Let me chime in one last time. This is unfortunately a horrible way of making a two-tonne vehicle airborne, not because it's early tech, but because of physics. Aeroplanes use aerodynamic lift - the Roadster doesn’t. Vertical rocket thrust has been around for decades, but continuously using thrust to hold a two-tonne vehicle against Earth’s gravity is incredibly inefficient. Sure, it can improve, it can get more efficient, lighter tanks, more compressed air (at the cost of more weight), but you can’t engineer away the fundamental problem that a small car has to carry and continuously expend a huge amount of weighty propellant for it to lift for a matter of seconds. If this was on the moon, which has far less gravity, it'd be far more viable, but on Earth, it'll never be more than a gimmick.