SmallSat Thermal Control

As SmallSats undertake increasingly complex missions, their power requirements and heat outputs must be adjusted accordingly. Electric propulsion systems, high-bandwidth communications, and other high-power devices are pushing the limits of conventional thermal management technologies. This necessitates improved thermal management systems that are lightweight, compact, and highly reliable.

The LGST Lab is developing a range of next-generation SmallSat thermal control technologies to address anticipated bottlenecks in heat transfer and rejection. Below, we offer a summary of projects that have focused our efforts in recent years.

Liquid metal cooling loops

In contrast to Mechanically-Pumped Fluid Loops (MPFL), magnetohydrodynamic (MHD) liquid-metal loops do not require moving parts to operate, thereby reducing the number of failure modes in the heat-transport architecture and simplifying its operation. The high thermal and electrical conductivity and low vapor pressure of liquid metals lead to lighter heat exchangers and power requirements of the order of tens of mW, ultimately reducing the mass per unit of transferred heat. As of today, we have demonstrated heat-transfer rates of up to 13.8 W/K with laboratory prototypes.

Journal Articles:

Conference Papers & Presentations:

Patents:

  • Á. Romero-Calvo, “Magnetohydrodynamically Pumped Liquid Metal Loops for Spacecraft Thermal Control”, US Application No. 63/504,558, May 2023.

Electromagnetic droplet radiators

The heat-rejection rate of body-mounted thermal radiators is limited by surface area, whereas state-of-the-art deployable units exhibit high thermal resistance at the hinge. These features are expected to impose significant constraints on thermal management as power budgets continue to increase.

Based on research conducted at NASA Glenn Research Center, our lab has recently introduced the magnetic droplet radiator (MDR) as a low-mass, high-power alternative to state-of-the-art heat-rejection systems. The MDR combines heat transport and rejection processes within a closed-loop thermodynamic cycle, in which the working fluid serves as the thermal medium. Heated droplets are ejected through a micrometer injector toward a low-temperature collector that gathers the liquid. A mechanical pump is incorporated to pressurize the fluid and sustain the cycle.

We have explored the design trade space of the MDR by addressing relevant material compatibility, thermal performance, magnetic collection, and environmental processes. Results reveal that a maximum heat-rejection rate of 450 W can be achieved with a 0.5-kg, 2-m-long droplet sheet, requiring less than 200 mW of power. The specific mass and mass-to-heat ratio of the radiator range from 0.45 to 1.2 kg/m2 and 1.1 to 2.8 kg/kW, respectively, depending on the trade between mass, power consumption, and maximum allowable slew rate. Unlike traditional liquid droplet collectors, the magnetic collection system is robust to perturbations caused by atmospheric drag, solar radiation pressure, axial thrust, and even 15 mrad/s ground-tracking slew rates across a wide range of designs. Together, these results position the MDR as a significantly lighter and more powerful alternative to existing deployable radiators, thereby enabling high-power small-satellite architectures.

Journal Articles:

  • R. Alotaibi, P. Martín García, Á. Romero-Calvo, “Magnetic Droplet Radiator for CubeSat Heat Rejection”, AIAA Journal of Spacecraft and Rockets, under review