Back in August of 2019, Rocket Lab - one of the most successful small satellite launch providers - announced that they intend to recover the booster stage of their Electron booster for reuse. Their intent is to both reduce the costs they charge and increase their launch cadence. At the time, they were saying they needed to quadruple the number of launches they could do per year to meet demand.
Unlike SpaceX's Falcon 9, though, Electron wasn't designed for reuse from the blank sheet of paper (or blank screen) stage. Redesign of the Electron adding the mass of hardware like deployable legs, would undoubtedly lead to either redesign of the rocket or only launching smaller payloads. The Electron's payloads are already fairly small at 220 kg (485 lb.) so there's basically very little margin there.
Given that, they opted for a technology the military has used for decades, recovery by putting a parachute on the booster and snatching the stage out of the air with a helicopter.
As expressed in that August '19 post, they started on a program of capturing data on what the stage went through during descent, and then later recovered some stages that splashed into the Pacific, the first of which was in November of '20, so 15 months after the announcement they were going to start working toward the goal. To the best of my knowledge, none of those were actually reused.
This week's Rocket Report from Ars Technica reports their next mission will be the first attempt to catch a booster.
The company will make this attempt during its next flight, with a launch window that opens on April 19 for the "There and Back Again" mission to deploy 34 small satellites. After the first stage completes its boost phase, at 2 minutes and 30 seconds, it will separate and begin descending at speeds up to 8,300 km per hour.
Falling, spinning, catching? ... Nominally, a drogue parachute should deploy at 13 km altitude, followed by the rocket's main parachute at around 6 km altitude to dramatically slow the stage to 10 meters per second. As the stage enters the capture zone, Rocket Lab’s Sikorsky S-92 helicopter will attempt to rendezvous with the returning stage and capture the parachute line via a hook. If this is successful, Rocket Lab engineers and technicians will conduct a thorough analysis of the stage and assess its suitability for re-flight.
Rocket Lab's website news page has more details.
Back in August of '19, when asked about how many reuses they wanted for each Electron Booster, CEO Peter Beck replied, "If we could reuse it once we've effectively doubled production. Once would be wonderful. Anything more would be really fantastic." As we can see from SpaceX now having reused a booster 12 times, that lifetime might well be beyond two. The disclaimer here is that Falcon 9 was designed for reuse from the get-go while it's an add on feature for Electron. The first thing that comes to mine is that Falcon 9 is a welded metal booster while the Electron is a carbon fiber composite. Design details like that might matter.
The launch time hasn't been announced yet, but I'll be trying to watch it that Tuesday. I can only wish them tons of luck. Happy hunting, Rocket Lab!
Ambitious, and interesting! Best of luck to them!!!
ReplyDeleteWhen Starship and SuperHeavyBooster were first brought to light by Musk and SpaceX, they were going for carbon fiber and composite construction.
ReplyDeleteBut the issue with carbon fiber and composite construction is the stuff works until it doesn't, and it doesn't have the same heat resistance as good old metal.
Which is why Musk surprised everyone when he went with stainless steel.
We'll see what happens with Rocket Lab. Maybe workable for a booster, don't know how the carbon fiber will work out for a returnable upper stage.
Carbon fiber is useful stuff, but to make useful parts it has to be embedded in some matrix. Usually a plastic. Just like fiberglass is more accurately called fiberglass reinforced plastic and is just a woven mat until it's embedded in the plastic, graphite is embedded into the plastic. Yeah, the composite is stronger than the plastic but only when they're bonded to each other perfectly.
ReplyDeleteAs you say, it works until it doesn't and the failure mode is generally a brittle failure of the plastic.
The base of their booster is going to be in the vicinity of a lot of hot fire all the way up. It sounds like they're going to have use a little leftover fuel to help slow the booster, so they'll fly into the hot exhaust. Which would you trust more with flames playing over the surface, metal or plastic? I wouldn't be surprised if they could manage a couple of reuses but not as many as the Falcon 9.
I've been wondering how the composite and liquid O2 get along. Lox can react explosively with organics, even something like leather. My thought was to build/ filament-wind the tank around a thin metal shell, but doing the whole thing out of SS make a lot of sense.
ReplyDeleteI wouldn't be surprised if lox caused both the plastic matrix and the graphite fibers to burn.
DeleteDid some looking, but don't see any data on how rocket lab makes its tanks. I guess it's considered proprietary.