SpaceX reusable launch system development program
|SpaceX reusable launch system development program|
Falcon 9 Flight 20's first stage landing vertically on solid ground in December 2015
|Type of project||Privately funded technology development|
|Products||Falcon 9, Falcon Heavy, Interplanetary Transport System|
|Established||Publicly announced 2011|
The SpaceX reusable launch system development program is a privately funded program to develop a set of new technologies for an orbital launch system that may be reused many times in a manner similar to the reusability of aircraft. The company SpaceX is developing the technologies over a number of years to facilitate full and rapid reusability of space launch vehicles. The project's long-term objectives include returning a launch vehicle first stage to the launch site in minutes and to return a second stage to the launch pad following orbital realignment with the launch site and atmospheric reentry in up to 24 hours. SpaceX's long term goal is that both stages of their orbital launch vehicle will be designed to allow reuse a few hours after return.
The program was publicly announced in 2011. SpaceX first achieved a successful landing and recovery of a first stage in December 2015. The first re-flight of a landed first stage occurred in March 2017 with the second occurring in June 2017, that one only five months after the maiden flight of the booster. The third attempt occurred in October 2017 with the SES-11/EchoStar-105 mission. Second flights of refurbished first stages then became routine.
The reusable launch system technology was developed and initially used for the first stages of the Falcon family of rockets. After stage separation, the return process involves flipping the booster around, an optional boostback burn to reverse its course, a reentry burn, controlling direction to arrive at the landing site and a landing burn to effect the final low-altitude deceleration and touchdown.
SpaceX is intending to develop technology to extend reusable flight hardware to second stages, a more challenging engineering problem because the vehicle is travelling at orbital velocity, which is considered paramount to the plans Elon Musk is championing to enable the settlement of Mars. It is thus planned to be developed for all of the flight hardware for the new SpaceX vehicles planned to transit to Mars, with initial test flights expected no earlier than 2020. SpaceX may also experiment with second stage recovery on a few select Falcon 9 flights or Falcon Heavy flights.
- 1 History
- 2 Technologies
- 3 Economics of rocket reuse
- 4 Technical feasibility
- 5 Test program
- 5.1 Flight test vehicles
- 5.2 Falcon 9 booster post-mission flight tests
- 5.3 First-stage reuse
- 5.4 Fairing reuse
- 5.5 Second-stage reuse
- 6 Operational flow
- 7 See also
- 8 References
- 9 External links
SpaceX initially attempted to land the first stage of the Falcon 1 by parachute, however the stage did not survive the re-entry into the atmosphere. They continued to experiment with parachutes on the earliest Falcon 9 flights after 2010. SpaceX subsequently switched its focus to developing a powered descent landing system.
The broad outline of the reusable launch system was first publicly described in September 2011. SpaceX said it would attempt to develop powered descent and recovery of both Falcon 9 stages—a fully vertical takeoff, vertical landing (VTVL) rocket. The company produced a computer-animated video depicting a notional view of the first stage returning tail-first for a powered descent and the second stage with a heat shield, reentering head first before rotating for a powered descent. In September 2012, SpaceX began flight tests on a prototype reusable first stage with the suborbital Grasshopper rocket. Those tests continued into 2014, including testing of a second and larger prototype vehicle, F9R Dev1.
News of the Grasshopper test rocket had become public a few days earlier, when the US Federal Aviation Administration released a draft Environmental Impact Assessment for the SpaceX Test Site in Texas, and the space media had reported it. In May 2012, SpaceX obtained a set of atmospheric test data for the recovery of the Falcon 9 first stage based on 176 test runs in the NASA Marshall Space Flight Center wind tunnel test facility. The work was contracted for by SpaceX under a reimburseable Space Act Agreement with NASA.
In 2012, it was projected that the first-stage separation of a reusable Falcon 9 rocket would occur at a velocity of approximately Mach 6 (2.0 km/s; 7,400 km/h; 4,600 mph) rather than Mach 10 (3.4 km/s; 12,000 km/h; 7,600 mph) for an expendable Falcon 9, to provide the residual fuel necessary for the deceleration and turnaround maneuver and the controlled descent and landing.
In November 2012, CEO Elon Musk announced SpaceX's plans to build a second, much larger, reusable rocket system, this one to be powered by LOX/methane rather than LOX/RP-1 used on Falcon 9 and Falcon Heavy. The new system was to be "an evolution of SpaceX's Falcon 9 booster", and SpaceX reiterated their commitment to develop a breakthrough in vertical landing technology. By the end of 2012, the demonstration test vehicle, Grasshopper, had made three VTVL test flights—including a 29-second hover flight to 40 meters (130 ft) on December 17, 2012. In early March 2013, SpaceX successfully tested Grasshopper for a fourth time when it flew to an altitude of over 80 meters (260 ft).
