Falcon 9 flight 20 (also known as Orbcomm OG2 M2) was a

Falcon 9 Falcon 9 is a Reusable launch system#Partial reusable launch systems, partially reusable, two-stage-to-orbit, medium-lift launch vehicle designed and manufactured in the United States by SpaceX. The first Falcon 9 launch was on June 4, 2010, an ...

space launch that occurred on 22 December 2015 at 01:29:00

UTC Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time. It establishes a reference for the current time, forming the basis for civil time and time zones. UTC facilitates international communica ...

(21 December, 8:29:00 pm local time). It was the first time that the

first stage First stage or First Stage may refer to: * First Stage Children's Theater, a professional American children's theater based in Milwaukee, Wisconsin * First stage (rocketry), the first stage of a multistage rocket * the first reading of a bill in t ...

of an orbital rocket made a successful return and

vertical landing Vertical takeoff, vertical landing (VTVL) is a form of takeoff and landing for rockets. Multiple VTVL craft have flown. A notable VTVL vehicle was the Apollo Lunar Module which delivered the first humans to the Moon. Building on the decades of ...

. The successful landing of the first stage at

Landing Zone 1 Landing Zone 1 and Landing Zone 2, also known as LZ-1 and LZ-2 respectively, are landing facilities at Cape Canaveral Space Force Station used by SpaceX. They allow the company to land the first stage of its Falcon 9 rocket or the two side boost ...

, near the launch site, was the result of a five-year technology development program to develop a

reusable launch system A reusable launch vehicle has parts that can be recovered and reflown, while carrying payloads from the surface to outer space. Rocket stages are the most common launch vehicle parts aimed for reuse. Smaller parts such as fairings, boosters ...

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 Falcon 9 Full Thrust (also known as Falcon 9 v1.2) is a Reusable launch system#Partial reusable launch systems, partially reusable, two-stage-to-orbit, medium-lift launch vehicle when reused and Heavy-lift launch vehicle when expended designed an ...

version of the Falcon 9

launch vehicle A launch vehicle is typically a rocket-powered vehicle designed to carry a payload (a crewed spacecraft or satellites) from Earth's surface or lower atmosphere to outer space. The most common form is the ballistic missile-shaped multistage ...

. It carried 11 Orbcomm-OG2 satellites to

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

orbit. The launch was also notable as it was the first

SpaceX Space Exploration Technologies Corp., commonly referred to as SpaceX, is an America, American space technology company headquartered at the SpaceX Starbase, Starbase development site in Starbase, Texas. Since its founding in 2002, the compa ...

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

(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 ORBCOMM is an American company that offers industrial IoT solutions designed to track, monitor, and control fixed and mobile assets in markets including transportation, heavy equipment, maritime, oil and gas, utilities and government. The compan ...

'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 A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular orbit, circular geosynchronous or ...

. 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 Statistical inference is the process of using data analysis to infer properties of an underlying probability distribution.Upton, G., Cook, I. (2008) ''Oxford Dictionary of Statistics'', OUP. . Inferential statistical analysis infers properties of ...

indicated a somewhat higher probability of recovering the booster on the later date.

New launch vehicle

The

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 A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or another motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicle ...

volume * larger Merlin 1D vacuum engine nozzle * larger and stronger interstage with revised stage-separation mechanism * revised

grid fin Grid fins (or lattice fins) are a type of flight control surfaces, flight control surface used on rockets and bombs, sometimes in place of more conventional control surfaces, such as planar fins. They were developed in the 1950s by a team led by ...

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 Liquid oxygen, sometimes abbreviated as LOX or LOXygen, is a clear cyan liquid form of dioxygen . It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an application which is ongoing. Physical ...

and

RP-1 RP-1 (Rocket Propellant-1 or Refined Petroleum-1) and similar fuels like RG-1 and T-1 are highly refined kerosene formulations used as rocket fuel. Liquid-fueled rockets that use RP-1 as fuel are known as kerolox rockets. In their engines, RP- ...

propellants through the use of

subcooling The term subcooling (also called undercooling) refers to the intentional process of cooling a liquid below its normal boiling point. For example, water boils at 373 K; at room temperature (293 K) liquid water is termed "subcooled". Subc ...

, refrigeration below the typical temperature of previous Falcon 9 launch conditions. * first stage booster can reach

low Earth orbit A low Earth orbit (LEO) is an geocentric orbit, orbit around Earth with a orbital period, period of 128 minutes or less (making at least 11.25 orbits per day) and an orbital eccentricity, eccentricity less than 0.25. Most of the artificial object ...

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

(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 In space mission design, a geostationary transfer orbit (GTO) or geosynchronous transfer orbit is a highly elliptical type of geocentric orbit, usually with a perigee as low as low Earth orbit (LEO) and an apogee as high as geostationary orbit ...

. The engine burn de-orbited the second stage as planned for a destructive

re-entry Atmospheric entry (sometimes listed as Vimpact or Ventry) is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet, or natural satellite. Atmospheric entry may be ''uncontrolled entry ...

, preventing it from becoming

space debris Space debris (also known as space junk, space pollution, space waste, space trash, space garbage, or cosmic debris) are defunct human-made objects in spaceprincipally in Earth orbitwhich no longer serve a useful function. These include dere ...

