1. Magnetically Levitated Cable
(MIC) System for Space Applications
James Powell
Plus Ultra Technologies
www.NewWorlds.com
NIAC Phase 1 Fellows Meeting
March 7-8, 2006
Atlanta, Georgia

2. The MIC Concept
|Very large, very strong and rigid MIC structures can be erected in space and on the surfaces of planets and moon’s using high temperature superconducting (HTS) cables
zVery strong magnetic forces (e.g., tons/meter) on a distributed array of HTS cables
zMagnetic forces on HTS cables are restrained by a network of high strength tensile tethers (e.g., Kevlar, Spectra, etc.) to form the MIC structure
zMIC structures can be configured as discs, trusses, loops, etc.
|HTS superconductors are rapidly being commercialized
zCurrent densities of ~100,000 amps/cm2with zero electrical losses
zOnly power input required is to remove heat leaking through thermal insulation – power requirements are very small
|MIC can be launched into space as a very compact, folded bundle of HTS cables and tensile tethers
zOnce in space or on the surface of a planet or moon, energizing the HTS cables with current unfolds the MIC array into its final design configuration
zMIC structures can be kilometers in scale
|Thermal insulation is easier for MIC than for superconducting installations on Earth
zVacuum of space eliminates need to maintain vacuum in Earth (based) thermal

3. MIC Launch and Deployment Sequence |---1000 meters---|

4. MIC Applications In Space

9. Objectives of the Phase 1 MIC Program
|Assess the feasibility and advantages of constructing large structures in space using magnetically inflated cables (MIC)
|Identify and analyze most promising MIC applications
|Evaluate potential high temperature superconductor (HTS) options for MIC and select best one
|Carry out baseline designs of most promising MIC applications and determine performance capabilities
|Layout R&D program to develop and demonstrate MIC feasibility

10. High Temperature Superconductors:
Options and Benefits for MIC
|HTS (High Temperature Superconductors) have the following benefits over LTS (Low Temperature Superconductors)
zMuch less refrigeration power required
zMuch more stable against external thermal and mechanical impulses
zEasier to thermally insulate
zDoes not require liquid Helium coolant
|Can be cooled with liquid Nitrogen or Helium gas
|Can use simple, reliable cryocoolersfor refrigeration
|3 principal HTS options
zMgB2(Magnesium Diboride)
zBSCCO (Bismuth Strontium Calcium Copper Oxide)
zYBCO (Yttrium Barium Copper Oxide)

11. Status of BSCCO Superconductor
|Critical temperature of BSCCO is ~90K
zUseful at 77K (liquid N2temperature) –for higher current density and field capability, lower operating temperatures, e.g., 20 to 50K,may be desirable
zRefrigeration factor very attractive, ~20 Watts(e) per Watt(th)
zExamples of engineering current density (A/cm2) capability (parallel to surface)
T(°K)Self Field1 Tesla2 Tesla3 Tesla
7715,0003,8001,500750
7018,00010,5006,0004,500
6427,00015,00011,0007,500
5037,50029,00022,50018,000
3551,00039,00032,00030,000
2081,00058,00050,00046,000
|Practical BSCCO conductor is commercially produced
z~1000 meter lengths produced
zProducing ~106meters/year (~105kiloampmeters)
zWill soon double capacity for wire production
|Principal limitation is requirement for silver metal matrix –impacts cost and very large scale production capability

13. Status of YBCO Superconductor
|Critical temperature of YBCO superconductor is ~100K
zUseful at 77K (liquid N2temperature –for higher current density
and field capability, lower operating temperatures,
e.g., 20 to 50K, may be desirable
zEngineering current densities of 16,000 A/cm2@ 77K
(self field)
zEngineering current densities of ~50,000 A/cm2@ 26K and 3%
|Present conductor uses single film (0.8 μm) on metal tape substrate
zMulti-layer film conductors under development –potential for much higher engineering current densities
|YBCO conductor is very flexible with minimum bend diameter of 1 inch
|Goal of 300 Km/year production capacity by 2007 with 1000 meter conductor lengths
zNo ultimate limit to production capacity

