I. Literature Review




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Future Recommendations and Research


The testing and research conducted thus far has yielded a great deal of knowledge about the actual construction of a working deorbit device. The next step is to complete the preparation necessary to test the deployment of the balloon in a low pressure environment. The low pressure environment will help to verify the design chosen thus far. The folding technique and the membrane rupture are key items which will need to be addressed in the low pressure environment.

Another area which will need to be explored during further testing and research is the scaling down of the valve assembly. There have been challenges thus far acquiring the correct specifications required for the current valve operating conditions. In future designs, the valve assembly may be substituted for an alternate inflation method. This area of deployment will be researched further, but is beyond the scope of this report.

A serious area of refinement on this project in the future will be in regards to custom inflatable membranes. The ability to manufacture a custom membrane to exacting specifications is critical for a successful deployment. The research conducted during this project has found that the use of adhesive when attaching layers of Mylar or Kapton is ineffective. The correct manufacturing method will be some form of welding or melting of the two mating surfaces. This will require specialized equipment and further research to be conducted properly.

The rupturing membrane is also an area which will need further refinement as the project matures. The correct material will need to be tested in a laboratory environment to test its feasibility. Also, strict quality control procedures will need to be in place, similar to the custom inflatable. The quality control for the rupturable membrane is critical due to the cuts and scribe lines put in place for the correct rupturing pattern.

Summary


The amount of knowledge and experience gather during this project has been staggering. The actual amount of engineering in various disciplines has been quite extensive. This project has taken the necessary steps to begin down a path to build a full scale space-ready version of the design. Engineering changes will need to be made along the way. However, this project has introduced and researched many of the areas that will be necessary for a successful mission.

Controlled deorbiting of retired satellites is of major importance in the coming years. As space access becomes easier, a reliable means of deorbiting is essential. This project provides a test-bed for such a device. The pillow design adopted here provides an easily assembled and inflatable structure to increase the surface area of the CubeSat. The compactness, reliability, and low cost of this device lends itself greatly to CubeSat integration







Appendix

I. Works Cited





1. California Polytechnic, State University. CubeSat Design Specification Rev.12.

2. Pumpkin, Inc. CubeSat Kit. [Online] 2008. http://www.cubesatkit.com/.

3. R. Janovsky, M. Kassebom, H. Lubberstedt, O. Romberg. END-OF-LIFE DE-ORBITING Strategies for Satellites. Bremen : OHB System AG, 2002.

4. Space Debris Mitigation Guidelines of the Committee on the Peaceful Uses of Outer Space. Office for Outer Space Affairs. Vienna : United Nations, 2010.

5. IADC. Space Debris Mitigation Guidelines. s.l. : IADC, 2007. Standard.

6. Development of a Generic Inflatable De-Orbit Device for CubeSats. D.C. Maessen, E.D. van Breukelen, B.T.C. Zandbergen, O.K. Bergsma.

7. Design Considerations for CubeSat Inflatable Deorbit Devices in Low Earth Orbit. Lokcu, Eser. 2010, Old Dominion University.

8. DuPont. Summary of Properties for Kapton Polymide Films. [Online] http://www2.dupont.com/Kapton/en_US/assets/downloads/pdf/summaryofprop.pdf.

9. Bradford Engineering. Sold Propellant Cool Gas Generator. [Online] 2006. http://www.bradford-space.com/pdf/be_datasheet_spcgg_sep2006.pdf.

10. Clippard Instrument Laboratory, Inc. www.Clippard.com. [Online] 2011.

11. Bate, Roger R, Mueller, Donald D and White, Jerry E. Fundamentals of Astrodynamics. New York : Dover Publications, Inc., 1971.

12. Chattopadhyay, Somnath. Pressure Vessels: Design and Practice. Boca Raton : CRC, 2005.

13. Wacker Chemie AG. [Online] [Cited: December 1, 2010.] http://www.wacker.com/cms/en/products-markets/trademarks/elastosil/elastosil.jsp.

14. RobotShop. [Online] [Cited: November 30, 2010.] http://www.robotshop.com/.

15. McMaster Carr. [Online] [Cited: November 27, 2010.] http://www.mcmaster.com/#aluminum/=a2cdo0.




II. Secondary Material



Project Gantt Chart:



III. Microcontroller Source Code


/*

* LEDbitWise.c

*

* Created: 4/18/2011 9:04:23 PM

* Author: Jake Tynis

*/


#include

#include

#include

#include


//Define the Valve Port

#define VALVE_PORT PORTB

#define VALVE_BIT PB3

#define VALVE_DDR DDRB

//Define the Buzzer Port

#define BUZZER_PORT PORTD

#define BUZZER_BIT PD7

#define BUZZER_DDR DDRD

#define DEBOUNCE_TIME 25

#define LOCK_INPUT_TIME 250


//Define the IR Port

#define TSOPPORT PORTC

#define TSOPDDR DDRC

#define TSOPPIN PINC

#define RC5BitHigh() (bit_is_set(TSOPPIN,2))

#define RC5BitLow() (bit_is_clear(TSOPPIN,2))

#define WAITFORTIMER() { while ( timerflag == 0); timerflag = 0; }

#define TIMER_0_CNT 0xCA // 111us with CLK/8 prescale

#define RC5BITREF1 6

#define RC5BITREF2 11

#define RC5BITREF3 14

#define TMC8_STOP 0

#define TMC8_CK8 _BV(CS01)

#define Timer0On() TCCR0 |= _BV(CS00);

#define Timer1On() TCCR1B |= _BV(CS10)

#define Timer1Off() TCCR1B &= ~(_BV(CS10)); PORTD &= ~_BV(5)


void init_io();

void toggle_valve();

void toggle_buzzer();

static volatile uint8_t timerflag;

unsigned int rc5decode( void );


int main(void)

{

uint16_t IRdata;

unsigned int rc5data;

uint8_t i;

TCCR1A = _BV(COM1A0); // Toggle timer1 output on match

TCCR1B = _BV(WGM12); // Clear timer on compare mode

init_io();

while(1)

{

while (RC5BitHigh());

rc5data=rc5decode();

IRdata=(rc5data & 0x003f);

if(IRdata<10)

{

}

else if(IRdata==12)

{

toggle_valve();

toggle_buzzer();


}

else

{

}


}

return 0;

}


void

init_io()

{

VALVE_DDR= _BV (VALVE_BIT);

VALVE_PORT |= _BV (VALVE_BIT);

}


void

toggle_valve()

{

VALVE_PORT ^= _BV(VALVE_BIT);


}


void

toggle_buzzer()

{

BUZZER_PORT ^= 0xFF;

_delay_ms(1000);

BUZZER_PORT ^= 0xFF;

}


unsigned int rc5decode( void )

{

unsigned int rc5data;

unsigned char timer;

int i;

sei();

// init timer/Counter0

TCCR0 = TMC8_CK8; // use CLK/8 prescale

TCNT0 = TIMER_0_CNT; // set timer T/16 = 111us

TIMSK = _BV(TOIE0); // enable TCNT0 overflow interrupt

// measure startbit

timerflag = 0; timer = 0;

while ( RC5BitLow() && (timer < RC5BITREF2) ) {

WAITFORTIMER();

timer++;

}

if ( (timer > RC5BITREF1) && (timer <= RC5BITREF2) ) {

// startbit ok, decode

// wait T/4: synchronize in the middle of first half of second bit

while ( timer < RC5BITREF3 ) {

WAITFORTIMER();

timer++;

}

// read the remaining bits

rc5data = 1;

for (i=0; i<13; i++) {

rc5data <<= 1;

if ( RC5BitHigh() ) {

rc5data |= 0x0001;

// wait max T/2 for H->L transition (middle of next bit)

timer = 0;

while ( RC5BitHigh() && (timer < 16) ) {

WAITFORTIMER();

timer++;

}

}else{

rc5data &= ~0x00001;

// wait max T/2 for L->H transition (middle of next bit)

timer = 0;

while ( RC5BitLow() && (timer < 16) ) {

WAITFORTIMER();

timer++;

}

}


if ( timer == 16 ) {

rc5data = 0x0000; // error, next bit not found

break;

}

// wait 3/4 T: await next bit

for ( timer=0; timer < 12 ; timer++) WAITFORTIMER();

}


}else {

rc5data = 0x0000; // error, invalid RC-5 code

}

TCCR0 = TMC8_STOP; // stop timer0


//sbi(TIMSK, OCIE1A); // Enable the compare mode Once Again

return (rc5data);

}

SIGNAL(SIG_OVERFLOW0) //This interrupt is used by 2 functions wiz TV remote and obstacle sensor

{

timerflag = 1; // set global variable

TCNT0 = TIMER_0_CNT; // reset counter to get this interrupt again }

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