Mars or Bust Inc. (MOB)
System Requirements Review
Document
10/8/03
This document details the Level 0, 1, and 2 requirements for a Mars Habitat System currently under development by Mars or Bust, Inc. This system is based on the Mars mission scenarios described in NASA’s Design Reference Mission (DRM) (Kaplan and Hoffman, 1997). The top-level (0 and 1) requirements are from the DRM. The level 2 requirements were derived from the DRM and other sources that are listed in the References section of this document. All Level 1 and 2 requirements have been assigned individual IDs to facilitate requirement-solution tracing throughout the remainder of the design process.
A. Level 0 - Overall Mission Goal
Establish a Martian Habitat capable of supporting humans
B. Level 1 - System Requirements
B1. Habitat must support crew of 6.
B2. Habitat must support crew for 600 days without re-supply.
B3. Habitat must be deployed 2 years before first crew.
B4. Habitat shall be in a standby mode for 10 months between crews.
B5. All systems in Habitat must have an operational lifetime of greater than 15 years.
B6. All systems in Habitat must have low failure rates.
B7. Crew health and safety must be maintained.
B8. In-Situ Resource Utilization System must be integrated with the Habitat where applicable.
B9. Dependence on support from Earth must be minimized.
B10. Habitat surface infrastructure must be setup and checked out before crew arrives.
B11. Total Habitat mass (including all payload) must not exceed 34 tons.
B12. All mission critical systems must have 2 levels of redundancy.
B13. All life critical systems must have 3 levels of redundancy.
B14. Habitat must be launched in an 80 metric ton launch vehicle.
B15. Habitat must land, deploy, operate, and maintain all systems.
B16. All systems must be modular.
B17. All systems must be easily repairable.
B18. Electronic and mechanical equipment must be highly autonomous, self-maintained or crew maintained and possibly self-repairing.
B19. Habitat shall have auto fault detection and correction for all life/mission critical and mission discretionary elements.
B20. Systems must be easy to learn, similar, and use common software and hardware.
B21. Crew must be able to perform real time science activity planning to continue research activities.
Level 2 Subsystem Requirements
In order to support these top-level requirements, the mission architecture has been derived as shown below. The level 2 requirements for each subsystem are given below as well. An organization chart of MOB Inc. following this mission architecture is given in Appendix A.
C. Systems Engineering and Integration Subsystem
Systems Engineering and Integration is responsible for establishing all habitat system requirements and for delegating top-level subsystem requirements. Integration reviews and reconciles all subsystem design specifications, ensuring that all habitat subsystem requirements are met and that all subsystems interface properly, thereby creating a habitat that meets the overall mission requirement.
D. Command, Control, and Communication (C3) Subsystem
The C3 subsystem will provide the habitat’s command, control and communication capabilities. It will provide communication with Earth, including transmitting experimental data, habitat and crew health monitoring, personal communication, and mission-related information exchange between the Mars and Earth based personnel. The C3 subsystem will provide communication with crewmembers during EVAs. It will also allow Earth and Mars based monitoring of and control over the habitat’s subsystems. The C3 subsystem will also permit communication with and control over teleoperated rovers. The level 2 requirements for the C3 subsystem are given below:
D1. Must survive the transit to Mars.
D2. Must be sized to fit within the transport spacecraft.
D3. Must support set-up and checkout of surface infrastructure pre-crew.
D4. Must include a computer based library for operational and instruction maintenance and trouble-shooting of systems and hardware failures.
D5. Must support a "smart" automated habitat.
D6. Must provide Earth-control capability of some subsystems (rovers, etc).
D7. Must provide communication with rovers (from Earth and Mars base) (telerovers).
D8. Must provide communication with astronauts away from habitat (pressurized rover occupants and EVAs).
D9. Must provide real time downlink/uplink to Earth.
D10. Must support the capability for programmatic activities such as publicity, public affairs, documentation, reporting and real-time activity planning.
D12. All communications and computer systems must be able to withstand surface and habitat conditions.
D13. Electronic equipment must be highly autonomous, self or crew maintained and possibly self-maintaining.
D14. Must provide auto fault detection for all life/mission critical and mission discretionary elements.
D15. Must be able to handle communication and data processing load for 6 people for the duration of each 600-day mission.
D16. Must be able to function autonomously for 10 months.
D17. Must be able to return to normal function after dormant periods.
D18. Mass must not exceed 320kg.
