SIMCENTER (stories)

Product: FEMAP, Simcenter
Industry: Aeroespacial

Siemens Digital Industries Software solution helps Almatech optimize unprecedented high-performance, lightweight component designs

Using Femap makes it easy to reiterate the simulation process.

Dr.Luc Blecha,CTO Almatech

Top precision and maintenance free reliability

To boldly go where no human has gone before was the mission of the starship Enterprise. Its aim was to explore strange new worlds, to seek out new life and new civilizations. While manned space voyages of this magnitude remain fictitious, mankind is sending out space probes to achieve these goals.

During their deep-space missions, typically lasting several years, the satellites are exposed to extreme environmental conditions. These include temperatures ranging from −160 °C to more than 350 °C and acceleration forces amounting to several g as well as high levels of various kinds of radiation. At the same time, there are no gravitational effects such as thermal convection. The on-board instruments and associated fixtures require high precision and operational reliability.

“Although they are optimized for minimum weight, their stability and functionality need to be sustained over several years without any maintenance or cleaning,” says Dr. Luc Blecha, chief technical officer (CTO) of Almatech. Employing 25 scientists and engineers, the company based in Lausanne, Switzerland, develops lightweight structures and mechanical solutions for exceptional requirements such as high precision and reliability in harsh environmental conditions. Almatech is frequently involved in the design of components for spacecraft programs of the European Space Agency (ESA).

Structural components for outer space

Scheduled for launch in late 2019, the Characterising Exoplanet Satellite (CHEOPS) will observe individual bright stars that are known to host exoplanets. It uses a photometer on its telescope to measure the dimming of the starlight caused by a transiting planet. It will provide scientists with the high-precision transit signatures that are needed to measure the sizes of small planets. This data will provide key insight into the formation and evolutionary history of planets.

As part of the Swiss-managed CHEOPS project, Almatech was in charge of all the structural components. The task involved the design and construction of the tubular main structure made of carbon fiber reinforced plastics (CFRP) as well as titanium brackets and the junctions holding the primary and secondary mirrors. The mirrors cannot be adjusted in flight, so their support needs to be rigid and have high stability over the range of temperatures experienced in space.

BepiColombo, a joint European and Japanese mission to Mercury, is already on its way to our inner neighbor. Launched in October 2018, it will start orbiting the least understood planet in our solar system in late 2025. The mission comprises two spacecraft: the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (MMO). While gathering data during its one-year mission, the MPO will endure temperatures in excess of 350 °C.

Almatech designed and optimized a baffle that protects the MPO against heating to more than 270°C. It also protects the laser receiver of a built-in altimeter against the heat coming from the sun. The components included a very fine aluminum mirror used to deflect rays of sunlight. “The shape of this mirror was given, the tolerable roughness was specified at 4 nm, regardless of any external influences,” says Blecha. “By comparison, the diameter of one aluminum atom is 0.25 nm.”

The Solar Orbiter is a collaborative mission between the ESA and the United States’ National Aeronautics and Space Administration (NASA) to study the sun and its outer atmosphere. Scheduled for launch in 2019, the spacecraft will observe the sun’s atmosphere and combine these observations with measurements taken in the environment surrounding the orbiter. It will provide insight into fundamental physical processes studied under conditions that are impossible to reproduce on Earth and unfeasible to observe from astronomical distances.

A Spectral Imaging of the Coronal Environment (SPICE) instrument aboard the Solar Orbiter will observe both the solar disk and the corona to characterize plasma properties at and near the sun. For this instrument, Almatech designed a slit-changing mechanism. It moves the shutter by deforming parts rather than sliding along guiding tracks. “This is vital because particles created by abrasion would over time disable the optical instrument, and cleaning is impossible,” says Blecha.

Testing the digital twin again and again

For many parts, Almatech’s role is to optimize existing designs. The CHEOPS telescope structure, for instance, needed to be reduced in complexity and weight while retaining its structural strength. “Because all components we create are unique and need to function for many years without any maintenance or cleaning, development cycles take longer than in terrestrial designs,” says Blecha. “Although the shape of the baffle for the BepiColombo orbiter was given, it took us four years to arrive at the final hardware.” Almatech spent a similar period developing the slit-changing mechanism for the Solar Orbiter, although they were contracted to provide the entire development from first idea to final hardware.

The main cause for these extended development cycles is the enormous number of tests performed to deliver proof that all requirements will be met in all fathomable situations over the entire lifecycle of the components. Within a development cycle, several physical prototypes are built and tested as well, but Almatech performs the vast majority of these tests in the virtual world using a digital twin of the component under scrutiny. For this purpose, the space-grade equipment designers use Femap™ software from Siemens Digital Industries Software in conjunction with the Nastran® solver to simulate performance, starting at very early phases of product development. “The various model analyses provide proof to clients and authorities that the complex devices will perform as required under the anticipated conditions,” says Blecha. “They are also instrumental in our efforts to reduce mass without compromising stability.”

Product: Femap, Simcenter
Industry: Aerospace and Defense

Simcenter Femap helps optimize component and parts for Curiosity’s mission to Mars, the most challenging and demanding ever.

