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Solar Sail Mission Applications and Future Advancement 20 - 22 July 2010 Malcolm Macdonald The.

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Presentation on theme: "Solar Sail Mission Applications and Future Advancement 20 - 22 July 2010 Malcolm Macdonald The."— Presentation transcript:

1 Solar Sail Mission Applications and Future Advancement 20 - 22 July 2010 Malcolm Macdonald The Second International Symposium On Solar Sailing The New York City College of Technology of the City University of New York, Brooklyn, New York, U.S.A. & Colin M c Innes

2 Introduction Photons perturb spacecraft by conservation of momentum Solar sailing uses the perturbation to reduce propellant mass Momentum carried by individual photons is extremely small Requires large reflector to provide a useful momentum transfer 20 - 22 July 2010Malcolm Macdonald2

3 Absence of reaction mass makes solar sailing romantic  Romanticism ≠ Realism Proponents have traditionally seen solar sailing as a technical nirvana i.e. the complete solution Difficulty in advancing low TRL concepts often underestimated Romanticism 20 - 22 July 2010Malcolm Macdonald3 Worm Hole Space Art

4 Solar Sail Mission Catalogue Diverse range of mission applications have been proposed Must identify the concepts which are truly enabled Or, significantly enhanced Enables development of an application-pull technology development roadmap 20 - 22 July 20104Malcolm Macdonald

5 Solar Sail Mission Catalogue Mission catalogue considers wide range of mission concepts Allows definition of key characteristics of enabled/enhanced missions Critical missions act as facilitators to later missions Application-pull technology development roadmap is thus established 20 - 22 July 20105Malcolm Macdonald

6  Planet-Centred...and other Short Orbit Period Applications  Highly Non-Keplerian Orbits  Inner Solar System Rendezvous  Outer Solar System Rendezvous  Outer Solar System Flyby  Solar Missions  Beyond Neptune 20 - 22 July 20106Malcolm Macdonald Mission Categories

7 Planet-Centred...and other Short Orbit Period Applications Trajectory design largely restricted to escape manoeuvres Or, relatively simplistic orbit manoeuvring such as lunar fly-by’s Significant technology demands on the solar sail Optimal energy gain requires sail be rotated 180 degrees once per orbit and then rapidly reset  Other simplistic orbit manoeuvres require similarly agile sail technology 20 - 22 July 20107Malcolm Macdonald

8 Planet-Centred...and other Short Orbit Period Applications Requirement for an agile sail is a significant disadvantage Two applications identified which don’t require an agile sail GeoSail and Mercury Sun-Synchronous Orbiter Use a fixed attitude to independently vary a single orbit parameter creating a non-inertial orbit 20 - 22 July 20108Malcolm Macdonald

9 Highly Non-Keplerian Orbits Requires small, continuous acceleration in a fixed direction Displace the spacecraft to artificial equilibrium point A location some distance from a natural libration point 20 - 22 July 20109Malcolm Macdonald

10 Highly Non-Keplerian Orbits Continuous thrusting lends well to solar sailing romanticism  Two primary applications have been proposed Polesitter and Geostorm Use fixed attitude sail to provide continuous thrust 20 - 22 July 201010Malcolm Macdonald

11 20 - 22 July 201011Malcolm Macdonald Approximate UK-DMC FOV The view from a Polesitter...

12 20 - 22 July 201012Malcolm Macdonald Approximate Landsat-7 Enhanced Thematic Mapper Plus FOV The view from a Polesitter...

13 20 - 22 July 201013Malcolm Macdonald The view from a Polesitter... Approximate Deep Space Climate Observatory Scripps-EPIC FOV

14 Inner Solar System Rendezvous Sample return to the inner planets discussed extensively Perceived as high-energy and therefore good for solar sailing Low-Thrust rendezvous requires v ∞ ≈ 0 at target body Transfer is thus significantly increased True for bodies which are “easy” to get to, i.e. Mars, Venus Once captured into a bound orbit typically require an agile sail 20 - 22 July 201014Malcolm Macdonald

15 Inner Solar System Rendezvous Mars Sample Return  “grab & go” optimal for solar sailing 5 – 6 year mission v’s ~2 years for equivalent chemical mission Venus Sample Return  Similar to MRS but with increased launch mass sensitivity 1000 m 2 sail for sample return leg offers potential launch cost saving Mercury and Small Body Sample Return  Truly high-energy transfer trajectories Only low-thrust propulsion systems offer viable mission concepts Solar sailing offering potential benefits  Small Body missions do not typically require an agile sail 20 - 22 July 201015Malcolm Macdonald

16 Outer Solar System Rendezvous Low-Thrust rendezvous requires low v ∞ at target body  Now even more difficult to “slow-down” with a solar sail  Can use gravity assists at large moons to capture Following capture, all orbit manoeuvres are slow Consider Europa,  Deep inside Jupiter gravity-well Long duration  Deep inside Jupiter’s intense radiation belts Significant shielding required 20 - 22 July 201016Malcolm Macdonald

17 Outer Solar System Flyby 20 - 22 July 201017Malcolm Macdonald Removes requirement for low v ∞ at target body  Consider a Jupiter trajectory

18 Outer Solar System Flyby Jupiter atmospheric probe mission was considered  Chemical propulsion was concluded to still be superior Due to mass and number of probes required sail was very large  As target moves further from Sun, solar sail propulsion becomes increasingly beneficial Leading to a peak in benefits for missions beyond Neptune 20 - 22 July 201018Malcolm Macdonald

19 Solar Missions Ulysses used Jupiter gravity assist to pass over solar poles Orbit is highly elliptical; pole revisit time of approximately 6 years ESA’s Cosmic Visions mission concept Solar Orbiter Maximum inclination of order 35 deg using SEP Mid-term sail could deliver spacecraft to solar polar orbit in ~5yrs SPO is an example of type of high-energy, inner-solar system mission which is enabled by solar sail propulsion 20 - 22 July 201019Malcolm Macdonald

20 Beyond Neptune Significant benefit to missions beyond Neptune For either a Kuiper Belt or Interstellar Heliopause mission  Destinations beyond the Heliopause are challenging for solar sailing alone 20 - 22 July 201020Malcolm Macdonald EventTime LaunchT0 Aphelion passageT0 + 1.5 yrs Perihelion passageT0 + 2.8 yrs Sail Jettison (@5 AU)T0 + 3.2 yrs Kuiper Belt Transit (40 – 55 AU)T0 + 5.7 – 8.3 yrs 100 AUT0 + 12.9 yrs 200 AUT0 + 23.2 yrs

21 Key Characteristics Reducing launch mass does not directly reduce mission cost  Launch cost is only reduced if the reduced launch mass allows a smaller launch vehicle to be used  Saving 10 – 20 M€ launch costs is 2 – 4 % total cost reduction Is that a good cost/risk ratio for the project?  Reduction must be a significant percentage of mission total Can sub-divide all solar sail missions into two classes  Class One Solar sail is used to reach a high-energy target, after which the sail is jettisoned by the spacecraft  Class Two Uses continuous thrust to maintain an otherwise unsustainable observation outpost 20 - 22 July 201021Malcolm Macdonald

22 Venus escape at end of sample return mission Mercury and high-energy small body Sample Return missions Outer solar system planet fly-by Oort Cloud Key Characteristics 20 - 22 July 201022Malcolm Macdonald Non-Inertial Orbits such as GeoSail or a Mercury Sun-Synchronous Orbiter Highly Non-Keplerian Orbits such as Geostorm and Polesitter Kuiper-Belt fly-through Solar Polar Orbiter Interstellar Heliopause Probe Planetary escape at start of mission Mars missions Outer solar system rendezvous and centred trajectories Loiter at the Gravitational Lens Enabled or Significantly Enhance Marginal benefitNo benefit

