Ok... On my second attempt, I almost reached the belt. Nailed on the third. Looked at the code a bit for clues and it's noted:
The matter required is only the one consumed by the thrusters, it doesn't take into account the normal consumption (and remember your drones aren't working during the travel).
Your energy signature will change from the sinusoidal form to peak flat. It also decreases to 25%, which, according to the traveled distance, of 1.2 AU, obeys the inverted square law.
Some suggestions:
A plan flight to the asteroid belt will usually involve an orbit transfer to lunar orbit and then using the gravitational assistance from Earth. This reduces the required costs (and time). Transfer orbit is very cost efficient.
You can then break the travel into 2:
1. Travel to the moon. The drones efficiency will drop (or be disabled). You can counter it with the drones mining the lunar surface or reducing matter launching costs (since Moon's gravity is lesser). Assume a polar orbit, and we'll have sun 100% of the time. It's still possible to save the crew, in case of a mishap.
2. Travel to the asteroid belt. The usual, but the cost is greatly reduced. This allows for a bigger station.
---
I would like a display of the drone matter harvesting and power consumption on the build info. This information IS necessary. Same with the power and matter consumption of the crew, including the credits they generate. Would also love to see the credit generation rate. There is space above the credit display.
---
I don't have a direct account of my matter consumption. Try to mimic the power UI box. Something like first row for production, consumption on the second and the third row for available. This also has the advantage for when implementing a cargo bay in the future (if the game moves into that direction).
If the concern is the screen space, you can try reducing the font on the boxes one or two sizes. This kind of games are played on computers, and assuming a 1024 x 768 monitor display is perfectly acceptable, so you have more space to play with. Since itch.io right side buttons are invasive, we usually play on full screen anyways.
---
What killed my third round was that module building does not take into account the available matter. +93 net positive matter production, still reached bellow zero while constructing a solar panel. Try to implement a fail safe, like pausing construction when matter is extremely low (.1 tons or something), or dynamically adjust the consumption.
So far, that's it.