Quora has a mix of answers from terrible to great.Learning about spaceships and atmospheres has been a funny experience for me. First you think all the wings on spaceships in movies are cool cause sci fi, then you think all the wings are dumb cause physics, but then you think they're cool again cause rocket equation. In a super far future universe where rocket fuel works like car fuel alla epstein drive, dumb blocky spaceships make sense. They also make sense for generation ships or crafts with weak but highly efficient engines. For example a ship like this is freaking awesome.
But what if a space ship didn't have to go through an atmosphere?Spoiler for Hidden:
A high powered laser is shot from Earth to propel the ship for the initial journey, making it circumvent the rocket equation. It would make no sense for it to ever enter an atmosphere.
A smaller ship for just our own solar system however all but needs aerobraking.
This delta v map (not sure if you've played kerbal space program) shows how much change in velocity is needed to move about the Earth, Moon, and mars. Without aerobraking, it'd take 19.5 km/s of delta v while with aerobraking it only takes 13.1 km/s of delta v. Because the fuel needed to accelerate that extra 6.4 km/s has mass, it takes even more fuel just to bring that extra fuel.
Say we have a rocket that weighs 100 tons when empty that has 100 tons of cargo and engines with a 350 ISP (this is kinda similar to SpaceX's Starship). To have 13.1 km/s of delta v, it needs 8,900 tons of fuel. However to have 19.5 km/s of delta v, it needs a whopping 58,500 tons of fuel. It's goes from insane but maybe possible in the future to ludicrous. Aerobraking can save so much fuel that I can't imagine any rocket with strong enough engines would ignore it. NASA's Mars transfer vehicle can't aerobrake for example because it would get stuck in the planet's gravity well.
Spoiler for Hidden:
