poly picosatellite orbital deployer mk iii icd

The CubeSat Program California Polytechnic State University – San Luis Obispo, CA 93407

Document Classification X Public Domain ITAR Controlled Internal Only

Poly Picosatellite Orbital Deployer Mk III

ICD

(P-POD Mk III ICD)

Revision Date Author Change Log 0 8/2/07 W. Lan Preliminary version.

0.1

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Table of Contents 1 Introduction ....................................................................................................3

1.1 P-POD Mission Objectives .....................................................................4 1.2 History and Flight Heritage .....................................................................4

2 Mechanical Interface......................................................................................5 2.1 Features .................................................................................................5 2.2 Mass Properties and Modal Characteristics ...........................................8 2.3 Interface..................................................................................................9

3 Electrical Interface .......................................................................................11 3.1 Features ...............................................................................................11 3.2 Interface................................................................................................11

4 Qualification Testing ....................................................................................13 4.1 Vibration Testing...................................................................................14 4.2 Thermal Vacuum Testing......................................................................15

List of Tables and Figures Figure 1 – P-POD Mk III........................................................................................3 Figure 2 – P-POD Mk I..........................................................................................4 Figure 3 – P-POD Mk II.........................................................................................5 Figure 4 – P-POD, Post-Deployment ....................................................................6 Figure 5 – P-POD Mechanical Features ...............................................................7 Figure 6 – P-POD Door Range of Motion .............................................................8 Table 1 – P-POD Mass Properties........................................................................9 Table 2 – P-POD’s 1st 4 Modes – Analytical Values .............................................9 Table 3 – P-POD Peak Frequency Range ............................................................9 Figure 7a: Single P-POD Bottom Panel Mounting Detail ....................................10 Figure 7b: Single P-POD Side Panel Mounting Detail ........................................10 Figure 8 – P-POD Electrical Interface Diagram ..................................................12 Table 4 – P-POD Release Mechanism Interface ................................................12 Figure 9 – P-POD Qualification Test Flow ..........................................................13 Table 5 – P-POD Test Phase Description...........................................................13 Figure 10 – NASA GEVS Qualification Profile ....................................................14 Table 6 – NASA GEVS Qualification Profile .......................................................14 Figure 11 – Thermal Vacuum Qualification Profile..............................................15 Table 7 – P-POD Thermal Vacuum Qualification Profile.....................................15 Figure 12 – Thermal Vacuum Bakeout Profile ....................................................16 Table 8 – P-POD Thermal Vacuum Bakeout Profile ...........................................16

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1 Introduction

Figure 1 – P-POD Mk III

The CubeSat program is a joint effort between Cal Poly and Stanford University to develop a new class of picosatellites: the CubeSat standard. This standard is defined in the CubeSat Design Specification (CDS). It includes information regarding nominal dimensions of the standard, the dimension tolerances, acceptable materials, the reference coordinate system, accessible areas once inside the P-POD, and other general information. The Poly Picosatellite Orbital Deployer (P-POD) is a standard deployment system that ensures all CubeSat developers conform to common physical requirements. The P-POD plays a critical role as the interface between the launch vehicle and CubeSats. It utilizes a tubular design and can hold up to 34cm x 10cm x 10cm of deployable hardware. The most common configuration is three picosatellites of equal size; however, CubeSats of different lengths can be accommodated in the same P-POD.

+Y

+Z

+X

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1.1 P-POD Mission Objectives The P-POD is designed to provide a standard secondary payload interface between CubeSats and launch vehicles. This interface can be implemented with most launch vehicles, making P-PODs an ideal responsive secondary payload. In order to satisfy all requirements for launch providers as well as CubeSat developers, the design of the P-POD meets the following requirements:

• The P-POD must protect the launch vehicle and other payloads from any mechanical, electrical or electromagnetic interference from the CubeSats in the event of a catastrophic CubeSat failure.