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 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 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 Sierra Nevada Corporation (also styled SNC) is an American aerospace, defense, electronics, engineering and manufacturing corporation that specializes in aircraft modification, integration and other space technologies. The corporation contracts ...

, completed checkout work and handed all 11 satellites off to ORBCOMM in early March 2016.

Post-mission landing

SpaceX performed a controlled-descent test on the rocket's first stage — the eighth propulsive return test of the series. For the first time, SpaceX was able to vertically land and successfully recover the first stage. Earlier tests had proven the high-altitude deceleration and atmospheric re-entry portions of the test protocol, but no landing attempt had previously been successful, including two attempts earlier in 2015 to land a first stage on a floating landing platform. The entire controlled-descent through the

atmosphere An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...

and landing attempt is an arrangement that is unusual for other

s. The flight test was planned for the twentieth Falcon 9 launch, even after the manifested payload was switched from SES-9 to the 11-satellite Orbcomm OG-2 payload.SpaceX preparing for Static Fire test on first Full Thrust Falcon 9 First Stage
24 October 2015, accessed 26 October 2015 The test was scheduled for and successfully carried out on 21 December 2015, when the first stage landed intact at

. SpaceX decided not to fly the B1019 again. Rather, the rocket was moved a few miles north to Launch Pad 39A, recently refurbished by SpaceX at the adjacent

Kennedy Space Center The John F. Kennedy Space Center (KSC, originally known as the NASA Launch Operations Center), located on Merritt Island, Florida, is one of the NASA, National Aeronautics and Space Administration's (NASA) ten NASA facilities#List of field c ...

, to conduct a static fire test. This test aimed to assess the health of the recovered booster and the capability of this rocket design to fly repeatedly in the future. The historic booster was eventually displayed outside

SpaceX headquarters Space Exploration Technologies Corp., commonly referred to as SpaceX, is an American space technology company headquartered at the Starbase development site in Starbase, Texas. Since its founding in 2002, the company has made numerous a ...

Hawthorne, California Hawthorne is a city in southwestern Los Angeles County, California. It is part of a seventeen-city subregion of the Los Angeles metropolitan area commonly known as the South Bay (Los Angeles County), South Bay. As of the 2020 United States cens ...

Evaluation of the recovered first stage

On 31 December 2015, SpaceX announced that no damage had been found on the stage and that it was ready to perform a

static fire Launch vehicle system tests assess the readiness of a launch system to safely reach orbit. Launch vehicles undergo system tests before they launch. Wet dress rehearsals (WDR) and more extensive static fire tests prepare fully assembled launch veh ...

again.Falcon 9 back in the hangar at Cape Canaveral. No damage found, ready to fire again.
Elon Musk, via Twitter, 31 December 2015, accessed 2 January 2016 SpaceX had initially moved the booster to their hangar at LC-39A, but they moved the stage to SLC-40 — the pad from which it was launched — on 12 January 2016. On 15 January 2016, SpaceX conducted the static fire test on the recovered booster, obtaining good overall results except for one of the outer engines experiencing thrust fluctuations. Elon Musk reported that this may have been due to debris ingestion.Falcon 9 booster fires again at Cape Canaveral
Spaceflight Now, 16 January 2016, accessed 18 January 2016 In February 2016, SpaceX President and COO

Gwynne Shotwell Gwynne Shotwell ( Rowley, previously Gurevich; born November 23, 1963) is an American businesswoman and engineer. She is the president and chief operating officer of SpaceX, an American space transportation company, where she is responsible fo ...

indicated that some unspecified modifications to the stage design would occur as a result of the booster's post-flight evaluation and static fire.

Display

In August 2016, the returned first stage was put on permanent display on a stand outside SpaceX headquarters in

Live coverage

SpaceX live coverage of the launch and landing included cheering crowds and tours of the SpaceX manufacturing and launch facilities. ''

The Atlantic ''The Atlantic'' is an American magazine and multi-platform publisher based in Washington, D.C. It features articles on politics, foreign affairs, business and the economy, culture and the arts, technology, and science. It was founded in 185 ...

'' technology editor Robinson Meyer called the scripted broadcast "a way of treating a rocket launch not like a dry engineering procedure, but like some combination of the

Macy's Thanksgiving Day Parade The Macy's Thanksgiving Day Parade is an annual parade in New York City presented by the American-based department store chain Macy's. The Parade first took place in 1924, tying it for the second-oldest Thanksgiving parade in the United States ...

and the

Super Bowl The Super Bowl is the annual History of the NFL championship, league championship game of the National Football League (NFL) of the United States. It has served as the final game of every NFL season since 1966 NFL season, 1966 (with the excep ...

". Upon the unprecedented first stage landing, a SpaceX engineer announced "The Falcon has landed", reminding audiences of the first Apollo landing.

References

External links

SpaceX video of full mission

Musk pre-launch backgrounder on Falcon 9 Flight 20
, 22 December 2015
Round-trip rocket flight gives SpaceX a trifecta of successes
Spaceflight Now, 22 December 2015
Elon Musk's SpaceX returns to flight and pulls off dramatic, historic landing
''Washington Post'', December 2015 {{Orbital launches in 2015 2015 in spaceflight Falcon 9 2015 in Florida Rocket launches in 2015