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6th Responsive Space Conference April 28–May 1, 2008

Los Angeles, CA

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

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Standardization Promotes Flexibility: A Review of CubeSats’ Success

Alexander Chin Roland Coelho Lori Brooks

Gradate Student Graduate Student Graduate Student [email protected] [email protected] [email protected] (805)756-5087 (805)756-5087 (805)756-5087

Ryan Nugent Dr. Jordi Puig Suari Graduate Student Professor, Aerospace Engineering [email protected] [email protected]

(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 P-POD 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 pico-satellites 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 low-cost 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) Protect the primary payload 2) Protect the launch vehicle 3) Protect the CubeSats 4) Safely group multiple CubeSats for launch 5) Eject CubeSats for safe deployment 6) Increase Access to Space for CubeSats 7) Provide standard interface to launch vehicle

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1AIAA/6th Responsive Space Conference 2008

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.

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

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 P-POD 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.

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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 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.

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 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

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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 the launch vehicles. This was of fundamental importance for the P-POD itself to adhere to maintaining the standards to ensure continued compatibility for future payloads and launches.

Figure 7: P-POD Mark III

Application of This Philosophy in Past Missions

The concept of standardizing CubeSats to allow for flexibility in finding launches and developing satellites with the expectation and ability of launching on multiple launch vehicles is further discussed in the following launches coordinated with the inclusion of P-PODS as a secondary payload.

Rockot Launch, June 2003

The Rockot launch vehicle launched a total of two P-PODS with four different CubeSats inside. The P-PODs were mounted to the outer edges of the payload support structure as shown in figure 8. These P-PODs were the original Mk. I design with a Planetary Systems Corporation Line Cutter Assembly, which burned through a Vectran line 30 seconds after receiving the signal from the launch vehicle. The power needed to burn through the Vectran line was all contained within the P-POD Mk. I system and did not require any resources from the launch vehicle, except for the standard launch vehicle deployment signal. This was the first ever launch of CubeSats, and it was determined that all CubeSats were deployed successfully from NORAD object tracking data. To this day, QuakeSat-1, a triple CubeSat from this launch, has been one of the most successful CubeSat missions providing data for early detection of earthquakes.

Figure 8: P-PODs Mounted on Rockot LV

Dnepr Launch- Belka, July 2006

The Dnepr launch during the summer of 2006 consisted of 5 P-PODS with 14 CubeSats from 10 universities and one private company. The P-PODS were mounted on the Space Head Module (SHM) on the lower shelf, which provides support for the payload as shown in figure 9. Unfortunately, the launch vehicle experienced an anomaly during the first stage engine firing and the onboard avionics terminated the flight shortly thereafter. Even though these 14 CubeSats never made it into orbit, valuable integration and procedural experience was gained.

One valuable benefit of the P-POD and the CubeSat standard was realized during the months leading up to integration for this Dnepr launch. Originally the Dnepr launch with the Belka primary payload was the second of the two Dnepr launches. The first Dnepr launch with

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the EgyptSat primary payload was scheduled to launch before Belka, but multiple launch delays pushed it farther out. Since the first set of CubeSat payloads were now waiting over 2 years for a flight, Cal Poly requested to swap the payload manifest between the EgyptSat and Belka launches. Initially the launch vehicle provider was reluctant to pursue this request because of payload to launch vehicle interfaces and administrative filings with the Russian Space Agency. However, about three months prior to shipping hardware to the launch site, the request for the CubeSat manifest swap was granted. Typically this can not be accomplished for a traditional spacecraft due to varying mass, volume, and interface requirements. This was a large milestone for the P-POD and the CubeSat standard as it proved the transparency of the CubeSat payloads to the launch vehicle and the P-POD’s standard interface to the launch vehicle.2

Figure 9: P-PODS Mounted on Dnepr LV

Minotaur Launch: December 2006

NASA Ames developed GeneSat-1, a triple CubeSat with a biological experiment testing the growth of e coli in space. This was the first US launch of a CubeSat onboard a Minotaur I launch vehicle from Wallops Island, Virginia. GeneSat-1 was 100% successful and demonstrated to the satellite community that real science can be achieved on such a small platform. The P-POD was mounted on the fourth stage motor casing of the rocket as shown in figure 10.

To minimize risk to the primary payload, TacSat2, the P-POD was mounted below the payload interface plane and deploying in the aft direction of the launch vehicle. With the temperature sensitive e coli onboard, initially there were concerns of back radiation from the fourth stage firing, but it was later proven to be a nonissue. The P-POD’s form factor created launch opportunities

in locations that would be impossible for other spacecraft. In this location, the P-POD is only inches away from the fairing’s dynamic envelope, creating a unique launch capability only for CubeSats.

