Consistent with our goal of focusing the Space Elevator community towards a common effort, each year the ISEC Board of Directors decides upon a theme that becomes the focus of many ISEC activities. These include:
The subject matter to be expressed in the annual ISEC Poster
A topic for the International Space Elevator Conference
Below are the annual Themes chosen by ISEC:
2017 - Design Considerations for Space Elevator Simulation
This 2017 study has been initiated and will evaluate the various aspects of the necessary computer simulation to support the development of the space elevator. With its unprecedented scale, wide range of physics and engineering concerns, and pioneering materials, the space elevator will require computer simulation of many of its aspects before any major component of it can be built.
The goals of this study are to:
· specify the aspects of the space elevator which require computer simulation, · develop the requirements necessary for a simulation system which can carry out the above tasks, · make recommendations for software tools needed to build the simulation system and · define a computing model for the simulation system.
Aspects to be simulated include:
· dynamics of tether and climber motion, · electrodynamics of the tether and its interaction with the magnetosphere, · radiation effects of tether and climber materials, · wind forces, and more.
Based on the requirements and recommended tools, a computing model will be defined which will serve as a framework for the construction of a simulation system. In general, computing models address the following issues:
· configuration of computing hardware and software · distribution, access and maintenance of computing resources · work-flow, including coding, the running of simulation jobs, analysis of results and archiving · testing, validation and benchmarking of models and tools.
2016 - Design Considerations for the GEO Node, Apex Anchor and a Communications Architecture
This 2016 study report was kicked off in September 2015 to establish a baseline for designing the Apex Anchor and the GEO Node. In addition, a communications architecture for the space elevator will be sketched out. This 2016 ISEC study addresses three critical aspects of the space elevator infrastructure: The Geo Node, the Apex Anchor and how the two will communicate with the rest of the space elevator.. The key question to ask at the present is: What are the functional needs of the space elevator that will drive the design of the segments. During this study, the team will assess many issues dealing with two nodes in deep space to include:
What is an Apex Anchor? Describe in detail the major sub-systems. * What are the functional elements of the Apex Anchor? * What are the missions of the Apex Anchor?
What is a GEO Node? Describe in detail the major sub-systems. * What are the functional elements of the GEO Node? * What are the missions of the GEO Node?
What is a Comm Architecture? Describe in detail the sub-systems. * What are the missions for the Comm Architecture?
2015 – Design Characteristics of a Space Elevator Earth Port
This study provides the International Space Elevator Consortium’s (ISEC) view of the Earth Port (formerly known as the Marine Node) of a Space Elevator system. The Earth Port:
• Serves as a mechanical and dynamical termination of the space elevator tether; • Serves as a port for receiving and sending Ocean Going Vessels (OGVs); • Provides landing pads for helicopters from the OGVs; • Serves as a facility for attaching and detaching payloads to and from tether climbers and attaching and detaching climbers to and from the tether; • Provides tether climber power for the 40 km above the Floating Operations Platform (FOP); and, • Provides food and accommodation for crew members as well as power, desalinization, waste management and other such support.
2014 - Roadmaps and Architectures
The concept for this year-long ISEC study is that the Architecture & Roadmap Team will develop a series of roadmaps leading to an operational space elevator. The report will quantify the step by step processes on how to move towards initiating a project, developing the research and development, conducting risk reduction and then building an infrastructure. The team will emphasize where the project is going and how funding can follow the layout of a series of roadmaps. The space elevator community has a variety of approaches for development of this low cost space access infrastructure. An important point is that many of the various architectures for space elevators are real and can be successful. To ensure that the community progresses in concept refinement, a year-long study must be conducted to trade each concept against others to drive great ideas to the surface while identifying risk mitigation efforts. There are at least five architectures that will initiate the discussion:
Dr. Edwards Baseline: Single tether, laser powered. [$ 6B in 2002$]
IAA Baseline: Solar powered climbers, multiple tethers. [$ 15B in 12$]
Rotating tether between GEO and Marine Node. [$ ? B]
A segmented tether with multiple stations. [$ 41B in 2009$]
Obayashi Architecture: Presented in Sept. in Beijing. [$ 100B in 2013$]
2013 - Tether Climber
The design of the tether climber has many dimensions. The first is to identify the types of climbers to include designs for initial buildup, operations, atmospheric protection, beyond GEO, and return to Earth. The study will look at specific designs of major segments of a climber to include the motor, structure, attachment to the tether, and source of power. In addition, a quick look at the operational approach will be included. The tether climber design will estimate the structural and payload mass to be loaded into the cargo bay. In addition, the length of time on the tether and speed will determine mass movements per week.
