Contact Us

1.9 Appendix

Naming Convention

OPCON Stages Examples

OPC-LAUNCH
OPC-ORBIT_INSERT
OPC-STANDBY
OPC-RENDEZVOUS
OPC-PROXIMITY_OPS
OPC-DOCKING
OPC-PROP_TRANSFER
OPC-UNDOCKING
OPC-RETURN
OPC-DISPOSAL

Requirements

IOR-<LEVEL>-<CATEGORY>-NNN

LEVEL

  • STKR = Stakeholder Requirement
  • MISR = Mission Requirement
  • SYSR = System Requirement
  • DERR = Derived Requirement
  • VERI = Verification Requirement
  • HSWR – High Level Software Requirement
  • LSWR – Low Level Software Requirement

CATEGORY

Discipline grouping

  • OPEC = Operational Coverage
  • FUNC = Functional Capability
  • PERF = Performance
  • SAFT = Safety
  • COMM = Communications
  • NAVI = Navigation
  • PROP = Propulsion
  • INTF = Interface
  • OPRS = Operations
  • REGU = Regulatory

SUB-CATEGORY

Is not part of the Requirements ID but SUB-CATEGORY is an optional attribute inside a requirement.

NNN

Three-digit number identified. Need not be sequential

Examples

IOR-MISR-OPEC-001: IOR-Mission Requirement-Operational Coverage-001

IOR-MISR-FUNC-004: IOR-Mission Requirement-Functional Capability-004

IOR-SYSR-PROP-012: IOR-System Requirement-Propulsion-012

IOR-SYSR-COMM-003: IOR-System Requirement-Communications-003

IOR-VERI-OPEC-001: IOR-Verification Requirement-Operational Coverage-001

ARCADIA Model Naming Convention (Very Important)

Model objects should be readable, not coded.

Use: <Type> – <System> – <Function>

Examples

  1. Operational Capability:LEO Servicing
  2. Operational Activity:Perform Rendezvous
  3. System Function:Transfer Propellant
  4. Logical Function:Regulate Propellant Flow
  5. Component:Service Vehicle
  6. Interface:SV-to-Depot Mechanical Interface
  7. Exchange:State Vector Data
  8. Component:Service Vehicle
  9. Component:Orbital Depot
  10. Component:Ground Segment

Acronyms

  • ISAM – In-space Servicing, Manufacturing, and Assembly
  • DSO
  • IOR – In-Orbit Refueling
  • PRM – Northrop Grumman’s Passive Refueling Module
  • RAFTI – Orbit Fab’s Rapidly Attachable Fluid Transfer Interface
  • RPOD – Rendezvous, Proximity Operations, Docking
  • SERB – Space System Command’s System Engineering Review Board
  • SSM – sustained space maneuver

Terms, Definitions and technologies

  1. Fuel Shuttle – Shuttle that services the spacecraft. Also called Service Vehicle
  2. Fuel Station – A space craft which stores the fuel or propellant, also called Fuel Depot
  3. Fuel Depot – Same as Fuel Station
  1. Service Vehicle – Same as Fuel Shuttle

References

  1. RPOD NASA – https://www.nasa.gov/reference/jsc-rendezvous-prox-ops-docking-subsystems/
  2. RPOD – https://www.merl.com/publications/docs/TR2024-016.pdf

IOR Technical Knowledge

Propellants

  1. Electric Propulsion Propellants (Noble Gases)

Primary propellants:

  • Xenon
  • Krypton

Why?

  • Used by almost all modern LEO constellations
  • Increasingly used in GEO satellites
  • Very high efficiency (high Isp)
  • Ideal for orbit raising + station keeping
  • Compatible with all-electric satellite platforms
  1. Storable Chemical Propellants (Hypergolic Family)

Primary combinations:

  • MMH + NTO
  • UDMH + NTO

Why still relevant:

  • Large installed GEO legacy fleet
  • High-thrust maneuvers
  • Reliable, flight-proven
  • Used in servicing vehicles and mission-critical burns

Core Factors Affecting Propellant Use

  1. Spacecraft Mass – Directly proportional to propellant required for a given ΔV.
  2. Orbit Altitude – Lower altitude → higher drag → higher propellant consumption.
  3. Mission Duration – Longer operational life → more accumulated station-keeping and drag compensation.
  4. Activity Profile – Nominal operations (sun alignment, orbital maintenance).
  5. Additional Maneuvers (DSO / Avoidance) – Each maneuver adds ΔV.
    Frequency per year directly increases total propellant use.

Formula to Calculate Propellant Use

Then the propellant mass is calculated using the Tsiolkovsky Rocket Equation.

m_prop = m₀ × (1 − exp(−ΔV / (Isp × g₀)))

Where:

  • m_prop = propellant mass (kg)
  • m₀ = initial total mass before burn (kg)
  • ΔV = total required delta-V (m/s)
  • Isp = specific impulse (seconds)
  • g₀ = 9.81 m/s²

Space Craft Weight

Uses the following approximations for calculations:

LEO Satellites

  • 400–700 kg → Good representative operational mass for modern commercial LEO spacecraft.

GEO Satellites

  • 2000–3000 kg → Reasonable mid-class GEO communications satellite mass (not the very large 6-ton class).

Sample Calculation for Propellant Use

LEO

  • LEO satellite mass: 600 kg
  • Mission duration: 5 years
  • Nominal operations only (drag makeup + station keeping)
  • Typical LEO ΔV budget (500–600 km altitude): ~50 m/s per year

10 Kgs

GEO

  • Mass at start of life: 3000 kg
  • Mission life: 15 years
  • Typical GEO station-keeping ΔV:
  • North–South: ~45 m/s per year
  • East–West: ~2 m/s per year
    → Total ≈ 50 m/s per year

Total ΔV over 15 years: 50 × 15 = 750 m/s

Propellant Type GEO satellites traditionally use hypergolic bipropellant: Isp ≈ 300 s

675 Kgs