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National Aeronautics and Space Administration Concept for a Lunar Power and Communications Utility Presented to Future In-Space Operations Working Group.

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Presentation on theme: "National Aeronautics and Space Administration Concept for a Lunar Power and Communications Utility Presented to Future In-Space Operations Working Group."— Presentation transcript:

1 National Aeronautics and Space Administration Concept for a Lunar Power and Communications Utility Presented to Future In-Space Operations Working Group Jim Schier, Chief Architect, Space Communications and Navigation Human Exploration and Operations Mission Directorate October 14, 2015

2 Developing the Moon Requires Utilities Two infrastructure or utility systems needed for service to lunar landers, rovers, & bases are: Communications –Direct To Earth (DTE) communications possible on the near side –What about communications to the poles & far side, e.g., South Pole Aitken Basin? Power –Solar power during lunar day is straight forward –How do you survive the night? 2

3 Communication Relays 3 Sample Relay Orbit: 12-Hour Frozen Orbits 8 hour/orbit useful SMA= 6142.4 km Eccentricity=0.59999 Inclination=57.7° Perilune Argument=90° 2 Relays in same plane 180° phased Continuous regional coverage including one pole 2 Relays in orthogonal planes Partial global coverage including both poles Provide far side coverage & polar coverage limited by lunar libration (83-90°latitude) Save surface systems 40+ dB over DTE Provide store & forward and NavSat services Spectrum use compatible with radio astronomy

4 Power Transmission RF transmission is not practical for small antennas on fairly long links However, laser transmission may be practical due to narrow beamwidth If practical, power transmission from lunar orbit has several advantages: –Reduces downmass to lunar surface –Avoids need for nuclear power –Able to start service with small capacity & scale up as demand grows –Able to provide wide geographic coverage with small number of assets Revisit rate (Coverage) vs. transmission efficiency (path loss) is a major trade yet to be done to design the best orbit 4

5 Lunar Power & Relay Utility, Inc. Lunar orbiting utility satellites offer potential benefits to surface elements –Communication relays provide support especially in regions where Direct To Earth service is limited or non-existent –Power transmission provides support to survive the lunar night A Power & Relay Utility consortium could be a profitable adjunct to developing the Moon –Strategy is to allocate functions to orbit that effectively reduce cost on the surface –Three revenue streams mitigate risks of a single service –All 3 services can reduce the cost of surface systems providing incentives for a utility consortium –Scalable architecture enables start-up with limited investment Coupled architecture of orbiting & surface systems drives need for standardizing the interfaces Power User does not have to match technology level of Provider 5

6 6 NASA’s Lunar Quest Program ILN Agency Steering Group James Green, Planetary Science Division NASA Science Mission Directorate james.green@nasa.gov March 13, 2009 6

7 7 Lunar Quest Program - Selected Highlights  Planetary Science Division’s Lunar Quest Program Robotic missions to accomplish key scientific objectives Provide a complementary Research and Analysis program including the NASA Lunar Science Institute Provide useful data to Exploration Systems and Space Operations mission directorates for returning humans to the Moon  Lunar Reconnaissance Orbiter (LRO) Exploration Mission: 1-year operations Planetary Science Division: for ~2-year science mission follow-on  NASA’s delivery of four landed payloads (Anchor Nodes) as part of the International Lunar Network (ILN) First US robotic lunar landers since 1968! A Science Definition Team was formed to begin thinking about what NASA could do for the ILN in line with National Academy Reports

8 8 Objective Instrument 1. Understand the current seismic state and determine the internal structure of the Moon Three axis broadband seismometer 2. Measure heat flow to characterize the temperature structure of the lunar interior Temperature and thermal conductivity measurements to depths > 3 m 3. Use electromagnetic sounding to measure the conductivity structure of the lunar interior Electromagnetic Sounding Experiment 4. Determine deep lunar structure by installing next-generation laser ranging capability Laser ranging experiment SDT - Anchor Node Science Objectives & Baseline Instruments  “4 nodes is the minimum number to accurately locate a shallow moonquake anywhere on the lunar surface; 2 is the minimum to investigate the lunar core” -- from ILN Science Definition Team (SDT) Jan 2009 report  Strong science desire for far-side placement. Due to dependency upon communications satellite, SDT also identified suitable nearside sites.

