SpaceX returns to flight with OG2, nails historic core return
SpaceX’s Falcon 9 rocket returned to flight Monday, on a mission for communications firm Orbcomm which also resulted in the first return of the vehicle’s first stage to the launch site. Flying in a new “Full Thrust” configuration, the rocket depart Cape Canaveral at 20:29 Eastern time (01:29 UTC on Tuesday) with the first stage touching down 10 minutes later.
Falcon 9 RTF:
The Orbcomm launch, which follows a similar mission last July, saw the Falcon 9 fly for the first time since June’s failure which claimed the CRS-7 Dragon spacecraft that had been bound for the International Space Station.
The launch also marked the first flight of the Falcon 9 Full Thrust, internally known only as the “Upgraded Falcon 9” – which introduces upgrades that will increase the vehicle’s capacity and increase the number of missions on which first stage recovery attempts will be possible.
SpaceX hoped that the launch would provide their first opportunity to attempt the return of the Falcon 9’s first stage to Cape Canaveral, utilising a newly-completed landing facility designated Landing Zone 1 (LZ-1).
In an unexpected move on Sunday, Elon Musk noted – with just over four hours to launch – that SpaceX was moving the launch to Monday to aid what is technically a secondary goal of the mission.
“Just reviewed mission parameters with SpaceX team. Monte Carlo runs show tomorrow (Monday) night has a 10 percent higher chance of a good landing. Punting 24 hours,” noted Mr. Musk – although the customer, ORBCOMM, claimed the delay was related to more analysis being required on super cooling the LOX, following the Static Fire.
It is possible to reconcile both statements, per Falcon 9’s upgraded use of super-chilled LOX and outside impacts on performance.
During Monday’s launch, the first stage made its historic return to LZ-1 and successfully landed in a milestone event for SpaceX.
The success backed up earlier statements from Mr. Musk over the weekend, citing the attempt to conduct a land recovery was the only focus of the core’s role post-ascent ambition, meaning the recent movements of SpaceX’s Autonomous Spaceport Drone Ship (ASDS) landing barge, named “Of Course I Still Love You”, were not related to this launch.
Two previous landing attempts, both using an earlier ASDS named “Just Read the Instructions”, were attempted following the CRS-5 and CRS-6 Dragon missions earlier in the year.
In both cases, the first stage performed a controlled descent to the barge but were unable to make successful landings.
During January’s CRS-5 mission the first stage ran out of hydraulic fluid shortly before touchdown, coming in hard and at an angle and exploding on impact with the landing platform. April’s CRS-6 saw the first stage topple over as it touched down, again exploding on the platform.
Had it not disintegrated during ascent, June’s CRS-7 mission would have also attempted a barge landing, using Of Course I Still Love You.
The payload for this RTF mission consisted of eleven Orbcomm Generation 2 (OG2) satellites, completing a contract for SpaceX to deploy eighteen such spacecraft which was signed in 2009.
At the time, the satellites were expected to launch atop the smaller Falcon 1e rocket – an improved version of SpaceX’s original Falcon 1 rocket. Development of the Falcon 1e was cancelled after SpaceX opted to focus on the larger Falcon 9 and carry smaller satellites as secondary payloads.
The multiple Falcon 1e launches became three Falcon 9 missions; the first carrying a single satellite as a secondary payload before two dedicated launches with six and eleven spacecraft respectively.
The first OG2 spacecraft to fly was Orbcomm FM101, which was carried aboard a Falcon 9 along with the CRS-1 Dragon mission in October 2012. The rocket suffered an engine failure during first stage flight but was able to continue towards orbit.
Despite deploying the Dragon spacecraft into its planned orbit, the rocket did not have sufficient fuel remaining to deliver the Orbcomm spacecraft to its intended destination and instead the satellite was left stranded in a rapidly decaying orbit where it could not complete its mission. The satellite reentered the atmosphere two days after launch.
The six-satellite launch took place in July 2014, using a Falcon 9 v1.1 rocket, and was completed successfully.
For that flight the rocket was equipped with two stacked EELV Secondary Payload Adaptors (ESPAs), each able to accommodate four spacecraft, with two empty slots on the lower ESPA being filled by mass simulators.
This latest launch used three stacked ESPAs, presumably with a further mass simulator to make the number of attachments up to twelve.