15. Status of MgB2Superconductors
|Critical temperature of MgB2is 39K
zPractical operating temperature of 15 to 20 K at high current, high field conditions
zPractical temperature for present NbTisuperconductor is 4 to 5 K at high current, high field conditions
zRefrigeration factor, watts(e)/watt(th), is ~100, compared to ~500 for NbTi
|Practical MgB2conductors are being manufactured using multi filament MgB2in Nbwire matrix
z~1000 meter lengths at present for powder in tube (PIT) conductor – will go to 3000 meters lengths in 2006
zλccurrent density in superconductor now at 175,000 Amp/cm2, compared to ~300,000 Amp/cm2for NbTiwill go higher in future
zEngineering current densities (superconductor + metal matrix) now at ~30,000 Amp/cm2–will go higher in future
zCost for large scale production will be below $1 per kiloampmeter
|Production process is simple and inexpensive –materials are cheap and abundant

17. Thermal Leakage into MIC Cable as Function of Insulation Thickness and Local Surface TemperatureThermal Leakage into MIC Cable as Function of Insulation Thickness and Local Surface Temperature02040608010012014023456Insulation Thickness, centimeters Thermal Leak into MIC Cable, watts per kilometer Tsurface = 100 KTsurface = 200 KTsurface = 300 KBasis: Cable diameter = 4 centimeters; cable length = 1 kilometer Insulation thermal conductivity = 0.5 x 10-4 W/MK Superconductor temperature = 20 K

18. Flowsheetfor MIC Cooling and Refrigeration System
From Heat Rejection Radiator
To Heat Rejection Radiator
Coolant PumpMICConductor
Electric PowerCoolant Heat ExchangerCryocooler
Connection to Alternate Cryocooler
Pump
Features of MIC Coolant/Refrigeration System
•Leak in MIC conductor coolant circuit is confined to that circuit –Does not compromise other conductor circuits
•Refrigeration function of failed cryocoolercan be taken over by other cryocoolers–MIC conductor circuit continues to operate
•Reject heat from cryocoolercan be handled by fail-safe multi-heat pipe radiator

19. Refrigeration Power of 1 Km MIC Cable as a Function of Superconductor Temperature, Fractional Carnot Efficiency, and Radiator Temperature05101520251520253035404550Superconductor Temperature, K Refrigeration Input Power, kilowatts(e) Tradiator = 300 K20% Cryocooler EfficiencyTradiator = 400 K20% Cryocooler EfficiencyTradiator = 300 K10% Cryocooler EfficiencyTradiator = 400 K10% Cryocooler EfficiencyBasis: 1 km long MIC cable 400,000 Amp current 4 cm diameter 2 cm thick insulation 200 K average surface temperature400K300K400K300K

21. Illustrative Views of Method 1 for Support of Multiple MIC Conductors on Single MIC Cable Using Central Structural Tube

22. Reliability and Redundancy Features of
MIC Conductor and Cable Systems
Potential Event
Consequence
Action Taken
Effect on MIC Capability
Coolant Tube Leaks
Coolant Leaks Into Space Coolant Flow to Conductor That Leaks
Very Minor Effect–Many other conductors inductively take over current that was carried by the failed sub-conductor
One of MIC Conductors Fails Locally
Current Locally Shifts to Other Conductors Through Aluminum Tube
No Action Taken
No Effect–Full current continues in other conductors and cables
Protective Kevlar Layer Prevents Damage to Sub- Conductor
No Action Taken
No Effect–Full current continues in other conductors and cables
Micro-Meter or Space Debris Strikes Conductor
Very Minor Effect–Many other conductors inductively take over current that was carried by the failed conductor
Protective Layer Fails to Prevent Damage to Conductor
Coolant Flow to Conductor That Fails Automatically Shuts Off
No Effect–Conductor has sufficient thermal inertia to continue operation while new cooler is switched in
Coolant Flow to Some Conductors Stops
Standby Cryocooleris Switched into Replace Failed Unit
CryocoolerFails

23. Examples of Present Large Scale Superconducting Systems
|High energy particle accelerators
zFermi doubleraccelerator/storage ring; 6 kilometers of high field superconducting magnets; operating for >10 years
zLarge HadronCollider; 42 kilometers of high field superconducting magnets, nearing completion in Switzerland
zSuperconducting collider; 76 kilometers of high field superconducting magnets (>10,000 total magnets); started by SSC funding went to International Space Station (ISS)
zAll superconducting magnets in such facilities must operate perfectly, otherwise, facility cannot operate
|Japan Railways superconducting Maglev system in Yamanashi, Japan
z350 mph Maglev vehicles levitated and propelled by superconducting magnets –many thousands of passengers carried
|MRI medical scanners
zSuperconducting magnets operate reliably and accurately in thousands of MRI units around the World

26. MIC Solar Electric Applications
|3 MIC solar electric applications evaluated
z100 KW(e) system @ 3 AU for electric propulsion
z1 MW(e) system @ manned lunar base
z200 MW(e) system @ GEO for power beaming to Earth
|1 MW(e) MIC system @ lunar base selected for further detailed baseline design effort
zHigh priority for first application
zLunar system can lead to other applications
|Specific mass of MIC solar concentrator is < 1 kg/KW(e)
zWith concentration factor of >10 Suns, total system mass is
~1.5 kg/KW(e)
|Lunar base can use multiple MIC solar electric system for reliability and redundancy
zElectric capacity can quickly be increased as size of base grows

27. Nominal cm2 engineering current density in MgB2superconductor2 cm thick multi-layer thermal insulation15,000 psi tensile stress in tethersParameterMIC Solar Electric ApplicationElectricPropulsionLunar BasePower Beamingto EarthUnit output power (1)100 KW(e)1 MW(e)200 MW(e) Solar cell efficiency20%20%20% Distance from Sun (2)3 AU1 AU1 AUConcentrator Area, m2375041708.34 x 105Concentrator diameter, m6973913Length of primary MIC cable, m2172292870MIC primary cable current, kiloamp (3) 250250950Diameter of primary MIC cable, centimeters (4) 2.52.59.5Mass of MIC primary cable, kg43043022,600Mass of tether and mirror surface, kg (5) 37037065,000Other mass (secondary cable, coolant and refrigerationequipment), kg1001005,000Total MIC concentratormass, kg90090092,600Specific mass ofMICconcentrator, kg/KW(e) 90.90.46Nominal Design Parameters for Potential MIC Solar Electric Applications Basis: 100,000 A/90.90.46

28. Nominal Design Parameters for PotentialMIC Solar Thermal Propulsion ApplicationsBasis: 100,000 Amps/cm2 engineering current density in MgB2superconductor2 cm thick multi-layer thermal insulation15,000 psi in tensile tethersParameterMIC Solar Thermal Propulsion Application Orbital LEOto GEOEarth to MoonTugMars CargoVesselThermal power, megawatt1510H2 propellant temperature, K250025002500H2 flow rate, kg/sec0.0250.130.25Thrust Newtons (Isp = 900 sec)22011002200Distance from Sun, AU111Concentrator area, m283041708340Diameter of MIC concentrator, meter3273103Length of primary MIC cable, meter100229460MIC primary cable current, Kilo Amp180250320Diameter of MIC primary cable, cm1.82.53.2Mass of MIC primary cable, kg1504301120Mass of tether and mirror surface, kg80370740Other mass (secondary cable& refrigeq.) kg50100200Total MIC concentratormass, kg2809002060High temperature receiver plus miscmass, kg20010001500Total solar thermal propulsion systemmass56019003560Nominal

29. V(kg/sec)/thrust time, days5/3.75/25/3.6Payload mass, metric tons1030100Total weight ofH2 propellant, metrictons8.12479Nominal metrictons8.12479

30. Nominal Design Parameters for Potential MIC Energy Storage ApplicationsBasis: 100,000 A/cm2 engineering current density in MgB2superconductor2 cm thick multi-layer thermal insulation (4 cm for rover) 30,000 psi tensile strength in tethers and support tubeParameterMIC Energy Storage ApplicationSpacecraftLunar Base(1) RoboticRoverEnergy storage,Megajoules10020005Form of storageCircular loopCircular loopLinearquadrupoleDimensions of storage unit50 metersdiameter100 metersdiameter10 meterslength, 2 meterswidthDiameter of support tube, centimeters11335.5Current in MIC cable, Amps1.1 x 1063.3 x 106500,000Length of MIC cable, meters16032050Mass of MIC superconductor, kg10006000150Mass of thermal insulation, kg360192070Mass of support tube, kg125240025Mass of tether network, kg19030040Mass of refrigeration equipment, kg5030010Total mass of MIC storage unit, kg172510,920295Refrigeration load, watts(th)7422Solar power generated at 1 AU usingintegrated solar cell array , KW(e) 50020005Specific mass, kg/MJ(e) stored175.559Specific mass, kg/KW(e) generated at 1AU3.45.5591) several independent storage loops, each of 2000 MJ capacity, would be usedfor the lunar baseNominal base

31. New Astronomical Discoveries Enabled by MIC Space Telescope
Imaging of First Stars and Galaxies forming in the Early Universe
Early detection and location of potential Earth impacting objects
Detection and imaging of terrestrial planets out to 100 light years
High resolution imaging of black hole boundaries
MIC Space Telescope
Spectroscopic imaging to detect life on planets around other stars
Detailed measurement of dark energy effects on the expanding universes
Very high resolution of Earth processes, e.g., ground movements
High resolution imaging of distant bodies in solar system (Pluto, etc.)

32. MIC Summary and Conclusions
|Strong, rigid large space structures based on a network of superconducting (SC) cables and tensile tethers appear practical
zStructure is launched from Earth as a compact packaged payload of SC cables and tethers
zAfter delivery to desired location in space, SC cables are energized with current, causing the MIC structure to automatically deploy into its final desired shape
zFinal dimensions of MIC structures can be a kilometer or more
|MIC applications include large solar collectors for solar electric generation and solar thermal propulsion, electric energy storage, large space telescopes, etc.
zStructures are very lightweight
zRefrigeration requirements are small
|Presently high temperature superconductors (HTS) are practical for MIC applications
zCan operate at temperature up to those of liquid N2
zMgB2and YBCO conductors favored options
zExisting high current densities in HTS conductors expected to gohigher

33. Backup

34. Potential MIC Applications –On Surface
|Solar electric power
zMIC structure provides a very large, lightweight solar collector that focuses sunlight into a solar cell array or solar dynamic power cycle
zPotential for high power, 100’s of KW(e) and low specific weight (kg/KW(e)) systems
|Large scale electric energy storage
zProvides very lightweight (kg/KWH) storage of large amounts of electric energy for bases on the Moon and other bodies
|Magnetically shielded habitats for astronauts
zQuickly and automatically erected when energized

35. Potential MIC Applications –In Space
|Solar thermal propulsion
zMIC structure provides a very large lightweight solar collector that focuses sunlight into a high temperature propulsion unit toheat H2propellant
zPotential for high thrust, high Isp(~1000 seconds) propulsion
|Solar electric power
zSimilar to MIC surface solar electric system
|Large scale electric energy storage
zSimilar to MIC surface electric storage system
|Magnetically shielded habitats for astronauts
zSimilar to MIC surface habitats
|Large scale space telescope
zMIC structure supports reflecting surfaces to produce ~1 km diameter telescope
|Propellantlesspropulsion using planetary magnetic fields

