# Trade Study: Battery Topology vs. Weight — All-Electric Group 1 Feasibility

**Document:** TS-MRTX-PWR-001
**Revision:** v1.0
**Date:** 3 June 2026
**Prepared by:** Aerix Defense Systems (fictional) — D. Reyes, Propulsion & Power Lead
**Companion to:** ORL-MRTX-001
**Distribution:** Notional / Unclassified test material

---

> **FICTIONAL DOCUMENT — METHODOLOGY TEST INPUT**
>
> Fabricated test material for an academic methodology demonstration. Not a real trade study, not a real proposal. Numbers are first-order engineering estimates chosen to be realistic and self-consistent, not validated design data.

---

## 1. Purpose

The PMA-263 RFI assumes an all-electric air vehicle under 20 lb MGTOW (DoD UAS Group 1) delivering not less than 2.5 hours endurance with the full RSTA payload. This trade study evaluates whether that combination closes with current battery technology, and if not, what the lightest feasible all-electric configuration weighs. The finding drives the propulsion architecture and class-assignment decisions in the ORL.

## 2. Mass Budget Framework

For a multirotor VTOL, hover power dominates the energy budget. On-station endurance is set by stored energy divided by average electrical power demand. For an all-electric configuration:

```
MGTOW = m_structure + m_propulsion + m_avionics + m_payload + m_battery
Endurance = E_battery / P_avg = (m_battery × ρ_usable) / P_avg
```

where `ρ_usable` is usable battery specific energy (Wh/kg) after depth-of-discharge, packaging, and reserve, and `P_avg` is average electrical power including hover, payload, and avionics.

## 3. Fixed Mass Estimates (Non-Battery)

| Item | Mass (lb) | Basis |
|---|---|---|
| Structure (Group 1 scale) | 4.5 | Quadcopter airframe, landing gear, fasteners |
| Motors + ESCs (×4) | 2.2 | High-power-density brushless for ~6 kW peak |
| Avionics + flight controller | 1.0 | Autopilot, companion compute, wiring |
| Navigation (GNSS/INS) | 0.6 | Tactical-grade dual-antenna unit |
| Datalink (MANET radio + antennas) | 1.3 | Multi-band tactical radio |
| Mission payload (EO/IR turret) | 2.0 | Baseline ISR variant |
| **Non-battery subtotal** | **11.6** | |

This leaves, against a 20 lb Group 1 ceiling, **8.4 lb (3.8 kg) for battery** before any margin.

## 4. Power Demand Estimate

| Load | Power (W) | Notes |
|---|---|---|
| Hover (avg) | 5,200 | ~17 lb all-up at ~6.5 kg/m² disc loading; cruise/loiter blend |
| Avionics + flight control | 120 | |
| Datalink | 90 | Transmit duty-cycle averaged |
| Payload (EO/IR) | 60 | |
| **Average electrical demand** | **~5,470** | ~5.47 kW |

## 5. Battery Topology Comparison

Usable specific energy assumes 85% depth-of-discharge, 90% packaging efficiency, and 10% reserve.

| Chemistry | Cell Wh/kg | Usable Wh/kg | Battery mass needed for 2.5 hr @ 5.47 kW | Verdict |
|---|---|---|---|---|
| Li-ion (NMC, current) | 250 | ~172 | see §6 | Infeasible |
| Li-ion high-energy (silicon-anode) | 300 | ~206 | see §6 | Infeasible |
| Li-poly (high C-rate) | 200 | ~138 | see §6 | Infeasible |
| Li-S (emerging) | 400 | ~275 | see §6 | Infeasible |
| Solid-state (projected) | 450 | ~310 | see §6 | Infeasible |

## 6. Energy Closure Calculation

Required usable energy for 2.5 hr: `5.47 kW × 2.5 hr = 13.675 kWh = 13,675 Wh`.

| Chemistry | Usable Wh/kg | Battery mass (kg) | Battery mass (lb) | All-up MGTOW (lb) |
|---|---|---|---|---|
| Li-poly | 138 | 99.1 | 218.5 | 230.1 |
| Li-ion NMC | 172 | 79.5 | 175.3 | 186.9 |
| Si-anode Li-ion | 206 | 66.4 | 146.4 | 158.0 |
| Li-S | 275 | 49.7 | 109.6 | 121.2 |
| Solid-state (projected) | 310 | 44.1 | 97.2 | 108.8 |

Even the most optimistic *projected* chemistry requires roughly **97 lb of battery** and lands at an all-up weight near **109 lb** — more than five times the Group 1 ceiling and well into Group 4 territory. The all-electric Group 1 concept does not close by any margin.

There is also a feedback penalty not captured above: adding battery mass increases hover power, which increases the energy required, which increases battery mass. The figures in §6 understate the true infeasibility because they hold hover power fixed at the 17 lb estimate rather than iterating to convergence.

## 7. Sensitivity

Reducing the endurance requirement to 1.0 hr with current Li-ion still requires ~70 lb all-up. Halving the payload and avionics loads changes the battery requirement by less than 5% because hover power dominates. The conclusion is insensitive to reasonable variation in the secondary assumptions: **hover power, not payload, is the binding constraint, and no battery chemistry resolves it within Group 1 mass.**

## 8. Recommendation

1. Abandon the all-electric Group 1 concept. It is not feasible at the required endurance.
2. Adopt a series-hybrid architecture: a fuel-burning turbogenerator provides continuous electrical power; a small hybrid energy buffer (battery + supercapacitor) covers transients and emergency reserve. This decouples endurance from battery mass — endurance scales with fuel mass, which is far lighter per unit energy than batteries.
3. Reclassify the air vehicle to Group 2 (21–55 lb MGTOW). Size structure and rotor to a 55 lb ceiling for growth and variant flexibility; operate at 43–45 lb nominal.
4. Carry the buffer battery sized only for engine-out reserve and transient absorption, not for full-mission energy.

## 9. Revision History

- **v1.0 (3 June 2026):** Initial trade study. Demonstrates all-electric Group 1 infeasibility across five battery chemistries; recommends series-hybrid Group 2 architecture. Drives ORL Section 4 class assignment.