Orbcomm’s OG2 spacecraft were manufactured by Sierra Nevada Corporation and MicroSat Systems, around the SN-100A satellite bus. Argon ST, which is owned by Boeing, produced the satellites’ communication payloads. Each spacecraft has a mass of 172 kilograms (379 lb) and is designed to provide at least five years’ service.
Of the OG2 spacecraft already launched, FM101 was lost in a launch failure and FM111 malfunctioned after eleven months in orbit. The remaining spacecraft are currently believed to be healthy.
The launch marked the debut of the “Full Thrust” version of the Falcon 9, retaining the v1.1 configuration but with the Merlin-1D engines uprated and recertified to increase the thrust available at launch, increasing the performance of the rocket and allowing first stage recovery attempts to be made on a greater number of missions, including launches to geosynchronous transfer orbit where it has not until now been possible.
Named after the Millennium Falcon spaceship in the Star Wars films, the Falcon 9 was introduced by SpaceX in June 2010.
SpaceX had previously launched five smaller Falcon 1 vehicles from Omelek Island in the Marshall Islands; the last two of these successfully reaching orbit; however, the Falcon 1 was abandoned as the company focussed on their larger rocket and the Dragon spacecraft.
When launching from the East Coast of the United States, the Falcon 9 makes use of Space Launch Complex 40 at the Cape Canaveral Air Force Station.
This former Titan launch pad was constructed in the 1960s for the Titan IIIC rocket, and subsequently served the Titan III(34)D and Titan IV vehicles up to the Titan IV’s retirement in 2005.
The complex was later turned over to SpaceX, who rebuilt it to support the Falcon. West Coast launches use a similar pad built on the site of Vandenberg’s former Titan IV launch pad, Space Launch Complex 4E.
The Orbcomm mission was the first Falcon launch since June’s failure to deliver the CRS-7 Dragon spacecraft on its mission to resupply the International Space Station.
On that flight the second stage appeared to suffer a structural failure around the time that engine chilldown was expected to begin, leading to the loss of the vehicle late in first stage flight.
It was the first outright failure for the Falcon 9, which had previously suffered a partial failure during the CRS-1 launch that claimed an earlier Orbcomm satellite, and the first outright failure for SpaceX since the third Falcon 1 launch in August 2008.
The cause of the failure appears to have been an overpressurisation of the second stage oxidiser tank after a helium vessel contained within the tank broke loose of its supports. The Falcon 9 uses RP-1 propellant in both its first and second stages, with liquid oxygen used as an oxidiser.
Following initial activation, checkout and fuelling – the latter now taking place with only 30 minutes to launch – the Falcon 9’s countdown entered its terminal phase ten minutes before launch, with an automated sequence taking control of operations.
Around six minutes before liftoff the rocket was transferred to internal power, and the Strongback structure that is used to transport and erect the vehicle, as well as to provide an attachment point for support umbilicals, was retracted.
The rocket’s flight termination system was powered-on and armed three and a half minutes ahead of liftoff, with the launch director and range control officer giving their final authorisation to proceed before the scheduled launch.
A final startup and pressurisation sequence began in the last minute of the count, with the launch pad water deluge system, or Niagara, also activated around this time.
Ignition of the nine Merlin-1D engines powering the first stage occurred two seconds before the rocket lifted off, allowing time for any problems to become apparent before the vehicle commits to lift off.
During the two seconds between ignition and liftoff, the launch could still be aborted should circumstances dictate this be necessary.
On previous missions the Falcon 9 has taken around a minute to reach the speed of sound, passing through the area of maximum dynamic pressure, or Max-Q, about fifteen seconds afterwards. Some parameters have since changed due to the upgraded nature of the rocket.
The first stage cut off about two minutes, 20 seconds after liftoff.
Following its separation, now four seconds later, the second stage coasted for eleven further seconds before igniting its Merlin Vacuum engine – a derivative of the Merlin-1D optimised for high altitude flight.
Payload fairing separation occurred later in second stage flight at T+12 minutes.
The Falcon made use of a single burn of its second stage prior to spacecraft separation, with this burn lasted about seven and a half minutes.
Around five minutes after the burn ends, the Falcon began to deploy its Orbcomm payload. The target orbit for the launch is expected to be 615 by 750 kilometres (382 by 466 statute miles, 332 by 405 nautical miles), inclined at 52 degrees to the equator.
All eyes were also on the ground, SpaceX returning the first stage for another recovery attempt. Landing of the first stage occurred 10 minutes after launch – a historic first.
Since its first launches with the Falcon 1, SpaceX has been attempting to return the first stages of its rockets to Earth for evaluation and eventually reuse.