2012 - Operating and Maintaining a Space Elevator
For many reasons, it is necessary to define a baseline configuration for the Space Elevator. Such a baseline forces one to make the hard decisions as to where the Base Station will be placed, how it will be staffed, how it will receive cargo and send it to space, how it will be powered, where the control and command centers will be, etc. And until such a configuration is defined, it is very difficult to place a price-tag on sending cargo to space.
Defining such a baseline also forces 'opponents' of this baseline to come up with a well-thought out alternative to one or more items in the baseline. For example, if the baseline defines the Climbers being powered with Lasers throughout the climb, and someone wants to suggest an alternative (for example, using a mix of Laser and Solar Power), having this baseline in place will show what must be modified to consider the alternative. This leads to more rigorous thinking about the design and operation of a Space Elevator.
By selecting "Operating and Maintaining a Space Elevator" as the 2012 Theme, ISEC wishes to focus the activity of all interested parties towards making the hard decisions and trade-offs to come up with a realistic Operations scenario.
2011 - Research and thought targeted towards the goal of a 30 MYuri tether
The biggest hurdle on the way to building a Space Elevator is constructing a tether that is both strong enough and light enough to support itself and cargo-carrying vehicles. We estimate that a tether with a minimum strength of 30 MYuris will be sufficient to construct the Space Elevator and ISEC wishes to promote research and thought targeted towards this goal.
The target of a 30MYuri tether has been specified in The Feasibility Condition, a study produced by Mr. Ben Shelef of the Spaceward Foundation (and an ISEC Board Member). At this time, only carbon nanotubes seem to be potentially strong enough to produce a tether with this minimum specific strength. However, the strongest tether material (a thread) demonstrated so far has had a specific strength on the order of 1 MYuri. Governments, corporations, academia and private individuals are all working towards making stronger nanotube structures.
By selecting "Research and thought targeted towards the goal of a 30 MYuri tether" as the 2011 Theme, ISEC wishes to focus the activity of all interested parties towards this goal.
(A Yuri (named in honor of Yuri Artsutanov) is a unit of Specific Strength. It is equivalent to 1 Pascal-cubic-meter per kilogram. A Mega Yuri (MYuri) is equivalent to the commonly used units of 1 GigaPascal-cubic-centimeter per gram (1 GPa-cc/g) and to 1 Newton per Tex (N/Tex).)
2010 - Space Debris Mitigation - Space Elevator Survivability
One of the issues that naysayers continue to bring up in objecting to the practicability of Space Elevator is the issue of Space Debris. There is no doubt that Space Debris is a large and growing issue. More nations (and now, even some private ventures) are launching devices into space and the body of debris in space, especially in LEO (Low Earth Orbit) continues to grow. Due to its being a permanent structure, the Space Elevator may be uniquely vulnerable to this problem.
By selecting "Space Debris Mitigation - Space Elevator Survivability" as the 2010 Theme, ISEC wishes to focus the activity of all interested parties towards investigating this issue and a) seeing how serious the problem actually is and b) recommending strategies to mitigate the problems that are real.
A summary report of the Space Elevator Roadmap workshop
Examining the progress toward a Space Elevator Architecture
23 August 2014
Michael A. Fitzgerald
On the last day of the recent Space Elevator conference in Seattle, the ISEC roadmaps and architecture study leads held a workshop with the attendees of the conference. The workshop had two purposes and one key objective.
To introduce our definition of the ISEC Space Elevator Architecture's 5 discrete segments; Climber Segment, Tether Segment, Marine Node Segment, HQ/POC Segment and the Tether Tenants Segment.
To seek the wisdom and advice from the attendees regarding the kind of demonstrations they would like to see to “prove” the viability of the functions within the reviewed segments AND to receive the attendee’s advice regarding the substantial success criteria the demonstrations need to match or surpass to be successful.
To initiate the first engineering efforts along the (admittedly) long road to the engineering development of a Space Elevator.
The workshop briefer presented graphics for the 3 key segments within the SE architecture. The graphics laid out the suggested pathways leading to the next major pre-development architecture activity; the implementation planning phase. Along each of those 3 paths … a series of tests, inspections, simulations, and / or demonstrations are called for. This envisioned activity, or set of activities, is to establish technological viability and the engineering validity of the segment’s make-up. The response from the attendees was fantastic; by substance and wisdom.
Segments discussed and reviewed
The workshop briefer presented graphics for the 3 key segments within the SE architecture. The graphics portrayed the path along which segments must move on their way to preliminary and then detailed implementation plans. For the development engineers, these implementation plans are the needed series of design efforts … to build the Space Elevator. To move toward these plans, each segment must “demonstrate” that the Space Elevator holds the necessary mature technologies and validated engineering approaches needed for the design and development phase … beyond the portrayed roadmap.