• The CubeSats must be released from the PPOD with minimum spin and a low probability of collision with the launch vehicle or other spacecraft.

• The P-POD must have the ability to interface with a variety of launch vehicles with minimum modifications and with no changes to the CubeSat standard.

• The mass of the P-POD should be kept to a minimum.

1.2 History and Flight Heritage The first 2 P-PODs flew in 2003 on the Eurokot launch vehicle, carrying 4 CubeSats. This Mk I version of the P-POD deployed the CubeSats at a nominal rate of 2 m/s and used a Vectran Line Cutter, provided by Planetary Systems, as the release mechanism.

Figure 2 – P-POD Mk I

The Mk II version of the P-POD flew on 2 Dnepr launch vehicles; the first launch in July 2006 consisted of 5 P-PODs carrying 14 CubeSats, and the second launch in April 2007 consisted of 3 P-PODs carrying 7 CubeSats. The P-POD Mk II deployed the CubeSats at a nominal rate of 1.6 m/s, and employed the Starsys Qwknut 3k, a separation nut system, for its release mechanism.

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A slightly modified version of the Mk II, co-developed by NASA Ames Research Center, flew on the Minotaur launch vehicle, launching NASA’s first CubeSat, GeneSat-1. This version of the P-POD used the NEA 9101B, a split spool device, as the release mechanism.

Figure 3 – P-POD Mk II

The next iteration of the P-POD, the Mk III, has larger access panels on both side panels to allow greater flexibility in the CubeSat design and to facilitate the CubeSat integration process. The Mk III can also accommodate both the Qwknut and NEA 9102G release mechanisms to meet different launch vehicle requirements. The interfaces to the P-POD Mk III will be discussed in this document.

2 Mechanical Interface 2.1 Features The tubular design creates a predictable linear trajectory for the CubeSats resulting in a low spin rate upon deployment. The satellites are deployed from the P-POD by means of a spring and glide along smooth flat rails as they exit the P-POD. After a signal is sent from the Launch Vehicle (LV) to the release mechanism, a spring-loaded door opens and the CubeSats are deployed by the main spring. The post-deployment configuration is shown in Figure 4.

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Figure 4 – P-POD, Post-Deployment The P-POD is manufactured from high-strength Aluminum 7075-T73 and encloses the CubeSats to ensure the safety of the primary payload. The resulting Faraday cage effect and a grounding bolt are utilized to meet EMC standards. The P-POD is coated with Teflon-impregnated anodization, creating resiliency to cold welding and providing a smooth, slick surface on which the CubeSats ride during deployment. Currently, the CubeSats’ exit velocity is approximately 1.6 m/s; however, this can be adjusted to meet launch vehicle requirements by replacing the main spring. 4 spring plungers in the back of the P-POD supplement the main spring in ejecting the CubeSats. Access ports provided on the side panels of the P-POD allow access to the CubeSats after integration and may be used to charge batteries and run diagnostics. These ports are staked and are not re-opened once CubeSat integration and acceptance testing is complete.

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Figure 5 – P-POD Mechanical Features

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The door is designed to open 260 degrees, measured from its closed position, at which point it contacts the bottom panel of the P-POD. Satellite deployment is guaranteed with a minimum door opening angle of 90 degrees; however, depending on how the P-POD is mounted, the door may open anywhere between 90 and 260 degrees. The door opening angle can be restricted to the desired position with an optional door stopper, shown in Figure 5. Figure 5 shows the door’s range of motion.

Figure 6 – P-POD Door Range of Motion

2.2 Mass Properties and Modal Characteristics Masses, moments of inertia and center of gravity information for the P-POD are provided in Table 1; these values are accurate within +/-10%, and the assumptions are as follows:

• Each CubeSat’s center of gravity is located at its geometric center. • Each CubeSat is inertially axisymmetric about the P-POD’s z-axis. • The NEA 9102G is the release mechanism used on the P-POD. • The P-POD door is open 90 degrees from the closed position for the post-

deployment values. The P-POD’s coordinate system is defined from the geometric center of the back panel, where the positive y-axis comes out the top of the P-POD, the positive z-axis comes out the front of the P-POD. This is shown in Figures 1 and 5.