9 9 Anchor Node Trade Results Summary  Science Driver: seismic stations must simultaneously and continuously operate for sufficient time to receive enough signals 6 years for 4 nodes/shallow moonquakes 2 years for 2 nodes/deep moonquakes  Power: Solar Arrays vs. Radioisotope Power System (RPS) Alternative concept studies indicate RPS would be required to meet continuous operation requirement within desired lander/LV sizing  Launch Vehicle Accommodations: Given RPS, then, at this time, only Atlas V can accommodate  If Atlas V, then Fly Four Landers on One Flight Operations issues Budget issues  Communication will be an issue for any far side nodes

10 10 Conclusions & Current Baseline  Baseline US Anchor Nodes Concept: 6 year lifetime & 4 nodes Will require a Small RPS (~60 We) Launch 4 nodes on one Atlas V Complete SDT science package on all landers Will landing in daylight and operating on nearside with direct com to Earth satisfy science requirements? Are the poles potential seismic sites? ·Need seismic simulations studies to verify  Anchor Nodes Schedule Plan: 2009 May/June: Mission Concept Review - objectives, feasibility, & cost 2009 Summer: Detail architecture & start of Phase A (to refine design) ·Risk reduction tests/activities ·Lander testbed demo (June) ·Propulsion thruster testing (July) Early 2010: Start of Phase B (detailed design for implementation)

11 International Lunar Network (ILN) Communications Working Group (WG2) Final Report for Study Period: June 2008 to January 2009 13 March 2009

12 12 Key Study Conclusions Organizations coordinating international space communications acknowledge ILN’s needs and are prepared to continue collaboration to ensure the success of ILN. No major spectrum issues were identified Scenarios for interoperable ILN comms were included in “Recommendations on a Strategy for Space Internetworking” which was approved by the IOAG and IOP Preliminary ILN operations concepts & scenarios are consistent with CCSDS standards –Evaluation of specific standards & options is needed to confirm that interoperability is feasible for all ILN partners. The desire to capture information from all the nodes over a full lunar cycle (6 years) drives the need to operate a lunar-orbiting communications relay for 6-10 years –Relay would enable improved science (including other missions) & provide additional benefits to the ILN by reducing the communication payload requirements of the nodes and associated missions. –Multiple agencies have an interest in implementing a lunar relay and there are cost benefits of a multi-agency partnership for implementing such a lunar relay. While near-side nodes could transmit their data directly to Earth at low data rates (kbps), a relay in a Low Lunar Orbit (LLO) making short passes would force far- side nodes to store ~175 MB and transmit at medium rates (up to 5 Mbps).

13 International Coordinating Bodies for Interoperability & Cross Support 13 International Standard Services Space Internetworking Optical Link Strategy Common Mission Operations Strategy Lunar-Mars Spectrum Coordination Group (LMSCG) Defines Moon & Mars Spectrum for SFCG

14 National Aeronautics and Space Administration International Lunar Network: Power Beaming Options Jim Schier to WG4 Technologies ILN Meeting, Yokohama 12 March 2009 14

15 National Aeronautics and Space Administration 15 RF Power Beaming to Lunar Surface Viability Study Bryan Welch, RHA Dr. Jeff Wilson, RHE March 5, 2009

16 National Aeronautics and Space Administration 16 100 km Orbital Altitude Orbital Altitude (km)100 Frequency (GHz)326094 Max Slant Range (km)368.0056 Tx Gain (dBi)6.75E+017.30E+017.69E+01 Beam Width (rad)0.0010580.0005640.00036 Beam Spot Diameter (m)389.2967207.6249132.5265 Rx Power (W)195 Number of Rectenna Elements ( )80424282743693977 Rectenna Gain (dBi)52.9135658.3736262.27315 Collection Efficiency ( )1.48E-055.22E-050.000128 Free Space Path Loss (dB)-173.862-179.322-183.221 Tx Power (W)8.31E+126.73E+111.12E+11 Input Power (W)2.08E+131.68E+122.79E+11

17 National Aeronautics and Space Administration 17 Two Power Beaming Spacecraft, 24 hr coverage using 3000 km altitude 39° inclined Frozen orbits Two spacecraft provide >30% coverage of entire moon, assuming 10° above horizon or better –Landers will require pointable power receiver arrays –Frozen orbits minimize stationkeeping propellant Red area denotes sun view-ability View Percentage

18 National Aeronautics and Space Administration 18 Laser Powered ILN Lander Use solid, monochromatic laser-tuned solar cells –Laser flux (assume 1 sun) –Or Solar flux Charge battery with laser flux View Times for each lander: 2 hours per day Solar panel pointed to beaming spacecraft or sun –Need pointable array to access beaming spacecraft and maximize power input –2-axis gimbal (down to 10° above horizon) Strawman results –Estimated Mass comparable to RPS design Need pointable solar array and acquisition system (laser reflectors?) But two power beaming spacecraft reqiured Issues/Risks –Lander –Solar Cell TRL level Need a single junction version of an existing triple junction design –Impact of monochromatic laser at 1 sun flux on lander –Accumulated Dust on solar panels –Solar panel gimbal vibration impact on seismic science Lifetime (dust) –Gimbal temperature during lunar night (are heaters needed) Need pointable solar array and acquisition system

