SpaceElevatorIntegration

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Title: Integration

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  • Moderator: Brad Edwards
  • Created: July 6, 2008
  • Modified: July 25, 2008

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  • This is a collaborative article
  • Discipline(s): Wiki, Engineering

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Integration

Building the individual components of a system can be easy until they have to fit and work together. The integration of the space elevator is actually more simple than might be expected but it is still complex. Below is the basic interaction matrix for the space elevator. This matrix drives decisions across the effort but in the form here is still incomplete and crude in terms of its static nature. The goal is to get this matrix interactive and constantly upgraded to include all aspects of the elevator interactions.


Additional Work Needed

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Space Elevator Interaction Matrix

System Component Subcomponent Affected component Implications
Ribbon Material Strength Cost Higher strength material will be more costly to develop and produce. The trade needs to be between required strength and cost.
Higher strenth material may mean a lower mass overall ribbon, fewer construction climbers and less repairs all which reduce cost
Ribbon Higher strength material implies higher operating tension and higher stored energy in the stretched material. Mitigation of catastrophic failure of CNT threads under extreme tension requires detailed small-scale design and testing.
Ribbon taper and overall mass are inversely propotional to strength.
Risk Lower strength equates to increased risk due to lower safety factor.
Lower strength also relates to higher perceived risk of construction.
Surface Climber A low friction ribbon surface means more challenges in the friction drive
A metalized surface will need repair and maintainence by the climbers.
Small-Scale Design Interconnect Risk Fewer interconnects results in higher risk
Wider interconnects are stiffer allowing less sliding of threads and possibly creating high stress spots
Narrower interconnects allow for more thread sliding and equlibration over long distances they also allow damage to interact across multiple segments
Tape sandwiches allow tension release from threads, easy splicing,... but can degrade
Woven CNT interconnects will be as resilient to the environment as the rest of the ribbon, can lock on or slide on threads as desired, more difficult to splice
Sliding interconnects allow for slow and consistent tension redistribution reducing tearing and catastrophic degradation of axial fibers.
Ribbon More interconnects results in higher overall ribbon mass
Climber More interconnects means higher splicing speed by climber and more mass to carry
Fiber size Cost Smaller fibers require more production time and processing time to convert into a ribbon. This converts into a more expensive ribbon.
Ribbon Smaller fibers imply easier attachment by interconnects and less separation lengths between fibers.
Climber Smaller fibers provide more surface area to grab but also more fragile fibers
Large-Scale Design Length Operations Destinations: at 100,000 km the ribbon can throw to Venus and Asteroids, at 119,000 km Jupiter is reachable
Overall Design The longer the ribbon the smaller the counterweight required. At 144,000km length the counterweight mass goes to zero.
Climber The longer the ribbon the smaller the useful climber for deployment that can be utilized at the upper end as a counterweight.
Taper Climber Higher taper ratio means lower ribbon capacity and smaller climbers. Climbers must move faster to build up the ribbon in a safe timeframe.
Ribbon Higher taper ratio means heavier ribbons for the same capacity.
Low taper ratio means higher material strength required or lower safety margin
Risk Higher taper ratio provides higher safety factor to survive more damage
Cost The higher the taper ratio the higher the overall construction mass and cost
Mass Operations Higher mass means more rockets and climbers to build.
Cost Higher mass means more expensive ribbon and deployment.
Schedule Higher mass ribbon takes longer to deploy.
Variations LEO Width Increased Risk Wider ribbon will reduce risk of damage due to LEO objects
Wider ribbon will increase possible damage by climber due to thickness.
Climber Must deal with wider ribbon
Mass Wider ribbon will have a larger percentage of interconnect mass and thus larger overall mass.
Smaller Width in Atm. Risk Narrower ribbon will reduce the risk of damage from wind
Climber Thinner width will be challenge for climber to clamp.
Thick vs Wide Risk Probability of impact from orbital debris and micrometeorites is higher with wider ribbons though wider ribbons can survive larger and more impacts. The wider the better from a risk standpoint.
Climber It is more difficult for climber to adjust to variable width than variable thickness
Coatings Characteristics Risk Damage to the coatings will reduce their effectiveness
Coatings will reduce damage by hazards such as atomic oxygen.
Climber Climbers must produce minimal wear on the ribbon to minimize damage to the coatings.
Special climbers required for laying down coatings.
Drive systems need to deal with coatings that may have a different coefficient of friction than the ribbon.
Ribbon Coatings increase the overall mass of the ribbon.
Immature technology for coating a CNT ribbon
Operations Re-coating of the fibers may be required due to wear
A coated ribbon may be easier to track with radar
Initial Ribbon Size Risk The larger the initial ribbon the more challenging the deployment. More launches or larger launches are required.
The larger the initial ribbon the faster the build-up and lower the risk of fatal damage at early stages
Schedule The larger the initial ribbon the shorter the deployment schedule - ~6 months for every factor of two in size
Deployment of a larger initial ribbon may require a longer up-front development time.
Cost The larger the size of the initial ribbon the more launches required - linear dependence
The larger the initial ribbon the fewer construction climbers required.
Climber The larger the initial ribbon the larger the initial climber
Alternatives Tube Climber Unless rigid (very massive) crimping and pinching will occur.
Risk High debris damage risk due to smaller frontal area.
Ribbon Much higher mass for a solid tube than a ribbon of fibers.
Climber Velocity Trade Constant Power Power Beaming Power beaming and power receiver on climber are simple - velocities range from < 20mph to >120 mph
Climber Drive system runs at variable speed through Earth's gravity well
Constant Speed Power Beaming Requires high power at Earth and less as you go up
Climber Constant speed drive is easier and lighter to gear
More complex power system
Velocity Schedule The higher the speed the faster the build up
Risk Immature technology for speeds above 200 km/h
Higher speeds required for safe transport of humans
Drive Friction: Tread Ribbon Flat ribbon design required
Designed to survive tread transit
Tread must account for contraction of ribbon during transit - if climber is at the limit of mass then the contraction could be 1 - 10%
Tread has low pressure on ribbon - pressure is linear with tread area
Tread must center ribbon - passive centering is preferred
Climber Simple, mature technology
Risk Minimal wear and tear on ribbon
Reduced efficiency due to bending of tread
Schedule Limited velocity implies slower delivery schedule to orbit
Friction: Roller Ribbon Flat ribbon design
Bending over rollers wears ribbon
Higher pressure on ribbon than tread design
Ribbon/rollers must work together to center
Climber Simple, mature technology
Risk Increased wear and tear on ribbon and rollers
Schedule Limited velocity implies slower delivery schedule to orbit
Magnetic Ribbon Very massive ribbon required due to wiring.
Risk Immature technology
Operations High-speed transport could allow higher performance.
Cost Very high due to ribbon mass and risk.
Payload Operations Payload handling affects overall operations
Climber Larger payload requires larger or higher efficiency climbers
Lower risk climbers required for human transport
Splicing Side-by-side Risk Immature technology
Ribbon Overlap, width, thickness and spacing affect ribbon mass
Engineered slippage above a certain tension enables debris and meteor survivability. Too rigid of grip induces tears, too loose and the affected length of ribbon becomes long.
Side-by-side splicing implies a full-length narrow ribbon – size can be limited by available thread size and interconnect design.
Climber Must be able to splice reliably at 10Hz.
Splicing must be done under tension.
End-to-end Deployment Requires deployment of full width and full mass ribbons.
Due to taper requirements, deployment must be from the middle under full ribbon tension
Cost Many large rockets required
Few construction climbers required
Climbers Must be able to deal with joints in the ribbon if used
Ribbon Joints must be made in place and hold full tension
Disposal Regulations Storage of climbers in orbit could be the subject of regulations
Operations Disposal or reuse of climbers will impact how the elevator is used
Cost Cost trade-off of disposal vs. Reuse is complex
Use of the climbers for parts in future applications could be a reasonable business model
Schedule If climbers are to be reused then the elevator will need to be shut down when the climbers are brought back down if a second ribbon is not available
Power Laser Beamed Schedule Reasonable power levels will enable 8 day travel from Earth to GEO
