A group of students from the University of British Columbia (UBC) is working to develop a robot prototype that will be the basis of a proposed commercial space elevator that would eventually provide transport to and from space at around 5% of the cost of current methods (see the figure). The prototype is being developed for a space elevator design competition sponsored by NASA. UBC’s Team Snowstar is competing against 19 other teams from around the world in the 2006 Space Elevator Games, which will be held at NASA’s Ames Research Center in Mountain View, Calif., in August.
Teams entering the challenge must provide an autonomous, intelligent space elevator robot to climb a cable. The robot must be powered wirelessly from a ground-based power beaming station. Teams also must design and build a power beaming mechanism to power the climber.
According to the Spaceward Foundation, the space elevator concept is based on a thin ribbon, with a cross-section area roughly half that of a pencil, extending from a ship-borne anchor to a counterweight well beyond geo-synchronous orbit. The ribbon is kept taut, due to the rotation of the earth, and that of the counterweight around the earth. At its bottom, the ribbon pulls up on the anchor with a force of about 20 tons.
Electric vehicles, called climbers, ascend the ribbon using electricity generated by solar panels and a ground-based booster light beam. In addition to lifting payloads from earth to orbit, the elevator also can release them directly into lunar-injection or earth-escape trajectories.
The baseline system weighs about 1500 tons (including counterweight) and can carry up to 15-ton payloads—easily one per day. The ribbon is 62,000 miles long, about three feet wide, and thinner than a sheet of paper. It’s made out of a carbon nanotube composite material.
The climbers travel at a steady 200 kilometers/hour (120 mph). They don’t undergo accelerations and vibrations. Also, they can carry large and fragile payloads. No propellant is stored onboard.
Orbital debris is avoided by moving the anchor ship, and the ribbon itself is resilient to local space debris damage. The elevator can increase its own payload capacity by adding ribbon layers to itself. There is no limit on how large a space elevator can be.
At the heart of Team Snowstar’s design is a host of MCUs and development tools from ZiLOG Inc. The company supplied its eZ80Acclaim!, Z8 Encore! MC, and Z8 Encore! 8-bit MCU solutions and development kits, as well as consultation and technical support.
The eZ80Acclaim! MCU will act as the central controller for the robotic vehicle. It will provide the main communications interface to the ground to complete the beam control feedback loop. MCUs from the Z8 Encore! family will control subsystems and monitor the photovoltaic cell array, which powers the unit. A microcontroller from the recently launched Z8 Encore! MC family will work to control the brushless dc motor, which will be used to climb up the cable.
To find out more about ZiLOG’s portfolio of MCUs and development tools and software, log onto www.zilog.com.
Further information on Team Snowstar can be found at www.snowstar.ca.
For more on the Space Elevator Challenge, check out www.elevator2010.org.
Find out more about the Spaceward Foundation at www.spaceward.org.