Development of Supersonic Parachute for Japanese Mars Rover Mission

Trans. JSASS Aerospace Tech. Japan Vol. 14, No. ists30, pp. Pe_87-Pe_94, 2016

By Hiroki TAKAYANAGI,1) Toshiyuki SUZUKI,1) Kazuhiko YAMADA,2) Yusuke MARU,2) Shingo MATSUYAMA3) and Kazuhisa FUJITA1)

1)Research and Development Directorate, JAXA, Chofu, Japan 2)Institute of Space and Astronautical Science, JAXA, Sagamihara, Japan 3)Aeronautical Technology Directorate, JAXA, Chofu, Japan

(Received July 31st, 2015)

For landing a rover on the Mars ground, supersonic parachute has been developed in JAXA. Key technologies are categorized in aerodynamic performance, mechanical strength, ejection system, and validation method of the design for pre-flight model. So far, we have performed experiments in low-speed, transonic, and supersonic wind tunnels in Chofu aerospace center and ISAS. From these experiments, we have investigated aerodynamic performance such as drag coefficients, opening load factor, and stability of the parachute. We have also evaluated the mechanical strength in these wind tunnel tests. In addition, ejection system with automobile airbag inflator has been developed and a vertical ground test is performed in Noshiro Rocket Testing Center.

Key Words: Supersonic Parachute, Mars EDL

Nomenclature China officially announced plans to go forward with their Mars mission planned for 2020. The program includes plans 2 A : Reference area, m for Mars sample return in 2030. India has already achieved CD : Drag coefficient their first interplanetary mission since 2014 called as D : Diameter Mangalyaan. As a next step, they also plan to land a rover on D0 : Nominal diameter the Mars ground in 2020’s. Dp : Projected diameter of inflated parachute In Japan, several missions to Mars have been planned. Fre : Unfurling resistance force, N NOZOMI was Japanese first Mars explorer and its main L : Length mission was to research Martian upper atmosphere by m : Mass, kg focusing on the interaction with solar wind. However, it was 2 q∞ : Free-stream dynamic pressure, N/m unable to achieve Mars orbit due to electrical failures. We

TB : Tension at mouth of deployment bag, N have also planned a mission with the entry into the Martian η : Wake parameter (ratio of drag coefficient atmosphere called as MELOS. In order to achieve this of deployment bag in vehicle wake to that mission, supersonic parachute is needed to be developed in in free stream) order to decelerate in Martian atmosphere, which is thinner Subscripts than earth’s atmosphere. From a present trajectory plan, a 1) B : Band parachute is opened at around 8 km altitude and Mach 1.79. Bent : Bent At that time, a dynamic pressure is about 580 Pa. After D : Disk deceleration lower than 90 m/s, a lander is landed by a sky G : Gap crane. : Suspension line In United States, supersonic parachutes have been SL 2, 3) v : Vehicle developed for planetary explorations from 1950s. They have developed and used Disk-Gap-Band (DGB) parachutes 1. Introduction for a number of Mars missions from Viking in 1972 to MSL in 2012. In MSL mission, they developed a mortar-developed Recently, several missions with the entry into the Martian 21.5-m reference diameter DGB parachute, the largest atmosphere have been proposed all over the world. On parachute ever to be deployed on the surface of Mars. EDL August 6, 2012, Curiosity landed the Martian ground reconstruction indicates that parachute mortar deployment successfully. United States also plans to launch InSight in was initiated at a Mach number of approximately 1.75 and 4) 2016. ESA is now planning to launch ExoMars rover in 2018 dynamic pressure of 493.6 Pa. Parachute release occurred after the launch of the orbiter and the lander in 2016. In Asia, some 116.6 seconds after mortar fire, as responsibility for

