Overview
In vacuum, conduction and convection are unavailable as external channels — thermal radiation from a surface is the only way to dispose of heat. This single-channel constraint makes the radiator a defining element of spacecraft architecture rather than an auxiliary component, and it accounts for 40 % or more of the power-unit mass of nuclear-electric spacecraft. State-of-the-art panels remain at 5.8–7.16 kg/m² against programme targets below 3 kg/m².
ARBIATOR replaces the panel assembly with a material. Thermally expanded graphite sprayed onto any surface behaves as a near-ideal black body: infrared emissivity above 0.9 and up to 0.99 in optimized forms, in-plane thermal conductivity of 100–470 W/m·K so the whole surface radiates rather than a hot spot around the interface, and bulk density of 0.002–0.02 g/cm³ — only 1.5–2 times the density of air. The radiator stops being a deployable subsystem and becomes a surface property of the spacecraft.
Applications
Nuclear-electric propulsion. All non-thrust power becomes heat in converters, power electronics and thrusters, and must be rejected continuously over months. With heat rejection at 40 %+ of power-unit mass, TEG-based rejection is a direct enabler.
Communication and navigation constellations. Serial spacecraft gain spray-applied radiator surfaces with no deployment mechanics, and material supply matched to constellation-scale production.
Orbital computing platforms. The authors hold a critical position on the thermal premise of "space cooling" for data centres; nevertheless any such platform, if built, is limited by its radiators, and a near-ideal emitter with minimal areal mass is the least implausible way to build them.
Small spacecraft. For CubeSats and nanosatellites the same TEG plate combines heat rejection with the evaporative recoil micro-thruster function of Arbok-NANODRIVE, cutting subsystem count on mass-constrained platforms.
Extended concepts. Pore impregnation with in-situ resources — asteroid or lunar water ice, ammonia — links thermal architecture to ISRU logistics; scalability runs from nanosatellites to interplanetary vehicles and solar sails with evaporation-based thrust control.
Operating Principle
Radiated power follows the Stefan–Boltzmann law, scaling with the fourth power of absolute surface temperature. This creates a design fork: low radiator temperatures demand large areas, while compact radiators must run at hundreds of degrees, stressing adjacent electronics.
TEG is produced from oxidized natural graphite by rapid thermal expansion, yielding a vermicular, thoroughly porous structure. Radiation entering the pore network is trapped by multiple internal reflections and the probability of photon escape approaches zero — absorption reaches 99 % across ultraviolet, visible and infrared. Where conventional radiator coatings are engineered for incremental emissivity gains, in TEG high emissivity is a property of the material structure itself.
In-plane conductivity of 100–470 W/m·K spreads waste heat across the full panel area instead of concentrating it around the thermal interface, so the entire surface radiates.
The material is applied by spray coating onto rigid, flexible or foldable structural surfaces — a separately solved deposition task supported by several proprietary know-hows. The open pore network allows optional integration with heat pipes and capillary wicks. A damaged radiator is restored by re-spraying rather than replaced by sections.
Limitations: system-level maturity is TRL 3; direct system comparison awaits prototype validation, thermal-vacuum testing, orbital demonstration and certification.
Key Parameters
| Parameter | ARBIATOR (TEG) | Conventional panel |
|—|—|—|
| Infrared emissivity | >0.9, up to 0.99 (inherent to structure) | set by applied coating |
| In-plane thermal conductivity | 100–470 W/m·K | localized around interface |
| Bulk material density | 0.002–0.02 g/cm³ (1.5–2× air) | aluminium/composite |
| Areal density | dominated by substrate and integration | 5.8–7.16 kg/m² |
| Programme target for comparison | — | below 3 kg/m² at 500–600 K |
| Heat rejection share of NEP power-unit mass | — | 40 % or more |
| Absorption across UV–VIS–IR | up to 99 % | — |
| Specific surface area | tens to hundreds of m²/g (1 g ≈ a tennis court) | — |
| Service life | 25–50+ years (5–10× conventional) | degrades under UV, cycling, impact |
| Deployment mechanics | none — sprayed on structure | hinges, drives, fluid couplings |
| Repair | re-spraying | section replacement |
| Material usage rate | 3–5 kg/m² of active surface | — |
TEG production:
| Parameter | Value |
|—|—|
| Output per unit | up to 1,000 kg/h (~24 t/day) |
| Material cost | ~$50/kg |
| Historical laboratory cost | $15–20 per gram (~3,000× more) |
| Purity | 99.99 % |
| Surface covered per unit per day | 5,000–8,000 m² |
Architecture and Components
TEG emissive layer sprayed onto structural surfaces; thermal-spreading pathways exploiting in-plane conductivity; optional integration with heat pipes and capillary wicks through the open pore network. No dedicated panel substrates, no hinges, no drives, no flexible hydraulic couplings, no ammonia heat-pipe network.
