BillikenSat-IIBillikenSat-IIThe First Bio-Fuel Cell Test Platform in SpaceThe First Bio-Fuel Cell Test Platform in Space

Senior Team Members: Darren Pais, Paul Lemon, Nathaniel Clark and Sonia HernandezFaculty Advisors: Dr. Sanjay Jayaram, Dr. Krishnaswamy Ravindra and Dr. John George

4 communication windows per day (yellow) 4-7 minutes per communication window

C&DHC&DHPIC 18Micro-

controller

PowerPower

Battery Array

Battery Chargers

Solar Array

5V 7V3.3V

ADCSADCS

Thermal ControlThermal Control ExperimentExperiment

CommunicationsCommunications

Rate Gyro X

Rate Gyro Y

Rate Gyro Z

Heater

Thermal Sensor

Control Switch

Transceiver

Power Amp

Antenna

Control Switch

A/D Conv.

Data

Unregulated Bus

3V Bus

5V Bus

7V Bus

Interface diagram of electrical subsystems

Interface diagram for the entire satellite; this shows the interrelated nature of the BillikenSat-II subsystems

Communication Window

Nm

Smorbit

Geo-Magnetic Lines of Force

Nm

Smorbit

Passive Attitude Control using Permanent Magnets and Hysteresis Dampers

Dynamic Modeling of Permanent Magnet Stabilization, Both Undamped (blue) and Damped with Hysteresis

Material (red)

Enzy

mes

V

Anode Cathode

H+

Nafion 112

H+

O2

H2O

e-e-

Orbital Parameters DNEPR 07

Type of Orbit Sun synchronous

Inclination 98 deg

Eccentricity 0.009

Altitude Perigee 660 km

Altitude Apogee 772 km

Period 90 min

Nylon & Nichrome for deployment

Spiral etching

Silver epoxy for contact

Antenna: Nitinolshape memory alloy

Antenna Deployment

Nitinol shape memory alloy material is used in our antenna design. The shape memory effect means that the antenna can be restrained within the spiral etching pictured above until the satellite is deployed, and it will return to the straight perpendicular orientation once released. The antenna is restrained in the spiral by nylon line which is in contact with a nichrome wire. To deploy the antenna, a current is passed through the nichrome wire, which melts through the nylon line, thereby allowing the antenna to achive its straight orientation.

Anode

Membrane Electrode Assembly

Cathode

4 cm

Bio-Fuel Cell

The payload of BillikenSat-II is an exciting new experiment developed by the Minteer Lab in the Department of Chemistry at SLU. The Minteer Lab works extensively on fuel cells that use biological fuels. The process by which electricity is produced is modeled in the diagram on the far left above. This energy alternative is especially suited for space applications due to its ability to adapt to use various biological fuels, such as dissolved food, orange juice or even astronaut waste. One of the difficulties with testing this technology in space is the size. The launch program chosen for this satellite is the Cubesat program, which limits the satellite to a 10 cm on edge cube with a mass of 1 kg. The center two pictures illustrate how the lab version was scaled down to meet the space and mass requirements. The diagram on the right here shows a more detailed computer model of the fuel cell used for our payload.

Structural Temperature Range: -20oC to 35oC

temperature sensor

If T < 10oC

If T > 30oC

take no action

turn on heater

turn off heater

true

false

false

true

Heating/Cooling Cycle:

Heater on ~ 14 minutes; Heater off ~ 18 hours

1

1

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Multi-Layer Insulation (MLI)

eq

q

Mylar Film

Dacron Web

Structures Engineering

Besides the size and mass requirements, the Cubesat standard requires that each satellite undergo specific tests, mainly thermal-vaccum and vibrational testing. The structure of BillikenSat-II was engineered with these requirements in mind. Finite Element Analysis, along with analytic calculations, was used to ensure the deflections and stress caused by vibrations and gravitational loading during launch do not dammage the satellite. The structure is designed to be simple and convenient to integrate, with common fastners and interchangeable slots.

Attitude Control

Since the experiment aboard BillikenSat-II does not require any accurate pointing, the attitude control system is necessary only for communication purposes (the antenna must be quasi-parallel with the Earth’s surface). In order to limit the physical size and computational load, a completely passive stabilization method was chosen involving permanent magnets and hysteresis dampers. The figures below illustrate this method and demonstate the dynamic modeling.

Orbital Analysis

The Cubesat program uses a DNEPR launch vehicle which deploys satellites into near polar-circular orbit as seen below. Using the complete set of orbital elements, an STK © simulation was performed. A link analysis done using STK gives the communication window shown here over a 24-hour period, centered at the ground station in Oliver Hall at SLU.

Thermal Engineering

Our biological payload has a strict temperature survivable range of 4oC to 40oC. To maintain this temperature range, a combination of passive and active thermal control was used. The PEEK payload vessel, besides having good strength characteristics, also has extremely low thermal conductivity. Consequentially, the heat transfer from the main structure to the payload is negligible, which means the payload temperature is independent of sunlight or eclipse conditions. The passive control used is the Multi-Layer Insulation shown to the right. The active thermal control system uses a Thermofoil © resistance heater pictured below (43mm dia.) that is controlled via the logic loop shown. The bio-fuel cell will be maintained in a safe range of 10oC to 30oC.

Systems Engineering

One of the most challenging and rewarding facets of the BillikenSat-II project is its interdisciplinary nature. This project incorportates Electrical and Computer Engineering students and a Chemistry graduate student, with the Aerospace Engineering students. Integrating electrical and physical requirements is a considerable task, especially when they are driven, as this project is, by a biological payload at its core. Shown below are systems interface diagrams that illustrate the interdesciplinary nature of this project.

Air Tight Fill Port

Wire Interface

Pressurized Payload Vessel

Since the payload is a biological fuel cell, it is necessary to maintain the payload at near Earth-ambient conditions. The fuel cell is air-breathing, so it must be constrained within an oxygen tank. Besides the presence of oxygen, the fuel cell must also be kept at a pressure over 1 atm. A cylindrical design was chosen for the tank (red above) because it is nearly ideal in shape for a pressure vessel (a sphere being ideal, but not feasible in this size-limited environment). The vessel is made of PEEK polymer, which has a very high tensile strength, and incorparates a wire-interface to draw information from the cell experiment.

Side Panel with Solar Cells

Antenna

3-view & isometric

Assembled Hardware

Main Structure CD&H

Power

Comm

Battery Box

Payload

Thermocouple

Active Thermal Control

Antenna Housing

Antennas

Kill Switch

Remove before flight pin

Solar Panels

Copper Coated PCB board

Magnets

Hysteresis Rods

Structures

ADCS

Power

Comm.

C&DH

Thermal

Legend