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Venus Entry Options
Venus Upper Atmosphere Investigations Science and Technical Interchange Meeting (STIM) January 24, 2013 at the Ohio Aerospace Institute
Peter Gage, Gary Allen, Dinesh Prabhu, Ethiraj Venkatapathy
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Characteristics of the Entry Problem
• Entry velocity
– Driven by interplanetary trajectory
• Entry angle
– Must be high enough to avoid skip-out
– Affects latitude that can be reached
• Ballistic coefficient
– Design choice, constrained by packaging
• Heating rate
– Constrains material selection
• Heat load
– Drives thermal protection thickness
• Deceleration
– Drives payload structural requirements
ADEPT/NASA Distribution Only 2
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TPS Mass Scales with Heat Load
September 14, 2012 ADEPT/NASA Distribution Only 3
From Laub and Venkatapathy
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Entry Environments for Previous Missions
September 14, 2012 ADEPT/NASA Distribution Only 4
P-V Large Probe
Venera 4, 5, 6
Venera/Vega
b = 600
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Entry Performance
Entry Vehicle Class
Ballistic Coefficient
Entry Angle
Peak deceleration (g’s)
Peak heat flux (kW/cm2)
Total heat load (kJ/cm2)
TPS mass fraction (%)
Venera 600 -70 435 14 23.6 >23
Vega 400 -18 140 3.4 19.5 23
Pioneer Large
200 -32 265 3.2 9.9 13
ADEPT 50 -9 45 0.4 8.5 ~12 (estimated)
September 14, 2012 ADEPT/NASA Distribution Only 5
All cases assume V=11.2 km/s
Cases are representative, not matching actual mission conditions
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Venus Entry: Time to Mach 1
ADEPT/NASA Distribution Only 6
0
50
100
150
200
250
0 50 100 150 200
Alt
itu
de
(km
)
Time (s)
ADEPT
Pioneer Large
Vega
Venera
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Adaptive Deployable Entry and Placement Technology
May 15, 2012 ADEPT/CA250/NASA Distribution Only 7
ADEPT-VITaL Key Facts
Launch Vehicle Atlas V 551
Launch Date 29 May 2023
Entry Date 29 September 2024
Entry Flight Path Angle -8.25º
Entry Velocity 10.8 km/s
Entry Azimuth Angle 171.0º
Peak G-load (nominal) 30 G
Peak G-load (3s) 46 G
Atlas V 551
Launch
ADEPT remains
stowed during
Interplanetary cruise;
Deployment at Venus
Ballistic Entry
(unguided)
6-m Diameter 70º Cone
Landing in Alpha region
Estimated 600 km x 600 km 3s landing
location uncertainty ellipse based on 2000
case POSTII Monte Carlo with uncertainties
in:
Entry Position, Entry FPA, Entry Velocity,
Drag Coefficient, Density, Wind
Subsonic
parachute for
ADEPT separation
and VITaL Lander
release
Alpha Landing
Ellipse
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Any benefit from lifting entry?
September 14, 2012 ADEPT/NASA Distribution Only 8
0
50
100
150
200
250
0 100 200 300 400 500 600
Alt
itu
de
(km
)
Time
L/D=0.2
L/D=0
Ballistic Coefficient
Entry Angle Peak deceleration (g’s)
Peak heat flux (kW/cm2)
Total heat load (kJ/cm2)
ADEPT Ballistic
50 -9 45 0.4 8.5
ADEPT L/D=0.2
50 -9 25 0.35 13.5
Targeting accuracy
Cross range
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Deployment Environment: Venus and Mars
September 14, 2012 ADEPT/NASA Distribution Only 9
UAV design experience from Mars may be relevant for Venus
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Summary
• Vega provides existence proof for entry capability for balloons
– Requires Carbon Phenolic or equivalent
• More mass efficient solutions are available
– Pioneer Venus has similar altitude for M=1 • More mass efficient, higher peak deceleration
– ADEPT decelerates higher, with much lower peak deceleration • Opportunity for unfolding UAVs
• Technology development is in progress
• Lifting entry adds complexity without obvious benefit
September 14, 2012 ADEPT/NASA Distribution Only 10
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BACKUP
September 14, 2012 ADEPT/NASA Distribution Only 11
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Engineering Challenges for High-Speed Atmospheric Entry – Venus Example
• For rigid aeroshell
– Size constrained by launch shroud
– Entry mass constrained by launch vehicle throw capability
– Ballistic coefficient ~ 250 kg/m2
9/14/2011 12
Need material that can sustain 2000
W/cm2
Only Carbon Phenolic is available
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Engineering Challenges for High-Speed Atmospheric Entry – Venus Example
• For rigid aeroshell
– Size constrained by launch shroud
– Entry mass constrained by launch vehicle throw capability
– Ballistic coefficient ~ 250 kg/m2
9/14/2011 13
For a given material,
operating near its heating
rate capability reduces heat
load, which reduces TPS
mass
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Engineering Challenges for High-Speed Atmospheric Entry – Venus Example
• For rigid aeroshell
– Size constrained by launch shroud
– Entry mass constrained by launch vehicle throw capability
– Ballistic coefficient ~ 250 kg/m2
9/14/2011 14
Select entry angle with
favorable balance of
heat rate and heat load
Accept high
deceleration (250 g)
Certify for this load
environment
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Opportunity for High-Speed Atmospheric Entry – Venus Example
9/14/2011 15
Develop a
lower-density
material that
can sustain
2000 W/cm2
Operate at
a lower
ballistic
coefficient
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Opportunity for High-Speed Atmospheric Entry – Venus Example
9/14/2011 16
• Assume ballistic coefficient can be lowered 10 x
A material that
can sustain 200
W/cm2 is now
feasible
Peak deceleration
reduced by an
order of
magnitude