GUIDED AEROCAPTURE AND ENTRY AT VENUS USING
MECHANICALLY DEPLOYED DECELERATORS
S. J. Saikia, H. Saranathan, M. J. Grant, and J. M. Longuski School of Aeronau.cs and Astronau.cs, Purdue University, West Lafaye:e, Indiana 47907-­‐2045, [email protected]
RESULTS WHY VENUS? The 2013 Planetary Science Decadal Survey recommends the Venus In Situ Explorer mission as highest-­‐priority within New Fron.ers class [1]. AlWtude vs. Downrange 200
Venus In Situ Explorer Science Goals [1] q  Understand chemistry, mineralogy, weathering of the Venus’ crust q  Understand history and proper.es of Venus atmosphere and the role of water q  Understand key drivers of atmospheric dynamics and climate q  Understand planetary-­‐scale evidence of past hydrological cycles 140
120
Ballistic
Drag Control
AoA and Bank Angle Control
100
90
100
80
80
0
q  Venera (Russia) and Pioneer-­‐Venus (US): successful missions to survive harsh Venus entry condi.ons q  Employed tradi.onal rigid aeroshell technology (high ballis.c coefficient), Carbon Phenolic (CP) thermal protec.on system (only with flight heritage) 70
0
500 1000 1500 2000 2500 3000 3500
Downrange (km)
DeceleraWon Load g−Load
20
15
10
LOW BALLISTIC COEFFICIENT: MECHANICALLY DEPLOYED DECELERATORS Stagnation Point Convective
2
Heat−Rate (W/cm )
Ballistic
Drag Control
Bank Angle Control
AoA and Bank
Angle Control
AoA, Bank Angle,
and Drag Control
25
Venera 7
200
150
100
q  ADEPT achieves low ballis.c coefficient by mechanically deploying a decelerator surface q  Has four primary subsystems: main body, nose cap, ribs, and struts q  Nose cap is a traditional 70° sphere-cone aeroshell with a base diameter of 3 m q  Ribs provide support to the tensioned 3D-­‐woven carbon cloth (thermal protec.on system) and a pair of struts in turn support each rib: against aerodynamic loads q  Maximum diameter for the ADEPT is 6m and preserves the 70° sphere-­‐cone geometry when fully deployed 80
90
100
110
Altitude (km)
120
0
130
100
120
Altitude (km)
140
75
25
20
15
Ballistic
Drag Control
Bank Angle Control
AoA and Bank
Angle Control
AoA, Bank Angle,
and Drag Control
10
5
0
0
80
Drag Skirt Angle for Drag Control 100
200
300
Time (s)
400
Drag Skirt Deployment Angle (deg.)
ADEPT FOR VENUS IN SITU MISSIONS 12
50
StagnaWon ConvecWve Heat-­‐Load Stagnation Point Convective
2
Heat−Load (kJ/cm )
ADEPT [4]
10
Ballistic
Drag Control
Bank Angle Control
AoA and Bank
Angle Control
AoA, Bank Angle,
and Drag Control
250
5
0
70
4
6
8
Velocity (km/s)
300
30
q  CP: high density and high thermal conduc.vity §  Requirement: Increase heat flux, and lower heat load (shorten dura.on) q  For “ballis.c” entry, steep entry flight path angle has to be selected [3] §  High decelera.on loading (150-­‐500 g’s) §  High heat fluxes (3–17 kW/cm2) q  Carbon Phenolic is in short supply! 2
StagnaWon ConvecWve Heat-­‐Rate 35
m kg
Ballistic Coefficient ( β ) =
ACD m 2
70
65
60
55
50
45
0
500
50
100
150 200
Time (s)
250
300
350
Control Histories for Angle-­‐of-­‐AVack and Bank Angle Control BASELINE MISSION CONCEPT [4] 14
180
12
150
ADEPT CONTROL STRATEGIES [5] 10
Bank Angle (deg.)
