• 3.2 CoDR Checklist Kareena Shah 14 Feb 2026
• 5.2 CoDR Checklist Sreeja Akula  14 Feb 2026 
• 3.2 (Thermal Equalization) Thermal Strap Analysis Divya Krishna 14 Feb 2026 
• 4.1 (Rotational Dynamics and Updated Torque Calcs) Izaan Rizvi Colter Mahabir  Adrian Yang  Elisha Aranibar 14 Feb 2026 
• 4.1 (Tank and Propellant Pressure Analysis) Pranav Bala Colter Mahabir   21 Feb 2026 
• 7.2 CoDR Checklist Brandon Garcia 21 Feb 2026 
• 9.1 & 9.2 CoDR Checklist Rene Ramirez 21 Feb 2026 
• 4.2 (Control Authority Budgets) Colter Mahabir 21 Feb 2026 

3.2

-kareena

4.1 - 

4.1 Design Book MCU Specs:

• Frequency up to 480 Mhz
• 2 Mbytes of flash memory
• 1 Mbyte of RAM
• 3x 16-bit ADC
  • STM32H753 VI →
    • Number of Direct channels - 3
    • Number of Fast channels - 2
    • Number of Slow channels  -11
  • STM32H753 ZI →
    • Number of Direct channels - 2
    • Number of Fast channels - 9
    • Number of Slow channels  -17
  • STM32H753 AI/STM32H753 II /STM32H753 BI →
    • Number of Direct channels - 2
    • Number of Fast channels - 9
    • Number of Slow channels  -21
  • STM32H753 XI →
    • Number of Direct channels - 4
    • Number of Fast channels - 9
    • Number of Slow channels  -23
• –40 to +85 °C temperature range from a 1.62 to 3.6 V power supply
• 4x I 2Cs– 4x USARTs, 4x UARTs and 1x LPUART
• a high-resolution timer, 12 general-purpose 16-bit timers, two PWM timers for motor control, five low-power timers

Rigid-Body Rotational Dynamics (Tank Spin System):

Tank Specs:

• Material → 304L Stainless Steel
  Length → 15 cm
  Radius → 4 cm
  Thickness → 0.5 cm
  Mass → 1.143 kg

Configuration:

• Thin-walled cylindrical tank approximation
  Instrumented with internal thermocouples
  Sealed end-cap with wiring feedthrough

Moment of Inertia (Izz):

• Izz = mR²
  Izz = (1.143 kg)(0.04 m)²
  Izz = 0.001829 kg·m²

Drive Torque:

• τ = 0.840 N·m

Angular Acceleration:

• α ≈ 459.4 rad/s²

Spin Rate Requirement:

• 2–3 RPM
  ω ≈ 12.57 – 18.85 rad/s

Spin-Up Time:

• t = ω / α
  t ≈ 27 – 41 ms

Power Estimate:

• P ≈ 6.5 W

Motor / Servo Notes:

• Torque–speed curve limits max RPM
  Servo must provide ≥ 0.84 N·m stall torque
  Continuous power ≥ 6.5 W

Design Task:

• Evaluate 4 candidate servos from electrical spreadsheet →
  Compare torque, speed, power, and mass to select optimal model.

4.2

Required Torque

• Inertia torque at 2–3 RPM is very small
• Required torque is mostly caused by:
  • Bearing friction
  • Wiring and feedthrough drag (slip ring)
  • Thermal strap torsion
  • Propellant slosh disturbance
• Primary risk: underestimating disturbance torque (testing will help)
• Required torque must remain well below actuator capability to maintain margin

Available Authority

• Actuator capability: plus/minus 0.840 N·m (possible drive torque calculated in 4.1)
• Significantly larger than inertia torque requirement
• True usable torque depends on:
  • Continuous torque rating (not stall torque)
  • Thermal limits
  • Torque-speed performance curve

Control Margin (Minimum 30 Percent Required)

• System meets margin requirement if disturbance torque remains below actuator threshold
• Current analysis indicates large theoretical margin
• Margin must be proven through disturbance modeling and hardware testing

