What are the advantages/disadvantages of VTOL and HTOL for a suborbital flight?

[engineer994]

Virgin Galactic and XCOR are designing an HTOL (horizontal takeoff/landing) suborbital vehicle, while Masten and Blue Origin are designing a VTOL (vertical takeoff/landing) suborbital vehicle to shuttle people into space. Are there advantages or disadvantages to VTOL and HTOL? Why would the engineers decide to employ one takeoff/landing strategy over another?

[QuantumG]

Welcome to the forum!

The general reason why you'd choose to go with horizontal landing over vertical landing is that you don't need power (as in, engines) to get out of the sky. The other alternative is a parachute, but landing under a parachute is not a gentle affair and then you have to repack the parachute and there's generally a lot of pain and risk that comes along with that, plus it's only scalable so far. If you choose to go with horizontal landing then horizontal takeoff starts to look a lot nicer that if you were just going to throw wings on a vehicle for takeoff and then get rid of them somehow for landing, but with something like air launch that'd be a reasonable choice too.

On the other hand, making a plane is a lot of hard work that doesn't help you at all at making better rockets. So, if your focus is on making rocket engines that are reusable and well controlled you might choose to dedicate your time to that instead of playing around with wind tunnels and such - that'll lead you to think about ways to land that rely on these engines that you've spent so much time perfecting. i.e., vertical landing.

Then there's the question of orbital aspirations. If your end goal is to build an reusable orbital launch system - as all these companies will tell you they want to do eventually - then you really have to start asking what wings are buying you. The saying goes that wings in space are just dead weight, because there's no air up there.