Real men dock using solid fuel boosters: Dock two space craft using solid fuel only

[Aphobius]

You must define better what "stage" means, because people can put everything in one stage and just use actions groups or right click things and activate them manually.

It's pretty obvious separating a part of the rocket would constitute a "stage". But what about using action groups to activate something later?

For example if you have a SSTO aircraft and you use the jets first and you activate the rocket later using action groups or even stages .... it's still a Single Stage to Orbit aircraft.

You can have 10 groups of sepatrons and use action groups to activate them one by one, without ever separating any of them, each activation would constitute a stage?

You have to clarify this. Not allowing action groups or activating things later by right clicking them (so people don't do that sepatron thing I've mentioned above) would make this challenge much more challenging. But you have to state it exactly in the rules.

I don't want to waste time with this just to have some unskilled, "inventive" person come and abuse the rules.