E. Environmental Control and Life Support Subsystem
The Environmental Control and Life Support subsystem (ECLSS) is responsible for providing a physiologically and psychologically acceptable environment for humans to survive and maintain health in the Mars habitat. This includes providing and managing food, water, waste, and atmospheric conditions, as well as supplying crew accommodations and medical services. The level 2 requirements for the ECLSS subsystem are given below:
E1. Shall provide adequate Atmosphere Monitoring and Control.
E2. Shall provide CO2 Removal and Reduction.
E3. Must have necessary Gas Storage.
E4. Must have adequate Ventilation.
E5. Must provide Trace Contaminant Control.
E6. Shall provide Temperature and Humidity Control.
E7. Shall have Fire Detection and Suppression.
E8. Must supply entire crew with adequate sources and amounts of food for a 4-6 month transit to Mars, and an 18-20 month stay on the surface of Mars.
E9. Shall be able to collect and store liquid, solid, and concentrated wastes for immediate and/or delayed resource recovery.
E10. Must provide adequate supply of Hygiene water and Potable water.
E11. Must provide adequate crew accommodations.
E12. Shall provide psychological support by taking into account crew environment and other psychological factors.
E13. Must provide necessary medical services.
E14. Must provide crew health monitoring.
E15. The crew must have adequate protection from harmful radiation through habitat design and/or safe-haven capability.
E16. Mass must not exceed 4661 kg.
F. Structures Subsystem
The structures subsystem provides the pressurized volume required for the human habitat. It will contain the crew and incorporate all subsystems necessary to provide for the crew and the mission, provide radiation and micro-meteoroid shielding, and withstand all loading environments. The level 2 requirements for the Structures subsystem are given below:
F1. Habitat shall fit within the dynamic envelope of the launch vehicle.
F2. Must ensure crew health.
F3. Must be structurally sound in all load environments (acceleration, pressure, etc.).
F4. Must be easily repairable.
F5. Must stably support all other systems.
F6. Shall interface with other systems.
F7. Mass shall not exceed 20744 kg.
G. Automation and Robotic Interfaces Subsystem
The automation subsystem will determine which habitat functions are to be automated and design all automated systems. The robotics subsystem will have a major role in the development of infrastructure elements and habitat and operations, including site analysis, habitat assembly, instrument deployment, and scientific investigation. The robotics team must design interfaces that allow communication and control of mission robotics. The level 2 requirements for this subsystem are given below:
G1. Shall deploy scientific instruments used for initial analysis and monitoring of mars.
G2. Must deploy Infrastructure (nuclear power station, antennas, solar arrays, etc.).
G3. Must provide method of sample acquisition.
G4. Must provide method for Infrastructure inspection and maintenance.
G5. Must provide for construction and assembly of site and structures (site preparation, drilling, excavation).
G6. Shall support EVA activity.
G7. Robotics shall operate through entire mission duration.
G8. Robotics shall support control and communication (telerobotic or fully autonomous based on mission).
G9. Diagnosis and maintenance shall be automated (repair if possible).
G10. Robotics shall meet all fault tolerances and safety standards.
G11. Robotics shall meet all size and weight restrictions.
G12. Robotics shall provide for movement (Auto, teleauto).
G13. Robotics shall support payload operations.
G14. Equipment shall meet thermal-loading tolerances.
G15. Robotics will have a wide range of operations to minimize equipment being brought to surface.
G16. Shall support power requirements.
G17. Shall support the maintenance of habitat.
G18. Robotics will support deployment and assembly of base, power plants.
G19. Mass for Robotics and Automation is included in Structures and CCC.
H. Extra Vehicular Activity Interfaces Subsystem
The Extra Vehicular Activity Interfaces subsystem (EVA) is responsible for ensuring EVA capability throughout the entire mission and designing habitat interfaces for all EVA related equipment. The level 2 requirements for the EVA Interfaces subsystem are given below:
H1. Airlock must provide area for EVA/Rover/Emergency ingress/egress for Habitat.
H2. Airlock must provide area for suit ingress/egress.
H3. Airlock must provide dock for pressurized rover.
H4. Airlock shall meet all fault tolerances and safety standards.
H5. Airlock shall operate through entire manned portion of mission.
H6. Must be capable of self-diagnosis and self-maintenance (in the form of redundancies and fail-safes).
H7. Airlock shall meet all size and weight restrictions.
H8. Airlock must maintain pressurized volume.
H9. Must provide capability of communication between Airlock/EVA/Rover/Habitat.
H10. Habitat must supply consumables for Airlock/EVA/Rover.
H11. Thermal control must be maintained in airlock.
H12. Airlock must minimize the risk of Decompression Sickness (DCS).
