There are several ways to get involved in space exploration and you don’t necessary need to have the greatest understanding of everything. Focus on one area that you find interesting and excel at that, whether it be command and data processing, thermal, mechanical, systems engineering, etc… it will all aid in the development of a spacecraft. If you want to look at everything (not really specializing) I recommend looking into systems engineering, the best book for this is Space Mission Engineering: The New SMAD (this is literally a bible here at NASA for spacecraft design), which outlies guidelines for developing spacecrafts, analysis, configurations, and much more.
Space Grant Programs – NASA funded organizations that are at most universities across the US and usually work on space related projects from developing CubeSats to creating new instruments or space-rated hardware. Many of these universities would be thrilled to have an additional participate helping develop their systems. A list of US based Space Grant Programs.
CubeSat Workshops – A great way to meet community members involved in developing CubeSats and CubeSat hardware. Workshops would be an excellent place to meet new people and make connections to help develop systems.
Open Source Projects – This is a harder one and have yet many open source space related projects. One open source project I know of is UPSat.
Tools & Resources
I recommend reading about spacecraft systems and their design. Depending on what you actually want to accomplish I recommend starting small (with CubeSats) and actually try to create your own, maybe open source it, but most importantly, it will give you the best experience and something to talk about.
Do not be afraid to email programs or organizations out of the blue and offer them assistance or ask them questions. Most will be thrilled to help and collaborate with you.
- CAD – I’d recommend learning SolidWorks, it’s fairly easy to use and is relatively cheap. However, most CAD programs will be adequate for developing a CubeSat. Depending on complexity of the system and what you wish to accomplish you might want to use a different CAD package.
- Orbital Simulation - AGI STK A great resource for trajectory design, mission planning, and a lot more. It is commonly used throughout the space industry.
- Simulation and Analysis - You can use integrated simulation packages that are in SolidWorks or other CAD programs. However, dedicated simulation packages such as COMSOL Multiphysics or Thermal Desktop are widely used and accepted. Also the Siemens NX simulation package is very good.
- Software for spacecraft development, design, and analysis (look at the updated response from 5/29/2018).