Acta Astronautica Vol. 17, No. 3, pp. 341-346, 1988 0094-5765/88 $3.00 + 0.00 Printed in Great Britain Pergamon Press pie

DEVELOPMENT OF A "HINGELESS MAST" AND ITS APPLICATIONSt

TAKAYUKI KITAMURA~, KAKUMA OKAZAKI~, MICHIHIRO NATORI§, KORYO MIURA§, SHIGERU SATO* and AKIRA OBATA~

:[:Japan Aircraft Manufacturing Co. Ltd, 3175 Showa-cho, Kanazawa-ku, Yokohama 236 and §Institute of Space and Astronautical Science, 4-6-1 Komaba, Meguro-ku, Tokyo 153, Japan

(Received 15 December 1986; revised version received 16 July 1987)

Abstract--The new concept of continuous longeron extendible mast without hinges ("Hingeless Mast") is introduced, and its development for space applications is presented in detail. Some design parameters such as spacer pitch and stiffness of spacers are clearly arranged from the viewpoint of smooth and stable deployment and stowage. Engineering considerations for mast materials and various tests for mast components and overall mast models are also presented.

i. INTRODUCTION

Masts for space applications are very important as supporting members for many substructures or instruments, and as main structural elements for large space structures. The concepts of extending masts have great consequence for space development, because of many structural members have to be transported from the ground to space in packaged configurations. Various types of extendible masts have been investigated, and more than 15 years ago a concept of a continuous longeron extendible mast (ASTROMAST)[I,2] was developed and have been studied[3,4]. Authors have studied another configur- ation of a continuous longeron extendible mast ("Simplex Mast"[5-7], Fig. i) for several years, and it will be used for scientific instruments such as magnetic sensors, and applied for extension of a solar sell blanket.

A Simplex Mast consists of continuous longerons, integrated radial spacers and diagonal wires. By extending the concept of integrated radial spacers and replacing the role of hinges with the elastic deformation of a spacer, the new concept of an advanced Simplex Mast without hinges ("Hingeless Mast", Fig. 2) can be obtained. This concept would give the better structural accuracy and weight proper- ties, and greatly reduce the various kinds of troubles in designing and manufacturing because of the less number of various components.

In this paper, the concept of a Hingeless Mast mentioned above is introduced, and its development is presented in detail. The design chart of the relation between spacer pitch and stiffness of materials is given from the viewpoint of smooth and stable deployment and stowage.

tPaper IAF-86-205 presented at the 37th Congress of the International Astronautical Federation, Innsbruck, Austria, 4-11 October 1986.

341

2. HINGELESS MAST

The hinges of a Simplex Mast are two axis hinges shown in Fig. 2, and they give the possible kinematic change between longerons and spacers during deploy- ment and stowage. In the concept of a Hingeless Mast, the role of hinges is replaced with the elastic deformation of spacers. This concept would give some better properties for continuous longeron extendible masts. The main properties of a Hingeless Mast are as follows:

Longeron

Integrated radial spacer

Diagonal wire

Hinge

Fig. I. Extendible mast.

342 TAKAYUKI KITAMURA et al.

(a) (b)

Fig. 2. Detail of the masts. (a) Simplex Mast; (b) Hingeless Mast.

(!) Increase of the a l ignment accuracy due to no hinge looseness;

(2) Reduct ion of the n u m b e r of var ious compon-

ents; (3) Simplified processes of assembly, a r rangement

and checking; (4) Grea t reduct ion of total weight and manu-

facturing cost.

The n u m b e r of various componen t s and the total weight of the Hingeless Mas t with 150 mm dia are abou t I,/4 and I/3 in compar i son with the Simplex Mast. The problems of a Hingeless Mast are the material and the cross-sectional shape of spacers to produce the smooth and stable deployment and stowage. The mater ial might be space-proven, and have good fatigue and creep characteristics. Several models are manufac tured , and they are listed in Table 1.

coil m o d e " combined with straight and coil modes. The local coil mode is preferable for any mast applications, because the masts have higher stiffness against a side force dur ing deployment and stowage. The appropr ia te selection of the values of spacer pitch and stiffness rat io of longerons to spacers gives the desired local coil model7]. The value of these parameters for the existing con t inuous longeron extendible masts are a r ranged in Fig. 3. This design char t shows the boundary between helix mode and local coil mode. The fixed end condi t ions of inte- grated radial spacers of a Hingeless Mas t give the upper family of the chart , and the stiffness of an integrated radial spacer for a Hingeless Mas t can be lower than tha t for o ther con t inuous longeron extendible masts.

