Sorry... my sad-brain thinking-out-loud...
What KIND of spacecraft???
Unmanned
Optionally-manned
Manned-Crewed
Manned-Colonizing
Special-purpose/one-use
Multi-purpose, reusable, indefinite-life
Micro/Mini [CubeSat]
Communications
Weather/earth-observing
Surveillance/spy
Space Observatories
In-space servicing or boost modules
Lunar-orbiter/Landers
Planet-orbiter/observing
Planet-landing/roving
Solar Orbiting
Deep-Space Fly-By
General configuration/layout [mission specific]
Structures
Basic systems
Insulation and thermal control
Power/thrust generation systems [solar, nuclear, Ion, chemical, gyro, etc]
Sensors and cameras
Life-support [vehicles]
life-support [space/planet-suits]
Antennas/communications
Launch vehicles
Launch-payload fairings/enclosures/boosters
'Origami-folding/unfolding mechanisms/procedures' [for launch-vehicle packaging]
Service/support
Space Environment
Ballistics and orbital mechanics/trajectories
Aerodynamics/dynamics
Re-entry/lander vehicles [heat shields, propulsion, etc]
Wings/stabilizers and/or aero-decelerators [parachutes]
Failure and accident analysis
etc...
NOTE. There are great documents for 'learning about' all of these topics [including some with lessons learned]... and bunches, more.
My brain hurts... it is impossible to know-it-all... but it is possible to know some-things important about every aspect. Get Curious... dive-deep... then choose.
Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]