# Presentation: 904651

## AMS-02 Thermal Control System (TCS)

## AMS-02 Thermal Overview

- Payload nominally dissipates 2400 watts (2800 watts peak) when fully operational
- Thermal Design Goals
- Maintain all experiment components and sub-detectors within specified operating and survival limits (document in AMS-02 Thermal ICD)
- Maximize Super Fluid Helium (SFHe) endurance
- Optimize sub-detector temperatures to maximize science

## AMS-02 TCS Hardware

- Radiators
- Heaters
- Thermal Blankets
- Loop Heat Pipes (LHP’s)
- Cryocoolers
- CAB
- Standard Axial Groove Heat Pipes
- 2-Phase CO2 pumped loop
- Surface Optical Coatings

## Radiators

- AMS-02 radiators include
- Main Radiators (Ram and Wake)
- Ram radiator dissipates heat from electronic crates (up to 525 watt)
- Wake Radiator dissipates heat from electronic crates and the PDS (up to 812 watt)
- Tracker Radiators (Ram and Wake)
- Tracker radiators reject the 144 watt of the Tracker, transported by the TTCS
- Zenith Cryocooler Radiators (4 panels)
- Zenith panels radiate the power of 4 cryocoolers, 400W in total,  carried by 8 LHP

## Main Radiators Mounting

- Main Radiators are mounted directly to the crates, which in turn are attached to the USS-02

- Lower Brackets (4)

- Upper Brackets (4)

- Mid Bracket (4)

## Main Radiator Construction

- Radiators are a sandwich construction with Al face sheets and a ROHACELL®  core.
- Axial grooved heat pipes (aluminum filled with ammonia) are imbedded between face sheets.
- Chotherm 1671  is used as a thermal interface filler between crates and radiators.
- Radiators are painted with SG121FD white paint to optimize heat rejection.

## Slide 7

## Slide 8

## Tracker Radiators

- Ram and Wake Tracker Radiators are designed to reject the total heat generated inside the Tracker (144W).
- Heat is transported by the Tracker Thermal Control System (TTCS) which will be discussed later.

## Slide 10

## Tracker Radiator Construction

- Tracker Radiators are a sandwich construction with Al face sheets and a ROHACELL®  core.
- Heat pipes (aluminum filled with ammonia) are imbedded between face sheets.
- Chotherm 1671  is used as a thermal interface filler between condensers and radiators.
- Outer surface is painted with SG121FD white paint to optimize heat rejection.

## Slide 12

## Zenith Radiator

- The Zenith Radiator (4 separate panels) is design to reject the waste heat generated by the Cryocoolers (60-160W each).
- Heat is transported to each radiator panel via 2 Loop Heat Pipes (LHP’s) attached to a single cryocooler.
- The LHP’s utilize propylene as a working fluid which flows directly through aluminum tubes embedded in the Radiator.
- Aluminum tubes in the radiator transition to stainless steel tubes running to the evaporator via a bi-metallic joint.

## 4 Zenith Radiator Panels

## Zenith Radiator Construction

- Radiators are a sandwich construction with Al face sheets and a ROHACELL®  core.
- 3mm aluminum tubes are glued to upper face sheet, inside the sandwich
- Radiator panels are mounted to top of TRD Upper Honeycomb Panel via brackets and glass-fiber pins.
- Outer surface is coated with silver-Teflon.
- Multi-layer Insulation (MLI) is used between Radiator and TRD.

## Zenith Radiator Installation

## Multi-Layer Insulation (MLI) Blankets 

## Multi-Layer Insulation (MLI) Blankets

- Numerous components of AMS-02 will be covered with MLI blankets
- All blankets will meet NASA standards for grounding and venting, and will be constructed according to “MLI for AMS Guidelines” (CTSD-SH-1782)
- Typical construction will include multiple layers of aluminized Mylar separated by Dacron scrim.  Betacloth will protect exposed surfaces.

## Heaters

- Heaters on AMS-02 are primarily used to:
- Warm up components to “switch on” temperature after power outages (including initial turn-on).
- Maintain components above minimum operating limits during operation.
- System recovery in case of extended power outages in cold environments.
- Manage TTCS operation

## Heaters (continued)

- Most heaters are both thermostatically and computer controlled.
- Most heaters will not be operated on the ground
- Analyses have been performed to evaluate effect of “run away” heaters.
- All safety critical heaters are two-fault tolerant.

## Heat Pipes

- Standard axial groove heat pipes are used in several locations to help distribute heat
- All heat pipes are aluminum filled with high purity ammonia.
- Heat pipes are designed to survive freezing/thawing cycles

## Cryocooler Cooling

- Each of the 4 Cryocoolers dissipate up to 160W of heat in order to remove 4 – 10W of heat from the Cryomagnet system.
- Loop Heat Pipes (2 per Cryocooler) are used to transport this heat to the Zenith Radiator where it is rejected via radiation.
- The Loop Heat Pipes (LHP’s), provided by IberEspacio/Madrid, are similar to those successfully demonstrated as part of COM2PLEX flown on STS-107.

## Loop Heat Pipe System

## CAB Thermal System

- The Cryomagnet Avionics Box (CAB) is used to monitor and control the Cryomagnet.
- Heat dissipation can vary from 35W to 800W.
- Two Loop Heat Pipes (LHP’s) will transport heat from the CAB base plate to the outer skin of the Wake Radiator.

