Curriculum · Teacher companion
Atmospheric Requirements — teacher companion
Everything you need to run the tutorial with confidence: a full answer key, suggested timing, the misconceptions students hit most, discussion prompts and NGSS alignment.
Learning objectives
What students should walk away with
- 1.Convert between total pressure, partial pressure of oxygen, and percent oxygen.
- 2.Explain why a lower total pressure forces a higher percent oxygen to keep people healthy.
- 3.Describe how oxygen concentration — not just partial pressure — drives flammability.
- 4.Weigh the competing demands of human comfort, fire risk, cost and structure when choosing an atmosphere.
- 5.Estimate how much of each gas a settlement needs using Dalton’s Law, Amagat’s Law and expansion ratios.
NGSS alignment
Where it maps
This is a quantitative engineering-design task, so the strongest fits are the engineering-design performance expectations, plus the mathematics practice and the scale/quantity crosscutting concept.
- HS-ETS1-2
Design a solution to a complex real-world problem by breaking it down into smaller, more manageable problems that can be solved through engineering.
- HS-ETS1-3
Evaluate a solution to a complex real-world problem based on prioritized criteria and trade-offs that account for a range of constraints — including cost, safety and reliability.
- SEP-5
Using Mathematics and Computational Thinking — applying Dalton’s and Amagat’s laws to size a real system.
- CCC-3
Scale, Proportion, and Quantity — how percent oxygen changes with total pressure at fixed partial pressure.
Suggested timing
A 55–60 minute run
| Phase | Minutes | Notes |
|---|---|---|
| Hook & objectives | 5 | Frame the design problem: a settlement has to make its own air. |
| Part 1 — pressure & composition | 12 | Two worked examples, then the Pressure Explorer. |
| Part 2 & 3 — health and fire | 12 | Altitude, SP-413, the fire triangle and the trade-off table. |
| Part 4 — other air components | 6 | N₂, CO₂, water vapour cards; quick class discussion. |
| Part 5 — sizing calculator | 15 | Work the container problem together, then let pairs change inputs. |
| Check & wrap | 8 | Three self-check questions; surface reasoning as a class. |
Answer key
Worked answers
Example 1 — 700 mmHg total, 150 mmHg pO₂
150 ÷ 700 = 0.214 → 21.4% oxygen (essentially Earth-like).
Example 2 — 20% O₂ at 0.65 atm total
0.20 × 0.65 = 0.13 atm pO₂ (below Earth’s ~0.16 atm; mild altitude effects).
Q1 — 0.18 atm pO₂ at 0.60 atm total
0.18 ÷ 0.60 = 0.30 → 30% oxygen. Above Earth’s 21% because total pressure is lower.
Q2 — 21% O₂ at 0.50 atm total
0.21 × 0.50 = 0.105 atm pO₂.
Q3 — same pO₂, cabin A at 1.0 atm vs cabin B at 0.5 atm
Cabin B is more flammable: same pO₂ at half the pressure means double the oxygen fraction, and flammability tracks concentration.
Container problem — 1,000,000 m³, 0.75 atm, pO₂ 0.132 atm
Partial volumes: O₂ 176,000 m³, N₂ 824,000 m³. Adjusted expansion ratios (×0.75): O₂ 0.000872, N₂ 0.001078. Liquid: O₂ ≈ 153.5 m³, N₂ ≈ 887.9 m³ → ≈ 1.5 containers O₂ and 8.9 containers N₂.
Watch for
Common misconceptions
“Lower pressure means less oxygen, so it must be safer from fire.”
The opposite is usually true. To keep people healthy at lower total pressure you raise the oxygen fraction, and fire risk tracks that fraction — so low-pressure cabins are often more flammable, not less.
“Percent oxygen and partial pressure of oxygen are the same thing.”
They’re linked but distinct. pO₂ is what the lungs respond to; percent is pO₂ divided by total pressure. The same pO₂ can be 21% or 40% depending on total pressure.
“The original worksheet says 1.6 oxygen containers, so that’s the answer.”
That figure is a rounding artefact. The calculation gives ≈153.5 m³ of liquid oxygen, or ≈1.5 containers. This rebuild corrects it — a good moment to discuss significant figures.
“Air is basically just oxygen.”
Oxygen is only ~21% of Earth’s air. Nitrogen (an inert safety buffer and biological necessity), CO₂ and water vapour all matter to people, plants, electronics and structures.
Take it further
Discussion prompts
- If shipping gas from Earth is expensive, what’s the argument for a lower total pressure — and what’s the cost of that choice?
- Apollo 1 used pure oxygen for engineering convenience. What trade-off were they making, and what changed afterward?
- Where else on the settlement (labs, workshops, agriculture) might a different atmosphere be justified?
- The maths assumes ideal gas behaviour. When would that assumption break down, and how would you check it?
Download the lesson pack
A ready-to-run lesson plan and slide deck accompany this tutorial. Get the full Space Design Challenge material for your classroom.