19 National Aeronautics and Space Administration 19 Power Beaming Satellite Strawman 12 kW laser, continuous (6 year lifetime) –2 m mirror ‘telescope’ –25% efficient Power –Two Ultraflex arrays –Batteries only for housekeeping survival Thermal –Large, pointable 9 kW radiators (from telescope) –Thermal expansion on telescope platform GN&C: –Hubble Accuracy (~0.07 arcsec) with fast slewing (27 arcsec/s +/- 0.01 arcsec/s) –CMGs for spacecraft, inertial pointing –Fine pointing platform for Laser (thermal removal issues!) Propulsion: Monoprop or biprop Communications –S-band science relay ~6-8 kbps –1-m dish; Bent-pipe C&DH –Intensive support of GN&C Mechanical –Structure vibrations impact pointing accuracy/jitter Radiator 30 m 2 High accuracy pointing platform 2 m, 3 kW (output) laser Solar Array 7 m diameter Solar Array 7 m diameter

20 National Aeronautics and Space Administration 20 Power Beaming Feasibility Summary Microwave: Not feasible –Required Antennas / power level too large Laser: Feasible –Minimal impact on ILN nodes Pointable solar array with laser-tuned solar cells – mass ~= RPS –20kW class power beaming spacecraft if Hubble class pointing with slewing can be achieved and sufficient laser TRL & lifetime can be developed Can be re-used as relay platform >$500M for two spacecraft (ROM estimate) Pointing, Acquisition & Tracking validated by Lunar Laser Communication Demonstration (LLCD) on LADEE in 2013

21 LaserMotive, Inc. 2012 Fact Sheet 21 “Successful prototype of 10kW high efficiency rectenna for wireless power for electric trucks”, Author: brian wang on 7/12/2012 http://nextbigfuture.com/2012/07/successful-prototype-of-10kw-high.html

22 National Aeronautics and Space Administration Backup Assumptions for RF and Laser power beaming options 22

23 Lunar Vicinity Frequency Plan Summary Report of 3rd Meeting of SFCG, Lunar/Martian Spectrum Coordination Group 3 April 2008 23 BandForwardAgencyReturnAgencyNotes Operational direct from/to Earth S-Band2025-2110 MHzAll2200-2290 MHz 5 All X-band7190-7235 MHz Roskosmos ESA ISRO JAXA CNSA 8450-8500 1 MHz Roskosmos ESA ISRO JAXA CNSA Ka-Band22.55-23.55 2 GHz NASA DLR a 25.5-27 GHz 3 NASA DLR JAXA b a Narrowband Ranging b Downlink only beyond 2018 Lunar Relay Trunk Line Ka-Band40-40.5 GHzNASA37-38 GHz 7 NASA Lunar relay to/from Orbiter or Surface; Orbiter to/from Surface; Orbiter to Orbiter UHF435-450 MHz 4 JAXA ISRO 390-405 MHz 4 JAXA ISRO S-Band2025-2110 MHz NASA JAXA 2200-2290 MHz 5 NASA JAXA Ka-Band 22.55-23.55 MHz NASA25.5-27 GHz 3 NASA Surface to Surface 6 UHF410 - 420 MHzNASA410 - 420 MHzNASAUnder study IEEE 802868 - 915 MHz, 2.4 GHzNASA868 - 915 MHz, 2.4 GHzNASAUnder study Lunar Relay to Lunar relay Cross link Ka-Band 37-38 7 GHz NASA 40-40.5 7 GHz NASAReverse Band Ka-Band 22.55-23.55 GHz DLR 25.25-27.5 GHz DLR Under study for sub- satellite ISL Ku-Band13.75-14 GHzDLR14.5-15.35 GHzDLR Under study for sub- satellite ISL Used by many. Agreed. Interoperability possible. Used by many. Agreed. Interoperability potential. Discussion on sharing the band. Used by one agency (no interoperability discussion needed at this stage). Agreed. Still to be discussed.

