Small-GEO Satellite: Electrical Propulsion Sub-System ...

45th International Conference on Environmental Systems ICES-2015-283 12-16 July 2015, Bellevue, Washington

International Conference on Environmental Systems

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Small-GEO Satellite: Electrical Propulsion Sub-System (EPPS) Thermal Design and Lessons Learnt

Davide Rizzo1, Christian Vettore

2, Alessandro Spalla

3

CGS Compagnia Generale per lo Spazio, Milano, 20151, Italy

Marcus Gröller4, Dr. Frank Bodendieck

5, Dr. Dieter Birreck

6

OHB System SE, Bremen, Germany

Small-GEO is a general-purpose small geostationary satellite platform that is giving

European industry the opportunity to play a significant role in the commercial telecom

market. Small-GEO has been developed by an industrial team managed by OHB System SE.

The Thermal Control System (TCS) Critical Design Review (CDR) close-out was

successfully closed and the integration tasks have just been accomplished. The satellite is

now on his way to Thermal Vacuum (TVAC) test facility. Small-GEO foresees three

different types of propulsion systems, namely chemical, electrical and cold gas. This paper

describes the Satellite Platform Electrical Propulsion Sub-System (EPPS) thermal control

which uses mainly passive concepts complemented with heaters either thermostatically or

software regulated. The sizing cases used to design the thermal control system will be

presented as well as the final predictions both for transfer and geostationary phases. The

EPPS design is mainly connected to the GEO phases. The EPPS provides, with electric

propulsion thrusters, the impulse for orbit control, as well as for dissipation of excess

angular momentum that is accumulated in the reaction wheels. An overview of the sizing

firing scenarios will be presented; they involve not only the thrusters but the control units

and the related piping too. Then the most relevant results will be shown and discussed. The

last part of the paper deals with the problems encountered, the solutions adopted and the

lessons learnt during the design and optimization steps.

Nomenclature

ADE = Actuator Drive Electronics

ADPM = Antenna Deployment and Pointing Mechanism

AVG = Average

BOL = Beginning Of Life

CDR = Critical Design Review

CFRP = Carbon Fiber Reinforced Plastic

CGTA = Cold Gas Thruster Assembly

COP = Cold OPerating

EOL = End Of Life

EPPS = Electrical ProPulsion Sub-System

EP = Electrical Propulsion

EPTA = Electrical Propulsion Thruster Assembly

EQ = Equinox

1 Senior Thermal Engineer, Thermal & Mechanical Dept, [email protected].

2 Head of Thermal and Mechanical Department, Thermal & Mechanical Dept, [email protected].

3 Thermal Engineer, Thermal & Mechanical Dept, [email protected].

4 System Thermal Engineer, Thermal Design & Verification Dept, [email protected].

5 Head of Thermal Analysis and Verification Department, Thermal Dept, [email protected].

6 SGEO Project Manager, [email protected].


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ETSU = External Thruster Switching Unit

FDV = Fill and Drain Valve

FU = Filter Unit

GEO = Geostationary

GTO = Geostationary Transfer Orbit

HAG1 = Hispasat Advanced Generation 1

HET = Hall Effect Thruster

HIB = Hot Interface Box

LEOP = Launch and Early Orbit Phases

MLI = Multi Layer Insulator

OSR = Optical Solar Reflector

P/F = Platform

P/L = Payload

PPU = Power Processing Unit

PRP = Pressure Regulation Panel

PSA = Propellant Supply Assembly

RW = Reaction Wheel

S/C = Spacecraft

SCE = Support Control Electronics

SGEO = Small GEO

SM = Safe Mode

SMHP = Surface Mounted Heat Pipe

SS = Summer Solstice

TCS = Thermal Control System

TRP = Thermal Reference Point

TVAC = Thermal Vacuum

XFC = Xenon Flow Control unit

XTA = Xenon Tank Assembly

WS = Winter Solstice

I. Introduction

This section will present a general overview of the spacecraft (S/C) and, then, the attention will be focused on

the main features of the Electrical Propulsion Sub-System (EPPS), as a part of Small GEO Hispasat Advanced

Generation 1 (SGEO HAG 1) Platform. A few images with identification of the main elements will be provided.

The configurations of the S/C in its different phases are shown in the following pictures.

The solar arrays are either fully stowed for launch and de-tumbling cases or partially deployed (outermost panels

deployed in XY plane) for geostationary transfer orbit (GTO) cases.

a) Launch, on launcher adapter b) After release c) General GTO

Figure I-1 Small SGEO in LEOP and GTO configurations


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The next pictures show the location of the Hall Effect Thrusters (HET) thrusters and an overview of the Xenon tanks

and the EPPS piping inside the S/C.

Figure I-3 HET-HET thrusters support panel and location

Figure I-4 SGEO HAG1 EPPS internal model overview

Figure I-2 Small SGEO in GEO configuration


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II. Small-GEO EPPS functional description

The Electrical Propulsion System is a part of the Small Geostationary Platform.

The function of the EPPS is to perform orbital manoeuvers during:

- initial detumble after separation from Launch Vehicle (Cold Gas Thruster Assembly);

- station acquisition and repositioning;

- station-keeping N/S and E/W during 15 years;

- momentum management during all phases except during GTO-GEO transfer;

- transfer to graveyard orbit at End of Mission.

Electrical propulsion system components are:

- Xenon Tanks Assembly (XTA).

- Propellant Supply Assembly (PSA): Support Control Electronics (SCE) and Pressure Regulator Panel (PRP)

- 2 EP Thruster Assembly (EPTA) each composed of: Power Processing Unit (PPU), 4 Hall Effect Thrusters

(HET), 4+4 Xe Flow Control unit (XFC), 4 Filter Units (FU) and an External Switching Unit (ETSU).

- EPPS Inter-assembly Tubing including valves and tubing support.

The following schematic summarizes all the SGEO EPPS components.

Figure II-1 Small SGEO EPPS overview


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The power demand for the SGEO HAG1 EPPS is 1.6kW.

A. XTA

The XTA consists of two tanks that have an internal volume of 60L. The tanks are made from a Ti-6Al4V

liner with two welded-on tubes (Ti-3Al-2.5V). This liner is overwrapped with Carbon Fiber Reinforced Plastic

(CFRP). The mechanical interface on the lower (-Z) end is an adapter flange to the SGEO structure. At the upper

(+) end there is a ball bearing to allow limited movement of the tank. For the SGEO program, one of the tank

ports has been rotated by 180 deg in order to simplify accommodation into SGEO.

B. PSA

The function of the PSA is to decrease the pressure from the XTA (186 bar @ BOL @ 50 ºC) to the required

operational pressure (2.2 bar @ 20ºC) and to supply a constant feed pressure to the different thruster assemblies.

The PSA consists of a PRP, which is the mechanical part of the system and the SCE which is the electronics that

controls the PRP. The PRP has two ports to the exterior of the satellite. These allow filling of the XTA, at high

pressure, and provides a test port for the low pressure side of the PRP. There are also four ports to the remaining

EPPS, three low pressure branches and one high pressure branch. The low pressure branches lead to the two

discrete ion propulsion branches and one to the tube leading to the Cold Gas Conditioning System (CGCS). The

high pressure branch leads to the lower port of the two XTAs.

C. EPTA

The Electronic Propulsion Thruster Assembly consists of one PPU, one ETSU and four HETs, each with

their dedicated Hot Interface Box (HIB), FU and XFC. The PPU connects to the system bus to be able to provide

power to the ETSU, which in turn powers the HETs, via the FUs. The HETs are, via the XFCs, attached to one

of the low pressure branches of the PSA.