H13. Airlock must provide Radiation Protection for humans.
H14. Airlock structure must be able to withstand Rover/Airlock docking maneuver.
H15. Hatches must be easily accessible and easy to use while in suit.
H16. Airlock must interface with Habitat.
H17. Hatch structure and material must meet safety standards.
H18. System Mass shall not exceed 1629 kg.
I. Thermal Control Subsystem
The thermal subsystem is responsible for providing a shirt sleeve environment for a crew of six and maintaining equipment within proper operating temperatures under all mission environmental extremes. The level 2 requirements for the Thermal Control Subsystem are given below:
I1. Must maintain a shirtsleeve environment for 6 crewmembers.
I2. Must keep equipment temperatures within operating limits.
I3. Must provide control over all Martian temperature extremes.
I4. Must be autonomous.
I5. Must operate over the mission lifetime of 15+ years.
I6. Must accommodate the transit to Mars.
I7. Must auto-deploy and activate if it is inactive during transit.
I8. Must report its status for communication to Earth during non-occupied times (for safety concerns).
I9. Mass shall not exceed 550 kg.
J. Mission Operations Subsystem
The task of the Mission Operations support team will be to identify, coordinate, and schedule crew operations within each subsystem. Before and during the mission, the Mission Operations team will be responsible for creating and modifying the operations schedule, in concert with the engineering and science teams. The Mission Operations team will assist in the design process by establishing clear hardware operational requirements, then approving operations and hardware designs subject to considerations of safety, efficiency, and crew time demands. It will be responsible for identifying and delivering relevant system status data to the onboard crew (e.g. caution and warning messages, alarms, critical parameters, etc.), and developing methods for responding to off-nominal conditions (i.e. failure modes identified by the systems engineers). The level 2 requirements for the Mission Operations subsystem are given below:
J1. Must perform setup and checkout of the surface infrastructure prior to crew arrival.
J2. Shall deploy the habitat 2 years before the first crew.
J3. There shall be a 10-month standby between crews.
J3. Shall have a 15+-year lifetime.
J4. Shall incorporate real time science activity planning in order to continue research activities.
J5. Both Earth and the Mars habitat shall be able to communicate with the rovers.
J6. The crew shall function autonomously from Earth based support.
J7. Crew shall be able to communicate with Earth for failure assist and vehicle health monitoring.
J7. Habitat shall be capable of real time downlink/uplink to Earth.
J8. Crew health monitoring will be provided.
J9. Shall have capability for programmatic activities such as publicity, public affairs, documentation, reporting, and real-time activity planning.
J10. Some systems must have Earth-controlled capability (rovers, etc).
J11. Life Support Subsystem (LSS) must be highly reliable, autonomous, and robust.
J12. Psychological support must be provided.
J13. EVAs shall involve 2 people for at least 8 hours per week.
J14. There shall be telerobotic rovers.
J15. Shall land, deploy, operate, and maintain surface systems.
J16. Shall perform mineralogical and chemical analysis of rocks, soil, and atmospheric samples.
K. Power Distribution and Allocation Subsystem
The power subsystem will interface with the nuclear power source and manage and distribute power throughout the Mars habitat. Both mobile and stationary sources of power will be present within the habitat to provide for all functions of the habitat and mission. The level 2 requirements for the Power subsystem are given below:
K1. Shall have a 15-year lifetime.
K2. Shall supply sufficient power with 3-level redundancy.
K3. Shall provide power storage and interfaces for rovers/EVA suits.
K4. Shall interface with transit vehicles.
K5. Shall supply power while reactors are being put online.
K6. Shall provide an emergency power cutoff.
K7. Shall be flexible in order to allow for future expansion or addition.
K8. Shall incorporate shielding around the reactor to keep radiation at an acceptable level.
K9. Must transfer power from reactor to habitat.
K10. Must have power dissipation capability.
K11. Must regulate voltage to a usable level.
K12. Must distribute power on a multi-bus system.
K13. Must include a fault protection system.
K14. Must follow maintenance and safety procedures.
K15. Mass must not exceed 3249 kg (including in-transit power).
L. Mars Environment and In-Situ Resource Utilization (ISRU) Team
The Mars Environment and ISRU Team is responsible for designing interfaces between the habitat and the ISRU unit, which may provide backup oxygen, water, and nitrogen for potential utilization. The team is responsible for working with the other subsystems to ensure that the habitat will operate successfully for more than 2 years under all Martian environmental extremes. The team will also evaluate potential use of any other in-situ resources. The level 2 requirements are given below: