1 JSC Earth Moon Libration Point (L1) Gateway Station – Libration Point Transfer Vehicle Kickstage Disposal Options Presented to the International Conference On Libration Point Orbits and Applications June 10-14, 2002, Parador d’Aiguablava, Girona, Spain G. L. Condon, NASA – Johnson Space Center / EG5, 281-483-8173, [email protected]C. L. Ranieri, NASA – Johnson Space Center S. Wilson, Elgin Software, Inc.
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JSC 1 Earth Moon Libration Point (L1) Gateway Station – Libration Point Transfer Vehicle Kickstage Disposal Options Presented to the International Conference.
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1
JSCEarth Moon Libration Point (L1) Gateway Station –
Libration Point Transfer Vehicle Kickstage Disposal Options
Presented to the International Conference On Libration Point Orbits and Applications
June 10-14, 2002, Parador d’Aiguablava, Girona, Spain
G. L. Condon, NASA – Johnson Space Center / EG5, 281-483-8173, [email protected]. L. Ranieri, NASA – Johnson Space Center
S. Wilson, Elgin Software, Inc.
2
JSCAcknowledgements
• Chris Ranieri* – orbit lifetime analysis• Joey Broome# – STK/Astrogator validation/movie• Sam Wilson+ – software development / analysis• Daniel M. Delwood + – analysis
* JSC Co-op # JSC Engineer + Elgin Software, Inc.
3
JSCOutline
• Introduction
• Expeditionary vs. Evolutionary Missions
• Libration Point Transfer Vehicle (LTV) Kickstage Disposal Options
• Geocentric Orbit Lifetime
• Conclusion
4
JSCIntroduction
The notion of human missions to libration points has been proposed for more than a generation
The Gateway concept supports an Evolutionary vs. Expeditionary approach to exploration …
A human-tended Earth-Moon (EM) libration point (L1) Gateway Station could support an infrastructure expanding human presence beyond low Earth orbit and serve as a staging location for human missions to:– The lunar surface– Mars– Asteroids, comets– Other libration point locations (NGST, TPF)– …
5
JSCExpeditionary vs. Evolutionary
• Single mission or mission set
• Completed mission satisfies mission objectives
• Closed-end missions
Humans to L1
Humans to telescope servicing
Humans to Mars
The The MoonMoon
Near Earth Near Earth AsteroidsAsteroids
SunSun--Earth Earth
Libration Libration PointsPoints
PhobosPhobos / / DeimosDeimos
Mars Orbit
MarsMars
Earth Orbit Earth Orbit OperationsOperations
EarthEarth--Moon Moon
Libration Libration PointsPoints
Humans to Moon
Humans to L1
Humans to telescope servicing
Humans to Mars
The The MoonMoon
Near Earth Near Earth AsteroidsAsteroids
SunSun--Earth Earth
Libration Libration PointsPoints
PhobosPhobos / / DeimosDeimos
Mars Orbit
MarsMars
Earth Orbit Earth Orbit OperationsOperations
EarthEarth--Moon Moon
Libration Libration PointsPoints
Humans to Moon
ApolloSkylabApollo-Soyuz Test
ProjectColumbus’ voyage of
discovery to the new world
ApolloSkylabApollo-Soyuz Test
ProjectColumbus’ voyage of
discovery to the new world
Examples
6
JSCExpeditionary vs. Evolutionary
• Ongoing missions
• Open-end missions on which other missions can build
• Greater initial capital investment
International Space Station program Voyages of Prince Henry the Navigator
of Portugal The man chiefly responsible for
Portugal’s age of exploration
International Space Station program Voyages of Prince Henry the Navigator
of Portugal The man chiefly responsible for
Portugal’s age of exploration
The The MoonMoon
Near Earth Near Earth AsteroidsAsteroids
SunSun--Earth Earth
Libration Libration PointsPoints
PhobosPhobos / / DeimosDeimos
Mars Orbit
MarsMars
EarthEarth--Moon Moon
Libration Libration PointsPoints
Humans (to L1, Moon, Telescope Servicing, and Mars)
Earth Orbit Earth Orbit OperationsOperations
The The MoonMoon
Near Earth Near Earth AsteroidsAsteroids
SunSun--Earth Earth
Libration Libration PointsPoints
PhobosPhobos / / DeimosDeimos
Mars Orbit
MarsMars
EarthEarth--Moon Moon
Libration Libration PointsPoints
Humans (to L1, Moon, Telescope Servicing, and Mars)
Earth Orbit Earth Orbit OperationsOperations
Examples
7
JSC
LTV transfers crew from
Earth orbit to L1 station
L1 Gateway Station
Lunar Lander
Moon
Earth
Libration Point Transfer
Vehicle (LTV)
Lunar Lander transfers crew from L1 station to lunar surface
Earth-Moon L1 – Gateway for Lunar Surface Operations
• Celestial park-n-ride• Close to home
(3-4 days)• Staging to:
– Moon– Sun-Earth L2– Mars– Asteroids – …
Sun-Earth L2
NGST TPF
Near Earth Near Earth AsteroidsAsteroids
MarMarss
8
JSCGateway Operations – LTV Kickstage Disposal
• Ongoing Gateway operations require robust capability for delivery & retrieval of a crew
• Human occupation of the Gateway Station requires a human transfer system in the form of a Libration Point Transfer Vehicle (LTV) designed to ferry the crew between low Earth orbit and the Gateway Station.
A key element of such a system is the proper and safe disposal of the LTV kickstage
9
JSCPurpose
1. Identify concepts concerning the role of humans in libration point space missions
2. Examine mission design considerations for an Earth-Moon libration point (L1) gateway station
3. Assess delta-V (V) cost to retarget Earth-Moon L1 Gateway-bound LTV spacecraft kickstage to a selected disposal destination
10
JSC
LTV KickstageDiverted to Disposal Destination
LTV Kickstage Disposal Options
Options considered for LTV kickstage disposal:1. Lunar Swingby to Heliocentric Orbit (HO)
2. Lunar Vertical Impact (LVI), typifies any lunar impact
3. Direct Return to Remote Ocean Area (DROA)
4. Lunar Swingby to Remote Ocean Area (SROA)
5. Transfer to Long Lifetime Geocentric Orbit (GO)
LTV/KickstageInjection Toward L1 LTV Crew Cab
Continues to L1
LTV / KickstageSeparation
11
JSCMethodology• Evaluation Timeframe - 2006 Mission Year Chosen
– Survey two week period of L1 arrivals yielding max (80.2o) and min (23.0o) plane changes ever possible at L1 for crewed spacecraft
• 28.6o lunar orbit inclination; coplanar departure from 51.6o ISS orbit• Moon goes from perigee to apogee during the chosen 2-week period;
begins and ends on the equator
• Combine max and min plane changes with arrivals at L1 perigee and apogee by looking at both choices of arrival velocity azimuth (northerly and southerly) for every arrival date (requires arbitrary ISS orbit nodes)
Lunar Orbit Inclination
51.6o
28.6o
80.2o
Earth Equator
Earth ParkingOrbit
Moon
Earth
L1(Between Earth
And Moon)
Maximum L1 ArrivalWedge Angle @ Libration
Point Arrival = 80.2o
Earth Equator
Lunar Orbit Inclination= 28.6o (max. ever)
12
JSCMethodology (continued)
• HO, LVI, DROA, SROA, and GO maneuver times designed to minimize V for stage disposal subject to imposed constraints– Solutions considered to be a practical attempt to minimize these
maneuver Vs (e.g.: coplanar kickstage deflection maneuver assumed optimal for some disposal options) and not rigorous global optimizations Analysis
• Analysis Tools– Earth Orbit to Lunar Libration (EOLL) scanner*
• Four-body model– Earth, moon, sun, spacecraft– Jean Meeus's analytic lunar and solar ephemerides
• Overlapped conic split boundary value solutions individually calibrated to multiconic accuracy
– Validation with STK/Astrogator
* Developed and updated by Sam Wilson
13
JSC
Earth Parking Orbit to Earth-Moon L1 V Cost vs. Flight Time
Upper Stage Disposal into Remote Ocean Area------------------------------------------------------------------
Direct entry (No Lunar Swing-by)20 deg Entry Flightpath Angle
240 deg Impact Longitude Spread
V for Northerly Lunar LibrationPoint Arrival Azimuth
V for Southerly Lunar LibrationPoint Arrival Azimuth
Transfer Orbit Inclination w.r.t. Earth-Moon Plane (deg)Northerly Lunar Libration Point Arrival Azimuth
Transfer Orbit Inclination w.r.t. Earth-Moon Plane (deg)Southerly Lunar Libration Point Arrival Azimuth
Tra
nsfe
r O
rbit
Incl
inat
ion
w.r
.t. E
arth
-Moo
n P
lane
(de
g)
Option 3. Direct Return to Remote Ocean Area (DROA)
Moon atPerigee
Moon atApogee
26
JSCOption 3. Direct Return to Remote Ocean Area (DROA)
• Data shown represent best of two solution subtypes– Generally there are two local optima for the location of the
kickstage maneuver point in the earth-to-L1 transfer trajectory, of which the better one was always chosen
• Advantages– Assuming kickstage disposal is not allowed to constrain the
primary mission, this option is one of three (HO,DROA,GO) requiring the lowest V budget that could be found (slightly more than 90 m/s in all three cases)
– Avoidance of close lunar encounter, combined with steep entry over wide areas of empty ocean minimizes criticality of navigation and maneuver execution errors
• Disadvantages– Not appropriate if kickstage contains radioactive or other
hazardous material
27
JSCOption 4. Lunar Swingby to Remote Ocean Area (SROA)
1. Lunar Transfer Vehicle (LTV) spacecraft with Kickstage in
initial 407 x 407 km parking orbit
L1
2. Kickstage injects spacecraft& kickstage onto transfer
trajectory toward L1
4. Jettisoned kickstage performs maneuver to achieve close
encounter with moon
5. Spacecraft arrives at Earth-Moon L1
6. Kickstage passes in front of Moon’s leading limb and
returns to Earth for ocean impact
3. Coast phase;Kickstage jettison
28
JSCOption 4. Lunar Swingby to Remote Ocean Area (SROA)
29
JSCSwing-by Remote Ocean Area (SROA) Transfer V vs. Libration Point Arrival TimeV Cost to Deflect LTV Kickstage from L1 Target to Remote Ocean Area Impact via Lunar Swing-by
V for Northerly Lunar LibrationPoint Arrival Azimuth
V for Southerly Lunar LibrationPoint Arrival Azimuth
Transfer Orbit Inclination w.r.t. Earth-Moon Plane (deg)Northerly Lunar Libration Point Arrival Azimuth
Transfer Orbit Inclination w.r.t. Earth-Moon Plane (deg)Southerly Lunar Libration Point Arrival Azimuth
Tra
nsfe
r O
rbit
Incl
inat
ion
w.r
.t. E
arth
-Moo
n P
lane
(de
g)
* V represents lower bound
Option 4. Lunar Swingby to Remote Ocean Area (SROA)
Moon atPerigee
Moon atApogee
30
JSCOption 4. Lunar Swingby to Remote Ocean Area (SROA)
• Advantages
– None identified
• Disadvantages– This option requires a greater V budget than any other one examined.
• The V values shown are minimum values for impact at an essentially random location.
• The V required for longitude control will be even higher
– Inherent sensitivity of this kind of trajectory is almost certain to require extended lifetime of the control system to perform midcourse corrections before and after perisel passage
31
JSCOption 5. Transfer to Long Lifetime Geocentric Orbit (GO)
1. Lunar Transfer Vehicle (LTV) crew module with Kickstage in
initial 407 x 407 km parking orbit
2. Kickstage injects crew module& kickstage onto transfer
V for Northerly Lunar LibrationPoint Arrival Azimuth
V for Southerly Lunar LibrationPoint Arrival Azimuth
Perigee: 6,600 km Apogee Range: 300,000 - 370,000 km
Transfer Orbit Inclination w.r.t. Earth-Moon Plane (deg)Northerly Lunar Libration Point Arrival Azimuth
Transfer Orbit Inclination w.r.t. Earth-Moon Plane (deg)Southerly Lunar Libration Point Arrival Azimuth
Tra
nsfe
r O
rbit
Incl
inat
ion
w.r
.t. E
arth
-Moo
n P
lane
(de
g)
Option 5. Transfer to Long Lifetime Geocentric Orbit (GO)
Moon atPerigee
Moon atApogee
34
JSCOption 5. Transfer to Long Lifetime Geocentric Orbit (GO)
• Advantages– Preferable to deliberate ocean impact if kickstage carries hazardous material– In 4 of the 22 cases studied, the V requirement for GO disposal (into an orbit
having a perigee altitude of 6600 km and an apogee altitude in the range of 300000 – 370000 km) was less than 12 m/s, which is much lower than that found for any other option considered.
– Assuming the 22 cases represent an unbiased sample of all possible transfers between earth orbit and L1, this implies that a 12 m/s budget would suffice if it were permissable to forgo all but about 20% of the otherwise-available transfer opportunities.
• Disadvantages– More orbital debris in the earth-moon system– The 12 m/s budget described above would increase the average interval between
usable transfers to something like 50 days, as opposed to 10 days if transfer utilization were not allowed to be constrained by the disposal V budget (which would then have to be more than 90 m/s).
– To achieve acceptable orbit lifetime, lunar and solar perturbations may necessitate a higher perigee and/or lower apogees, either of which will increase the required V.
35
JSCHO, LVI, DROA, SROA, GO Transfer Delta-V vs. Libration Point Arrival Time
V Cost to Deflect LTV Kickstage from L1 Target to Disposal Destination
• Spacecraft (kickstage) initial condition – Apogee of LEO to EM L1 transfer orbit – Apogee range: 300,000 km – 371,000 km
– Perigee range: 6600 km – 20,000 km
• 45 test case runs• Results
– 56% of the test cases impacted the Earth within 10 years
– Spacecraft cannot be left on transfer orbit
– Further study to determine safe Apogee and Perigee Ranges
Geocentric Orbit Lifetime
38
JSC
300000
300692
306456
313102
313767
320664
327826
328329
340036
342967
343636
351011
352551
359686
360952
6600
750015000
OrbitLifetime
(yrs)
Apogee (km)Perigee (km)
Lifetime for LTV Placed in Geocentric Orbit (GO)50
40
20
0
-16
LTV Orbit Lifetime
Note: A negative lifetime indicates LTV kickstage experienced either heliocentric departure from the Earth-Moon system or Lunar impact
Note: A negative lifetime indicates LTV kickstage experienced either heliocentric departure from the Earth-Moon system or Lunar impact
45 transfer orbits in sample space
39
JSCSummary
• Recommend Direct Remote Ocean Area impact disposal for cases without hazardous (e.g., radioactive) material on LTV kickstage– Controlled Earth contact
– Relatively small disposal V
– Avoids close encounter with Moon
– Trajectories can be very sensitive to initial conditions (at disposal maneuver)
• V to correct for errors is small
• Recommend Heliocentric Orbit disposal for cases with hazardous material on LTV kickstage– No Earth or Lunar disposal issues (e.g., impact location, debris footprint,
litter)
– Relatively low disposal V cost
– Further study required to determine possibility of re-contact with Earth
JSC
Additional Slides
41
JSCSummary Results SWW:dmd
Earth-to-LL1 Transfer and Upper Stage Disposal DataAll transfers involve coplanar departure from circular earth parking orbit having an altitude of 407 km and an inclination of 51.6 deg
GO,DROA, LVI, HO, and SROA maneuver times selected to minimize delta-v for stage disposal
EarthArr Time RA Decl. Dist. Park Orbit Park Xfr Park Xfr(Nominal) 1000 RAN Epoch Orbit Orbit EOD LPA GO DROA HO SROA Orbit Orbit EOD LPA GO DROA HO SROA2006 Oct deg deg km 2006 Oct RANo iEMP MC MC MC MC MC OC OC OC RANo iEMP MC MC MC MC MC OC OC OC
RA RAN Right Ascension of Ascending Node RANo iEMPEODLPAGO Upper Stage Disposal in "Safe" Geocentric Orbit (6600 km Perigee Alt, 300000 - 370000 km Apogee Alt)DROALVIHOSROAOCMC
LVI: Use none on abort
Upper Stage Disposal in Remote Ocean Area (Direct,20 deg Atmospheric Entry Angle, 240 deg Longitude Spread)
Multi-Conic Trajectory
Upper Stage Disposal on Lunar Surface (Vertical Impact)Upper Stage Disposal in Heliocentric Orbit (via Lunar Swingby)
Overlapped Conic TrajectoryUpper Stage Disposal in Remote Ocean Area (via Lunar Swingby)
Inclination of Xfr Orbit wrt Earth-Moon PlaneRight Ascension of Ascending Node at RAN Epoch
• The spacecraft possesses zero initial position and velocity relative to Earth-Moon L1
• With no station-keeping maneuvers, spacecraft drifts from L1 position
• EM L1 location shifts as the Earth and Moon positions change
– EM L1 Earth distance: 302830 km – 345298 km
• No Earth Impacts found – Either lunar impacts or the s/c uses the lunar gravity to go heliocentric
– Un-discernable pattern (given data sample space)
