Rube Goldberg Rocketry: Triggering a Rocket Launch

Rube Goldberg cartoons “If the Soap Falls Out of the Bathtub, Try This …” and “Foolish Questions,” on page 10 of the Duluth Herald, November 18, 1921.

To illustrate the Triggering settings in the ObserVIEW software, we devised a clever Rube Goldbergesque rocket launch. While we were planning on launching a rocket for the purpose of collecting data, we also decided to devise a special trigger sequence to illustrate the ObserVR1000’s triggering capabilities.

Figure 1. “Rocketman” is ready for launch. It is tilted at a slight launch angle to compensate for the wind.

Trigger Sequence: Software Steps

Figure 2. Triggering option in the ObserVR1000 Settings.

You can add a triggering event(s) when recording data in an ObserVIEW session running the VR Mobile application.

1. To access the Triggering feature, point to the ObserVR1000 Settings and select the three-line menu icon > Triggering (Figure 2).
2. To create a new trigger, select the New Trigger button.
3. Select the trigger event and action(s).

Triggering Sequence: Physical Setup

To trigger the rocket’s launch, we designed a sequence of events and actions.

1. An individual struck a gong with a modal hammer (the gong’s sound did not trigger the launch, but did prepare the spectators for an imminent launch.) If the force that hit the gong exceeded 60F-lbs, it would trigger the next action.
2. The event (a force on the modal hammer greater than 60F-lbs) produced an action (turning on an ObserVR1000 digital output).
3. The digital output from the ObserVR1000 tripped a relay to complete an electrical circuit, which ignited the fuse of the rocket propellant engine.

Figure 3. The triggering sequence. An individual hit a gong with a modal hammer, the ObserVR1000’s digital output tripped the relay, and the electrical circuit was completed, igniting the fuse of the rocket propellant engine.

Triggering Sequence Executed

We conducted several launches to collect vibration data and test the ObserVR1000 triggering options. The following is a report on two of the launches for comparative purposes.

Launch Mission-C

The force hammer needed 60F-lbs to launch. Mission-C hammer hit with 103F-lbs, successfully triggering the launch (Figure 4).

Figure 4. Launch Mission-C.

0.32 sec after exceeding the 60F-lbs event criterion, the ignition of the rocket began with a force of 32.9G on the launch pad (Figure 5).

Figure 5. Launch Mission-C.

0.63 sec after exceeding the 60F-lbs event criterion, we observed the maximum launch forces of 763G (Figure 6).

Figure 6. Launch Mission-C.

Launch Mission-N

The first hit of the gong with a modal hammer only recorded 45.2F-lbs, which was not sufficient force to trigger the event sequence (Figure 7).

Figure 7. Launch Mission-N.

The second hit of the gong with a modal hammer recorded 154.7F-lbs, which was plenty sufficient to trigger the event sequence (Figure 8).

Figure 8. Launch Mission-N.

The ignition of the rocket propellant engine was 25.8G on the launch pad (Figure 9).

Figure 9. Launch Mission-N.

We witnessed the maximum launch forces on the launch pad at 905.7G (Figure 10).

Figure 10. Launch Mission-N.