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Propulsion Instruments for Small Hall Thruster Integration International Electric Propulsion Confere

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Validated model is the tool used to extend test flight results to operational missions. ... due 10/02, schedule set by sensor tests. Sensor fabrication ... – PowerPoint PPT presentation

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Title: Propulsion Instruments for Small Hall Thruster Integration International Electric Propulsion Confere


1
Propulsion Instruments for Small Hall Thruster
IntegrationInternational Electric Propulsion
ConferenceIEPC-01-169, 16 Oct 01
  • L.K. Johnson
  • JPL
  • D. G. Conroy
  • California Institute of Technology
  • D.R. Bromaghim and G.G. Spanjers
  • AFRL

California Institute of Technology
2
Motivation for Instruments
  • Propulsion Flight Sensors Are a Critical Part of
    AFRLs TechSat 21.
  • On-orbit measurements are the only valid way to
    collect necessary data.
  • Ground-based tests dominated by facility effects.
  • Needed to assess impact on future USAF missions.
  • Objective Develop integration handbook for Hall
    thrusters on USAF spacecraft.
  • Acquire on-orbit data on plume properties and
    surface contamination.
  • Compare with ground tests and MS results.
  • Generate and distribute technical
    recommendations.
  • Sensors
  • Plume probes 1 Ion mass/energy spectrometer, 2
    electron probes.
  • Induced environment monitors 10 radiometers, 10
    photometers, 2 solar cells.
  • 3 ship-sets, mass constrained to 1.5 kg. each
    power lt 15 W-h per rev.

3
Relation to modeling
  • Validated model is the tool used to extend test
    flight results to operational missions.
  • Combined effort to extend models from inside
    thruster through 3D spacecraft effects
  • SAIC EWB
  • Fife, et al. underway
  • Boyd

Mikelledes EWB results
4
Organization
  • Program Management
  • Mission Analysis and System Engineering
  • Interface Requirements Management
  • Spacecraft IT, Launch, On-orbit Support
  • Data Reduction Analyses

AFRL/PRSS POC Daron Bromaghim
Measts - AFRL/JPL POC Lee Johnson
Micro-PPT - AFRL POC Greg Spanjers
HTS - TRW POC Bob Vondra
  • Thruster Design, Development, and Test
  • Mission Analysis and System Engineering
  • Spacecraft IT
  • Launch/On-orbit Ops Support
  • Program Management
  • Mission Analysis and System Engineering
  • PPU Development
  • Spacecraft IT
  • Launch/On-orbit Ops Support
  • Sensor Design, Development, and Test
  • Modeling, Calibration Tests
  • Mission Analysis and System Engineering
  • Spacecraft IT
  • Launch/On-orbit Ops Support

Busek
Moog
W.E. Research
TBD Contractor
Broad-Reach Engineering
TBD Contractor
  • Thruster
  • Cathode
  • Launch/On-orbit Support
  • Xenon Feed System
  • Thruster Devt Support
  • Performance, Life Tests
  • Flight Thruster Fabrication (TBD)
  • Acceptance Tests (Thermal, Vibe, etc.)
  • Sensor Fab
  • Environment Tests
  • Interface Electronics

5
Instrument types
Ion and electron sensors receive signal from
thruster.
Solar cell, radiometer, and photometer are
exposed to thruster environment, use sun as
constant source.
6
TechSat 21 Flight Orientation
Zenith deck (to sun)
Velocity vector
Ion Probe
Hall Thruster
Micro-PPT
Electron Probe
7
TechSat 21 Propulsion Instrument Layout
- Ion sensor input 20 cm radial, 80 deg from
centerline - Electron sensors 1 boom mounted, 1
current collector patch. - Radiometer,
Photometer, Solar cell distributed near-to-far
around spacecraft. - Likely addition of
bill-board to allow propulsion panel sensors to
view constant sun.
8
Ion Spectrometer Overview
  • Motivation
  • Understanding of the effect of EP on S/C
    observational measurements
  • Determination of the environment experienced by
    S/C components
  • Validation of theoretical models in the backflow
    region
  • Status
  • Nearly all prototype components fabricated
  • Thermal stabilization of magnetic field underway
  • Input optic tested agrees with simulations
  • Sequential assembly component testing pending

9
Ion Spectrometer Design
  • Constraining DoF
  • Apertures constrain 5 of 8
  • Electric field defines a ratio
  • Magnetic field defines a ratio
  • Other features
  • Input optic
  • Collimation optic

10
Ion Spectrometer E/q selection
  • Energy Analyzer
  • Nested hemispheres allow ions of certain m/q to
    pass
  • Most of the volume of a hemisphere is unused if
    apertures are employed
  • Use slice of hemisphere to reduce mass and volume
  • Apply resistive film between electrodes to
    control field fringing

