cubesat deployer testing and verification approach€¦ · the test facility was assembled to...

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International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 11, November 2018, pp. 867–876, Article ID: IJMET_09_11_088

Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=9&IType=11

ISSN Print: 0976-6340 and ISSN Online: 0976-6359

© IAEME Publication Scopus Indexed

CUBESAT DEPLOYER TESTING AND

VERIFICATION APPROACH

Konstantin Klimov, Ivan Pushkar, Anatoly Shapovalov and Dmitry Rachkin*

Bauman Moscow State Technical University, 5, 2-nd Baumanskaya Street, Moscow, Russia

105005

* Corresponding Author

ABSTRACT

One of ASRTU spacecrafts mission purposes is to achieve developmental verification

of the CubeSat format satellites launch from a small spacecraft and their subsequent

interaction with each other including, in particular, testing the intersatellite

communications and cloud technologies. All the spacecraft should match the jointly

developed requirements regarding unified mechanical, electrical and traffic interfaces.

In this paper we provide the results of ground tests of CubeSats deployment from a

small spacecraft. The results of experiments were used to refine the designed computer

models, the structure of the container and its mounting hardware, as well as the sequence

of deployment of satellites depending on their number and form factors.

Key words: Picosatellite deployer, verification and testing, dynamics simulation, small

spacecrafts.

Cite this Article Konstantin Klimov, Ivan Pushkar, Anatoly Shapovalov and Dmitry

Rachkin, Cubesat Deployer Testing and Verification Approach, International Journal of

Mechanical Engineering and Technology, 9(11), 2018, pp. 867–876.

http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=9&IType=11

1. INTRODUCTION

One of the projects being implemented in the framework of the Association of Sino-Russian

technical universities (ASRTU) and which is aimed at further development of scientific and

technological cooperation between Russia and China is concerned with the design and

implementation of a joint space mission involving design of interacting small spacecrafts. For

this mission, one of its purposes is to achieve developmental verification of the CubeSat format

satellites launch from a small spacecraft and their subsequent interaction with each other

including, in particular, testing the intersatellite communications and cloud technologies. An

onboard container (Fig.1) is capable of launching CubeSats of 1U–6U. Picosatellites are arranged

inside the deployer along 4 guides, closed by the cover plates and forced by pusher springs [1].

All the spacecrafts should match the jointly developed requirements regarding unified

mechanical, electrical and traffic interfaces.

Konstantin Klimov, Ivan Pushkar, Anatoly Shapovalov and Dmitry Rachkin


Figure 1 1U - 6U Picosatellite Deployer

Developers of the picosatellite in Bauman Moscow State Technical University identified a

list of requirements to its separation, such as angular velocities have to be not more than 5°/sec

on three axises, linear velocity must be at least 0.3 m/s but not exceed 1 m/s [2]. This article is

covered to development of special deployer for performing this task under the specified

restrictions.

2. VERIFICATION APPROACH

To prove the deployer satisfy the ejection velocities requirements the verification process (Fig.

2) was developed. First two steps are to create a dynamic model of CubeSat 1U ejection process

in zero gravity condition and modify it to ground test conditions. The modeling of the test facility

showed that imperfections of weightlessness block system are not more than imperfections of the

separation process, so the feasibility of the experiment was proved. Then the ground experiment

of the ejection process was carried out and compared to its model. The fourth step is reducing

validated dynamic ground test model to zero gravity conditions. And the last step is scaling

verified CubeSat 1U model up to CubeSat 6U model.

Figure 2 Picosatellite deployer verification process

Cubesat Deployer Testing and Verification Approach


3. DYNAMICS SIMULATION

Dynamics simulation is implemented by the MSC.Adams software. The model is shown on Fig.

3. Features of the model are written in table 1. The results of satellite zero gravity conditions

ejection simulation are shown on Fig. 4.

Figure 3 The dynamics model for zero gravity conditions

Table 1 Dynamics simulation features

Software MSC Adams 2012

Functions Contact, Vector Force, Joint

Contact task solver Parasolid, Impact

Integrator GSTIFF

Index reducing method SI1

Allowable integration error 1∙10-5

Max step of integration 1∙10-5

Max order of integration 6

Max number of iterations for convergence 15

Figure 4 Results of zero gravity conditions satellite ejection simulation



4. TESTING FACILITY

The test facility was assembled to provide the ground testing of the deployer and verification of

the mathematical model. The deployer was fixed on a massive base (Fig. 5). The deploying

satellite mockup was in the state of weightlessness because of a special block system (Fig. 6).

Figure 5 The deployer fixed on a massive base

Figure 6 The block system

The satellite was built as prototype of already existed «BMSTU Sail» satellite [3] and has the

same mass and inertia characteristics (Fig.7). The values are listed in Table 2.

Figure 7 Satellite and mockup models



Table 2 Mass and inertia characteristics

Satellite Mockup

Mass, kg 1.051 1.074

Main inertia moments, kg∙m2∙10-3

1.633

1.734

1.909

1.461

1.722

1.846

The mockup has a gimbals (Fig.7) made from cylindrical hinges. It was necessary a

suspension point was at the center of mass. Because of it the mockup was balanced by attaching

small masses (about 0.5 grams) on its edges.

Figure 8 The gymbals

A micromechanical gyroscope for measuring angular velocities is installed at the mockup. To

be able to get data without influence on the mockup’s movement process, radio transmission is

used. The data is transmitted to the laptop in real time via a radio channel. The mesuring device,

data transmittion sytem and software was developed by authors and information about system is

on the fig. 9.



Figure 9 The measuring system

5. DETERMINATION OF THE PHYSICAL CHARACTERISTICS

The mathematical model of ground testing required such values of physical quantity as Young’s

modulus and damping ratio of the cable that links the mockup and the counterweight.

To determine the Young’s modulus the cable is loaded and the deformation is measured. The

value of elastic modulus is calculated from Hooke’s law:

/E σ ε= (1)

Measurements of the damping ratio are carried out on an oscillatory system with a high-speed

camera.

The principle of the system is based on the graphical measurements of the oscillatory process

decrement. The measuring of the cable position was made with the help of Adobe After Effects

CC 2015. Using the Track Motion function, the position of the selected area in the frame was

analyzed (Fig. 10). The result is recorded in a text file.



Figure 10 The Track Motion function

Using the Wolfram Mathematica the plot of the oscillatory process was built. Measuring the

values of two neugboring extrema and calculating the decrement by the formula:

( )ln

( )

x t

x t Tδ =

+ (2)

The value of the decrement is 0.324.

6. MATHEMATICAL MODEL OF THE GROUND TESTING

Mathematical model of ground experiment is a modified space condition model. The block

system, gravity and spherical joint are added (Fig. 11).

Figure 11 The dynamics model of ground testing



The results of ground testing modeling have the same character as the space condition model

(Fig. 12). This fact confirms the correctness of our experiment.

Figure 12 Results of zero gravity conditions satellite ejection simulation

7. EXPERIMENT CARRYING OUT

Additional simulation of the test facility including cable stiffness and damping properties, and

block system friction properties in MSC.Adams was carried out. The results of comparison of

the experimental data and the results of mathematical simulation of the test facility are shown on

fig.13. The dynamic model of the test unit was verified by the ground experiment and the dynamic

model of the deployer in flight conditions was also verified by this results. The picture from the

video of the satellite mockup ejection from the deployer is shown on Fig. 14.

Figure 13 A comparison of the angular velocities from numerical experiment and ground conditions

modeling



Figure 14 The mockup ejection from the ground deployer

8. MODEL SCALING

Picosatellite deployer capacity is up to 6U CubeSat, so two more mathematical models of ejection

process in zero gravity conditions were created by scaling and modifying verified 1U model.

The first model is CubeSat 3U, results of the simulation are shown on Fig. 15. The second one is

a combination of 1U and 2U CubeSats which are located on top of each other (Fig. 16). Because

of a bigger friction force work between guides and the CubeSat located at the bottom, there are

different linear velicities after the ejection (Fig. 17).

Figure 15 A combination of 1U and 2U CubeSats. Deployer’s walls are hidden

Figure 16 Results of 3U CubeSat zero gravity conditions ejection simulation



Figure 17 Results of 1U and 2U CubeSats zero gravity conditions ejection simulation

8. CONCLUSION

The deployer, the test facility and a measurement system were designed, manufactured and

assembled by paper authors. Mathematical simulation of the device and the test facility in the

MSC.Adams package is made. The verification of the mathematical model is carried out.

ACKNOWLEDGMENTS

The research was performed at Bauman Moscow State Technical University with the financial

support of the Ministry of Education and Science of the Russian Federation under the Federal

Target Program "Research and development on priority directions of scientific and technological

complex of Russia for 2014-2020". Agreement # 14.577.21.0247 (unique identifier

RFMEFI57717X0247).

REFERENCES

[1] CubeSat Design Specification Rev. 12. The CubeSat Program, Cal Poly SLO.

https://static1.squarespace.com/static/5418c831e4b0fa4ecac1bacd/t/56e9b62337013b6c063

a655a/1458157095454/cds_rev13_final2.pdf (date of the application 10.09.2018).

[2] Mayorova, V., Popov, A., Nerovnyy, N., Rachkin, D. And Tenenbaum, S. Two-Blade Solar

Sail Dynamics. Advances in Solar Sailing / Macdonald M. Springer Berlin Heidelberg, 2014,

pp. 717-735.

[3] Rachkin, D., Tenenbaum, S., Dmitriev, A., Nerovnyy, N., Kotsur, O., and Vorobyov, A. 2-

blades deploying by centrifugal force solar sail experiment, Proc. of 62nd International

Astronautical Congress, 2011, pp. 9128–9142.

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