Count Until a Staff Member Posts! (394)

[Brisky]

34

Acceleration increased during S-IC flight for three reasons. One, increased acceleration increased the propellant pressure at the engines, increasing the flow rate somewhat. This was the least important factor, though this feedback effect often led to an undesirable thrust oscillation called pogo. Two, as it climbed into thinner air F-1 engine efficiency increased significantly, a property of all rockets. The combined thrust of five engines on the pad was about 7.5 million pounds, reaching nearly 9 million pounds at altitude. But the biggest contribution by far was the rocket's rapidly decreasing mass. The propellant in just the S-IC made up about three-quarters of Saturn V's entire launch mass, and it was furiously consumed at over 13 metric tonnes per second. Newton's second law states that force is equal to mass times acceleration, or equivalently that acceleration is equal to force divided by mass, so as the mass decreased (and the force increased somewhat), acceleration rose. Including gravity, launch acceleration was only 1¼ g, i.e., the astronauts felt 1¼ g while the rocket accelerated vertically at ¼ g. As the rocket rapidly lost mass, total acceleration including gravity increased to nearly 4 g at T+135 seconds. At this point, the inboard (center) engine was shut down to prevent acceleration from increasing beyond 4 g.

When oxidizer or fuel depletion was sensed in the suction assemblies, the remaining four outboard engines were shut down. First stage separation occurred a little less than one second after this to allow for F-1 thrust tail-off. Eight small solid fuel separation motors backed the S-IC from the rest of the vehicle at an altitude of about 36 nautical miles (67 km). The first stage continued ballistically to an altitude of about 59 nautical miles (109 km) and then fell in the Atlantic Ocean about 300 nautical miles (560 km) downrange.

The engine shutdown procedure was changed for the launch of Skylab to avoid damage to the Apollo Telescope Mount. Rather than shutting down all four outboard engines at once, they were shut down two at a time with a delay to reduce peak acceleration further.

[Aveq]

35


hallo once more, yes

[Bricket]

36
the bricket train it is

[Emtile]

37

Does it go fast?

[Bricket]

38
it doesn't stop, that's for sure

[Brisky]

39

After S-IC separation, the S-II second stage burned for 6 minutes and propelled the craft to 109 miles (175 km) and 15,647 mph (6,995 m/s), close to orbital velocity.

For the first two unmanned launches, eight solid-fuel ullage motors ignited for four seconds to give positive acceleration to the S-II stage, followed by start of the five J-2 engines. For the first seven manned Apollo missions only four ullage motors were used on the S-II, and they were eliminated completely for the final four launches. About 30 seconds after first stage separation, the interstage ring dropped from the second stage. This was done with an inertially fixed attitude so that the interstage, only 1 meter from the outboard J-2 engines, would fall cleanly without contacting them. Shortly after interstage separation the Launch Escape System was also jettisoned. See Apollo abort modes for more information about the various abort modes that could have been used during a launch.
Apollo 6 interstage falling away. The engine exhaust from the S-II stage glows as it impacts the interstage.

About 38 seconds after the second stage ignition the Saturn V switched from a preprogrammed trajectory to a "closed loop" or Iterative Guidance Mode. The Instrument Unit now 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.

About 90 seconds before the second stage cutoff, the center engine shut down to reduce longitudinal pogo oscillations. At around this time, the LOX flow rate decreased, changing the mix ratio of the two propellants, ensuring that there would be as little propellant as possible left in the tanks at the end of second stage flight. This was done at a predetermined delta-v.

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 they were uncovered. One second after the second stage cut off it separated and several seconds later the third stage ignited. Solid fuel retro-rockets mounted on the interstage at the top of the S-II fired to back it away from the S-IVB. The S-II impacted about 2,300 nautical miles (4,200 km) from the launch site.

On the Apollo 13 mission, the inboard engine suffered from major pogo oscillation, resulting in an early automatic cutoff. To ensure sufficient velocity was reached, the remaining four engines were kept active for longer than planned. A pogo suppressor was fitted to later Apollo missions to avoid this, though the early engine 5 cutoff remained to reduce g-forces.

