Transcript Deflecting APOPHIS with a Flotilla of Solar Sails Jean-Yves Prado Olivier Boisard, Alain Perret,Guy Pignolet U3P France Outlines ■ The case of Apophis ■ Keyholes and resonant orbits ■

Deflecting APOPHIS with a Flotilla
of Solar Sails
Jean-Yves Prado
Olivier Boisard, Alain Perret,Guy Pignolet
U3P
France
Outlines
■ The case of Apophis
■ Keyholes and resonant orbits
■ The Yarkovsky Effect
■ Mitigation mission
■ Comparison with other deflection techniques
ISSS 2010
Deflecting Apophis with a flotilla of solar sails
New York July 20-22
APOPHIS
Discovery
Discovered by:
Roy A. Tucker,
David J. Tholen,
Fabrizio
Bernardi
Discovery date:
June 19, 2004
Orbital characteristics
Aphelion distance:
1.099 AU
Perihelion distance:
0.746 AU
Orbital period:
323.6 d (0.89 year)
Inclination:
3.331°
Physical characteristics
Dimensions:
~250 m (estimated)
Mass:
2×1010 kg
(estimated)
Rotation period ~30h
Mass of APOPHIS ~ 200 x
ISSS 2010
Deflecting Apophis with a flotilla of solar sails
@V=40,000 km/h
New York July 20-22
APOPHIS Fly by of the Earth on April 13, 2029
417 Days =>2037
426 Days =>2036
KEYHOLES
Orbit Uncertainty
+
+ Earth Gravity Assist
asteroid
Earth
ISSS 2010
Deflecting Apophis with a flotilla of solar sails
New York July 20-22
Possible Resonant Orbits
Resonant orbits up to 2130
2037
140
120
2036
426.125 d
Year of return (-2000)
417.43 d
100
80
60
40
20
1s
0
417
419
421
423
APOPHIS Period (Days)
Resonance Condition: Tap=m/n TEarth
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Deflecting Apophis with a flotilla of solar sails
New York July 20-22
425
427
KH distance distribution
‘safe area’
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Deflecting Apophis with a flotilla of solar sails
XX = New
YearYork
– 2KJuly 20-22
The Yarkovsky Effect
1987: Small variations in motion of LAGEOS
explained using Yarkovsky theory
2003: First time measured on an asteroid
GOLEVKA (Chesley)
May 2003
Ivan Osipovich Yarkovsky
1844-1902
From PhD thesis Miroslav Broz, Charles University, Prague 2006
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Deflecting Apophis with a flotilla of solar sails
based on 1991-1999 data
New York July 20-22
The Diurnal Yarkovsky Effect
YE depends on:
Distance to the Sun
Asteroid size
Asteroid shape
Rotation axis obliquity
Rotation rate
Thermal properties:
surface conductivity
thermal inertia
• Very sensitive for the 1 m / 10 km class of Asteroids
• Seasonal effect can be neglected for >100m asteroids
ISSS 2010
Deflecting Apophis with a flotilla of solar sails
New York July 20-22
Impact of the Yarkovsky Effect on the asteroid orbit
■ Tiny effect (10-10 / 10-13m/s2) but permanent
■ Main effect on semimajor axis
■ Order of magnitude for da/dt variation of tens to hundreds meters per year
■ Position error varies with t2
■ Example: with da/dt =10m/year position shifts 100m in 1 year, 400 m in 2 years…
100m
1km
4 km
■ Can be positive (outward spiral) or negative (inward spiral) depending on obliquity
■ Determination of its direction and magnitude for propagating orbit parameters
with an accuracy coherent with keyhole sizes
■ General question, not specific to APOPHIS
ISSS 2010
Deflecting Apophis with a flotilla of solar sails
New York July 20-22
Mission Design
■ A Transfer Module using SEP carries 4 x 200 kg solar sails to be deployed near APOPHIS
■ Formation Flying mode of the sails controlled by the TM
■ The sails hover a few km over the asteroid
■ They can shadow only the surface which is the most effective w.r.t. YE
■ No direct link from the Earth to individual sails
■ Chemical propulsion needed for balancing the photonic pressure (DV ~1.1 m/s/day)
■ Photonic pressure could be decreased by using a mesh instead of a film screen
■ 2 sets of TM+SS required (so 2 launches) can be required for efficiency and reliability
ISSS 2010
Deflecting Apophis with a flotilla of solar sails
New York July 20-22
Cruise
■ High DV needed => Use of solar electric propulsion
■ Soyouz Fregat launch from Kourou assumed
■ Typical mission profiles
2016 option
2011 option
2019 option
Departure date
Dec. 14, 2011
Mar. 30, 2016
Dec. 5, 2019
Departure conditions
v-inf = 3km/s, dec = -20.4deg
v-inf=3.76 km/s, dec =-40 deg
v-inf = 3km/s, dec = -18.4deg
Launch mass
1200kg
1200 kg
1200kg
Date of the Earth swing-by
Apr. 18, 2013
Characteristics of the swing-by
hp = 78000km, v-inf = 4.38km/s
Date of the rendezvous
Mar. 5, 2014
Dec.22, 2018
Jan. 18, 2022
Total cruise duration
813 days (27 months)
997 days (33 months)
775 days (26 months)
Total Delta-V
1520m/s
1620 m/s
1350m/s
Xenon mass
95kg
100 kg
85kg
Final S/C dry mass
1105kg
ISSS 2010
No Earth Swing-By
Apr. 11, 2021
hp = 60000km, v-inf = 4.50km/s
1100 kg
Deflecting Apophis with a flotilla of solar sails
1115kg
New York July 20-22
2016 Departure
No Earth Swing By
ISSS 2010
Deflecting Apophis with a flotilla of solar sails
New York July 20-22
2019 Departure
ISSS 2010
Deflecting Apophis with a flotilla of solar sails
New York July 20-22
Image Credit Olivier Boisard
ISSS 2010
Deflecting Apophis with a flotilla of solar sails
New York July 20-22
Comparison with Other Deflection Techniques
■ 2 categories: Impulsive/Slow Push Techniques
■ Impulsive techniques can be seen as a preliminar to send weapons in space
■ Slow Push Techniques (from NASA report to US Congress):






Focused Solar
Pulsed Laser
Mass Driver
Gravity Tractor
Asteroid Tug
Enhanced YE
 YES
ISSS 2010
Boil off material using large mirror
Low TRL, complex
Boil off material with a laser
Low TRL
Needs to land, Asteroid characteristics dependant Low TRL
Efficiency in D-5,
High TRL
Needs to land, Asteroid characteristics dependant Low TRL
Heavy, Asteroid characteristics dependant
Low TRL
Efficiency in ~D-1, High TRL but applicable only if YE is present
Deflecting Apophis with a flotilla of solar sails
New York July 20-22
Conclusions
■ Cancelling YE can be an efficient and reliable method for deflecting a NEO < km
■ Effort in such technology would benefit several types of missions
■ Canceling YE for a given period of time, even if not needed for APOPHIS, would validate
the feasibility of the method
■ The required technology is very similar to the one required for solar sailing
■ International coordination required
ISSS 2010
Deflecting Apophis with a flotilla of solar sails
New York July 20-22
APOPHIS in the Egyptian mythology
ISSS 2010
Deflecting Apophis with a flotilla of solar sails
New York July 20-22