Pe_87 Trans. JSASS Aerospace Tech. Japan Vol. 14, No. ists30 (2016) terminal descent was handed by the “Skycrane” thrusters. On dynamic pressure. the other hands, ESA has developed a 12.0 m nominal diameter DGB parachute for ExoMars mission.5) In this 3. Aerodynamic Performance and Mechanical Strength mission, the maximum deployment Mach number is 2.1. In Japan, although drop tests of supersonic parachute from a In this study, in order to evaluate aerodynamic performance balloon6) and a sounding rocket7) have been carried out in such as drag coefficients, stability, and mechanical strength, 1990s, the methodology of supersonic parachute wind tunnel tests were performed in low-speed, transonic and developments has not been established yet. Then, we started supersonic wind tunnels developed in Chofu aerospace center a development of supersonic parachute in 2012. So far, we and ISAS. have searched past supersonic parachutes, designed a concept, 3.1. Supersonic wind tunnel test in Chofu aerospace center and performed wind tunnel tests. When we want to design a Supersonic wind tunnel tests were performed with scaled new parachute, we need to perform various types of membrane parachute models manufactured by Fujikura Koso experiments and CFD calculations in order to optimize a lot of KK. An example picture of model is shown in Fig. 1. parameters, such as materials, shape, and sizes. In our research, Parameters of these models are shown in Tables 1 and 2. In we have developed a parachute with Viking scaled geometry these tables, drag coefficients at low velocity measured in to reduce our time and costs. So far, we have performed Fujikura Koso KK are also tabulated. Two types of parachute, experiments in low-speed, transonic, and supersonic wind tunnels in Chofu aerospace center and ISAS. From these experiments, we have investigated aerodynamic performance such as drag coefficients, opening load factor, and stability of the parachute. In addition, ejection system with automobile airbag inflator has been developed and a vertical ground test is performed in Noshiro Rocket Testing Center.

2. Development Scenario for Supersonic Parachute

In order to develop a supersonic parachute for our Mars Mission, we categorized key technologies in aerodynamic performance, mechanical strength, ejection system, and validation method of the design for pre-flight model. So far, we have performed experiments in low-speed, transonic, and supersonic wind tunnels. From these experiments, we have investigated aerodynamic performance such as drag coefficients, opening load factor, and stability of the parachute. We have also evaluated the mechanical performance in these wind tunnel tests. However, we should take into account the effect of the differences in dynamic pressure, scale, and Fig. 1. Parachute model for wind tunnel tests. fabricate materials between the wind tunnel tests and real Mars entry conditions. Therefore, fluid structure interaction Forebody analysis will be performed in order to evaluate these differences. In addition, the effects of the mounting structure were observed in the wind tunnel tests as mentioned in section 3. Therefore, we will perform the drop tests from a helicopter, a scientific observation balloon, and a sounding rocket. First, Strut we will perform a drop test with a small-size DGB parachute from a helicopter in order to evaluate the ejection system at same dynamic pressure. In this case, the maximum Mach number will be about 0.3. As a second step, we will perform a drop test with a small-size DGB parachute from a scientific observation balloon in order to evaluate a drag coefficients, Flange at undersurface in opening load factor, and stability of the parachute at around measurement position M = 1.4. In this case, dynamic pressure will be about 5.1 kPa. Finally, we will perform a drop test with a small-size DGB parachute from a sounding rocket in order to evaluate a drag coefficients, opening load factor, and stability of the parachute at same Mach number and same dynamic pressure. In addition, we will perform a drop test with a full-scale parachute from a helicopter in order to evaluate the mechanical strength at same Fig. 2. Schematic of mounting structure in supersonic wind tunnel at Chofu aerospace center. 2

Pe_88 H. TAKAYANAGI et al.: Development of Supersonic Parachute for Japanese Mars Rover Mission six models, were used for these experiments. As mentioned in Table 1. Parameters of parachute small models for transonic and the introduction, the shape is DGB-type Viking scaled supersonic wind tunnel tests. geometry. The material of disk and band is 38-g woven nylon. Parameters Small - 2 Small - 3 Small -4 Its permeability is between 0.35 and 0.61 m3/m2/s. When the Nominal D0 156 158 158 fabric of band and disk was broken, it was repaired after diameter, mm experiments. The schematic of mounting structure for the Projected Dp 115 109 102 membrane parachute models is shown in Fig. 2. The shape of diameter of the forebody is consists of circular cone and cylinder. Two inflated types of the forebody, of which diameter were 20 and 32 mm, parachute were used for the experiments with the small-size models. Gap length, LG 7.3 6.0 5.6 The 40-mm-diameter forebody was used for the mm experiments with the large-size models. The parachute drag Band length, LB 18.5 20.2 20.2 was measured by means of a single-axis load cell mm (Measurement specialties Inc., XFTC-301) mounted within Vent diameter, Dv 9.3 9.8 9.8 the forebody after an amplifier (TEAC Inc., SA-59) at a rate mm of 2 kHz. Drag is calculated in the same method as the Viking Suspension L 287 282 283 era wind tunnel programs by following equation. 8) s line length, (1) mm ிವ Number of N 24 24 24 ஽ బ These measurement systemܥ ൌ ௤ௌwas calibrated with weights. gore

