Craig S. ClarkAMS-02 Phase II Safety Review1 AMS-02 Thermal Control System (TCS)

Craig S. Clark AMS-02 Phase II Safety Review 1

AMS-02 Thermal Control System (TCS)


AMS-02 Thermal Overview AMS-02 delivered to ISS in orbiter payload bay Mounted on S3, inboard, zenith Payload Attach Site Payload nominally dissipates 2400 watts (2800 watts

peak) Will meet all ISS and STS safety requirements Thermal requirements are defined in SSP 57003 (Attached

Payload Interface Requirements Document) 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

RadiatorsHeatersThermal BlanketsLoop Heat Pipes (LHPs)Standard Axial Groove Heat Pipes2-Phase CO2 pumped loop

Surface Optical Coatings


Radiators AMS-02 radiators include Main Radiators (Ram and

Wake), Tracker Radiators (Ram and Wake), and Zenith Cryocooler Radiators.

Zenith Radiator

Tracker Radiator

WAKE Radiator

Tracker Radiator

RAM Radiator

Main Radiator

WakeMain Radiator

Ram

RamWake


Main Radiators

Main Radiators dissipate heat from electronics crates.

Ram radiator dissipates up to 525 watts during normal operation, while the Wake Radiator dissipates up to 812 watts.


Main Radiators Mounting Main Radiators are mounted to 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 groove heat pipes (aluminum filled with

ammonia) are imbedded between face sheets. Heat pipe flanges maximize thermal contact at

crates mounting locations Chotherm 1671 is used as a thermal interface

filler between crates and radiators. Radiators are painted with SG121FD white paint

to optimize heat rejection.


AMS-02 Main Radiator Cross-section (flange removed)


AMS-02 Main Radiator Heat Pipe Layout

Ram Wake


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 latter.


Tracker Radiators

Tracker Radiator (2 x 1.225 m2)


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. TTCS Condensers bolt directly to heat pipe

flanges (40mm wide at interface locations, but only 22mm elsewhere).

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.


Tracker Radiator Cross-Section (non-interface section)


TTCS Condenser Mounting Interface


Tracker Radiator Heat Pipe Layout


CARBON FIBERSUPPORT STRUTS

TTCS CO2

CONDENSERS (old design)

EMBEDDED HEAT PIPERADIATOR PANEL


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 (LHPs) attached to a single cryocooler.

The LHPs 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.


Zenith Radiator Panels


Zenith Radiator Construction Radiators are a sandwich construction with Al

face sheets and a ROHACELL® core. 3mm aluminum tubes are brazed to upper face

sheet. 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 Cross-Section

Radiator Mounting

Radiator Cross-section


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)

All blankets will be positively secured. Typical construction will include multiple layers

of aluminized Mylar separated by Dacron scrim. Betacloth will protect exposed surfaces.


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


HeatersHeaters 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.

Thaw CO2 (TTCS system) and NH3 (heat pipes) in case of extended power outages in cold environments.

Manage TTCS operation


Heaters (continued)

Most heaters are both thermostatically and computer controlled.

Analyses have been performed to evaluate effect of “run away” heaters.

All safety critical heaters are two-fault tolerant.

No heaters are required to control any hazards.


Heat Pipes Standard axial groove heat pipes are used in several

location to help distribute heat: Main and Tracker radiators have embedded heat pipes mounted

directly to heat sources. Heat pipes are mounted to one of the USS-02 joints to help

dissipate heat from the CAB during magnet charging. Heat pipes are used on the CAB base plates to minimize

gradients. All heat pipes are aluminum filled with high purity

ammonia. Heat pipes are designed to survive freezing/thawing

cycles without excessive pressure or rupture.


Thermal Optical Coatings Passive thermal design of AMS-02 include the use of

thermal optical coatings. MLI blankets or plain Betacloth covers are used to

improve optics of some surfaces. Main and Tracker radiators are painted with SG121FD

white paint to improve heat rejection. The Zenith Radiator, along with parts of the Vacuum

Case, USS-02, High Voltage Bricks, and CAB are covered with silver-Teflon film to reduce peak temperatures.


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 (LHPs), provided by IberEspacio/Madrid, are similar to those successfully demonstrated as part of COM2PLEX flown on STS-107.

