## 3 Thermal Control System Scheme and Unit Design  
### Framework and Scheme  
As shown in Figure 3, a three-stage thermal control system based on single-phase fluid loop was constructed to solve the problem of diversified thermal management of the payload inside the module of CSS. Firstly, the liquid-liquid heat exchanger provided by the platform is used as the heat sink of the thermal control system, and the fluid loop drive unit is used as the circulating power to construct the bus-type fluid pipe network in the module. A first-level thermal control bus (TCB) for the module is constructed, which conveys the cooling fluid (36% ethylene-glycol) to each payload rack; after the load heat is collected, it is conveyed to the Fluid Drive unit through a fluid pipeline network; finally, the heat is transferred to the thermal control loop of the aircraft platform by the liquid-liquid heat exchanger.  
According to the payload racks, second-stage thermal control systems are built based on the liquid-cooled resources provided by first-stage TCB. Four kinds of thermal control management units of rack are designed: (a) liquid-cooled thermal control terminal,  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Name** & **Description** & **Type 1 \({}^{*}\)** & **Type 2 \({}^{*}\)** & **Type 3 \({}^{*}\)** \\ \hline \multirow{2}{*}{Payload layout} & \multirow{2}{*}{Layout Feature} & Centralized and regular layout & Large enclosed space, small-size discrete distribution & Special-shaped layout, personalized layout \\ \hline Heat consumption & Indicators (W) & \textless{}300 W & 300–1000 W & 1000–2300 W \\ \hline \multirow{2}{*}{Tem Stability} & Indicator (\({}^{\circ}\)C/h) & \(\pm 5\,^{\circ}\)C/h Electronics equipment & \(\pm 0.5\)-\(1\,^{\circ}\)C/h Optical load & mK/h Basic physical load \\ \hline \multirow{2}{*}{Tem level} & Indicators (\({}^{\circ}\)C) & \(-10\)–\(45\,^{\circ}\)C Electronics equipment & 0–\(10\,^{\circ}\)C Low-temperature load & \(4\,^{\circ}\)C, \(-20\,^{\circ}\)C, \(-80\,^{\circ}\)C Biological sample \\ \hline \multirow{2}{*}{Tem Uniformity} & \multirow{2}{*}{/} & No special needs & \(\
ot\succ 5\,^{\circ}\)C & \(\
ot\succ 10\) mK \\ \hline \multirow{2}{*}{Mode of operation} & \multirow{2}{*}{/} & Continuously & Discontinuous & Monorail time-sharing work \\ \hline \multirow{2}{*}{Other constraints} & \multirow{2}{*}{/} & \multirow{2}{*}{Contact heat transfer} & Non-contact heat transfer & Heat transfer without disturbance \\ \hline \hline \end{tabular}  
* The longitudinal load characteristics of the rack do not match; all kinds of load characteristics are cross-distributed.  
\end{table}
Table 1: Heat source characteristics and temperature control requirements inside the rack.  
Figure 3: Topological structure of integrated thermal management system.  
(b) gas-liquid thermal control terminal, (c) secondary fluid loop terminal and (d) multi-stage thermal control terminal. According to the thermal control demands of different racks, the thermal control terminal carries on the overall thermal control management regarding the rack and realizes the medium and heat exchange with the TCB. The product architecture of the thermal management system is shown in Figure 4:  
Different modules of CSS adopt a unified thermal control design framework; each module is equipped with different thermal control terminals according to the number and type of actual payload rack; the fluid drive unit and thermal control terminals have a unified design.