Delivering fast for the Red Planet

4 min read

Tom Shelley meets the man responsible for a crucial part of the Mars Rovers and learns how innovative software helped get the job done in time, and his beliefs on why the human race has to keep undertaking such projects

The robot arms on the Mars Rovers, which unfold to support the instrument pack which grinds off areas of rock and then analyses them, had only six months to get from concept to production with a team of seven engineers and one manager. These people, who also had to deal with the NASA bureaucracy and various suppliers and subcontractors, were able to swiftly deliver working product that could never be repaired in service, thanks to the development of a process based on souped-up PDFs. There is no environment on the surface of earth as severe as that on Mars. Temperatures drop to -120 deg C, dust storms can reach hundreds of miles and hour, and delivery involves being bounced around on a dusty, rocky surface over around 1km distance, suffering a series of shock loads starting at 42g. The design and manufacture of the arm was contracted out by NASA's Jet Propulsion Laboratory to Alliance Spacesystems, based in Pasadena. The director of engineering there is Brett Lindenfeld, a former JPL employee. The specifications for the arm included: five degrees of freedom and support for a turret with three instruments and a rock abrasion tool to grind clean patches on rocks that the instruments could be used to examine. It had to fold up to within a small space, but be able to extend to more than 1m at the same time as weighing only 4.2kg. Accuracy had to be {{plusminus 5mm}} and repeatability {{plusminus 4mm}}. Each joint was unique, and 220 electrical signals had to make their way across them. The system had to be able to survive a temperature range of -120 deg C to +110 deg C and work within the range, -70 deg C to +45 deg C. Slip rings to transfer the signals were at once ruled out and as Lindenfeld said, round wire becomes too stiff at low temperatures. The solution adopted to transfer signals was to use flex cables, with loops at each joint, and 'S' bends at the shoulders. There are eight of the these in the adopted design, each with two to four layers, all designed using the Solid Works Sheet Metal module. Overall, there were 300 SolidWorks drawings, each requiring six approval signatures per drawing, with five months to document, review and approve the design package and start fabrication. Using what Lindenfeld described as the "Traditional JPL production cycle", this would have required four meetings and the three sets of drawings for each of perhaps as many as 300 design iterations. Clearly, the traditional approach was not going to get the job done in time, and it was going to be necessary to collaborate electronically. Since many of the collaborators did not use SolidWorks, the solution adopted was to devise novel PDF files capable of being read by Adobe Reader 6.0. The new facility, which has since been spun off into a new company called Bluebeam Software, displays accurately scaled drawings with correct line widths. Digital text stamps help maintain draft revision control and hyperlinks are incorporated into design notes. By using the file attachment facility, solid models and other data are directly embedded into the PDFs. Approved drawings are signed off with digital signatures. ASI has also developed a dedicated workflow tool to control configuration and drawing release based on Bluebeam. Lindenfeld said that "Based on my experience at JPL, using electronic collaboration easily achieved a five to tenfold time saving over their traditional working methods." For anyone else wishing to follow the same path, Bluebeam CEO Richard Lee told Eureka he was prepared to supply the software at $249 for a one off, coming down to $100 per seat for installations with 10 seats or more. Benefits for all There are those who argue that space technology is not relevant to the needs of the human race. Apart from the fact that we may one day be sending robot probes routinely to asteroids, to look for things worth mining, asi has also developed other products based on their space oriented technology and design philosophy. As a result, a Gas Pipe Explorer can crawl along the inside of underground 4 inch pipes, and a RockerCam 3 axis gyro stabilised platform helps Hollywood film makers produce better car chase sequences. Spinoffs from the space industry generally have been much more than the often cited technologies for shape memory alloy bras and non stick frying pans. In Lindenfeld's opinion, "Most of our IT industry is based on the early US space program. Modern computers are born out of the need for on-board processing for the Lunar Command Module and Lander and their communications infra structure. "Without the various space programs, we would have no idea of the true extent of global climate change or what was causing it. Nor would villages in remote parts of Africa be able to be put in touch with the rest of the world through satellite based Internet, telephone and television services. By making the world smaller in this way, the human race is brought closer together into the realisation that we all going to have to work together to survive, let alone prosper. "Lately, transfer to industry has been less because of the significant amount of research and development in the commercial sector. You will now find that the chip in the average hand held is more advanced than those used in the US space program. In recent years, we have stagnated. The only way we are going to get out of our present technological rut is to have some really ambitious programs to push us in new directions. The barrier to these is that we are going to once more have to be prepared to take risks." Asked if going to Mars represented the limit of his vision, it became quite clear that he was thinking of mankind going very much further, but as he said, to do this, "We need some solid breakthroughs in physics." We then briefly discussed Showan's reactionless emdrive (Eureka December 2002) and possibilities that might arise from some of the more bizarre recent discoveries in modern physics. Eureka brought up entanglement and other hitherto imperfectly explained quantum effects and Lindenfeld brought up the discovery that the speed of light can in some circumstances, be varied. We agreed that these possibilities urgently needed to be properly investigated if only for their own sake. As he said, ''All possibilities need to be investigated because the act of discovery is unique. You don't know what you are going to discover unless you look and you don't know what else you might be able to use it for until you find it." SolidWorks is one of the companies expected to exhibit at this year's SolidModelling 2004 show Alliance Spacesystems Bluebeam Software "Using electronic collaboration easily achieved a five to tenfold time saving over their traditional working methods" Eureka says: Pushing the frontiers of space research continues to generate unexpected spinoffs. Pointers * New software makes use of the capabilities of latest generally available PDF format reader to greatly speed engineering collaboration * It is just the latest in a long succession of spinoffs from space research which more than justify the effort and expense