What is Space Mission Engineering?

Space Mission Engineering is a process

Many different names that mean the same thing, or overlap strongly: space systems engineering, systems engineering, space mission engineering,

• I didn't know exactly what i wanted to do, just work in the space industry. Even harder was finding a masters since there were so few and they varied so much

• What is systems engineering?

• "System(s) Engineering is an interdiscplinary approach governing the total technical effort to transform requirements into a system solution." - ESA/ECSS

• "Systems Engineering integrates all the disciplines and specialty groups into a team effort forming a structured development process that proceeds from concept to production to operation" - INCOSE

• "System" - "Set of interdependent elements constituted to achieve a given objective by performing a specified function" - ECSS/ESA

• What does a space engineer do?

Importance of Systems Engineering:

• Coordinates the different subsystem experts - spacecraft are too complex to be designed by an individual

• Gives an overview of the whole spacecraft system

• Coordinates designs from the top, to ensure that all the subsystems work in harmony

• Maintains focus towards the mission goals

• Fits the design of the spacecraft and mission into the broader organisational elements - Project management, manufacture, product assurance, AIT

• Often coordinates activities across international/inter-company groups

With no systems engineering:

add "dream airplanes" sketch by C.W. Miller

So, what must the space systems engineer coordinate? What elements are required to make up a complete space mission?

Elements of a Space Mission:

• Space segment (spacecraft + payload)

• Mission application (subject, users)

• Orbit

• Launch

• Ground segment

• Operations

• Space-ground communications

Also... Project management, legal aspects, manufacture & test, data dissemination etc, in support of the above

Space segment: what functions are required on an operational spacecraft?

• Structural/mechanical subsystem function: holds the configuration during launch and in orbit. Allows for ground handling and transportation. Provides interface with launch vehicle. Allows moving parts.

• Structural subsystem hardware elements: Aluminium allow and carbon composite thrust tubes, space-frames. honeycomb panels. Fastenings. Motorised or spring deployment mechanisms, drive assemblies for solar array tracking, mirror scanning mechanisms, release mechanisms, etc

• Power subsystem function: Provides (generates and/or stores), conditions and distributes electrical supplies to all payload and spacecraft subsystems.

• Power subsystem hardware elements: Conditioning and distribution electronics, solar arrays, radioisotope thermoelectric generators, nuclear reactors, solar dynamic generators, fuel cells, batteries.

• Thermal control subsystem function: Controls the thermal environment of on-board equipment.

• Thermal control subsystem hardware elements: temperature sensors, heaters, heat pipes, thermal insulation blankets, thermal paints and other coatings, second surface mirrors, radiators, cryogenic cooling

• TT&C and OBDH functions: TT&C forms and transmits payload and housekeeping data to the ground; used for tracking; receives and decodes telecommands from the ground. OBDH: data processing, control, autonomous functions, data storage

• TT&C and OBDH hardware elements: Encoders, decoders, data buses, solid state memories, processors, RF transmitters/receivers, antennas, RF waveguides, amplifiers

• AOCS function: Controls P and sometimes V, often influenced by S

• AOCS hardware: Attitude sensors (earth, moon, sun, star magnetometers, integrating rate gyros). Actuators (momentum and reaction wheels, gas thrusters), pointing strategy, control laws and computations, mono and bi propellant liquid and solid rocket engines, electric engines, solar sails

• Payload function: provides the purpose and rationale for the space mission. May include science, earth observation, communications etc

• Payload hardware elements: Highly diverse, but may include microwave technology, IR, UV & xray optical instruments, particle detectors, sample acquisition, mechanisms, microgravity experimental and manufacturing facilities, habitation and laboratory modules.

• Space hierarchy:

• 

Develop original example similar to firesat to use throughout book, or use a real life mission from ESA and describe how it was developed from concept to launch

Systems engineering methodology:

Objective - requirements - design options - trade-offs - concept select and definition

Key Systems Engineering Elements

• Requirements analysis - defines requirements for all parts of the global system

• Identification of design options

• Trade-off analysis - balances the requirements of different elements of the system and allows selection of best overall design solution

• Control of budgets: physical parameters: mass, size, power, fuel, data, tolerances, cost

• Definition of margins to be used

• Definition of interfaces between subsystems

• Design, manufacture, test

• Verification that requirements have been met

• Maintenance of databases of requirements, analyses, design and verification data

Requirements Analysis:

• Requirements may be directed or derived

• Directed requirements come from the mission requirements specification - i.e customer - eg requirement for a particular payload performance

• Derived requirmeents are inferred from the directed requirements and mission objectives

• Requirements can (should) be questiond! - they may come from incorrect assumtpions

• Good requirements should be quantitative: allows you to know if you've met them