Burn Wire Release Mechanism for Spacecraft Tether Deployment

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Solution Overview

Problem

Tethered spacecraft with smaller end masses face challenges in complete deployment due to mismatched springs causing large tipoff rates, which can prevent the tether from fully deploying.

Innovation Solution

A telescoping stacer spring system is used to separate the end masses, where the stacer is coiled around a center rod and initially contained within a housing, biased to push the end masses apart, with a burnwire release mechanism to deploy the spring, allowing the stacer to extend and form a cylindrical boom, and the tether to fully deploy without interruption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If multiple springs are used to provide separation energy for tethered spacecraft, then the separation force is improved, but for smaller end bodies with small masses, any mismatch in the springs can result in large tipoff rates which cause the tether to not deploy completely

Engineering Contradiction:

Improveseparation forceVSAvoiddeployment reliability

Core Design Contradiction:

ForceVSReliability

Solution Approach 1:

The spring assembly is segmented into multiple individual springs arranged in a circular pattern, allowing each spring to contribute to the separation force independently while distributing the total force evenly around the separation axis, thereby reducing tipoff rates

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The springs are arranged asymmetrically in a circular pattern around the separation axis rather than in a linear configuration, which distributes the separation force uniformly in all directions perpendicular to the axis, minimizing rotational tipoff effects

Inventive Principle:

Principle #4Asymmetry

2Speed

If a burnwire release mechanism is used to cut the pretensioned loop, then the deployment speed is improved, but the complexity of the release mechanism increases

Engineering Contradiction:

Improvedeployment speedVSAvoidrelease mechanism complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The mechanical release mechanism is replaced with a burnwire release system that uses thermal energy to cut the pretensioned loop, eliminating the need for complex mechanical cutting components and reducing overall mechanism complexity while maintaining rapid deployment

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The stacer spring system ensures minimal rotational tipoffs and complete deployment of the tether, suitable for both small and large satellites, with the stacer extending to its full length to maintain the separation of end masses and allow the tether to unreel without interruption, ensuring effective deployment.

Implementation Method 1

a burnwire release mechanism cuts the loop to deploy the spring

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

The spring is coiled around a center rod and initially contained within a housing, the spring being biased to push the first endmass away from the second endmass

Methodology Applied

Scientific EffectElastic potential energy: Elasticity

Data Source

PatentUS10351269B2Burn wire release mechanism for spacecraft and terrestrial applications

Publication Date: 2019.07.16 THE GOVERNMENT OF THE UNITED STATES OF AMERICA AS REPRESENTED BY THE SECRETARY DEPARTMENT OF HEALTH & HUMAN SERVICES

AI summary

A burn wire release mechanism for a spacecraft or other system having two masses initially held together by a pretensioned loop, with a spring configured to push the masses apart. The burn wire release system includes at least one burn wire held in contact with the pretensioned loop material. When an electrical current flows through the burn wire, the wire heats up and severs the pretensioned loop, and the masses are pushed apart by the spring.