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Table 1 – P-POD Mass Properties

Property Pre - Deployment Post - Deployment Mass 5.25 kg 2.25 kg

Ixx 0.3317 kg m2 0.1882 kg m2

Iyy 0.3295 kg m2 0.1849 kg m2Moments of Inertia

Izz 0.01689 kg m2 0.01294 kg m2

Xg 0 mm 0 mm Yg 6.560 mm 8.159 mm Centers of

Gravity Zg 216.63 mm 244.59 mm

The P-POD’s first 4 natural frequencies are shown below in Table 2. These preliminary values were obtained analytically and will be confirmed upon completion of modal testing.

Table 2 – P-POD’s 1st 4 Modes – Analytical Values Natural Frequencies

Mode Frequency, Hz 1 180 2 360 3 700 4 920

The P-POD’s peak frequency range resulting from the NASA GEVS Qualification Profile is shown in Table 3.

Table 3 – P-POD Peak Frequency Range Peak Frequencies from NASA GEVS Qualification Profile

Longitudinal (Z) Axis Lateral (X and Y) Axes 720 – 800 Hz 650 – 700 Hz

2.3 Interface The P-POD can be mounted directly to the LV or through an adapter on any mounting surface specified in Figure 7. Mounting holes (up to M6-size bolts) can be added anywhere on the mounting surfaces. Figure 6 also shows mounting hole patterns for past missions; however, these can be modified to accommodate any launch vehicle.

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aero

Line


Figure 7a: Single P-POD Bottom Panel Mounting Detail

Figure 7b: Single P-POD Side Panel Mounting Detail

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3 Electrical Interface 3.1 Features The P-POD’s electrical interfaces to the launch vehicle include the release mechanism connector, an optional deployment sensor, and a grounding bolt. The CubeSats are enclosed in the P-POD to ensure the safety of the primary payload, and the resulting Faraday cage effect, along with a grounding bolt, are designed to meet EMC standards. The grounding bolt is located at the rear end of the P-POD on the top panel (see Figure 5). Deployment of CubeSats is initiated by a standard pyro signal from the LV. The signal triggers the release of the mechanism, which in turn allows the door to open and the deployment sequence to begin. In order to minimize shock to the CubeSats, the release mechanism does not utilize any pyrotechnics; however, the signal it receives is an industry standard pyro signal. No batteries or control electronics are required on board to make the system function. A deployment sensor installed on the P-POD near the door is available to provide telemetry data to the launch vehicle. The switch is wired as a normally-closed circuit when the door is closed; thus, when the door has opened, the telemetry data sent back to the launch vehicle is an open circuit. This provides assurance that the door stays closed until the CubeSats are deployed. Two switches have been used thus far on the P-POD; the Honeywell 3M1 switch, and a Saia-Burgess snap-action switch. Two Saia-Burgess switches, used on the Dnepr launches, are the standard hardware for the P-POD; this redundant circuit is shown in Figure 7. However, as demonstrated by the use of the Honeywell 3M1 switch on the Minotaur launch in December 2006, any standard snap-action switch with similar electrical specifications can be used on the P-POD to meet the necessary requirements of the launch vehicle. An example cable interface from these P-POD features to the launch vehicle is shown in Figures 5-7.

3.2 Interface The following diagram is an example of the electronic interface between the P-POD and the launch vehicle. There is one redundant pyro signal and one redundant telemetry signal. These signals can be combined in 1 connector, or it can be left as 2 separate connectors. Additionally, EMI closeout can be achieved by using shielded wires, although it is not shown in Figure 8.

