How JPL Modeled and Tested Pieces of the Rover Curiosity

This onboard view shows MSL’s successful separation about 45 minutes after launch. At this point, Curiosity had a long, cold transit ahead of it. Photo Credit: NASA TV

On Tuesday, attendants at the 2012 Farnborough International Airshow in England will get a chance to hear from two representatives about a very interesting partnership. Director of NASA’s Mars Exploration Program Doug McCuistion and CEO of Siemens Industry Sector Siegfried Russwurm will discuss Mars, the importance of the space program, and the role cost-efficient product development will play in the new era of space travel and exploration.

McCuistion and Russwurm will give details on the Mars Science Laboratory (MSL) mission. They will also answer questions about the importance of a collaboration between government and industry in space exploration as a way to maximize productivity and efficiency. Both organizations collaborated on MSL’s successful development.

MSL’s payload, the rover Curiosity, is scheduled to land in Gale Crater on August 6 this summer. It’s the fourth rover NASA’s sent to Mars and the most complicated. It’s a mobile laboratory designed to determine whether Mars, specifically the area around Gale, ever had conditions favorable for life. Curiosity will use its robotic arm to drill into rocks and scoop up soil and deliver samples to internal instruments for analysis.

It isn’t just Curiosity that’s making MSL a complex mission. Its flight system is the most complicated that NASA’s Jet Propulsion Laboratory (JPL) has implemented, requiring new technologies and a new approach for entry, descent, and landing.

The rover’s power source was another major design challenge on this mission. Curiosity uses a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) that constantly generates a substantial amount of heat. The rover’s larger size doesn’t help; it means the MMRTG dissipates more heat than the power systems on smaller rovers. Excess heat, or heat runoff, is a problem JPL solved by adding more capability to the heat rejection system.

A 3D color-coded model of Curiosity. Image Credit: NASA Goddard

The heat rejection system is an instrumental piece of hardware that will protect MSL from the wide array of temperatures it will experience during the mission. During its interplanetary cruise, temperatures will be about -456 degrees Fahrenheit (2 degrees Kelvin) before jumping to 2,637 degrees F during atmospheric entry. On the surface, temperatures are expected to range between -211 to +122 degrees F.

To deal with these temperatures, Curiosity’s heat rejection system is designed to perform both heating and cooling functions. It includes all the typical thermal control hardware (heaters, thermostats, thermal control coatings and thermal blankets) that maintain the payload and the spacecraft subsystems at a safe temperature for all operating modes throughout the mission lifetime.

In developing the mission and the thermal control system, JPL used Siemens’ NX software as its design platform to simplify the process.

NX is a digital product development system that addresses the full range of development processes in product design, manufacturing, and simulation. A complete suite of integrated process automation tools gave JPL fully integrated computer-aided design, computer-aided engineering, and computer-aided manufacturing systems that JPL used to develop the mechanical portions of the MSL.

JPL modeled the entire MSL mission using NX, digitally assembling and modeling the rover, as well as its cruise and descent stages. To address the thermal aspects of the mission, JPL used the NX model to simulate a variety of physical effects, such as fluid flow in the Mars rover, heater control of the propulsion system, and solar loading of the cruise stage. NX also enabled integration between different types of analysis, such as thermal and mechanical distortion and stress analysis simultaneously.

These tests gave engineers the data they needed to adjust and perfect the hardware, including the thermal regulation system. Design updates were immediately integrated into the NX model, saving time to ultimately allow JPL to stick to its schedule with MSL. Furthermore, NX model tests negated the need for physical testing and allowed engineers to run tests they wouldn’t have been able to simulate.

The real test will come when MSL reaches Mars, sets down the rover, and it gets to work; then engineers will see the results of their computer-modeled testing. But so far they know that thanks to NX the MSL program had less manual work and more efficient modeling and simulation interfacing compared to any previous rovers.

2 comments to How JPL Modeled and Tested Pieces of the Rover Curiosity

  • Michael Harleman

    How much actual physical testing of the system was done prior to launch? Has just about all testing only been done by computer models? If so that’s pretty impressive if the rover’s descent to Mars actually works. I’ve seen videos of what they expect to happen as the rover approaches the ground. Are you saying that they used a completely computer generated manufacturing system to create the rover or does that mean that while human hands were used to build it, NX is responsible for engineering and simulated testing of the rover and all it’s necessary functions?

  • Jeff

    During its interplanetary cruise, temperatures will be about -456 degrees Fahrenheit (-2 degrees Kelvin) […]

    Two small problems: there’s no such thing as “degrees Kelvin”, and the Kelvin scale represents absolute zero as 0 kelvin, so -2 kelvin doesn’t represent any real temperature!

    The equivalent of -456 degrees Fahrenheit is actually about +2 kelvin.