alternative strategies for exploring mars and the moons of mars
TRANSCRIPT
GLEX-2012.08.2.2x12575-Presentation Drake, Baker, Hoffman, Landau, Voels
National Aeronautics and Space Administration National Aeronautics and Space Administration
Alternative Strategies for Exploring Mars and the Moons of Mars
Bret G. Drake / NASA Johnson Space Center, USA John D. Baker / Jet Propulsion Laboratory, California Institute of Technology, USA Stephen J. Hoffman, PhD. / Science Applications International Corporation, USA Damon Landau, PhD. / Jet Propulsion Laboratory, California Institute of Technology, USA Stephen A. Voels, PhD. / Science Applications International Corporation, USA
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https://ntrs.nasa.gov/search.jsp?R=20120009026 2019-04-05T01:46:55+00:00Z
GLEX-2012.08.2.2x12575-Presentation Drake, Baker, Hoffman, Landau, Voels
“Set far-reaching exploration milestones. By 2025, begin crewed missions beyond the moon, including sending humans to an asteroid. By the mid-2030s, send humans to orbit Mars and return them safely to Earth”
2010 National Space Policy
“Set far-reaching exploration milestones. By 2025, begin crewed missions beyond the moon, including sending humans to an asteroid. By the mid-2030s, send humans to orbit Mars and return them safely to Earth”
• Recent discussions have focused on the prospect of conducting a human mission to Mars orbit as a validation test prior to the surface mission
• These strategies are drawn from the historical precedence of the Apollo test missions
• Apollo 8 and 10 flew very similar mission profiles to the eventual surface missions
• But this Apollo analogy may not apply for much harder and longer Mars orbital missions
Careful examination of the required capabilities and knowledge needed is necessary to fully understand the key issues and applicability of a human mission to Mars orbit prior to a surface mission
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GLEX-2012.08.2.2x12575-Presentation Drake, Baker, Hoffman, Landau, Voels
Mar
s Moo
n Su
rfac
e (P
hobo
s/De
imos
)
Mission Sequence
Mission Summary
Mar
s Orb
it
Day 1
Mission Site: Phobos / Deimos
Capture into High-Mars Orbit
Deimos: 20,063 km circular 0.9 deg, 1.26 day period
Phobos: 5981 km circular 1 deg, 0.32 day period
Departure Trajectory
• Deimos survey • SEV anchoring
• Test payload anchoring methods. • Collect initial samples
• Science package deployment • Drilling operations
Day 60
SEV 1 + CPS 1
Crew:
• Test EVA procedures & mobility • Test payload anchoring methods.
SEV 2 + CPS 2
Deimos Phobos
HMO: 1-sol 250 x 33,813 km
Assumed Mars Orbit Strategy 1. Capture into a 1-sol parking orbit with proper
plane change to match departure asymptote 2. Leave Mars Transfer Vehicle in 1-sol parking
orbit 3. Prepare for orbital operations 4. Utilize SEV-1 to explore Deimos for 14 days
(1,370-2,770 m/s delta-v required)
5. Utilize SEV-2 to explore Phobos for 14 days (1,700-3,170 m/s delta-v required)
6. Prepare for Mars departure 7. Trans-Earth Injection
Jettison
Jettison
Rescue CPS
Short Stay Mars Vicinity Operations
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GLEX-2012.08.2.2x12575-Presentation Drake, Baker, Hoffman, Landau, Voels
Mars Ballistic Trajectory Classes
EARTH DEPARTURE
MARS ARRIVAL
γ
MARS DEPARTURE
VENUS SWING-BY
SUN
EARTH RETURN EARTH
DEPARTURE
MARS ARRIVAL
γ
MARS DEPARTURE
SUN
EARTH RETURN
Long-Stay Missions (Conjunction) • Variations about the minimum
energy mission • Long-stays at Mars (~500 days)
and long overall duration (900-1000 days)
Short-Stay Missions (Opposition) • Variations of missions with short
Mars surface stays (20-60 days) and may include Venus swing-by
• Total mission duration typically 540-840 days
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GLEX-2012.08.2.2x12575-Presentation Drake, Baker, Hoffman, Landau, Voels
Example Delta-v versus Mission Duration
0
10
20
30
40
50
60
- 200 400 600 800 1,000
Tota
l Del
ta-v
(km
/s)
Total Mission Duration (Days)
Crew Vehicle Total Delta-VOpposition Class - 2033 "Good" Opportunity