36. Functional Requirements for MIC Superconductor
•MIC superconductors able to operate at 20 K or above in strong magnetic field with good current density
Operating TemperatureCurrent Density & Magnetic Field Capability
MIC Superconductor
Operational Stability•Engineering current density of conductor (superconductor plus substrate) can be 100,000 Amp per cm2or greater•Can operate in magnetic fields up to 4 Tesla
•Remains superconducting for all anticipated conditions including local flux jumps and conductor micro-movements
•Operates at anticipated conditions without mechanical fracture or cracking
•Can be wound into compact package for launch
Mechanical Integrity

37. Preliminary Assessment of High Temperature Superconductors for MIC Applications
|HTS conductors already in commercial production
|Practical applications already demonstrated
zHigh power motors –5MW built, 36MW under construction
zHigh power generators and synchronous condensers
zPower transmission
zMaglev
|Substantial improvements likely in next few years –higher current density and field capability lower cost, longer conductor length
|BSCCO conductor production capacity limited by availability of silver for matrix –MgB2and YBCO conductors not limited
|MgB2probably ultimately lower in cost than YBCO –however, both are promising candidates for MIC

38. Design Issues for MIC Superconducting Cables
|Thermal insulation
zType and thickness
zMethod for expansion from compressed thin layer to full thickness
|Refrigeration
zOptimum operating temperature
zCooling system design
|Superconductor
zDesign and operating current of multiple independent conductors
zAttachment/support of multiple conductors on MIC cable
|Reliability and redundancy of MIC SC cable
zCapability to continue operation if individual conductors or coolant circuits fail

40. Erection Process for MIC Thermal Insulation
1
Package MIC Cable Structure into Compact Payload
2
Launch and Deploy MIC Payload into Orbit
3
Energize MIC Cable with Partial Current
6
Thermal Insulation Layer Expands to Full Thickness
5
Energize Aluminum Conductors to Expand Thermal Insulation
4
MIC Structure Expands to Initial Shape
7
Energize MIC Cable to Full Current
8
MIC Structure Expands to Final Shape

41. Thermal Insulation Parameters for Illustrative MIC Applications
ApplicationsParameterSolarElectricSolar ThermalPropulsionEnergyStorageSpaceTelescopeLocationLunar BaseSpaceLunar BaseSpacePerformance5 MW(e) @ 20% solar cellefficiency50 MW(th) H2 propulsion Isp = 950 sec[10,000 Newtonthrust] 30 MWH[100 KW for2 weeks] 300 meter[200 timesHubblediameter] # of MIC cables onloop @ 400,000 Ampsper cable1116(c) [inside 0.5 minsulatedtube] 1MIE loop diameter, meters1602301000300Total MIC cablelength, km0.510.733.10.94Total mass ofinsulation(a) package, kilograms2603702500 (d)480Mass of insulation, kgper square meter ofloop1.2 x 10-28.8 x 10-33.5 x 10-36.8 x 10-3Heat leak, watts (b)4260500 (e)77Notes: a)Insulation thickness on MIC cable is 2 centimeters Density = 120 kg/m3b)Heat leak based on 200 K average surface temperaturec)Multiple MIC cables (16 total) required to achieve total current of 7 x 106 Amps inenergy storage coop. The 16 cables are contained inside a 0.5 meter diameter thermallyinsulated tube, with 4 centimeters of insulationd)Mass of insulation based on 4 centimeters thickness, with density of 120 kg/m3e)Refrigeration during 2 week night period is supplied from cold sink refrigerated bypower generated during 2 week day periodHeat

42. Design Approach for MIC Superconducting Cables
|Individual MIC conductors are independent of other MIC conductors
z~10,000 Amp nominal current in individual MIC conductor
zEach conductor has its own cooling circuit and current input/output leads
zEach conductor several multiple SC sub-conductors (e.g., 8)
|MIC SC cable incorporates many individual independent MIC conductors onto common support tube to provide desired total current
zMIC cable carrying total of 400,000 Amps would have 40 individual conductors, for example
|If an individual conductor fails (e.g., coolant circuit leak, mechanical failure, space debris impact, etc.), MIC cable continues to operate
zFailed conductor transfer its current to other conductors by magnetic induction

