Falcon 9 flight 20 (also known as Orbcomm OG2 M2) was a Falcon 9 space launch that occurred on 22 December 2015 at 01:29:00 UTC (21 December, 8:29:00 pm local time). It was the first time that the first stage of an orbital rocket made a successful return and vertical landing. The successful landing of the first stage at Landing Zone 1, near the launch site, was the result of a five-year technology development program to develop a reusable launch system and came on a flight test that followed the primary launch mission. Following separation of the second stage, SpaceX conducted the eighth of its controlled booster descent tests of the spent first stage, the first in which the descent target location was on land, and also the first ever successful landing. Prior to this flight, SpaceX's two previous attempts at a vertical landing and booster recovery ended in failure to recover the rocket. The success of flight 20 marked a significant milestone en route to the company's goal of creating a reusable rocket system that would significantly reduce the cost of launching payloads into orbit. Falcon 9 flight 20 was the first launch of the substantially upgraded Falcon 9 Full Thrust version of the Falcon 9 launch vehicle. It carried 11 Orbcomm-OG2 satellites to Earth orbit. The launch was also notable as it was the first SpaceX launch following the catastrophic failure of a Falcon 9 v1.1 launch vehicle's second stage on Falcon 9 Flight 19 in June 2015.
Launch schedule history SES announced in February 2015 that it would provide the payload on the first launch of the revised-design Falcon 9 Full Thrust (also called Falcon 9 v1.2 ). At the time, SES expected its SES-9 geostationary communications satellite would launch by September 2015. SES kept the decision despite the loss of the launch vehicle and payload of another SpaceX mission in June 2015, but postponed the launch until late 2015. On 16 October 2015, after considering all options, SpaceX announced a change: Orbcomm's 11 OG2 satellites would be the payload on the return-to-flight launch of the redesigned Falcon 9 instead of SES-9. The Orbcomm payload with its lower orbit would allow SpaceX to test relighting the second-stage engine, a capability required to successfully put the heavier SES-9 on a geostationary orbit. The launch was delayed to mid-December or later, while SES-9 was scheduled to follow within a few weeks. A required pre-launch static-fire test was initially scheduled for 16 December 2015, but a few issues emerged with the new processes required for the colder propellants for the launch vehicle and the related ground support equipment. The test was successfully carried out on 18 December 2015, which resulted in a launch delay of one day to 19 December 2015 (local time). The launch was subsequently delayed an additional day after statistical analysis indicated a somewhat higher probability of recovering the booster on the later date.
New launch vehicle
The Falcon 9 Full Thrust launch vehicle used on flight 20 had a number of significant modifications from the previous Falcon 9 v1.1 vehicle. These included:
increased second stage tank length and propellant volume larger Merlin 1D vacuum engine nozzle larger and stronger interstage with revised stage-separation mechanism revised grid fin design to support the continuation of the Falcon 9 booster controlled-descent and landing tests, and ultimately, the operational Reusable Falcon 9 launch system upgraded structure in the landing legs, also to support the reusable development program and objectives upgraded first stage structure and octaweb engine support structure denser liquid oxygen and RP-1 propellants through the use of subcooling, refrigeration below the typical temperature of previous Falcon 9 launch conditions. first stage booster can reach low Earth orbit as a single stage if not carrying the upper stage and a heavy satellite.
Launch and on-orbit test
Flight 20 was launched on 22 December 2015 at 01:29 UTC (21 December, 8:29 pm local time).
Second stage re-ignition Following successful launch and deployment of the OG2 satellites, the Merlin Vacuum (1D) second-stage engine successfully re-ignited, demonstrating its capability to launch SES-9 into geostationary transfer orbit. The engine burn de-orbited the second stage as planned for a destructive re-entry, preventing it from becoming space debris.
Payload Falcon 9 Flight 20 carried 11 Orbcomm-OG2 second-generation satellites, which will provide enhanced ORBCOMM messaging capabilities, increased data capacity, and automatic identification systems (AIS) service. All 11 satellites were successfully deployed by the Falcon 9 second stage, beginning approximately 14 minutes after takeoff. All 11 satellites successfully checked in with ground control stations. The satellites were placed by the launch vehicle "within a fraction of a degree in inclination and 5 km (3.1 mi) in altitude of the intended orbit, "and by 9 January 2016, were in the middle of on-orbit testing, while executing propulsion maneuvers that had spread the 11 satellites over a 6,400 km (4,000 mi) orbital arc. Initial ORBCOMM customer message traffic began to be tested by late January 2016. Satflare reported in February 2016 that one of the 11 flight 2 satellites will reenter Earth's atmosphere in late-February 2016. The satellite manufacturer, Sierra Nevada Corporation, completed checkout work and handed all 11 satellites off to ORBCOMM in early March 2016.
Post-mission landing
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