In March 2013, SpaceX announced that it would instrument and equip subsequent Falcon 9 first-stages as controlled descent test vehicles, with plans for over-water propulsively-decelerated simulated landings beginning in 2013, with the intent to return the vehicle to the launch site for a powered landing—possibly as early as mid-2014. The April 2013 draft Environmental Impact Statement for the proposed SpaceX South Texas Launch Site includes specific accommodations for return of the Falcon 9 first-stage boosters to the launch site. Elon Musk first publicly referred to the reusable Falcon 9 as the Falcon 9-R in April 2013.
In September 2013, SpaceX successfully relit three engines of a spent booster on an orbital launch, and the booster re-entered the atmosphere at hypersonic speed without burning up. With the data collected from the first flight test of a booster-controlled descent from high altitude, coupled with the technological advancements made on the Grasshopper low-altitude landing demonstrator, SpaceX announced it believed it was ready to test a full land-recovery of a booster stage. Based on the positive results from the first high-altitude flight test, SpaceX advanced the expected date of a test from mid-2014 to early 2015[clarification needed], with the intention of doing so on the next Space Station cargo resupply flight pending regulatory approvals. That flight took place on April 18, 2014.
Musk stated in May 2013 that the goal of the program is to achieve full and rapid reusability of the first stage by 2015, and to develop full launch vehicle reusability following that as "part of a future design architecture".
In February 2014, SpaceX made explicit that the newly defined super-heavy launch vehicle for what was then called Mars Colonial Transporter would also make use of the reusable technology. This was consistent with Musk's strategic statement in 2012 that "The revolutionary breakthrough will come with rockets that are fully and rapidly reusable. We will never conquer Mars unless we do that. It'll be too expensive. The American colonies would never have been pioneered if the ships that crossed the ocean hadn't been reusable."
Also in May 2014, SpaceX publicly announced an extensive test program for a related reusable technology: a propulsively-landed space capsule called DragonFly. The tests were to be run in Texas at the McGregor Rocket Test Facility in 2014–2015.
In June 2014, COO Gwynne Shotwell clarified that all funding for development and testing of the reusable launch system technology development program is private funding from SpaceX, with no contribution by the US government.  As of 2017 SpaceX had spent over a billion dollars on the development program.
For the first time, SpaceX stated in July 2014 that they are "highly confident of being able to land successfully on a floating launch pad or back at the launch site and refly the rocket with no required refurbishment."
By late 2014, SpaceX suspended or abandoned the plan to recover and reuse the Falcon 9 second stage; the additional mass of the required heat shield, landing gear, and low-powered landing engines would incur too great a performance penalty.
In September 2016, SpaceX announced that development was underway to extend the reusable flight hardware to second stages, a more challenging engineering problem because the vehicle is travelling at orbital velocity. The reusable technology was to have been extended to the 2016 designs of both the tanker and crewed spaceship upper stage variants as well as the first stage of the ITS launch vehicle for the Interplanetary Transport System, and is considered paramount to the plans Elon Musk is championing to enable the settlement of Mars. In 2016, initial test flights of an Interplanetary Transport System vehicle were expected no earlier than 2020.
In 2017 SpaceX was making test flight progress in incrementally and iteratively developing a fairing recovery system. In July 2017, Musk said "we are quite close to being able to recover the fairing. ... We've got a decent shot of recovering a fairing by the end of the year, and reflight by late this year or early next." The cost savings to SpaceX of recovering the fairing is expected to be on the order of US$5 million. Together, the booster stage and the fairing make up approximately 80 percent of the cost of a launch.
Despite 2014 plans to suspend development of Falcon 9 second stage reuse, Musk further commented in July 2017 that a few experimental attempts would be made on particular future flights to bring a Falcon 9 second stage back.
Several new technologies needed to be developed and tested to facilitate successful launch and recovery of both stages of the SpaceX reusable rocket launching system. Following the completion of the third high-altitude controlled-descent test, and the completion of the third low-altitude flight of the second-generation prototype test vehicle (plus eight flights of the first-generation Grasshopper prototype flight test vehicle), SpaceX indicated that they are now able to consistently "reenter from space at hypersonic velocity, restart main engines twice, deploy landing legs and touch down at near zero velocity."