[Aveq]

40


a round number.

[Bricket]

41
and trains that don't stop are neat

[Brisky]

41

Unlike the two-plane separation of the S-IC and S-II, the S-II and S-IVB stages separated with a single step. Although it was constructed as part of the third stage, the interstage remained attached to the second stage.

During Apollo 11, a typical lunar mission, the third stage burned for about 2.5 minutes until first cutoff at 11 minutes 40 seconds. At this point it was 1,430 nautical miles (2,650 km)  downrange and in a parking orbit at an altitude of 103.2 nautical miles (191.1 km)  and velocity of 17,432 mph (7,793 m/s). The third stage remained attached to the spacecraft while it orbited the Earth one and a half times while astronauts and mission controllers prepared for translunar injection (TLI).
Apollo 17 S-IVB rocket stage, shortly after transposition and docking with the Lunar Module

This parking orbit was quite low by Earth orbit standards, and it would have been short-lived due to aerodynamic drag. This was not a problem on a lunar mission because of the short stay in the parking orbit. The S-IVB also continued to thrust at a low level by venting gaseous hydrogen, to keep propellants settled in their tanks and prevent gaseous cavities from forming in propellant feed lines. This venting also maintained safe pressures as liquid hydrogen boiled off in the fuel tank. This venting thrust easily exceeded aerodynamic drag.

For the final three Apollo flights, the temporary parking orbit was even lower (approximately 93 nautical miles (172 km)), to increase payload for these missions. The Apollo 9 Earth orbit mission was launched into the nominal orbit consistent with Apollo 11, but the spacecraft were able to use their own engines to raise the perigee high enough to sustain the 10-day mission. The Skylab was launched into a quite different orbit, with a 234-nautical-mile (434 km) perigee which sustained it for six years, and also a higher inclination to the equator (50 degrees versus 32.5 degrees for Apollo).

On Apollo 11, TLI came at 2 hours and 44 minutes after launch. The S-IVB burned for almost six minutes giving the spacecraft a velocity close to the Earth's escape velocity of 25,053 mph (11,200 m/s). This gave an energy-efficient transfer to lunar orbit, with the Moon helping to capture the spacecraft with a minimum of CSM fuel consumption.

About 40 minutes after TLI the Apollo Command Service Module (CSM) separated from the third stage, turned 180 degrees and docked with the Lunar Module (LM) that rode below the CSM during launch. The CSM and LM separated from the spent third stage 50 minutes later. This process is known as Transposition, docking, and extraction.

If it were to remain on the same trajectory as the spacecraft, the S-IVB could have presented a collision hazard so its remaining propellants were vented and the auxiliary propulsion system fired to move it away. For lunar missions before Apollo 13, the S-IVB was directed toward the Moon's trailing edge in its orbit so that the moon would slingshot it beyond earth escape velocity and into solar orbit. From Apollo 13 onwards, controllers directed the S-IVB to hit the Moon.[44] Seismometers left behind by previous missions detected the impacts, and the information helped map the interior structure of the Moon.

On September 3, 2002, astronomer Bill Yeung discovered a suspected asteroid, which was given the discovery designation J002E3. It appeared to be in orbit around the Earth, and was soon discovered from spectral analysis to be covered in white titanium dioxide, which was a major constituent of the paint used on the Saturn V. Calculation of orbital parameters led to tentative identification as being the Apollo 12 S-IVB stage.[45] Mission controllers had planned to send Apollo 12's S-IVB into solar orbit after separating from the Apollo spacecraft, but it is believed the burn lasted too long, and hence did not send it close enough to the Moon, remaining in a barely stable orbit around the Earth and Moon. In 1971, through a series of gravitational perturbations, it is believed to have entered in a solar orbit and then returned into weakly captured Earth orbit 31 years later. It left Earth orbit again in June 2003.[46]

[Aveq]

43


watch out for numbers

[Bricket]

44
so, any one any other words to say?

[Brisky]

45

Terugvallende...

