Joshua Laub Jake Tynis Lindsey Andrews Small, lightweight satellites Developed by California Polytechnic State University and Stanford University Relatively low cost Short development time Auxiliary payloads on larger missions Size = 10 cm cube (1 U up to 3U) Total Mass < 1 kg Orbital altitudes as great as 900 km (ISS is about 350 km) Definition: Man-made objects in orbit Around 19,000 objects > than 10 cm DIA Velocities on the order of 7.4 km/s NASA/IADC Guideline: Man-made orbital debris must have lifetime of 25 years or less. Challenger (Fleck of Paint) Endeavor (unknown debris) Increasing volume of CubeSat missions contributes to orbital debris Due to their small size, mass, and frontal area CubeSats have orbital lifetimes on the order of 500 years at typical deployment altitudes ( 1000 yrs @ 900 km) Orbital decay is controlled by atmospheric density using a characteristic ballistic coefficient BC = m/Cd*A Develop a prototype CubeSat deorbiting system Basis: Even at 900 km altitude, atmospheric density is sufficient to create a small amount of aerodynamic drag (V = 7.4 km/s). Increasing the cross sectional area will increase the drag, decrease ballistic coefficient, and deorbit the CubeSat faster. Possible Solutions: Inflatable device 2. Deployable frontal area device 1. Modular inflatable structure to increase drag Considerations: Shape Folding/Packaging Inflation system Material Structural Spherical: Overlap panels to create spherical shape High reliability on the adhesion of panels Pillow: Bond two sheets at edges Less dependence on adhesion (less room for error) Gas cylinder initiated by ground signal or on-board timing circuit Must consider added weight and volume for power source Must be cautious of over-inflation or gas leaks Gas: Liquid that vaporizes upon release into lowpressure inflatable structure Bradford Engineering Conditions: Durability and low density Polyethylene terphthalate (Mylar) Polyimides Resistant to punctures, low cost but vulnerable to radiation over long periods of time Good mechanical properties External chemical coating necessary to prevent atomic oxygen degradation Kapton Thicknesses of about 25 – 50 microns Coatings of about 0.1 micron Insert a conductive strip inside the inflatable structure to allow a ring of electrical current to flow, which would interact with the Earth’s magnetic field F = I*L x B Figure 1 Figure 2 Figure 3 Main challenges: Orienting the CubeSat Controlling the current (timing) Ensuring that the dissipated heat does not degrade the adhesive New folding characteristics Adequate battery life to produce current Increase surface area for drag Extending panels that can swing out to increase CubeSat surface area Panels could be used for solar power if desired Main challenge: Weight constraints Benefits: No concerns about leaks or folding patterns Challenges: Additional mechanisms and moving parts, requiring power and volume (pointing at the sun may not produce drag cross section) US Air Force Plug and Play prototype system Develop interfaces (assuming onboard avionics) to determine CubeSat orientation Develop software to activate drag device deployment via transmitted radio command Demonstrate deployment Estimated Finish Date: March 23rd (Allows time for unexpected delays) ITEM 6061 T6 Al Kapton© /Mylar Elastosil © S36 adhesive Suva 236fa gas Misc. Electronics Testing/Labor COST ~$0.10 /cm3 $200 /lb $18.00 /tube Pending Supplier ~$200+ /module Location/trade specific Goal: Create de-orbiting device for CubeSat Inflation structure General increased surface area Challenges: Weight Packaging Folding (if inflation device selected) Signaling (Ground signal or on-board circuitry) Bradford Engineering. "Sold Propellant Cool Gas Generator." 2006. <http://www.bradford-space.com/pdf/be_datasheet_spcgg_sep2006.pdf>. California Polytechnic, State University. "CubeSat Design Specification Rev.12." D.C. Maessen, E.D. van Breukelen, B.T.C. Zandbergen, O.K. Bergsma. "Development of a Generic Inflatable De-Orbit Device for CubeSats." (n.d.). DuPont. "Summary of Properties for Kapton Polymide Films." <http://www2.dupont.com/Kapton/en_US/assets/downloads/pdf/summaryofpr op.pdf>. Lokcu, Eser. "Design Considerations for CubeSat Inflatable Deorbit Devices in Low Earth Orbit." Old Dominion University (2010). NASA. NASA Orbital Debris Program Office. 2009. <http://orbitaldebris.jsc.nasa.gov/>. —. NASA's Cubesat Launch Initiative. 2010. <http://www.nasa.gov/directorates/somd/home/CubeSats_initiative.html>. Office for Outer Space Affairs. "Space Debris Mitigation Guidelines of the Committee on the Peaceful Uses of Outer Space." Vienna: United Nations, 2010. R. Janovsky, M. Kassebom, H. Lubberstedt, O. Romberg. END-OF-LIFE DEORBITING Strategies for Satellites. Bremen: OHB System AG, 2002. Questions?