Saturation Limits

• Torque limited to plus/minus 0.840 N·m
• Continuous torque may be lower than peak rating
• Speed limited by actuator capability
• Controller must implement torque saturation limits

Coupling Effects With Other Subsystems

• Spacecraft bus experiences equal and opposite reaction torque
• ADCS (built in gyros) must compensate for tank spin momentum
• Power system sees peak draw during spin-up, less once reached speeds
• Structural elements add torsional stiffness and drag
• Propellant slosh introduces disturbance torque, strenuous on motor
• Possible micro-vibration coupling into IMU and attitude sensors

-Colter (not done, polishing atm)

4.3

5.1

Sensor Inventory

The sensor suite must be finalized for CoDR and justified, including:

IMU (gyroscopes and accelerometers

• ignore

Redundant rate sensing

• 2 pressure sensors

Tank temperature sensor array

• Custom from WIKA

Pump RPM and motor current sensing

• ignore

Pressure and vent-state sensing

• ignore

5.2

For each sensor, Controls shall specify:

Update rate

Accuracy and noise

Drift characteristics

Survivability under spin

Electrical interface

5.3

• Max Operating Temperatures of Components (C):
  • Tank Servos: max coil temp → 130, continuous (preferable) operating temp → 90
  • On Board Computer (OBC): -40 to 85 (assuming power supply 1.62V to 3.6V)
  • Pressure Sensor: -40 to 125
  • Watchdog timer circuit: -40 to 125
  • Thermocouple to digital converter: -55 to 125
  • RS-422 Transceiver Bus/Data: -65 to 150 (storage temperature), 150 max junction temperature, **highly recommended: -40 to 85
• Thermal strap details: STCH_Thermal Straps_Submitted_Q2 2024.pdf

7.1 -

FDIR = Continuously:

1. Observe system state

2. Compare to model/expectations

3. Flag anomalies

4. Enter a safe mode

5. Attempt recovery

6. Only return to nominal when consistent

7.2

How should the spacecraft react when something goes wrong?

Detection Limits: Numerical limits or conditions the system uses to decide when something is wrong

Fallback Control Laws: Backup control strategies when the normal system fails or becomes unreliable

Degraded Authority Allocation: How to reallocate control authority when components are partially lost

Safe-Mode Entry Conditions: What to do when normal spacecraft operations fails and protects itself

Sensor Bias / Dropout

Determine the safe bounds and measure

Implement redundant sensors and estimators with reduced measurement sets

Reduce pointing bandwidth (data transfer capacity)

Unexpected Torque Impulses

Determine the normal angular velocity and acceleration

Add impulsive actuators and transition to rate-damping (detumble) control

Spin-Axis Misalignment

Determine the normal angular momentum boundaries

Measure for deviations from the expected principal axis

Enter reacquisition mode and command alignment maneuver using coarse control

Partial Power Lose

Measure bus voltage, is it less than the minimum?

Battery state-of-charge, is it less than the lowest allowable charge?

Measure current charge, is everything running well?

Transition to low-power attitude mode (sun-pointing or thermally-safe orientation) with minimal actuation

Degraded Authority Allocation

During faulted operation, control authority is reduced and reallocated to preserve stability and survivability.

Control gains are reduced to maintain robustness under uncertainty

• High-power or high-torgue actuators become disabled under power-limited conditions
• Coarse sensors replace precision sensors when necessary
• Control priority is reallocated in this order:

1. Attitude stability
2. Power-positive orientation
3. Thermal protection
4. Precision pointing (suspended until recovery)

Safe-Mode Entry Conditions

The system will autonomously enter safe mode when any condition is met:

• Loss of valid attitude determination solution
• Angular rate exceeds safe operational limit
• Multiple sensor failures detected concurrently
• Bus voltage or battery state-of-charge falls below minimal threshold
• Persistent control residuals indicating instability or unmodeled disturbance

Safe Mode Configuration

• Sun-point of thermally safe orientation
• Rate-damping control law
• Essential avionics powered only
• Non-essential payload and mission operations are suspended

Once functionality is restored to normal conditions, the system shall exit safe mode

Thermal Straps

11. Risks and Mitigations