Auto Struts are a crucial tool in Kerbal Space Program (KSP) for ensuring the structural integrity of your spacecraft, especially large vessels like space stations and motherships assembled in orbit. They automatically create struts between parts, reinforcing connections and preventing unwanted flexing or wobbling. This guide will delve into the best practices for utilizing auto struts effectively.
Understanding Auto Strut Options in KSP
KSP offers several auto strut modes:
- Grandparent: This mode connects each part to its “grandparent” part, i.e., the part two levels up in the hierarchy. It’s generally the recommended setting for space stations, providing a good balance between stability and performance.
- Heaviest Part: This connects all parts to the heaviest component of the vessel. While effective for rigidity, it can lead to instability if the heaviest part changes, such as when docking a heavier module.
- Root Part: Connects all parts to the designated root part of the vessel. Ideal for rockets, where the root is typically a central fuel tank. Changing the root part in the editor allows for optimizing stability.
Best Practices for Using Auto Struts
Space Station Construction
For space stations, the Grandparent auto strut mode is generally sufficient. Modules in orbit experience minimal stress under microgravity conditions. The primary concern is maintaining rigidity during docking procedures. Grandparent struts adequately handle these forces in most scenarios. However, consider using Heaviest Part for exceptionally large or complex stations, ensuring a central and strong connection point. Plan ahead and choose docking ports capable of handling the stress if you anticipate significant expansion. Using the larger Sr. docking port over the smaller 1.25m port for central connections in large stations can prevent structural weakness.
Rocket Design
Rockets benefit from Root Part auto strutting. Select a central fuel tank as the root part to distribute forces evenly during launch. The rigid connection provided by this mode ensures the rocket maintains structural integrity under intense acceleration and aerodynamic forces. Fairings usually provide sufficient support for payloads during ascent, so additional struts are often unnecessary for the upper stages. However, the lifter stage itself, especially for larger rockets, greatly benefits from root part strutting.
Rigid Attachment for Specialized Cases
While rarely necessary, the Rigid Attachment option creates unbreakable connections between parts. This is useful for specialized craft like heavy construction tugs operating under gravity, preventing flexing that could lead to instability or clipping issues.
Planning for Future Expansion
Always consider future additions when designing your spacecraft. If you plan to dock heavier modules to your space station, avoid relying on Heaviest Part unless the central connecting point remains the heaviest component. Switching to Grandparent or strategically placing struts manually might be necessary to accommodate future growth. Changes in the heaviest part can lead to unexpected physics behavior and potentially catastrophic failures. A Kerbodyne fuel tank can serve as a suitable heavy central point, but ensure no docked modules exceed its mass.
Dealing with Physics Bugs
While auto struts significantly improve stability, physics glitches can still occur, especially with complex or unbalanced designs. These issues often manifest as wobbling, unintended flexing, or even parts breaking apart. If you encounter such problems, re-evaluate your strutting strategy, considering manual strut placement for critical connections. Remember that overly extended structures, whether in height, width, or length, are more prone to instability.
By understanding the different auto strut modes and implementing these best practices, you can ensure your spacecraft remain structurally sound and mission-ready in the challenging environment of KSP.