The workshop briefer presented this graphics for the Climber Segment. In the presented graphic, the Climber Segment’s path is seen as resolving 3 primary functional roles of the climber.
Delivery of a payload LEO & GEO altitudes
Repair of the Tether
Delivery of payloads above GEO
For each of these three primary roles the workshop offered that a test and demonstration taxonomy for 8 required functions was needed; structure, gripping, the motor, the brakes, power above 40 Km altitude, power below 40 Km altitude, a protective box for traversing the lower 40 Km, and payload support. Obviously, the test taxonomy execution can “share” the results across the functions, but it is likely that different climber configurations will require different engineering validation efforts within the test and demonstration taxonomic execution. The point is that climber configurations could vary for LEO destinations versus Climbers destined beyond GEO.
The feedback from the attendees was spectacular and is documented – in summary here. Analysis of the feedback will be more thorough over the next few months, but at first review …the attendees seek a wide range of test & demonstration events to assure our place in the competition for venture capital as well as our construct of needed, empirical engineering knowledge.
The workshop briefer presented this graphics for the Tether Segment. In the presented graphic, the Tether Segment’s path is seen as resolving the 3 primary functional manifestation of the Tether.
Delivery of 100,000 Km of Tether to Space
Functional knowledge of the Tether; represented in a Tether Simulation
Tether Control and its components
For each of these three primary roles the workshop offered that a test and demonstration taxonomy for 5 required functions was needed; the tether’s dynamics, the first 5 modes of tether dynamics, perturbations from the Sun, the Earth, and the Moon, climber induced perturbations on the tether, and the hazards from debris strikes on the tether.
As with the other segments, the purpose of the workshop was to seek the wise feedback from conference attendees. For many, the Tether Segment and the set of needed tests, inspections and examinations it needs to reach readiness prior to design development , is exactly what the entire Space Elevator’s future is all about. The Tether Segment is composed of more unknown unknowns than the rest of the Architecture. A extensive campaign of test, experiments, inspections and analyses is needed. So, we asked for feedback. We got it. See the summary.
Marine Node Segment
The workshop briefer presented this graphics for the Marine Node Segment. In the presented graphic, the Marine Node Segment’s path is seen as resolving the 4 primary elements of the Marine Node Segment.
Floating Operations Platform
Facilities Support Platform
Ocean Going Vessels
For each of these four elements the workshop offered that a test and demonstration taxonomy to examine and delineate 5 required functions was needed; site location for the Marine Node, the ocean currents at that location, and the hazards from debris strikes on the tether, sea water status and makeup, Sea floor geology and seismology, weather and storms in the locale. Obviously, a great deal more must be tested and evaluated. We sought the attendee’s aid in detailing a larger and more complete set of tests needed to reach technology maturity (possibly); and mature & valid engineering approaches (most likely). We got the feedback we needed. See the summary.
The idea of letting months of hard work on you little project be open to the public for inspection … is always a little embarrassing. As it turned out I was not embarrassed; and the attendees were warm and welcoming in their feedback. It was a wonderful, humbling moment and I am proud to have been a part of it. The engineering of the ISEC Space Elevator is underway! The first step toward our destination has been taken.
The workshop feedback archive
The following is an accumulation – without comment - of the feedback received at the 23 August workshop. Repeated items were deleted.
Summary of Suggested Demonstrations
“Demonstrations” should include a range of tests, inspections, analyses, simulations, and more. Some demonstrations are likely to be a sequence of test events; a taxonomy of tests.
Security process overall
Initial attachment or reattachment
Adverse sea state survival / rogue wave
Node exchange (new ship)
Storm Demo – “Perfect Storm Demo”
Assembly demo – Payload onto climber onto tether
Adverse weather survival
Receipt on transfer of climber
Strength / tension / dynamics
Tether disposal or removal
Maintenance and repair
Long duration exposure
Metrology for location, state, dynamics
Space debris impact demo
Electrical survivability demo
Wear and tear demo
Simulation on the internet
Harmonic suppression demo
Electromagnetic tests of all sorts
Tether test in the Orbital mode
Loss of signal
Telemetry & monitoring
Transfer to descent
Climb & Descend
Adverse weather survival
Long duration reliability
Response to vibrations / oscillations
Detached climber re-entry
Diagnostics & failure modes
Braking demo to slow
Braking demo to be stationary
Computer Simulations … OPS simulator
Radiation Survivability Demos
Summary of Success Criteria
Success Criteria are not yet quantified citations of the regime of information needed as a result of the “demonstrations”. Standards will be set at the entry to next phase. Criteria is to standards, as weight is to 100 pounds.