43. Procedure to Maintain MIC Current if One of the
Sub-Conductors in a MIC Cable Were to Fail or Leak
Action 1
Outcome
Other MIC Conductors Inductively Takes Over Most of the Current from the Failed One
No Additional Action Taken
MIC Conductor Fails due Either to Coolant Leak or Micro Meteor Impact
Coolant Flow to Conductor Ceases
OR
Action 2
Outcome
Current is Increased Slightly in Re-Connected Conductor Which is Inductively Coupled
One of the Remaining MIC Conductors is Re-connected to Power Supply
Notes
Action 1:Total current carried by MIC cable will drop slightly. For 40conductor cable, total current will decrease by <0.1%, due to inductive coupling of the MIC conductors
Action 2:Total current carried by MIC cable can be kept at original level, by temporarily reconnecting just one MIC sub-conductor to its power supply

44. MIC Solar Thermal Propulsion Application
|3 MIC solar thermal propulsion applications evaluated
|1 MW LEO to GEO tug
z5 MW Earth to Moon tug
z10 MW Mars cargo vessel
|5 MW Earth to Moon tug chosen for further detailed baseline design effort
zHigh priority for first application
zSystem can be readily scaled for other applications
|Specific mass of MIC solar concentrator is 0.2 kg/KW(th)
zSpecific impulse of hot H2propellant is 900 seconds
z73 meter diameter MIC solar concentrator
|Potential for generation of electric power as well as solar thermal propulsion

45. MIC Energy Storage Application
|3 MIC energy storage applications evaluated
z100 megajoulesystem for spacecraft
z2000 megajoulesystem for lunar base
z5 megajoulesystem for robotic power
|2000 megajoulesystem for lunar base chosen for further detailed baseline design effort
zHigh priority for first application
|Specific mass of MIC lunar base energy storage system is 5.5 kg/MJ(e)
zMIC loop diameter is 100 meters
zSC current is 3.3 megamps
zTotal mass is 1 metric tons
|MIC mass dominated by superconductor needed to carry very large currents, plus conservative tensile stress in tethers
zMass could be reduced by factor of ~3, with higher current densities and tether stress
|MIC energy storage system can also be used to generate MW(e) power levels

46. MIC Technical Issues
|Ability to pack MIC superconducting (SC) cables and tethers intocompact payload for launch which is then deployed once in space to form extended structure
zSC and coolant tube flexibility
zExpansion of compacted thermal insulation around SC and coolant tubes once in space
zPractical solutions identified for packing/deployment operations
|For certain applications, ability to carry currents >>500,000 Amps in compact flexible SC cables without exceeding maximum field capability
zSingle small cable can carry up to ~500,000 Amps
zVery large currents can be carried by array of multiple cables separated by tether network to keep magnetic fields at acceptable levels
|Robust and reliable operation of SC network
zNot vulnerable to single point failure
zUse of independent multiple SC/coolant circuits that are inductively coupled so that remaining circuits can compensate for circuits that fail
|Optimize choices for SC, coolant, and operating temperature

47. MIC Development –Preliminary Assessment
|High temperature superconductor (HTS) development rapidly proceeding
zHTS current density expected to substantially increase
zHTS cost rapidly decreasing
zMgB2and YBCO conductors are leading candidates
|Present HTS conductors can be used to test and demonstrate MIC concept
zTests/demonstrations can be done on Earth laboratories, both in atmosphere, and in large vacuum chambers
zTests can be carried out starting with compact package of HTS conductors and tethers that are energized to form final structure
zTests can measure thermal input to HTS conductors, temperature distributions, forces, geometric tolerances, etc. in deployment structure
|Variety of structures can be tested at sub-scale including MIC
zSolar collector
zEnergy storage
zTelescope