24 ILN Scenario D: Two Agencies Via Relay Common Proximity & Relay Links 24 SA1 Surface Station SA2 Lunar Relay Satellite Proximity Link Relay Link Forwards data SA1 Surface Station SA2 Lunar Relay Satellite Proximity Link Relay Link Forwards data 1 2 SA1 Ground Station SA1 Mission Operations Center SA1 Ground Station SA1 Mission Operations Center Bilateral Proximity & Relay Link interoperability required Relay stores data Surface station may store data till Relay acquired 1.Real-time: SA2 LRS has simultaneous LOS to Surface & Ground Stations –SA1 surface station uses proximity link to SA2 relay satellite which forwards data to SA1 ground station –SA1 ground station transmits data via terrestrial network to SA1 Mission Operations Center 2.Store & forward: SA2 LRS has sequential LOS to Surface & Ground Stations –SA1 surface station uses proximity link to SA2 relay satellite which stores data –SA2 relay satellite forwards data to SA1 ground station –SA1 ground station transmits data via terrestrial network to SA1 Mission Operations Center

25 National Aeronautics and Space Administration 25 RF Power Beaming Assumptions Required Rx Power (W)150 Rx Power Margin (%)30 Half Power Efficiency ( )0.5 RF-DC Conversion Efficiency ( )0.7 Rx Rectenna Efficiency ( )0.5 Rectenna Diameter (m)1.5 Rectenna Element Gain (dBi)6.87 Rectenna Element Spacing (λ)0.5 Tx Antenna Efficiency ( )0.5 Tx Antenna Diameter (m)10 Tx Power Efficiency ( )0.4

26 National Aeronautics and Space Administration 26 Summary Methodology of beaming energy to the lunar surface via RF technology is not a viable option at this time. At the RF wavelengths considered, beam footprint is too large for the 10m large aperture inflatable transmit antenna, meaning that a large portion of the transmit power is not collected Compensation of increasing the transmit power is not a viable option, as Ka-band space qualified klystrons have a 1kW limit –1MW magnetrons and klystrons are available at 5.8 GHz, but required power is even higher at that frequency than at 32 GHz due to expanded beam footprint Additional trades have also been performed, but also provides non- viable options: –Inflatable receiver platform that feeds a simple rectenna provides an order of magnitude reduction in transmit power –Unfoldable rectenna that can enlarge the receive size also provides an order of magnitude reduction in transmit power

27 National Aeronautics and Space Administration 27 Laser Option Assumptions (Jeff Landis, Dave Wolford) Laser power beaming for lunar network satellite: Back of the envelope calculations. Laser efficiencies are improving, but for the lasers currently available, an efficiency of 25% is a reasonable value to assume. (50% is possible, but not really available off the shelf) Photovoltaic conversion of laser power can be done at an efficiency of 50%. Not accounting for other efficiencies in the chain, 12.5 % of the power input to the laser can be converted to output power at the solar array bus. This number must be multiplied by the fraction of the laser power which is intercepted by the photovoltaic array. The fundamental diffraction limit to spot size at a distance d is r_spot = 0.61 d /r_lens d distance in meters  wavelength in meters r_lens radius of the lens or mirror on the beaming station that directs the output of the laser, in meters. Assume = 0.5 micrometers = 5E-7 meters Assume r_lens = 1 meter (i.e., 2 meter diameter telescope on the satellite) r_spot (in meters) = (0.61)( 5E-7)*d(in meters) = 3 E-7* d(m) = 3 E-4* d(km) For an 8000 km beaming distance, spot radius is 2.44 meters, and spot area is 18.7m 2

28 National Aeronautics and Space Administration 28 Laser Option Assumptions (cont.) Conversely, if the maximum spot diameter is desired to be two meters (radius 1 meter), then the maximum beaming distance is 3280 km (directly overhead). We want: 20 W on the ground =120 watts assuming 4 hrs per day (beam shared by 6 ground stations) =150 watts required assuming 80% battery round-trip efficiency At a beam intensity of 1 kW/m2 (about one sun intensity), 150 watts requires only.3 square meters of solar array area. This fills roughly 10% of the one-meter radius beam spot. To get this 150 watts, from the spot-fill-fraction times the efficiency numbers above, you will need 12 kW of power to the laser. This will need 9 kW of heat rejection. (Note that this has omitted a large number of real-world losses in the chain). Pointing required is 1 meter over a 3,000,000 meter distance = (1/3) of a micro- radian. Multiply by 180/pi = 2E-5 degrees = 70 milli-arc seconds For reference, the Hubble telescope Coarse Track Mode was designed to maintain pointing error to within 20 milli-arc seconds (rms, and the Fine Mode was designed to maintain FGS pointing error to less than 3 milli-arc seconds (rms).

29 National Aeronautics and Space Administration Characteristics of Frozen Orbits 29 “Relay Coverage Studies For The International Lunar Network”, Charles H. Lee & Lynette Zamora, California State University, Fullerton, James Schier, NASA

30 National Aeronautics and Space Administration Characteristics of Frozen Orbits 30 “Relay Coverage Studies For The International Lunar Network”, Charles H. Lee & Lynette Zamora, California State University, Fullerton, James Schier, NASA

31 LaserMotive, Inc. 2012 Fact Sheet 31


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