Falcon 9 first-stage landing tests

The overall objective of the program is to privately develop reusable rockets using vertical-landing technology so as to substantially reduce the cost of space access.

SpaceX first announced in March 2013, that it would instrument and equip subsequent Falcon 9 first stages as controlled-descent test vehicles, able to propulsively decelerate to a soft touchdown over the water surface.

The company expected to begin these flight tests in 2013, with an attempt to return the vehicle to the launch site for a powered landing no earlier than mid-2014.

[8][9] SpaceX announced in February 2014 that they intended to continue over-water tests of the first stage until mastering precision control of the vehicle from hypersonic speed all the way through subsonic regimes.

[9] Subsequent tests, starting with the CRS-5 mission in January 2015, attempted to land the first stage on an autonomous spaceport drone ship stationed off the Florida coastline or in the Pacific Ocean depending on launch site.

[9][12] In detailed information disclosed in the Falcon 9 flight 6 launch license for the CASSIOPE mission, SpaceX said it would fire three of the nine Merlin 1D engines initially to slow the horizontal velocity of the rocket and begin the attempt at a controlled descent.

[6] This first experimental descent was considered successful, achieving substantial test milestones and collecting engineering data, despite losing the stage into the ocean.

[19] SpaceX tested a large amount of new technology on this flight, and, combining those results with the advances made on the Grasshopper demonstrator, the company believed it had "all the pieces of the puzzle".

[9][23] During the second test, the first stage was traveling at a velocity of Mach 10 (10,200 km/h; 6,340 mph)[23] at an altitude of 80 kilometers (260,000 ft)[24] at the time of the high-altitude turn-around maneuver, followed by ignition of three of the nine main engines for the initial deceleration and placement onto its descent trajectory.

[31] Results of the post-landing analysis showed that the hull integrity was lost as the 46-metre (150 ft)-tall first stage fell horizontally, as planned, onto the ocean surface following the landing.

The data was collected by NASA in a joint arrangement with SpaceX as part of research on retropropulsive deceleration technologies in order to develop new approaches to Mars atmospheric entry.

All phases of the night-time flight test on the first stage were successfully imaged except for the final landing burn, as that occurred below the clouds where the IR data was not visible.

[17] The research team is particularly interested in the 70–40-kilometer (43–25 mi) altitude range of the SpaceX "reentry burn" on the Falcon 9 Earth-entry tests as this is the "powered flight through the Mars-relevant retropulsion regime" that models Mars entry and descent conditions.

[16] SpaceX had planned to make the sixth controlled-descent test flight and second[34] landing attempt on their drone ship no earlier than February 11, 2015.

[34][35][36] According to regulatory paperwork filed in 2014, SpaceX plans called for the sixth test flight to occur on a late January 2015 launch attempt.

[37] This issue was resolved within days of the ship's return to Jacksonville, and by January 15, SpaceX was unambiguous about its plans to attempt a landing of the first stage following the boost phase of the Deep Space Climate Observatory mission.

However the touchdown on the corner of the barge was a hard landing and most of the rocket body fell into the ocean and sank; SpaceX published a short clip of the crash.

[57] On April 15, SpaceX released a video of the terminal phase of the descent, the landing, the tip over, and the resulting deflagration as the stage broke up on the deck of the ASDS.

[45][59] This was the first time in history that a rocket first stage returned to Earth after propelling an orbital launch mission and achieved a controlled vertical landing.

[63][64][needs update] Both options to attempt landing on the ground pad or on the drone ship at sea remained open until the day of the launch.

The final decision to return the booster to Cape Canaveral was made based on a number of factors, including weather at the potential landing sites.

[73][74] On March 4, 2016, Falcon 9 flight 22 launched the 5,271 kg (11,620 lb) heavy SES-9 communications satellite,[75][76] the rocket's largest payload yet targeting a highly-energetic geosynchronous transfer orbit (GTO).

Consequently, the Falcon 9 first stage followed a ballistic trajectory after separation and re-entered the atmosphere at high velocity with very little fuel to mitigate potential aerodynamic damage.

Nine minutes after liftoff, the booster landed vertically on the drone ship Of Course I Still Love You, 300 km (190 mi) from the Florida coastline, achieving a long-sought-after milestone for the SpaceX reusability development program.

On May 6, 2016, Falcon 9 flight 24 delivered the JCSAT-14 satellite on a geostationary transfer orbit (GTO) while the first stage conducted a re-entry burn under ballistic conditions without prior boostback.

[79] Pursuing their experiments to test the limits of the flight envelope, SpaceX opted for a shorter landing burn with three engines instead of the single-engine burns seen in earlier attempts; this approach consumes less fuel by leaving the stage in free fall as long as possible and decelerating more sharply, thereby minimizing the amount of energy expended to counter gravity.

[81] On May 27, 2016, Falcon 9 flight 25 delivered THAICOM 8 to a supersynchronous transfer orbit; despite high re-entry speed, the first stage again landed successfully on the SpaceX drone ship.

The landing failed in its final moments due to low thrust on one of the first stage engines, caused by the exhaustion of its liquid oxygen fuel supply.

[89] SpaceX continued to return a number of first stages in both ground and sea landings to clarify the procedures needed to re-use flown boosters.

The company had hoped to begin offering pre-flown Falcon 9 rocket stages commercially by the end of 2016,[90][91] but the first re-used booster eventually took off on March 30, 2017, with the SES-10 mission.