The mystery behind the “floating platform” – set to welcome home a returning Falcon 9 v1.1 first stage – has been solved via a series of fascinating comments by SpaceX’s Elon Musk. Known as the Autonomous Spaceport Drone Ship, the ocean faring platform will be the new propulsive landing target for a Falcon 9, possibly as soon as the CRS-5/SpX-5 Dragon mission in December.
SpaceX is currently working through an incremental evolution of its reusable rocket aspirations, continuing a path that should eventually result in the first Falcon 9 v1.1 core stage returning to land and being processed for a future launch.
Normally, first stages can only look forward to a one-time push uphill, ahead of the prospect of a watery grave in the ocean downrange of the launch site.
First hinted at in 2009, before expanding on the goals in 2011, Mr. Musk spoke of his ambitions of creating a paradigm shift in the traditional approach for reusing rocket hardware – one of many SpaceX revolutions that has fostered legions of fans for his company.
Incremental steps towards achieving this aim have already been conducted, ranging from computational evaluations into the possibility of returning rocket stages without crippling performance penalties that would be detrimental to customer upmass requirements, through to real life testing during missions.
Visible signs of progress were seen at SpaceX’s test center in Texas, where the Grasshopper test vehicle began to make impressive “hops” to fine-tune controllability and engine performance requirements for smooth and precise landings.
The test program at the McGregor facility was advanced via the use of the F-9R Dev-1 vehicle, the big sister to the Grasshopper and a close match to the real life Falcon 9 v1.1 first stages being employed on actual missions.
SpaceX noted that this test vehicle was always going to push the boundaries in more ways than one, placing emphasis on the rocket science mantra of “this is why we test”.
“So we’re (100 percent) testing on the Grasshopper. But, that means we’re not pushing hard enough. We’ve got to tunnel one of those vehicle into the ground by trying something really hard,” noted SpaceX President Gwynne Shotwell in 2013.
“So now our challenge to our test team is you’ve got to push hard enough that we’re going to see something happen. A spectacular video.”
The vehicle had already enjoyed several hops into the Texas air, providing impressive controllability, while refining the use of fins for stability and the pinpoint soft landing on her four legs.
More testing, via the new F-9R Dev-2 – which underwent validation testing on the tripod stand in September, per L2’s McGregor Update Section – is expected to begin soon, before she moves for higher altitude testing at Spaceport America in New Mexico.
“The current plan is to continue testing in Texas with F-9R Dev-2 and then move to New Mexico when we transition to higher altitude tests,” noted SpaceX Spokesman John Taylor to NASASpaceFlight.com recently.
All of this testing is being conducted in tandem with actual propulsive landings of core stages during actual missions.
Since the move to the upgraded Falcon 9 v1.1, with her more powerful Merlin 1D engines, SpaceX has been working through the objectives to safely return the core stage back to Earth via a propulsive landing on to the ocean surface.
These returns involve numerous milestones, all occurring after the core stage has completed its primary role of lofting the second stage and passenger on their way towards their orbital destination.
The events begin shortly after staging, with the first stage booster rotating 180 degrees via Reaction Control System (RCS) thrusters, prior to the re-ignition of three of the booster’s nine Merlin 1D engines.
“(It involves) a reentry burn and then a landing burn with the Falcon 9 first stage. For the first burn, we relight three engines to do a supersonic retro propulsion burn to slow the vehicle down and help ensure it survives atmospheric reentry,” SpaceX’s Emily Shanklin explained to NASASpaceFlight.com earlier this year.
“Assuming successful reentry, SpaceX relight the center engine to stabilize the stage and reduce the vehicle’s velocity prior to contact with the water. About 10 seconds into the landing burn, SpaceX demonstrates successful deployment of the legs in preparation for future land landings.”
The goal of a propulsive return and soft landing on the ocean surface – since aided with refinements to the control thrusters and the addition of fins for stability – has since been achieved successfully, although a stage has yet to be recovered.
Recovery from the unforgiving Atlantic ocean was always classed as unlikely. However, that may soon change.
SpaceX has been planning to return a core stage to a landing platform, first thought to be a barge of sorts, for some time. It was first mentioned by Ms. Shotwell, before Mr. Musk expanded on what it would look like.
“For the upcoming launch (SpaceX Falcon 9 v1.1 launch with the CRS-5/SpX-5 Dragon to the ISS), I think we’ve got a chance of landing on a floating landing platform,” Elon Musk said at a recent MIT event (video – transcript).
“We actually have a huge platform that’s being constructed at a shipyard in Louisiana right now. Which is – well, it’s huge, huge-ish, it’s about 300 feet long by 170 feet wide.”
Recently, Mr. Musk posted a photo of the platform, naming it the Autonomous Spaceport Drone Ship, complete with its own “X marks the spot” SpaceX logo in the center of the platform.
“That looks very tiny from space, and the leg span of the rocket is 60 feet,” he added at the MIT event, “and this is going to be positioning itself out in the ocean with engines that will try to keep it in a particular position – but it’s tricky, you’ve got to deal with these big rollers and GPS errors.”
Mr. Musk classes the odds of successfully landing on the platform at 50 percent or less for the first attempt.
The ship is more than just a floating platform, with Mr. Musk noting it has been outfitted with thrusters, repurposed from deep sea oil rigs, allowing for the platform to hold position to within three meters, even in a storm.
Landing a core stage on the platform would be a major achievement. However, Mr. Musk appears to have yet more plans for the Autonomous Spaceport Drone Ship.
“Will allow (for) refuel and rocket flyback in future,” he added to the unveiling of the ship.
While that fascinating detail hasn’t yet been expanded on, it suggests a plan – or at least the option – to land stages on the Autonomous Spaceport Drone Ship, refuel and then allow them to make the hop back to land. This would also show the additional value of the continued testing with F-9R Dev-2.
Such a technique could also solve a rumored note surrounding the Falcon Heavy, which suggested SpaceX had been looking at an island downrange of the West Coast launch site for returning the center of the three Falcon Heavy cores, in the event of high payload penalties negating a return to the preferred landing site at SLC-4W.
Returning a stage to an Autonomous Spaceport Drone Ship positioned downrange of Vandenberg, allowing it to refuel and make the “hop” back to the West coast would become a potential solution.
However, this is all for the future. The upcoming effort to land a Falcon 9 v1.1 core stage on the Autonomous Spaceport Drone Ship would be the next step in an exciting future where rockets can extend their lives and ultimately bring down costs.
(Images: via L2’s SpaceX Section, including renderings created by L2 Artist Nathan Koga – Click here for full resolution F9, F9-R, FH and BFR renderings and more – these are not official SpaceX images. Other images from SpaceX, Elon Musk and NSF members Jim Howard and Brick_top.)
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