Electrical Propulsion Subsystem

(EPPS)

Xenon Tank Assembly

(XTA)

Propellant Supply Assembly

(PSA)

Support Control Electronics (SCE)

Pressure Regulator Panel (PRP)

Harness

Xenon Tanks

EP Thruster Assembly

(HET)

Power Processing Unit (PPU)

Xenon Flow Control Unit (XFC)

Thruster (HET)

External Thruster Switching Unit

(ETSU)

Filter Unit (FU)

Harness

EPPS inter-assembly tubing

Tubing

Isolation valves

Tubing support

Figure II-2 Small SGEO EPPS breakdown


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Each of the four HET thrusters with the corresponding XFC, HIB and interconnecting tubing and harness, are

assembled onto structural brackets into eight HET thruster sub-assemblies, given by the figure below. The

complete assembly is integrated from the outside onto the thruster panel.

The HET assemblies (i.e. HET + HET bracket) are mounted on large common brackets, HET assembly brackets.

Each HET assembly bracket is attached on one side to a S/C radiator (65 deg zones) and on the other side to a

CFRP panel as shown in the next picture.

Figure II-4 Small SGEO two HET assemblies on a S/C corner

Figure II-3 Small SGEO single HET sub-assembly

Figure II-5 Small SGEO HET thruster


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D. EPPS inter-assembly tubing

The inter-assembly tubing consists of a high-pressure branch and a low-pressure branch.

The high-pressure tubing connects the lower Xenon tank ports to the PSA pressure regulation panel and one

FDV. High pressure tubing is also used to connect the upper Xenon tank ports to the Fill and Drain Valve (FDV)

used drain the system. The low pressure tubing is all Xenon tubing downstream of the PSA. This tubing is made

up of four branches, two connecting the PSA to the HETs, one connecting the PSA to the CGCS and one

connecting the CGCS to the CG Thruster Valves (CGTV). The tubing material is Ti-3Al2.5V The tubing is held

together by aluminum stand-offs, which are attached to the satellite structure. There are two main types of stand-

offs, one that can support up to five tubes and one that can support up to two tubes. These are further subdivided

to provide support in different configurations, vertical or horizontal and with varying base.

The EPPS has three Fill and Drain Valves connecting the tubing system to the outside of the satellite. They are

positioned on the –Z Antenna Deployment and Pointing Mechanism (ADPM) structure panel. The first FDV is

used as a test port to externally test the pressure of the xenon propellant at the low pressure node of the PSA. The

second FDV connects to the high pressure node of the PSA. It is used to fill the XTA as well as to test the EPPS,

including the PSA but without the XTA. This can be done by closing isolation valves placed at the input to each

Xenon tank. The third FDV is used as a high pressure drain port, to be used when evacuating the XTA, without

affecting the remaining EPPS.

III. Small-GEO EPPS applicable thermal requirements

The qualification or design temperature ranges, at Thermal Reference Point (TRP) level, applicable to the SGEO

EPPS equipment are reported here below:

EPPS Platform Equipment Design temperatures

Non Operating Start-Up Operating

Description Abbreviation TNOP,min TNOP,max TST,min TST,max TOP,min TOP,max

[°C] [°C] [°C] [°C] [°C] [°C]

Propellant Supply Assembly PSA

PSA - Support Control Electronics SCE -10 50 -10 50 -10 50

PSA - Fill & Drain Valve FDV -35 50 -35 50 -35 50

CG Thruster Assembly CGTA

CG Actuator Drive Electronics ADE -10 50 -10 50 -10 50

CG Thruster Valve TV 15 50 15 50 20 50

HET Assembly

HET Thruster HET -20 190 -20 190 -20 190

HET Xenon Flow Control XFC -5 85 -5 85 -5 85

HET electrical Filter Unit FU -30 60 -30 60 -15 60

HET Hot Interface Box HIB -15 110 -15 110 -15 110

HET External Thruster Switching Unit

ETSU -15 50 -15 50 -10 50

HET Power Processing Unit PPU -15 50 -15 50 -10 50

Table III-1 SGEO EPPS equipment temperatures


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EPPS Platform Equipment Design temperatures

Non Operating Start-Up Operating

Description Abbreviation TNOP,min TNOP,max TST,min TST,max TOP,min TOP,max

[°C] [°C] [°C] [°C] [°C] [°C]

Xenon Tank Assembly XTA 20 50

35 47

Propellant Supply Assembly PSA

PSA – PRP PRP 30 40 30 40 20 50

CG Thruster Assembly CGTA

CG Conditioning System CGCS 30 40 30 40 20 50

Xenon Tubing

Tubing Low Pressure (LP) XTA -35 80 NA NA -35 80

Tubing High Pressure (HP) XTA 20 50 NA NA 20 50

Table III-2 SGEO EPPS equipment temperatures (cont.)

The power dissipation of each EPPS component is here below presented:

Power [W]

EQB

OL

CO

P1

2

EQB

OL

CO

P1

EQB

OL

CO

P2

EQB

OL

CO

P3

EQB

OL

CO

P4

EQB

OL

TC7

EQEO

L TC

8

EQEO

L TC

9

SMEQ

BO

L G

12

SSB

OL

B1

SSB

OL

TC7

SSEO

L E1

SSEO

L TC

8

SSEO

L TC

9

WSB

OL

C1

WSB

OL

TC6

WSB

OL

TC7

WSE

OL

F1

WSE

OL

TC8

WSE

OL

TC9

HET MAX 0 0 0 0 0 284.3 284.3 284.3 0 284.3 284.3 284.3 284.3 284.3 284.3 284.3 284.3 284.3 284.3 284.3

HET MIN 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

HET AVG 0 0 0 0 0 45.958 45.958 45.958 0 45.958 45.958 45.958 45.958 45.958 45.958 45.958 45.958 45.958 45.958 45.958

XFC MAX 0 0 0 0 0 1.9 1.9 1.9 0 1.9 1.9 1.9 1.9 1.9 1.9 1.9 1.9 1.9 1.9 1.9

XFC MIN 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

XFC AVG 0 0 0 0 0 0.307 0.307 0.307 0 0.307 0.307 0.307 0.307 0.307 0.307 0.307 0.307 0.307 0.307 0.307

FU MAX 0 0 0 0 0 1.9 1.9 1.9 0 1.9 1.9 1.9 1.9 1.9 1.9 1.9 1.9 1.9 1.9 1.9

FU MIN 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

FU AVG 0 0 0 0 0 0.307 0.307 0.307 0 0.307 0.307 0.307 0.307 0.307 0.307 0.307 0.307 0.307 0.307 0.307

HARNESS MAX 0 0 0 0 0 2.32 2.32 2.32 0 2.32 2.32 2.32 2.32 2.32 2.32 2.32 2.32 2.32 2.32 2.32

HARNESS MIN 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

HARNESS AVG 0 0 0 0 0 0.375 0.375 0.375 0 0.375 0.375 0.375 0.375 0.375 0.375 0.375 0.375 0.375 0.375 0.375

PRP MAX 0 0 0 0 0 6.9 6.9 6.9 8.1 6.9 6.9 6.9 6.9 6.9 6.9 6.9 6.9 6.9 6.9 6.9

PRP MIN 0 0 0 0 0 0 0 0 8.1 0 0 0 0 0 0 0 0 0 0 0

PRP AVG 0 0 0 0 0 1.115 1.115 1.115 8.1 1.115 1.115 1.115 1.115 1.115 1.115 1.115 1.115 1.115 1.115 1.115

CGCS MAX 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

CGCS MIN 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

CGCS AVG 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

CGTV MAX 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

CGTV MIN 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

CGTV AVG 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Table III-3 EPPS power dissipation summary

IV. Small-GEO EPPS Thermal Control Subsystem description

The main function of the SGEO Thermal Control System (TCS) is to maintain all the S/C equipment within the

allowed temperature ranges. For this purpose, SGEO uses thermal control techniques common to all S/Cs:

- large lightweight radiators

- Multi-Layer Insulator (MLI) blankets on all external surfaces not used for radiators.