VITal [3]
Angle−of−Attack (deg.)
q  VITaL repackaged from rigid aeroshell in to ADEPT Decelerator q  Lander mass of 1050 kg, instruments carried inside a pressurized vessel q  Thermal management system supports 3 hours of opera.on q  Entry mass of 1602 kg: carries the payload from entry interface to subsonic (Mach 0.8 ) parachute deployment at around ~75 km q  Parachute extracts the lander from ADEPT Decelerator q  Lander lands in a Tessera region (study baseline is Ovda Regio, 3.7° E longitude, and , 25.4° S la.tude) carries same instruments as VITaL q  Fulfill the same scien.fic objec.ves as ViTaL q  Bank Angle Control: The vehicles is trimmed at 12.5°. Ver.cal component of the lil vector is controlled by varying bank angle. q  Drag Control: The ADEPT vehicle is trimmed at 0 deg. Angle-­‐of-­‐a:ack. The drag coefficient is varied by controlling the level of deployment of the decelerator system. q  Angle-­‐of-­‐AVack and Bank Angle Control: The aero-­‐
surface is suitably gimbaled to orient the lil vector in the desired direc.on. This translates to a unique combina.on of angle-­‐of-­‐a:ack and bank angle. q  Angle-­‐of-­‐AVack, Drag, and Bank Angle Control: In addi.on to gimbaling the aero-­‐surface, the drag skirt deployment angle is also controlled. 110
Altitude (km)
Altitude (km)
160
CHALLENGES OF ENTRY, DESCENT, AND LANDING IN TO VENUS ATMOSPHERE q  Shallower entry flight angles possible using low ballis.c coefficient (<30 kg/m2) entry system q  To overcome limits of rigid aeroshells due to launch vehicle fairing diameter: in-­‐space deployment of a decelerator system to increase drag-­‐area §  Low ballis.c coefficient q  Adap.ve Deployable Entry and Placement Technology (ADEPT) is a viable mechanically deployed decelerator entry system being developed by NASA 120
Ballistic
Drag Control
Bank Angle Control
AoA and Bank Angle Control
AoA, Bank Angle, and Drag Control
180
Requirements q  Achieving a majority of the above goals represents a New Fron.ers class mission q  Measurements of deep atmospheric gas composi.ons and surface mineralogy require an in situ mission q  Venus Intrepid Tessera Lander (VITaL) concept was evaluated for the 2013 Decadal Survey [2] AlWtude vs. Velocity 8
6
4
90
60
30
2
0
0
120
100
200
Time (s)
300
400
0
0
100
200
Time (s)
300
400
CONCLUSIONS Angle-of-Attack and Bank Angle Control [5]
Drag Control
q  Low-­‐β ADEPT liling and guided entry (in contrast to ballis.c entry) leads to q  further reduc.on in peak decelera.on loads (3–6 g) Vs. 30 g for ADEPT ballis.c entry q  reduc.on in convec.ve heat-­‐flux (<190 W/cm2) Vs. ~300 W/cm2 for ADEPT ballis.c entry q  Integrated stagna.on-­‐point heat-­‐load increases because of increase in .me of flight q  Drag control (β), angle-­‐of-­‐a:ack (α), and bank angle (σ) and combina.on thereof used as control strategies q  β-­‐α-­‐σ control strategy results in least peak g-­‐load q  Mechanism for gimbaling the decelerator system involves minimal addi.onal structural elements q  Introduc.on of β-­‐control will require addi.onal control elements (increase in mass) REFERENCES: [1] Squyres, S., et al. (2011), NAP Press, pp. 111-132. [2] Gilmore M. S. et al. (2010) NASA [3] Dutta S. et al. (2012) IEEE AC,
10.1109 [4] Smith B. et al. (2013) IEEE 978-1-4673 [5] Venkatapathy E. (2011) AIAA 2011-2608.