Sending a package to Mars is a complex undertaking

Delivering a roving science laboratory from Earth to the planet Mars requires meticulous planning and precision performance. You only have one chance to get it right: there’s no margin for error. Engineers and scientists at NASA’s Jet Propulsion Laboratory (JPL) at the California Institute of Technology had to make crucial decisions thousands of times over a multi-year product development schedule to successfully land the Mars Rover “Curiosity” on the floor of Gale Crater on August 6, 2012.   They’ve been doing rocket science at JPL since the 1930s. In 1958, JPL scientists launched Explorer, the first US satellite to orbit the Earth, followed by many successful missions not only near Earth, but also to other planets and the stars.

JPL engineers use a toolkit of engineering software applications from Siemens Digital Industries Software to help them make highly informed decisions. A key component in this toolkit is Simcenter™ Femap™ software, an advanced engineering simulation software program that helps create finite element analysis (FEA) models of complex engineering products and systems and displays solution results. Using Simcenter Femap, JPL engineers virtually modeled Curiosity’s components, assemblies and systems, and simulated their performance under a variety of conditions.

From 13,000 to 0 mph in seven minutes Also known as the Mars Science Laboratory (MSL), this rover is massive compared to earlier vehicles NASA has landed on the “Red Planet.” In the deployed configuration with the arm extended, the rover is 2.5 meters wide, 4.5 meters long and 2.1 meters high. Weighing nearly a ton, the Curiosity rover is five times the mass and twice the length of its predecessors, which meant that an entirely new and much softer landing procedure had to be engineered. NASA needed to slow the rover spacecraft from a speed of 13,000 miles per hour (mph) to a virtual standstill to softly land the rover during what NASA calls “Seven Minutes of Terror.” After completing a series of “S” maneuvers, deploying a huge parachute, and then with the unprecedented use of a specially designed “sky crane,” the MSL was gently set down so as not to damage the labs’ functional and scientific components.

Those components include a 2.1 m long robotic arm, which is used to collect powdered samples from rocks, scoop soil, brush surfaces and deliver samples for analytical instruments. The science instruments on the arm’s turret include the Mars Hand Lens Imager (MAHLI) and the Alpha Particle X-ray Spectrometer (APXS). Other tools on the turret are components of the rover’s Sample Acquisition, Processing and Handling (SA/SPaH) subsystem: The Powder Acquisition Drill System (PADS), the Dust Removal Tool (DRT), and the Collection and Handling for Interior Martian Rock Analysis (CHIMRA) device.

Curiosity also inherited many design elements from the previous Mars rovers “Spirit” and “Opportunity,” which reached Mars in 2004. Those features include six-wheel drive, a rocker-bogie suspension system and cameras mounted on a mast to help the mission’s team on Earth select exploration targets and driving routes on Mars.

Virtually all of the spacecraft itself and its payload were subjected to simulation analysis using Simcenter Femap for pre- and post-processing. Simulations performed before part and system production included linear static, normal loads, buckling, nonlinear, random vibration and transient analyses. Thousands of design decisions were made using information from Simcenter Femap simulations.

In addition to the complex nature of the mission itself, engineers developing Curiosity from initial design to final delivery of components to Cape Canaveral were working against the clock. The ideal time window to send a package from Earth to Mars is a 2- to 3-week period that happens roughly every 26 months. Missing that window would have set the mission back by more than two years, so JPL engineers needed to analyze parts and components quickly and efficiently so that they could be fabricated.

The role of Simcenter Femap

Simcenter Femap is JPL’s primary pre- and postprocessor for FEA. For MSL, engineers started using Simcenter Femap early in the design stage when they were performing trade studies on various configurations or different ways to approach the mission. As the configuration matured, they used Simcenter Femap to help create the master finite element model that was used to run the various load cases.

Most of the structural analysts at JPL use Simcenter Femap either for creating or viewing the results of a FEA run. The software was used for both high level-linear analysis and very detailed nonlinear analysis. These are two very different types of analysis both using the same piece of software.

Certain jobs were simply too large for one person, and in some instances engineers had to build on the work of other people who had previously used Simcenter Femap to build FEA models. Simcenter Femap was designed as a very easy-to-use package, created for analysts by analysts who are acutely aware of what engineers need and how they work. They can pick it up after six months of non-use and be back to peak proficiency in a very short time.

Simcenter Femap was critical in performing all types of FEA on all aspects of the vehicle. Each component of the vehicle had a higher-level, loads-type model built, and these models were joined to create the full spacecraft model. JPL engineers worked through various “what if” scenarios, including as many as 37 different load cases for how the parachute would deploy during the landing process.

The Curiosity mission is not JPL’s only current project. Other missions include satellites monitoring conditions on Earth, telescopes, experiments and other spacecraft.

Planned missions include the InSight mission that will place a lander on Mars in 2016 to drill beneath the surface and investigate the planet’s deep interior to better understand Mars’ evolution. There are even plans for a proposed Mars Sample Return mission, which would collect samples from the surface of Mars and return them to Earth.

JPL engineers are currently using and will likely continue to use Simcenter Femap to help accomplish these and other missions of engineering, discovery and science.