Propellants
- 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
- 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
- Spacecraft Mass – Directly proportional to propellant required for a given ΔV.
- Orbit Altitude – Lower altitude → higher drag → higher propellant consumption.
- Mission Duration – Longer operational life → more accumulated station-keeping and drag compensation.
- Activity Profile – Nominal operations (sun alignment, orbital maintenance).
- 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