Figure 10: P-POD Mounted on Minotaur LV

Dnepr Launch-EgyptSat, April 2007

The second Dnepr launch consisted of a total of three P-PODs with 7 different CubeSat payloads. This time the P-PODs were mounted to a bracket on the upper shelf between the two primary payload satellites, EgyptSat and SaudiSat, as shown in figures 11 and 12. This was an unusual mounting location, and for typical spacecrafts, a near impossibility to fit within this volume. The P-PODs were integrated without any problems and the two primary spacecraft were comfortable with having these picosatellites rest only inches away. This unique mounting location was made possible by the robust design of the P-POD to withstand the harshest launch environments and prevent premature deployment of the CubeSats.

With the failure of the first Dnepr launch, it was critical to the CubeSat Program that these picosatellites reach orbit. It was unfortunate for the 14 CubeSat payloads that were originally manifested for this launch. However, it was in the best interest of all the parties to pursue the manifest swap between the two Dnepr launches because of the unknown EgyptSat launch date. This swap proved the flexibility of the P-POD’s standard interface and the CubeSat’s transparency to the launch vehicle. On April 17th 2007, it was confirmed that all CubeSats were ejected and contacted with successfully, providing Cal Poly with its first two satellites in space.

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Figure 11: P-PODs Mounted on the Dnepr LV

Figure 12: P-POD Mounted on Dnepr LV

Other CubeSat Launches

Other CubeSats have launched that used similar concepts as the P-POD. In October 2005, the SSETI Express launched CubeSat XI-V, N-Cube-2, and UWE-1 on board the T-POD (Tokyo Picosatellite Orbital Deployer) developed by Tokyo Institute of Technology.

In February of 2006, CUTE 1.7 with the payload of Avalanche Photo Diode Sensor module was successfully launched on board the T-POD.

Future Missions

There are five upcoming launches with CubeSats manifested as payloads. The first is a SpaceX Falcon 1 launch out of the Kwajalein Atoll in the beginning of June 2008. There will be two P-PODs onboard, with a triple CubeSat (PreSat) from NASA Ames and a triple CubeSat (NanoSail-D) from NASA Marshall.

The P-PODs will me mounted to the Rideshare Adaptor (RSA) developed by Space Access Technologies (SAT)

and is funded by Astronautic Technology (M) Sdn Bhd (ATSB). A conceptual drawing of the ride share adapter is shown in figure 13.

Figure 13: Rideshare Adapter Illustration6

The Rideshare Adapter, gives the opportunity for up to 6 P-PODs to be mounted on the exterior of the adapter and the upcoming SpaceX Falcon 1 flight will demonstrate its capability. This adapter is also compatible with multiple rockets with a standard 38 inch interface.

The second launch is also on a SpaceX Falcon 1 out of Kwajalein Atoll approximately 2 months after the preceding launch. There will be two P-PODs onboard, both of them will contain two triple CubeSats (InnoSAT and CubeSAT) built by ATSB, who also owns the primary spacecraft. This launch will not utilize the Rideshare Adapter, therefore P-PODs must be mounted directly to the payload interface cone.

The third launch is on an Air Force Minotaur 1 out of Wallops Island, Virginia and scheduled for September 2008 with the primary payload being TacSat3. Following the successful GeneSat1 launch on the TacSat2 mission, two P-PODs are now mounted on the fourth stage motor casing. One P-POD will contain a triple CubeSat (PharmaSat) by NASA Ames, and the other P-POD will contain three single CubeSats from the Aerospace Corporation (AeroCube 3), Cal Poly San Luis Obispo (CP6), and University of Maryland, Eastern Shores (HawkSat 1). Since much of the P-POD engineering analysis was complete for the previous Minotaur 1 flight, the opportunity to fly a second P-POD was realized.

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The University of Toronto Institute for Aerospace Studies (UTIAS) is also coordinating a launch of five CubeSats aboard the India Polar Satellite Launch Vehicle (PSLV) which is scheduled to launch at the end of April 2008. The CubeSat participants are CanX-2 from Canada, AAUsat-2 from Denmark, Cute-1.7+APD II and SEEDS from Japan, COMPASS-1 from Germany, and Delfi-C3 from the Netherlands. UTIAS developed their own version of a CubeSat deployer called the XPOD and will launch 5 of them on this flight with another deployer developed by the Cute-1.7+APD II team.

The fifth launch of CubeSats is on a Minotaur IV out of Kodiak, Alaska and scheduled for December 2009 with the primary payload being STP-S26. This launch was a result of a new National Science Foundation (NSF) Program; CubeSat-based Science Missions for Space Weather and Atmospheric Research. This launch is planned to be the first of many, giving CubeSats the opportunity to demonstrate a potential for large science return. In the past, CubeSats were only known for providing students with educational training, however the recent CubeSat launches and this NSF Program proves otherwise.

