The Saturn V - Apollo   performance characteristics

During the asscent phase until orbit insertion the flight performance parameters mentioned below are relevant to be monitored in time and should not exceed upper or lower limits during flight.
  1. Downrange distance
  2. Altitude
  3. Pitch angle
  4. Angle of attack
  5. Velocity
  6. Flight path angle
  7. Aerodynamic pressure
  8. Axiale force
  9. Acceleration
  10. Thrust
On a plot board or display a real time Altitude vs. Downrange plot and a Flight path angle vs. Velocity plot are shown to be able to detect actual flight trajectory deviations from the predicted nominal flight trajectory and ascertain that these deviations do not exceed abort limits.

This picture shows the flight path of the SA-503 (Apollo 8) during ascent.

This picture shows a set of flight characteristics of the SA-506 (Apollo 11) from lift-off to orbit insertion. The mass of the whole Saturn V stack is expressed in payload mass. The payload mass is the combined mass of the command module, the service module, the lunar module and the spacecraft lunar module adapter, which is around 47 metric tons (around 1.6 % of the launch mass).

The red plot shows a dramatically large rate of propellant consumption in the first 2½ minutes of the flight. At the moment of S-IC stage burn-out, the Saturn V has already lost around 78% of its launch mass.

The expression "MR shift" stands for "Mixture Ratio shift". It is referring to an automated procedure to change the ratio between the amount of fuel and amount of oxidizer which are supplied to the thrust engines of the S-II stage. The objective of this procedure is to optimize the performance of the S-II stage by depleting the propellants during flight as much as possible, to keep the mass of the launch vehicle at stage burn out as low as possible.

The blue plot representing the acceleration during flight helps us to imagine what the crew must have felt during ascent. In the first minute of the flight the acceleration was slowly building up. But the sudden drop of acceleration at S-IC stage burn-out (from 4 G's to weightlessness within a second) must have been quite an experience. About 1 second after S-IC stage separation, the second stage J-2 engines kicked in. All five J-2 engines were building up thrust in the next two seconds. The astronauts were gently pushed back in their couches when the acceleration went from zero to 1 G.

This picture shows a set of other flight characteristics of the SA-506 (Apollo 11) from lift-off to orbit insertion. Also is shown which abort procedures have to be used in time during ascent in case of emergencies.

Aerodynamic pressure (Q) is depending on the velocity and the air density. Q is zero when the velocity is zero at the moment of lift-off and is also zero when the air density is zero. This implies that during ascent there is a moment when Q has a maximum value. This Max. Q is attained at around 95 seconds into the flight at an altitude of 14 kilometers.

For the ascent phase from lift-off to orbit insertion, abort procedures have been devised to return the flight crew safely to Earth in case of emergency. The requirements for an abort procedure however, are much related to the velocity of the launch vehicle and its altitude.
Therefore three flight regimes have been distinguished:
- atmospheric flight;
- transitional or sub-orbital flight;
- and space flight.
There is an abort procedure for each flight regime. The objective of all these three abort procedures is to attain a quick return of the flight crew to Earth. Each procedure also requires a different mode of operation with regard to the spacecraft, to onboard software for event sequencing and guidance, to ground based stations and to Mission Control. There is however a fourth abort mode which is meant to attain a contigency orbit. This mode provides more options in selecting landing area's and, if possible, to meet some of the mission objectives.

Short description of the four abort modes:
Mode IA: From launch pad until 42 sec. after Lift-Off: LES propels CM to a safe distance from the exploding launch vehicle. The pitch control motor in the top of the LES is used to push the CM downrange, off the coast, into the Atlantic Ocean.

Mode IB: 42 sec. up to 30 km altitude: Same as Mode IA. The launch vehicle has cleared the beach after 42 seconds. After sepration from the launch vehicle a canard system in the top of the LES is used to induce a pitch tumble to put the CM in the proper attitude for parachute deployment.

Mode IC: From 30 km altitude up to 3 min. after Lift-Off: The LES is used to seprate the CM. After jettison of the LES, the CM is put in a proper reentry attitude with its RCS.

Mode II: Service Module RCS engines or SM main engine propel CM away from the launch vehicle. When the CSM is at safe distance, the CM is separated from the SM and manoeuvred into a reentry attitude.

Mode III: Service Module RCS engines or SM main engine propel CM away from the launch vehicle. Then the SM main engine is used to slow down the CSM and to manoeuvre it into an reentry attitude.

Mode IV: Service Module main engine is used to separate the CSM from the launch vehicle and insert the CSM into an orbit.

S-IVB to COI: The S-IVB stage is used to bring the CSM into an orbit (Contingency Orbit Insertion).
This ablity to attain a contingency orbit should actually not be considered as an abort mode but as a comfortable option which becomes available halfway the ascent.

Apollo 8 ground track during the Boost Phase (Ascent)

This picture shows the ground track of the SA-503 (Apollo 8) during ascent.
The S-IC performed its task in only the first 2½ minutes of the flight and was then disposed of. The S-IC stage plunged into the Atlantic Ocean about 655 km off the east coast of Florida.
The S-II provided thrust for about 6 minutes and was then separated. After a 10 minutes ballistic flight, the S-II stage plunged into the Atlantic Ocean about 4200 km off the east coast of Florida.
The S-IVB burned its J-2 thrust engine for about 5 min. to insert itself with the Apollo spacecraft on top into an 185 km high parking orbit. The S-IVB was re-ignited after about one revolution to propel the spacecraft into a trajectory to the Moon.

Apollo 8 ground track during Ascent, Earth Parking Orbit,
Trans Lunar Injection Burn and Trans Lunar Coast

This picture shows the ground track of the SA-503 (Apollo 8) during the first 3 hours into the flight: from lift-off until Trans Lunar Injection.
The S-IVB provided thrust at two moments:
A first 2½ min burn, which was the last burn in the boost phase and was meant to obtain a parking orbit around Earth.
And a second 5 minutes burn 2 hours and 50 min. into the flight for trans lunar injection.
After the Apollo spacecraft had been separated from the S-IVB stage, the S-IVB was sent into an orbit around the Sun.


Copyright 2005, 2009 by   Sander Panhuyzen
Comments and questions are welcome. All pictures and drawings contained on and through these pages are the author's, unless otherwise noted. No unauthorized reproduction without permission.