Propylene is used as a working fluid to avoid any freezing. Freezing point of propylene is -185C.


Loop Heat Pipe System for 1 Cryocooler

Radiator panel

Fluid Lines

Redundant Evaporators


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).


LHP Schematic


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 Heaters Heaters are mounted to the evaporators for LHP

startup and to keep Cryocoolers above their minimum storage limits.


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)


CAB Thermal SystemThe Cryomagnet Avionics Box (CAB) is

used to monitor and control the Cryomagnet.

Heat dissipation can vary from 35W to 800W.

Two Loop Heat Pipes (LHPs) will transport heat from the CAB base plate to the outer skin of the Wake Radiator.

Final design details are under review.


CAB Thermal System

LHP are similar to Cryocooler LHPs, 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.


CAB Thermal System

1 TOP HP

1 WAKE HP

2 LHP Condensers

2 WAKE LHPs

CAB


CAB Thermal System Additional axial groove heat pipes will be

attached on the USS between the Upper Trunnion Bridge Beam and the Upper Vacuum Case Interface Joint.


TRD Thermal Design

The TRD must be isothermal to +/-3ºCThe TRD and Upper Time Of Flight

(UTOF) are enclosed in a common thermal enclosure made of MLI blankets.

The Zenith Radiator is mounted on top of the TRD using low conductivity pins.

Primary TRD interfaces to USS-02 joints are insulated with titanium spacers.


TRD Thermal Design

Zenith Radiator

TRD

UTOF


TRD Thermal Design

The MLI blanket enclosure is made of 7-layer MLI, except for the portion under the Zenith radiator which is 10-layer.

Heaters are mounted on the TRD M-structure to help minimize gradients and to maintain the detector components (flipper valves) within operating limits.


TRD MLI

M-structure


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


TRD Gas Pre-Heaters A Pre-heater is used to warm small volumes of

Xenon and CO2 making transfer to the mixing tank more controlled.

Heater is computer controlled using temperature sensors on heater plate.

Heater will only be activated for brief periods (<15 minutes per day)

4 thermostats in series protects against over heating.


TRD Gas Valve Blocks The are 5 groups of valves in Box S mounted together with support

brackets. Brackets are isolated from the base plate with G10 spacers. Each block of valves is individually wrapped with MLI. Resistive heaters are mounted on each valve support bracket to

maintain valves above operating limits. A single thermostat is used to control each valve block heater

(Except for the tower valve which has 4 in series) Two additional thermostats in series are mounted on the base

plate to control power to all valve heaters.


TRD Gas Box C Box C pumps the low pressure gas mixture from

Box S to the TRD detector. The two pumps are enclosed in a pressurized

canister. Kapton foil heaters are mounted on this canister

to maintain the pumps above their operating limits.

Resistive heaters are mounted on a block of valves to maintain valve temperature limits.


TRD Gas Box C


TRD Gas Box C

Both the canister heater and the valve block heater are each controlled with a single thermostat.

The two additional thermostats on the base plate cut heater power in hot environments.


TRD Gas 28V Heater Schematic

A

c

c

c

c

c

c

c

c

Xe vessel <20WT T T T

Xe vessel <20WT T T T

CO2 vessel <24WT T T T

CO2 vessel <24WT T T T

Preheater <15W <10WT T T T

Valve Tower <10W tower<10W

T T T T

Preheater <15W <<<10W<10W

T T T T

Valve Tower <10W tower<10W

T T T T

B

A

Bc

c

c

c

c

c

c

c

UPDATE


TRD Gas 120V Heater Schematic

4 valve unit 11WT

2 valvefilter 7WT

2 Valve GP50 5W

C-tank 10WT

4C-valves 4WT

4 valve unit 11WT

2 valvefilter 7WT

2 Valve GP50 5WT

C-tank 10WT

4C-valves 4WT

A

B

A

B

T T

T T

UPDATE


Thermal Design of other AMS-02 Subsystems

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 optical coatings, etc.

None of these designs affect any pressure systems or other safety critical components.

Documents

Craig S. ClarkAMS-02 Phase II Safety Review1 AMS-02 Thermal Control System (TCS)