20 Day Stay40 Day Stay60 Day Stay80 Day Stay100 Day StayConjunction
Trajectory Set: 27 January 2012
ORBIT ASSUMPTIONSEarth Departure Orbit = 400 X 400 kmMars Arrival Oribt = 250 X 33,813 kmMars Departure Oribt = 250 X 33,813 kmDirect Entry at Earth Return
PLANETARY ARRIVAL ASSUMPTIONSMars Propulsive CaptureCapture Plane: As isDirect Earth Entry @ 13 km/s
Opposition Class “Short-Stay” Conjunction Class “Long-Stay”
Stay Time Varies (550-730 Days)
60-Day One-Way Transits
200-Day One-Way Transits
No Venus Swing-by
0
200
400
600
800
1000
1200
Tota
l Miss
ion
Dura
tion
(Day
s)
Earth Departure Opportunity
Opposition Class (60 Day Stay) MissionsMission Duration
Inbound (130 - 560 d) At Mars (60 - 60 d) Outbound (140 - 530 d)
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GLEX-2012.08.2.2x12575-Presentation Drake, Baker, Hoffman, Landau, Voels 6
Total Crew Mission ∆V Sensitivity Co-planar Trajectories
Mission opportunities (Earth departure date) occur approximately every 26 months
Due to the difference in orbits of both the Earth and Mars, the required trajectories vary for each Earth departure date
Short-stay (opposition) missions demonstrate significantly variation
Less sensitivity occurs for long-stay (conjunction) missions
-
5
10
15
20
200 400 600 800 1,000
Tota
l Miss
ion
Delta
-V (
km/s
)
Total Mission Duration (Days)
202820302033203520372039204120432045
Opposition Class “Short-Stay”
(60 Days at Mars)
Conjunction Class “Long-Stay” (60-200 Day Transits)
Mission Characteristics • LEO: 400 km x 400 km • HMO: 250 km x 33,813 km • Direct Earth Entry: 13 km/s
GLEX-2012.08.2.2x12575-Presentation Drake, Baker, Hoffman, Landau, Voels
TRANSLATING ∆V TO MASS
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GLEX-2012.08.2.2x12575-Presentation Drake, Baker, Hoffman, Landau, Voels
Transportation and Exploration Systems Assumptions
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Multi Purpose Crew Vehicle
• Crew delivery to Earth orbit and high-energy Earth return
• CM inert = 9.8 t
• SM inert = 4.5 t
• SM specific impulse = 328 s
Deep Space Habitat
• Support a crew of 4-6 from 365 – 1100 days
• Mass Range : 28-65 t
• Consumables loaded based on crew size & mission duration
Solar Electric Propulsion
• Low-thrust with solar power
• Spacecraft alpha ~30 kg/kw
• Specific impulse = 1800-4000 s
• Xe tank fraction = 5%
• Total power varies
Space Exploration Vehicle • Primary purpose is for
exploration of the moons
• Crew of 2 for 14 days
• Nominal mass = 6.7 t
• CH4 Stage when needed:
• Stage Fraction: 15%
• Isp: 355 s
Chemical Propulsion Stage
• High-thrust propulsive stage
• Parametric design with each stage optimized
• Zero-boiloff cryo management
• Stage fraction ~ 23%
• Specific impulse = 465 s
Nuclear Electric Propulsion
• Low-thrust with nuclear power
• Spacecraft alpha ~20 kg/kw
• Specific impulse = 1800-4000 s
• Xe tank fraction = 5%
• Total power varies
Mars Landers
• Parametric sizing of entry and landing systems
• Inflatable (HIAD) entry system assumed
• Wet lander mass: 89-113 t
Nuclear Thermal Propulsion • High-thrust nuclear propulsion
• NERVA-derived common core propulsion (20 t core)
• 3 x 111 kN engines
• Specific Impulse = 900 s
• All LH2 fuel with zero boil-off
• Drop tanks @ 27% tank fraction
Space Launch System
• Gross Performance ~ 130 t
• Net Performance ~ 120.4 t
• Performance estimates to negative perigee conditions: (-87 km x 241 km)
GLEX-2012.08.2.2x12575-Presentation Drake, Baker, Hoffman, Landau, Voels
ISS ISS
ISS
Opposition Class Missions Crew Vehicle Mass With 60-Days at Mars
9
0
200
400
600
800
1,000
1,200
0 200 400 600 800 1,000
Tota
l Mas
s in
LEO
(t)
Total Mission Duration (Days)
Nuclear Electric Propulsion
202820302033203520372039204120432045
0
200
400
600
800
1,000
1,200
0 200 400 600 800 1,000
Tota
l Mas
s in
LEO
(t)
Total Mission Duration (Days)
202820302033203520372039204120432045
Nuclear Electric
Nuclear Thermal Chemical
Solar Electric
ISS
GLEX-2012.08.2.2x12575-Presentation Drake, Baker, Hoffman, Landau, Voels
Conjunction Class Missions Crew Vehicle Mass Total Mission Durations Approximately 1,100 Days
