Model Rocketry
Stability, propulsion and recovery.
Course
How a rocket flies straight, what its motor does, and how it comes home safely. Builds on the site's Model Rocketry tutorial and a 3D stability mission.
Before you start
- School arithmetic
- Newton's three laws in words
Learning objectives
- Name the parts of a model rocket and the four forces in flight
- Explain why the centre of gravity must be ahead of the centre of pressure
- Describe the phases of a flight from lift-off to recovery
- State the safety rules that apply whenever a rocket is launched
By the end you can
- Can predict whether a rocket will fly straight from its CG and CP
- Knows the safety boundary: launches are supervised and motors are never made by students
Before you start
- Foundation level of this track
- Algebra and square roots
- Impulse and momentum
Learning objectives
- Estimate the CP with the Barrowman method
- Calculate the CG from component masses and positions
- Relate total impulse to motor classes and to apogee
- Check that stability survives a heavier motor or a damaged fin
By the end you can
- Can apply the Barrowman method and a CG calculation
- Can design for robustness rather than for one condition
Lesson plan
Lessons · Ages 14–16
Parts and forces
- Nose cone, body, fins, motor, recovery
- Thrust, weight, drag and lift
Stability
- Centre of gravity
- Centre of pressure
- Static margin in calibres
Flight phases
- Boost, coast, apogee
- Ejection and recovery
Safety
- Supervised launches only
- Safe distances and range rules
- Why students never make motors
Hands-on activities
- Find the balance point (CG) of a model or a pencil with an eraser on one end
- Cut a cardboard side profile of a rocket and find where it balances: a rough, conservative way to estimate the CP
- Play Design a Stable Model Rocket and explain your fin choice
Challenge: Design a Stable Model Rocket
Adjust nose, fins and ballast in the 3D mission until the rocket is stable but not overstable.
Pass criteria
- Static margin between 1.0 and 2.0 calibres
- Correct explanation of why the CG must lead the CP
Physics and mathematics
Show the 3 equations
W = m × g
W in N, m in kg, g = 9.81 m/s²
A 100 g rocket weighs about 1 newton.
T ÷ W > 1
no unit
Above 1 the rocket can lift off. Designers want much more, so it is moving fast enough for the fins to work when it leaves the launch rod.
SM = (X_cp − X_cg) ÷ d
calibres (body diameters)
Positive means stable. This lesson aims for 1 to 2 calibres.
3D models
- Model rocket with CG and CP markers and exploded view (available: Design a Stable Model Rocket)
- Rocket explorer (existing: Model Rocketry tutorial)
Lessons · Ages 17–18
Barrowman method
- Nose and fin normal-force coefficients
- Fin geometry: root, tip, span, sweep
- Limits: subsonic flight, small angles
Mass properties
- Component CG
- Ballast
- CG shift as propellant burns
Propulsion
- Thrust curves
- Total impulse and motor classes
- Thrust-to-weight
Flight simulation
- Drag and apogee
- Open-source simulators such as OpenRocket
- Comparing simulation with flight data
Hands-on activities
- Calculate CP by hand for one design with the Barrowman equations and compare with the mission's value
- Model the same rocket in an open-source flight simulator and compare apogee for two motor classes
- Write a one-page stability report with liftoff and burnout margins
Challenge: Robust Stability
Design a rocket that stays stable with the standard motor and with a heavier motor.
Pass criteria
- Static margin between 1.0 and 2.0 calibres with the standard motor
- Static margin of at least 1.0 calibre with the heavier motor
- Thrust-to-weight of at least 5 with the standard motor (this lesson's guideline)
Physics and mathematics
Show the 3 equations
X_cg = Σ(mᵢ × xᵢ) ÷ Σmᵢ
x in mm from the nose tip, m in g
The mass-weighted average position of every component.
C_Nf = [1 + R ÷ (S + R)] × 4N(S ÷ d)² ÷ [1 + √(1 + (2L_F ÷ (C_R + C_T))²)]
R body radius, S span, N fin count, L_F mid-chord length, C_R and C_T root and tip chords
How strongly the fins push back when the rocket tilts. More span or more fins moves the CP aft.
I = ∫F dt ≈ F_avg × t_burn
I in N·s
Each motor class letter allows up to twice the total impulse of the one before it.
3D models
- Parametric model rocket: fin count, span, sweep (available: Design a Stable Model Rocket)
- Liquid engine reference architecture (existing: Rocket Engine Digital Twin)
Classes and workshops
Online
Interactive 3D mission and tutorials now; live online classes planned.
In person
Model Rocketry workshop planned. Dates, venue, fees, eligibility and safety arrangements will be published for each workshop.
Existing tutorials for this track
- Model RocketryAerodynamics, stability, propulsion, recovery and flight analysis.
- Model Rocketry: flight physics and stability labMove the CG and CP and watch the static margin.
- 7-Day Model Rocketry Learning GuideAn independent day-by-day study companion; not an official IN-SPACe publication.
- Rocket Engine Digital TwinA reusable liquid rocket engine reference architecture.
Eligibility, independence and privacy
- Independent initiative. Space Academy is part of an independent ISHAVASYAM.ORG education initiative. It is not affiliated with, endorsed by, or run on behalf of ISRO, IN-SPACe, NSIL or the Department of Space.
- No competition eligibility. Learning here does not register anyone for, or make anyone eligible for, any national or international competition. Each competition's organisers set its rules and eligibility.
- Simulated and illustrative. Interactive missions use simplified models and simulated, illustrative values. They are labelled as such and are not flight data.
- Ages. Written for learners aged 14 to 18. Anyone may play the self-paced missions; enquiries from under-18s need a parent or guardian.
- Privacy. Missions never ask for a name, school, age or contact details. Progress is stored only in this browser and can be cleared at any time. This site uses Google Analytics to count page visits and mission steps. Some of the site's existing tutorials ask visitors to sign in with a Google account. If you are under 18, check with a parent or guardian before signing in.