- embedded and surface mounted heat pipes

- high emittance internal coatings

- internal MLI/ Single-Layer Insulator (SLI) blankets

- heaters/thermostats

- coating/painting

EPPS thermal control main features are:

- Xenon tanks are fully covered with MLI and equipped with heaters;

- Xenon piping is isolated from structure by low conductivity stand-offs;

- specific piping sections are heater controlled and covered by low-emissivity tape;

- HET assemblies are mounted on Al brackets, attached to a S/C radiator and to a CFRP panel;

- PPU is mounted on heat pipes, along with ADE and SCE, to reject its high dissipation;

- ETSU is heaters controlled and installed on an Al doubler;


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- PRP and CGCS are bolted on CFRP panel, isolated by Ti washers and heaters controlled.

Each of the above mentioned bullets are now fully explained. Here below some pictures of the integrated S/C are

presented.

A. XTA and piping

The two Xenon tanks are fully covered with MLI and equipped with heaters for maintaining the temperature

level during the cold phases. The parts of the Xenon piping that are thermally controlled are covered as a baseline

with low emissivity tape. No MLI is used. Low conductivity stand-offs keep the piping at few centimeters from the

walls.

Figure IV-1 Small SGEO Satellite EPPS components

Figure IV-2 Small SGEO Satellite EPPS piping


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B. Thrusters

The HET assemblies are mounted as shown in Figure II-4. The HET thruster is mounted on an aluminum bracket

(i.e. HET bracket) that also carries the XFC and HIB units, as shown in Figure II-3. All these components are

mounted without thermal filler. Heaters on the HET bracket maintain the thruster above the minimum non-operating

temperature in cold cases.

The HET assembly is mounted – again without thermal filler – on the HET Bracket at 6 fixation points.

Figure IV-3 HET bracket mounting

C. PPU/ETSU

The PPU, sitting on the South Platform (P/F) Radiator, that powers the HET thrusters has a dissipation of up to

136W during thruster operation. This very large dissipation is spread over the platform radiator by means of the heat

pipe network.

The ETSU, with its small dissipation, does not need heat pipes and is cooled by conduction to the radiator and

radiation to the environment.

The ETSUs are sitting on an aluminum doubler that serves mainly to spread the heat transferred by Reaction Wheels

Heat pipes.

D. SCE

This low dissipation electronic unit is functionally associated to the PSA-PRP. It is located on the same heat

pipes as the PPUs.

E. PSA PRP

The PSA PRP are mounted to internal CFRP panels with 19 bolts for PSA-PRP. Titanium washers are used at all

bolts and there is no contact between the two units and the supporting panels. The dissipation is evacuated mainly by

radiation to the environment. No special thermal control means are needed except cold case heaters.

V. Thermal sizing cases and EPPS operation scenarios

In order to derive the thermal sizing cases the complete mission profile has been analyzed and specific

dissipation cases have been selected depending on the scenario (e.g. GTO vs GEO).

Phase Description

Pre-launch Ground operation.

LEOP From liftoff (depending on mission, the S/C may be launched in an active/passive state) up to S/C separation. Depending on mission, the S/C may be launched in an active/passive state.

GTO This phase is entered when the spacecraft is transferred from the GTO to the GEO orbit.

Orbit Relocation This phase is activated when the satellite is to be manoeuvered in its orbital position for operational reasons. Payloads are deactivated in this phase.

On-Station The On-Station phase represents the nominal phase when the satellite has reached its geo-stationary position. Payloads can only be activated in this phase.

Graveyard This phase is entered when the satellite is retired.

Table V-1 Complete mission profile summary

The EPPS works mainly after the LEOP and GTO phases.

The driving factors and the criticalities for the EPPS firing sizing cases are:


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HET thruster firing duration;

orbital position and season;

reaction wheels power dissipation profiles;

PPU (South side, one is very close to the reaction wheels) temperature limits;

FU temperature limits;

The most critical cases for the SGEO EPPS are in hot environment, that is to say that the HET thrusters firing

occurs when the Sun is illuminating the North (Summer Solstice) or the South (Winter Solstice) side of the

satellite.

Figure V-1 On station Sun illumination

The other driving factors are the Payload (P/L) and P/F dissipation profiles. A quick synoptic summary of the EPPS

power dissipation is provided in section III.

A. EPPS EP configuration

Figure V-2 shows the Electrical Propulsion (EP) thrusters accommodation on the satellite. The EP system

consists of two branches, which are operated in cold redundancy in the baseline:

Branch A (EP1, EP4, EP5, EP8) made of HET/ SPT-100 operated at 75 mN

Branch B (EP2, EP3, EP6, EP7) made of HET/ SPT-100 operated at 75 mN

Only branch A is supposed to fire in the simulations.

Figure V-2 EP Thrusters accommodation on the Satellite

In the baseline operational concept, only one EP thruster is operated at a time at its nominal operating point

(nominal power, thrust and specific impulse). If a manoeuver requires the use of two thrusters, it is split into two


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sequential manoeuvers using only one thruster each at a time. To switch from one thruster to another, a minimum

gap of 60 s shall be assumed between two sequential manoeuvers.

B. Nominal operation – Station Keeping

During station-keeping, 4 HET thrusters are typically fired in total 5 or 6 times per day (i.e. each thruster is fired

once or twice). The specified firing scenarios have been somewhat modified in order to make the implementation in

the thermal model easier. The main differences are:

• no gap between thruster switching is considered, however the specified maximum burn time for each thruster is

considered as well as the preheating of the thrusters;

• the PPU as the driving factor is powered until the temperature limit is achieved, this is estimated to be 116

minutes of continuing firing;

• the FU and XFC as the driving factors are powered until the temperature limit is achieved, this is estimated to be

63 minutes of continues firing, the total amount of 116 minutes for two adjacent firings has been assumed;

• in order to catch the worst case for the thruster, the firing manoeuver starts at the hottest point in orbit, which

might deviate from the actual node for a given sequence. Here after are the firing sequences described applicable to

the different seasonal cases.

Summer solstice

1st thruster Start time 2nd thruster

First sequence EP4 17430s EP5

Second sequence EP1 70930s EP8

Winter solstice




Winter solstice: PPU combined with the hottest RW




Equinox




Table V-2 HET firing sequences

The firing scenarios and associated dissipation are hereafter presented for equinox (winter and solstice profiles are

identical with different firing starting points):


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0 6 12 18 24 30 36 42 480

50

100

150

200

250

300

Time [hrs]

Po

we

r [W

]

EP1

EP2

EP3

EP4

EP5

EP6

EP7

EP8

0 6 12 18 24 30 36 42 480

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Time [hrs]

Po

we

r [W

]

FU1

FU2

FU3

FU4

FU5

FU6

FU7

FU8

0 6 12 18 24 30 36 42 480

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Time [hrs]

Po

we

r [W

]

XFC1

XFC2

XFC3

XFC4

XFC5

XFC6

XFC7

XFC8

Figure V-3 Equinox – HET, FU and XFC dissipations during firing

0 6 12 18 24 30 36 42 480

20

40

60

80

100

120

140

Time [hrs]

Po

we

r [W

]

PPU 1

PPU 2

0 6 12 18 24 30 36 42 480

1

2

3

4

5

6

7

8

Time [hrs]

Po

we

r [W

]

TSU 1

TSU 2

ADE

SCE

Figure V-4 Equinox PPU, TSU, ADE and SCE dissipations during firing

C. GEO Station acquisition and repositioning

During this case, the S/C rotates slowly around its Z axis (4 rotations per day), which remains pointed to the

Earth. The HETs are firing 16 times per day, in a sequence such that the firing direction is always in the same

quadrant of the S/C, Figure V-6.

