Aerocapture Technology - 123SeminarsOnly

Aerocapture Technology
www.nasa.gov
Dr. Thomas Spilker
Planetary Scientist / Engineer, Jet Propulsion Laboratory / Caltech
Michelle M. Munk
In-Space Propulsion Aerocapture Manager, NASA-Langley Research Center
Decadal Survey Steering Committee Meeting | February 22, 2010
1

Introduction to Aerocapture
Mission Benefits / Missions Enabled
Current Status of Aerocapture
Plan and Costs to Flight
Outline
2

Atmospheric
Drag
Reduces Orbit
Period
Hyperbolic
Approach
Aerobraking
Orbit
Insertion
Burn
Aerobraking vs Aerocapture
Many Passes
Through Upper
Atmosphere
Entry
targeting
burn
Periapsis
raise
maneuver
(propulsive)
Aerocapture
Jettison
Aeroshell
Energy
dissipation/
Autonomous
guidance
Target
orbit
Aerocapture: A vehicle uses active
control to autonomously guide itself
to an atmospheric exit target,
establishing a final, low orbit about a
body in a single atmospheric pass.
3

The !V necessary to slow from a
hyperbolic approach trajectory to a
useful science orbit is
!V = V phyp - V circ
The rocket equation shows why
aerocapture is so advantageous,
masswise:
For a propulsive capture, the mass
increases exponentially with the !V;
for aerocapture, the mass of the
aeroshell is linear with !V.
The Aerocapture Advantage
Examples for Circular Orbit Insertion
Mars
Titan
Venus
Neptune
Saturn
4

Aerocapture’s Advantages to Science
• Advantage: greater delivered mass into orbit at the
destination
• It’s all about mass – more mass yields better science
• More instruments, or higher-performance instruments
• More mass for higher-performance subsystems that support the
science
• Power – for the instruments, and other support subsystems
• Telecommunications – to downlink larger data volumes
• Propulsion – to get the spacecraft to locations it wouldn’t access
otherwise
• Onboard data storage
• Etc…
• Structure – to hold all this together
• Advantage: reduced trip times to distant destinations
• Spend less time in the cruise phase, more in the science phase
• Stay within the lifetimes of lifetime-limited components
5

Sample Aerocapture Benefits for Robotic Missions
Mission - Science Orbit
Nominal
Orbit
Insertion
!V, km/s
Best A/C
Mass, kg
Best
non-A/C
Mass, kg
A/C %
Increase
Launch
Vehicle
Decrease?
Venus V1 - 300 km circ 4.6 5078 2834 79 Yes
Venus V2 - 8500 x 300 km 3.3 5078 3542 43 Yes
Mars M1 - 300 km circ 2.4 5232 4556 15 No
Mars M2 - ~1 Sol ellipse 1.2 5232 4983 5 No
Jupiter J1 - 2000 km circ 17.0 2262

Titan Aerocapture Systems Study Concept
“Titan Explorer”-type mission based on SSE
Roadmap circa 2001 – direct Titan orbit
Detailed analysis by multi-Center team of
discipline experts (many published refs)
Using Aerocapture and SEP,
• fit on smaller launch vehicle
• cut trip time in half
versus a chemical mission.
2.4 m diameter HGA
3.75 m diameter
Aeroshell
Ref: “Aerocapture Systems Analysis for a Titan Mission”, NASA TM 2006-214273, March 2006.
Lander
Orbiter
SEP Prop
Module
Solar
Arrays
7

Characterizing Atmospheric Uncertainties
Variability We Can Model (season, latitude, etc.)
Measurement Uncertainty (Big improvement for Titan after Huygens/Cassini)
Residual Uncertainty (Monte-Carlo-modeled waves, turbulence, etc.)
Neptune
Titan
Titan
Mars
Earth
0 10 20 30 40 50 60 70
Variation, % of Mean
Post Cassini / Huygens
Density Variation, % of Mean (at Aerocapture altitudes)
• Residual uncertainty about the same for Mars and Titan; higher for Neptune
• Titan’s overall variation roughly same as Earth, after Cassini/Huygens
8

Trajectory Simulations Include Realistic Global
Reference Atmosphere Models
Global Reference Atmosphere
Models (GRAM)
• Provides atmosphere parameters
(density, pressure, temperature)
vs. altitude, latitude, longitude,
season, and time of day
• Earth GRAM used for Space
Shuttle, Genesis, Stardust
• Mars GRAM used for Pathfinder,
MER, MGS, Odyssey, MRO, MSL
• Titan, Neptune, Venus GRAM
modeled using same approach
as Mars GRAM
• Titan GRAM profiles validated
against Cassini/Huygens
measurements
Models include variability and
random perturbations for Monte
Carlo trajectory analysis
• Includes uncertainties in current
estimates derived from scientific
measurements
• Includes perturbations based on
models of dynamic processes
2000 Perturbed Density Profiles
from Mars GRAM
Aerobraking Altitudes
Aerocapture
Altitudes
9

