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6th Responsive Space Conference RS6-2008-4006

Standardization Promotes Flexibility: A Review of CubeSats Success

Alexander Chin, Roland Coelho, Lori Brooks, Ryan Nugent Dr. Jorgi Puig-Suari Cal Poly San Luis Obispo

6th Responsive Space Conference April 28May 1, 2008Los Angeles, CA


Standardization Promotes Flexibility: A Review of CubeSats SuccessAlexander Chin Gradate Student (805)756-5087 Roland Coelho Graduate Student (805)756-5087 Lori Brooks Graduate Student (805)756-5087

Ryan Nugent Dr. Jordi Puig Suari Graduate Student Professor, Aerospace Engineering (805)756-5087 (805)756-5087 Aerospace Engineering Department California Polytechnic State University San Luis Obispo, CA 93407

ABSTRACT The initial creation of the P-POD was driven by the need for consistency and increased frequency in both pico-satellite development and access to space. The PPOD protects the launch vehicle and the primary payload as well as the CubeSats, and is compatible with many launch vehicles, making integration repeatable and cost-efficient. The P-POD can accommodate picosatellites that meet the 1kg mass and 10 centimeter cubic dimensional CubeSat standard. Mass producing a stock deployment device creates reliability in flight heritage and decreases design, manufacturing and testing costs. The P-POD provides a framework for developers to design around, and enforces adherence to the CubeSat specification. In turn, the P-POD is designed with the capability to integrate onto multiple launch vehicles. The advantages of this system are most evident in creating flexibility for CubeSat developers to launch on multiple rockets as secondary payloads. Since most satellite manufacturers must coordinate directly with the launch vehicle provider, secondary and tertiary payloads find it difficult to acquire launches. The P-POD can group multiple CubeSats to provide a competitive basis for launch as a viable secondary payload. This has allowed CubeSat developers to develop their system without a preset launch. A review of the P-POD flights over the past 5 years, and an outline of future launches consistently show the value of a standard and the benefits of flexibility. One of the main keys to the success of the CubeSat Program has been its strict adherence to the initial standard. Cal Poly, NASA Ames, and other organizations are looking to incorporate similar

standards to larger satellites in an effort to bring lowcost access to space for a wider range of spacecraft. These efforts will utilize the efficiency of the P-POD and will incorporate outside influence in developing future standards. CubeSats provide a unique flexibility in the aerospace industry opening up quicker and cheaper mission opportunities than ever before. In addition, the research at the CubeSat level offers a unique shift in design operations. This means that the structure and hardware are designed first, while the development of the payload comes second. In addition, developers can devote their focus on meeting the CubeSat standard and developing satellites and not on launch logistics and integration. Background The Poly Pico-satellite Orbital Deployer (P-POD) started as a collaboration between Cal Poly and Stanford University. This deployer would supplement the need for consistency in the design and launching of picosatellite class CubeSat satellite systems. The P-POD was developed with seven primary goals to meet1: 1) 2) 3) 4) 5) 6) 7) Protect the primary payload Protect the launch vehicle Protect the CubeSats Safely group multiple CubeSats for launch Eject CubeSats for safe deployment Increase Access to Space for CubeSats Provide standard interface to launch vehicle

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The design of the P-POD is relatively simple consisting of an aluminum box with a spring along with a door that is controlled by a release mechanism.

Figure 1: P-POD Mk II The P-POD is able to mount to multiple launch vehicles, allowing for a large level of versatility in search for launch opportunities. The CubeSat Standard The CubeSat specification states that a single CubeSat should not be larger than approximately a 10 cm cube, and have a total mass of no more than 1 kg. From these specifications, up to three CubeSats can be deployed from a single P-POD. In addition, the P-POD can launch double and triple CubeSats that occupy the same volume and weight as two and three CubeSats, respectively.

minimize tumble and spin rates at deployment from the P-POD The location of the access ports on the P-POD determines where CubeSats should have diagnostic ports and remove before flight (RBF) pins Rails on CubeSats must be smooth, flat, and hard anodized to prevent welding from the launch environment and minimize friction interference while deploying Thermal expansion of the CubeSats should be similar to that of the P-POD aluminum material (7075-T73) CubeSat design tolerances are based on PPOD tolerances and specifications

