cold gas microthrusters experimental developments g ...eotvos.dm.unipi.it/tasi gg presentation...

All rights reserved © 2009, Thales Alenia Space

BU OOS1

Cold gas microthrusters experimental developments

G. MatticariTAS-I (IUEL) Firenze


BU OOS2

CGPS on GG CGPS on GG UnitsUnitsElementsElements identificationidentification

The CGMTS for GG includes the following major elements:

•• Propellant tanks (not part of the TASPropellant tanks (not part of the TAS--I FI subI FI sub--system)system)

•• Pressure RPressure Regulationegulation Stage ( Stage ( PRSPRS ))

•• MicroMicro--Thrust Actuation Stage ( Thrust Actuation Stage ( MTASMTAS ))

•• MicroMicro PropulsionPropulsion ElectronicsElectronics ( ( MPE MPE ) )

•• ElectricalElectrical HarnessHarness

•• PipeworkPipework, , Supports, standSupports, stand--offs& Bracketsoffs& Brackets


BU OOS3

CGMTS CGMTS heritageheritage

The GAIA Micro Propulsion system (MPS)GAIA Micro Propulsion system (MPS), currently under qualification at TAS-I, is a reference design/technology for realizing the GG CGMTS.

The heart of the GAIA MPS is the Proportional Micro Thruster (MT).

The MT is an innovative Cold Gas Thruster whose development has required overcoming numerous technology challenges such as:

Developing an actuation valve capable of regulating the gas mass flow in a continuous and progressive way, on the basis of a control signalMeasurement of very low mass flows (as low as 0.001 mg/s of N2)Measurement of mass flow over 3-order-of-magnitude dynamic rangeImplementation of a PID closed loop control system in which the actuator is the regulation valve and the sensing element is the Mass Flow SensorIntegration of the Valve + MFS in a very compact and lightweight structureDeveloping dedicated software for the thrust control algorithmsCoping with the very challenging requirements of the GAIA mission


BU OOS4

CGMTS CGMTS heritageheritage

For the GGGG application a significant variation is introduced w.r.t. GAIA:Use of an EPR (Electronic Pressure Regulator)EPR (Electronic Pressure Regulator) instead of a MPR (Mechanical

Pressure Regulator) for realizing the PRS (Pressure Reduction & Regulation Stage)

The main advantages of an EPR based on regulation valves as actuating elements include:

Fully European technology (key components are TAS-I products)No ITAR Export/Import problemsExtremely low leakage (at least one order of magnitude better than the MPR)Very low ripple in the regulated low pressureHigh degree of flexibility (regulated low pressure selectable according to a specified set point) Reduced mass and dimensions


BU OOS5

CGMTS on GG CGMTS on GG preliminarypreliminaryarchitecturalarchitectural sketchsketch

6+6 MT’s are connected to the same PRS reduced pressure node. Each of the 2 thrusting locations (cluster) has 3 nominal and 3 redundant thrusters.

Separate propellant ducts are foreseen for each thruster in order to prevent cross-talk effects


BU OOS6

PRS PRS OverviewOverview

HP RIV as key element of HP RIV as key element of the PRSthe PRS

• The HP RIV is a normally closed device which provides leak tight capability when de-energized

• The piezo-actuator is a coaxial stack of piezoceramic elements able to generate both the force to open the valve against the antagonist spring and the necessary stroke to move the

plunger that opens the orifice

• When operated in closed loop control with a pressure transducer the HP RIV allows analog control of the operational low pressure at user inlet.

• The regulated low pressure can be actuated according to a selected set-point

• The piezo actuator steady state power consumption is very low (< 100 mW ) and the valve design is compact and lightweight

View of PRS Internal View of PRS Internal fluidic Components fluidic Components


BU OOS7

Micro Thruster (MT) keyFunctions

To actuate (together with the control electronics) the closed loop control of the propellant mass flow and thus the control of the generated micro-thrust, that can be established according to a selected set-pointTo provide isolation from the pressure inlet when de-energizedTo provide temperature monitoring of valve and nozzle, for in flight corrections of temperature effects on the IsTo provide the propellant mass flow monitor for insertion in the telemetry


BU OOS8

Micro Micro ThrusterThruster (MT) (MT) configurationconfiguration

MT cross section CAD view

MT series arranged fluidic components

MT couple (nominal+ redundant) accommodated on the L shaped mechanical support

MT EQM model assembled for the qualification Campaign vs. GAIA requirements


BU OOS9

ThrusterThruster Valve (TV) Valve (TV) OverviewOverview

The TV is a LP RIV which provides isolation against low pressure (few bar) with low leakage, and allows precise – analog – control of the propellant flow during operation, taking advantage by piezo- technology actuation (power consumption (< 100 mW) mechanism.

In the TV a micromicro--nozzle nozzle is realized through an electro-erosion process and integrated in the valve body, downstream the exit orifice.

