quote:
Wouldn't being able to take off from the Moon be a big time game changer, because there is no atmosphere and thus the amount of energy needed for takeoff would be drastically reduced?

Gravity is vastly more important than atmospheric drag when determining the forces acting upon a rocket. That being said, the moon's gravity is approx 1/6 that of Earth's.

There are 4 basic forces that act upon a rocket during flight; Thrust, Mass, Drag and lift. Given the small nature of the stabilization fins on most rockets, lift is usually negligible, and the effect of drag is much higher (usually from the cross sectional area of the rocket body). Resultantly, most rockets are evaluated not by how much lift they have, but by their thrust to drag ratio. Using vectored thrust nozzles, many modern rockets can eliminate stabilization fins get that number to almost zero. But of all the external forces trying to keep a rocket on the ground, it's gravity by a long shot. It's why the engines are massive and the fins are small. It's also why most rockets preform a "roll program" not long after launch. To change the vector angle and reduce the effect of grvity.

However, that's not the whole story. Like all objects, rockets have a center of mass, and the location of this center of mass effects their stability. In addition to center of mass, rockets also have what is know as a center of pressure. The center of pressure is defined as where the aerodynamic forces in the front of the rocket are equal to those on the back of the rocket. For a rocket to be stable in the atmosphere, the center of pressure must be behind the center of pressure. This has implication when building rockets on the distribution of fuel (often the heaviest part of a rocket) and payload. Obviously in the vacuum of space, the center of pressure is irrelevant. This gives designers much more flexibility in design and how to arrange cargo and fuel on a spacecraft.

This is also why the discovery of frozen water on the moon in the craters near the poles is so important. If it can by hydrolyzed the extracted hydrogen could be used for fuel (and the oxygen for life support). This would make the moon an ideal jumping off point for exploring the far reaches of the solar system and beyond...

This post was edited on 3/15/24 at 7:06 am