I. Literature Review




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Organization


The organization and scheduling of this project is to fit within a two semester time frame. All work for the project will be shared equally, dependent upon each team members' strengths. The planned completion of this project is early April 2011 with allowances for extensions. The bulk of the scheduling is comprised of design and manufacturing. Procurement of materials should be minimal due to the simplicity in the design approach. The work breakdown structure of the project currently consists of ten tasks:

  1. Problem Definition – Define the task to be accomplished including constraints such as final product volume and mass, and project scope.

  2. Budget/Cost Analysis – Determine an estimate for the amount of capital necessary to develop and test the prototype.

  3. Finalization of Approach – Based on the background research and project scope, decide on the method of deorbiting, be it an inflatable or rigid structure.

  4. Software Development – Write software and code that will allow the mechanism to perform its intended function.

  5. Materials Sourcing – Obtain all of the materials necessary to construct and demonstrate the prototype deorbiting system.

  6. BUS Interfacing – Integrate the prototype hardware and software with the command and control computer of the CubeSat.

  7. Structural Design/Packaging – Finalize and construct the housing for the deorbiting device.

  8. Integration – Integrate the hardware, software, and controllers into the CubeSat payload.

  9. Testing

  10. Report and Summary

Care has been taken to allow for leeway in the scheduling, so that any difficulties encountered during a particular phase in the work breakdown structure will not cause the project to exceed the firm deadline of the end of the Spring 2011 semester. A Gantt chart has been developed of the project timeline, and is attached in the Secondary Material section of the Appendix.

Cost Consideration


The costing of this project is supplemental currently. The primary purchasable components are 606-T6 aluminum, Kapton®, adhesive, inflation gas, and the CubeSat development kit. The Kapton® film has been acquired by donation, and is valued at approximately $200/lb. This saves a considerable cost in the overall project. An additional donation of the CubeSat kit mitigates that cost, which is currently $5,000.

Of the many available adhesives Elastosil S36® (which is similar to an RTV silicone) was chosen with regards to its low out-gassing and previous use in spaceflight qualified applications. Elastosil® is produced by Wacker Chemie AG (Wacker Chemie AG) and is available from various suppliers within the U.S. for around $15 per tube.

As mentioned previously the use of COTs technology allows for the cost of CubeSat development to be kept to a minimum. This is especially true of the electronics. Controllers similar to those utilized in recreational robotics can be integrated into the CubeSat, providing a cost effective solution for running software. Controllers are available from many sources with single unit costs averaging around $200 (RobotShop).

6061-T6 aluminum can be purchased in a variety of shapes and sizes. Price varies depending on the amount of shaping and forming required (cold/hot working) and surface finish. Aluminum naturally forms an oxide coating when exposed to the Earth environment, so no further surfacing is required to prevent corrosion or per NASA regulations. Raw material is available from industrial suppliers at a cost of approximately $0.10/cm3 (McMaster Carr). As the volume of the deorbiting device is restricted to a maximum of 150 cm3 (Lokcu), the total raw material cost for the aluminum in a single device is capped at $15.

Labor is estimated to be the largest contribution to cost during prototype development. Such tasks as milling, machining, or circuit board printing/construction will incur labor costs. Labor rates vary depending upon the location and task to be performed. Additional costs include miscellaneous wiring and electronics, as well as assembly hardware and tools. These costs should be around $120. The total cost for a single deorbiting unit, not including the cost of the Kapton® or labor, is estimated to be $193. This information can be seen in Figure 14 below.

The costs incurred are itemized in Figure 13. These are the costs for prototyping the design. At this point the development has been very reasonable. The ability to reuse parts or to acquire items free of charge has aided our budget. It should be noted however that the price would increase if these objects were not acquired for free.

Prototype




Material

Cost

2 Mil Mylar

$33

Contact Cement

$10

Gas Cylinder (from lab)

$0

Lab air

$0

Aluminum (from stock)

$0

Valve (Clippard)

$48

Circuit board

$2

Misc.

$15

Net cost:

$108

Figure : Prototype Budget



Space-Qualified Design







Material

Cost

Mass (g)

Upilex-S polyimide film (50µm)

$75

126

Elastosil S

$15

0.004

Aluminum 6061-T6

$15

2.13

SUVA-236fa refrigerant

unknown

1.77

Aluminum 6061-T6 (from stock)

$0

2.13

Upilex-S polyimide film (50µm)

included above

0.74

Dyneema

$3

0.075

Clippard

≥ $70

Around 11 g

Misc.

$15

 




Cost

Net mass (g)




$193

143.849

Figure : Space Qualified Budget

Summary


The level of development to this point has been successful. The prototype is in the process of being built and tested. The project is running close to being on schedule, perhaps off by a week. This can be made up in other areas of the project.

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




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

Bradford Engineering. "Sold Propellant Cool Gas Generator." 2006. .

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

Clippard Instrument Laboratory, Inc. www.Clippard.com. 2011.

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." .

IADC. "Space Debris Mitigation Guidelines." Standard. 2007.

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

McMaster Carr. 27 November 2010 .

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

Pumpkin, Inc. CubeSat Kit. 2008. .

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

RobotShop. 30 November 2010 .

Wacker Chemie AG. 1 December 2010 .





II. Secondary Material




Project Gantt Chart:




1   2   3   4   5

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