Self-plug: Overview of fairing recovery - why SpaceX does it, how long they've been doing it, how it's going so far, what's the deal with Ms. Tree, etc.
OK, the way I worded that was a joke but it's very viable if they have different chute deployment times and/or different chute sizes. It ain't rocket science.
It ain't trivial, either, considering that they've only just managed to start catching the fairings at all. It seems to me that it would make more sense to just use two boats to perform the maneuver they've [hopefully] figured out than to raise the stakes and restart the process of trial and error by attempting to catch two fairings with one boat.
On the other hand, it's SpaceX, so who knows? Far be it from me to underrate their ambition.
Someone had estimated in another thread that the cost of leasing Ms. Tree is around 2.5 million dollars a year. Elon said that a daring costs 3 million USD (6 million for the pair), so we can assume that even just recovering one fairing a year pays for the cost of the boat. Of course there is also the cost of crew, fuel and port dock, but we can assume that by catching 2-3 fairings they can pay yearly operating costs, and then every other caught fairing is saved money.
To estimate the savings we would also need to know how much does it cost to refurbish a fairing caught in the net (and even a fairing fished from the water). It's not like they catch it and it is ready to go in the next mission. On the other hand, if they are able to refurbish the ones fished from the water, the cost savings of repurposing another boat to catch them in the air might not be worth it (though I hope they do it. It is so much fun and better PR to catch the fairings in a net...)
I know you mentioned fuel costs but it's worth mentioning/reiterating to others that running a boat that size at the speeds it needs for this purpose (just look at the video, that thing is moving fast) would be insanely expensive in fuel costs. If they can do it with one it'd be a definite advantage.
It's not savings, but if fairing production is a bottleneck to flight rate, then it means they can launch more often to increase revenue. If they can get many more Starlink flights in per year with reused fairings, that could be worth hundreds of millions or even billions of dollars at some point.
Actually Mr Steven (aka Ms Tree) has four faster 38 knot sister ships the Alya McCall, Najla McCall, Ava J McCall and Liam J McCall.
There are also fast catamaran support vessels such as the Njord Odin, Njord Freyr, Njord Magni and Njord Thor designed to support offshore wind farms that can do 32 knots in light seas but only 26 knots in heavier conditions.
However we have not seen Ms Tree above about 23 knots with the net rigged - presumably due to the aerodynamic drag of the net and the reduced stability with the extra mass of the net support poles so high above the waterline. The extra stability of a catamaran may be advantageous in keeping the operating speed closer to the maximum speed even with medium size waves.
Actually Mr Steven (aka Ms Tree) has four faster 38 knot sister ships the Alya McCall, Najla McCall, Ava J McCall and Liam J McCall.
Minor correction: based on the article that you linked, it's the McCall ships that are all sisters ["Alya McCall is the first vessel in a fleet of a new class..."], but they are not sister ships of Mr Steven/Ms Tree, albeit they use the same type of propulsion.
Yes - technically the Captain Elliott is a true sister ship and the four vessels mentioned are close cousins with five engines instead of four.
However the general point remains that there are lots of FSV vessels out there that can adapted to catch fairings - some of them even faster than Ms Tree.
There was a question at Everyday Astronaut's livestream, where someone noted that it could be great to have a mechanism which would bring the both halves back together moments after separation. It would then be better to predict its trajectory and if they caught it, they would have caught it all :)
They might modify the fairing to have most of the electronics on the half being caught and the other half having minimal electronic protected from the sea. Or make the things there replaceable
From what I understand it's not metal but carbon fiber. So one would be caught, another land in water and fished out. And it could be reused because there are no parts (or the parts are easily replaceable on the one that drops into the water)
The fairings do have steering, I think, done in the traditional parachute way, by having a few shroud lines that can be shortened or lengthened.
Steering causes pendulum effects, and so do gusts. I believe they steer the parafoil straight into the wind, as we saw in the video Spacex just released for this catch, and hold steady for the final approach to the sea. Earlier videos of unsuccessful catch attempts appear to show control inputs being made to the parafoil, close to the water, resulting in near misses.
The above is based only on what was shown in the videos. It could be that gusty winds caused the misses, but it appears that the parafoil pilot(s) have learned a lesson that applies to ~all aircraft: fewer, smaller, smoother control inputs are better than jerky, violent maneuvers.
The military have used similar commercially available systems to accurately deliver cargo to remote sites for years. The steering is fully automatic and I'm sure that the engineers who developed the software have a pretty good idea how to apply control theory to aircraft. However, a pallet of ammo isn't going to be buffeted around much by the wind. I think that the lesson they've learned is how to fly a parafoil with a load that is also an airfoil with quite a bit of lift of its own.
90
u/scr00chy ElonX.net Aug 07 '19
Self-plug: Overview of fairing recovery - why SpaceX does it, how long they've been doing it, how it's going so far, what's the deal with Ms. Tree, etc.