CanSat & Suborbital Model Satellites

Definition and historical origin

A CanSat is a complete satellite system—electrical power regulation, onboard computer (OBC), barometric and inertial sensors, radio telemetry transceiver, recovery mechanism, and scientific or guidance payload—packaged within the volume of a standard beverage can ($\varnothing 66\text{ mm}\times 115\text{ mm}$, $393{\text{ cm}}^3$) or a cylindrical sounding-rocket payload canister ($\varnothing 120–146\text{ mm}$). Rather than entering orbit, a CanSat is lofted by a sounding rocket, captive balloon, or drone to an altitude of $0.5–4.0\text{ km}$ above ground level (AGL) and ejected near apogee to execute its mission during atmospheric descent.

The concept was proposed in November 1998 at the University Space Systems Symposium (USSS) in Hawaii by Professor Robert J. (Bob) Twiggs of Stanford University together with Japanese university faculty led by Professor Shinichi Nakasuka (University of Tokyo). Ten months later, on 11 September 1999, the first ARLISS (A Rocket Launch for International Student Satellites) campaign launched 350-gram student CanSats to $3.6\text{ km}$ over the Black Rock Desert, Nevada. Immediately following that inaugural CanSat campaign, Twiggs and Jordi Puig-Suari (Cal Poly) formalized the 1U CubeSat standard ($10\times 10\times 10\text{ cm}$, 1999)[1], and a decade later Twiggs introduced the 1P PocketQube standard ($5\times 5\times 5\text{ cm}$, 2009)[2][3].

Three primary competition architectures

Modern student CanSat and Model Satellite programmes operate across three distinct mechanical and operational tiers:

1. Standard 330 mL CanSat Class ($\varnothing 66\times 115\text{ mm}$, $300–350\text{ g}$): Adopted by the European Space Agency (ESA CanSat), ESERO-UK, and introductory university tracks. The entire probe fits inside a $\varnothing 66\text{ mm}$ cylinder without sharp protrusions; a parachute deployed at rocket ejection limits terminal velocity to $8–11\text{ m/s}$ while the probe transmits $1\text{ Hz}$ atmospheric pressure and temperature telemetry alongside a secondary experiment.
2. Two-Stage Container–Payload Model Satellite ($\varnothing 120–125\text{ mm}$, $600–1000\text{ g}$): Used in the American Astronautical Society (AAS) Student CanSat Competition, CNES C’Space, and international university Model Satellite competitions. A protective outer container deploys a stage-1 drogue parachute ($v_{t1}\approx 15\text{ m/s}$) at apogee ($670–1000\text{ m}$) and subsequently releases an internal science payload at $300–500\text{ m}$ AGL via a non-pyrotechnic mechanism (Nichrome burn-wire or servo pin-puller)[4]. The released payload descends at $\le 5\text{ m/s}$ using a passive autogyro rotor, ram-air parafoil, or reaction-wheel-stabilized camera platform.
3. Autonomous Comeback & Surface Rover Class ($\varnothing 66–146\text{ mm}$, up to $1050\text{ g}$): Pioneered at ARLISS (Black Rock Desert, $3.5–4.0\text{ km}$ apogee) and UNISEC regional events in Japan. After surviving high-speed parachute deployment, the vehicle autonomously navigates back to a designated GPS target coordinate using a dual-servo parafoil, autonomous quadrotor, or detachable surface rover.

Terminal descent velocity and parachute opening shock

During quasi-steady vertical descent through the troposphere, gravitational weight balances aerodynamic drag:

where $m$ is the descending mass, $\rho (h)$ is the local air density (${\rho }_0=1.225{\text{ kg/m}}^3$ at sea level under ICAO Doc 7488 ISA), $C_d$ is the canopy drag coefficient ($0.78$ for a flat circular canopy, $0.70$ for a low-oscillation cruciform chute, and $1.55–2.10$ for pulled-down-apex toroidal canopies), and $k_{\text{spill}}=d_{\text{spill}}/D_0$ is the central spill-hole ratio.

When the sounding rocket ejects the CanSat off-apogee at relative airspeed $v_{\text{deploy}}=20–45\text{ m/s}$, the peak opening shock load follows the Knacke–Pflanz method:

where $C_x\approx 1.25–1.70$ is the infinite-mass opening shock factor and $X_1\in (0.08,1.0)$ is the Pflanz ballistic mass-ratio reduction factor during canopy inflation time $t_f=n_{\text{fill}}{D}_0/v_{\text{deploy}}$.

Barometric altitude reconstruction and reset immunity

Flight software determines altitude above the launch pad ($h_{\text{AGL}}$) from static pressure $P$ via the tropospheric hypsometric equation referenced to the calibrated launch-pad pressure $P_0$:

where $L=0.0065\text{ K/m}$, $R_d=287.05\text{ J/(kg}\cdot \text{K)}$, and $g_0=9.80665{\text{ m/s}}^2$. To prevent two classic student failure modes—(1) a mid-air MCU brownout resetting $P_0$ to mid-air pressure, and (2) the black-powder ejection pressure spike falsely triggering low-altitude separation—flight firmware must:

• Store $P_0$ and the current state integer (LAUNCH_WAIT, ASCENT, APOGEE, SEP, LANDED) in non-volatile FRAM or EEPROM so a watchdog or brownout reboot resumes the active flight state immediately;
• Filter raw MEMS pressure samples (e.g. Bosch BMP388 or BMP390) and require $N\ge 10–20$ consecutive descending samples after a $600\text{ ms}$ post-ejection blanking window.

Comparison across suborbital and orbital student classes

Interactive tools and CAD templates

Use the CanSat & Model Satellite Engineering Hub or the standalone CanSat Lab Simulator to run parachute and opening-shock calculations, MEMS barometer apogee filter sizing, CSV telemetry link budgets, and Nichrome burn-wire release sizing, or to download $\varnothing 66\times 115\text{ mm}$ .STEP, .DXF, and $\varnothing 62\text{ mm}$ circular KiCad PCB templates.