With the go-ahead from NASA for a first mission to the International Space Station (ISS), the engineering team at Sierra Nevada Corp. (SNC) is reviewing flight performance data and refining the Dream Chaser spacecraft, refining the vehicle’s design adaptations to meet mission requirements and changing payloads. The team is using the HyperSizer software from Collier Research Corp.
The HyperSizer software gives the team insights into the strength, weight, and manufacturability of designs for both composite and metal structures. Typically able to reduce the weight of existing designs by 20-40%, the software plays an important role in margin-of-safety certification for aerospace projects and is also valuable for wind, marine and other fields looking for performance with durability.
The current model of the autonomous, reusable Dream Chaser—Commercial Resupply Service 2 (CRS-2)—will transport pressurized and unpressurized cargo to and from the ISS, with a launch window of late 2020. The vehicle also has the potential for satellite servicing, orbital-debris removal and exploration technology testing.
In every case the demands of low-orbit flight, earth reentry, runway landing and vehicle reuse require precision design for reliability, durability and safety. Each type of mission requires additional analysis due to new flight trajectories and corresponding changes to the vehicle loads.
Managing the complexity of ever-evolving designs
The unique challenges faced by the structural engineers at SNC were to design the Dream Chaser to accommodate changing cargo weights and different reentry trajectories, carry pressurized and non-pressurized items, and withstand significant deflection forces.
According to SNC engineers Andy Kim and Eric Schleicher, to meet these challenges HyperSizer was used by the team on nearly all primary composite structures for the launch-approved CRS-2.
“HyperSizer’s suite of industry-standard failure criteria was valuable for our team, enabling us to quickly size the Dream Chaser structure and perform architectural trade studies,” says Andy Kim, Senior Structural Engineer for SNC. “The software’s rapid analysis capability gave us more time to interrogate our results and gain insights into the sensitivity of the structural weight to various design features and stiffener cross sections.”
“HyperSizer helped us improve and automate the design-analysis process for the CRS-2,” says Eric Schleicher, SNC Principal Structural Engineer. “We found some of the most useful aspects of the software to be load processing, sizing, margin reporting and the finite-element model [FEM] update feature.”
“The SNC team did a great job of incorporating HyperSizer into their design and analysis process to the hit weight and schedule targets,” said James Ainsworth, lead stress engineer for Collier Research Corporation. “They took full advantage of the software’s scripting API to customize the workflow and automate data exchange with their suite of CAE software tools. This enabled the team to move rapidly from whole-scale optimization to detailed analysis and stress reporting. It will be exciting to watch the spacecraft meet its next milestones and prepare for powered orbital space flight.”
Collier Research Corp.