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Power Budgeting

Model power generation, storage, and consumption for orbital compute systems across the full orbital cycle.
Status: Early Access — Request API key

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Overview

Power in orbit is fundamentally different from Earth:
  • Solar only — Primary power source is photovoltaic
  • Eclipse periods — No generation during Earth shadow
  • Battery cycling — Must store enough for eclipse
  • Degradation — Solar cells degrade over mission life

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Quick Start

from rotastellar import RotaStellar

client = RotaStellar(api_key="rs_...")

power = client.planning.power(
    orbit="LEO-550",
    compute_load_w=500,
    duty_cycle=0.8,
    mission_life_years=5
)

print(f"Solar array: {power.solar_array_m2} m2")
print(f"Battery: {power.battery_kwh} kWh")
print(f"Available during eclipse: {power.eclipse_power_w}W")
print(f"EOL margin: {power.eol_margin_percent}%")

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Parameters

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orbit
string
required
Orbit specification (e.g., LEO-550, GEO)
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compute_load_w
number
required
Peak compute power consumption in watts
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duty_cycle
number
default:"1.0"
Fraction of time compute is active (0-1)
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mission_life_years
number
default:"5"
Mission duration for degradation calculations
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housekeeping_w
number
default:"50"
Non-compute power (thermal, comms, ADCS)
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battery_dod
number
default:"0.3"
Maximum battery depth of discharge (0-1)

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Response

{
  "solar_array": {
    "area_m2": 3.2,
    "power_bol_w": 960,
    "power_eol_w": 768,
    "degradation_percent_per_year": 2.5
  },
  "battery": {
    "capacity_kwh": 0.85,
    "cycles_per_day": 15.5,
    "eol_capacity_percent": 80
  },
  "power_profile": {
    "sunlit_available_w": 680,
    "eclipse_available_w": 420,
    "average_available_w": 580
  },
  "margins": {
    "bol_margin_percent": 25,
    "eol_margin_percent": 12
  },
  "recommendations": [
    "Consider 10% larger array for operational margin",
    "Battery supports 5-year mission with 80% EOL capacity"
  ],
  "orbit_profile": [
    {"phase": "sunlit", "duration_min": 57, "power_w": 680},
    {"phase": "eclipse", "duration_min": 35, "power_w": 420}
  ]
}

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Power Budget Breakdown

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Typical LEO Power Budget

SubsystemPower (W)Notes
Compute (peak)500GPU/TPU workloads
Compute (idle)50Standby mode
Thermal30-100Heaters during eclipse
Communications20-50Varies with data rate
ADCS10-20Attitude control
Housekeeping20-30Avionics, sensors

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Power Modes

# Model different operating modes
power = client.planning.power(
    orbit="LEO-550",
    modes=[
        {"name": "full_compute", "power_w": 500, "duration_percent": 60},
        {"name": "reduced", "power_w": 200, "duration_percent": 30},
        {"name": "idle", "power_w": 50, "duration_percent": 10}
    ],
    mission_life_years=5
)

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Eclipse Operations

During eclipse, power is limited to battery capacity: 
power = client.planning.power(
    orbit="LEO-550",
    compute_load_w=500,
    eclipse_strategy="reduced"  # or "full", "suspend"
)

# Check eclipse power availability
if power.eclipse_available_w < 500:
    print(f"Must reduce to {power.eclipse_available_w}W during eclipse")

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Eclipse Strategies

StrategyDescriptionUse Case
fullMaintain full powerLarge battery, short eclipse
reducedReduce compute during eclipseBalanced approach
suspendSuspend compute, housekeeping onlyMinimal battery

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Degradation Over Mission Life

Solar arrays and batteries degrade over time: 
# Compare BOL vs EOL power
power = client.planning.power(
    orbit="LEO-550",
    compute_load_w=500,
    mission_life_years=7
)

print(f"Year 1 available: {power.solar_array.power_bol_w}W")
print(f"Year 7 available: {power.solar_array.power_eol_w}W")
print(f"Degradation: {power.solar_array.degradation_percent_per_year}%/year")

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Design Recommendations

Size for end-of-life (EOL) power needs plus 10-20% margin. Account for degradation: ~2.5%/year in LEO due to radiation.
Size for eclipse duration + margin. Limit depth of discharge to 30-40% for long cycle life.
Design for multiple power modes. Ability to reduce compute load extends operational flexibility.

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Next Steps

Thermal Simulation

Ensure thermal design matches power budget

Feasibility Analysis

Complete system feasibility check