|Title: Space Elevator Climber|
Ascending the ribbon efficiently and reliably is crucial. The climber utilizes current technology throughout and is under development through the Spaceward Foundation Space Elevator Games.
|Mass||30 tons||Baseline mass has been 20 tons (13 payload and 7 climber) but larger systems are being considered. Initial climber mass breakdown File:Climber mass.ods|
|Height||20 meters||Only roughly determined at this time. Height will be determined by stability and tracking studies.|
|Width||20 meters||Determined by photovoltaic array size|
|Payload||60 tons||Baseline mass has been 20 tons (13 payload and 7 climber) but larger systems are being considered|
|Maximum Velocity||200 kph||This limit was set by the state of current technology with no maturation. This rate is likely too slow for many human transport applications.|
|Power usage||10 MW||Determined by maximum velocity expected and capabilities of lasers adn receivers. This power delivery is larger than listed as baseline in the past to account for the larger climbers being considered.|
|Motor||DC electric||Various designs are possible. Brushed, rare-Earth motors regularly run at 90% efficiency. Issues come in the variable speed and power required, operation from atmospheric pressure through vacuum and thermal issues.|
The working climber design is File:Climber model.dxf. Notes on the design are located [climberdesignnotes.odt here]
In the grand Space Elevator scheme of things, climbers can be easily identified - they are the things that move. The climber moves up (and possibly down) the stationary Space Elevator ribbon, carrying payload with it.
A picture of the climber is shown below:
Climbers have 3 main parts:
- A beam convertion system, which captures incoming light and converts it into electricity
- A traction and drive system, which uses the ribbon to propel the climber
- A hull, which encoumpases all of the non-climber related functionality, such as attitude control, communications, and life support. **NEAD A TERM FOR THIS**
Since only the first two systems are unique to the Space Elevator, they usually get most of the attention, since we think we know how to make a space-worthy hull. This is a common misconception, since so very much of the way spacecraft are built, down to even the basic choice of construction material, is goverened by the fact that they are designed to sit on top of rockets.
Most recent work on climbers has been done in the framework of the Space Elevator games.
These climbers demonstrate the basic principles of a Space Elevator Climber, since they contain all the basic functionality, but they do not really have a direct lineage to real spaceworthy climbers.
Full article: Climber Traction Mechanism
The traction mechanism has to be developed along with the Ribbon Macro Structure and it is likely that the considerations that go into the development of the latter will override those that define the former. In short, the traction mechanism will be built around the ribbon, and not the other way around.
It is possible at this point, however, to start considering how to handle very fine ribbon at high speeds in a way that is safe. The traction system is the #1 candidate to break a Space Elevator.
See Climber Traction Mechanism Workpage for more details.
Full article: Climber Power Conversion System
The power receiving unit has to be deloped along with the Power Beaming Source. The receiving unit has to be both lightweight and efficient. A 20 ton climber will be expading 10 MWatt when traveling at even 50 m/s, and any inefficiencies create heat that has to be ratiated away, which introduces mass penalties. Current space power systems are in the 100 kWatt range, two orders of magnitude below what we plan to have.
At this point, we should be looking at the range of PV alternaives out there, since it is a rapidly evovling field.
In propulsion terms, the overall climber must a thrust-to-weight ratio of 1! This a tough requirement.
See Climber Hull Workpage for more information
Current Climbers at the Space Elevator Games http://www.spaceward.org
Include images and videos from the SE Games Include design write-ups
Alternative designs and concepts for a climber can be found at ArchiveSchematics and ArchiveDesigns
Major Development Issues Related to this Component
Additional Work Needed
The climber has the most engineering work that needs to be done and the most opportunity for individuals and groups to get directly involved.
|Item||Notes||Completed and Ongoing Efforts|
|Categorize the available photovoltaic cells for use with the power beaming system||Baseline climbers are designed to use photovoltaic cells to receive power from lasers at Earth. The specifics of these PV cells are critical to understanding the performace of the climbers. PV cells are being heavily researched and such the best are constantly changing. We need someone to compile the information on the best cells for power beaming - receiving light at a specific wavelength. They need to be light weight with high efficiency around 1 micron. Who is making them, mass, cost, efficiency spectrum,coatings to improve them at our wavelength, output,... Also, in case Ben Shelef's solar design works out we need as much information on the ultralight arrays as well.|
|Categorize the available motors||Recently I have been working on various small motors and finding that there are numerous possibilities for off the shelf motors that may work for the climber. In addition a custom motor or a modified commercial one promises to have even better performance. The motor is the major mass component on the climber - getting the right one is crutial. It must be in the megawatt range, high efficiency, torque at zero RPM, operate in a vacuum, and be geared to meet the climber needs. For a motor engineer, mechanical/electrical engineer or just a good hardware person this is an open area where you have a blank sheet for designing a motor and seeing how it compares to commercial systems.|
|PV array design||In the Space Elevator Games we have seen lightweight solar arrays literally get torn apart on the ribbon. We need to examine the best way to make an array that is lightweight but strong. Composite frame with tension members? A rigid sandwich panel? an organic type structure looking like a inverted tree? We need need innovation. Optimize for collection, efficiency, mass, use in unidirectional -0.1 to +1 gravity,...|
|Roller design||If you've ever seen newsprint flying through a printing press then you have seen what we need - rollers that handle thin material at high speed. It must track the ribbon and hold it securely without damaging it. The added challenge is that the system must be low mass, operate with what may be a low-friction ribbon, apply minimal variation in force across the ribbon, and the forces will be tons per roller drive, ... not a small system but precise. This one can be designed and built for testing. An initial set of offset canted rollers I (Edwards) designed and a colleague built took a ribbon, held it and tracked it even when it was aggressively pulled off to the side (a colleague wanted to prove it wouldn't work - he apologized for a week for doubting me)|
|Overall structure design||Innovation, artistry and a bit of engineering and you get to design the coolest climber ever. Many climber designs look functional - we are still at that stage - but now is the time to analyze where the forces and masses will need to be on a climber and build a structure to best suit it, minimize vibrations or roll with them, aid in tracking, keep the array aligned,... and do it for as little mass as possible - maybe a CNT gossamer structure?|
|Operations||Before we build it we will need to know how we will run it - how much mass is going up, how often do we launch, if a climber fails what do we do, what is the ascent speed profile, how much time do we have to load climbers, do we bring climbers back down when they are done, do we toss them when they reach their destination, do we scavenge climbers for parts, how many people do we need at the anchor for loading climbers or on the mainland scheduling, ... We need someone to start working out a detailed operational scenario|