P-POD and CubeSat Growth

In response to growing demand for access to space for larger satellites, Cal Poly is working with NASA Ames to develop the P-POD philosophy for application into larger systems and satellites. This research is looking at creating a deployer system capable of holding a larger satellite.

This six pack P-POD can hold a satellite that is approximately equivalent to the size and mass of 6 CubeSats. This structure is designed to take the place of two P-PODs side by side, such that it can be interchangeable with existing mounting configurations for two P-PODs. The six pack design fully encloses the satellite to protect both the satellite and the launch vehicle meeting the same goals and purpose as the P-POD.3 A conceptual design for this project is shown in figure 14.

Figure 14: Picture of six pack preliminary design

The value of versatility is expanding as the P-POD becomes compatible with more and more rockets.

The following are a few highlights of P-POD mounting concepts for future launches.

The ESPA Ring

The Evolved Expendable Launch Vehicle Secondary Payload Adapter (ESPA) ring was developed by the United States Air Force to accommodate multiple secondary payloads. Consequently, P-POD mounting systems have been designed to be compatible with mounting onto the ring as a one of its secondary payloads. Several conceptual models have been developed to support the P-POD’s compatibility with the ESPA ring as shown in figures 15 and 16. The actual ESPA ring is shown in figure 17. The P-POD clusters would mount into one of the six satellite mounting holes on the ring.

Currently the Naval Post Graduate School (NPS) in Monterey, CA has begun preliminary studies and research projects in developing CubeSats for launches using the ESPA ring concept. NPS is developing the NPSCuL CubeSat Launcher. This system will be compatible with the ESPA ring and hold multiple P-PODs for launch.7,8

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Figure 15: NPSCuL CubeSat Launcher ESPA ring Concept

Figure 16: ESPA Launch Concept

Figure 17: ESPA Ring

Future Objectives

Looking ahead, the Cal Poly CubeSat program hopes to continue to improve the P-POD and increase its compatibility with more launch vehicles. In addition, programmatic goals include:

• Further develop US and international launch opportunity

• Increase number of participating organizations

• Continue to demonstrate CubeSats as a viable platform for research and low cost missions

• Continue to educate students

• Continue to contribute valuable data to science and industry

Conclusion

The CubeSat community now consists of over 90 universities from all around the world and 40 different companies and organizations, including six different NASA centers. The philosophy of “Standardization equals flexibility” has shown to be successful and continues to rapidly grow as it offers access to space to more and more developers. Figure 18 show a picture of CP4, one of Cal Poly’s own satellites. This picture was taken by another CubeSat developed by the Aerospace Corporation. The CubeSat program not only provides contributions to knowledge for research in science and industry, but also educates the next generation of scientists and engineers. Therefore, the standard CubeSat philosophy not only leads to flexibility, but contributes to the ultimate goal of accessible and responsive space for all.

Figure 18: CP4 Successfully Deployed in Space

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Acknowledgements

The authors would like to thank Riki Munakata and Jonathan Brown for their thorough review of this paper and insight in adding information and details. In addition, the authors would like to thank Wenschel Lan for her support and knowledge base on the development of the Mk III P-POD.

References

1 Toorian, Armen et. Al, “CubeSats as Responsive Satellites,” Paper no. AIAA-RS3 2005-3001, AIAA 3rd Responsive Space Conference, Los Angeles, CA, 25-28 April 2005

2 Lee, Simon et. Al, “Cal Poly Coordination of Multiple CubeSats on the DNEPR Launch Vehicle,” 18th Annual AIAA/USU Conference on Small Satellites, Logan Utah, 9-12 August 2004

3 Brown, Jonathan. Munakata, Riki. “Dnepr 2 Satellite Identification and the Mk III P-POD.”” 5th Annual CubeSat Developers’ Workshop. Cal Poly, San Luis Obispo. April 9th-11th 2008.

4 Brooks, Lori. “History of CubeSats,” RideShare Conference 2007.

5 Puig Suari, Jordi. “A Low Cost Pico-Satellite Standard for Education and Research,” Presentation to Naval Post Graduate School. Monterey, CA. 26, July 2007.

6 Leach, Rachel. Ibrahim, Mohd Suhaimi. Hamzah, Norhizam. “Cost Effective access to Space for Research & Education Payloads.” CubeSat Summer Workshop at Small Sat Conference. August, 2006.

7 Sakoda, Dan. “A Path to ESPA-Class Multiple Cubesats/P-PODs.” Naval Post Graduate School. 2007 CubeSat Developers’ Workshop. Huntington Beach, CA. April 2007. 8 Newman, James. Sakoda, Daniel. Panholzer, Rudolf. “CubeSat Launchers, ESPA-rings, and Education at the Naval Post Graduate School.” Utah State University. Conference on Small Satellites, August 2007.

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