To this end, the Falcon 1 was equipped with a parachute but the recovery was never completed successfully. With the larger Falcon 9, SpaceX decided to opt for a powered descent using some of the rocket’s Merlin engines to brake the stage’s descent.
Early tests used water landings to prove that a controlled descent and landing would be possible, and while this was demonstrated the stage could not survive the rigours of landing in the Atlantic Ocean.
SpaceX, therefore, introduced the Autonomous Spaceport Drone Ship (ASDS), a barge equipped as a mobile floating landing platform which the first stage could put down upon.
Although no Falcon has yet landed successfully upon the ASDS, SpaceX felt they were now ready to progress to land landings back at Cape Canaveral.
The Landing Zone 1 site, which SpaceX targeted the first stage towards following the launch, is a former Atlas launch pad which was originally built as Launch Complex 13 (LC-13) in the 1950s for early testing of the first Atlas missiles, along with the adjacent Launch Complexes 11, 12 and 14 which formed the southern half of Cape Canaveral’s “Missile Row”.
As a launch pad, it was first used in August 1958 by Atlas 3B, the second flight of the Atlas-B missile, which was the first of fifty-one rockets to launch from the complex.
Two Atlas-B launches were made from Complex 13; the second being Atlas 6B in September 1958. The pad was next used for a series of thirteen Atlas-D tests between April 1959 and March 1960 followed by fourteen Atlas-E launches between October 1960 and February 1962, with a single Atlas-F using the pad in August 1961.
As Atlas missile tests at Cape Canaveral began to wind down, the service tower at Complex 13 was rebuilt to support payload integration for orbital launches, with the first orbital mission from the pad, using an Atlas-Agena vehicle, lifting off on 17 October 1963 with a pair of Vela satellites designed to detect nuclear explosions from orbit.
This was the first of twenty-one Atlas-Agena launches from the pad; including three pairs of Vela spacecraft, the Mariner 3 probe which was to have flown past Mars, NASA’s five Lunar Orbiter missions to the moon, the fifth Orbiting Geophysical Observatory (OGO-5) magnetospheric research satellite and eleven geosynchronous signals intelligence satellites for the National Reconnaissance Office; seven of the Canyon programme and four of the Aquacade series, also known as Rhyolite.
The final launch from Complex 13 was of an Atlas SLV-3A Agena-D on 7 April 1978. Carrying the fourth and final Aquacade spacecraft, this was the final Atlas-Agena launch from Cape Canaveral, the final launch from any of the original four Atlas pads at the Cape and the final launch of a true Atlas-Agena vehicle; although an Atlas E/F rocket launched the Agena-based Seasat spacecraft from Vandenberg later the same year.
The inactive launch pad was designated a historic landmark in 1984 but fell into disrepair, with the mobile service tower being demolished in 2005 after corrosion left it too unstable to be left standing. The blockhouse has also since been demolished.
SpaceX agreed to lease the facility from the US Air Force earlier this year, with a view to using it as a landing site for the Falcon 9’s first stage.
The company is developing a similar landing facility at Vandenberg, using former Space Launch Complex 4W.
The launch was the twentieth and last of 2015 for the United States, and the last of seven Falcon 9 missions that SpaceX have conducted since the beginning of the year.
A Falcon 9 made the first launch of 2015 worldwide on 10 January, lofting the CRS-5 Dragon mission, following this up with the successful deployment of the Deep Space Climate Observatory (DSCOVR) in February. In early March a Falcon 9 placed a pair of communications satellites; Eutelsat 115 West B and ABS-3A, into geostationary transfer orbit.
Two launches less than a fortnight apart in April saw the CRS-6 mission sent to the International Space Station and another communications spacecraft – and Turkmenistan’s first satellite – TurkmenÄlem 52E placed into orbit.
The next Falcon mission was the ill-fated CRS-7 launch attempt, with this launch marking SpaceX’s return to flight after that failure.
The next Falcon launches are scheduled for mid-January. A flight from Vandenberg to deploy the Jason 3 ocean research satellite is currently slated for 17 January, while the next East Coast mission – to deploy the SES-9 communications satellite – is currently targeting the middle of the month but does not have a confirmed launch date at present.
Following these launches, Dragon is expected to return to flight in February with CRS-8.
The debut of SpaceX’s larger rocket, the Falcon Heavy, is scheduled for the middle to latter part of next year from the Kennedy Space Center.
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