Sea Life effects
Keep out zone limits
Positioning / re-positioning capabilities
Extent of tether repositioning
Manufacture defect detection
Repair defect detection
Extent of tether splicing
Tether Friction limits
Out of atmosphere
Categories not yet defined - looking for feedback!
A summary report from the Research mini-workshop at the International Space Elevator Conference in Seattle
23 August 2014
A wide-ranging discussion of research-related topics was conducted as a mini-workshop at the 2014 Space Elevator Conference in Seattle.
The goal of the mini-workshop was to stimulate thoughts and inputs from the conference attendees on space elevator research projects. Some detailed objectives were:
Gain an awareness of the ISEC Research Committee’s goals and process
Review the list of topics that the Committee has produced
Identify potential contributors with relevant skills and interests
Where possible, add some level of detail, particularly on those topics where little work has so far been done
Where possible, propose who could carry out the work and where
From the teams at separate tables, discussions developed observations, ideas, proposals, and preliminary conclusions in several areas. What follows are notes representing highlights from those discussions.
Manufacturing limits, cost requirements
Designing around industrial production
Possibly use biological production methods—bacteria producing CNTs or precursor carbon compounds?
Following the work of Harvard professor George Church in synthetic biology
Assemble a list of researchers with facilities that can produce “vendor amounts” of CNT, preferably non-CVD produced
Single wall, double wall – different markets
Rotating assembly? Two carbon chains at a time?
We need a growth model
Hybrids between graphene and CNT for strength?
What are the possible benefits from putting dielectric material inside CNT lattice?
Drawing out tubes uniformly
Can this be aided by electrodynamics?
How does the height of the array affect tangling? Do CNTs tangle as they grow, or is there some optimal length to which to draw out filaments?
Crowd sourcing? With bulk material, we let every high school in Oregon learn to use/make CNTs.
How do we work internationally? There are multiple potential contributing organizations and roles:
CLIMB journal 18 months
Architecture and roadmaps
Japan Space Elevator Association (JSEA)
Academy Study on space elevators
Possible committee opportunity here too
Related treaty experience (Antarctic treaty, Outer Space treaty)
Originally an intergovernmental consortium with a similar goal of providing space-based services to its governmental participants
Has expressed an intent to deploy a space elevator by 2050
Should space elevator research and development be funded commercially, through governments, or both?
Decision would determine applicable legal and social frameworks
Philosophical foundations for international cooperation
What is the objective of building?
Why are we doing it?
How do we manage connect/ disconnect events for climber/tenant
Reserve space on tether – always have it
Maybe have wider tether
Center of gravity and center of mass management
Debris, flux sensors and meteorological shielding
Lasers – avoid satellites with sensors
Coefficient of friction
Dynamics Analysis & Electrodynamics Modelling
Electrodynamic Modelling should be integrated with the mechanical dynamics analysis, even though there will be many more unknown factors requiring different resolution methodologies. Related issues include:
Radiation protection and remediation for passengers and cargo (live animals and other biological material, food & water, medicine, delicate equipment)
Evaluations of shielding solutions
Radiation testing would be simulated initially; lab tests would follow when material or mock-ups become available
Sun pressure on solar sails could cause deflection
Solar wind an issue outside the magnetopause
Compare forces on integrated structure – simulated and experimental
Solar storm could move the FOP
Conductivity of tether could be affected by electromagnetism
Forces and factors that need to be included in the model:
Gravity (from multiple bodies, at least sun & moon)
Rotation of earth
Solar and lunar tides
EM fields—need to develop a comprehensive 3D model of the radiation environment up to 17 earth radii (100,000 km)
Earth anchor location: what happens as the Marine Node is moved?
Tether properties: flexibility, torsional behaviour of ribbon, capacitance, conductivity (electrical & thermal), thermal expansion/contraction, albedo, moment of inertia, …
Could model initially as Zylon (or similar), then change to CNT as properties become known
Need results from historical tether tests
Also, what sort of computer systems will be needed to run the integrated system model? These requirements can be estimated based on benchmark testing of existing tether models.
Conclusions and Highlights
It would be highly desirable to come up with an integrated tool that can combine a model of the tether’s mechanical dynamics with its electrodynamics. These two will influence each other because electric currents induced in the tether will interact with the Earth’s magnetic field. The model of the radiation environment needs to feed through to the tether’s electrodynamics but does not need to be so closely coupled.
Ideas on tether materials included using bacteria or synthetic biology. A summary of active research work and contacts would be useful. Crowd sourcing may make progress; for example getting school-children to experiment with CNTs.