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Nuclear Electric
Nuclear Thermal Chemical
Solar Electric
0
200
400
600
800
1,000
1,200
300 400 500 600 700 800
Tota
l Mas
s in
LEO
(t)
Useful Exploration Time at Mars (Days)
202820302033203520372039204120432045
0
200
400
600
800
1,000
1,200
300 400 500 600 700 800
Tota
l Mas
s in
LEO
(t)
Useful Exploration Time at Mars (Days)
Nuclear Thermal Propulsion
202820302033203520372039204120432045
0
200
400
600
800
1,000
1,200
300 400 500 600 700 800
Tota
l Mas
s in
LEO
(t)
Useful Exploration Time at Mars (Days)
Nuclear lectric Propulsion
202820302033203520372039204120432045
0
200
400
600
800
1,000
1,200
300 400 500 600 700 800
Tota
l Mas
s in
LEO
(t)
Useful Exploration Time at Mars (Days)
202820302033203520372039204120432045
ISS ISS
ISS
Nuclear Electric Solar Electric
ISS
GLEX-2012.08.2.2x12575-Presentation Drake, Baker, Hoffman, Landau, Voels
ISS
For the Conjunction Class missions, the stay at Mars can be lengthened to allow faster one-way transits to and from Mars
Practical limits exist, due to the physics of the trajectories
The limits are dependent on the propulsion technology choice
The range of practical transits for the Nuclear Thermal Propulsion depicted here
Transit times also dependent on Earth departure year
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Conjunction Class Missions Crew Vehicle Mass Shortening the One-Way Transit Times – Nuclear Thermal Propulsion
-
200
400
600
800
1,000
1,200
0 50 100 150 200 250 300
Tota
l Mas
s in
LEO
(t)
One-Way Tranist Time (Days)
202820302033203520372039204120432045
GLEX-2012.08.2.2x12575-Presentation Drake, Baker, Hoffman, Landau, Voels
ADDITIONAL MISSION DESIGN CONSIDERATIONS
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GLEX-2012.08.2.2x12575-Presentation Drake, Baker, Hoffman, Landau, Voels
Short Stay Orbital Operations Concept High-Thrust Missions
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Phobos 0.32 day period
Deimos 1.26 day period
MTV Remains in Parking Orbit
1 sol period Inclination Varies
Arrival Trajectory Declination Varies
Arrival Asymptote Declination Varies
Departure Asymptote Declination Varies
Deimos Inclination = 0.9 deg Phobos Inclination = 1.1 deg
Assumed Mars Orbit Strategy 1. Cargo pre-deployed into high-Mars parking orbit 2. Crew captures into high-Mars parking orbit 3. Crew transfer vehicle remains in high-Mars
parking orbit 4. Crew prepares for orbital operations 5. Space Exploration Vehicle #1 used to explore
Deimos for 14 days (1,370-2,770* m/s delta-v required)
6. Space Exploration Vehicle #2 used to explore Phobos for 14 days (1,700-3,170* m/s delta-v required)
7. Prepare for Mars departure 8. Trans-Earth Injection
Departure Trajectory Declination Varies
MTV Remains in Parking Orbit
1 sol period
* These values still under review
GLEX-2012.08.2.2x12575-Presentation Drake, Baker, Hoffman, Landau, Voels
Mars Orbital Missions • Mars orbital missions, including exploration of the moons of
Mars, are conducted entirely in deep-space • Reducing the exposure of the mission crew to the hazards of
deep-space is of prime concern for these missions • Practical considerations (transportation technology and number
of launches) will limit mission durations to not much less than 600 days. Thus, human health issues cannot be obviated by propulsion technology alone
• If there is no true difference between 600 and 900 days from a human health perspective, then long-stay (conjunction class missions) should be used
Mars Surface Missions • Application of short-stay opposition class missions is not so clear • Short-surface stay alone is insufficient to ameliorate the human
health concerns (zero-g and radiation) • It is anticipated, though yet to be confirmed, that the surface
environment of Mars (partial gravity and radiation) may provide sufficient human health mitigation for long-stay missions
• Landing large payloads remains a key challenge for Mars surface missions, both short and long stay
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Key Takeaways