SpaceX will conduct a second attempt at landing a Falcon 9 v1.1 core stage on to its Autonomous Spaceport Drone Ship (ASDS) next month, during its primary mission of lofting the DSCOVR spacecraft to orbit. With stunning footage of the first attempt – during the CRS-5 mission – showing how close the core stage came to nailing the landing, the next propulsive return will aim to go one stage further.
Returning A Core To A Barge:
Propulsive returns of the core stage has been undergoing testing since SpaceX upgraded its Falcon 9 to the more capable v1.1 variant.
With her nine Merlin 1D engines arranged on an octoweb structure, the taller core has been enjoying a life after staging.
After the second stage has taken over the mission, tasked with pushing the passenger spacecraft en route to the required orbital destination, the core stage has successfully proved its ability to rotate, point the aft into the direction of travel and execute a boost back/reentry burn using three of the nine engines.
This supersonic retro propulsion burn has been successfully conducted on numerous occasions, allowing for the stage to make a controlled return back to Earth.
Refinements have been made to the core, based on experience gained from the returning stages, such as improved nitrogen thrusters used to overcome the aerodynamic torque to null the roll rate, through to the recent addition of grid fins, allowing for increased stability to allow for pinpoint soft landings.
To realize that goal, the center engine is ignited to stabilize the stage and reduce the vehicle’s velocity prior to touchdown on four landing legs that are deployed around 10 seconds into the burn.
All previous attempts have resulted in the stage touching down on the ocean surface – with varying levels of success.
However, the CRS-5 rocket involved the first attempt to land on a specially modified “barge”, known as the Autonomous Spaceport Drone Ship (ASDS).
Outfitted with thrusters, repurposed from deep sea oil rigs, the platform is able to hold position to within three meters, even in a storm.
This debut attempt to land on the ASDS was always going “sporty”, with SpaceX supremo Elon Musk classing the odds of successfully landing at 50 percent or less.
“Close, but no cigar. This time,” noted Mr. Musk in reviewing the video footage of the core’s debut try, as the stage, with the center engine burning and landing legs deployed, made a valiant attempt to land on the ASDS.
As noted shortly after the event, the stage returned with too much velocity and lost some of its required stability due to the grid fins running out of hydraulic fluid right before landing – although they worked “extremely well from hypersonic velocity to subsonic”.
The spectacular video – tweeted Mr. Musk on Friday – shows the stage coming in hard, hitting the deck at an angle, before cleverly – albeit not on purpose – aborting most of its tankage over the side of the ASDS into the ocean.
The next core – set to be involved with the launch of the DSCOVR spacecraft – will learn from the CRS-5 rocket, with Mr. Musk noting “Upcoming flight already has 50 percent more hydraulic fluid, so should have plenty of margin for landing attempt.”
The Deep Space Climate Observatory (DSCOVR) mission is was scheduled to launch on January 31, at around 6:30pm local time, from Cape Canaveral’s SLC-40. However, this has since slipped to February 8.
The date has moved a few days from its previous slot, with the Static Fire – shown to be scheduled for January 24 – along with the passing of the Launch Readiness Review (LRR) required before the launch date is finally set in stone. The Static Fire is likely to slip to later in the month, or into February, based on the latest launch date target.
DSCOVR is a partnership between NOAA, NASA and the US Air Force, with the mission providing real-time solar wind monitoring capabilities for the NOAA’s space weather alerts and forecasts.
Formerly known as Triana, the spacecraft was originally conceived in the late 1990s as a NASA Earth science mission. However, Triana was cancelled and the satellite went into storage in 2001, before the NOAA funded NASA to remove DSCOVR from storage at NASA’s Goddard Space Flight Center in 2008.
NASA inspected the instruments, tested the mechanisms, provided new electrical components and conducted environmental tests of the observatory.
The spacecraft’s ultimate destination will be the first sun-Earth Lagrange point (L1), located 1.5 million kilometers (930,000 miles) sunward from Earth, a neutral gravity point between Earth and the sun.
The spacecraft will be orbiting this point in a six-month orbit with a spacecraft-Earth-sun angle varying between 4 and 15 degrees.
DSCOVR’s primary instrumentation includes NASA’s Earth Polychromatic Imaging Camera (EPIC) instrument, which will provide spectral images of the entire sunlit face of Earth.
The National Institute of Standards and Technology Advanced Radiometer (NISTAR) is the other DSCOVR NASA instrument, a cavity radiometer designed to measure the reflected and emitted energy (in the 0.2 to 100 micron range) from the entire sunlit face of Earth.
The launch will be SpaceX’s debut in the Orbital/Suborbital Program-3 (OSP-3) class of mission, following the awarding of the contract – that includes another mission known as STP-2 (Space Test Program 2), to fly on a Falcon Heavy – in December, 2012.
Although the successful launch of the spacecraft is the over-riding priority for SpaceX, progression with its propulsive landing ambitions is a key aim for the company.
While SpaceX will likely provide similar odds for the successful landing and recovery of the Falcon 9 core from the DSCOVR flight, the hope will be for the ASDS to sail back to the coast with the core secured on its deck.
Recent information notes that the rocket will be “tied down” via chains that extend from the engine section to the deck.
Once SpaceX has achieved this major milestone – be it on the DSCOVR or a future mission – the advancements won’t stop there.
Mr. Musk has already noted that he wishes to refly a returned stage in the not too distant future, while use of the ASDS could involve refueling the core on the ship, before it then hops off and flies back to land on its own.
As previously reported, such a technique could also address unconfirmed information 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.
Utilizing 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.
Falcon 9 v1.1 – and Falcon Heavy boosters – are set to eventually return directly to land, once the technology has matured.
The East Coast site for returning stages is understood to be SLC-13 at Cape Canaveral.
(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 and NASA)
(Click here: http://www.nasaspaceflight.com/l2/ – to view how you can support NSF’s running costs and access the best space flight content on the entire internet)