5.9 KiB
| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Saturn V | 8/10 | https://en.wikipedia.org/wiki/Saturn_V | reference | science, encyclopedia | 2026-05-05T13:12:08.190587+00:00 | kb-cron |
=== Startup sequence === At T−8 minutes, the onboard computer, the Launch Vehicle Digital Computer (LVDC), was armed. At T−5 minutes 45 seconds, the final Go/No-Go was given from the launch controllers. At T−4 minutes 30 seconds, the Terminal Countdown Sequencer (TCS) was armed and prepared to execute the countdown sequence automatically. At T−3 minutes 7 seconds, the TCS began the automatic countdown sequence. At T−16.97 seconds, the TCS sent a signal to the LVDC giving it access to the internal gyroscopes and accelerometers. At T−8.9 seconds, the first-stage ignition sequence was initiated, with the center engine being ignited first, followed by opposing outboard pairs at 300-millisecond intervals to reduce the structural loads on the rocket. At T+0.3 seconds, the rocket was "soft released" in two stages. First, the hold-down arms released the rocket. Second, as the rocket began to accelerate upwards, it was slowed by tapered metal pins being pulled through holes for half a second. At T+0.63 seconds, the IU umbilical cable was disconnected, indicating to the LVDC that launch had occurred. At about T+1.7 seconds, the vehicle yawed 1.25° away from the launch tower to ensure adequate clearance despite winds. It took about 10 seconds for the rocket to clear the tower; this varied between missions. At an altitude of 140 m (450 ft) the rocket rolled to the correct flight azimuth, which varied from 72 to 108 degrees depending on the time and date of launch. At T+20.6 seconds, the four outboard engines were tilted outward, in case of a premature outboard engine shutdown. At around T+1 minute, the Saturn V reached the speed of sound.
=== Max Q sequence === At about T+1 minute 6 seconds, the rocket experienced maximum dynamic pressure (max q). Dynamic pressure on a rocket varies with air density and relative velocity. Although velocity continues to increase, air density decreases so quickly with altitude that dynamic pressure falls below max q. As the Saturn V consumed fuel, its weight decreased, increasing its acceleration. This caused the crew to experience 4 g at T+2 minutes 15 seconds. To reduce the g forces, the center engine was cut, lowering the g forces to 3 g. Each F-1 engine consumed 900,000 kg/min (16.5 short ton/s). At this time, the Saturn V had an altitude of 44.1 km (23.8 nmi), weighted 1,110,000 kg (2,450,000 lb), and had a speed of 7,124.4 km/h; 4,426.9 mph (6,492.8 ft/s) When the optical depletion sensors detected low fuel or oxidizer, the remaining four outboard engines were shut down. This would happen around T+2 minutes 40 seconds. The Saturn V had an altitude of 66.1 km (35.7 nmi), weighed 830,000 kg (1,820,000 lb), and had a speed of 9,950.8 km/h; 6,183.1 mph (9,068.6 ft/s) Just before first stage separation, on earlier Apollo missions, small ullage engines on the second stage were ignited for a few seconds to ensure the fuels were at the bottom of their tanks. First stage separation occurred less than one second after the engines were cut off. Eight small solid-fuel separation motors separated the S-IC from the rest of the vehicle. The first stage would continue on a ballistic trajectory for another minute and 45 seconds before falling into the Atlantic Ocean about 560 km (350 mi) downrange.
=== S-II sequence === After S-IC separation, the five J-2 engines were ignited and began providing thrust. It took a couple of seconds for the J-2 engines to reach full thrust. At about T+3 minutes 12 seconds, the interstage ring dropped from the second stage. The ring, sitting only a 1 m (3.3 ft) from the outboard J-2 engines, needed to fall cleanly without hitting them, as it could have potentially damaged the engines. Shortly after interstage separation, the Launch Escape System was also jettisoned. At about T+3 minutes 24 seconds, the Saturn V switched from a pre-programmed trajectory to a "closed loop," or Iterative Guidance Mode. The pre-programmed trajectory was designed to keep the vehicle on its course but prioritized making sure that the aerodynamic forces on the Saturn V did not exceed its limits. The instrument unit computed in real time the most fuel-efficient trajectory toward its target orbit. If the instrument unit failed, the crew could switch control of the Saturn to the command module's computer, take manual control, or abort the flight. At about T+7 minutes 40 seconds, the center engine shut down to reduce longitudinal pogo oscillations. Five level sensors in the bottom of each S-II propellant tank were armed during S-II flight, allowing any two to trigger S-II cutoff and staging when uncovered. At about T+9 minutes 8 seconds, the rest of the J-2 engines shut off and the process of separating the S-II from the S-IVB began. At this time, the Saturn V had an altitude of 187.2 km (101.1 nmi) and had a speed of 24,897.9 km/h; 15,470.9 mph (22,690.6 ft/s). Two small ullage engines were ignited and retro motors were fired, separating the S-II from the rest of the rocket.
=== S-IVB sequence ===
Unlike the two-plane separation of the S-IC and S-II stages, the S-II and S-IVB separated with a single step. Less than one second after the S-II's engines were cut off, the S-IVB's single J-2 engine was ignited, taking about 5 seconds to reach full thrust. The third stage burned for about 2.5 minutes until first cutoff at about T+11 minutes 40 seconds. The vehicle had an altitude of 191.1 km (103.2 nmi) and had a speed of 28,048 km/h; 17,428 mph (25,561 ft/s). Unlike the previous two stages, S-IVB's J-2 engine was restarted for trans-lunar injection (TLI). After engine cutoff, the Saturn V entered an Earth parking orbit 190 km (100 nmi) above the Earth. The third stage remained attached to the spacecraft while it orbited the Earth one and a half times.