The tests were recorded with Shclieren system on high speed Drag CD 0.69 0.58 0.64 video camera (1 kHz). The ejection method of membrane coefficient in parachute models is shown in Fig. 3. After attaining the test low speed conditions, gas was injected inside the forebody from a wind tunnel compressor set outside the wind tunnel. A silicon skin set between the packed parachute and the eye nut was inflated by Table 2. Parameters of parachute large models for transonic and the injected gas. As a result, the packed parachute was ejected. supersonic wind tunnel tests. The maximum pressure of the compressor was set about 0.8 Parameters Large -A Large -B Large-C MPa. Nominal D0 244 245 245 diameter, mm Projected D 173 173 158 Load cell p Packed diameter of parachute inflated Sealed with cray parachute

Gap length, LG 10.1 9.9 10.3 mm

Band length, LB 28.4 28.5 28.6 Gas injection from the mm compressor Vent diameter, Dv 18.3 19.6 16.0 (~ 0.8 MPa ) mm Suspension Ls 423 424 432 Silicon coating skin line length, mm Number of gore N 24 24 24

Drag C 0.53 0.52 0.38 Packed parachute is ejected D coefficient in

by the gas low speed wind Fig. 3. Ejection method of membrane parachute model in the tunnel supersonic wind tunnel test.

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The drag coefficients are estimated by Eq. (1) as shown in Fig. 4. Stable opening is achieved lower than Mach 2.0. However, large fluctuation and damage were observed faster than Mach 2.0. In this figure, the drag coefficients measured in ISAS supersonic and transonic wind tunnels are also shown. As the flow velocity and dynamic pressure increased, the drag coefficient decreased. In addition, the influence of the mounting structure was observed. In order to evaluate the reason why the drag coefficient decreases as dynamic pressure increases, we will perform a fluid structure interaction analysis. At M = 1.4, the drag coefficients measured in Chofu aerospace center were smaller than 0.4. It is because the parachute models were located at the cross section of the reflected shock wave by walls generated by the forebody. It was also observed by the Schlieren pictures.

The opening load factor, Ck, was evaluated with the averaged drag for 2 ms as following equation as shown in Fig. 5. (2) ஼ವሺሻ ௞ ஼ವሺሻ As a result, in someܥ casesൌ Ck was larger than 2.0. Opening Fig. 5. Opening load measured in transonic and supersonic wind load factor is influenced by packing methods of the parachute. tunnels. Therefore, parachute should be packed inside a parachute bag in order to avoid the parachute opening before total extension at M = 1.4. Therefore, these values should be evaluated in the of the suspension line. However, in the wind tunnel tests, we drop test from a helicopter and a scientific observation performed the wind tunnel tests without packing inside a balloon. parachute bag owing to its small size. As a result, in some 3.2. Low-speed wind tunnel test experiments, the parachute was opened before total extension In order to evaluate the aerodynamic performance and of the suspension line. In addition, as mentioned above, flow mechanical strength with larger scale model, low-speed wind behind the forebody is influenced by the reflected shock wave tunnel tests were performed with 951-mm nominal diameter model as shown in Table 3. In this case, we measured drag coefficients with two-types of mounting structure. One of them is the method with the metal jig on the strut as shown in Fig. 6. The other of them is the method with wires set on the walls as shown in Fig. 7. The drag coefficient were measured as shown in Fig. 8. Setting in low-speed wind tunnel test is shown in Table 4. In these experiments extension lines with metal or ZYLON were added between the load cell and the swivel of the parachute in order to evaluate the effect of the position of the position of the parachute. When the flow velocity was lower than 25 m/s, parachute was opened behind the strut owing to the weight of the base plate and the load cell. As a result, the drag coefficient measured with the strut was smaller than that measured with the wires. When the flow velocity was faster than 30 m/s, the error in drag coefficient was less than 2%. As the flow velocity and dynamic pressure increased, the drag coefficient decreased from 0.6 to 0.54. In these experiments, parachute materials were not damaged. In order to evaluate the reason why the drag coefficient decreases as dynamic pressure increases, we will perform a fluid structure interaction analysis.

Fig. 4. Drag coefficients measured in transonic and supersonic wind tunnels.

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Base plate Rod pin Load cell

Eye nut

Strut

Fig. 7. Mounting structure with wires on the walls for low-speed wind tunnel. Fig. 6. Mounting structure with the metal jig on the strut for low-speed wind tunnel.

Table 3. Parameters of parachute models for low-speed wind tunnel tests.

Parameters

Nominal diameter, mm D0 951

Projected diameter of inflated parachute Dp 680

Gap length, mm LG 41

Band length, mm LB 115

Vent diameter, mm Dv 70

Suspension line length, mm Ls 1690 Number of gore N 12

Table 4. Setting in Low speed wind tunnel test.

