How are umbilical connectors held in place until their intended detachment?

Question

When a rocket is on its launch pad, umbilicals allow the flow of liquids, gases, electric power, and signals to the spacecraft. The umbilical is detached from the spacecraft at or before launch, to allow the craft to move unimpeded.

What mechanisms are used to hold umbilicals in place, so they do not detach prematurely?

If your answer is specific to a particular spacecraft, please specify it. Although this question is principally about umbilicals used for launch, their use between sections of a spacecraft may also be addressed.

Speculated possible answers:

• Friction is sufficient to hold the umbilical in place
• A spring-loaded or detent mechanism is overcome with the force of the launch
• Explosive bolts
• They are screwed-on
• A locking mechanism that must be actively released by electrical/pneumatic/hydraulic power
• Don't worry about it (doubtful)
• Just let the force of the launch tear through the pipes and wires (doubtful!)

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Answer 1

This paper surveys a large number of umbilical designs.

For the mechanical connections to the vehicle, it lists two types of detachable locking devices.

The type of locking mechanism used in this application is shown in Figure 16. This system is a simple ball and socket type of locking device where a sleeve captures multiple balls around the ball connection. This system, used in the Saturn program, can be remotely disengaged by pneumatic actuation as well as a mechanical device.

A second type of locking mechanism used for locking/release is the collet. This type of device uses a pin to radially expand fingers that are captured by the flight side receptacle (Figure 17). During disengagement, the pin is pulled, releasing the fingers from the receptacle. For conditions where the pin is jammed, a secondary system provides additional force for release. As a third option the vehicle receptacle can have a shear pin designed to fail at a given load. This design has been used extensively on current vehicles.

The paper lists Shuttle and Atlas V as users of the collet mechanism.

This image labels one of the collet connections at the top of the shuttle port side (LH2) T-0 umbilical, and shows both the vehicle and ground side plates.

This personal photo shows the complete starboard side (LO2) T-0 umbilical so that you can clearly see there are two collect connections at the top (right side in this picture since the vehicle was sitting on its gear).