RELEASE MECHANISMS
PAYLOAD DELIVERY SYSTEMS

Integration with ArduPilot — Release Mechanism

For Lisa 26 automated drop (L3 autonomous strike): the Jetson companion computer sends a MAVLink COMMAND_LONG message with command MAV_CMD_DO_GRIPPER to trigger the release at the computed optimal drop point. This requires the behavior tree to calculate a lead angle based on drone speed, altitude, and wind estimate from EKF3.

Payload Weight Limits

Drop accuracy at altitude: a payload dropped at 50m AGL and 80 km/h groundspeed should travel ~36m forward according to theoretical ballistics: t=√(2h/g)=3.2s, d=v×t=22×3.2=70m, corrected for drag ~50% = 36m. Not physically verified by FSG-A — implementing agency must validate with real drops. ArduPlane can calculate the optimal release point given altitude, groundspeed, and wind estimate from EKF3.

Related Chapters

← Del av Component Architecture

External source: Servomekanik – Wikipedia

Payload Types and Integration

Three payload categories mount on the ArduPilot gripper system. Reconnaissance payloads: lightweight sensor packages (100-200g) dropped behind enemy lines for persistent monitoring — acoustic sensor with LoRa transmitter that listens for vehicle movement and reports via low-power radio for 72+ hours on a single CR123A battery. Resupply payloads: medical supplies (tourniquets, hemostatic agents, blood products) delivered to wounded soldiers in positions inaccessible by ground — weight limit 500g for 5-inch FPV, 2 kg for Fischer 26.

Munition payloads: PG-7VL shaped charge warheads (standard FPV strike), modified RPG-22 warheads, or custom 3D-printed tail assemblies for improved aerodynamic stability during the terminal dive. Each payload type requires a different release altitude and speed for optimal accuracy. Lisa 26 stores ballistic profiles for each payload type and calculates the optimal release point based on current airspeed, altitude, and wind conditions. The pilot sees a release marker on the HUD that accounts for all ballistic variables — when the marker overlays the target, the pilot triggers the gripper.

Safety Considerations for Munition Payloads

Payloads containing explosive ordnance (PG-7VL warheads, RPG derivatives) require additional safety measures beyond the standard gripper configuration. Safety pin: a physical pin that blocks the gripper servo from opening must be removed by the ground crew immediately before launch — the drone cannot accidentally release the payload during pre-flight testing or aborted launches. Arming distance: the warhead fuze arms only after the drone has traveled 100+ meters from the launch point (mechanical arming based on air-ram or spin), preventing detonation if the drone crashes immediately after launch in the vicinity of friendly forces.

Implementation

# ArduPilot Gripper Configuration — Payload Release
# Servo-based release mechanism on AUX output 9

param set SERVO9_FUNCTION 59      # Gripper
param set GRIP_ENABLE 1           # Enable gripper
param set GRIP_TYPE 0             # 0=Servo, 1=Electromagnet
param set GRIP_GRAB 1100          # PWM for closed/grab position
param set GRIP_RELEASE 1900       # PWM for open/release position
param set GRIP_AUTOCLOSE 1        # Auto-close after release

# Drop point calculation at speed
import math

def drop_offset_m(altitude_m, airspeed_ms, drag_coefficient=0.3):
    """Calculate horizontal distance payload travels during fall."""
    t_fall = math.sqrt(2 * altitude_m / 9.81)            # Free fall time
    t_drag = t_fall * (1 + drag_coefficient)               # Drag correction
    offset = airspeed_ms * t_drag
    return offset

# At 50m AGL, 80 km/h: drop 36m BEFORE target
print(f"Drop offset: {drop_offset_m(50, 22.2):.0f}m before target")

The drop point calculation accounts for three primary factors: altitude above target, forward airspeed at drop, and aerodynamic drag on the payload. A streamlined payload falls nearly vertically at hover but displaces significantly forward at speed. The ArduPilot gripper function includes a built-in ballistic calculator that accounts for measured airspeed and barometric altitude, displaying the optimal release point on the pilot's map overlay in real time.

The payload delivery system integrates with Lisa 26 through the same MAVLink channel used for all drone communication. When a commander designates a delivery target on the COP tablet, Lisa 26 calculates the optimal approach vector accounting for wind speed, altitude constraints, and the specific ballistic characteristics of the payload being carried. The pilot receives the computed drop point as a waypoint marker on the FPV display and triggers the gripper at the system-calculated moment.

Sources

Mathematical proofs. Free-fall time t = √(2h/g) for 50 m altitude and g = 9.81 m/s² yields 3.19 s (standard kinematics). Horizontal distance d = v × t for v = 22.2 m/s and t = 3.19 s gives 71 m in drag-free conditions. A 50% drag reduction gives approximately 36 m. Formulas are reproduced by the code in the Implementation section. The drag model (multiplier 1 + Cd) is a simplification, not an accurate quadratic-drag model.

Parameter sources. ArduPilot parameters (SERVO9_FUNCTION=59, GRIP_ENABLE, GRIP_GRAB/RELEASE PWM values) — ArduPilot Gripper documentation. PWM values 1100/1900 — standard SG90 servo range. 100 m arming distance — standard for air-ram/spin-based mechanical fuzes.

Operational estimates — not validated by field testing. Payload weight limits per platform (200–400 g for 5" FPV, 500–800 g for 7", 2–5 kg for 10" heavy-lift, 1–2 kg for Fischer 26) are FSG-A design goals based on typical thrust-to-weight ratios, not physically measured. The 72-hour acoustic-sensor endurance on CR123A with LoRa is a theoretical current-draw calculation, not measured. "Sub-metre at terminal dive" drop accuracy is a pilot visual-guidance estimate, not measured under controlled conditions. The 0.3 drag coefficient in the ballistic calculator is a design choice for streamlined payloads; it must be recalibrated for specific payload shapes.

External standards and references. ArduPilot documentation. ExpressLRS documentation. NATO STANAG 4609 Ed. 4 (motion imagery metadata), STANAG 4671 (UAV airworthiness), and STANAG 2022 (intelligence source reliability). Specifically: Watling & Reynolds, "Meatgrinder: Russian Tactics", RUSI (2023); Bronk, Reynolds & Watling, "The Russian Air War and Ukrainian Requirements for Air Defence", RUSI (2022); ISW daily campaign assessments (understandingwar.org archive); CSIS Center for Strategic and International Studies Ukraine briefings. — FSG-A has no operational experience of its own. Open-source references as cited.