[Luis Gonzalez]

"I just don't understand the mentality of not going into orbit with a full tank of gas."

Weight.

[Rebelbase]

"Weight"

I understand fuel is weight and that the trade off was a massive science lab. But by comparison, If you are going walk across the desert, you don't carry a boombox in place of water.

Even if think you can make it across, its stretching your confidence thin to think that the unexpected would not happen.