Figure V-5: Attitude during Repositioning Thruster Firing Scenario


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Orbit path

Flight direction

72 min firing

9 min gap

9 min gap

Spin rate around Z 1°/min

Figure V-6: Thruster Firing Scenario

Also the cases with 60 minutes firing instead of 72 has been considered. The gaps are 15 minutes each.

The firing scenarios and associated dissipation for the specific on station acquisition/repositioning case (i.e. the HET

are firing 16 times per day) is hereafter presented.

0 6 12 18 24 30 36 42 480

50

100

150

200

250

300

Time [hrs]

Po

we

r [W

]

EP1

EP2

EP3

EP4

EP5

EP6

EP7

EP8

0 6 12 18 24 30 36 42 480

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Time [hrs]

Po

we

r [W

]

FU1

FU2

FU3

FU4

FU5

FU6

FU7

FU8

0 6 12 18 24 30 36 42 480

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Time [hrs]

Po

we

r [W

]

XFC1

XFC2

XFC3

XFC4

XFC5

XFC6

XFC7

XFC8

Figure V-7 Winter Solstice Repositioning – HET, FU and XFC dissipations during firing

0 6 12 18 24 30 36 42 480

20

40

60

80

100

120

140

Time [hrs]

Po

we

r [W

]

PPU 1

PPU 2

0 6 12 18 24 30 36 42 480

1

2

3

4

5

6

7

8

Time [hrs]

Po

we

r [W

]

TSU 1

TSU 2

ADE

SCE

Figure V-8 Winter Solstice Repositioning – PPU, TSU, ADE and SCE dissipations during firing


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VI. Thermal analysis results

The main objective of the thermal analyses presented here is to demonstrate that the SGEO EPPS TCS complies

with the thermal performance requirements. These can be summarized as follows:

the TCS must maintain at all times all the parts and equipment within the applicable temperature limits, with

the applicable margins;

this must be achieved within the available resources (mass and power budget, number of heater lines, …).

The presented temperatures figures are predicted ones, that means calculated values plus (for the maximum

temperatures) and minus (for the minimum temperatures) the estimated uncertainties.

The Cold Operating (COP) and the Safe Mode (SM) are not sizing cases, that is why firing scenarios have not been

taken into account for these ones in the simulations. All the EPPS units remain within their limits in cold cases

thanks to the heating power coming from EPPS heater lines. Table VI-1 summarizes the duty cycles all over the

analysed cases:

HEATER LINES/DUTY

CYCLE [%]

EQB

OL

CO

P1

2

EQB

OL

CO

P1

EQB

OL

CO

P2

EQB

OL

CO

P3

EQB

OL

CO

P4

EQB

OL

TC7

EQEO

L TC

8

EQEO

L TC

9

SMEQ

BO

L G

12

SSB

OL

B1

SSB

OL

TC7

SSEO

L E1

SSEO

L TC

8

SSEO

L TC

9

WSB

OL

C1

WSB

OL

TC6

WSB

OL

TC7

WSE

OL

F1

WSE

OL

TC8

WSE

OL

TC9

TSU 1 60 60 58 50 50 25 23 25 29 23 23 16 10 14 0 0 0 0 0 0

TSU 2 40 40 43 35 35 17 18 18 34 15 16 10 9 9 0 0 0 0 0 0

HP PF S1 9 9 9 7 7 2 2 2 1 0 0 0 0 0 0 7 7 0 0 0

HP PF S2 100 100 100 100 100 79 74 75 100 81 81 76 74 76 0 0 0 0 0 0

HP PF N 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

XTA-1 38 38 38 33 33 28 31 32 36 25 25 24 25 25 13 21 21 6 17 17

XTA-2 31 33 32 31 31 24 25 27 34 15 16 8 10 13 16 21 21 17 18 20

PRP 31 31 31 30 30 19 18 20 0 12 14 4 4 5 11 17 17 4 9 11

HET EP-1 41 41 41 29 29 11 15 19 51 0 0 0 0 0 6 15 15 5 10 14

HET EP-2 35 35 35 29 29 15 19 22 75 0 0 0 0 0 14 21 22 15 18 21

HET EP-3 25 25 25 24 24 3 4 11 49 0 0 0 0 0 0 5 6 3 1 8

HET EP-4 27 27 27 26 26 7 9 16 74 0 0 0 0 0 7 12 13 13 9 15

HET EP-5 31 32 31 30 30 12 18 23 56 25 20 27 17 23 0 0 0 0 0 0

HET EP-6 29 29 29 28 28 14 19 23 81 28 23 30 22 27 0 0 0 0 0 0

HET EP-7 50 51 50 28 28 14 25 22 56 19 20 26 24 19 0 0 0 0 0 0

HET EP-8 42 42 42 29 29 15 26 22 79 23 24 30 28 24 0 0 0 0 0 0

FU-1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

FU-2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

FU-3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

FU-4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

FU-5 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

FU-6 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

FU-7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

FU-8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

XE SOUTH 99 99 98 92 92 75 83 82 100 70 71 70 68 67 7 42 44 0 11 10

XE EAST 86 86 86 82 82 52 55 63 90 16 23 3 5 11 36 49 51 32 38 46

XE TO FDV 7 7 7 6 6 3 2 3 0 0 0 0 0 0 0 1 1 0 0 0

XE EP-1 5 5 5 5 5 4 4 4 5 1 1 0 0 1 3 4 4 3 3 4

XE EP-2 5 5 5 5 5 4 4 4 5 0 1 0 0 1 3 3 3 3 3 3

XE EP-3 4 4 4 4 4 3 3 3 5 0 1 0 0 0 2 3 3 3 3 3

XE EP-4 3 3 3 3 3 2 2 2 4 0 0 0 0 0 1 2 2 1 1 2

XE EP-5 5 5 5 4 4 3 4 4 5 4 3 4 3 3 0 1 1 0 0 1

XE EP-6 4 4 4 4 4 3 4 4 5 3 3 4 3 3 0 1 1 0 0 1

XE EP-7 5 5 5 5 5 4 4 4 5 4 4 4 4 4 0 1 1 0 1 0

XE EP-8 12 12 12 11 11 9 10 9 13 8 8 9 9 8 0 2 3 0 1 1 Table VI-1 EPPS heater lines duty cycles

An orange cell means that the duty cycle is between 90% and saturation, while a red one means that a specific line is

in saturation. The following bar charts prove that in the cold cases all the instrumentation is compliant (no out of

specifications encountered):


