Automatic Transfer Vehicle ATV Reentry Safety Trajectory ... - Congrex

Control Division, TEC-ECM
Automatic Transfer Vehicle ATV
Reentry Safety Trajectory Analysis
with ASTOS
Guillermo Ortega, Tomaso Sgobba, Antoine Bavandi, Sven Weikert, Francesco
Cremaschi
3rd IAASS Conference, October 21st-23rd, 2008

Presentation guide
ATV and ATV re-entry
Trajectory re-entry safety analysis
ASTOS a re-entry tool
Way Forward
Conclusions
2

Time-line of ATV re-entry analysis
ESA-CNES task force on ATV re-entry safety ends April
2007: risk analysis starts
Mission analysis update in Autumn 2007
Re-entry safety analysis ends February 2008
Safety analyses of controlled and uncontrolled reentry
trajectories as well as the calculation of
debris survivability and the estimation of risk
probability
Re-entry scheduled for Autumn 2008
3

ATV
Automatic Transfer Vehicle
build by EADS for ESA
Operated by CNES
Used to resupply ISS and
raise its apogee
Launched by Ariane-5
Automatic not autonomous
Named “Jules Verne”
4

ATV Re-entry scenario: CNES mission analysis
2nd ORBIT
ΔV1
ΔV2
DEPARTURE FROM
ISS ORBIT
1st ORBIT
5

Risk assessment: roles and responsibilities, ESTEC part only
ATV Reentry
Safety
Review
Panel
(RSRP)
Request for
analysis
ATV Ground
segment ESA
ESA’s Technical
Directorate TEC
ATV Project
manager
Request for
analysis
ATV Ground
segment
CNES
6

ESTEC Analysis
Assess ATV disposal cargo list w.r.t. their contribution to the surviving
fragments list in the case of an uncontrolled re-entry
Compute trajectories and their corresponding casualty and fatality
probability:
controlled re-entry with explosion without demise
controlled re-entry with explosion with demise
controlled re-entry without explosion with demise
uncontrolled re-entry with explosion with demise
uncontrolled re-entry without explosion with demise
7

Failure Cases Considered
[300;300] ORBIT, 100% FUEL LOAD
[460;460] ORBIT, 10% FUEL LOAD (NOMINAL)
UNREALISTIC FAILURES
8

Nominal Re-entry Trajectory by CNES
10-2
FOOTPRINT
10-5
FOOTPRINT
SPOUA
9

ATV re-entry
10

ATV interior view
Composed of 2
main parts:
Spacecraft
subassembly
Integrated cargo
carrier
4 solar arrays
skewed about 45
deg
a S-band antenna
mast mounted
11

ATV rear 3D view
Main propulsion system composed
of a set of thrusters
12

ATV front 3D view
Composed of the docking
mechanism
Attitude control thrusters
Rendezvous sensing system
13

Size comparison
14

ATV model 3D views
15

ATV Docking Mechanism
16

ASTOS: AeroSpace Trajectory Optimization Software
ASTOS is an
optimization
environment to
compute optimal
trajectories
(launchers reentry)
Use Non-Linear
Programming
(NLP)
mathematical
solvers
Developed in
WinXP, Solaris,
Linux, MAC OS X
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Inputs to safety analysis
Initial boundary constraints
Path constraints
Orbital
constraints
Path constraints
Vehicle features
Planetary
environment
conditions
Final boundary constraints
18

Trajectory Safety Analysis: HOWTO
Input data
Entry Analysis Safety Analysis
ASTOS
Risk Assessment Analysis
RAM
DARS, DIA
19

DARS, DIA, and RAM modules
2D, 3D Visualization
and Reporting
ASTOS
RAM
DARS DIA
DARS (Debris Analysis Re-entry Spacecraft) calculates the stage re-entry considering break-up
and demise
DIA (Debris Impact Analysis) calculates the impact based on ballistic coefficients
RAM (Risk Analysis Module) calculates the risk probabilities of human casualties and fatalities
20

DARS, DIA, RAM modules of ASTOS
DIA is based on
ballistic coefficients
and allows safety
analysis in combination
with additional
impulses during the
break-up already in
early project phases
RAM is used to
compute the risk to the
population on-ground
DARS, DIA, RAM are
modules of ASTOS
and are fully integrated
in the ASTOS GUI
21

