SpaceElevatorIntegration

Title: Integration
[Cover Img]	About: Moderator: Brad Edwards Created: July 6, 2008 Modified: July 25, 2008	Tags: This is a collaborative article Discipline(s): Wiki, Engineering

 

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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