16

-50°C

-50°C

-10°C

-10°C

30°C

30°C

70°C

70°C

110°C

110°C

150°C

150°C

190°C

190°C

230°C

230°C

EPTA NW CORNER

HET EP 1 54.48-20°C2 152.95 +190°C

XFC EP 1 nom 24.5-5°C 3 61.67 +85°C

XFC EP 1 red 22.39-5°C 4 62.81 +85°C

FU EP 1 19.58-30°C 25.33 45.09 +60°C

HIB EP 1 23.34-15°C 14.74 86.92 +110°C

HET EP 2 42.26-20°C 8.6 159.12 +190°C

XFC EP 2 nom 21.51-5°C 5. 62.83 +85°C

XFC EP 2 red 21.4-5°C 5. 62.97 +85°C

FU EP 2 21.36-30°C 29.5 39.14 +60°C

HIB EP 2 22.24-15°C 15.62 87.14 +110°C

EPTA NE CORNER

HET EP 3 40.65-20°C 9.2 160.09 +190°C

XFC EP 3 nom 20.43-5°C 7. 62.26 +85°C

XFC EP 3 red 20.35-5°C 7. 62.34 +85°C

FU EP 3 14.54-30°C 31.41 44.05 +60°C

HIB EP 3 21.07-15°C 17.04 86.89 +110°C

HET EP 4 55.44-20°C1 153 +190°C

XFC EP 4 nom 22.33-5°C 6. 61.42 +85°C

XFC EP 4 red 22.24-5°C 6. 61.58 +85°C

FU EP 4 22.08-30°C 30.35 37.57 +60°C

HIB EP 4 23.1-15°C 16.03 85.87 +110°C

EPTA SE CORNER

HET EP 5 50.9-20°C 3 155.3 +190°C

XFC EP 5 nom 23.64-5°C3 62.92 +85°C

XFC EP 5 red 21.55-5°C 4 64.07 +85°C

FU EP 5 15.17-30°C 29.15 45.68 +60°C

HIB EP 5 22.45-15°C 14.56 87.99 +110°C

HET EP 6 40.39-20°C 8.8 160.8 +190°C

XFC EP 6 nom 20.53-5°C 5. 63.99 +85°C

XFC EP 6 red 20.38-5°C 5. 64.15 +85°C

FU EP 6 22.47-30°C 28.54 38.99 +60°C

HIB EP 6 21.31-15°C 15.51 88.18 +110°C

EPTA SW CORNER

HET EP 7 40.07-20°C 9.7 160.17 +190°C

XFC EP 7 nom 20.8-5°C 5. 64.19 +85°C

XFC EP 7 red 20.74-5°C 4 64.37 +85°C

FU EP 7 22.63-30°C 22.71 44.66 +60°C

HIB EP 7 21.14-15°C 15.18 88.68 +110°C

HET EP 8 57.69-20°C0 151.4 +190°C

XFC EP 8 nom 25.94-5°C2 61.25 +85°C

XFC EP 8 red 23.95-5°C 3 62.39 +85°C

FU EP 8 21.88-30°C 28.55 39.57 +60°C

HIB EP 8 24.24-15°C 13.89 86.87 +110°C

Figure VI-1 Equinox COP cases and Safe Mode min-max summary for EPTA corners


17

-60°C

-60°C

-20°C

-20°C

20°C

20°C

60°C

60°C

100°C

100°C

Prop. Supply Assy

PRP 16.7+20°C1 +50°C

SCE 14.71-10°C2 42.86 +50°C

EPTA Electronic Units

ETSU Branch A 16.02-15°C 4. 43.99 +50°C

PPU Branch A 16.6-15°C 5. 42.63 +50°C

ETSU Branch B 16.02-15°C 4. 43.99 +50°C

PPU Branch B 14.59-15°C 6. 43.59 +50°C

Fill and Drain Valves

FDV-XTA 33.42-35°C 32.81 18.77 +50°C

FDV-PRP 33.42-35°C 32.81 18.77 +50°C

FDV-test 33.42-35°C 32.81 18.77 +50°C

Figure VI-2 Equinox COP cases and Safe Mode min-max summary for other EPPS units

-20°C

-20°C

20°C

20°C

60°C

60°C

100°C

100°C

Xenon Tanks Assy

XTA-1 10.+35°C +47°C

XTA-2 10.+35°C +47°C

Figure VI-3 Equinox COP cases and Safe Mode min-max summary for XTA

The worst hot case for the EPPS is (Winter Solstice End Of Life, dissipation case F1) WSEOL F1, and, in specific,

for the South-East corner (EPTA nr. 5). The min-max and transient results will be shown only for this case because

it is the most interesting one with respect to EPPS. Some transient graphs will be shown also for WSEOL G12 with

repositioning manoeuver. The temperatures are, in this case, lower due to the satellite spin.

-60°C

-60°C

-20°C

-20°C

20°C

20°C

60°C

60°C

100°C

100°C

Prop. Supply Assy

PRP 20.62+20°C1 +50°C

SCE 27.25-10°C 19.16 +50°C

EPTA Electronic Units

ETSU Branch A 17.71-10°C 25.44 16.85 +50°C

PPU Branch A 37.22-10°C 17.34 +50°C

ETSU Branch B 18.84-15°C 26.68 19.48 +50°C

PPU Branch B 27.34-15°C 23.28 +50°C

Fill and Drain Valves

FDV-XTA 30.53-35°C 44.88 +50°C

FDV-PRP 30.53-35°C 44.88 +50°C

FDV-test 30.53-35°C 44.88 +50°C

Figure VI-4 WSEOL F1 case min-max summary for other EPPS units


18

-20°C

-20°C

20°C

20°C

60°C

60°C

100°C

100°C

Xenon Tanks Assy

XTA-1 10.+35°C +47°C

XTA-2 10.+35°C +47°C

Figure VI-5 WSEOL F1 case min-max summary for XTA

-50°C

-50°C

-10°C

-10°C

30°C

30°C

70°C

70°C

110°C

110°C

150°C

150°C

190°C

190°C

230°C

230°C

EPTA NW CORNER

HET EP 1 128.92-20°C0 80.56 +190°C

XFC EP 1 nom 50.68-5°C 6. 32.4 +85°C

XFC EP 1 red 42.67-5°C 8.1 39.2 +85°C

FU EP 1 23.38-15°C 26.27 25.35 +60°C

HIB EP 1 44.4-15°C 17.13 53.47 +100°C

HET EP 2 46.28-20°C 8.2 155.47 +190°C

XFC EP 2 nom 30.67-5°C 9.5 49.83 +85°C

XFC EP 2 red 30.39-5°C 9.6 49.93 +85°C

FU EP 2 17.17-30°C 46.96 25.87 +60°C

HIB EP 2 32.64-15°C 18.7 73.66 +110°C

EPTA NE CORNER

HET EP 3 43.66-20°C 7. 159.1 +190°C

XFC EP 3 nom 29.11-5°C 9.2 51.6 +85°C

XFC EP 3 red 28.93-5°C 9.4 51.63 +85°C

FU EP 3 18.46-30°C 42.63 28.91 +60°C

HIB EP 3 30.18-15°C 19.1 75.72 +110°C

HET EP 4 128.73-20°C1 80.06 +190°C

XFC EP 4 nom 48.53-5°C 9.4 31.98 +85°C

XFC EP 4 red 42.75-5°C 9.5 37.68 +85°C

FU EP 4 23.64-15°C 32.24 19.12 +60°C

HIB EP 4 43.59-15°C 18.96 52.45 +100°C

EPTA SE CORNER

HET EP 5 118.29-20°C 31.09 60.62 +190°C

XFC EP 5 nom 49.93-5°C 32.44 +85°C

XFC EP 5 red 41.33-5°C 33.77 14.9 +85°C

FU EP 5 24.48-15°C 49.66 +60°C

HIB EP 5 42.87-15°C 41.93 30.2 +100°C

HET EP 6 40.36-20°C 36.36 133.28 +190°C

XFC EP 6 nom 30.23-5°C 32.83 26.94 +85°C

XFC EP 6 red 29.95-5°C 33.07 26.98 +85°C

FU EP 6 18.63-30°C 62.11 +60°C

HIB EP 6 32.05-15°C 41.77 51.18 +110°C

EPTA SW CORNER

HET EP 7 41.2-20°C 34.27 134.53 +190°C

XFC EP 7 nom 28.75-5°C 30.58 30.67 +85°C

XFC EP 7 red 28.47-5°C 30.76 30.77 +85°C

FU EP 7 18.37-30°C 61.67 +60°C

HIB EP 7 30.14-15°C 40.03 54.83 +110°C

HET EP 8 123.48-20°C 27.62 58.9 +190°C

XFC EP 8 nom 49.38-5°C 28.81 +85°C

XFC EP 8 red 41.03-5°C 29.98 18.99 +85°C

FU EP 8 19.94-15°C 45.96 9.1 +60°C

HIB EP 8 41.63-15°C 39.38 33.99 +100°C

Figure VI-6 WSEOL F1 case min-max summary for EPTA corners


19

For this specific case, now the transients (calculated temperatures) of the EPPS are shown:

0 6 12 18 24 30 36 42 48-20

0

20

40

60

80

100

Time [hrs]

Te

mp

era

ture

[°C

]

EP3

EP4

FU3

FU4

XFC3a

XFC3b

XFC4a

XFC4b

0 6 12 18 24 30 36 42 48-20

0

20

40

60

80

100

Time [hrs]

Te

mp

era

ture

[°C

]

EP1

EP2

FU1

FU2

XFC1a

XFC1b

XFC2a

XFC2b

0 6 12 18 24 30 36 42 4820

30

40

50

60

70

80

90

100

110

120

Time [hrs]

Te

mp

era

ture

[°C

]

EP5

EP6

FU5

FU6

XFC5a

XFC5b

XFC6a

XFC6b

0 6 12 18 24 30 36 42 480

20

40

60

80

100

120

Time [hrs]

Te

mp

era

ture

[°C

]

EP7

EP8

FU7

FU8

XFC7a

XFC7b

XFC8a

XFC8b

Figure VI-7 Case WSEOL F1 EPTA transient temperatures

0 6 12 18 24 30 36 42 4810

15

20

25

30

35

40

Time [hrs]

Te

mp

era

ture

[°C

]

PPU 1

PPU 2

0 6 12 18 24 30 36 42 4826

27

28

29

30

31

32

33

34

35

36

Time [hrs]

Te

mp

era

ture

[°C

]

PRP

CGCS

0 6 12 18 24 30 36 42 4812

14

16

18

20

22

24

26

28

30

32

Time [hrs]

Te

mp

era

ture

[°C

]

TSU

ADE

SCE

0 6 12 18 24 30 36 42 4839

39.5

40

40.5

41

41.5

Time [hrs]

Te

mp

era

ture

[°C

]

Xenon Tank 1

Xenon Tank 2

Figure VI-8 Case WSEOL F1 other EPPS components transient temperatures


20

0 6 12 18 24 30 36 42 48-20

0

20

40

60

80

100

120

Time [hrs]

Te

mp

era

ture

[°C

]

EP3

EP4

FU3

FU4

XFC3a

XFC3b

XFC4a

XFC4b

0 6 12 18 24 30 36 42 48-20

0

20

40

60

80

100

120

Time [hrs]

Te

mp

era

ture

[°C

]

EP1

EP2

FU1

FU2

XFC1a

XFC1b

XFC2a

XFC2b

0 6 12 18 24 30 36 42 48-20

0

20

40

60

80

100

Time [hrs]

Te

mp

era

ture

[°C

]

EP5

EP6

FU5

FU6

XFC5a

XFC5b

XFC6a

XFC6b

0 6 12 18 24 30 36 42 48-20

0

20

40

60

80

100

120

Time [hrs]

Te

mp

era

ture

[°C

]

EP7

EP8

FU7

FU8

XFC7a

XFC7b

XFC8a

XFC8b

Figure VI-9 Case WSEOL G12 with repositioning manoeuver EPTA transient temperatures

0 6 12 18 24 30 36 42 48-5

0

5

10

15

20

25

30

35

Time [hrs]

Te

mp

era

ture

[°C

]

PPU 1

PPU 2

0 6 12 18 24 30 36 42 4825

26

27

28

29

30

31

32

33

34

35

Time [hrs]

Te

mp

era

ture

[°C

]

PRP

CGCS

0 6 12 18 24 30 36 42 48-5

0

5

10

15

20

25

30

Time [hrs]

Te

mp

era

ture

[°C

]

TSU

ADE

SCE

0 6 12 18 24 30 36 42 4839

39.5

40

40.5

41

41.5

Time [hrs]

Te

mp

era

ture

[°C

]

Xenon Tank 1

Xenon Tank 2

Figure VI-10 Case WSEOL G12 with repositioning manoeuver other components transient temperatures


21

Here below a quick summary of the EPPS piping min-max temperatures is shown:

-60°C

-60°C

-20°C

-20°C

20°C

20°C

60°C

60°C

100°C

100°C

LP Xe tubing to HET

LP Xe to FDV-Test 25.08-35°C 35.66 54.25 +80°C

LP Xe to FDV-PRP 24.91-35°C 37.03 53.05 +80°C

LP Xe to FDV-XTA 22.90-35°C 35.65 56.44 +80°C

LP Xe from FDV-XTA 13.79-35°C 39.60 61.61 +80°C

LP Xe to XTA-1 #1 18.87-35°C 37.89 58.22 +80°C

LP Xe to XTA-1 #2 27.22-35°C 33.58 54.19 +80°C

LP Xe to XTA-2 #1 15.07-35°C 52.21 47.71 +80°C

LP Xe to XTA-2 #2 16.18-35°C 61.23 37.58 +80°C

LP Xe to XTA-2 #3 16.58-35°C 59.52 38.89 +80°C

LP Xe to XTA-2 #4 14.20-35°C 57.76 43.03 +80°C

LP Xe to XTA-2 #5 13.31-35°C 48.48 53.2 +80°C

LP Xe to XTA-2 #6 14.52-35°C 37.33 63.14 +80°C

LP Xe to XTA-2 #7 23.89-35°C 33.40 57.7 +80°C

LP Xe from PRP 14.33-35°C 49.42 51.25 +80°C

LP Xe to HET North 13.0-35°C 56.52 45.39 +80°C

LP Xe to HET 1-2 #1 11.9-35°C 51.87 51.14 +80°C

LP Xe to HET 1-2 #2 12.6-35°C 37.65 64.7 +80°C

LP Xe to HET 1-2 #3 13.47-35°C 35.46 66.06 +80°C

LP Xe to HET 1-2 #4 18.01-35°C 35.43 61.56 +80°C

LP Xe to HET 1 17.80-35°C 47.05 50.14 +80°C

LP Xe to HET 2 #1 21.23-35°C 44.29 49.47 +80°C

LP Xe to HET 2 #2 15.61-35°C 43.98 55.4 +80°C

LP Xe to HET 3-4 17.60-35°C 43.06 54.33 +80°C

LP Xe to HET 3 17.76-35°C 47.99 49.24 +80°C

LP Xe to HET 4 #1 20.67-35°C 39.00 55.32 +80°C

LP Xe to HET 4 #2 23.22-35°C 46.41 45.36 +80°C

LP Xe to HET South #1 15.28-35°C 62.33 37.38 +80°C


LP Xe to HET 5-6 17.92-35°C 42.97 54.23 +80°C

LP Xe to HET 5 19.38-35°C 46.21 49.41 +80°C

LP Xe to HET 6 #1 20.98-35°C 53.08 40.92 +80°C

LP Xe to HET 6 #2 15.92-35°C 40.79 58.29 +80°C

LP Xe to HET 7-8 #1 16.75-35°C 60.03 38.21 +80°C

LP Xe to HET 7-8 #2 14.24-35°C 57.58 43.17 +80°C

LP Xe to HET 7-8 #3 11.7-35°C 55.53 47.75 +80°C

LP Xe to HET 7-8 #4 13.0-35°C 51.99 49.92 +80°C

LP Xe to HET 7-8 #5 20.79-35°C 35.42 58.78 +80°C

LP Xe to HET 7 18.17-35°C 45.55 51.28 +80°C

LP Xe to HET 8 #1 18.21-35°C 41.42 55.36 +80°C

LP Xe to HET 8 #2 24.91-35°C 43.77 46.31 +80°C

-60°C

-60°C

-20°C

-20°C

20°C

20°C

60°C

60°C

100°C

100°C

LP Xe tubing to CGTV

LP Xe from PRP 14.33-35°C 49.42 51.25 +80°C

LP Xe PRP to CGCS #1 15.28-35°C 62.33 37.38 +80°C





LP Xe to CGCS #1 14.04-35°C 38.56 62.39 +80°C

LP Xe to CGCS #2 16.39-35°C 40.51 58.09 +80°C

LP Xe from CGCS #1 26.93-35°C 38.25 49.81 +80°C

LP Xe from CGCS #2 35.09-35°C 29.76 50.14 +80°C

LP Xe from CGCS #3 33.34-35°C 31.39 50.26 +80°C

LP Xe to CGTV 31.19-35°C 32.07 51.74 +80°C

LP Xe to CGTV 31.71-35°C 28.70 54.58 +80°C

LP Xe to CGTV-1 #1 28.92-35°C 27.63 58.45 +80°C

LP Xe to CGTV-1 #2 28.51-35°C 27.06 59.42 +80°C

LP Xe to CGTV-1 #3 30.53-35°C 27.91 56.54 +80°C

LP Xe to CGTV-1 #4 27.22-35°C 56.78 30.99 +80°C

LP Xe to CGTV-2 #1 32.95-35°C 29.06 52.98 +80°C

LP Xe to CGTV-2 #2 31.77-35°C 69.26 +80°C

LP Xe to CGTV 24.76-35°C 33.24 56.99 +80°C

LP Xe to CGTV-3 #1 26.48-35°C 33.01 55.5 +80°C

LP Xe to CGTV-3 #2 27.22-35°C 65.08 22.69 +80°C

LP Xe to CGTV-4 #1 27.67-35°C 31.39 55.94 +80°C

LP Xe to CGTV-4 #2 24.74-35°C 32.09 58.15 +80°C

LP Xe to CGTV-4 #3 24.17-35°C 32.00 58.82 +80°C

LP Xe to CGTV-4 #4 25.94-35°C 31.81 57.23 +80°C

LP Xe to CGTV-4 #5 22.91-35°C 33.26 58.82 +80°C

LP Xe to CGTV-4 #6 27.90-35°C 59.86 27.23 +80°C

Figure VI-11 Equinox COP cases and Safe Mode min-max summary for EPPS piping

-20°C

-20°C

20°C

20°C

60°C

60°C

100°C

100°C

HP Xe tubing

HP Xe from XTA-1 10.6+20°C 6 +50°C

HP Xe from XTA-2 #1 11.7+20°C1 16.58 +50°C

HP Xe from XTA-2 #2 12.5+20°C0 16.88 +50°C

HP Xe from XTA-2 #3 13.49+20°C2 +50°C

HP Xe from XTA-2 #4 15.10+20°C3 +50°C

HP Xe from XTA-2 #5 16.53+20°C3 +50°C

HP Xe from XTA-2 #6 16.07+20°C 6. +50°C

HP Xe from XTA-2 #7 14.39+20°C 4 +50°C

HP Xe from XTA-2 #8 11.7+20°C3 14.76 +50°C

HP Xe to PRP 15.15+20°C 8.1 +50°C


22

-60°C

-60°C

-20°C

-20°C

20°C

20°C

60°C

60°C

100°C

100°C

LP Xe tubing to HET

LP Xe to FDV-Test 27.02-35°C 45.11 42.86 +80°C

LP Xe to FDV-PRP 24.05-35°C 47.77 43.16 +80°C

LP Xe to FDV-XTA 20.80-35°C 47.73 46.46 +80°C

LP Xe from FDV-XTA 11.8-35°C 54.43 48.7 +80°C

LP Xe to XTA-1 #1 17.36-35°C 58.47 39.16 +80°C

LP Xe to XTA-1 #2 23.51-35°C 55.83 35.65 +80°C

LP Xe to XTA-2 #1 14.62-35°C 64.29 36.09 +80°C

LP Xe to XTA-2 #2 14.83-35°C 67.17 33 +80°C

LP Xe to XTA-2 #3 12.8-35°C 69.53 32.57 +80°C

LP Xe to XTA-2 #4 10.4-35°C 70.30 34.22 +80°C

LP Xe to XTA-2 #5 11.6-35°C 68.21 35.16 +80°C

LP Xe to XTA-2 #6 11.6-35°C 64.82 38.49 +80°C

LP Xe to XTA-2 #7 18.06-35°C 61.48 35.45 +80°C

LP Xe from PRP 14.23-35°C 61.15 39.61 +80°C

LP Xe to HET North 13.2-35°C 62.10 39.69 +80°C

LP Xe to HET 1-2 #1 11.6-35°C 56.03 47.33 +80°C

LP Xe to HET 1-2 #2 10-35°C 51.19 53.54 +80°C

LP Xe to HET 1-2 #3 11.3-35°C 50.62 52.98 +80°C

LP Xe to HET 1-2 #4 21.19-35°C 46.50 47.3 +80°C

LP Xe to HET 1 22.71-35°C 51.09 41.19 +80°C

LP Xe to HET 2 #1 27.01-35°C 47.25 40.72 +80°C

LP Xe to HET 2 #2 18.65-35°C 50.00 46.34 +80°C

LP Xe to HET 3-4 21.70-35°C 47.65 45.64 +80°C

LP Xe to HET 3 20.42-35°C 51.47 43.1 +80°C

LP Xe to HET 4 #1 33.37-35°C 42.44 39.21 +80°C

LP Xe to HET 4 #2 37.43-35°C 49.31 28.26 +80°C



LP Xe to HET 5-6 24.82-35°C 66.83 23.34 +80°C

LP Xe to HET 5 29.14-35°C 67.87 17.98 +80°C

LP Xe to HET 6 #1 29.35-35°C 65.68 19.96 +80°C

LP Xe to HET 6 #2 23.98-35°C 67.83 23.18 +80°C

LP Xe to HET 7-8 #1 12.6-35°C 69.74 32.61 +80°C

LP Xe to HET 7-8 #2 10-35°C 70.39 34.16 +80°C

LP Xe to HET 7-8 #3 12.4-35°C 64.72 37.85 +80°C

LP Xe to HET 7-8 #4 14.58-35°C 64.64 35.76 +80°C

LP Xe to HET 7-8 #5 25.12-35°C 61.73 28.14 +80°C

LP Xe to HET 7 24.07-35°C 63.29 27.63 +80°C

LP Xe to HET 8 #1 31.77-35°C 61.35 21.88 +80°C

LP Xe to HET 8 #2 45.63-35°C 58.662 +80°C

-60°C

-60°C

-20°C

-20°C

20°C

20°C

60°C

60°C

100°C

100°C

LP Xe tubing to CGTV

LP Xe from PRP 14.23-35°C 61.15 39.61 +80°C




LP Xe PRP to CGCS #4 10-35°C 70.39 34.16 +80°C


LP Xe to CGCS #1 12.7-35°C 65.82 36.38 +80°C

LP Xe to CGCS #2 15.78-35°C 60.39 38.81 +80°C

LP Xe from CGCS #1 28.34-35°C 49.19 37.46 +80°C

LP Xe from CGCS #2 35.80-35°C 43.69 35.51 +80°C

LP Xe from CGCS #3 34.40-35°C 44.55 36.04 +80°C

LP Xe to CGTV 32.45-35°C 46.74 35.8 +80°C

LP Xe to CGTV 31.44-35°C 47.63 35.92 +80°C

LP Xe to CGTV-1 #1 27.91-35°C 49.48 37.6 +80°C

LP Xe to CGTV-1 #2 26.17-35°C 50.72 38.1 +80°C

LP Xe to CGTV-1 #3 26.89-35°C 51.35 36.75 +80°C

LP Xe to CGTV-1 #4 27.32-35°C 67.64 20.03 +80°C

LP Xe to CGTV-2 #1 33.00-35°C 47.00 35 +80°C

LP Xe to CGTV-2 #2 30.01-35°C 75.33 +80°C

LP Xe to CGTV 24.89-35°C 46.82 43.28 +80°C

LP Xe to CGTV-3 #1 24.41-35°C 43.26 47.32 +80°C

LP Xe to CGTV-3 #2 26.37-35°C 67.55 21.07 +80°C