Dep loyment forces are generated by elastic energy o f the longerons and the spacers. These forces o f bo th modes are as follows[8]:

,2x E {(x)2 t {(x)2 /1 3. DESIGN EXTEND1BLEOF CONTINUOUSMAsTLONGERON [ P o ] H = ~ T ~ 2E~I~ 1 - ~ +G1J l 2 ~ -- 1

In the study of dep loyment and stowage mech- 6[GJ]s /I . ~x ~'] anism of Hingeless masts, various combina t ions of - - ~ t s m - - 2//: helix mode, deformat ion pa t te rns are investigated[6]. The two p D ~ \ L main pa t te rns are the "helix mode" , and the "local ~ \ L J

Table 1. Manufactured models

"Simplex Mast" Mast No. S-I S-2

No. of Iongerons 3 3 Length L (mm) 5000 5216 Diameter D (mm) 233 150 Spacer pitch (mm) 136 85.5 Cross section of a longeron (mm) 3.0 × 3.0 1.5 × 2.0 Spacer's material CFRP CFRP Weight (g/m) 180 140 Pcr (kg) 51.9 I 1.1 E1 (Spacer) (kg/mm 2) 2220 1350 Remarks EM .4 PM *S

for EXOS-D

"Hingeless Mast" HL-I HL-2 HL-3 HL-4 HL-5

3 3 3 3 3 957 3072 3000 957 3045 150 220 150 150 150 87 128 87 87 87

1.5 × 2.0 2.2 x 3.3 1.5 × 2.0 1.5 × 2.0 1.5 × 2.0 pC *l pc .1 PE1.2 p1.3 p1.3

38 100 42 34 34 10.7 18.5 10.7 10.7 10.7

340 2200 400 620 620 EM .4 EM .4 Payload EM .4 EM .4

recovery (Fig. 14)

*~ PC--Polycarbonate; .2 PEl--Polyetherimide; .3 Pl--Polyimide, .4 EM--engineering model; .5 PM--Proto model.

Hingeless mast 343

i

2O

~5

I.l.I

,-7 uJ 10

A ~ i Helix

/ > ~ . Hlngetess mast LocoL (_/ \ / ¢o,L ~ /

Helix HL-1

\ HL-2,4,5

Loc at 4 l • - coil x~ S--'2 A~tro •

L ~ / / I I Astro I 0.55 0.60 0.65

P / D

a. Helix m o d e

b. Local co i l mode

Fig. 3. Design chart of continuous longeron extendible masts.

6E]ll 3rtZ[GJ]s [P,k = D 2 4pD : local coil mode,

where

D = mast diameter, x/L = deploying ratio to mast length,

E1 = bending stiffness, GJ = torsional stiffness,

p = spacer pitch, I = coordinate along a Iongeron, s = coordinate along a spacer.

Figure 4 shows the relation between load and end shortening of the Hingeless Mast model (HL-I).

4. MATERIALS

The material of Iongerons for both Simplex and Hingeless Masts is unidirectional S2-glass/epoxy. This material is selected because of its high strain limit. By using this material higher stiffness can be provided for any mast diameter. The stowed strain

in the longerons is limited to 1.0% which allows repeated deployment and long-term stowage without any degradation. Special blended heat resistant epoxy resin is used to ensure its maximum stress level over a wide range of temperature ( - 1 5 0 to +200°C). And the relation between maximum stress and temperature shown in Fig. 5.

Various kinds of super-engineering plastic have been tested for spacers of a Hingeless Mast, for example, polycarbonate, polyetherimide and poly- imide. Polycarbonate is used for engineering model or ground use only because of its weakness in space environment. Polyimide board is made from lamin- ated its films, and milled to proper shape. It is most promising material for hingeless spacers because of both high strain limit and high temperature limit, and also it is a spaceproven material.

5. TESTS OF HINGELESS MAST

5.1. Mechanical property test

Some stiffness tests were conducted on a Hingeless Mast model (HL-4). Figure 6 shows the result of

P

5 E

== r'~

/ - : 0 . 0 , o , m . n ,

. . . . : Stowage ! I~ j . s

Theoretical c, • ~ - - " - ~

I / ,, x J

0 0.5 1.0 DepLoyment rat io X / L .

Fig. 4. Load-end shortening, mast model (HL- I ) .

200 --

~ 150

100

¢

5 0 -

I I I I - t 00 0 100 200 300

r ¢c)

Fig. 5. Maximum stress-temperature of longerons.

34.4 TAKAYUKI KITAMURA et al.

(N) 5

i i i t - 6 0 - 4 0 - 2 0 /

I I I I 20 40 60 80 (mm)

Fig. 6. Stiffness to side force.

5.00E+O0

5.00E-04

.,m_ i , , . , _ . l i '~ l l I l l l , ~

i 5.00E + 00

HLMT (IM-PI) 1.50E+02

i

i I

Fig. 8. Results of vibration test (Case 2).