## CAB Thermal System

- LHP are similar to Cryocooler LHP’s, except that ammonia, rather than propylene will be used as the working fluid.
- A bypass valve on the LHP will be used to bypass the radiator if CAB temperature approach lower limits.

## Slide 26

## Conclusion (1/2)

- Extensive work has also been performed on the thermal design of other AMS-02  Detectors and subsystems not described here
- Designs include
- MLI
- thermal fillers
- thermal washers
- thermal optical coatings
- heaters and thermostats.

## Conclusion (2/2)

- Safety controls include:
- Restricted access to AMS-02 when it is charged, thus limiting risk of personnel contact with radiators.
- Design of TCS precludes hot spots.
- Most payload heaters will not be operated on the ground.
- All safety critical heaters are two-fault tolerant.

## Backup slides

## TYPICAL RADIATOR INSERTS

## TTCS Condenser Mounting Interface

## Zenith Radiator Cross-Section

- Radiator Mounting

- Radiator Cross-section

## MLI for AMS Guidelines

- Written by Crew and Thermal Systems Division (CTSD-SH-1782, September 30, 2005)
- Based on requirements from ISS, STS and MSFC
- Electrical Bonding and Grounding
- All blankets with surface area greater than 100cm2 will have at least  two (2) grounding assemblies.
- Resistance from aluminized surface to ground shall be less than (<)  5,000 Ohms
- Resistance from ground to spacecraft structure shall be less than (<) 1 Ohm

## Heater summary:

| Item | Quantity |
| --- | --- |
| RAM radiator | 19 |
| WAKE radiator | 13 |
| J-crate | 2 |
| JT-crate | 2 |
| JPD crate | 2 |
| Both Tracker radiators | 26 |
| TOTAL | 64 |

## Thermostats

- Heater circuits are thermostatically controlled:
- For a progressive heating of the radiator panel at the activation (close-on-rise)
- For avoid overheating of the radiator and the electronics
- For safety (i.e. to avoid excessive overheating of the heat pipes, containing pressurized ammonia)
- For power saving
- Once the temperature is reached there is no need to continue supplying power

## Safety thermostats assessment: RAM radiator results

- Max Design temperature is 114 °C
- Max reached temperature is 82°C.

## Safety thermostats assessment: WAKE radiator results

- Max Design temperature is 114 °C
- Max reached temperature is 103°C.

## Thermostats

- 166 thermostats, including spares.
- These thermostats are located on
- RAM radiator
- WAKE radiator
- Tracker radiators
- inside the PDS and
- on the JPD main wall feet.

## Thermostats quantities (including spares):

| Item | Quantity |
| --- | --- |
| RAM radiator | 49 |
| WAKE radiator and PDS | 63 |
| PDS interlock | 10 |
| JPD | 10 |
| Tracker radiator | 34 |
| TOTAL | 166 |

## LHP Configuration

- Each LHP has a vapor line running to the Zenith Radiator and a liquid line returning.
- Lines in and out of the evaporator are stainless steel tube.  These tubes transition to aluminum tubes at the edge of the Zenith Radiator via a bi-metallic joint.
- “Pumping” pressure is achieved via capillary  action in the LHP wick (nickel).

## Crycooler to LHP Interface

- Cryocooler

- LHP Evaporators bolt to either side of the Cryocooler heat reject collar.
- Indium foil is used as a thermal interface.

- Evaporator

## LHP Bypass Valve

- A bypass valve is used to keep Cryocoolers from getting too cold in power outage situations.
- A bellows system filled with Argon is used to set the temperature set point of the valve.

## LHP Bypass Valve Schematic

- (Argon)

## TRD GAS BOX TCS

## TRD Gas Thermal Design 

- The TRD Gas system consists of two parts; the Supply (Box S) and the Circulation (Box C).
- Box S includes a high pressure Xenon tank, a high pressure CO2 tank, a mixing tank, pre-heater volumes, valves, pressure sensors, and associated tubing all mounted on an aluminum base plate.
- Box C includes two pumps, monitoring tubes and valves.
- Both Box S and Box C are enclosed in an MLI blanket.

## TRD Gas Thermal Design 

- Xe Tank

- CO2 Tank

- Circulation Box (Box C)

- Valve blocks

## TRD Gas Tank Heaters 

- Active heating is required to keep both the Xenon and CO2 tanks above their respective saturation temperatures.
- This is required in order to measure the amount of gas left in the tanks.
- Extremely long time constants preclude short term heating only.
- The Xenon tank should stay above 20oC
- The CO2 tank should stay above 34oC

## TRD Gas Tank Heaters 

- Kapton foil heaters are glued to the surface of the composite over-wrapped stainless steel tanks.
- On each tank there are two strings of eight heater patches (one per power feed).
- Four thermostats in series are used for each string to protect against over heating the tanks.
- Each tank is wrapped with MLI.

## TRD Gas Tank Heaters 

- heaters

- thermostats

## WAKE RADIATOR

## Tracker Radiators

- Tracker Radiator (2 x 1.225 m2)

## Safety thermostats assessment

- Analysis shows that the contemporary presence of all the heaters does not bring radiators skin temperature to the maximum design temperature for the Heat Pipes (114°C).
- Safety thermostats have been removed