Human Factors Facilitation Guide

Lesson 01: Human Tolerance and G-Force Limits

Teacher Resource

Pacing Overview

Hook & Slides 15 min
Stapp Case Study 30 min
Constraint Workshop 30 min
Total Time 75 min

Key Objectives

Analyze the relationship between \(\Delta t\) and peak force.
Identify physiological survival limits for humans.
Establish engineering design constraints for impact systems.

Instructional Script & Discussion

The Hook (Slides 1-2)

Open with the 18-G myth. Ask students: "If you were an engineer in 1945, why would you stop designing at 18 Gs?" Prompt them to think about the intersection of biological limits and mechanical design. Stapp's courage was not just physical, but scientific—he challenged the "consensus" through rigorous self-experimentation.

Physics Deep Dive (Slides 3-4)

Focus heavily on the formula \( F \cdot \Delta t = m \cdot \Delta v \). For engineering students, emphasize that momentum (\(m \cdot \Delta v\)) is usually a fixed design parameter (e.g., a car weighing 1500kg at 60mph). The only variables they can manipulate are \(F\) and \(\Delta t\).

"We can't change the car's weight or its speed once the collision has started. We only control how long it takes to stop."

Case Study Facilitation

During the worksheet, watch for students confusing Average Force with Peak Force. In a real crash, the force-time curve is rarely a rectangle; it's usually a bell curve or a jagged multi-peak curve. Explain that our calculations for average force represent the "ideal" flat curve they are aiming for.

Common Engineering Misconceptions

Misconception #1

"G-force is just gravity."

Clarify that 'G' is a unit of acceleration, not a force. We use it to compare non-gravitational accelerations to Earth's standard gravity. \(1G = 9.81 m/s^2\).

Misconception #2

"Harder materials are better for safety."

Students often equate strength with safety. Explain that high stiffness (Young's Modulus) actually leads to shorter impact times and higher peak forces. We want controlled failure.

// QUICK CHECK QUESTIONS

1. If we double the stop distance, what happens to the average force?

-> It is halved (assuming constant deceleration).

2. Why did Stapp survive 46 Gs but a typical fall is fatal?

-> Direction of force (transverse vs. longitudinal) and surface area distribution (harnessing).

3. What is the Factor of Safety (FoS) used for?

-> To account for uncertainties in material behavior and physiological variance.

Preparation Checklist

Materials for Students

Stapp Rocket Sled Case Study (Printed)

Engineering Notebooks / Graph Paper

Scientific Calculators

Teacher Prep

Load Stapp YouTube footage (optional, use for hook)

Review SI/HIC safety standards for background

Instructor Technical Brief: Severity Index (SI)

The Severity Index is calculated using the integral \( \int a^{2.5} dt \). This emphasizes that acceleration is not just linear in its damage profile—doubling the Gs results in nearly 6 times more physiological damage. This is why "flattening the curve" is the primary goal of impact engineering. The flatter the curve, the lower the SI for the same total impulse.

Impact Attenuation Engineering

Human Tolerance and G-Force Limits

Materials Science of Impact Damping

Designing Crumple Zones

Prototyping and Impact Testing

Design Review and Optimization

Stapp Rocket Sled Case Study

G-Force Limits Slides

Human Factors Teacher Guide

Damping Materials Slides

Material Energy Lab Guide

Impact Material Reference Sheet

Crumple Zone Physics Slides

Deformation Math Worksheet

Blueprint Drafting Template

Testing Telemetry Slides

Impact Test Data Log

Optimization Review Slides

Design Iteration Report

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