Spacecraft Mechanisms

Overview

Spacecraft mechanisms include reaction wheels, magnetic torquers, control moment gyroscopes, inertial sensors and drive mechanisms. Angular momentum (N·m·s), torque (N·m) and magnetic dipole moment (A·m²) describe different physical quantities and must be compared separately.

Mechanism Categories

Reaction Wheels

The 090, 130 and 160 wheels provide different momentum capacities and control interfaces.

Magnetic Torquers

Micro magnetic torquers and combined flywheel/torquer assemblies support magnetic actuation and wheel momentum management.

Gyroscopes & CMGs

Rate sensors measure rotation; control moment gyroscopes produce control torque. These are distinct roles even though both product names may contain “gyroscope”.

Drive Mechanisms

Solar array and antenna drives provide controlled deployment or pointing for their associated structures.

Performance Specifications

Product	Parameter	Published value
090 reaction wheel	Rated momentum / mass	0.12 N·m·s / ≤0.75 kg
130 reaction wheel	Rated momentum / mass	0.5 N·m·s / 2.1 ±0.3 kg
160 reaction wheel	Rated momentum / mass	4 N·m·s / ≤3.8 kg
Micro magnetic torquer	Magnetic dipole moment	0.5, 1 or 10 A·m², by model
Dual-axis antenna drive	Output torque	>3 N·m
Extended-arm solar array drive	Output torque	≥10 N·m

Frequently Asked Questions

What is the angular momentum capacity of reaction wheels?

The 090, 130 and 160 models list 0.12, 0.5 and 4 N·m·s respectively. These are angular momentum capacities, not torque ratings; request the torque-speed characteristics needed for your maneuver profile.

How do reaction wheels and magnetic torquers work together?

Reaction wheels exchange angular momentum with the spacecraft. Magnetic torquers interact with the ambient magnetic field and can support wheel desaturation where that field provides suitable control authority.

What is the expected lifetime of these mechanisms?

Design life is model-specific. The VSCMG lists 5 years and the Coriolis vibratory gyroscope lists 8 years. Review duty cycle and qualification conditions for the intended application.

Can I use multiple reaction wheels for redundancy?

A suitable wheel arrangement can provide redundancy. Confirm control authority after a failure, wheel orientation, interface requirements and spacecraft control algorithms as part of the system design.

What control interfaces are available?

The 130 wheel lists an analog interface; the 090 and 160 wheels list RS-422 or CAN. Other mechanisms have their own interface requirements.

Control Modes

• Momentum Bias: Maintain a nominal stored wheel momentum as part of the attitude-control design.
• Momentum Dumping: Transfer accumulated wheel momentum using external actuators such as magnetic torquers or thrusters.
• Slew Maneuvers: Change spacecraft attitude within the selected actuators’ torque and momentum limits.
• Fine Pointing: Coordinate sensors and actuators to meet the mission pointing requirement.

Integration Support

Check mounting, power, interface, thermal range, disturbance characteristics and qualification records for the selected mechanism. Request technical information.

Last updated: 2026-11-07