Dense atmospheres also make it much easier to enter, descend, and land (EDL), since they can be used for drag parachutes and atmospheric braking.
The atmosphere on Mars by comparison is awful for landing spacecraft. It has just enough density to jumble the craft's trajectory, so vacuum-based EDL techniques similar to the moon landing are impossible, but it's too thin for atmospheric EDL systems similar to those used on Earth.
I wonder if it would also make it easier to exit--having dense atmosphere and low gravity. It might be possible to easily fly a rocket on the underbelly of a low-powered aircraft and launch it from the upper atmosphere.
Leaving the gravity well of a planet depends on delta-v needed to leave that gravity well, not just on getting high enough in the atmosphere. We can easily send balloons to 'space' on earth, but they don't have the speed to achieve escape velocity. Delta-v for Titan is around 2.6km/s (compared to 11.2 on Earth, and 5.0 on Mars).
Atmosphere (especially a dense one that causes drag and heating) makes achieving escape velocity harder, as you need to actually do it 'high up' where the atmosphere is not as dense, say from something similar to Low-Earth Orbit.
>Leaving the gravity well of a planet depends on delta-v needed to leave that gravity well, not just on getting high enough in the atmosphere.
I'm well aware of that, I think you didn't see what I was trying to say.
> as you need to actually do it 'high up' where the atmosphere is not as dense, say from something similar to Low-Earth Orbit.
That was actually the thought process behind it, not the problem with it. I will rephrase it:
On earth piggy-backing or ballooning a rocket to the upper atmosphere is not usually practical due to the ability to produce lift in the atmosphere relative to the size and weight of the rocket.
However, on Titan with a thick atmosphere, imagine flying one to the upper atmosphere which would take relatively little energy in a thick atmosphere with low gravity, thereby escaping much of the problem of atmospheric drag and using it to your benefit instead.
That's just the thought process, of course I don't of anyone that has done the math on the most efficient way to launch from Titan, yet.
That's an interesting thought, but I doubt it works. Density should go roughly like
exp(-gravity * height)
Lesser gravity implies slower decrease of density with height. "Titan's lower gravity means that its atmosphere is far more extended than Earth's; even at a distance of 975 km, the Cassini spacecraft had to make adjustments to maintain a stable orbit against atmospheric drag." https://en.wikipedia.org/wiki/Atmosphere_of_Titan
The atmosphere on Mars by comparison is awful for landing spacecraft. It has just enough density to jumble the craft's trajectory, so vacuum-based EDL techniques similar to the moon landing are impossible, but it's too thin for atmospheric EDL systems similar to those used on Earth.