Multiple climbers utilizing the same power beaming systems will require detailed scheduling
Climbers Need tracking beacon on climber
Power receiver is mature PV technology
Operations Clouds will reduce power and climber will need to deal with it
Shadow of ribbon on PV array could cause issues
Power Sys PV array needs to supply HV to motors
Thermal/mass trades depending on Si or GaAs array
Regulations High-power laser use will require FAA clearance
Issues with reflections off of climber
Risk Low development risk
Beam RF Power Sys Large receiver
Operations Similar receiver and converter to solar array
Cost Inefficient system increases operations cost
Climber Large rectenna receiver, possible thermal issue
Conducted RF Ribbon Must be large (10 meters+)
Operations Powers lower climber only
Climber RF receiver
Conducted Electrical Ribbon Two conductors with insulator
Cost Efficiency of transmission drops with distance, at GEO efficiency can be small fractions of a percent
Operations Difficult to power multiple climbers differently
Damaged climber may short conductors
Power Sys Simple
Risk Has single point system failure – damaged ribbon
Climber Simple, low mass receiver
Drives are high resistance to use power efficiently
Solar Schedule Low power delivery slows transit dramatically
Risk Mature technology
Slow deployment with this system implies a longer schedule with a small and vulnerable ribbon
Power Sys None on Earth, only climber receiver
Possible alternative could use reflected solar power form Earth to increase power density
Cost Increase climber but reduced power beaming costs
Operations Slowed
Climber Receiver design is solar arrays with orientation actuators
Nuclear Schedule Risk, cost, personnel protection
Anchor Power Size Cost The larger the power system - higher the cost.
Operations Larger power systems will require more personnel and more extensive maintenance operations.
Power Sys The power beaming system size will be limited by the power available on the station.
Anchor: Drive Larger power systems will allow for larger drives
Anchor: Platform The larger power systems will require more volume on the platform, more fuel storage.
Fuel Operations The choice of fuel will drive the operations in terms of delivery, safety, regulations
Maintain Operations Maintenance requirements will determine station l need to go to drydock and thus downtime.
Drive Mobility Operations Drive performance determines the anchor’s ability to move the ribbon out of the path of satellites and storms.
Mobility also enables the anchor to travel to drydock for maintenance. Higher speed and mobility means less down time.
Ribbon The greater mobility reduces the number of collisions with the ribbon and reduces the required robustness of the ribbon
Cost The better the drive the higher the cost.
The reliability and lifetime affects the cost.
The fuel used in the drive will impact the operations cost.
Risk Mobility of the anchor reduces the risk from debris and storms.
Size Risk The larger the drive the more quickly the anchor can respond to requests to move.
Accuracy Tracking The accuracy of the drive enables use of higher accuracy tracking.
Risk The accuracy of the drive reduces of the possibility of impact by debris.
Anchor The anchor station will need to be equipped with the GPS and other navigation tools
Platform Size Power Sys The size of the platform can limit the use of RF and FEL power beaming systems due to their required footprint. For FEL a length of about 150 m is required. Solid-state lasers require less footprint.
Stability Power Sys A stable platform reduces the need for a optics system that can track the climber over degrees continuous on a fast timescale. The lower stability platform will result in higher power system and maintenance costs.
Robustness Operations Robustness implies longer time between maintenance in drydock. Less-expensive operations.
Design Schedule A better design for the platform including high-quality housing and recreation on the platform will reduce the schedule impacts due to the workforce needs to have time away.
Risk A better design for the platform will reduce the stress of the workers and improve their performance.
Attachment Mobility Operations Required removability for transfer between anchor stations for repair and general drydock.
Robustness Cost Less repair and down time with greater robustness.
Capability Operations The reeling in and out as well as proper tensioning is required for proper and safe operation.
Risk The capability of the attachment will enable reeling in and out of the ribbon as well as properly maintaining the tension on the ribbon. Propoer execution of these operations will reduce the overall risk.
Being able to reel in the ribbon to deal with malfunctioning climbers also reduces risk.
