Introduction to Space Mission Design

1
Introduction to Space Mission Design

• Prof. Solomon
• Prof Coverstone
• September 10, 2009

2
Elements of Space Mission Design
Robotic/Uncrewed
3
Create Several Potential Mission Concepts and
Architectures

• Step 1 Review the preliminary list of
  requirements and constraints.
• Objectives, requirements and constraints are
  flexible and can potentially be negotiated if you
  uncover unrealistic requirements and constraints.
• Step 2 Create potential top-level mission
  concepts.
• Key trade-offs and issues in the mission concept.
• Number of international partners, if any
• National interests or national security issues
  favoring a national mission only.
• Economic/political considerations and unique
  skills favoring an international mission
• Scope of mission in terms of funding
• Schedule constraints, consistent with planned
  observatory deployments
• Construction sequence
• Maintenance concept (if any)

4
Create Several Alternative Mission Concepts and
Architectures (Cont.)

• Step 2 (Create potential top-level mission
  concepts cont.)
• Key aspects of the mission concept
• System Robustness (reliability)
• Key trades level of redundancy and design
  philosophy
• Tasking, scheduling and control
• Key trades Level of autonomy at destination
  facilities and Earth, central vs. distributed
  control, task distribution between people and
  machines
• Communications architecture
• Key trades data rates, timeliness of
  communication
• Mission timeline
• Key trades deployment/retirement strategy,
  construction sequence, level of timeline
  flexibility
• Step 3 Define the subject characteristics.
• Mission subject is typically defined in the
  mission statement
• The subject of the mission is the thing which
  interacts with or is sensed by the space payload.
• Radiation environment, measure magnetotail and
  magnetosheath, etc.
• Step 4 Identify key payload issues.
• Launcher, space propulsion and configuration of
  spacecraft (s)
• Methodology to Size the vehicles, and determine
  number of vehicles in the constellation, space
  transportation methodology

5
Create Alternative Mission Concepts and
Architectures (Cont.)

• Step 5 Characterize destination orbit.
• Overall configuration
• Trajectories and orbit (s) of interest
• Mass properties by mission phase
• Total system mass, dry mass by subsystem and
  consumables mass, mass moments of inertia
• Reliability
• Approach to redundancy
• Subsystem characteristics
• Power
• Solar or other, body-mounted vs pointed arrays,
  Average and peak power provided, storage
  (batteries)
• Attitude control
• Attitude determination and control
  approach,operating modes, sensor and actuator
  characteristics

6
Create Alternative Mission Concepts and
Architectures (Cont.)

• Step 5 (Characterize destination operations
  cont.)
• Telemetry and command
• Command/telemetry format, telemetry storage
  capacity, number of channels by type
• Communications
• Uplink and downlink data rates, time delay,
  overall architecture
• Computer
• Speed and memory, data architecture
• Space Propulsion
• Type of technology, propellant and dry mass,
  sizes of thrusters
• Structures
• Configuration post boost vehicle, structure of
  nanosat (s)
• Thermal and Environmental
• Heaters, amount of heat dissipated, radiator area
  and orientation
• Overall system parameters
• Mission duration, level of autonomy (human vs
  computer workload), methodology of
  transportation, deployment, ground segment,
  formation flying (?), cooperative spacecrafts (?)

7
Create Potential Alternate Mission Concepts and
Architectures (Cont.)

• Step 6 Define orbit and transfer trajectories.
• Earth orbit altitude, inclination, eccentricity,
  argument of perigee for non-circular orbits
• Delta-V budget for orbit transfer
• Transfer orbital parameters
• Delta-V budget for insertion into L-2 orbit
• Constellation orbit (s)
• Launch windows opportunities vs anticipated solar
  events
• Step 7 Select launch and orbit transfer
  vehicles.
• Alternatives for the transportation element
• Number of launches by mission phase
• Mass, volume, size of payload per launch from
  Earth
• Launch vehicle
• Atlas, Delta, STS, Titan, Pegasus, Ariane, etc.
• Upper stage
• Pam-D, IUS, TOS, Centaur, integral propulsion
• Launch site
• Kennedy, Vandenberg, Baikonur and Kourou