International cooperation could include writing science fiction with positive outcomes. The International Academy of Astronautics (IAA) has set up an Academy Study on space elevators. Bilateral agreements between countries would be a good way to make progress; a global treaty can come later. We need to learn from the Obayashi Corporation in Japan and develop a story to attract other companies.
(Note: During the 2013 Space Elevator Conference, several workshops were held, delving more deeply, with audience participation, into specific Space Elevator related topics. This is a summary of one workshop, Space Elevator Tether Climber.)
Champions: Pete Swan, Skip Penny
Initial Presentation: "ISEC Report Major Points" - Pete Swan
Goal: To stimulate thoughts and inputs from the conference attendees on tether climbers -- involve the attendees...
Outputs: Draft ISEC Report to be available by 15 December - review upon request from attendee or interested party.
30 minute major talk on topic
5 minutes of discussion on handout sheet [stimulation of ideas and areas to discuss]
10 minutes of brainstorming on topics to discuss
45 minutes of brainstorming in small groups [breakups along the lines of the topics to be discussed]
20 minutes of discussions by small groups to large audience on results of brainstorming
10 minute summary
Champion and helper will summarize the results and put on web
Issues: The design of tether climbers in the next twenty years will leverage the phenomenal growth in materials sciences to enable lighter/stronger structures, lighter/more capable batteries, lighter deployable solar arrays, and more energy efficient laser energy devices. The question is what should the preliminary design look like? The 2013 ISEC theme and study will be focusing on these topics and looks forward to the inputs at the conference.
Major Points: Eight different types of climbers described:
Atmospheric [up and down - dock on stratoballoons?]
First 7,500 kms [high gravity]
7,500 to GEO [1 MW power standard]
Micro- to Macro small climbers using the tether [transparent to other climbers]
No such thing as extra power
Anything brought up is valuable
Separation of 3 and 4 above is based upon power needed [from gravitational fall off], but should happen someplace between the major radiation belt altitudes.
Mate climbers to pass payload
Topic: Evolution of Climbers Team: Michael Schaeffer, Sandee Schaerffer, Bryan Laubscher, Peter Stewart
Construction climber needs to build bigger tether capacity [20 MT to 40 to 60 etc]
Second tether prior to commercial operations
Repair climbers are important, from LEO to GEO for monitoring tether health, as well as monitoring debris fields.
Payload climbers should also be able to de-orbit
Astronaut driven climbers must be able to be rescued [detachable, re-enterable]
Low orbit options to include family trips and altitude freefall records
GEO tourist climbers will be much bigger, have plenty of food and be able to reenter
Logical answer would be GEO solar power to climbers
Climbers dedicated to launches to Mars and beyond, with Mars elevators + power projection to surface
Much future is Mag-Lev option with large Apex Anchor [asteroid]
Ring World is reasonable for GEO stations connected
Outer planet moon trips reasonable in the future
Topic: Getting On-Off the Tether Team: Canaan Skye Martin, Bill Rossington, Intchested Amature, David Schilling, Jose Fuentes, Hal Rhodes, Michael Laine
Circular orbits will probably need extra thrust once released
Ellipitical orbits will be from almost any height
One question is how much does the motion of the tether effect the release velocity [vector, direction and magnitude]
Figure out how to coordinate up/down climbers on same tether
On a single strand, to go around another tether, someone must disconnect/re-connect
Below GEO, Stop, then disconnect, then thrusters to enable mission orbit
Most situations are very dynamic, release of climber affects mass on tether
Chaos in launch from dynamics of tether? Could be perturbations due to debris avoidance, releasing and attaching cargo, varying climber speeds and any unpredictable movements.
Topic: Climbers Specialized for Different Altitudes Team: Ben Sibelman, Max Braun, Dennis Wright, Jun Kikuchi, Peter Robinson
There are strong reasons for varying designs of Climbers
Low level climber will probably be driven by laser
Higher speed will come from solar at higher altitudes
Four separate and distinct phases with handoffs between climbers
Each climber goes up, hands off payload, goes back to lower range, picks up next payload
About half the payload throughput of original design
Only four climbers required on tether at any one time... payloads are passed along
To repair of changeout climbers, three high ones come down to lower climber which then loads them as payload and decends to surface.
After proof test of concept, larger advanced climbers can replace original concept and could go from LEO to GEO.
Workshop discussion concluded that four separate optimized Climber designs would be required, but this must be confirmed by a more detailed design and operational study. Provisionally :
Climber 1 for days 1 & 2 would be slow for operation in the high low-altitude gravity field : low speed, high power, laser powered.
Climber 2 for days 3 & 4 would use large solar arrays, with shielding as required for transit through the upper Van Allen belts : medium speed and power.