The TV nozzle has been designed and validated also through a dedicated computer modelization and simulation

CAD view of theTVEngineered Model for

GAIA MPS

TV Nozzle (cutaway) close upTV EQM for GAIA MPS


BU OOS10

Mass Flow Mass Flow SensorSensor (MFS) (MFS) OverviewOverview

• Provides the actual mass flow rate at the MT inlet, strictly related to the generated thrust level.

• Detects the “temperature unbalance” in presence of the gas mass flow, between two thermometers, while a constant amount of power is provided in between.

• Si Chip technology: a heating element is positioned in between the upstream and downstream temperature sensing elements (thermo-resistors)

• inside the Si chip, two other temperature sensors are realized for thermal stabilization• the sensor for monitoring of bulk surface temperature• the sensor for the monitoring of the gas temperature

• MFS Dynamic Range: about 3 order of magnitude• MFS Frequency/Time response: 300 Hz bandwidth

Integration of the MFS elements inside the

Mech. housing

Assembled MFS

MFS implemented in a Si Chip (new layout)


BU OOS11

MPE MPE OverviewOverview & & FunctionsFunctions

•Drive and commute 6+6 LP On/off insulation valves (based on TAS-I LP RIV)

•Drive and commute 2 On/Off insulation HP piezo valves(based on TAS-I HP RIV)

•Acquire signals from 4 Pressure Transducers ( 2 HP + 2 LP )•Drive 4 piezo-valves (TAS-I HP RIV) for pressure regulation.•Act a control loop on one of these valves, while the second one is kept open ( the remaining two in the redundant branch are un-powered )

•Acquire signals from 12 Mass Flow Sensors, 6 at a time•Drive 12 piezo-valves (Thruster valves) for thrust control, 6 at a time

•Act a control loop on 6 of these valves (the remaining 6 are un-powered)

•Acquire auxiliary monitors (temperatures, voltages, …)

Driver 1

J02J01 J03

Driver 2

J05J04 J06

Co ntrol + monitorPower

J15J14 J08J07 J09J10

Driver 3

J12J11 J13


BU OOS12

CGMTS CGMTS BudgetsBudgets

Mass Budget

No of items

Item mass (kg)

Continmgency(kg)

Item mass withContingency(kg)

MT’s 6+6 4,4 0,44 (10%)

4,8

MT’s brackets

6 0,6 0,12 (20%)

0,7

MPE (nom+red.)

1 box 3,5 0,7 (20%)

4,2

Electricalharness

1 set 0,5 0,1 (20%)

0,6

PRS (2 branches)

1 box 4 0,8 (20%)

4,8

Pipingfittings and brackets

1 set 1,3 0,26 (20%)

1,6

Total CGMP Dry Mass

14,3 2,4 16,7

Power Budget

Total + 20% Cont.

On the MPE

Stand-by 7.5 W 3.6 W

Operational 25 W 9.6 W

EnvelopeBudget

Dimensions(mm)

MT 184,3 x 62 x 52,5

PRS 300 x 300 x 150

MPE 250 x 150 x 120


BU OOS13

GG GG RequirementsRequirements forfor CGMTSCGMTS

Parameter Unit Requiredvalue

Notes Comparison with is achievable by GAIAMPS

Maximum thrust

Max Thruster responsetime

Resolution (quantization

Max noise

Scale factor error

Command update rate

Specific Impulse s ≥60 Same of GAIA

Centrifugal Acceleration g <4.4 GAIA Design suitable for withstanding the GG centrifugal acceleration

Total impulse

Minimum thrust

Thruster Vector stability

µN ≥150 up to 500 µN

msec 40 @ commanded step (up & down) ≥60 mN

about 100 ms: from T1 to T2 if T1≠0< 300 ms: from 0 to T2

µN 24 TBC, not critical 1 µN achievable with the current GAIA Design

µN/√Hz 18 Around 1 Hz(reffered to the static noise)

1 µN/√Hz from 0.01 Hz to 1 Hz0.1 µN/√Hz from 1 Hz to 150 Hz

% 12 Peak Few %

Hz 10 1 Hz; Nice to have up to 8 Hz

Ns 4500 @150 µN total tonis about 8300 h;

About 10000

µN ≤10 TBC 1 µN

rad 0.17 Peak at 60 No data available at the moment


BU OOS14

ThrustThrust CommandCommand rate & rate & ResponseResponse TimeTime

This GG requirement (10 Hz) is significantly different w.r.t GAIA(1 Hz) The updating of the commanded thrust level every 100 msec:

possible when passing from T1 to T2 if T1≠0If T1 =0 the thrust updating can be implemented within 300 ms

Means for increasing the command rate frequency with design modifications w.r.t GAIA

Increase the computational power of the MPE (significant modification)Increase the cut-off frequency of the Low Pass Filter Modify the PID Closed loop Control Parameters/StrategySlight modifications (TBC) to the TV actuation mechanism

Joint simulation (Thrust closed loop control performance model) and experimental activities necessary to characterize the thrust actuator dynamic behavior


BU OOS15

CentrifugalCentrifugal AccelerationAcceleration

• The direction of the centrifugal acceleration is expected “not” in the thrust direction in any operational flight situation.