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Figure 8 – P-POD Electrical Interface Diagram

The P-POD Mk III is designed to accommodate both the Starsys Qwknut 3k, a separation nut system, and the NEA 9102G, a split spool device. The specifications and requirements of each device are show in the following table.

Table 4 – P-POD Release Mechanism Interface Release Mechanism Specifications

Signal Release Mechanism

Resistance Range (Ohms) Current Range

(A) Voltage Range

(V) Actuation Time

(ms) Starsys Qwknut

3k 3.9 – 4.1 3.5 – 5.5 15-21 100

NEA 9102G 1.2 - 1.6 2.0 – 20 3.0 - 30 45

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4 Qualification Testing All P-POD hardware is tested extensively to assure safe and reliable operation. A series of qualification tests are performed before the P-POD is ever put into service. The testing flow is shown in Figure 9, and the requirements for each phase of P-POD testing are outlined in Table 5.

Figure 9 – P-POD Qualification Test Flow

Table 5 – P-POD Test Phase Description Prototype Engineering Unit Flight Units

Mission Phase During development phase.

Qualification of new

design.

Qualification of

multiple flight units.

Documentation Initial test plan.

Used to develop test plan for flight units.

Extensive

documentation for traceability.

Pre/post test deployment and

inspection.

Tests Performed

Wide variety of tests. Vibration T-VAC

Functional Deployment

Tests performed to LV and GEVS

specifications.

LV qual vibration.

Thermal bakeout.

LV acceptance vibration after

integration. CubeSats must be qualification tested, as per the CubeSat Design Specification and launch vehicle requirements, before being integrated into qualification-tested flight P-PODs. After this point, the fully-integrated unit goes through acceptance testing before it is sent to the launch site for launch vehicle integration.

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4.1 Vibration Testing Vibration tests are performed under the NASA GEVS Qualification Profile, shown in Figure 10, for prototype and engineering units. The values for this profile are listed in Table 6. This vibration profile encompasses most launch vehicle qualification profiles.

Figure 10 – NASA GEVS Qualification Profile

Table 6 – NASA GEVS Qualification Profile NASA GEVS Qualification Profile

Frequency, Hz ASD Level (G2/Hz) 20 0.026 20 – 50 +6 dB/oct 50 – 800 0.16 800 – 2000 -6 dB/oct 2000 0.026 Overall 14.1 Grms

Flight units are subjected to the qualification and acceptance profiles specified by the launch vehicle provider.

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4.2 Thermal Vacuum Testing Thermal Vacuum tests are also performed to bake out hardware and ensure predictable behavior in different environments. The chamber pressure is taken down to a vacuum level of at least 5x10-5 Torr before the thermal cycle begins. 4.2.1 Qualification Testing The P-POD undergoes the following thermal-vacuum profile for qualification testing shown in Figure 11.

Figure 11 – Thermal Vacuum Qualification Profile

Table 7 – P-POD Thermal Vacuum Qualification Profile

Thermal Vacuum Qualification Profile Temperature, ˚C Soak Time, min.

25 Initial -30 30 70 30 -30 30 70 30 25 Final

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4.2.2 Bakeout Profile Each flight P-POD is also subjected to a bakeout cycle to meet out-gassing requirements. This profile is shown in Figure 12.

Figure 12 – Thermal Vacuum Bakeout Profile

Table 8 – P-POD Thermal Vacuum Bakeout Profile

Thermal Vacuum Bakeout Profile Temperature, ˚C Soak Time, min.

25 Initial 70 60 25 60 70 60 25 Final

The P-POD is assembled in a class 100,000 cleanroom, and all CubeSats are required to meet this standard as well; this level of cleanliness is maintained from assembly through integration. The P-POD is not an airtight container and is not hermetically sealed, which means that it does not vent at any point. Questions? Email: [email protected] Phone: +1 (805)756-5087

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poly picosatellite orbital deployer mk iii icd

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