Centradiant LDR Architecture

A spinning disk liquid droplet radiator that achieves 4.4 kg/kW(th), 6–8× lighter than conventional panel radiators. Centrifugal force drives passive droplet collection with zero parasitic power.

Centrifugal Droplet Collection

A 10m radius flat spinning disk sprays hot CB-DC705 fluid as 377μm droplets into the vacuum of space. At 2 RPM, centrifugal acceleration (0.045g at the rim) drives droplets radially outward into a peripheral mesh collector requiring only 94 m² of capture area and 19 kg of Ti-6Al-4V mesh. No electromagnetic steering, no electrostatic charging, no parasitic collection power.

934 kg launch mass 4.4 kg/kW(th) specific mass 55 kW thermal rejection

Disk Architecture

Geometry

10m radius flat disk, 2 RPM
6 CFRP spokes with tensioned mesh
Rim collector channel (annular trough)
0.045g centripetal acceleration at rim
Effective radiating area: 94 m² (both faces)

Fluid Loop

CB-DC705: DC-705 + 100 ppm carbon black
27,248 laser-drilled SS nozzles (200μm) → 377μm drops
Rayleigh breakup: d_drop = 1.88 × d_nozzle
PCHE: 2,000 × 3.0mm × 100cm semicircular channels
Galinstan thermal rotary joint (no fluid seal)

Key Metrics

934

kg launch mass

812 kg dry + 15% margin

4.4

kg/kW(th) LDR specific mass

6–8× lighter than panels

kW thermal rejection

64× H100/B200 GPUs

34.2°C

T_j margin

vs 83°C GPU limit

61.7%

5-year reliability

all subsystems included

kg mesh (Ti-6Al-4V dual-layer)

13× reduction

Mass Budget

Subsystem	Mass (kg)	Fraction
Power System (solar + PMAD + battery)	218.5	27.4%
Thermal, Rotating (PCHE, mesh, nozzles, fluid)	164.5	20.3%
Compute Payload (64× GPU + 8mm Al shielding)	118.9	14.9%
LDR Structure (spokes, hub, rim)	74.0	9.3%
Structure & Mechanisms	50.0	6.3%
Thermal, Rotary Joint (Galinstan)	26.6	3.3%
ADCS & Propulsion	18.0	2.3%
Avionics & Comms	11.3	1.4%
Thermal, Bus Side	9.5	1.2%
DRY MASS	812 kg	100%
System Margin (15%)	122 kg	–
LAUNCH MASS	934 kg	–

Deployment Sequence

Step 1

Separation & Despun. Spacecraft separates from launch vehicle; reaction wheels despin to stable attitude

Step 2

Spoke Deployment. 6 CFRP spokes unfurl radially (solar sail heritage, 2D deployment only)

Step 3

Mesh Tensioning. Dual-layer Ti mesh stretched between spokes; rim collector channel seats

Step 4

Spin-Up. Motor brings disk to 2 RPM; centripetal field established at 0.045g rim acceleration

Step 5

Fluid Activation. CB-DC705 pumped through Galinstan joint; nozzles fire; droplet cloud established; thermal rejection begins

Capture Physics

The critical dimensionless parameter for mesh capture is the Weber number (We = ρv²d/σ), which determines whether a droplet is captured or splashes on impact.

We ≈ 58

At mesh impact

>99.99%

Per-cycle capture efficiency

5 kg

5-year evaporation loss (5%)

Dual-layer Ti-6Al-4V mesh with oleophilic coating captures >99.99% of impinging droplets per cycle. Gutter channels drain collected fluid to spoke return paths, completing the recirculation loop.

Competitive Specific Mass

Technology	kg/kW(th)	Notes
Centradiant LDR	4.4	LDR subsystem only
Deployable fin radiators	15–25	Best traditional option
Body-mounted panels (ISS-style)	25–35	Mature, very heavy
Electromagnetic LDR	20–30	30 years of failed attempts

Launch Vehicle Compatibility

At 934 kg, the D3 fits comfortably on a Falcon 9 rideshare (5.1% utilization), Rocket Lab Neutron (11.5%), or PSLV-XL (52.3%). The only excluded option is Electron (300 kg max). Starship opens multi-satellite deployment.

Ground Prototype Design →