You need propellants to accelerate toward Mars, then to decelerate at Mars, again to re-accelerate from Mars to Earth, and finally to decelerate back at Earth. Accordingly, the mass of these required propellants, in short, drives our need for innovative launch vehicles.

When we can demonstrate that we can take off horizontally and put something into orbit, then we can begin to talk about increasing the amount of payload. But to say, ‘I’m going to do that and put people into orbit’ is a real leap.

What’s aero braking? That’s a way to use the gravity and upper atmosphere of Earth to sling shot a ship out either deeper into space, or slow it down to be ‘captured’ by Earth’s gravity.

Us reaching the moon convinced Gorbachev and other leaders that the Soviet Union couldn’t compete with the U.S., so they revised their agenda. But people have short memories.

Trips to Mars, the Moon, even orbit, will require that we provide astrotourists with as many comforts from home as possible, including paying each other.