Task Flow and Trade Tree
The idea is to develop a flow of tasks from feasibility to mission and
list the trades as relevant (or associated) to particular tasks and operations.
The trades can then be distilled and prioritized. The approach is to create
& maintain a baseline design, the objective of which is to keep alive
the feasible, rational and optimal design in that priority. The trades
that are needed to make the design feasible and rational are done first
followed by ones that impact the vital statistics the most (mass, volume,
cost, schedule). Within this priority the ones that are most decoupled
can be chosen first and the ones most dependant on other trades last.
Task Flow along with Trades:
- Feasibility Study
- Propose Phase A/B
- Team organization and structure
- Means of operation
- Perform Phase A/B
- Risk reduction testing and prototyping
- Conduct PDR
- Level of documentation
- Review format
- Review process
- Review issues handling
- Detailed Design & Development
- Traditional vs Rapid prototyping
- Full digital Product Definition Vs paper
- Quantitative reliability analysis (design, system redundancy)
- Fabrication & test
- Facility & where
- SRM & QA - how?
- Parts qualification: level and process
- Level, detail of reporting & records
- Integrate
- Facility, where?
- Mass & inertia determination - CAD vs measure (seperately for sat,
SRM, rover, lander & combine)
- Prelaunch processing:
- Level of testing support
- Hazardous processing
- Sequence of integration
- Launch processing
- Post mate testing
- Mating sequence
- Pad access requirement
- Pad & Launch environment conditioning
- Launch to TLI
- Science Operations
- Mission Operations
- Coast
- Nav
- Attitude control & strategy
- MCC - when & how commanded
- Prepare for descent
- Attitude control
- SRM start timing
- SRM burn
- Spin vs 3-axis
- SRM jettison
- Deploy: when
- Terminal descent
- Fixed Landing vs piloted vs autonomous steer vs obstacle avoidance
vs autonomy split - lander/rover
- Plume analysis
- Thruster clustering and placement
- Short vs long legs, 3 vs 4 legs
- Post land checkout
- What's deployed
- What's tested
- Contingency planning
- deploy
- Test Comm links
- Test Computing & avionics
- Test sensors
- Test Power & thermal
- Command reception, validation, cycle times and latency
- Offload checkout
- Lander-rover vs Lander & rover
- Decoupling - what? how?
- Lander - rover component sharing
- Ramp or other
- deploy
- Test motion ranges of locomotion & other moving parts
- Test drill
- Conduct test sorties (expand here)
- Test locomotion
- Transformer vs Ackerman steer, 3 vs 4 wheel, suspend vs not
- Test navigation
- Test safeguarding & autonomous capabilities
- Test terrain ability and sensors
- Test Comm link near & over horizon (multipathing and diffraction)
- Test drill, sampling and analysis
- Conduct Science Sorties (Baseline Mission)
- Terrainability requirements
- Comm strategy: mast, surface relay and satellite
- Develop local terrain & horizon maps
- Explore lighted areas for light
- Explore cold trap fringes
- Exploratory drives into cold traps
- Baseline Mission Plan update
- Execute baseline mission
- Extended Mission
- Get Earthrise 2000
- Long distance traverse and sun tracking
- Autonomous operations
Key Trades and Results
Certain important issues bifurcate and impact the spacecraft DD&T
significantly enough that they need to be resolved ahead of time. The process
is to identify the trades, prioritize them and develop a trade tree and
conclude the process where the remaining trades no longer shake up the
spacecraft development significantly.
Prioritized Trade List
- Lander-Rover vs Lander & Rover: The spacecraft is configured
to fire a solid fuel Thiokol motor for about a minute to bleed the energy
off. This motor then sperates minimizing the soft-landing mass fraction
(and hence maximizing useful landed mass). The two distinct ways the rest
of the spacecraft can be built are
- To develop a unified lander-rover where the machine that lands is the
machine that rolls (with possible shedding & deployment)
- To have a seperate Lander & Rover, where the lander effects
soft landing and the rover (after a possible harness disconnect and a strucutral
mounting disconnect) rolls off the lander.
- Transformer Chassis Vs 4-Wheel Ackerman Chassis Vs Three Wheeler
- Comm Scenario: Mast, deployed mast, satellite
- Fixed landing vs Real-time visuals based controlled landing
- DD&T & flight process: Prototyping technique - NASA vs Rapid
- evolve
- Major Facility: Dewey, Huntsville, CMU, JSC, JPL - evolve
- Mission landing site selection
- Night Ops Hours - 20 to 40?
- Terrainability: 15, 20, 25, 30 deg slope capability & soft soil
needs vs mission confidence of terrain & ice models
- Comm Strategy: High deployed mast, vs Drop off comm station vs
Orbiter
- Autonomy Strategy: To do ro not to do, how to prioritize
- Lunar night Hibernate vs not: Determined by mission duration and
RHU tradeoff