Titan-GRAM Model vs Cassini-Huygens Data
Aerocapture
min alt
Aerocapture Minimum Alt Range Aerocapture to Orbit Alt Range
Titan-GRAM conservatively bounds the density observations
from HASI and INMS
Ref.: Justh and Justus, “Comparisons of Huygens Entry Data and Titan Remote Sensing Observations with the
Titan Global Reference Atmospheric Model (Titan-GRAM)”
10

!
!
!
!
!
!
!
Titan Aerocapture Technologies - Ready!
Enabling Technologies - No new enabling technology required
Strongly Enhancing Technologies
Aeroheating methods development, validation
• Large uncertainties existed at time of analysis, further work and Cassini data all but
eliminated
TPS Material Testing
• TPS materials were not tested against then-expected radiative heating at Titan;
testing was done AND radiative environment reduced significantly in models
Atmosphere Modeling
• Model validated against Cassini/Huygens data
Enhancing Technologies
Aeroshell lightweight structures - reduced aerocapture mass
Guidance - Existing guidance algorithms have been demonstrated to
provide acceptable performance, improvements could provide
increased robustness
Simulation - Huygens trajectory reconstruction, statistics and modeling
upgrades
Mass properties/structures tool - systems analysis capability
improvement, concept trades
11

300 x 300 km
Aerocapture Benefit for a Venus Mission
1165 kg Launch Vehicle Capability
Delta 2925H-10, C3 = 8.3 km 2 /s 2
Into 300 x 300 km Venus orbit with same launch vehicle, Aerocapture delivers:
• 1.8x more mass into orbit than aerobraking
• 6.2x more mass into orbit than all chemical
Reference: “Systems Analysis for a Venus Aerocapture Mission”, NASA TM 2006-214291, April 2006
Mass savings will
scale up for
Flagship-class
mission
Venus Orbiter
(OML Design Only)
Ø 2.65 m
12

Example Monte Carlo Simulation Results:
Venus Aerocapture
100%
successful
capture
97.7% !V performed
by Aerocapture
13

Neptune Orbiter Aerocapture System Concept
Mass margin provides opportunity for
• Third probe
• Increased aeroshell size for possible reduction in
aeroheating rates/loads, TPS thickness
requirements, surface recession
Propulsive mission is too massive for Delta IV-H
Aerocapture is ENABLING
Orbiter
2.88 m Length
Flattened Ellipsled
Aeroshell
2 Probes
Orbiter
Reference: “Systems Analysis for a Neptune Aerocapture Mission”, NASA TM 2006-214300, May 2006
35% Dry
Margin at
Orbiter and
SEP Level
5m Fairing
Solar
arrays
SEP Prop
Module
14

Total Heat Load (kJ/cm 2 )
1.6
1.4
1.2
1.0
.8
.6
.4
.2
0
Neptune Aerocapture Challenges: Aeroheating, TPS
Zone 4
(includes
base)
Low
Zone 2
2.88 m
Zone 2 – Wind
TPS Sizing
Radiative
Convective
Ref
Med
Zone 3
High
Outside of
Expected Range
Zone 1
~0.74 m
16
14
12
10
8
6
4
2
0
Total Peak Heat Rate (kW/cm 2 )
• TPS developments and interfaces
will require a significant effort
• No facility exists for testing these
heating levels, or the combined
convective/radiative environment
• Manufacturing and shape change
due to recession is challenging
• New aerodynamic shape
Total Heat Load (kJ/cm 2 )
4.0
3.5
3.0
2.5
2.0
1.5
1.0
.5
0
Zone 1 – Nose
TPS Sizing
Radiative
Convective
Low
Ref
Med
High
Outside of
Expected Range
40
35
30
25
20
15
10
5
0
Total Peak Heat Rate
(kW/cm2 )
15

Top-Level Aerocapture Infusion Roadmap
In-Space Propulsion Technology
(2002+)
Systems Analysis
Technology Development
Aeroshells and TPS
Aerothermal Models
Guidance, Navigation and Control
Instrumentation
Additional development:
Aerothermal
TPS/test facilities
Aerodynamics
Structures/manufacturing
Earth Orbit Flight
Test (2015)
Inner Planet/OP Satellite
Aerocapture Missions (2018+)
(Low L/D, modest TPS needs)
Mars Titan
Venus
Additional development:
Aerothermal
TPS/test facilities
Aerodynamics
Structures/manufacturing
Giant Planet Aerocapture Missions (2025+)
(High L/D, substantial TPS needs)
Jupiter Saturn Uranus Neptune

