A Lunar Robotics Testbed - Abstract
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A Lunar Robotics Testbed
Individual Mission Plan
Dr. Wallace T. Fowler
Department of Aerospace Engineering
The University of Texas at Austin
May 9, 1993
During the 1980's there was much talk in the US, and around the world, about the prospects of exciting large scale manned space exploration missions. During that time the US was in an economic boom and it seemed very likely that we would soon have a manned orbiting space station, that we would establish a permanently manned lunar base, and that we could even send a crew to Mars and return them safely to Earth. Now, in the 1990's, in the early stages of recovery from and economic recession, we see that we can no longer afford so many large scale missions all at one time. We have learned from the Space Shuttle and Space Station Freedom that such large scale programs are slowed down, redesigned and possibly even canceled because of the extremely large amount of funds necessary over many years. By Congress reassessing the programs' budget every year the projects drag on for years, losing public support and gaining scrutiny, while draining funds from smaller less visible projects.
As a result, in an effort to reduce costs while advancing technology and building a large success rate, NASA has been directed to carry out much smaller individual faster-paced missions. Thus instead of developing many technologies under one large program, like those necessary for a manned Mars mission, much smaller programs with identifiable affordable price tags and relatively short timelines should be carried out. It is not suggested that we abandon the ideas of large scale nature, just that we abandon the idea of developing them all at the same time under one program. It is too late to apply this method to the space station since its fate will be determined shortly. However, if the US is determined to expand the presence of man in space we should plan now to refocus our efforts on how to attain our other major goals: a manned lunar base, and a manned mission to Mars.
Many technologies necessary to complete these missions efficiently and safely need much further development. These include: long-term micro-gravity effects on humans, time lag in communications, and telerobotics, just to name a few. These technologies can be advanced individually under smaller programs with better defined objectives. By developing the technologies in single steps we can more quickly reap the benefits while working toward an ultimate goal. This paper describes a mission that takes the first step in furthering manned exploration.
Lunar Robotics Testbed
It has been determined that for any of the lunar base concepts proposed, robots will somehow be employed in the construction, maintenance, repair, mobility, or environmental protection of the base. The logic in this assumption is simple: the more that can be accomplished without manned presence, the cheaper the mission becomes. For example, if a robot can perform functions, such as filling bags of lunar soil for radiation protection or repair a solar array, the astronaut is not needed for these tasks thus reducing the cost of the mission by orders of magnitude. It would not be necessary to factor in special space suits, life support systems, astronaut fatigue, etc. Thus if a base was completely established and maintained roboticly the astronauts time could be used more efficiently for scientific endeavors.
The major problem with this scenario is that robotics technology has not yet advanced to the level required for such tasks.
The major function of robots today is in automation; performing tedious or repetitive tasks with a high level of precision. These tasks typically include spot welding or spray painting, as used in the manufacturing of cars, and are controlled by programming. Autonomous robots perform the same task over and over and do not allow for interactive control by humans. Although automation will certainly have a place in the establishment of a lunar base we would also like to be able to instruct the robot to perform various (possibly one-time only) tasks.
This sort of control is commonly known as telerobotics, where the device extends human senses or dexterity to a remote location. A human operator sees, feels and controls the remote task through the teleoperator thus eliminating the need of human presence at the remote location. This two-way communication merges the benefits of mechanization and human intelligence . Due to the three second time lag in communications between the Earth and the Moon total reliance on telerobotics becomes impractical. Therefore for lunar applications we would like to merge these two types for optimum performance; a telerobot which would have some level of autonomy to perform various preprogrammed tasks (such as filling bags with lunar soil), as well as the flexibility to perform more detailed tasks that require human supervision (like replacing or repairing a solar array.) This leads to the definition of the proposed mission.
Proposed Mission Concept
In the spirit of advancing technology under small scale, relatively cheaper and faster programs, a series of lunar robotic missions is proposed. The overall goal of these missions is the advancement of telerobotics technology. More specific goals are to:
- test precision of telerobotics versus pure automation
- est various methods of control (possibly use virtual reality)
- test durability of space robots in harsh space environment
- gain experience in telerobotics technology (especially in space)
The concept is to send a series of relatively small payloads (200 - 300 lbs) to the lunar surface via a current launch system. Each payload would consist of two identical micro-robots attached to a common platform. The platform supplies the rockets and propellant used for lunar transfer and landing, as well as the major communications link to the earth. Shortly after landing the robots would detach from the platform and begin their tasks. The robots would be required to perform identical tasks; this provides researchers with twice as much test data as well as a redundancy should one of the robots become incapacitated.
Some future expectations on telerobots for lunar base activities are classified by the following general tasks :
- soil excavation/movement for site preparation
- module/node/tunnel/garage transportation, handling and interconnection
- structural assemble and disassembly
- module protection and materials processing
- remote repair and maintenance of nuclear power plants
For some of these tasks autonomous systems will be sufficient, but total reliance on autonomy is impractical due to the difficulty in providing the protocols and procedures necessary to handle all abnormal situations. Similarly the robots cannot rely on pure telerobotics due to the three second time lag in communications; the robot could cause permanent damage during fault detection and correction procedures. Thus the robot must effectively employ the advantages of both telerobotics as well as autonomy.
CSR/TSGC Team Web