• Should the centrifugal acceleration result directed in the same direction of the thrust, the correspondent force would act in opposition to the mechanical force exerted by the spring that maintains the valve fully closed,

• Force exerted by the spring : about 10 N (corresponding to about 1 kg)• mass of the valve actuator: 10 grams (0.01 kg)• Centrifugal acceleration: 17.4 g• Centrifugal force acting on the Valve actuator: about 0.174 kg

• Centrifugal Force (0.174 kg) << Spring strength (1 kg),

• no significant risk of valve opening due to the centrifugal force practically exists


BU OOS16

ThrustThrust ParasiticParasitic NoiseNoise

PSD of force relevant to piezo actuator movement during regulation( vertical axis is µN/√Hz )

10-4 10-3 10-2 10-1 10010-3

10-2

10-1

100

101PSD

Frequency [Hz]

Forc

e [ µ

N/ √

(Hz)

]

Thrust Noise at 100 µN measured at the TAS-I Turin nanobalance facility

TV and Displacement Detector accommodated in the vacuum chamber

Thrust noise due to gas flow fluctuationsThrust noise due to gas flow fluctuations

Thrust noise due to mass movementThrust noise due to mass movement

Use of a compensation disk within the TV actuator possible as an additional provision to reduce the noise due to piezo-actuator movements


BU OOS17

ThrustThrust Scale Scale FactorFactor ErrorError

4100 4120 4140 4160 4180-30

-20

-10

0

10

20

30

Time [s]

Forc

e [ µ

N]

NB measure

Sketch of the test setSketch of the test set--up at the up at the nanonano balancebalancePulsed Thrust test (100Pulsed Thrust test (100--150 150 µN) at the N) at the nanonano balancebalance

Assessment of the scale factor error has been performed for GAIA• Error due to the Thrust balance performance: 3-4%• Errors due to calibration conditions, in flight different conditions, etc. : <1%• Error due to quantization (thrust expressed with a 14 bit code): 0.06 µN• Error related to the SW processing: ±0.1 µN

GG figure for the scale factor error is widely higher than the figure/s resulting from GAIA. So scale factor is not a critical parameter for the CGMTS on GG.


BU OOS18

CGMTS TRL Status CGMTS TRL Status

Program/Mission and Contractor

Status CGPS Operation

For GAIA this module is called MPFM and is procured from Astrium UK and is a Mechanical Pressure Regulator (MPR);

PRSPRS 44

The PRS here considered (and for which the TRL is identified) is an Electronic Pressure regulator based on TAS-I High Pressure PiezoValve;

MPEMPE 66 At begin of 2009 a MPE EQM for GAIA program is ready for being submitted to the Qualification Test campaign at Unit level

MTASMTAS 66 At begin of 2009 2 MT EQM’s for GAIA program are ready for being submitted to the Qualification Test campaign at Unit level


BU OOS19

CGMTsCGMTs for GG Development Plan for GG Development Plan


BU OOS20

GG Integrated CG Propulsion System

A significant optimization of the GG Propulsion Architecture can be proposed an “integrated” CGPS, including:

• Unified PRS (used for the Pressure regulation of both the Micro Thrusters and Auxiliary Thrusters

• Unified MPE (both for Micro Thrusters and Auxiliary Thruster control)

• Micro Thrusters (6 nominal and 6 redundant) used for the actuation of the drag-free control

• Auxiliary Propulsion Thrusters (4 nominal and 4 redundant) used for the initial attitude stabilization and for the spin-up operation


BU OOS21

GG Auxiliary Propulsion requirements

Parameter Unit GG requirements

Comments also considering what is achievable for Small GEO

Max. Thrust N > 0.5 50 mN at about 2 bar inlet pressure; using an EPR with a regulated pressure set point of 10 bar would produce about 0.25 N of thrust

MIB Ns < 0.005Specific Impulse s > 60 Small GEO uses Xe; the TV can

operate also with N2 at the desired Is

Centrifugal Acceleration

g < 4.4 Mechanical design of Small GEO suitable for this requirement

No. of Cycles TBDNo. of thrusters for each assembly

4 2 assemblies as from Small GEO architecture


BU OOS22

Integrated CGPS architecture

72 x Φ66 mm120 g

Cold Gas On/off Thruster

nominal thrust (2 bar) : 50 mN)

Cold Gas Micro Thruster

cold gas microthrusters experimental developments g ...eotvos.dm.unipi.it/tasi gg presentation...

Documents