2010 Olin Student Projects

Keith Gendreau

Keith.c.gendreau@nasa.gov

301-286-6188

Fred Huegel

frederick.g.huegel@nasa.gov

301-286-2285

Kurt Rush

Kurt.d.rush@nasa.gov

301-286-1196

Bob Baker

Robert.g.baker@nasa.gov

301.286.9882

2009 Student Projects with contacts

• XACT Sounding Rocket Low Voltage Power Supply Point Design– Keith Gendreau, Kurt Rush, Fred Huegel, Bob

Baker

• Modulated X-ray Source Controller– Keith Gendreau

Project #1, XACT Low Voltage Power Supply Point Design

• We are in the initial phases of designing and building a suborbital rocket payload to do astrophysics

• The detectors and command & data handling units need regulated low voltage power derived from “28 Volts” from Rocket battery

• Do a point design of a Low Voltage Power Supply (LVPS) and build a prototype– Take Electrical and mechanical requirements of LVPS– Include basic housekeeping functions– Build a command tester

XACT Payload and Rocket

X-ray Concentrators & Star Tracker

Optical Bench

X-ray Polarimeters, Electronics, & MXS

Overall Payload Length: 3.26 mPayload Diameter: 52 cm*

Payload Mass: 80.2 kg (include ST)A 1st approximation of complete XACT rocket

Black Brant VC

Terrier Mk70

Aft Cone & Door

Nose Cone & Recovery System

Telemetry and ACSSystems

Very Basic XACT Block Diagram

Rocket Avionics System

Unregulated 28 V powerUnregulated 28 V power

Telemetry InterfaceTelemetry Interface

XACT Main Electronics Node (XMEN)

SRIB

LVPS

Regulated power

HK

PEB 1

PEB 2

HVPS

Regulated power

PEB 3

IN FLUX..Will define, but may be a bit bigger

Other details• We will soon specify connectors for the power

output and HK address and data• HK should include actual voltages and currents

and some temperatures of items which may get warm

• Look in digikey and elsewhere for cheap, but robust converters and parts..– Some specify shock and vibration ratings

• Can you make a USB based card that would allow us to query for HK?

Olin student Project #2: Modulated X-ray Source

Controller• Our new modulated X-ray source uses UV light to

generate photoelectrons which are accelerated into high voltage targets to make X-rays

• We like to have absolute control of the X-ray flux, which is driven by absolute control of the UV light (from LEDs)

• Olin student project: build an X-ray source electronics box which– provides HV– Drives UV LED with arbitrary flux output– Measures currents, temperatures– Is USB controlled with PC or mac software

Vacuum Flange

Electron Target

Photocathode

LED: Modulate This tomodulate the x-rays.

OpticalPhotons

X-ray Photons

Photoelectrons

10 keV or more

•Characteristics:

• Rugged- no moving parts or fragile filaments- perfect for space flight.

• Modulates x-rays at same rate that one can modulate an LED

• Major NASA Uses:

•Timing Calibration

•A “flagged” in-flight Gain Calibration Source: Have calibration photons only when you want them and increase your sensitivity by reducing the background associated with the calibration photons

The World’s First Fully Controllable Modulated X-ray Source

This has evolved to include an electron multiplier

LED

HV for Target(~5-10 kV)

HV for Electron Multiplier(~2-3 kV

1st Magnum Multiplier MXS

Multiplier HV

Electron Target HV

Be Window

Be Window

AMPTEK Detector

Electron Target HV

Multiplier HV

Output of AMPTEK Detector

Pulses Modulating X-ray Output

Some 1st Data

Block Diagram

Computer

“Smarts”

US

B

LEDLED Driver

HV Multiplier (DC/DC Converter)

HV Target (DC/DC Converter)

Source (provided by GSFC

Commands from computer• HV target voltage (0-10 kV)

– Use EMCO Q series dc/dc converter with a dac and transistor follower

• HV multiplier voltage (0-3 kV)– Use EMCO Q series dc/dc converter with a dac and transistor

follower

• Arbitrary LED flux as a function of time– Asci file?

• Pulsed LED flux– Frequency, duty cycle or width, amplitude

• Query for housekeeping

House Keeping Items

• LED current (average, max)

• LED temperature (necessary?)

• HV current (or atleast current and voltage into various DC/DC converters)

“i-Heliograph”

• Can we make a low power data transmitter to send “lots” of data from the moon to the earth using a 19th century idea enhanced with 21st century technology?

• How does such a system compare to laser communication?

Replace this guy with a high speed optical modulator and an ethernet port.

Replace this guy with a avalanche photodiode and an ethernet port..

Replacing the guy wiggling the mirror

• Voltage Controlled LCD displays (KHz Speeds?)

• Acoustic Optical Modulators (speeds up to 100 MHz)

Replacing the guy using his eye to see the signal on the

receive end• Avalanche Photo diodes

There should be a power savings compared to Laser

Comm• Lasers are ~10% efficient on producing

optical output from electricity it gathers from ~25% efficient solar cells.– Total efficiency from sun = 0.25 * 0.1 =

2.5%

• Mirrors are ~90% reflective

Other factors in comparison

• Mass to moon– Do solar cells and power system with

Laser weigh more than a mirror and heliostat?

• Reliability– Solar panels, motors, AOMs…– Is dust an issue?

2009 Olin Job

• Build a Heliostat to capture the sun• Pipe the light from the Heliostat through

either an accoustic optical modulator or a LCD retarder

• Build a simple pulse frequency modulator to drive the AOM or LCD retarder

• Build a demodulator to read the output of an APD

• Predict performance and compare to Laser Comm.

GSFC will provide

• A telescope base to make a heliostat• An AOM to modulate light• A Circuit design to produce a FM Pulse

train• A Telescope for the receive end• An APD (maybe dual use the one for

the MCA project)• The demodulator design.