Power Budgets: Ensuring Your Payload Has the Energy to Perform

You've selected a Blackwing platform that fits your payload's volume and mass. Excellent! But there's one more critical constraint that determines whether your mission succeeds or sits dead in orbit: power. 

A camera without power is just ballast. A radio without energy can't transmit. Your payload might fit physically, but if it can't get the electricity it needs when it needs it, your mission is over before it starts. 

Let's talk about how to build a power budget that actually works in orbit. 

Understanding Orbit Average Power (OAP) 

When we say the Sparrow provides 10W OAP, the Kestrel provides 30W OAP, and the Osprey provides 60W OAP, what does that actually mean? 

Orbit Average Power (OAP) is the average power available to your payload, averaged over an entire orbit. It's not the instantaneous power during operation—it's the sustained power budget accounting for charging, discharging, and operational duty cycles. 

Think of it this way: your CubeSat's solar panels generate power when illuminated by the sun, charging the batteries. Your payload draws power from those batteries during operation. OAP is the equilibrium point where power generation and consumption balance over a complete orbital period. 

For a typical Low Earth Orbit (LEO) at 500 km altitude, one orbit takes roughly 90-95 minutes. During that time, your satellite experiences approximately: 

• 60 minutes in sunlight (eclipse-free, panels charging)
• 30-35 minutes in Earth's shadow (eclipse, running on batteries only) 

Your payload's power consumption must fit within this charging-and-discharging cycle, orbit after orbit, day after day. 

Key Power Terms You Need to Know 

Before we dive into calculations, let's define the vocabulary: 

• Orbit Average Power (OAP): The average continuous power available to your payload over a complete orbit. This is your primary constraint and what Blackwing platforms specify.
• Peak Payload Power: The maximum instantaneous power your payload draws during active operation. This can be significantly higher than OAP if you operate for short durations.
• Duty Cycle: The percentage of each orbit your payload operates. A 30% duty cycle means your payload runs for about 27 minutes out of a 90-minute orbit.
• In-Rush Current: The brief surge of current (and power) drawn when your payload first powers on. Some components—motors, heaters, certain sensors—can draw 2-5× their steady-state power for a few milliseconds to seconds during startup.
• Standby Power: The power your payload consumes even when "off," maintaining memory, keeping clocks running, or staying ready for activation.
• Battery Depth of Discharge (DoD): How much of the battery's capacity you're allowed to use. Blackwing platforms manage this for you, but it limits how much energy is available during eclipse periods. 

How OAP, Peak Power, and Duty Cycle Connect 

Here's the relationship that governs your power budget: 

OAP = (Peak Power × Duty Cycle) + Standby Power 

This equation tells you everything. If your payload draws 100W when operating but only runs 20% of the time, its OAP contribution is roughly 20W (plus any standby power). 

Let's work through a real example for a Kestrel mission (30W OAP available): 

Example 1: High-Power, Low-Duty-Cycle Camera 

• Peak operating power: 80W
• Standby power: 2W
• Available OAP: 30W 

What duty cycle can you sustain? 

Rearranging the equation: 

• Duty Cycle = (OAP - Standby) / Peak Power
• Duty Cycle = (30W - 2W) / 80W = 0.35 or 35% 

Your camera can operate for about 31 minutes per 90-minute orbit, then must remain off while batteries recharge. 

Example 2: Moderate-Power, High-Duty-Cycle Sensor 

• Peak operating power: 25W
• Standby power: 3W
• Available OAP: 30W 

Duty Cycle = (30W - 3W) / 25W = 1.08 or 108% 

Wait—over 100%? This means your sensor draws less power during operation than the OAP budget allows. You can run it continuously (100% duty cycle) with power to spare. In fact, you could run it 100% of the time and still have about 2W of margin. 

Planning for Peak Power and In-Rush Current 

While OAP determines your average power consumption, you also need to consider instantaneous peaks. The Blackwing platform's power system can handle brief surges above OAP, but there are limits. 

Peak Power Considerations: 

• Most payloads can safely draw 2-3× their OAP allocation for brief periods (seconds to minutes)
• The battery and power distribution system have maximum current limits
• Sustained peak power reduces battery life and may trigger protection circuits 

In-Rush Current Management: Some components draw significant inrush current during startup: 

• Reaction wheels spinning up: 3-5× steady-state
• Heaters activating: 2-3× steady-state
• Cameras initializing: 1.5-2× steady-state
• Transmitters keying: 2-4× steady-state 

Good practice: if your payload has multiple high-inrush components, sequence their power-up over several seconds rather than turning everything on simultaneously. This prevents tripping overcurrent protection and stressing the battery. 

