SpaceX needs a horizontal launcher?

[Navigaiter]

Watching the Sx superheavy booster take over ten seconds just to rise 500 feet and clear the launch tower, I understand how much of the booster's massive fuel load is wasted on getting its own fuel and itself off the ground!!
It seems more efficient to launch the booster from a supersonic rocket sled. The sled would be an earthbound partial booster with a super quick turnaround.
Acceleration would be quicker when moving across gravity rather than lifting vertically against gravity.
Rocket sled technology is "old hat" and Elon knows how to scale things UP!

Mod Edit - Personal Promotion Removed per forum rules

 

[billslugg]

Horizontal launching from sea level traverses too much of a dense atmosphere.
Cost of horizontal rails would be enormous.
Additional drag due to coming up to speed at a low altitude outweighs the fuel gains of lofting a lighter vehicle.
Straight up gets the rocket to thinner air as quickly as possible.
Ullage problems with horizontal firing.
Rotating the structure in dense air is problematic.

There is no advantage and many disadvantages.