Run No. Mounting method Extension line 003 Strut Nothing 004 Strut Nothing Fig. 8. Mounting structure with wires on the walls for low-speed 007 Strut Nothing wind tunnel. 009 Wire Metal(111cm)

010 Wire Metal(111cm)

011 Wire Nothing 4. Ejection System

012 Wire Nothing In our parachute system, automobile airbag inflators are 013 Wire Nothing taken into account as candidates. First, we investigated the 015 Wire ZYLON(120cm) initial performance requirements of the ejection velocity in 016 Wire ZYLON(214cm) Mars condition according to the method in Viking era. Second,

we performed a vertical ground test in Noshiro Rocket Testing Center.

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4.1. Minimum required ejection velocity Table 7. Integral parameters of Mars EDL Demonstrator for MELOS The minimum required ejection velocity in Mars condition mission. is estimated in accordance with a method in Ref. 9). In this Parts Value, kg integral to the equation for the linear motion of an inelastic Disk KD 1.57 method, the motion of the parachute is obtained by a first Gap KG 0.10 parachute deployed in the lines-first mode. The governing Band KB 0.26 equation of relative motion is derived in the following Suspension line KSL 1.95 equation: Riser KR 0.56 re (3) Vehicle wake KW 1.70 ��e��

As mentioned� � �in the �introduction,� �the�� shape is DGB-type Viking scaled geometry. The parachute parameters are listed Table 8. Unfurling resistance forces of Mars EDL Demonstrator for in Table 5. The mass of the parachute parts are estimated as MELOS mission. listed in Table 6. As a result, the integral parameters defined Parts Value, N

by following equation are calculated as shown in Table 7. Disk (Fre)D 34.3 (4) Gap (Fre)G 34.3 � Band (Fre)B 34.3 �e Unfurling resistance forces�� for� the parts are set by measured Suspension line (Fre)SL 34.3

values as listed in Table 8. Riser (Fre)W 49.0

Table 5. Parachute parameters of Mars EDL Demonstrator for MELOS Dynamic pressure distribution at parachute deployment mission. condition (M = 1.61, H = 8 km, U = 604.6 m/s) is calculated Parameters Value by JONATHAN code10) as shown in Fig. 9. By using this Model type DGB-type dynamic pressure distribution, wake parameters are obtained 2 Nominal surface area, m S0 56.9 as listed in Table 9. As a result, the required ejection velocity at Mars parachute deployment conditions is estimated as Nominal diameter, m D0 8.51 Number of gore N 24 follows.

Number of riser NR 3 � Suspension line length, m Ls 14.47 � � �� Riser length, m LR 7.05 req �� Disk diameter, m Dp 6.13 (5) � �� Disk length, m LD 2.8 � �� 2 � �v ∑ ��∑ �� Gap length, m LG 0.34 Band length, m LB 1.03 ≅ 28.2m/s Bent diameter, m DBent 0.596

Table 6. Parachute parts mass of Mars EDL Demonstrator for MELOS mission. Parts Value, kg

Disk mD 2.09

Gap mD 0.10

Band mB 1.15 Bent mBent 0.09

Suspension line mSL 4.41

Riser mR 2.69

Total of fabricate material mFT 10.5

Swivel mSV 1.42

Reefing cutter mRC 1.0 Parachute bag mBag 1.0 Fig. 9. Dynamic pressure distribution at parachute deployment Total mt 13.9 condition (M=1.61, H=8km, U=604.4m/s).

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Table 9. Wake parameters. Parachute box Position Averaged region Value Riser connector

X, m Y, m Parachute Riser 0 – 7.1 0.14 Suspension line 7.1 – 21.5 0.76 Band 21.5 – 22.5 ±0.125 0.85 Gap 22.5 – 22.9 0.88 Base plate Disk 22.9 – 25.7 0.90

4.2. Vertical ground test In order to evaluate the model for the parachute ejection, a vertical ground test was performed in Noshiro Rocket Testing Center. The experimental setup for this experiment is shown in Fig. 10. Detailed schematic of the ejection system is shown in Fig. 11. The inflator was fired by an electrical signal from a stabilized power supply. The high-pressure gas was ejected inside the airbag. The parachute was ejected by the expanding force of the airbag. This airbag was made with two layers of ZYLON and Silicon. The inner layer is an air-tight cylinder made of a silicon rubber sheet. The ZYLON cylinder is adopted as the outer layer to withstand the tensile stress due to the inner pressure. ZYLON has a high thermal stability and a high tensile strength and has been used for flare-type Fig. 10. Experimental setup for ground vertical test. membrane aeroshell. 11) Parameters of the airbag is listed in Table 10. The motion of the parachute was estimated by the high-speed camera, of which frame rate was 1200 fps, and Parachute video camera, of which frame rate was 60 fps as shown in Fig. 12. The velocity was estimated by the time differential approach with the motion as also shown in Fig. 12. From these results, the ejection velocity was estimated as 30 m/s.

