Lighting System

ABSTRACT

Luna’s lighting system is designed to deliver 100,000 lumens of high-quality, diffused light from an elevated position. This page details the optical modeling, LED selection, and the advantages of our balloon-based diffusion approach over traditional point-source towers.

Optical Model

The core advantage of Luna is its geometry. By elevating the light source and using the balloon envelope as a diffuser, we create a “soft light” effect that covers a large area without the harsh glare and deep shadows associated with traditional light towers.

Illuminance Distribution

We model the light source as a point emitter at height $h$ with a conical beam of half-angle $\alpha$. The illuminance $E$ (in lux) at a ground point $(x,y)$ is calculated using the inverse square law with cosine correction for the angle of incidence.

$E(x,y)=\frac{\Phi \cdot h}{4\pi (x^2+y^2+h^2{)}^{3/2}}$

Where:

• $\Phi$ = Total Luminous Flux (lumens)
• $h$ = Height of the balloon (meters)
• $r=\sqrt{x^2+y^2}$ = Horizontal distance from center

Coverage Area vs. Height

A key finding from our Optical Model simulations is that height matters more than raw power for area coverage.

For a target illuminance of 10 lux (sufficient for construction safety):

• Traditional Tower (4m height): Covers a small, intensely lit circle. Light drops off rapidly.
• Luna (20m height): Covers a much larger radius with more uniform light.

Height (m)	10 Lux Radius (m)	Area ($m^2$)	Uniformity
5	~10	~314	Poor (Hotspot)
10	~18	~1000	Good
20	~25	~1960	Excellent
30	~28	~2460	Excellent

NOTE

Luna illuminates nearly 6x the area of a standard 5m tower for the same power output, simply by virtue of geometry.

LED Module Specification

To achieve our target of 100,000 lumens (100 klm) while staying within our weight and thermal budgets, we require high-efficiency LED modules.

Requirements

• Total Flux: $\ge 100,000$ lm
• Efficacy: $\ge 180$ lm/W (to minimize heat)
• Power: $\approx 600$ W total
• Weight: Minimal (no heavy heatsinks)
• Form Factor: Exposed PCB for helium cooling

Selected Component: TCI SML280

We have identified the TCI SML280 (or similar high-density LED boards) as a primary candidate.

• Type: Linear / Rectangular LED Engine
• Efficiency: High efficacy suited for industrial applications
• Origin: Made in Italy (aligns with supply chain preference)

Configuration

• Array: 3 to 4 modules mounted on a lightweight aluminum frame.
• Orientation: Downward-facing.
• Control: Dimmable drivers located at the ground station (to reduce balloon weight) or lightweight DC-DC converters onboard.

Diffusion Strategy

The quality of light is determined by the envelope material. We use a hybrid Mylar strategy:

1. Upper Hemisphere: Aluminized Mylar.

   • Acts as a reflector, bouncing upward-emitted light back down.
   • Prevents light pollution (sky glow).
   • Increases effective downward flux.

2. Lower Hemisphere: High-Haze Transparent Mylar.

   • Haze: 80-90%. Scatters light to soften shadows.
   • Transparency: High transmission to minimize absorption loss.
   • Acts as a large “softbox,” increasing the apparent size of the light source to reduce glare.

Comparison with Competitors

Feature	Luna	LuxTower / Traditional	AirStar (Film)
Source Size	Large (Balloon $\approx 2m\oslash$)	Small (Lamps)	Large
Glare	Low	High	Low
Shadows	Soft / Filled	Hard / Sharp	Soft
Color	Customizable (RGB option)	Fixed White	High CRI (Film)
Efficiency	190 lm/W	80-120 lm/W	Variable

Smart Features

The lighting system is integrated with the Safety System:

• Thermal Throttling: If internal temperatures rise, LEDs automatically dim to reduce heat.
• Emergency Signaling: In case of communication loss or critical error, the lights can flash a distress pattern.
• Zone Control: Potential to switch off individual panels to shape the beam (e.g., 180° lighting).

See Thermal Management to understand how we cool these high-power LEDs using helium.