ISPT’s Low-Risk Aeroshell Mass Improvements
Warm Structure System Model - based on MER, MPF, validated with testing
For environments up to 300 W/cm2 HT-424
for adhesive
Aluminum
honeycomb
MER SLA-561V System 250 deg C
Areal Density = 2.07 lb/ft 2 Areal Density = 1.78 lb/ft 2
Genesis Carbon-Carbon
Warm Structure SLA-561V System 316 deg C
Hot Structure System Model - based on Genesis, validated with testing
For environments up to 700 W/cm2 Final System included
backup aluminum
Honeycomb structure
Modified RS9
for adhesive
Graphite polycyanate
honeycomb
Final System includes
11-layer MLI
and high-temp coating
Hot Structure
Carbon-Carbon/Calcarb
Areal Density = 3.65 lb/ft 2 Areal Density = 2.50 lb/ft 2
14%
Improvement
31%
Improvement
17

Aeroshell Manufacture and Test with Ablator
Family System
ARA Material Density Heating Range New Missions Features
SRAM-17 0.27 g/cm 2 115 – 210 W/cm 2 Titan, Mars Robust Char
SRAM-20 0.32 g/cm 2 140 – 260 W/cm 2 Earth Acap, Mars Low Recession
PhenCarb-20 0.32 g/cm 2 200 – 500 W/cm 2 Large Mars, EEV High Heating
PhenCarb-32 0.51 g/cm 2 500 – 1,100 W/cm 2 EEV, Venus, Neptune Severe Heating
1-m SRAM-20 aeroshell test at Solar Tower
18

Power
Supply
Command &
Telemetry
Processing
Main
Simulation
Processor
Simulation I/O
Cards for IMU
& Thrusters
GN&C Flight Testbed is Complete
Spacecraft Computer with MOAB
Card (Broad Reach Engineering)
Command & Telemetry
Workstation
19

Status of Aerocapture Technology
• ISPT has made major strides in ground-based
development over the past 8 years
• GN&C Hardware-in-the-Loop Testbed (guidance coded in flight
software)
• Lighter, more robust structural and TPS concepts matured through
arcjet, structural, and environmental testing and model validation,
culminating in two 2-meter and larger aeroshell manufacturing
demonstrations
• Aerothermal and Atmospheric models greatly matured (better
prediction capability)
• High-fidelity statistical simulation capability applied to several
destinations (same tool used for operational planetary entry
missions)
• Stoplight chart on next page show summary of “readiness”
of each subsystem for key destinations
20

Destination
Subsystem
Atmosphere
Goal: Capture Physics
Aerodynamics
Goal: Errors ! 2%
GN&C
Goal: Robust
performance for 4-6
DOF simulations
TPS
Goal: Reduce SOA by
30%+, expand TPS
choices
Structures
Goal: Reduce SOA
mass by 25%
Aerothermal
Goal: Models match
within 15%
System
Goal: Robust
performance with
ready technology
Venus-GRAM (2004)
based on world-wide
VIRA.
Heritage shape, well
understood aerodynamics
CA =±3%, CN =±5%,
" TRIM =±2%
APC algorithm captures
96% of corridor
More testing needed on
efficient mid-density TPS.
Combined convective
and radiative facility
needed.
High-temp systems will
reduce mass by 31%.
Convective models
match within 20% laminar,
45% with turbulence.
Radiative models agree
within 50%
Accomplishes 97.7% of
!V to achieve 300 x 300
km orbit.
Aerocapture Technology Subsystem
Readiness
Venus Earth Mars Titan Neptune
Earth-GRAM (1974)
validated by Space Shuttle
Heritage shape, well
understood aerodynamics
CA =±3%, CN =±5%,
" TRIM =±2%
Small delivery errors. APC
algorithm captures 97% of
corridor
Technology ready for ST9.
LMA hot structure ready for
arrivals > 10.5 km/s.
High-temp systems will
reduce mass by 14%-30%.
Environment fairly wellknown
from Apollo, Shuttle.
Models match within 15%
Accomplishes 97.2% of !V
to achieve 300 x 130 km
orbit. No known
technology gaps.
Mars-GRAM (1988)
continuously updated with
latest mission data.
Heritage shape, well
understood aerodynamics
CA =±3%, CN =±5%,
" TRIM =±2%
Small delivery errors using
!DOR. APC algorithm
captures 99% of corridor
ISPT investments have
provided more materials
ready for application to
slow arrivals, and new
ones for faster entries.
High-temp systems will
reduce mass by 14%-
30%.
Convective models agree
within 15%. Radiative:
predict models will agree
within 50% where radiation is
a factor.
Accomplishes 97.8% of
!V to achieve 1400 x 165
km orbit. No known
technology gaps.
Titan-GRAM (2002) based on
Yelle atmosp. Accepted
worldwide to be updated with
Cassini-Huygens data
Heritage shape, well
understood aerodynamics
CA =±3%, CN =±5%,
" TRIM =±2%
Ephemeris accuracy
improved by Cassini-
Huygens. APC algorithm
captures 98% of corridor
ISPT investments have
provided more materials
ready for application.
High-temp systems will
reduce mass by 14%-30%.
Convective models agree
within 15%. Radiative no
longer a concern.
Accomplishes 95.8% of
!V to achieve 1700 x 1700
km orbit. No known
technology gaps.
Ready for Infusion Some Investment Needed Significant Investment Needed
Neptune-GRAM (2003)
developed from Voyager,
other observations
New shape; aerodynamics
to be established.
CA =±8%, CN =±8%,
" TRIM =±10%
APC algorithm with "
control captures 95% of
corridor.
Zoned approach for
mass efficiency. Needs
more investment.
Complex shape, large
scale. Extraction
difficult.
Conditions cannot be
duplicated on Earth in
existing facilities. More
work on models
needed.
Accomplishes 96.9% of
!V to achieve Triton
observ. orbit. ENABLING
21