Figure 3: Schematic of the CubeSat Standard The P-POD as a Bridge from Developer to Launch Vehicle Decreases in Cost Launch costs are expensive, and as a secondary payload, CubeSats can find difficulty in paying for launches on their own. The P-POD can group multiple CubeSats together and provide feasible launch costs by combining them together as a larger payload inside of a P-POD. This also makes the CubeSats act as a more competitive payload with other larger secondary payload satellites. In addition, repetition in building multiple P-PODs decreases manufacturing and development costs with systems that are not mission specific.

Figure 2: MEROPE Satellite Developed by Montana State University4 The following are specifications to standardize CubeSats as a result of the P-POD interface1: The center of mass of a CubeSat must be within 2 cm of its geometric center to

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Flexibility in Access to Space Since CubeSat developers need only design to the CubeSat standard, their mission is independent of the launch vehicle itself, aside from a desired orbital altitude or trajectory. However, launch vehicles still maintain the final authority on which CubeSats they will allow for their launch. If a launch slips, the CubeSats and their mission can switch to another available rocket as a secondary payload. In addition, CubeSats need not be developed with a firm launch in place. Developers need only focus on finishing a quality product, and are not driven by launch dates. As the P-POD increases in compatibility with multiple launch vehicles, CubeSat developers can develop their satellites, and launch when they are ready.

Figure 4: Assembled P-PODs for Dnepr Launch Simplify interaction between multiple developers and launch provider It is not necessary for the launch provider to directly communicate with multiple CubeSat Developers on exact mounting setups and requirements. As long as developers adhere to the CubeSat P-POD standard, they need only communicate with Cal Poly, and Cal Poly will communicate directly with the launch providers. As long as the CubeSats do not interfere with launch operations, launch providers would only concern themselves with mounting the P-POD to their rocket.

Figure 6: P-POD Mounted on Minotaur LV Shift in Satellite Development Since CubeSat Developers must design to the CubeSat standard to fit inside the P-POD, the structure of the satellite is paramount and must be designed first to ensure its compatibility with the P-POD. Once these conditions are met, the actual mission of the CubeSat can be focused on. By designing to the standard, the CubeSat is given more flexibility on launch availability and access to space. Revisions of the P-POD Although CubeSat developers must strictly adhere to standards enforced by the P-POD, the P-POD has been flexible enough to consider design changes to better accommodate the needs of CubeSat Developers. The first P-POD, the Mk I, was designed to meet the basic requirements of protecting the CubeSats and launch vehicle. The Mk I used a burn wire deployment

Figure 5: Diagram P-POD Coordination5 Flexibility in Mounting CubeSats will not need to be compatible with different launch vehicles; rather they only need to be compatible with the P-POD. Since the P-POD attaches to the launch vehicle, the P-POD acts as an intermediary mounting device for CubeSats. The P-POD has shown flexibility in past missions through accommodating for different screw and mounting hole patterns for attachment to surfaces. The mounting holes can be modified to multiple rockets by using compatible helicoils for varying launch vehicle interfaces.

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system to open the door and release the satellites, which took approximately 30 seconds. The P-POD evolved into the Mk II to provide an instantaneous release after the launch vehicle deployment signal. To accomplish this, the Mk II was compatible with the Starsys Qwknut and NEA release mechanisms. Using either of these two space qualified release mechanisms reduced risk and increased the reliability of the P-POD. The latest generation of P-PODs are the Mk III. The Mk III P-POD offers increased access to CubeSats after integration, larger spring plungers for easier satellite integration, and bracket modifications to also accommodate release mechanisms developed by NEA. Therefore, P-PODS are responsive to the needs and requirements of not only the launch providers, but the CubeSat Developer community as well. Although the actual P-POD has changed, the CubeSat standard and launch vehicle bolt pattern remains the same and has not affected developers or