Flow Control Valves
Thermal Loop Flow Control and Isolation Valve Assemblies
Thermal loop flow control and isolation valve assemblies are motorized and manual mechanical components that regulate fluid flow paths, rates, and loop configurations throughout lunar thermal networks. Across the 354-hour lunar day-night cycle, valve positions continuously adjust to transition transport loops between daytime cooling and nighttime heating modes. Diverter valves route working fluid away from radiators to prevent freezing during the lunar night, while stepper-motor-driven proportional valves modulate flow with position resolution better than one percent. Lunar operations require vacuum-compatible seal materials resilient to extreme temperatures, alongside sealed actuator motor housings designed to exclude abrasive lunar dust.
Motorized and manual valves that control fluid flow paths, rates, and loop configurations including proportional flow control valves, diverter valves, isolation valves, and check valves throughout the thermal transport network.
Purpose
Enable dynamic reconfiguration of fluid loop topology to adapt to changing thermal conditions. Proportional valves modulate flow to individual branches for temperature control. Diverter valves route fluid between radiators and bypass paths. Isolation valves enable component replacement and fault isolation. Check valves prevent reverse flow in parallel-pump configurations.
Context
Valves are the actuators through which L2-TCS-CTRL exercises thermal management authority. During the 354-hour lunar day/night cycle, valve positions continuously adjust to shift heat transport between daytime cooling and nighttime heating modes. Radiator bypass valves prevent fluid freezing in stagnant radiator tubes during lunar night. Isolation valves at every maintenance interface enable robotic component swap without full loop drain-down.
Principles
- ▸Proportional control valves modulate flow via variable orifice area, enabling continuous thermal control authority
- ▸Three-way diverter valves split flow between active and bypass paths: critical for radiator freeze protection
- ▸Ball valves provide low-pressure-drop isolation with positive shutoff for maintenance operations
- ▸Check valves prevent reverse flow through standby pumps or failed loop segments
- ▸Valve actuators (stepper motor, solenoid, pneumatic) must be vacuum-compatible and radiation-tolerant
Typical implementations
- ▸ISS ETCS ammonia flow control valves: motor-driven ball valves with 0-100% proportional control
- ▸ISS ETCS isolation valves: manually-operated (EVA) quarter-turn ball valves for ammonia loops
- ▸Orion MPCV three-way mixing valves for coolant temperature control
- ▸Satellite thruster latch valves adapted for thermal control fluid isolation
Lunar considerations
- ▸Valve seat and seal materials must not degrade over 100 years in contact with working fluid at extreme temperatures
- ▸Stepper motor actuators preferred for proportional valves: precise positioning, holdable without power, vacuum-compatible
- ▸Fail-safe positions must be defined for each valve: loss of power should drive valves to thermally safe state
- ▸Lunar dust exclusion at valve actuator interfaces critical: sealed motor housings required
- ▸Valve cycling frequency of 2500+ full day/night cycles over 100 years plus continuous modulation requires high-cycle-life seat materials
Specifications
Functional
| primary function | Control fluid flow paths, rates, and loop configurations to enable thermal mode management and component isolation |
| inputs | Position commands from L2-TCS-CTRL (proportional valves, diverters), Open/close commands for isolation valves, Electrical power for valve actuator motors |
| outputs | Modulated fluid flow in controlled branches, Valve position telemetry (percent open, fully-open/closed status), Flow isolation for maintenance operations |
| proportional valve resolution pct | Better than 1% of full travel |
| isolation valve leakage | Zero through-leakage at rated differential pressure |
| response time seconds | <5 seconds for full stroke proportional, <2 seconds for isolation valve close |
| cycle life | >100,000 full cycles for proportional valves, >10,000 for isolation valves |
Physical
| materials | Stainless steel 316L (valve bodies, ball elements), Stellite 6 (valve seats for wear resistance), PTFE / PEEK (soft seal elements), Stainless steel (actuator housings), Neodymium magnets (stepper motor rotors) |
| operational temp range c | -80, 80 |
| survival temp range c | -173, 127 |
| vacuum compatible | True |
Operational
| thermal range c | -80, 80 |
| lifetime years | 50 |
| mtbf hours | 100000 |
| notes | Stepper motor valves hold position without power. Power consumed only during repositioning. Estimated 1-10W per valve during actuation. Valve assemblies are robotically replaceable LRUs. |
Interfaces
Provides
- Flow control and routing authority for all fluid loop branches, enabling thermal mode transitions
- Isolation capability for pump maintenance: upstream/downstream shutoff enabling pump cartridge swap
Requires
- Valve position commands, mode selection, and fault response directives
- Electrical power for valve actuator motors during repositioning
- Robotic access for valve replacement and manual override operations
Cite this entry
Lunar Ark Codex. "Flow Control Valves" (L3-TCS-FLOP-VALV). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-TCS-FLOP-VALV
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.