8
Create Alternative Mission Concepts and
Architectures (Cont. Step 7)

• Step 7 (Select launch and orbit transfer vehicles
  cont.)
• Total mass to orbit by phase
• Include strategy regarding number and types of
  launch systems to be used
• For each launch system, the following information
  should be provided
• Cargo and payload bay size and shape
• Maximum accelerations
• Axial and lateral vibration frequencies and
  magnitudes
• Acoustic frequencies and magnitudes
• Orbital insertion accuracy
• Interfaces to deployment system

9
Create Alternate Mission Concepts and
Architectures (Cont.)

• Step 8 Select the mission operations approach.
• Operations automation level
• Fully automated ground stations, part-time
  operations, full time (24 hr) operations, full
  ground command and control, partial autonomy,
  full autonomy (not yet readily available)
• Command, control and communications architecture
• Timeliness
• Store and dump, real time link
• Control and data dissemination
• Single or multiple ground stations, direct to
  user, user commanding, commercial links
• Relay mechanism
• TDRSS, satellite-to-satellite crosslinks,
  commercial communications relay
• Mission operations characteristics
• Communications architecture at L-2
• Downlink and uplink path design
• Number and distribution of surface-based and
  space-based stations

10
Create Alternate Mission Concepts and
Architectures (Step 8, Cont.)

• Step 8 (Select the mission operations approach
  cont.)
• Relay satellites, if used
• Communications link budget
• Space-to-ground data rates
• Earth-based systems
• Use of existing or dedicated facilities
• Required transmit and receive characteristics
• Required data handling
• Other operation characteristics
• Software lines of code to be created vs number of
  operational personnel
• Full-time or part-time staffing
• Amount of commanding required
• Timeliness of data distribution

11
Create Potential Alternative Mission Concepts
and Architectures (Cont.)

• Step 9 Integrate steps 2-8 into a possible
  mission architecture.
• Identify the elements/components that are subject
  to trade
• Identify the main options for each tradable
  element
• Construct a trade tree of available options
• Look for other alternatives
• Step 10 Estimate life-cycle cost and assess
  reliability
• Options are parametric, analogous, and bottoms-up
  methods for costing
• For concept exploration, we use only the first
  two because we lack a detailed definition of the
  design. At this level, we simply want relative
  comparisons rather than absolute estimates, so we
  can accept the greater uncertainty in this these
  methods.

12
Summarize Mission Concepts and Architectures
(Cont.)

• Step 11 Evaluate, document and iterate.
• At this point we need to evaluate how well our
  concept meets the mission requirements.
• We must document all our steps so we have a
  record of what weve done for the next iteration.
  (Preliminary Design Report)
• Finally, we must go back to the beginning of the
  design process and continue to refine the design
  until we are satisfied with the final design.

13
Identify System Drivers and Critical Requirements

• Common System Drivers (significantly influence
  the overall cost, performance and design of
  detailed components)
• Number of launches required
• What limits driver Availability of launch
  system, cost of launching
• What driver limits Payload delivery capability
  (maximum volume and mass)
• Mass required at L-2
• What limits driver Capability of launch
  element, capability of space element
• What driver limits Size and capability of
  orbiting vehicle
• Size
• What limits driver Shroud or bay size,
  available weight, aerodynamic drag
• What driver limits Payload delivery capability
  (maximum volume and mass)

14
Identify System Drivers and Critical Requirements
(more)

• Common System Drivers ( continued)
• Power supply
• What driver limits Size of system, physical
  location of system, system lifetime
• Data rate
• What limits driver Storage, processing, antenna
  sizes, limits of existing systems, Power
  requirements
• What driver limits Information sent to user
• Communication
• What limits driver Coverage, availability of
  ground stations or relay satellites
• What driver limits Available information,
  timeliness, ability to command, autonomy

15
Identify System Drivers and Critical Requirements
(more..)

• Common System Drivers ( continued)
• Number of spacecraft
• What limits driver Cost, system size, logistics
  support for space transportation system, mission
  control
• What driver limits Payload delivery capability,
  Delivery concept
• Scheduling
• What limits driver Timeline and operations,
  decision making, communications
• What driver limits Timeliness of Data Delivery
• Operations
• What limits driver Cost, communications
• What driver limits Frequently principal cost
  driver, principal error source, pushes demand for
  autonomy for longer missions

16
Baseline a Mission Concept and Architecture
Summary

• Review the overall mission objectives.
• Develop various mission concepts.
• Review the various mission concepts with
  life-cycle costs.
• Pick the concept that best meets the objectives.
• This becomes teams baseline design.