Climber 3 for days 5 & 6 would use smaller solar arrays : higher speed, lower power.
Climber 4 for days 7 & 8 would be used to finish journey to GEO and beyond : optimized for high speed operation, with lowest-power motors and smallest solar arrays. ( Transit times may mean a 5th Climber would be needed beyond GEO, but this could be identical to the 4th Climber.)
Topic: Alternate Climbing Approach Team: Dalong An [Samuel], Peter Glaskowsky, David Horn, Paul Wieland
New motive approach
Similar to rock climbers in grip
Approaches the tether with gripping motion vs. wheel interactions
Easier to grasp vs. pull oneself up by wheels
Inspired by watching monkeys climb
Less damage to the tether from gripping [brake mechanism] vs. friction from moving wheels.
Idea: A vertical tether is approached from the side by a long loop of strong material.
The goal Sam proposed was to find a way around the need for a wide, thin ribbon tether.
That requirement follows from the usual assumption that the climber must use multiple drive wheels with a high normal force against a wide tether to overcome the disadvantages of a small contact patch and a low coefficient of friction.
Sam had the idea of using some kind of hand-over-hand motion to climb the tether the way a monkey would, by gripping the tether with some kind of clamp and pulling the climber up to the clamp.
We didn't like the idea of reciprocating grippers repetitively passing each other on the tether for the obvious reasons. It seemed to me that we could get similar results without one "hand" passing the other by using a method like mountain climbers use to ascend a rope, with prussik knots (or mechanical equivalents such as the Petzl Ascension) that don't bypass each other.
My suggested solution is to have two "shuttles" above the climber.
A rope (or multiple ropes for redundancy and balance) is looped through all three units, each of which has a tether clamp and a rope clamp.
Each shuttle has a small electric motor and a drive system that can pull it up the tether, carrying only the load of its own weight plus the weight of the rope.
The climber has a motor-driven capstan that can pull the rope, but it doesn't necessarily need any way to pull on the tether.
The rope can potentially be a COTS product; a 2" Dyneema rope is rated at 155 metric tons and weighs less than one pound per foot.
The climbing process works this way:
To start, imagine the Climber is on the ground and the two Shuttles are immediately above it. At this point, there will be considerable slack in the rope.
Shuttle 1 (on top) engages its drive motor and begins pulling itself up the tether at speed 2V (where V is the target speed of the Climber) until the loop of rope is nearly tight.
Shuttle 1 clamps the tether and the rope.
Shuttle 2 unclamps the tether and the rope.
Shuttle 2 begins pulling itself up the tether at speed 2V.
The Climber engages its drive motor to pull itself up the rope at speed V, which cause it to ascend the tether but without applying any force directly to the tether. (That force is carried from the rope to the tether through a Shuttle.) As the Climber comes closer to Shuttle 1, it generates slack in the rope, which hangs below the climber.
Shuttle 2 stops just short of Shuttle 1.
Shuttle 2 clamps the tether and the rope.
Shuttle 1 unclamps the tether and the rope.
Shuttle 1 begins pulling itself up the tether again at speed 2V and stops when the rope is nearly tight.
We repeat steps 3 to 9 to the top of the rope.
Note that the Climber is constantly pulling itself up the rope, stops ascending the tether. Meanwhile, the two Shuttles alternate in pulling themselves up the tether, which is why they have to average twice the speed of the Climber while they're moving. (For practical reasons they will need to travel at somewhat more than twice the speed.)
The side of the rope loop nearest the tether (the "tight" side) remains stationary relative to the tether because at least one Shuttle is always clamped to both the tether and the rope.
The other side of the rope loop (the "loose" side) moves intermittently upward. When moving (when Shuttle 1 is climbing) it moves upward at four times the speed of the Climber, and so will probably need to be managed carefully to keep it from whipping around. When Shuttle 1 is clamped and Shuttle 2 is moving, the loose rope just hangs in place.
So there are some obvious challenges in this system, but perhaps it's still a better solution than trying to drive the Climber directly against the tether. Or perhaps it's only a better solution at lower altitudes where the direct friction drive solution is most difficult to implement.
First, the upper gripper ascends the ribbon with almost no mass and feeds the loop rope[pulls the upper portion of the loop with it] with it as it moves up.
Second, it grasps the tether at a much higher location than the last grasp [length of loop] and holds on
Third, the climber pulls itself up on the rope loop without touching the tether until it approaches the upper grasping mechanism.
Fourth, the lower grasping mechanism moves up with the climber and grasps the tether below the climber to hold it stationary at that point.