The porous structure permits functional combination within a single element: the same plate serves as radiator, as heat-pipe or wick medium, as micrometeoroid buffer, and as the Arbok-NANODRIVE evaporative thruster.
Advantages
Physical: emissivity approaching the black-body limit as a structural property rather than a coating; full-surface emission through high in-plane conductivity; density 1.5–2 times that of air.
Reliability: reduced deployment mechanics removes entire failure classes rather than mitigating them. Conventional designs require redundancy against puncture because a single breached heat pipe can disable a whole section — a reliability-mass feedback loop where redundancy adds mass and mass constrains the mission. Service life 25–50+ years against conventional systems, a 5–10× increase; in vacuum the primary terrestrial degradation mechanism, oxidation at elevated temperature, is absent.
Economic: radiator mass reduction of several times acts on launch cost independently of launcher progress.
Architectural: multifunctional surface combining radiator, shielding and thruster functions, reducing subsystem and interface count.
Integrations
Arbok-BlackBody System (ABBS) — Kirchhoff-dual counterpart. By Kirchhoff's law spectral absorptivity equals spectral emissivity at thermal equilibrium: a near-ideal absorber is a near-ideal emitter. ABBS exploits the absorptive side for full-spectrum solar capture at 1–3 kg/m² system mass against 10–20 kg/m² for space-grade photovoltaics; ARBIATOR exploits the emissive side. A single TEG-coated surface can therefore act as energy absorber on the illuminated side and heat-rejection radiator on the shadow side — absorption, redistribution and emission become properties of one material rather than three subsystems, substantially reducing the distinction between "solar array", "radiator" and "structure".
ARBOK-NANODRIVE — evaporative recoil micro-thruster on the same TEG plate.
AEROGRAPH (Graphene AeroGel) · MAGNA (Metal-Graphene) · ARBOK EMI TEG Protection Paint
Deployment & Operation
Applied as a spray coating directly onto existing spacecraft structure — rigid, flexible or foldable — without dedicated panel substrates. Operates as a passive or semi-active radiator in high-temperature regimes. Maintenance by re-spraying rather than sectional replacement.
Commercial model: 15–20 year off-take agreement supplying TEG against constellation schedules; licensing of the spray-coating technology to satellite-platform integrators; thermal-design services delivering radiator, thruster and shielding in one surface.
Development path to higher TRL: prototype integration, thermal-vacuum testing, orbital demonstration, certification.
TRL
TRL 3 at system level. Material properties — absorption and emission characteristics, thermal transport — validated at laboratory level, and the underlying TEG material is in industrial production. System-level validation remains outstanding.
Market Potential
Launch cost runs from approximately $1,000/kg on high-volume launchers to $2,000–10,000/kg depending on mission conditions, with industry estimates placing the viability threshold for large orbital infrastructure near $200/kg. Radiator mass reduction acts on the numerator of that economy independently of launcher progress.
Demand drivers: national programmes have announced nuclear-electric missions on accelerated timelines, and multiple commercial filings propose large orbital computing constellations whose thermal budgets would require radiating surfaces measured in square kilometres. On the ground, the data-centre cooling market is growing from $16.84 billion to $42.48 billion per year between 2024 and 2032.
Supply is not a constraint: at 3–5 kg/m² usage and 1,000 kg/h output, one production unit covers 5,000–8,000 m² of active surface daily, or millions of square metres annually — enough for constellation programmes of tens of thousands of spacecraft.
Typical Project Economics
ABBS reference case, illustrating the scale of the effect:
| Item | Value |
|—|—|
| Conventional solar arrays for a large orbital system | ~30,000 kg |
| Equivalent TEG-based system | 500–1,000 kg |
| Mass reduction | up to 29,000 kg |
| Launch cost saved per deployment | $58–290 million |
Analogous logic applies to heat-rejection surfaces of comparable area. Given the 40 %+ mass share of heat rejection in NEP power units, a several-fold reduction translates directly into mission-level gains: the same mission on a smaller launcher, or a multiplied payload fraction on the same launcher.
Production economics: ~$50/kg against a historical laboratory cost of $15–20 per gram — roughly a 3,000× reduction.
Risk Factors
System-level maturity is TRL 3. Direct system comparison against conventional panels awaits prototype validation. Prototype integration, thermal-vacuum testing, orbital demonstration and certification all remain ahead.
Related Technologies
Arbok-BlackBody System (ABBS) · ARBOK-NANODRIVE · AEROGRAPH (Graphene AeroGel) · ARBOK-Stellar · LunaLand