Hybrid Propulsion Trajectory Optimization for LEO to L2 Transfer

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Solution Overview

Problem

Current methods for transferring spacecraft from low earth orbit to the Lissajous L2 orbit are inefficient, particularly for hybrid spacecraft, as they require multiple maneuvers and are not optimized for both high thrust and low thrust engines, leading to higher fuel consumption and longer flight times.

Innovation Solution

A control system for hybrid propulsion spacecraft that simultaneously optimizes both high thrust (HT) and low thrust high specific impulse (LT-HI) engine trajectories using a stable manifold trajectory, allowing for a combined optimal transfer trajectory with reduced maneuvers and shorter flight times.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If standard differential targeting with two maneuvers is used for transfer to L2 orbit, then the transfer can be achieved with impulsive maneuvers, but the method is not valid for hybrid spacecraft and requires multiple separate optimization steps

Engineering Contradiction:

Improveapplicability to hybrid spacecraftVSAvoidcomplexity of optimization process

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent combines the optimization of HT and LT-HI trajectory portions into a single unified optimization process. The cost function simultaneously optimizes both trajectory segments and their transition points, eliminating the need for separate optimization steps and making the method directly applicable to hybrid spacecraft with both engine types.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The unified optimization framework serves multiple functions: it optimizes HT impulsive maneuvers, optimizes LT-HI continuous thrusting, and determines the optimal transition point between engine types all in one process. This universal approach works for hybrid spacecraft configurations without requiring separate specialized procedures.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Loss of substance

If low energy transfers with exterior ballistic capture are used, then fuel consumption is reduced, but flight time increases to 90-150 days which is not relevant for fast transfers

Engineering Contradiction:

Improvefuel consumptionVSAvoidflight time

Core Design Contradiction:

Loss of substanceVSLoss of time

Solution Approach 1:

The patent employs dynamic optimization that continuously adjusts the trajectory parameters and thrust application timing. By dynamically determining the optimal transition point between HT and LT-HI engines and optimizing the entire trajectory profile, the system achieves a balance between fuel efficiency and transfer speed, obtaining fast transfers (comparable to Hohmann transfers) with reduced fuel consumption (17.2% less than Hohmann).

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The optimization process varies multiple parameters including thrust magnitude, burn timing, transition point between engine types, and trajectory shape. By changing these parameters simultaneously in a unified optimization, the system achieves both fast transfer times and reduced fuel consumption compared to traditional methods.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If separate optimization is performed for HT and LT-HI trajectory portions, then each portion can be optimized independently, but the overall combined optimal trajectory is not achieved

Engineering Contradiction:

Improveease of trajectory computationVSAvoidtransfer efficiency

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The patent merges the optimization of HT and LT-HI trajectory portions into a single unified optimization problem with a combined cost function. This simultaneous optimization ensures that the transition point and both trajectory segments are optimized together, achieving the true combined optimal trajectory rather than suboptimal separately optimized segments.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS9284068B2Fast-low energy transfer to Earth-Moon Lagrange point L2

Publication Date: 2016.03.15 THE BOEING CO

AI summary

A control system for a hybrid propulsion spacecraft, configured for transfer between low earth parking orbit (LEO) and a Lissajous L2 orbit (L2O), including a first control portion communicably connected to a high thrust (HT) engine portion of the hybrid propulsion spacecraft, a second control portion communicably connected to a low thrust high specific impulse (LT-HI) engine portion of the hybrid propulsion spacecraft, the first and second control portions being configured to control both the HT engine portion and the LT-HI engine portion to provide an optimal LEO to L2O transfer trajectory, wherein the optimal LEO to L2O trajectory includes an optimal LT-HI trajectory portion, selected from a stable manifold trajectory, and an optimal HT trajectory portion, and wherein the LT-HI trajectory portion and HT trajectory portion are configured for providing a combined optimal trajectory along the LEO to L2O transfer trajectory, and are optimized substantially simultaneously.