1. Tethered Satellite Propulsion
Icarus Student Satellite
Goals – What, How, and Why
ProSEDS

2. Topics What is Tethered Propulsion Why do we need Tethered Propulsion
How do we implement the model for Tethered Propulsion

3. Why Normal Satellite Missions Launch rocket/space shuttle
Shuttle deploys payload (usually satellite)
Satellite performs function, and then eventually loses enough momentum to fall out of orbit
If Satellite needs more time in space, fuel must be shipped up to the satellite
Bottom Line: needs fuel

4. Why Disadvantages of Fuel: We need a propellant-less propulsion model
Expensive
Refueling MIR space station costs estimated at about $1 billion.
Limited Supply
Earth is already running out of fossil fuels, nuclear/renewable resources not yet a viable solution for propulsion in space
We need a propellant-less propulsion model

5. How Earth has magnetic field Earth has electric field
Basic law of Physics :
F = B x I
If we could utilize the Earth’s electric and magnetic fields by driving current in the right direction, then we can generate an electromotive force sufficient for use in orbit

6. How Keep it simple: Generate current along a straight line
Use a taut conducting wire (Tether) to channel the current
Tether needs to be kept taut and oriented properly in the magnetic field
Another basic rule of physics: if two masses connected by a tether are in orbit, the masses will align themselves along the local vertical regardless of the starting orientation.

7. Potential Uses

8. What ProSEDS – Propellant-less Small Expendable Deployer System
Drives current through the tether
Deploys endmass (Icarus)
Icarus (ProSEDS Endmass)
Dead weight (~20 kg +/- 0.4 kg)
Used to study tether physics
Possible backup in case of ProSEDS failure

9. Icarus Student Satellite
First (real) student built, designed, and tested satellite
Part of the tethered satellite propulsion model
Scheduled to be launched March/May 2001
Advantageous since it is an instrumented endmass as opposed to a passive dead weight
Helps prove NASA’s “cheaper/faster/better” solution model

10. What Payload GPS, Magnetometer – provide location information
GPS unit uses the GPS satellite network
Magnetometer compares the magnetic readings at present location against the current model of the Earth’s magnetic field
Together, both units provide a complete measurement of the physics of the Endmass

11. What Control and Data Handling Subsystems
Octagon systems 386 board assimilates the information, sends it to the transmitter
Power: 3.0 W
Memory: 2.64 MB total
2 MB DRAM
512 kB FLASHROM
128 kB SRAM (battery backed)
A/D: 8 channels, 12 bit accuracy
Serial Ports: 2 UART 16C550 chips with RS-232 voltage level
Digital I/O: 24 channels (TTL)
Operating Temperature: -40 to 85 C

12. What Control and Data Handling Subsystems
Custom C&DH Board performs tasks required specifically by the Endmass
Analog MUX used to multiplex A/D channels – provides 23 total channels
Platform for Health Data Collection
Power and Data Connections for all Subsystems
2 4-Orbit Timers in Series
2 21-Day Timers in Parallel
GSE Data Connection
GPS Hard Reset Switch

13. What Power and Electrical Subsystems Power Distribution System
Solar Cells
Used to provide main power to the Endmass in day-side of the orbit (8 W) and to charge the batteries
Total power provided ~16 W
Batteries (Ni-Cd)
Used to provide main power to the Endmass in Eclipse (~8 W)

14. What Mag Tx PE CDH GPS Octagon Batt Female on inside, male on outside
from PAA
switches
Bulkhead Mounted
Bulkhead Mounted
Female on Icarus side, Male from GSE box
PAA (15pin)
4 wires
~30”
GSE (50pin)
PAAGSE
25 wires
~25.5”
8 wires
~20.5”
12 wires
~38”
Male connector on Mag .,
so cable has female connector
on this end.
PEGSE
CDHGSE
2+, 1- each string
negatives connected on each panel,
Tail,Top,PAA: 16.25”, Outboard 26.25”,
Nose: 22.5”, Bottom: 24.3”
Mag
Custom Transmitter
Connector (REM- no
toxic metals)
CDHBatt
PEPAA
7 wires, ~18”
2 wires ea
~7,17,17,32”
CDHMag
PESolar
25pin
9pin
GSE(J1)
Mag(J3)
4 wires
~6.5” Tx
Solar Cells(J1)
37pin
9pin
Tx(J4)
37pin PE
Therm(J5)
CDH
9pin
CDHTx
PAA GSE(J2)
CDHGPS
24 wires
GPS
PE(J2)
4.1,4.2
GPS(J7)
25pin
9pin,9pin
15pin
15pin
Battery(J3)
CDH(J4)
14 wires
~9.5”
Octagon(J6)
37pin
8 wire
~7”
PEBattery
33 wires, ~6”
16 wires
~12”, 15”
8 go to 9 pin
connector on PE,
8 go to floating
connector.
2 wire
Octagon
Keepalive battery
connected to CDH
board via jumpers
at GSE connector.
9pinmale
Batt
8 wires
PECDH2
8 wires
PECDH1
Male connector on GPS,
so cable has female connector
on this end.
2 Jumper wires go straight to Octagon board instead of through
C&DH board.
All wire is 24 guage, from the lab downstairs. (Flight qualified.)

15. What
Transmitter
Outputs assimilated data from the Octagon ~2.247 GHz
Ground stations at various locations around the world are set up to receive the data from this transmitter
The data is then relayed back to the Icarus team for analysis and conclusions

16. Schematic C&DH System Octagon 386 Magnetometer 3 Analog Values
Sampled 1/sec
Octagon 386
on/off
A/D
Dig I/O
Digital bit stream
Connection: TTL
Health System
MEM
MUX
Thermistors, Currents, Voltages
Sampled 1/min
data
Transmitter
Serial Port
Serial Port
Ground Support Equipment
on/off
GPS
Development and Testing
Connection: RS-232
Sampled 1/ 2 sec
Connection: RS-232

17. Tether attachment point
System Level Diagram
Power Path
Data Path
Solar Cells
Control 2
8 bits
PAA
Separation Switches
4 orbit
timer
21 day
timer
C&DH
Payload
Chip 25 MHz
Battery
Telemetry
GPS Receiver
Magnetometer
ROM 512 kB
Transmitter ( GHz)
RAM 2 MB
V = 5.0 V DC I = 185 mA
V = 5.0 V DC I = 11 mA
SRAM 128 kB
V = 5.0 V DC I = 650 mA
Power Distribution
V = 12.0 VDC I = 400 mA
GPS Almanac Data
Tether attachment point
tether
U of M GSE
ProSEDS

18. Mission Plan T=? Instrument Measurements T=+1 day ETD Deployment
T=~3 hours Tether Deployment
T=+60 min Power-up, Release
T=21+ days Reentry
T=0 March/May 2001 Delta-II Launch!

19. The Big Picture