.  What is the velocity of an orbital insertion rocket when stages 2 and 3 separate?   You would think this would be easy to find.


  1. Single stage to orbit was achieved in 1957.


    SpaceX Falcon 9 is a two stage rocket. The 1st stage is dropped around 6000-9000 km/h depending on the required final velocity.

    The main reason the Saturn V was a 3 stage rocket was the need to perform the TLI burn. It dropped its first stage when it reached 4,330 mph, about 7000 km/h.

  2. From "Apollo 11 Lunar Landing Mission Press Kit":

    "The 7.6-million-pound thrust Saturn V first stage boosts the space vehicle to an altitude of 36.3 nm at 50.6 nm downrange and increases the vehicle's velocity to 9030.6 fps in 2 minutes and 40.8 seconds of powered flight. ..."

    "The 1-million-pound of thrust second stage (S_II) carries the space vehicle to an altitude of 101.4 nm and a distance of 885 nm downrange. Before burnout, the vehicle will be moving at a speed of 22,746.8 fps. ..."

    "Velocity at Earth orbital insertion will be 25,567 fps ..."

    (From the days when sliderules ruled!)

    At ignition, the missile weighed 6,484,280 lbs; at lift off 6,398,535 lbs. (That's right - it burned nearly 86,000 pounds of fuel and oxidizer in those few seconds while it was on the pad prior to lift off.)

    Only 299,562 pounds made it to orbit. Staging was necessary to shed the deadweight from the first and second stages (288,750 and 79,918 lbs. respectively) plus several thousand additional pounds for the interstages.

    Less than 5% of the starting weight made it to orbit. And less than 13,000 lbs (just 0.2%) made the round trip.