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Comment by jacquesm | Hacker News Reader

Does anybody know why they would re-try the barge thing when they've already got a once-proven way of landing on a pad? What is the benefit of being able to land on a barge? (which to me seems to be a lot harder than landing on land, after all, now you have two craft to coordinate, one of which is only nominally under your control (lat, long, the rest is very much subject to change due to the action of the ocean).

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The benefit of landing on the barge is that the barge can be located way downrange. This means the rocket can fly to it more directly, rather than making a U turn and flying back where it came from. That in turn means the rocket needs less fuel for landing maneuvers and can use more fuel for putting stuff into space. For some missions, the rocket won't have enough fuel to get the payload to orbit and return to the launch site for landing. The barge will allow first stage recovery for these missions.

In this particular case the launch was from Vandenberg in California and they do not yet have permit clearances to land the first stage back on land here. However, as others have said the barge is key for other reasons too.

As far as I understand this, the landing location depends on the launch site and mission profile - i.e. they can't always boost back to the pad with the remaining fuel stage 1 has.

Given that, then even if they'd decide to eventually launch every mission so that first stage can land on the ground, the current situation was that they could either waste the booster or try and land on water. So the question is - why shouldn't they try?

Depending on the target orbit, it is often simply not possible to propel the first stage back to dry land. Today's Vandenberg launch into polar orbit was just that.

They said during prelaunch news conference that for this mission, falcon 9 had plenty of oomph to get the first stage back to the pad (payload mass is low), but couldn't because of environmental assessment not being ready.

https://twitter.com/elonmusk/status/688844190826942465

"Ship landings are not needed for flexibility or to save fuel costs. Just not physically possible to return to launch site" - @elonmusk

One party or another has the wrong information _shrug_.

Elon Musk explained why they need drone ship landings at all, once they have proved they can land on land: because some missions require landing downrange.

I explained that Hans Koenigsmann said 27 minutes 57 seconds into NASA's Jason-3 prelaunch new conference that they have to try to land the Jason-3 booster on drone ship instead of land because they don't have environmental approval at this time for Vandenberg AFB in Califiornia.

https://youtu.be/Set_IES7VZE?t=1672

Fuel.

Edit: to elaborate, you can burn more fuel on the first stage, with all the advantages that implies, if you have a place to land down range as opposed to having to turn around and fly back. Sometimes the way to get that place to land might be to put it there.

You mean so they can reach higher orbits when landing further downrange rather than reverse back to a landing pad?

Exactly. Or fly more cargo.

Or simply lift more stuff with the same amount of fuel.

They need it for falcon heavy central core, and also for certain launches where they don't have enough deltav to return to landing site. Land is preferable of course.

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