Preparing Apollo 11: “Ordnance”

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Mobile Service Structure Rollback (CDDT) Apollo 11. Retro Space Images/NASA.
Mobile Service Structure Rollback (CDDT) Apollo 11. Retro Space Images/NASA.

The first day of the countdown of the Saturn V launch vehicle involved the installation of ordnance, explosives in the form of pyrotechnics on the spacecraft and ordnance on the launch vehicle. In fact, the original description for the Mobile Service Structure was the “arming tower,” as it allowed access to the vehicle for the ordnance installation. For safety these explosives were not installed or their initiators were not installed until the start of the countdown.

On the Saturn V, these included engine start materials for the F-1 engines, which involved high voltage ignitors, hypergolic cartridges, along with pyrogen initiators for the first stage retrorockets. During the installation of these items, the lower levels were cleared for safety. Common practice included the recording of relevant pad television cameras during the ordnance installation process. In addition, radio-frequency silence was maintained during the handling of ordnance.

After the first stage ordnance was installed, separation ordnance was installed, and the process continued up the vehicle, including initiators for pyrotechnics on the spacecraft. The operation also included final hookup of the launch vehicle destruct packages.

The complete Apollo/Saturn V stack contained an array of ordnance, with over 210 devices, ranging in application from LES separation, SLA separation, LM systems pressurization, and parachute deployment.

Ordnance on the first stage, in addition to the engine start hypergolics and ignitors, featured the stage propellant dispersion explosives, or “range safety destruct” system. The explosives were contained along the sides of the stage in the systems tunnels. In the event of range safety destruction they would split the stage open to disperse the propellants as widely as possible.

Saturn V S-IC Propellant Dispersal System. From the Saturn V Flight Manual/NASA.
Saturn V S-IC Propellant Dispersal System. From the Saturn V Flight Manual/NASA.

The S-IC first stage also contained retrorockets under the fin fairings. A portion of the forward fin fairing was blown off when the retrorockets fired.

Saturn V S-IC Retrorockets. From the Saturn V Flight Manual/NASA.
Saturn V S-IC Retrorockets. From the Saturn V Flight Manual/NASA.

Separation ordnance was featured in each of the Saturn V stages, and in the spacecraft, consisting of linear shaped charges at the separation point.

Saturn V stage separation ordnance installations. From the Saturn V Flight Manual/NASA.
Saturn V stage separation ordnance installations. From the Saturn V Flight Manual/NASA.

In the S-II second stage, ordnance included retro rockets and a separate propellant dispersion system:

Saturn V S-II Ullage and Retro Rockets. From the Saturn V Flight Manual/NASA.
Saturn V S-II Ullage and Retro Rockets. From the Saturn V Flight Manual/NASA.
Saturn V S-II Propellant Dispersion System. From the Saturn V Flight Manual/NASA.
Saturn V S-II Propellant Dispersion System. From the Saturn V Flight Manual/NASA.

Similar systems were contained in the S-IVB third stage:

Saturn V S-IVB ordnance installations. From the Saturn V Flight Manual/NASA.
Saturn V S-IVB ordnance installations. From the Saturn V Flight Manual/NASA.

Spacecraft pyrotechnics were installed on the SLA, the lunar module, the command/service module, and in the launch escape system.

Saturn V Apollo Spacecraft Pyrotechnic Installations. From the Apollo Experience Report - Spacecraft Pyrotechnic Systems, March 1973. NASA.
Saturn V Apollo Spacecraft Pyrotechnic Installations. From the Apollo Experience Report – Spacecraft Pyrotechnic Systems, March 1973. NASA.

After the ordnance operations were complete, work proceeded to the loading of spacecraft consumables, such as hypergolic fuels and gaseous consumables, such as oxygen and helium. In the next installment of Preparing Apollo 11: We’ll look that that next phase of the countdown – the loading of spacecraft consumables.

Sources and further reading:

The Saturn V Flight Manual/NASA

Apollo Spacecraft & Saturn V Launch Vehicle Pyrotechnics/Explosive Devices (an excellent descriptive presentation of how the devices operated on the launch vehicle and spacecraft)

Apollo Experience Report – Spacecraft Pyrotechnic Systems, March 1973.

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