0 . 5 - -

I I I ~ I I I -0.6~-0.4 -~-0.2 o.2(rad)0.4 0.6

-0 .5

Fig. 7. Torsional stiffness.

stiffness test due to a side force, and Fig. 7 shows the repeatability of these test results are very good. The result of compression test (Pcr) is shown in Table 1. Vibration test was also conducted with and without a top-plate, its results are shown in Table 2 and Fig. 8. First and second modes are rigid modes with support stiffness of the end hinges of the mast, and third and fourth are first and second bending, respectively.

5.2. Creep test

In order to get basic understanding of creep char- acteristics of a mast in a long-term stowage configur- ation, creep tests of longerons and spacers were carried out. The results are shown in Figs 9 and 10. Creep strain of longerons is very small (Fig. 10), and creep deformation of spacers (Fig. 9) shows over 10 deg. Figure 11 shows the results of overall alignment of a mast in long-term stowage. The tip torsional

Table 2. Results of vibration tests

No. Case l* Case 2t

I 15.8 21.3 2 25.0 24. I 3 27.9 29.7 4 33.5 40.4

*Case 1: with top-plate. tCase 2: without top-plate.

50

4 0

30

2o

IO

" :

-it: rLodoWi tlhe mgpO. deg "~f~l ' \\

I I I I 10 102 103 104

Time (h)

Fig. 9. Creep of spacers.

deformation is under 1 deg, and the slope is very small.

5.3. Fatigue test

Many fatigue tests of longerons, spacers and over- all mast configurations were conducted. These results

0 .10

0 .05

-hoLd with 150ram d i n . (1,0 , / , s t r a i n )

J 8o'c

- - - - - - R . T . I I I I

10 102 103 104 T i m e ( h )

Fig. 10. Creep of longerons.

" 0, ~, / / c

2

- in room t emp .

1

0 I 10

- - h o l d In stowed configuration

I I ,J 10 2 10 3 10 4

T ime (h)

Fig. 11. The tip torsional creep of the mast.

Hingeless mast 345

Fig. 13. Geotail spacecraft.

assure over 1000 time deployment and stowage in room environment except the case of Polyetherimide spacers.

6. APPLICATIONS

Some applications of Hingeless Masts have been developing, for example, masts for the 2-D array experiment (Fig. 12), magnetic sensor's masts for scientific satellite (Geotail--Fig. 13), and loran (long range navigation) antenna masts for rocket recovery experiment (Fig. 14). Various ground uses are also developed, since Hingeless Masts are low cost and high stiffness extendible mast, for example, tele- communication antenna, masts for search lights, and hand carrying antennas, and so on.

7. CONCLUSION

The new concept of continuous longeron extend- ible mast without hinges ("Hingeless Mast") is intro-

Fig. 12. 2-D array experiment.

Fig. 14. Rocket recovery experiment.

duced, and its development for space applications presented in detail. The elastic deformation of integrated radial spacers play the role of hinges; this concept leads to better structural accuracy and weight property, and it greatly simplifies the pro- cesses of manufacturing and checking. Deployment and stowage deformation patterns strongly depend on spacer pitch and stiffness ratio of longerons to spacers, and these design parameters are clearly arranged for various continuous longeron extendible masts. Engineering considerations for mast materials and various tests for mast components and overall mast models are also presented.

This study shows that the Hingeless Mast is a promising candidate for various present and future space applications.

REFERENCES

1. C. F. Crawford, Strength and efficiency of deployable booms for space applications. AIAA Paper 71-396,

346 TAKAYUKI KITAMURA et al.

ASS/AIAA Variable Geometry and Expandable Struc- tures Conf. (1971).

2. Astro Research Corp., Astromasts for space applica- tions, ARC-B-004 (1978).

3. Y. Soucy and F. R. Vigneron, Identification of structural properties of continuous longeron space mast. AIAA-84-0930, AIAA /ASME/ASCE/AHS 25th Structures, Structural Dynamics & Materials Conf., Palm Springs (1984).

4. M. Eiden, O. Brunner and C. Stavrinidis, Deployment analysis of the olympus astromast and comparison with test measurement. AIAA-85-0695, AIAA/ASME/ ASCE/AHS 26th Structures, Structural Dynamics & Materials Conf., Orlando (1985).

5. K. Miura, M. Natori, M. Sakamaki, K. Kakitubo and H. Yahagi, Simplex mast: an extendible mast for space-

applications. 14th International Symposium on Space Technology Science, Tokyo (1984).

6. M. Natori, K. Okazaki, M. Sakamaki, M. Tabata and K. Miura, Model study of simplex masts. 15th International Symposium on Space Technology Science, Tokyo (1986).

7. K. Okazaki, S. Sato, A. Obata, M. Natori and K. Miura, Design Consideration of mechanical and deployment properties of a coilable lattice mast. 15th International Symposium on Space Technology Science, Tokyo (1986).

8. K. Okazaki, H. Yahagi, S. Sato, A. Obata, M. Natori and K. Miura, Development of the hingeless mast. Japanese 29th Space Science & Technology Conf., Tokyo (1985) (in Japanese).