Spacecraft Transfer from Geosynchronous Orbit to Lunar Orbit
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Solution Overview
Problem
The challenge lies in efficiently transferring a spacecraft from a geosynchronous transfer orbit (GTO) with significant inclination to a lunar orbit, requiring precise maneuvers to achieve the desired inclination and minimize energy expenditure while avoiding direct illumination by Earth and Sun radio sources, which interfere with the DARE mission's goal of measuring red-shifted radiation from primeval hydrogen.
Innovation Solution
The solution involves a sequence of velocity maneuvers, including apogee-raising, lunar flyby, and resonance orbit establishment, utilizing ΔV changes to intersect the Moon's orbit, achieve lunar capture, and select desired inclination and perilune altitude, allowing for both standard and ballistic capture methods, with optional low-thrust maneuvers to stabilize the lunar orbit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a standard impulsive lunar capture maneuver is used from GTO, then the spacecraft can reach lunar orbit, but the energy expenditure (ΔV) is excessive and the trajectory is complex
Solution Approach 1:
The invention introduces an intermediary body (the Moon) to assist the transfer process. By using lunar gravity assistance through a flyby maneuver, the spacecraft leverages the Moon's gravitational field as a mediator to change its trajectory and energy state, converting a direct high-ΔV impulsive transfer into a multi-phase transfer that uses gravitational interaction to reduce propellant requirements
Solution Approach 2:
The invention transitions from a static impulsive maneuver model to a dynamic continuous transfer model. The spacecraft performs a sequential process: apogee raising to extend orbital period, phasing with the Moon's motion, executing a lunar flyby with gravity assistance, and finally performing capture. This dynamic approach allows the spacecraft to continuously adjust its trajectory and utilize gravitational fields along the path, reducing total energy expenditure compared to a single impulsive maneuver
2Use of energy by moving object
If the spacecraft performs multiple apogee-raising maneuvers to minimize finite burn losses, then the energy efficiency improves, but the transfer time increases
Solution Approach 1:
The invention performs preliminary apogee-raising maneuvers before the lunar flyby to extend the spacecraft's orbital period and align its arrival time with the Moon's position. By preparing the trajectory in advance through controlled apogee extensions, the spacecraft ensures optimal phasing with the Moon, enabling the gravity assistance maneuver to occur at the most energy-efficient point in the transfer sequence
Solution Approach 2:
The invention utilizes periodic orbital mechanics to synchronize the spacecraft's extended orbital period with the Moon's orbital period. By performing multiple apogee-raising maneuvers that progressively extend the orbit, the spacecraft creates a periodic transfer trajectory that naturally phases with the Moon's motion, allowing the flyby to occur at the optimal moment without requiring excessive ΔV corrections
3Use of energy by moving object
If the spacecraft uses ballistic lunar capture (no thrust) to reach lunar orbit, then the energy expenditure is minimized, but the orbit stability and precision are reduced
Solution Approach 1:
The invention applies partial action by using a small follow-on capture maneuver (ΔV5 ≈ 265 m/sec) after the ballistic flyby. Rather than attempting perfect precision in the flyby parameters, the spacecraft allows the ballistic capture to place it in a near-lunar orbit, then applies a controlled correction to achieve the desired stable lunar orbit. This partial correction approach reduces total energy expenditure compared to requiring perfect flyby precision while still achieving reliable orbit insertion
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
This method enables efficient transfer to a lunar orbit with arbitrary inclination and altitude, minimizing energy expenditure and avoiding interference from Earth and Sun radio sources, thereby facilitating the DARE mission's objectives.
Implementation Method 1
lunar gravitational assistance
Data Source
AI summary
Method for placing a spacecraft into a lunar orbit, either by standard (i.e., impulsive) or ballistic (i.e., non-impulsive) capture, from an Earth orbit that is significantly inclined relative to the lunar orbit plane, with no constraint on the local time of perigee for the starting orbit.