Autonomous Lander Discrete Landing Sequence
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Solution Overview
Problem
Conventional planetary landers face challenges in achieving pinpoint accuracy and payload delivery due to high fuel mass fractions, limited ΔV capability, and inability to correct for navigation errors and hazards, restricting landing sites to flat, uninteresting areas.
Innovation Solution
An autonomous space flight system with a discrete landing sequence using initial velocity braking, lateral divert maneuvers, and terminal velocity braking, combined with a high T/M ratio bi-propellant propulsion system and terrain correlation for navigation, enables precise landing and hazard avoidance, allowing for relocation to different sites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional continuous landing sequence with high fuel mass fraction is used, then soft landing is achieved, but payload mass fraction is limited to 5-10%
Solution Approach 1:
The landing sequence is divided into discrete phases: initial velocity braking, coasting with navigation error estimation, lateral divert maneuvers, and terminal velocity braking. This segmentation allows optimized fuel usage in each phase, reducing overall fuel mass fraction from 40%+ to enable 15%+ payload mass fraction while maintaining soft landing capability.
Solution Approach 2:
Navigation error estimation is performed during the coasting phase before terminal braking, allowing preliminary correction planning. Lateral divert maneuvers are executed in advance to remove cross-track errors, enabling more efficient terminal braking and reducing total fuel requirements.
2Reliability
If conventional continuous landing sequence is used, then landing is achieved, but unknown navigation errors cannot be removed
Solution Approach 1:
The system estimates navigation errors (cross-track and along-track) during the coasting phase by comparing expected with actual position. This feedback information drives corrective lateral divert maneuvers and adjusts terminal braking parameters, enabling removal of unknown navigation errors and achieving pinpoint accuracy.
Solution Approach 2:
The landing sequence transitions from static continuous burning to dynamic discrete maneuvers with variable thrust levels. The propulsion system adapts thrust magnitude and duration based on real-time navigation error estimates, enabling responsive correction of unknown errors while optimizing fuel consumption.
3Reliability
If conventional propulsion system with limited T/M ratio is used, then controlled descent is achieved, but hazard avoidance and relocation are not possible
Solution Approach 1:
The propulsion system achieves high T/M ratios (15:1 to 100:1 per nozzle) through parameter changes in thrust magnitude and pulse duration. This enables the lander to perform hazard avoidance maneuvers by generating sufficient thrust to divert from predicted landing sites, and relocation hops by achieving lift-off and controlled descent to new sites.
Solution Approach 2:
The propulsion system uses pulsed thruster operations rather than continuous burning. Short high-thrust pulses provide the impetus for hazard avoidance diverts and relocation hops, while coasting phases allow navigation error correction and site selection, creating a rhythmic pattern of thrust-coast-thrust that enables versatile operations.
4Quantity of substance
If discrete landing sequence with high T/M ratio propulsion is used, then fuel mass fraction is reduced, but system complexity increases
Solution Approach 1:
The propulsion system is divided into multiple nozzles (4-8) that can be independently controlled. This segmentation allows distribution of control complexity across multiple simpler actuators, each handling a portion of the total thrust requirement, while maintaining the capability for high T/M ratio maneuvers.
Solution Approach 2:
The control system dynamically adjusts which nozzles fire and at what thrust levels based on real-time navigation state and desired maneuver. This dynamic allocation of propulsion resources optimizes fuel efficiency while managing control complexity through adaptive rather than static nozzle scheduling.
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 approach significantly reduces fuel mass requirements, increases payload capacity, and enables landing on scientifically valuable sites, minimizing rover requirements and enhancing mission capability by achieving precision and hazard avoidance.
Implementation Method 1
The lander's bi-propellant propulsion module includes fuel tanks for storing propellant and a set of nozzles configured to expel the propellant to perform terminal velocity braking and lateral divert maneuvers
Implementation Method 2
The terrain image correlator is configured to correlate the gathered terrain data to reference maps to provide a navigation update
Data Source
AI summary
An autonomous unmanned space flight system and planetary lander executes a discrete landing sequence including performing an initial velocity braking maneuver to remove velocity at altitude, coasting during which the planet surface is imaged and correlated to reference maps to estimate cross-track and along-track navigation errors and one or more lateral braking maneuvers are performed to reduce cross-track navigation error, and performing a terminal velocity braking maneuver(s) to reduce the along-track braking maneuver and remove the remainder of the velocity just prior to landing. A bi-propellant propulsion system provides a very high T/M ratio, at least 15:1 per nozzle. Short, high T/M divert maneuvers provide the capability to remove cross-track navigation error efficiently up to the maximum resolution of the reference maps. Short, high T/M terminal velocity braking maneuver(s) provide the capability to remove along-track navigation error to a similar resolution and remove the remaining velocity in a very short time window, approximately 3-15 seconds prior to touchdown. The propulsive efficiency frees up mass which can be allocated to a fuel to remove the unknown navigation errors, perform hazard avoidance and/or relocate the lander by flying it to another site or be allocated to additional payload.