Matching Your Mission to Blackwing Platforms 

Now let's see how your payload's power requirements map to Blackwing platforms: 

Sparrow (1U) - 10W OAP. Best suited for low-power missions:

• Simple sensors (passive imaging, magnetometers, radiation detectors)
• Store-and-forward communications with low duty cycle
• Technology demonstrations with intermittent operation
• Missions where you can operate 10-20% of the orbit at moderate power 

Kestrel (3U XL) - 30W OAP. The versatile option for most missions: 

• Active imaging systems with moderate duty cycles
• RF payloads with regular but not continuous transmission
• Edge computing with periodic high-power processing bursts
• Missions operating 30-50% of the orbit at moderate-to-high power 

Osprey (6U XL) - 60W OAP. For power-hungry, high-performance missions: 

• Continuous earth observation or remote sensing
• High-throughput communications
• Multiple simultaneous payloads
• AI/ML processing with sustained compute loads
• Missions requiring 50-100% duty cycle at high power 

Building Your Power Budget 

Here's a step-by-step process to determine if your payload fits within a Blackwing platform's power allocation: 

Step 1: List all payload components and their power draws 

• Operating power for each component
• Standby/idle power
• In-rush current and duration 

Step 2: Determine your operational profile 

• How long does the payload need to operate per orbit?
• Is operation continuous or periodic?
• Are there specific orbital conditions required (sunlight, ground station passes, etc.)? 

Step 3: Calculate total peak power 

• Sum all components operating simultaneously
• Add 10-20% margin for inefficiencies and unknowns 

Step 4: Determine duty cycle 

• Minutes of operation per 90-minute orbit
• Convert to percentage (minutes ÷ 90) 

Step 5: Calculate required 

• OAP = (Peak Power × Duty Cycle) + Standby Power
• Add 15-20% margin for battery aging and solar panel degradation 

Step 6: Select your platform 

• Compare required OAP to Sparrow (10W), Kestrel (30W), or Osprey (60W) 

Example: Earth Observation Payload 

Let's design a power budget for a multispectral imaging payload: 

Components: 

• Imaging sensor: 35W active, 1W standby
• Onboard processor: 8W continuous
• Data storage: 3W continuous
• GPS receiver: 2W continuous
• Total standby (sensor off): 13W
• Total active (sensor on): 48W 

Mission Profile: 

• Image collection over target regions
• 30 minutes of imaging per orbit
• 60 minutes idle/processing/downlink 

Power Budget: 

• Active duty cycle: 30 min ÷ 90 min = 33%
• Active power contribution: 48W × 0.33 = 15.8W
• Standby power contribution: 13W × 0.67 = 8.7W
• Total OAP required: 15.8W + 8.7W = 24.5W With
• 20% margin: 24.5W × 1.20 = 29.4W 

Platform Selection: The Kestrel (30W OAP) fits this mission perfectly, with a small margin for growth or extended operations. 

Common Power Budget Mistakes 

1. Forgetting standby power. Components often draw power even when "off." Those few watts add up over a 90-minute orbit.
2. Ignoring eclipse periods. Your payload might draw 40W, but if you only operate during sunlight when panels are charging, your OAP impact is much lower. Conversely, operating heavily during eclipse drains batteries fast.
3. Underestimating in-rush current. A payload that draws 30W steady-state but 90W for 5 seconds at startup can trip protection circuits if you're not careful.
4. No margin for degradation. Solar panels lose 2-3% efficiency per year. Batteries degrade. Your OAP budget on Day 1000 is lower than Day 1. Plan accordingly.
5. Assuming 100% efficiency. Power conversion isn't free. The power distribution system has losses. Add 10-15% to your calculated requirements. 

Real-World Advice: Power is the Long Pole 

In our experience at Blackwing Space, power is often the constraint that drives platform selection—even more than volume or mass. A compact, lightweight payload can still require an Osprey if it's power-hungry. 

Start your power budget early. Instrument datasheets are notoriously optimistic about power consumption, so add margin generously in preliminary design. As you mature your mission, you can release margin—but you can't create power that isn't there. 

And here's a pro tip: if your power budget calculation puts you right at the edge of a platform's OAP (say, 28W for a 30W Kestrel), seriously consider the next size up. Solar panels degrade, batteries age, and missions evolve. That 2W of margin might disappear in Year 2 of a three-year mission. Future you—watching your payload brown out because the batteries can't keep up—will wish you'd budgeted conservatively. 

Bringing It All Together 

Over these three articles, we've covered the critical constraints for selecting your Blackwing platform: 

• Volume determines if your payload physically fits
• Mass determines if you can launch it affordably
• Power determines if it can actually operate 

All three must align for mission success. A payload that fits volumetrically but exceeds mass limits won't fly. A lightweight payload that fits but draws too much power will fail in orbit. 

The good news? Blackwing platforms are designed with these constraints in balance. The Sparrow, Kestrel, and Osprey each offer realistic, achievable allocations for volume, mass, and power that work together. We've done the systems engineering so you can focus on your payload. 

Now you have the tools to make an informed decision. Measure your payload dimensions, weigh your components, calculate your power needs, add appropriate margins, and select the platform that gives you confidence your mission will succeed. 

Ready to move forward? Configure your Blackwing platform today and come fly with us.