I think the way this piece is structured really speaks to the journey you mention in your description. I like the idea of having an emotional beginning and ending, and having this idea tie in with the strings that convey the rocket taking off. It was all set up in a way that I could hear what you were going for in the way you connected your ideas to the artwork.
The biggest issue I have with the piece is that while I feel like the structure is very good, I'm not really sold on the composition itself evoking that sense of longing, journeys and wondrous discovery. To me, I felt like I wasn't quite getting the full emotional appeal from the main musical idea that is repeated throughout. And that's not to say that you can't have a repeating idea for the entire three minutes - I just think that when doing that, the emphasis on the journey should be conveyed through the layers in the texture. I can hear you adding some layers, especially to the part with the strings towards the end, but it seems like there isn't enough momentum and "excitement" leading up to the final section.
I really wish the fast moving strings were more present at 2:24 - it might be the balancing, but at 2:36, they sound like off-beat eighth notes and it feels as though the piece is fizzling out before it actually ends. Because you have the more slow, quiet section at the end, I think keeping those fast moving strings constant up until the bells kick in would have built up more contrast between these two sections and made the final section, with the same ideas, have a bigger impact.
Another thing I wanted to mention is that I feel like the reverse cymbal was not necessary for the transitions in this piece. It's a great way to transition between sections and build up a piece, but it's also such a significant and distinct way of transitioning that when used multiple times, it starts to lose its meaning. There's many ways of moving through sections besides just the reverse cymbal, such as swelling a rolled snare or bringing out that leading tone more. Maybe even slowly bringing in a new layer like those fast moving strings a bar before, starting very soft and building to the normal dynamic you use for the main part of its phrase. Keeping the reverse cymbal as a transition idea rather than THE transition idea will make it feel a lot less like it's just there just because.
I have to say, I truly appreciate the playing around with tempo and thought it was really cool when the part with the bells sped up at the beginning and slowed down. And the part at 1:02 with the oboe? That was a fantastic choice for adding emotional richness to the soundscape overall.
If the composition were as strong as the setup, this piece would feel like it had so much more to say about the scene and a more clear interpretation of it, musically. Towards the end, I could hear a chord change at 3:08 that I wish was brought out more and was utilized a bit more throughout the piece itself. Maybe even different chords accompanying the repeating melody could have been interesting, too. But you definitely have it in you to do it. :P Overall, good job!