LP Xe to CGTV-4 #1 25.99-35°C 42.60 46.41 +80°C

LP Xe to CGTV-4 #2 22.26-35°C 43.46 49.27 +80°C

LP Xe to CGTV-4 #3 19.82-35°C 43.66 51.51 +80°C

LP Xe to CGTV-4 #4 22.06-35°C 43.30 49.62 +80°C

LP Xe to CGTV-4 #5 20.06-35°C 43.19 51.73 +80°C

LP Xe to CGTV-4 #6 26.55-35°C 63.63 24.81 +80°C

Figure VI-12 WSEOL F1 min-max summary for EPPS piping

VII. Lessons learnt

A. FU recovery

A major difficulty for the thermal control system is the cooling of the Filter Unit which is attached at the same

common bracket of the HET thruster. During the station keeping manoeuvers, which last up to 60 minutes, a part of

the dissipated heat of the thruster is evacuated through the bracket and into the radiator. The entire bracket increases

in temperature which results in too high interface temperatures for the FU.

-20°C

-20°C

20°C

20°C

60°C

60°C

100°C

100°C

HP Xe tubing

HP Xe from XTA-1 10.6+20°C 6. +50°C

HP Xe from XTA-2 #1 13.2+20°C 9.8 +50°C

HP Xe from XTA-2 #2 12.8+20°C 11.5 +50°C

HP Xe from XTA-2 #3 10.8+20°C 14.71 +50°C

HP Xe from XTA-2 #4 10.7+20°C 15.46 +50°C

HP Xe from XTA-2 #5 13.69+20°C 14.01 +50°C

HP Xe from XTA-2 #6 14.67+20°C 12.1 +50°C

HP Xe from XTA-2 #7 13.97+20°C 11.1 +50°C

HP Xe from XTA-2 #8 11.9+20°C 4 +50°C

HP Xe to PRP 15.40+20°C 5. +50°C


23

Figure VII-1 FU position and thermal strap assembly

The lower FU, attached to the HET bracket below the lower HET thruster gets too hot and out of specification in

some cases. The worst one is the WSEOL F1, especially for FU 5.

Several solutions have been investigated and eventually a thermal copper strap assembly has been chosen due to

robustness and cost efficiency. The thermal strap is mounted between the filter unit bracket and the Surface

Mounted Heat Pipe (SMHP), on the South P/F radiator (yellow in Figure VII-1, in the middle). The results for the

HET assembly 5-6 in the hottest case is reported in Figure VI-7 and Figure VI-8: it is a Winter Solstice EOL case,

the Sun is on the South radiator and a criticality on a filter unit has been encountered. This solution has been

implemented for all the 4 lower FUs of the S/C.

B. PPU and reaction wheels relative position

Typically, the reaction wheels dissipation profile is a sinusoid. In SGEO HAG1 there are four RWs and they are

on the south side, very close to a PPU (nr. 1 in Figure VII-3). If EPPS units are too close to the RWs, it is preferable

not to fire in phase to one of the RWs dissipation profile, otherwise huge temperatures peaks can be encountered.

0 6 12 18 24 30 36 42 4810

15

20

25

30

35

40

Time [hrs]

Te

mp

era

ture

[°C

]

PPU 1

PPU 2

Figure VII-2 Case WSEOL F1 PPU temperatures (nominal case)

0 6 12 18 24 30 36 42 4810

15

20

25

30

35

40

45

Time [hrs]

Te

mp

era

ture

[°C

]

PPU 1

PPU 2

Figure VII-3 Case WSEOL F1 PPU temperatures, firing in phase to RW1 dissipation profile

If we compare Figure VII-2 and Figure VII-3 it is possible to understand the temperature increase in the PPU1. Here

below the impact of the firings with respect to SGEO HAG1 RW1.


24

0 6 12 18 24 30 36 42 480

5

10

15

20

25

30

35

40

45

50

Time [hrs]

Te

mp

era

ture

[°C

]

RW1 nom

RW1 PPURW

Firing nom

Firing PPURW

Figure VII-4 Case WSEOL F1 RW1 temperatures comparison

C. EPPS piping thermistor bracket

For the heater lines Xenon South and East the presence of the bracket is represented by an arithmetic node per

each thermistor. So, an additional link has been implemented between the thermistor and the piping, as shown in the

next picture.

Figure VII-5 Piping thermistor bracket

Even if no considerable changes have been detected after the implementation of the thermistor support bracket, in

terms of temperature or heater duty cycle variations, it is preferable to keep the implementation in order to avoid

errors in detecting the temperature in a wrong location.

D. OSR degradation due to EPPS

The HET thrusters firings cause a degradation in the radiators performance. It has been calculated the thickness of

the layer deposited on the Optical Solar Reflector (OSR) due to the back sputtering of the solar panels eroded

materials. Two thrusters causing the highest deposition rates and placed at adjacent corners of the OSR have been

considered. The OSR performance degradation is translated in the increase of the absorptivity α when the thickness

of the deposited layer grows. At system level, the degradation of the OSR performance has been considered using

0.31 for α coefficient in a semicircle of 1 m in radius centered at the thrusters location. The OSR degradation is

therefore modeled with margin in the system thermal analysis. The darker zones in the next picture near the HET

closure bracket are due to the effect of the HET thruster firing contamination. This phenomenon is considered only

in EOL. The OSR degradation is simulated considering an absorptivity of 0.31 instead of 0.26.


25

Figure VII-6 OSR thermo-optical properties degradation

This degradation causes an increment of the solar absorbed flux and, consequently, of the internal components

temperatures, anyway, within the allowable limits of the units themselves.

E. HET thrusters piping heater lines

On each corner of the S/C the bracket hosts two thrusters, one belonging to the main branch and the second one

to the redundant. Each thruster piping final segment is controlled by independent lines, instead of by a single one, in

order to avoid over-temperatures on the non-operative branch.

VIII. Conclusions

SGEO HAG1 is a pioneer for his class. It is not the first time that a telecom S/C hosts three different propulsive

systems, but, for sure, it is the first time that a telecom satellite has this small size. So the difficult task of the TCS is

to make them coexist also in a smaller space. Anyway, SGEO HAG1 EPPS TCS design works properly, according

to the simulations. Specified operating temperatures are met for units in all the design cases resulting in comfortable

positive margins. All the discussed recovery actions have been implemented successfully. Further, temperatures

experienced by the units in the repositioning cases does not pose any limitation in the use of the sub-system.

Acknowledgments

The authors want to acknowledge the entire thermal department of CGS, which supported the analysis and

documentation execution, the OHB System one and the whole SGEO team. A sincere acknowledgment goes also to

Philippe Delouard and his team of RUAG S.

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