Location E. Equat Pacific. Risk This location was selected to minimize risk from the weather.
Operations This location in the middle of nowhere impacts operations by making the trip to and from the anchor long and more costly. Maintenance and repair of the anchor require long travel distances or repair at sea.
The extremely mild weather at this location makes operations easy in terms of maintaining location, stability and weather damage.
Anchor The anchor must be very reliable due to the remote location.
Cost The cost of construction of the anchor for this location is less than for other locations but the general operations will be more costly due to the remote location.
Australia Politics US politics will not be happy with foreign ownership
Associated with friendly country
Near volatile countries such as Indonesia
Operations Possibly close to major cities
Ribbon goes up at an angle
Risk More lightning
Cost Funding can be split
Land Operations Movement on land is more difficult
Easy access for cargo and people
Plenty of room for people to live and facilities
Risk Lightning is more prevalent
Easy access for terrorists
Anchor No anchor station
General Operations GEO location slots may be filled - may need to locate south of Equator
Alternatives Multiple Legs Anchor Multiple stations need to be coordinated to maintain tension
More anchor maintenance due to larger number of anchors
Ribbon Redundant ribbons at bottom mean additional mass though each leg can only support the same climber
Dynamics are different than single leg and not well understood
Dynamics of the loss of a single leg are not understood
Attachment point needs to be able to add and replace legs
Attachment point needs to hold the tension for all
Added mass of attachment and legs comes out of climber/payload mass
Climber Climber must be able to ascend one leg, cross attachment point and continue up
Smaller climber for same primary ribbon
Climbs at an angle
Operations More available integration time for attaching climbers to leg ribbon (~time for 1 leg *#of legs)
Coordinating climbers from different legs is required
Deployment is more complex, attaching legs
Power Sys Possibly more, smaller beaming stations - each associated with a leg
Risk Redundant legs reduce risk of loss at low altitudes
Risk of attachment failure
Cost Additional anchors adda cost
Anchor maintenance adds cost
Attachment point adds cost in development and operations
Additional ribbon complexity adds cost
Additional power beaming systems add cost
Power Beaming Laser FEL Size Requires large platform
Location Line of sight, no clouds
Anchor Efficiency requires more power
Operations Complex system
Regulations Restrictions on open high-powered lasers near people, airplanes, etc.
Solid-State Cost $100/W capital cost
Major replacement of pump diodes every five years
Power Beaming 30% wall plug efficiency determines power required
No need for large station to expand beam
Risk Megawatt laser power can damage airplanes, animals and nearby humans
1KW laser module has been built, current program pushing to build 100kw and believe MW laser possible - may need to couple lasers and consider 10-20% duty cycle for coupling
Operation 500 microsec pulse, 10-20% duty cycle
Easy operation, maintenance
Transportable in small container
Line of sight with climber required – no clouds
Replacement required at regular intervals
No expendables
Climber Wavelengths of 810 to 990 nm, receivers can be GaAs or Si depending on laser design
Si receivers would imply a possible thermal issue
High quality beam allows for small receiver diameter
Deployment Small laser modules implies easy delivery to stations
Small laser modules imply easy dispersion to global locations for use during deployment and then relocation for standard operations
Primary Optics Mirror Heat and pointing issues
Operations Climber Required tracking becon
Require proper PV arrays
Beam RF Antenna Climber Large receiver
Cycle Time Operations Transmitter is not movable, line of sight, no clouds, near power plant
Cost Inefficient power delivery, very large transmitter, additional power plants
ITU Regulations Restrictions on beamed power and safety
Conducted RF Ribbon Metal coated
Climber RF receiver
Operations Multiple climbers?
Conducted Electrical Design Ribbon Dual conductors with insulator between Increases mass of ribbon dramatically
Power system High transmission losses
Coupling Climber High resistance motors required
Ground Anchor Power at anchor
Damage Operations Multiple climbers?
Risk A ribbon sever could cut power, lightning rod
Locations Deployment Regulations During deployment it will be useful for the power stations to be located at widely spaced locations on Earth. This will require international cooperation.
Anchor The anchors may need to be mobile if they need to be at different locations during deployment and operations.