Status of Aerocapture Technology (cont’d.)
• Aerocapture is ready for either flight validation or mission
implementation, except at Outer Planets
• The community is somewhat divided on the need for a flight validation
before mission infusion
• The experts in the technical fields who understand the system say, “It’s
ready to fly!”
• The scientists/mission managers/proposal reviewers say, “It’s too risky!”
• We have not yet been in a situation where Aerocapture enabled a key
Roadmap mission. For small, competed missions, the perceived risk
and cost have eliminated Aerocapture early on. The Discovery AO
may remedy this—remains to be seen.
• We do have a consensus: The proper flight validation will reduce
the risk for the first user, and will add Aerocapture to the tool set for
those small missions who can’t afford to be the first user.
• We will also continue education and advocacy, to make the user
community more comfortable with Aerocapture and its benefits.
22

Resource Estimates for Aerocapture
Validation
• NASA’s Chief Engineer requested an Issue Paper in June of 2009,
to identify this cross-cutting technology as a gap in the current
NASA budget
• Was put on hold due to expectations of new technology program
• Basis of Estimate:
• NMP ST9 with margin for inflation and schedule lengthening (40 mo)
• Phased with 60/40 beta curve
• Includes post-flight analysis at higher level than ST9
• Launch vehicle costs not included
• 30% margin is included
• This represents a heavily-instrumented vehicle with a new thermal
protection system; some reductions could be realized
If this validation reduces the launch vehicle class of just one mission,
we’ve recovered our investment.
For information purposes only. Pre-decisional.
23

Top-Level Aerocapture Infusion Roadmap
In-Space Propulsion Technology
(2002+)
Systems Analysis
Technology Development
Aeroshells and TPS
Aerothermal Models
Guidance, Navigation and Control
Instrumentation
Additional development:
Aerothermal
TPS/test facilities
Aerodynamics
Structures/manufacturing
$30-50M
$100-150M
(no LV)
Earth Orbit Flight
Test (2015)
Inner Planet/OP Satellite
Aerocapture Missions (2018+)
(Low L/D, modest TPS needs)
Mars Titan
Venus
Additional development:
Aerothermal
TPS/test facilities
Aerodynamics
Structures/manufacturing
Giant Planet Aerocapture Missions (2025+)
(High L/D, substantial TPS needs)
Jupiter Saturn Uranus Neptune

Aerocapture Development Summary
• Aerocapture is enabling or strongly enhancing
for many of the destinations in the Solar System,
saving launch mass, trip time, and cost.
• Aerocapture is ready for flight infusion or
validation.
• A flight validation at Earth, immediately
applicable to inner planets and outer planet
satellites, would cost $100-150M, excluding
launch vehicle.
• Additional ground testing for application to giant
planets would be $30-50M.
• A flight validation would lower first-user cost
and risk. If applicable missions will be on the
Planetary Science Roadmap, we need advocacy
for a flight validation.
• Including entry system experts in mission studies
and review boards could improve risk
perception.
25