Earth-Moon L1 - Orbit LifetimeSpacecraft Initially at L1
45
JSCL1 Orbit Lifetime vs. EM L1 Position in Lunar Cycle
Orbit Lifetime and Earth-Moon L1 Distance vs. Days In a Lunar CycleBased on a free-drifting (uncontrolled) spacecraft with initial conditions at the Earth-Moon L1 point
0
20
40
60
80
100
120
0 4 8 12 16 20 24 28 32 36 40
Days
Orb
it L
ife
tim
e (
yrs
)
0
50000
100000
150000
200000
250000
300000
350000
Ea
rth
-Mo
on
L1
Dis
tan
ce
(k
m)
OrbitLifetime
Earth-Moon L1Distance
Moon atPerigee
Moon atApogee
Moon atPerigee
Orbit lifetimes <100 years result in either lunar impact or heliocentric trajectory (via lunar fly-by)No Earth impacts occurred (for these 18 sample propagations)Orbit lifetimes <100 years result in either lunar impact or heliocentric trajectory (via lunar fly-by)No Earth impacts occurred (for these 18 sample propagations)
46
JSC
• Seven Total Earth Impacts• Earth Impact for a case with a Δv as small as
10 m/s
• No discernible pattern to results by either magnitude, direction, or epoch for maneuver
EM L1 Orbit Lifetime w/ Delta-Vs
47
JSCOrbit Lifetime for Spacecraft at L1
Initial V of 10-500 m/s; 360o Range Relative to Initial Velocity
Lifetime Results For Satellite Starting at EM L1
2%
51%
44%
2%
1%
Earth Impact
Lunar
Heliocentric Departure
Earth Impact following Heliocentric Departure
100+ Years in Geocentric Orbit
48
JSCManeuver at Earth-Moon L1 (345,187 km apogee)V = 100 m/s Over 360o Range of Direction
0.618 Years
1.71 Years
100 Years
100 Years
L1 Velocity Direction
100 Years In
Earth Orbit
0.033 years
0.402 years
100 Years
Earth Impact
Lunar Impact
Escape to Heliocentric Orbit
49
JSC
• Further studies to better define safe disposal guidelines for s/c launched to EM L1– Further examine lifetimes for s/c at or near EM
L1 position and velocity– Examine transfers to other disposal orbits,
possibly b/w GEO and EM L1 that are less affected by lunar perturbations
– Write for paper to be possibly presented in Spain on this work
EM L1 Orbit Lifetime – Future Work
50
JSCHuman Presence in Space
• Demonstrated benefit to human presence– Hubble Space
Telescope deploy and repair
– Retrieval of Long Duration Exposure Facility
– Retrieval of Westar and Palapa satellites
51
JSCLibration Point Missions
• Earth-Moon L1– Gateway station
• Sorties to the Moon• Satellite deploy, servicing
– Next Generation Space Telescope– Terrestrial Planet Finder
– Staging area for interplanetary and asteroid missions
• Earth-Moon L2– Robotic relay satellites for backside operations
• Bent pipe communications• Navigation aid
• Sun-Earth L2– Human missions to extend human presence in space
52
JSC
Earth-Moon L1– No lunar departure
injection window
– Reusability
– Protection from failed station-keeping
– Specialized vehicle design
Lunar Mission: Libration Point vs. LOR
Lunar Orbit Rendezvous (LOR)
Shorter mission duration
Lower overall V cost
Fewer critical maneuvers required
Mission Scenario Advantages
53
JSCConsiderations for Human Lunar L1 Missions
• 18 year lunar inclination cycle
• Eccentricity of lunar orbit
• Performance cost versus time
• Frequency of outbound & inbound opportunities
54
JSC18 Year Lunar Inclination Cycle
Earth Equator
Lunar Orbit Inclination
Earth Equator
Lunar Orbit Inclination
Earth Equator
Lunar Orbit Inclination
Earth Equator
Lunar Orbit Inclination
55
JSC18 Year Lunar Inclination Cycle
Lunar OrbitInclination
51.6o 28.6o
23.0o
Earth Equator
Earth ParkingOrbit
Moon
Earth
L1(Between Earth
And Moon)
Minimum L1 ArrivalWedge Angle @ Libration
Point Arrival = 23o
Lunar Orbit Inclination
51.6o
28.6o
80.2o
Earth Equator
Earth ParkingOrbit
Moon
Earth
L1(Between Earth
And Moon)
Maximum L1 ArrivalWedge Angle @ Libration
Point Arrival = 80.2o
Earth Equator
Lunar Orbit Inclination
56
JSCEccentricity of Lunar Orbit
Earth Parking Orbit to Earth-Moon L1 V Cost vs. Flight Time