"Over the weekend, due to rough sea conditions, SpaceX's recovery team was unable to secure the center core booster for its return trip to Port Canaveral," SpaceX representatives said in an emailed statement. "As conditions worsened with 8- to 10-foot swells, the booster began to shift and ultimately was unable to remain upright. While we had hoped to bring the booster back intact, the safety of our team always takes precedence. We do not expect future missions to be impacted."This is the time of year when it's very common for the area around the Cape to get strong winds off the ocean and those winds bring rough seas. While it's a shame to see them lose the booster, reality is the system has to be designed for these seas. Balanced all the while against the cost of a ship that much bigger and more stable than the ones they're using.
It's widely reported that the ships are autonomous, and the crews are relocated onto another ship that stands back well away from the drone ship while the landing attempt is made. The first step is for a crew to return to the ship and secure the booster to the deck by welding hold down brackets to the landing feet on the Falcon 9, according to the Wikipedia entry. The statement from SpaceX makes it sound as if they viewed it too dangerous to deploy the welders onto the drone - or to leave them there if they were already aboard.
When you look at the feet of the booster, remember these things are a lot bigger than you might think.
The same view with some workers near the legs adds perspective. Those hold downs aren't standard U-bolts you're going to find at Ace Hardware.
And the Atlantic off the Florida east coast gains another stretch of artificial reef a bit over 225 feet long and 12 feet across.
8 to 10 foot swells offshore are not a big deal. (Depending on the frequency... how close the waves are together.)
ReplyDeleteI think we may have an instance of a design that didn't consider environmental factors.
When you consider that the ship is about as long as a football field - over 330', and has a very wide beam, it's a bit more puzzling. Add in that the booster is probably pretty bottom heavy, since there's no fuel in it and the engines add a lot of mass at the bottom. It doesn't seem to make sense.
DeleteOr maybe they need to design their recover vehicle more like an offshore oil rig, where the center of mass is way below the surface, and less impacted by waves. (Goes up and down, doesn't list back and forth.)
ReplyDeleteStill lots of leverage up high, with a tripod base, and waves in open water are not as rhythmic as you might assume, peaks and valleys are rarely uniform, distance or height. Still, "welders"; this is a 1950's solution to a 21st century scenario.
ReplyDeleteSome sort of reverse elevation gantry system, to grab and lower the booster, would be good. Of course, as our noble host pointed out, a larger ship would be better. Increase the length vs width for a more stable platform.
ReplyDeleteThe landing ships may have some of the same issues that big catamarans have over same sized single hulled ships. The wide hulls give great overall stability, but the frequency of the waves, and the way they are hitting, affects the hull a lot. Cat hulls are great on mid-choppy, but single hulls ride better, in my opinion, in rough seas.
I figure they will conquer this problem. The article at Space.com stated that an automated(?) hold down system could not be used because of the attach points for the side boosters but would be remedied soon.
ReplyDeleteI figured that they knew what it takes to fix it and it cost too much.
DeleteAt some point they have to balance the cost of the fix versus the chances of losing the booster like this, costs due to weather delays, and so on. At what cost/benefit ratio they decide to fix the problem is anyone's guess.
I suggest everyone who believes in reusable boosters watch Antonio Elias talk "Space Transportation: Past, Present and ...?" https://www.youtube.com/watch?v=oY3GclS5VUQ
ReplyDeleteDan Kurt
The most important thing in that video (IMO, of course) is that there's a herd of companies starting up that think there's going to be a big market for small satellite launchers. If his numbers are good, and I'm sure he was right five years ago for that video, we're looking at a major shakeout of providers in the next couple of years. There's just not as many pending microsat launches as these companies are envisioning.
DeleteAs the video went by, I became convinced I watched that back closer to when it was released.
I thought it was interesting that the developer of the Pegasus would say there's no future for reusable boosters when the B-52 they use is nothing but a reusable booster. I understand his distinction based on the shear thermal energy released being lower in the case of the aircraft while the booster releases more in a shorter period.
They should at least make it so when they have a failure, it will be at (recreational) diving depths!
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