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Comment by iaw | Hacker News Reader

I have to hand it to them, they are doing a damn good job on safety.

I wonder how this bodes for the future of hazardous professions like offshore oil-drilling.

They probably won't be landing rockets on oil rigs, so probably not very much related.

If they keep upping their launch cadence, I suspect they'll actually need something similar to an oil rig permanently sited instead of running the ships back and forth all the time.

Are all those landings in the same spot? I was under the impression that the LZ can be all over the place depending on the weight/trajectory of the payload.

Heavy payloads and ones destined for geostationary orbit currently need a drone ship, whereas lighter payloads or ones for low orbit can return to the launch site.

I'm not sure how much the drone ship launches deviate in a north/south or east/west direction for ship landings (couldn't find a map). The boosters have a fairly significant ability to maneuver, and a fixed platform may offer enough benefits to slightly limit payload sizes. Falcon Heavy will also help there.

Eventually, BFR will have enough performance margin to return to the launch site on all missions. I suspect SpaceX wouldn't want to invest in any fixed oceanic infrastructure when their next generation system wouldn't have any use for it.

Their BFR video showed sea platforms near cities being used for launch/landing for Earth-to-Earth transit, though.

I believe that is more because most cities won't want a really loud rocket launching/landing nearby.

BFR will have enough performance margin to RTL for missions with F9 sized payloads. But eventually customers will want heavier payloads, and that will mean no RTL.

There’s no provision for BFR boosters to land anywhere but the launch site. They’re looking at 150 tons to orbit that way. If a customer wants more, they can put it up on two flights.

The drone ship location varies quite a bit, depending on payload, destination orbit, weather, etc.

You'd still need the barge to bring back the booster, plus the tug to pull the barge (and now a crane to transfer the booster from a fixed platform to the barge at sea). Not much benefit to stick a platform in the ocean when the barge serves that purpose sufficiently.

Edit: I'm unsure if you'd want to waste an engine firing on a boostback to the launchpad. Way above my domain knowledge though.

> You'd still need the barge to bring back the booster...

Nah. Automated refueling, then send it back to land via a little suborbital hop.

At least until they start refueling and flying back.

I understood that part of the reason the landing ship can be so small is that the drone ship is actively maneuvering to a spot to catch the booster.

It's announced in the sequence when the drone ship acquires tracking signals from the booster, I'm guessing it's 99% automated other than abort contingencies.

Even if it's only moving 50ft that'd require a radial increase for a fixed landing spot.

But then they also stuck their land-based landings right on the money so it could just be a purely safety related thing.

I don't think the ship maneuvers at all. Both the ship and rocket are pre-programmed with the landing coordinates, and independently arrange to be at the right spot at the right time. The ship has fancy thrusters, but their purpose is to hold it perfectly still even when the water is moving around a lot.

That's my understanding as well. The ship moves really slow by comparison to the rocket, not much useful moving it can do - it just stays in place despite waves and weather.

The ship is also painted with a radar reflective X that the booster is targeting on the way down. The ship just has massive engines for solid station keeping in rough seas. Like you say they don't use those to move to the booster.

I'm fairly sure it's these things: https://www.thrustmaster.net/out-drive-propulsion-unit/

They were posted about when the ships were first made. And I know spacex had gone a size up from the originals.

Totally what that guy on Gold Rush needs to get his barge up the Yukon. ;)

That's just a tracking signal, not guidance. Both the booster and the drone ship navigate to the same GPS coordinates.

They also have a radar on the ASDS that the rocket locks onto to help it navigate in addition to the GPS. This gives it a much more exact set of coordinates to shoot for so to speak. There was extensive discussion regarding this on r/SpaceX after they managed a virtually perfect bullseye landing several landings ago.

The landing ship is the size of a football field, not something I'd call small by any means. The booster that lands on it is approximately 14 stories high (230ft / 70m).

There's an advantage to the ships that a fixed location couldn't provide. With the ship, you can anchor the rocket and pull it into port without having to move the rocket itself after landing. On a fixed platform, you'd have to have infrastructure to relocate the rocket to bring it into port. Unless, of course, you're going to refurbish it and launch from the platform ... Now that would be impressive.

Perhaps they should contact the Zenit people.

At that point they would be better off using full RTLS and landing the rocket on land back near the launchpad as much as possible.

Also based on the BFR / spaceX airways teaser video, they might be planning this sort of offshore refurbishment / no refurbishment needed mode anyway.

> Unless, of course, you're going to refurbish it and launch from the platform

But then you're at the same problem again - if the fuel isn't enough to cancel out the entire downrange, they have to land some place further out again.

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