[xixi77]

Thanks for noting Musk's clarification, this did leave me confused for a moment. The difference between what they are trying to do is indeed quite huge.

I feel still a bit unclear on this though: hasn't SpaceX been trying to land just the first stage module (which presumably doesn't try to achieve that Mach 30)? If so, what is the main difference -- just the size of the payload, or is the 1st stage of SpaceX itself already going a lot faster than the BO rocket? (or perhaps both).

[mikeash]

Blue Origin's rocket is returning from a bit above 300,000ft and roughly zero speed. Falcon 9's first stage is returning from a similar altitude but at mach 6.

That adds a lot of difficulty just in terms of getting rid of that speed without destroying your hardware. Plus you need to aim from a lot farther away. The Falcon 9 includes hypersonic grid fins to steer towards the landing site, for example. (Failure of these due to running out of hydraulic fluid is what caused the first landing attempt crash.)

Just getting to that state requires a lot more of the rocket as well. If getting to that altitude is the equivalent of going mach 3, then the Falcon 9 first stage is putting in the equivalent of mach 9, so that's 9x more delta-v, which means the rocket needs to carry vastly more fuel and be vastly lighter.

All in all, the Falcon 9-R is trying to optimize for two things at once, which is always difficult. Landing a rocket vertically is not that difficult. Landing a rocket vertically while having that exact same rocket also be useful as the first stage of an orbital launcher is way harder. It's a bit like building a flying car: there are good cars, and good airplanes, but trying to build a machine that's good at both is far more difficult. Hopefully SpaceX's effort works out better than flying cars have.

[rst]

For one thing, the trajectories are very different -- New Shepard is pretty much up and down, while the SpaceX booster's velocity is mostly horizontal at stage separation; it requires a substantial amount of maneuvering to cancel that out. For another, SpaceX's landing attempts have been on a barge, not flat land, which means that targeting is a much harder problem. (The latter is speculation on my part, but the New Shepard booster went through a lot of gymnastics just before landing; that sort of thing can be a whole lot easier if you just have to wind up level with zero velocity, without having to target a particular spot on the ground as an added constraint.)

EDIT: some observers claim that the New Shepard is hovering. If so, that does two things: first off, it indicates that either the stage is ballasted, or Blue is taking advantage of their engine's very deep throttle range. (SpaceX's first stage can't hover, as even fully throttled-down thrust of one engine exceeds weight of the stage at landing; so long as an engine is firing at all, the stage is accelerating up.) Second, it obviously makes the targeting problem much easier. (Note that the ballast could just be extra fuel; they've clearly got extra to burn in the landing maneuvers...)

[InclinedPlane]

The point is reuse of a core stage of a launch vehicle. Both Blue Origin's vehicle and SpaceX's are launch vehicles, one is sub-orbital the other is orbital. Reusing either makes their respective launches cheaper and easier, but because the launches themselves are vastly different the implications of that reuse are also vastly different.