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Comment by shirro | Hacker News Reader

They are both great solutions.

Blue Origin could design the most elegant solution to their problem without a lot of compromises.

SpaceX always intended reuse but originally they were going to recover boosters with parachutes. They already had a full flight manifest depending on engines designed for mass production and thrust to weight, not throttle ability. So they had to work with what they had which was a rocket that could not hover. They turned the limitations into a benefit because the hoverslam is more fuel efficient which is far more critical for their service than it would be for Blue Origin.

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>SpaceX always intended reuse but originally they were going to recover boosters with parachutes

I know that engineers have obviously done that math on this, but I still find it incredibly counterintuitive that they are not at least shaving off some velocity with any chutes or other aerodynamic surfaces (except of course there are the grid fins, but afaik those are primarily for steering the ballistic trajectory in the upper atmosphere at hypersonic speeds, and don't significantly alter the terminal velocity relevant to how much fuel you need for a hover burn).

SpaceX totally 'flies' the first stage, but as a cylinder with gridfins it can't shed that much velocity due to aerodynamics.

If you watch the first stage telemetry as it comes back down on the livestream (they don't always show you it, sadly) you can see that actually a huge proportion of the velocity is lost through atmospheric drag. I was shocked the first time I saw it.

Obviously the terminal velocity of the stage is still pretty fast but compared to the speed it starts at it's much smaller.

Yea, atmospheric drag does most of the work to slow the boostet rocket. Which makes it all the more counterintuitive to my brain that the economics and engineering doesn't make sense for deploying some kind of chutes to shave off velocity.

Every kg in fuel you need to burn to land, you need to lift off the pad. From what I found through some Googling, a F9 booster uses a little under 1,000kgs to do the hover burn. I would imagine some lightweight aero surfaces would be more weight-efficient at decelerating the rocket than the 999th, 997th, 996th, (nth) kg of fuel.

Parachutes hinder re-usability. You can't deploy a chute, land, then expect to take off again quickly without manual refurbishment. SpaceX's ultimate goal is zero refurb re-usability.

A parachute would also be next to worthless for landing a fully-loaded BFR on Mars.

SpaceX takes the iterative approach and is designing their vehicle for Mars landings now to get practice, at the expense of being able to carry a bit less to high-energy orbits (which they've largely negated with Falcon Heavy and Falcon 9 upgrades) here on Earth.

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