AMS TIM July, 2008 – CERN 1 AMS 02 –Thermal Control System Design AMS-02 Thermal Control System (TCS)

AMS TIM July, 2008 – CERN 1

AMS 02 –Thermal Control

System Design

AMS-02 Thermal Control System (TCS)



System Design

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



System Design

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



System Design

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



System Design

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)



System Design

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.



System Design



System Design



System Design

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.



System Design



System Design

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.



System Design



System Design

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.



System Design

4 Zenith Radiator Panels



System Design

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.



System Design

Zenith Radiator Installation



System Design

Multi-Layer Insulation (MLI) Blankets



System Design

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.



System Design

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



System Design

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.



System Design

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



System Design

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.



System Design

Loop Heat Pipe System

ZENITH RADIATOR

CRYOCOOLER



System Design

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.



System Design

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.



System Design



System Design

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.



System Design

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.



System Design

Backup slides



System Design

TYPICAL RADIATOR INSERTS



System Design

TTCS Condenser Mounting Interface



System Design

Zenith Radiator Cross-Section

Radiator Mounting

Radiator Cross-section



System Design

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



System Design

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



System Design

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



System Design

Safety thermostats assessment: RAM radiator results

• Max Design temperature is 114 °C

• Max reached temperature is

82°C.



System Design

Safety thermostats assessment: WAKE radiator results

• Max Design temperature is 114 °C

• Max reached temperature is

103°C.



System Design

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.



System Design

Thermostats quantities (including spares):

Item Quantity

RAM radiator 49

WAKE radiator and PDS 63

PDS interlock 10

JPD 10

Tracker radiator 34

TOTAL 166



System Design

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).



System Design

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



System Design

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.



System Design

LHP Bypass Valve Schematic

(Argon)



System Design

TRD GAS BOX TCS



System Design

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.



System Design

TRD Gas Thermal Design

Xe Tank

CO2 Tank

Circulation Box (Box C)

Valve blocks



System Design

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



System Design

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.



System Design

TRD Gas Tank Heaters

heaters

thermostats



System Design

WAKE RADIATOR



System Design

Tracker RadiatorsTracker Radiator (2 x 1.225 m2)



System Design

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



System Design

Documents

AMS TIM July, 2008 – CERN 1 AMS 02 –Thermal Control System Design AMS-02 Thermal Control System (TCS)