Table 10. Airbag size of vertical ground test. Parameters Value, mm Designed Expanded Diameter D 210 230 Length L 255 395 Withstanding Pmax 0.4 MPa (measured by Airbag pressure breaking test) Adapter

5. Conclusion Inflator

For landing a rover on the Mars ground, supersonic Fig. 11. Detailed schematic of the ejection system. parachute has been developed in JAXA. Key technologies are categorized in aerodynamic performance, mechanical Noshiro Rocket Testing Center. From the motion of the strength, ejection system, and validation method of the design parachute estimated by the high-speed camera and video for pre-flight model. In order to evaluate the drag coefficients, camera, the velocity was estimated as 30 m/s by the time stability, and survivability, tests were performed in low-speed, differential approach with the motion. transonic and supersonic wind tunnels developed in Chofu aerospace center and ISAS. As the flow velocity and dynamic pressure increased, the drag coefficient decreased. In addition, the influence of the mounting structure was observed. In order to evaluate the reason why the drag coefficient decreases as dynamic pressure increases, we will perform a fluid structure interaction analysis. Ejection system with automobile airbag inflator has been also developed and a vertical ground test was performed in

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and Rockets, 6(1969), pp. 621-623. 4) Witkowski, A., Kandis, M. and Adams, D. S.: Mars Science Laboratory Parachute System Performance, Aerodynamic Decelerator Systems Technology Conferences, AIAA 2013-1277, Daytona Beach, Florida, 2013. 5) Saunders, A., Underwood, J. C., Lingard, J. S. and Langlois, S. :ExoMars EDM Parachute System: Update on Design and Verification, AIAA Aerodynamics Decelerator Systems Conference, AIAA 2013-1278, Daytona Beach, Florida, 2013. 6) Nakajima, T., Hiraki, K., Hinada, M., Yamagiwa, T. and Ohta, S.: Guidance experiment of gliding parachute dropped from balloon, 13th Aerodynamic Decelerator Systems Technology Conference, AIAA 1995-1541, Clearwater Beach, Florida, 1995. 7) Hinada, M., Akiba, R., Nishimura, J. and Godai, T: Payload Recovery Experiments by Sounding Rockets and Baloon in Japan, 11th Aerodynamic Decelerator Systems Technology Conference, AIAA 91-828, San Diego, California, 1991. 8) Sengupta, A., Roeder, J., Kelsch, R., Wernet, M., Kandis, M. and Witkowski, A.: Supersonic Disk Gap Band Parachute Performance in the Wake of a Viking-Type Entry Vehicle from Mach 2 to 2.5, AIAA Atmospheric Flight Mechanics Conference and Exhibit, AIAA 2008-6217, Honolulu, Hawaii, 2008. 9) Huckins, E. K., III, and Poole, L. R.: Method for Estimating Minimum Required Ejection Velocity for Parachute Deployment, Fig. 12. Parachute motion and velocity estimated with the movies by NASA TN D-6300, 1971. high-speed camera (line) and video camera (dot). 10) Matsuyama, S., Takayanagi, H., Fujita, K., Mitsuo, K., Watanabe, M. and Nishijima, H.: Numerical Investigation on RCS Jet References Interactions for a Mars Entry Vehicle, 32nd AIAA Applied Aerodynamics Conference, AIAA 2014-2692, Atlanta, Georgia, 2014 1) Fujita, K., Ishigami, G., Ogawa, N., Oyama, A., Yamada, K., Kubota, T., Miyamoto, H. and Satoh, T.: Design Study of 11) Yamada, K., Abe, T., Suzuki, K., Imamura, O., Akita, D. and Mars EDL Demonstrator for MELOS mission, 29th International MAAC research and development group: Reentry Demonstration Symposium on Space Technology and Science, Nagoya Congress Plan of Flare-type Membrane Aeroshell for Atmospheric Entry Center, Nagoya, Aichi, Japan, 2013. Vehicle using a Sounding Rocket, 21st AIAA Aerodynamic 2) Maynard, J. D.: Aerodynamics Characteristics of Parachutes at Decelerator Systems Technology Conference and Seminar, AIAA Mach Number 1.6 to 3.0, NASA TN D-752 (1961). 2011-2521, Dublin, Ireland, 2011. 3) Murrow, H. N. and McFall Jr., J. C.: Some Test Results from the NASA Planetary Entry Parachute Program, Journal of Spacecraft

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