Title: Propulsion Instruments for Small Hall Thruster Integration International Electric Propulsion Confere
1Propulsion 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
4Organization
- 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
- Thruster Devt Support
- Performance, Life Tests
- Flight Thruster Fabrication (TBD)
- Acceptance Tests (Thermal, Vibe, etc.)
- Sensor Fab
- Environment Tests
5Instrument types
Ion and electron sensors receive signal from
thruster.
Solar cell, radiometer, and photometer are
exposed to thruster environment, use sun as
constant source.
6TechSat 21 Flight Orientation
Zenith deck (to sun)
Velocity vector
Ion Probe
Hall Thruster
Micro-PPT
Electron Probe
7TechSat 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.
8Ion 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
9Ion 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
10Ion 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
11Ion 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)
12Ion spectrometer potential scheme
13Electron 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.
14Solar 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.
15Solar 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.
16Photometer 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
17Radiometric 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
18Radiometer 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
19Temperature 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
20Radiometer prototype
21Radiometer 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)
22Propulsion Instruments Block Diagram
23Sensor I/O
Inputs
Instrument
Outputs
(2) 8 point I-V curve
Solar Array Instruments (2)
4 resistor load switching
(2) T sensor /- 3 C
24Electronics
- 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.
25Propulsion 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.