In 1965, the Apollo Applications Program (AAP) was created to look into science missions that could be performed using Apollo hardware. Much of the planning centered on the idea of a space station. Wernher von Braun's earlier (1964) plans employed a "wet workshop" concept, with a spent S-II Saturn V second stage being launched into orbit and outfitted in space. The next year AAP studied a smaller station using an S-IVB Saturn 1B second stage. By 1969, Apollo funding cuts eliminated the possibility of procuring more Apollo hardware, and in fact forced the cancellation of some later Moon landing flights. This freed up at least one Saturn V, allowing the wet workshop to be replaced with the "dry workshop" concept: the station (now known as Skylab) would be built on the ground from a surplus Saturn IB second stage and launched atop the first two live stages of a Saturn V.[47] A backup station, constructed from a Saturn V third stage, was built and is now on display at the National Air and Space Museum.

Skylab was the only launch not directly related to the Apollo lunar landing program. The only significant changes to the Saturn V from the Apollo configurations involved some modification to the S-II to act as the terminal stage for inserting the Skylab payload into Earth orbit,[specify] and to vent excess propellant after engine cutoff so the spent stage would not rupture in orbit. The S-II remained in orbit for almost two years, and made an uncontrolled re-entry on January 11, 1975.[48]

Three crews lived aboard Skylab from May 25, 1973 to February 8, 1974, with Skylab remaining in orbit until July 11, 1979.

[Bricket]

46
Heh, anyway: it's gonna be fun as the vice-president of the greens

[Brisky]

47

Green is good, have a bonus!!!

After Apollo, the Saturn V was planned to be the prime launch vehicle for Prospector intended to land a 330-kilogram (730 lb) robotic rover on the Moon, similar to the Soviet Lunokhod,[49] and the Voyager Mars probes, as well a scaled-up version of the Voyager interplanetary probes.[50] It was also to have been the launch vehicle for the nuclear rocket stage RIFT test program and the later NERVA.[51] All of these planned uses of the Saturn V were cancelled, with cost being a major factor. Edgar Cortright, who had been director of NASA Langley, stated decades later that "JPL never liked the big approach. They always argued against it. I probably was the leading proponent in using the Saturn V, and I lost. Probably very wise that I lost."[50]

The canceled second production run of Saturn Vs would very likely have used the F-1A engine in its first stage, providing a substantial performance boost.[52] Other likely changes would have been the removal of the fins (which turned out to provide little benefit when compared to their weight); a stretched S-IC first stage to support the more powerful F-1As; and uprated J-2s or an M-1 for the upper stages.

A number of alternate Saturn vehicles were proposed based on the Saturn V, ranging from the Saturn INT-20 with an S-IVB stage and interstage mounted directly onto an S-IC stage, through to the Saturn V-23(L)[53] which would not only have five F-1 engines in the first stage, but also four strap-on boosters with two F-1 engines each: giving a total of thirteen F-1 engines firing at launch.

The Space Shuttle was initially conceived as a cargo transport to be used in concert with the Saturn V, even to the point that a Saturn-Shuttle was proposed, using the winged shuttle orbiter and external tank, but with the tank mounted on a modified, fly-back version of the S-IC. The first S-IC stage would be used to power the Shuttle during the first two minutes of flight, after which the S-IC would be jettisoned (which would then fly back to KSC for refurbishment) and the Space Shuttle Main Engines would then fire and place the orbiter into orbit. The Shuttle would handle space station logistics, while Saturn V would launch components. Lack of a second Saturn V production run killed this plan and has left the United States without a heavy-lift launch vehicle. Some in the U.S. space community have come to lament this situation,[54] as continued production would have allowed the International Space Station, using a Skylab or Mir configuration with both U.S. and Russian docking ports, to have been lifted with just a handful of launches. The Saturn-Shuttle concept also would have eliminated the Space Shuttle Solid Rocket Boosters that ultimately precipitated the Challenger accident in 1986.

[Bricket]

48
I mean, I was the vice president of the greens once during the flemish youth parliament