RAM (Risk Analysis Module for ASTOS)
RAM calculates the casualty cross-section (Ccs) of a re-entry
object
Ccc is computed using the the cross-section of all surviving
objects and an average projected cross section of a human
body
The probability of casualty is determined using this casualty
cross-section, the impact probability, and a population density
distribution map
The risk to the population on-ground is determined by
integrating the probability over a terrain area with underlying
population density
Plots in 2D and 3D are available
22

ATV cargo list used for ESTEC analysis
23

ECM Trajectory Risk Analysis
Parameter Distribution Dispersion
Impulse duration Gaussian Mean=1383.4 s, 3sigma = 35%
Thrust level Uniform [-5.4% ; 13.2%]
Thrust pitch angle Gaussian 3sigma = 1.72°
Atmosphere density Uniform [-50% ; 50%]
Altitude of explosion Gaussian mean=75 km, 3sigma=6km
Fragments ejection direction Uniform uniform dispersion in 3D space
21x10 6 trajectories run
First deorbitation maneuver is not
dispersed
ASTOS’s bach mode tool used to
perform the Monte Carlo simulations
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Footprint with Demise
25

Footprint without Demise
26

3D Projection of DARS results
27

Risk Assessment Comparison: ESA/TEC - ACTA
Initial ESA/TEC Risk
Assessment
ACTA Risk Assessment Updated ESA/TEC Risk
Assessment
November 2007 August 2008 September 2008
- Descending re-entry track (expected
trajectory)
- initial mass of 20.1 t (expected mass)
- 131 surviving fragments (60% of initial
mass)
- Explosion occurs at 75km altitude
+/-2km at 1σ
- Does not consider population sheltering
- Fatality Kinetic Energy Threshold = 32J
- Casualty Area ~ 108 m 2
- Descending re-entry track (expected
trajectory)
- initial mass of 12.4 t (expected mass)
- 214 surviving fragments (25% of initial
mass)
- Explosion at 78km altitude (nominal
case, otherwise between [68 ; 84km])
- Considers population sheltering
- Fatality Kinetic Energy Threshold = 79J
- Casualty Area ~ 205 m 2
- Descending re-entry track (actual
trajectory)
- initial mass of 13.4 t (actual mass)
- 214 surviving fragments from ACTA
(25% of initial mass)
- Explosion at 78km altitude (nominal
case, otherwise between [68 ; 84km])
- Does not consider population sheltering
- Fatality Kinetic Energy Threshold = 32J
- Casualty Area ~ 205 m 2
P F = 2.0×10 -5 P F = 2.4×10 -5 P F = 4.1×10 -5
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Expected Fatality Probabilities comparison: ESA/TEC - ACTA
Type of Scenario ESA/Technical
Directorate
(unsheltered)
ACTA Inc.
(sheltered)
Controlled 0.8×10 -5 0.4×10 -5
Uncontrolled 3.3×10 -5 2.0×10 -5
Total 4,1×10 -5 2.4×10 -5
US Requirement < 3.0×10 -5 < 3.0×10 -5
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Footprint comparison ASTOS-ACTA study
The ASTOS footprint extensions are slightly smaller that in the
ACTA study
in the order of -25 km up-range and 3 Km down-range
The fragments impacts are slightly more outspread
in the order of +20 km up-range and 2 Km down-range
CONCLUSION:
For the nominal controlled scenarios studied in part 2,
ASTOS simulations provide results (10-5 footprint) that
are similar to the ACTA simulations with a variation of
1.6 %
30

Conclusions (I)
First analysis risk assessment performed:
good number of trajectories have been
run with several parameters,
configurations, etc
The assumptions and input data have
been checked with the project/CNES
Analysis shows risk below NASA
standards
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Conclusions (II)
Trajectory risk analysis is not yet a common practice
(even in a voluntary basis)
The re-entry risk analysis process is composed of a
series of steps (procedure) that comprises the use of
software tools to calculate demise and fall down of
debris
The cost of the use (or even imposition in a space
project) of these tools is minimal in comparison with
the liability that would occur in case of disaster
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