23 Key Characteristics Positive Characteristic Very High Energy transfer trajectory Inner Solar System Highly Non-Keplerian and Non-Inertial orbits Final stage in a multi-stage system Fly-by beyond the orbit of Neptune 20 - 22 July 201023Malcolm Macdonald Negative Characteristic Mars and Venus rendezvous Outer Solar System rendezvous Short orbit period with rapid slew manoeuvres High radiation environment High pointing stability required Required to rendezvous with a passive body Fly-by beyond solar gravitational lens

24 Key Missions GeoSail  Earth-centred, non-inertial orbit  ~40 m square sail, at an assembly loading of ~35 g m -2 To provide heritage to later missions, the design is required to be more demanding than considered in isolation Solar Polar Orbiter  Close solar mission, rapid polar revist  ~150 m square sail, at an assembly loading of ~8 g m -2 Sail slew rate of 10 deg per day required Interstellar Heliopause Probe  200 AU in ~15 – 25 years  ~150+ m disc sail, at an assembly loading of ~2 g m -2 20 - 22 July 201024Malcolm Macdonald

25 Application Pull... The culmination of any technology roadmap must be enabled by previous milestones  IHP requires a sail architecture with low assembly loading 20 - 22 July 201025Malcolm Macdonald

26 20 - 22 July 201026Malcolm Macdonald...Technology Development Route Current applications are clustered about the mid to far term IKAROS Design point @ 200 m 2 & 75 gm -2

27 Future Advancement Roadmap Current applications are clustered about the mid to far term  To much risk in attempting to directly jump to, say, SPO Initial flight tests must provide confidence in the technology and a clear path towards some enabling capability JAXA sounding rocket deployments an excellent example of this Risk was spread across several tests and led to IKAROS 20 - 22 July 201027Malcolm Macdonald

28 Future Advancement Roadmap Requirement exists to backfill the roadmap  Either develop new mission concepts, or  Re-engineer the mission concepts and the vision of the future of solar sailing Removing the gap between near and mid-term applications 20 - 22 July 201028Malcolm Macdonald

29 Advancement Degree of Difficulty Consider the concept of Advancement Degree of Difficulty AD2 categorises risk, from 0 – 100 %  Consider system level engineering risk of solar sailing The programmatic risk of an advanced technology demonstrator is found to be, at best, acceptable And, dual development approaches should be pursued to increase confidence  The AD2 of solar sailing must be reduced 20 - 22 July 201029Malcolm Macdonald

30 Future Advancement Roadmap Romanticism ≠ Realism  Spacecraft engineering realism seeks to evolve technology Consider solar sail propulsion as a spectrum of advancement 20 - 22 July 201030Malcolm Macdonald Secondary propulsion Perturbation Primary propulsion Requires reaction mass to counteract Attitude control systems Traditional solar sail vision Now

31 31Malcolm Macdonald Future Advancement Roadmap Solar sailing for attitude control is well established Used on many GEO spacecraft – often called a “trim tab” Used by Mariner 10 and MESSENGER spacecraft Used by Hayabusa 20 - 22 July 2010

32 Future Advancement Roadmap Solar sailing is a mature technology  Programmatic risk in advanced solar sailing can be reduced by hybridising the propulsion Mariner 10 & MESSENGER both used a small kite  No reason why other inner solar system missions would not similarly benefit  Missions could be primarily SEP, with a secondary sail  Can incrementally balance and then switch this AD2 is thus significantly reduced 20 - 22 July 201032Malcolm Macdonald

33 Future Advancement Roadmap Hybridisation of solar sail mission with SEP can significantly enhance the mission 20 - 22 July 201033Malcolm Macdonald

34 Future Advancement Roadmap Hybridisation of solar sail mission with SEP can significantly enhance the mission  Consider a hybrid sail/SEP Geostorm variant A 45-m square sail, at an assembly loading of ~45 g m -2 Storm warning time is doubled! 20 - 22 July 201034Malcolm Macdonald

35 Future Advancement Roadmap  May not need sails >50 – 100 m 20 - 22 July 201035Malcolm Macdonald IKAROS Design point @ 200 m 2 & 75 gm -2

36, or search “Advanced Space Concepts” in iTunes

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