How to Build a CubeSat: A Complete Beginner’s Guide
A CubeSat is a small, standardised satellite built up from 10 cm cubic units (“U”). A single 1U CubeSat is a 10×10×10 cm cube of roughly 1–1.3 kg; larger missions stack these into 2U, 3U, 6U and 12U form factors. Because the mechanical interface and deployment method are standardised, CubeSats are dramatically cheaper and faster to build than traditional satellites — which is exactly why universities, startups and hobbyists can now fly real space missions.
This guide walks through the whole process end to end: choosing a mission, picking a form factor, designing each subsystem, balancing your budgets, testing, and getting to launch.
1. Start with the mission, not the hardware
Every good CubeSat starts with one clear question: what is it for? Earth observation, technology demonstration, amateur radio relay, space-weather measurement, biology experiments and deorbit-technology tests are all common first missions. Your mission drives every later decision — the payload, the orbit, how much power and data you need, and how big the satellite has to be.
Write a single sentence describing your mission objective and the one measurement or capability that defines success. Everything else follows from it.
2. Choose a form factor (1U to 6U)
The form factor sets your mass, volume and power ceiling. As a rough guide:
| Form factor | Typical mass | Good for |
|---|---|---|
| 1U | ~1–1.3 kg | Simple tech demos, beacons, education |
| 2U | ~2–2.6 kg | Small sensors, comms experiments |
| 3U | ~3–4 kg | Earth observation, most first missions |
| 6U | ~8–12 kg | Higher-resolution imaging, propulsion, deep space |
Most first-time teams land on 3U — enough room for a real payload, solar power and reaction wheels, while still fitting cheap, widely available deployers. Not sure? Browse the reference prototypes to see complete 1U–6U designs and what fits in each.
3. The core subsystems
Almost every CubeSat is built from the same building blocks:
- Structure — the frame that holds everything and mates with the deployer.
- EPS (power) — solar panels, battery and a power-management board.
- OBC (on-board computer) — the flight computer running your software.
- Communications — a radio (often UHF/VHF or S-band) and antennas.
- ADCS (attitude control) — sensors and actuators to know and control which way it points.
- Payload — the instrument that actually does the mission (camera, sensor, experiment).
- Thermal — coatings, insulation and layout that keep everything in temperature range.
4. Balance your budgets
Budgets are where CubeSat projects live or die. The three that matter most:
- Mass budget — the total of every component must stay under the deployer limit for your form factor.
- Power budget — the energy your solar panels generate over an orbit must exceed what your subsystems consume, including time in eclipse. See our CubeSat power budget guide.
- Data / link budget — you must be able to actually downlink the data you produce during the short windows your ground station is in view. See the RF link budget guide.
These budgets are all interlinked — a bigger payload needs more power and produces more data, which needs a stronger downlink and a bigger battery. Iterating them by hand is painful, which is exactly what the design tools automate.
5. Pick an orbit
Most CubeSats fly in Low Earth Orbit (LEO), either deployed from the ISS (~400 km) or into a sun-synchronous orbit (~500–600 km) as a rideshare. Altitude affects your coverage, eclipse time, radiation dose and orbital lifetime. Read how to choose a CubeSat orbit for the trade-offs.
6. Build, test, and test again
Space is unforgiving and you cannot pop up to fix a bug in orbit. Real missions go through functional testing, thermal-vacuum cycling, vibration testing and a “day in the life” rehearsal before launch. Even for a hobby build, test your power system across a full charge/discharge cycle and rehearse your comms link on the bench with the actual ground station hardware.
7. Getting to orbit
CubeSats reach space as secondary payloads (rideshares) on launches such as SpaceX Transporter, Rocket Lab Electron or via ISS deployment. You buy a slot through a launch broker or deployer provider, who will hand you an Interface Control Document specifying the exact mechanical, electrical and safety requirements your satellite must meet.
Next steps
The fastest way to learn is to design one. Start from a proven reference design, adapt it to your mission, and let the budgets update live as you go — all free, in your browser.
Design it for free in your browser
Defiant Smallsat is a free, all-in-one CubeSat & SmallSat design platform. Put this guide into practice — size your budgets, model your orbit and plan your mission without installing anything.