Lesson 8 of 9

🔧 Integration & Verification

🎯 Grades 9–12 ⏱ ~30 minutes 🟡 Intermediate

What You'll Learn

The difference between verification (did we build it right?) and validation (did we build the right thing?)
Integration strategies: big-bang, incremental, and continuous integration
How Technical Readiness Levels (TRL) measure maturity of systems

Verification vs. Validation

Verification: "Did we build it right?" — checking that the system conforms to its specifications. A verification question: "Does the braking system stop the car in <150 ft from 60 mph?" (checked by test)

Validation: "Did we build the right thing?" — confirming the system actually meets the stakeholder's needs in real use. A validation question: "Does the car meet drivers' safety expectations in real-world conditions?"

You can build exactly what the specs say and still fail validation if the specs didn't capture the real need correctly.

Integration Strategies

Big-bang integration: Build all components, integrate them all at once. Simple but when it fails, hard to diagnose which interface is broken.
Incremental integration: Integrate components one by one, testing after each addition. Makes it easier to isolate failures.
Continuous integration (CI): Software teams merge and test code multiple times per day. Automated tests run on every change. Catches regressions immediately.

Technology Readiness Levels (TRL)

The TRL scale (1–9), developed by NASA, measures the maturity of a technology:

TRL 1–3: Basic research and proof of concept
TRL 4–6: Lab and prototype validation
TRL 7–9: Operational demonstration and deployment

Government and defense contracts often require TRL 6+ before funding production. NASA requires TRL 6 before a technology can fly on a spacecraft.

🛰

The Mars Climate Orbiter Validation Failure

In 1999, NASA's Mars Climate Orbiter was lost because one team used metric units (newton-seconds) while another used imperial units (pound-force-seconds) for thruster data. The spacecraft passed all its verification tests — it was built exactly to specification. But the specification itself was wrong. This is a validation failure. Cost: $327.6 million. The lesson: verify that specifications correctly capture the actual operational need.

Quick Check

1. What does "verification" mean in systems engineering?

ADid we build the right thing for the user?

BDid we build it according to the specifications?

CDid we complete the project on time?

DDid we test all failure modes?

2. Compared to big-bang integration, incremental integration is better because:

AIt requires less total testing

BInterface failures are easier to isolate when adding one component at a time

CAll components are completed before any testing begins

DIt eliminates the need for unit testing

3. At what TRL level does NASA require a technology before it can fly on a spacecraft?

ATRL 3

BTRL 4

CTRL 6

DTRL 9

4. The Mars Climate Orbiter failure (metric vs. imperial units) was primarily a:

AVerification failure — the system was not built to specification

BValidation failure — the specification was wrong, not capturing the actual need

CIntegration failure — components were assembled incorrectly

DReliability failure — a component stopped working

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