the r2 mission - digitalcommons.usu.edu

The R2 mission

R2 before shipping

Mission

Technical demonstration of Exotrail’s ExoMG™ Hall Effect Thruster

Stakeholders

Satellite manufacturer and operator: NanoAvionicsCustomer and payload operations: Exotrail

Orbit

Launched from India on 7th November 2020Altitude: 571 km - Inclination: 36.9° - Eccentricity: 0.001

The R2 mission

Mission


Stakeholders


Orbit


R2 before shipping

R2 before shipping

The R2 mission

Mission


Stakeholders


Orbit


6

Subsystem for gas distribution towards the thrusterhead

Propellant Management System

A Tank Assembly for propellant storageTanks

The thruster head generates the thrust. It hosts the anodeand cathode assemblies

Thruster Head

The command and control subsystemIt manages the power and the communication with thesatellite.

Thruster Control Unit

Propulsion system overview

7

Other subsystems

E l e c t r o n i c s

Power conversionBattery voltage → usable voltage for the thruster6-32 V input voltage

ControlCAN, RS485, RS422 communication protocolHighly configurable commandsComplete system monitoring with 15+ temperature monitored

Propellant storageStores high-pressure xenon gas in certified tanks for propellant density and increased thruster performance

Mass flow regulationRegulate the pressure and the mass flow to the thruster head

P r o p e l l a n t m a n a g e m e n t

8

Hall effect technology

(1) Electrons are emitted by the cathode

(2)They are captured inside the anode channel by a strong magnetic field

(4) The electron density locally generates a gradient

of electric field that accelerates the ions

(3) The electrons collide and ionize the propellant

(5) A fraction of the electrons are used to recombine

with ions in order to neutralize the plume

Xe+

e-

Thru

st/po

wer r

atio (mN/kW)

specific impulse (s)

10

25

50

0 1000500 3000

50 mN/kW | 1000 s

Good EfficiencyHighest Thrust

A high-thrust thruster

FEEPVATGITRFPT

RFPT

RFPT : Radio Frequency Plasma ThrusterGIT : Grid Ion Thruster

VAT : Vacuum Arc ThrusterFEEP : Field Emission Electric Propulsion

EXOMGTM

Commissioning of the satellite

Passive checks

power the propulsion unit for several days to gather data

Monitoring of the temperatureMonitoring of the power consumptionMonitoring of the propellant management system

Temperature of the control unit

Temperature of the thruster head

Pressure in the tanks


Passive checks





Temperature is within the acceptable limit for electronics and the CONOPS is not impacted



Passive checks





Temperature is within the acceptable limit for the thruster and the CONOPS is not impacted (no heating required)



Passive checks





10% of pressure oscillations and it remains well within design marginsThe pressure before and after launch indicates that no leak occurred in the meantime



Active checks

Start-up procedure performed step-by-step

Controlling the mass flow to the anode and to the cathodePowering the cathode heater and the anode with trying ignitionTrying the first ignition

Cathode and anode mass flow

Cathode heating

Anode polarization


Active checks




Cathode heating

Anode and cathode mass flow are nominal and as calibrated on the ground

Two independent lines for the anode and the cathode with the possibility to control the mass flow in time Anode polarization


Active checks




Cathode heating

Cathode heating is nominal, as calibrated on the groundNo impact of launch on the heater

Anode polarization


Active checks




Cathode heatingAnode is polarized as expected

Anode polarization


First ignition attempt

Cathode hotPropellant flowing through anode and cathodeAnode polarization

Nominal ignition of the thruster at the first trialFull duration firing of 10 minElectrical and propellant behavior as expected

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Executing the commissioning requires:

- A plan, with corrective actions in case something goes wrong- Many observables- On-ground references

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Operations and performance estimation

Operations shared between 3 partners- Exotrail operates the payload and provide flight dynamics

solutions through its ExoOPS™ - Operations software- NanoAvionics operates the platform- Leaf Space operates the ground segment

EXOOPS™ - Operations

Events management

Telemetries monitoring

Commands generation

Flight Dynamics

Compute, display and give access to events (eclipses, nodes crossing, firings, etc.)

Store, arrange, display and create alerts on the data gathered from the payload and the platform

Generates commands for the payload and manage modes of subsystems of the platform

Handles orbit determination and maneuver planning

20


Satellite tracking is key

Results

SpacetrackTLE

Unscented Kalman Filter

Maneuver plan

Thruster telemetriesAOCS telemetries Operational

TLE

GPS NMEA

Mission Planning

Orbit wrongly estimated→ no contact with the satellite→ need for powerful orbit determination algorithms

Semi-major axis evolution during a maneuvering phase:Estimated from GPS dataGiven by TLE

Along track error during a maneuvering phase:Along track errorDates of TLE

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Estimate the performance is key

Results

Firing # Expected thrust [mN]

Realized thrust [mN]

1 1.8 2.252 1.8 2.153 2.4 2.894 2.4 3.025 2.4 3.12

Thrust measured in-space higher than measured on the ground

Explanations: Facility effects – background pressure, conducting walls, etc.Thruster Performance

➢ Required for mission planning➢ Objective of a demonstration mission

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Executing the mission with propulsion on-board requires:

- Positioning data generated by the satellite- Automated orbit determination algorithms with propagation taking into account maneuvers- Performance estimation algorithms

the r2 mission - digitalcommons.usu.edu

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