11
Ion Spectrometer m/q selection
  • Energy Analyzer
  • Larmor radius of ions with uniform kinetic
    energy dependent on vm/q
  • 90 deflection leads to parallel ion paths
  • Trade magnet mass for ion mass resolution (ion
    streams diverging)

12
Ion spectrometer potential scheme
13
Electron Probe and Current Collector
- Ramp V /- 50V, measure I to metallic electron
collector exposed to plasma environment, 0.25 mA
to 1 mA. - ES1 1 foot fixed boom, propulsion
panel - ES2 5 cm patch on SA A-frame restraint
or zenith panel. - Design of ES1 and ES2
underway. - Composite boom, perhaps mounted on
billboard panel. - Sphere welded SS or
polymer, plated or carbon coated. - Patch
Plated foil bonded to Kapton substrate. Possible
fab by GSI. - Prototypes early 02. - Test
against thruster later in the year.
14
Solar Cell Sensors
- Examine cell characteristics as a function of
thruster exposure. - Same CIGS technology as main
TS21 array -- multiple suppliers. - Cell
footprint 1.5 x 7 - Cell output 2A, 0.5V. -
Possibly smaller cells available. - Very thin,
mass 2g. - Add insulating substrate for body
mount, wires, T sensor. - Built prototypes this
summer (Dan Perea). - Trade of I-V curve vs. OCV,
SCC.
15
Solar Cell Measurement Circuit
- Need 0.1 ohm for SCC. - Open all for OCV. -
Cell performance changes with T, circuit needs to
work over the expected range. - Green lines of
constant load. - Switches in parallel give
multiple combinations. - Possible use of 6
switches to better determine curve.
16
Photometer sensor Measures optical transmission
loss or gain.
UDT
IRD
- PC board mount, TO-5, TO-18, TO-8 all meet mass
requirements. - Packaging somewhat taller than
case. - Est. 1 cm x 1 cm x 1 cm - Reverse bias
at -3 to -12 V - Bond or coat optical materials,
selection in process. - Supplied by UDT Sensors,
Inc. or International Radiation Detectors, Inc.
1 cm
TO-5
17
Radiometric sensor Measures changes in solar
absorptivity, a, and IR emissivity, e.
ESEX radiometer
Spacecraft coating material - Kapton -
Al/K - Gold - White paint
Incident solar irradiation
Thermal conductor (Al, etc.)
Insulator
0.3-0.5 inch
- Signal is T1 and T2. - Good history on ESEX. -
Slow time response hampered analysis. - Reducing
size improves time response, but how to keep
T1-T2 large?
T1 T2
Spacecraft
18
Radiometer concept
Wire gauge size change encapsulated in RTV and
staked to baseplate.
Disk 10 mils thick coating 2-3 mils
AD590 chip
28 gauge to spacecraft
Kapton ring 1 mil thick
3 mil wire
Becca Kim James Turnbull Summer 2001
19
Temperature sensor
Intersil AD590
- Die 0.044" x 0.066" or 1.1 x 1.7 mm - Pads
about .15 mm square - Approx weight 2.2 mg
20
Radiometer prototype
21
Radiometer modeling
Disk heat equation mcp dT/dt dQ/dt (sun
radiative) dQ/dt (spacecraft radiative) - dQ/dt
(disk radiative) dQ/dt (wire conductive)
dQ/dt (standoff conductive)
22
Propulsion Instruments Block Diagram
23
Sensor I/O
Inputs
Instrument
Outputs
(2) 8 point I-V curve
Solar Array Instruments (2)
4 resistor load switching
(2) T sensor /- 3 C
24
Electronics
  • BroadReach Engineering - contractor.
  • Dimensions 8 x 7 x 1.2 inch.
  • Mass 650 g.
  • Pre-amplifier board in ion sensor box.
  • Connector 1 x 100 - pin
  • Location Inner surface of propulsion panel.
  • RS-422 command and data interface to spacecraft.
  • 12 W standby, 24 W during firings.

25
Propulsion Instruments Summary
  • Engineering path to flight
  • Most sensors either in prototype or test.
  • Electronics Preliminary Design Review 10/4/01.
  • Prototype electronics available 3/02 for test and
    use in ground tests of sensors.
  • Flight electronics due 10/02, schedule set by
    sensor tests.
  • Sensor fabrication starting mid-02.
  • Diet to achieve mass lt1.5 kg.
  • Science path to flight
  • Update and progress on models.
  • Ground test program with prototypes schedule.
  • Analysis and review of models, leading to
    predictions for flight results.
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