Deployment Satellite Initial Ribbon Size Risk The larger the ribbon the less the risk of damage and destruction - exponential improvement.
Schedule The larger the ribbon the shorter the schedule - linear dependence.
Climber The larger the ribbon the larger the initial climber - linear dependence
Spacecraft The larger ribbon requires a larger support system and size is limited by the capabilities of the launch vehicles available - structure is linear dependence, fuel is exponential increase with ribbon size.
Spooling Ribbon Spooling determines the ribbon design, width, flexibility required, and the risk of twisting and tangling.
Spacecraft Combining spools - End or side unspooling
Propulsion Electric Power Sys The electric propulsion requires high powers. This power can be supplied by the power beaming but it will impact the design of the power beaming system. Tracking, scheduling and location of the power beaming system will be the main considerations.
Schedule The electric propulsion will require a much longer time (6 months to years) to move the spacecraft from LEO to GEO. A solid rocket engine would do the move in days.
Risk Development risk - Longer SC operation - longer time in radiation belt
Ribbon Due to the higher efficiency and lower fuel mass a larger initial ribbon can be deployed
Spacecraft Reduced structure requirements
Chemical Ribbon A smaller initial ribbon can be deployed with the same launchers than for electric propulsion.
Schedule Faster move from LEO to GEO
Risk Low development risk - shorter SC operating time - less time in radiation belts
Spacecraft Heavier structures for fuel - exponential growth
Power System Nuclear Regulatory Extensive regulatory requirements
Launch Limits on launch
Cost Expensive in direct and indirect costs
Spacecraft Can be used for electric propulsion
Beamed Power Sys Simple, mature technology
Lightweight system
Schedule Less than 100% duty cycle will increase schedule
Risk Powerful lasers located at different locations – both technology transfer and safety risk.
Spacecraft Must operate in low-Earth orbit with <100% duty cycle
Must orient to the laser power beaming
On-Orbit Assembly Cost Manned on-orbit assembly is likely to be much more expensive in current environment
Schedule Manned assembly has much higher schedule uncertainty
Spacecraft Autonomous assembly is more complex
Manned assembly more expensive but less risk
Deployment Altitude Schedule Optimal altitude reduces the deployment schedule
Challenges International International Consortium Operations Fewer countries and entities to protest operations.
Stronger alliance to support and protect the anchor.
Stronger alliance to address space treaties
Schedule All activities must be coordinated with the consortium members
Cost Int. Consortiums cost more due to interactions and utilizing less capable manufacturers.
More entities to spread the cost and risk among
Military Protection Risk Reduce the risk of terrorist attack
Satellite Debris Prob. Of Collision Ribbon Modification of ribbon dimensions to optimize survivability
Movement Operations Active avoidance, maintenance,
Atomic Ox Surface Ribbon Coat the ribbon or design the ribbon to survive
Operations Repair and maintenance
Radiation Lifetime Ribbon Design to survive radiation, mods may increase size of ribbon
Climber Structure Increased speed and shielding required for transporting people
Oscillation Dynamics Ribbon The taper length and mass determine the natural period of the ribbon, modification of the dimensions will change the frequency of the oscillations.
Operations Active damping of oscillations may be required
Lightning Multiple Legs Anchor Location requirements
Ribbon Conductive or non-conductive
Wind Shape Ribbon Narrower and thick inside atmosphere
Wave Height Anchor Locate where minimal winds
Jet Streams Constant Anchor Locate where minimal jet streams
Altitude Vary Ribbon Minimize cross-section at level of high altitude winds
Hurricane Winds Anchor Locate out of hurricane zones
Induced Currents Ribbon Conductive/non-conductive sections to reduce the overall charging and currents
Satellite/Debris Power Ribbon Modification of ribbon dimensions to optimize survival
Ribbon position Operations
Debris Tracking Sensors Optical Cost New system to be developed
Risk Increased development risk
Better tracking reduces operations risk
Radar Cost Mature system in use
Risk Lower accuracy increases risk
Accuracy Risk Lower accuracy increases risk
Cost Higher accuracy implies higher construction and operations cost
Sensitivity Risk Lower sensitivity means lower performance and high risk
Cost Higher sensitivity means higher cost in construction and operations
Ribbon Low sensitivity means impacts on ribbon from small objects, the ribbon must be more resilient

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