After two failed Mars missions, NASA wanted to make sure the Phoenix Mars Mission would succeed in providing insight to important scientific questions concerning water and climactic conditions, and whether the martian arctic can support life.
The researchers needed to develop a small, but vital part of the scientific project: a wind sensor for the Phoenix Lander's meteorological station mast. NASA called the University of Aarhus, where researchers relied on Autodesk Inventor to overcome extreme design challenges in order to develop a sensor that would help scientist track martian winds, provide new insights into martian weather patterns and ensure that the Lander collected samples under optimal conditions.
Not only did the sensor need to survive extreme forces during lift-off and landing, it had other strict requirements. Named Telltale, after wind indicators used on sailboats, the sensor had to be extremely sensitive, yet incredibly strong and light — weighing no more than 20 gm. It also had to withstand a horizontal load factor of up to 120 times gravity and a vertical load factor of 100 times gravity. Compounding the challenge, Telltale's natural frequency had to exceed 200 Hz. Because scientists expected the sensor to be exposed to extreme vibrations, it needed to be exceptionally rigid. Finally, the Telltale sensor had to be entirely mechanical because it would not be connected to the Lander's electrical network.
Autodesk Inventor helped the researchers of the University of Aarhus meet all of NASA's strict parameters. Inventor provided the team with a complete set of 3-D modeling and mechanical design tools for producing and validating digital prototypes. With the Inventor 3-D digital model, the University of Aarhus scientists could visualize, simulate and analyze their Telltale sensor designs under Mars-like conditions.
“We made a design interface in Autodesk Inventor based on the maximum weight requirement of 20 grams and its need to be located atop the mast,” says Henrik Bechtold, from the Dept. of Physics and Astronomy at the University of Aarhus. “Then we developed the first prototype along the lines of a telltale used on sailboats.”
When the first prototype didn't pass vibration tests, the University of Aarhus scientists looked to Inventor to refine its design. Inventor allowed them to calculate the natural frequency of the 3-D model, optimize the design, revise the prototype and subject it to additional tests.
“We were really impressed that Autodesk Inventor's calculations were so close to the results we obtained with the physical prototype,” says Bechtold. “Even though we always test such equipment in a physical environment, the design process was far quicker and more efficient because we could get the design right before physical prototyping.”
Two University of Aarhus researchers — Haraldur Pall Gunnlaugsson and Christina von Holstein-Rathlou — have been stationed at mission control in Tucson, AZ since the Phoenix Lander touched down on May 26, 2008. They report that the Telltale wind sensor is providing all data as planned and helping researchers accurately calculate wind conditions. As a result, teams managing the robotic arm that collects samples from the Red Planet are able to schedule their missions when wind conditions are optimal — and protect the Lander's sensitive instruments.
So far, the data collected has proved intriguing. “This is the first time analyses have been made so close to the martian poles, and the results of the geological tests are very interesting,” says Gunnlaugsson. “We have run into ice just a few centimeters under the surface dust layer. And thanks to the Telltale sensor, we have measurements that give us a good idea about how winds vary throughout the day.”