(Note: During the 2013 Space Elevator Conference, several workshops were held, delving more deeply, with audience participation, into specific Space Elevator related topics. This is a summary of one workshop, Space Elevator Space Operations.)
Goal: To stimulate thoughts and involve the conference attendees on timely topic
Outputs: Summary Report to be posted on ISEC website in 60 days
30 minute talk on topic, based on paper: status of topic, past history, future approach, technological challenges [as well as legal and other] etc.
5 minutes of discussion on handout sheet [stimulation of ideas and areas to discuss]
10 minutes of brainstorming on topics to discuss
45 minutes of brainstorming in small groups [broken up along the lines of the selected topics]
20 minutes of discussions by small groups to large audience on results of brainstorming
10 minute summary
Champion and helper summarize the results and put on web
Issues: The design of space elevator climbers will require a solid space operations concept developed prior to "kick-off." As such, the identification of the various processes associated with the ground and space operations will require inputs from diverse sources and experiences. This mini-workshop will consolidate inputs and summarize the concepts and proposals for operations during the lifetime of a climber.
Topic: Repair of Tethers
Major Points: Several points were emphasized:
Sever is a real problem and requires much future study, especially with the emphasis on recovery from a sever in the lower reaches.
A partially torn tether will need to be identified by both manual and automated methods. This could be accomplished though IR sensors on each tether climber, or searching the tether by remote means.
The safety approaches for damaged tethers will vary depending altitude.
One concept would be a "sliding 3-D printer" that would move the damaged location and then replace, overlay, or fuse the material needed.
Once the damage is identified, the movement of tether climbers over that spot could be limited drastically.
No answers were expected as this is a serious topic to pursue as the knowledge of the design firms up.
Topic: Down Climbers
The consensus is that there should be dedicated down elevators in addition to the principle mission of vertical lift for profit.
The return climbers should only come down when they have payloads to carry [multiple folded climbers might be one payload]. The cost to come down [opportunity lost on up carrying climbers is the issue]
The descent of climbers will probably be slower than the ascent as the danger of it getting out of control is high. The earth's gravity is pulling the climber and significant braking capability and massive heat dissipation. The concept would be to have a motor using the downward pull to create electricity which could be transmitted to other climbers.
The parachute is a questionable option. It will only work in the atmosphere and the tether/parachute coiling might be an issue.
Topic: Operations with a Strato-station or a High Stage One
Many of the concepts of operations at a high stage one are parallel with the operation of a stratospheric balloon [dirigible] operation.
The height would probably be at approximately 30 km [maybe higher] and the load would be dependent on the capability of the large balloons to stay at altitude.
One effect that will be difficult is the day/night buoyancy issues due to heating of the atmosphere and more vertical thrust when daytime.
Solar power for energy seems natural when you are above most of the opaque atmosphere.
Indeed, the center of mass and flying capabilities will be important during the long periods of operations.
Maintenance issues are real and will probably drive one to two strato-stations to ensure 24/7/365 coverage.
There could be telescopes on the strato-station for science as well as to look for space debris and help in identifying potential tether threats.
With the flyability of the stratospheric balloons, the tether can definitely be moved for dynamic motion to avoid space debris.
High Stage One seems to have a good handle on these issues and looks like a very good stationary platform to work automated machinery to operate the Earth's terminus for tether climbers and other activities.
Topic: Diagnostic Discussions
Team: Larry Bartoszek, Sandee Schaeffer, "Sam" Dalong, Vern McGeorge, Jose Fuentes
Major Points: Types of diagnostics needed for a tether climber:
During the braking, the heat sensors must look for overheating problems, not only at the source, but as it moves. This could be bearings, wheel surfaces, ribbon surface, battery/capacitive packages, motors, and especially brakes.
Cameras should be in many locations as monitors of the action motion and activities.
The ability to center on the ribbon will be crucial. Many types of sensors could achieve the desired result during high speed climbs, but optical will be principle. Some of those would be on Non Destructive Inspection methods such as X-ray, gamma ray, light density measurements, and, of course, counting cross bars or other height locator items.
There could be radar required on-board.
There should be sensors for impacts from space objects and to detect dynamic motion that is unexplained or actual holes in tether.
Radiation sensors are probably required as the issue is real and changeable.
Electrical sensors for current, voltage, capacitance, and stray EMF's. The sensors should be measuring levels and looking for anomalies such as spacecraft charging.
There should be strain gauges on the high stress items such as the wheels and pressure structure.
GPS can be very valuable for location, speed, and acceleration.
The payload needs environmental sensors to monitor the environment. When the payload is people, these requirements become serious.
It seems that streaming video is a common request - thus probably a customer need.
The preliminary meeting of the ISEC Marine Node team was conducted as a mini-workshop at the 2014 Space Elevator Conference in Seattle. We had a fantastic discussion on the development of the Marine Node, identifying and exploring multiple topics that are essential for making progress on this key element of a space elevator system.
Marine Node Overview
Dr. Peter Swan, acting as workshop leader, presented the following graphic for the Space ElevatorMarine Node.
The image shows two Marine Nodes, each consisting of a single Floating Operations Platform. The platform in the foreground is shown with a support vessel alongside. The Marine Node may also include an additional Facilities Support Platform. Another key element, the port facilities to support the node, is not shown.
Workshop participants discussed five parameters of proposed locations: ocean currents, sea water status and makeup, sea floor geology and seismology, and weather conditions. Obviously, these are just some of the parameters of interest. Attendees also participated in a brainstorming process to develop new concepts and ideas for the Marine Node.
Workshop Goals and Processes
The goal of the mini-workshop was to develop a description of the Marine Node and show how to move towards operations, driving innovations in node design and lowering development risk.
Define the Problem. The questions presented to the workshop participants included these:
Where should the Marine Node be located?
How many platforms should be provided for each node?
What are the characteristics and requirements of the tether connection?
What resources are required to meet the throughput goals of the node?
What are the security concerns for the node?
What businesses can operate at the node?
Build on the Marine Node baseline. Over the last few years, there have been multiple solutions proposed to the problem of how to develop a space elevator Earth anchor, including these:
Dr. Edwards' baseline: Single tether, middle of Pacific, oil rig, laser powered
IAA baseline: Multiple sites with paired tethers and solar-powered climbers
Keith Henson's proposal: Marine nodes 8° south of the equator, angled tethers
Japanese proposal: Floating tunnel to island-based surface node, 100 MT tethers
The team looked at these proposals and considered the positive and negative aspects of each to enable progress forward.
Make specific proposals. The following discussion notes are the product that the team developed in the mini-workshop. They comprise three elements:
Definition of functional needs to be fulfilled by Marine Node.
Presentation of multiple solutions to the needs.
Description of the "best" solutions available today or in the future. This set of descriptions should enable future designers to leverage our comparisons and understand our engineering trades.
From the teams at separate tables, discussions developed observations, ideas, proposals, and preliminary conclusions in several areas:
Loading due to tether
The tether anchor must counteract an upward force of less than 500 tons.
High Stage One provides 25,000 tons of down-force.
For the case of an off-equator tether (4 to 8 degrees south) the tether will be roughly 20 degrees from vertical, leading to significant transverse forces of about 100 tons.
Fuel for marine thrusters required for station keeping at surface node, but not for high stage one
The logistics stream from tether base to main base of operations
The team considered ports in Hawaii, South America and Panama
Distance from port:
Locating the platforms 200 miles from a major port is considered practical
A position 1,000 km west of Galapagos would be more difficult to support
Food, fuel are significant components of the consumables requirements
several tugs will be needed
Docking facilities will be required at the platforms
For the more distant platform locations, for example 1,000 km west of the Galapagos, only a few helicopters exist with sufficient range to reach major medical facilities.
E.g., the AH-56A, Mi-26, V-22, etc.
Should we rely on Navy carrier groups for medical and evacuation?
Sufficient on-site medical could be developed - it is scalable from existing offshore operations.
Moving the platform in case of storm, orbital debris, etc.
It may be necessary to move the tether platform as much as 50 miles.
A 100-ton tug would be sufficient to provide the necessary movement.
How quickly could the base be moved? Assuming base is moored to sea floor, a few hours to drop moorings and get underway. A 100-ton tug could move the platform at a speed of 2-3 knots. With integrated submarine propulsion, a speed of 10 knots may be possible.
Movement available at top of High Stage One is 20 - 30 km.
An off-equator platform could be moved by reeling the tether in or out.
Seismic loading from sea floor.
There is little seismic activity at nominal location and sea floor depth of 8,000 ft.
Additional features and functions
Likely new OGVs (Cruise Ships?)
Greater storage capacity (climbers and payloads)
Larger numbers of operations and support personnel
Keep-out zone (safety and security)
Greater movement capability, possibly faster
Larger operations center
More in-depth weather (and ocean) monitoring/sensing
Climber mating equipment
Greater power generation (4 MW for climber)
Power cord handling equipment
Climber refurb facilities
16 MT per day throughput
48 MT storage - preparation
48 MT storage - waiting movement
Climber Repair Modules - storage and preparation
The mini-workshop defined and discussed many potential problems and solutions for the space elevator Marine Node. The conference attendees became actively involved in the discussions and ideas flowed freely, achieving progress in the conceptual development of the Marine Node.