The technologies that were developed for this program, some of which are still being refined, include:
- restartable ignition system for the first-stage booster. Restarts are required at both supersonic velocities in the upper atmosphere—in order to decelerate the high velocity away from the launch pad and put the booster on a descent trajectory back toward the launch pad—and at high transonic velocities in the lower atmosphere—in order to slow the terminal descent and to perform a soft landing.
- new attitude control technology—for the booster stage and second stage—to bring the descending rocket body through the atmosphere in a manner conducive both to non-destructive return and sufficient aerodynamic control such that the terminal phase of the landing is possible. This includes sufficient roll control authority to keep the rocket from spinning excessively as occurred on the first high-altitude flight test in September 2013, where the roll rate exceeded the capabilities of the booster attitude control system (ACS) and the fuel in the tanks "centrifuged" to the side of the tank shutting down the single engine involved in the low-altitude deceleration maneuver. The technology needs to handle the transition from the vacuum of space at hypersonic conditions, decelerating to supersonic velocities and passing through transonic buffet, before relighting one of the main-stage engines at terminal velocity.
- hypersonic grid fins were added to the booster test vehicle design beginning on the fifth ocean controlled-descent test flight in 2014 in order to enable precision landing. Arranged in an "X" configuration, the grid fins control the descending rocket's lift vector once the vehicle has returned to the atmosphere to enable a much more precise landing location. Iteration on the design continued into 2017. Larger and more robust grid fins, made from forged titanium and left unpainted, were first tested in June 2017, and will be used on all reusable Block 5 Falcon 9 first stages starting in 2018.
- throttleable rocket engine technology is required to reduce engine thrust because the full thrust of even a single Merlin 1D engine exceeds the weight of the nearly empty booster core.
- terminal guidance and landing capability, including a vehicle control system and a control system software algorithm to be able to land a rocket with the thrust-to-weight ratio of the vehicle greater than one, with closed-loop thrust vector and throttle control
- navigation sensor suite for precision landing
- a large floating landing platform in order to test pinpoint landings prior to receiving permission from the US government to bring returning rocket stages into US airspace over land. In the event, SpaceX built the autonomous spaceport drone ship in 2014, and conducted an initial flight test and landing attempt in January 2015.
- large-surface-area thermal protection system to absorb the heat load of deceleration of the second stage from orbital velocity to terminal velocity
- lightweight, deployable landing gear for the booster stage. In May 2013, the design was shown to be a nested, telescoping piston on an A-frame. The total span of the four carbon fiber/aluminum extensible landing legs is approximately 18 meters (60 ft), and weigh less than 2,100 kilograms (4,600 lb). Deployment system uses high-pressure Helium as the working fluid. With Flight 25 it was announced that each landing leg contained a "crush core", to absorb the impact of landing for particularly hard landings.
Economics of rocket reuse
In order to make the Falcon 9 reusable and return to the launch site, extra propellant and landing gear must be carried on the first stage, requiring around a 30 percent reduction of the maximum payload to orbit in comparison with the expendable Falcon 9. Reflight of a previously used stage on a subsequent flight is dependent on the condition of the landed stage, and is a technique that has seen little use outside of the Space Shuttle's reusable solid rocket boosters. In September 2013, SpaceX said that if all aspects of the test program were successful and if a customer is interested, the first reflight of a Falcon 9 booster stage could happen as early as late 2014. In December 2015, following the recovery of the first stage from December 22 launch, SpaceX projected that the first reflight of a recovered booster would likely occur in 2016, but that their plan was to not refly December 22 recovered stage for that purpose. Musk projected in 2015 that the reflight step of the program would be "straightforward," because of the multiple full duration firings of the engines that had been done on the ground, and the multiple engine restarts that had been demonstrated by that time, with no significant degradation seen. In 2015, industry analysts continued to forecast problems that could prevent economic reuse because costs to refurbish and relaunch the stage were not yet demonstrated, and the economic case for reuse would necessarily be highly dependent on launching frequently.
If SpaceX is successful in developing the reusable technology, it is expected to significantly reduce the cost of access to space, and change the increasingly competitive market in space launch services. Michael Belfiore wrote in Foreign Policy in 2013 that, at a published cost of US$56.5 million per launch to low Earth orbit, "Falcon 9 rockets are already the cheapest in the industry. Reusable Falcon 9s could drop the price by an order of magnitude, sparking more space-based enterprise, which in turn would drop the cost of access to space still further through economies of scale." Even for military launches, which have a number of contractual requirements for additional launch services to be provided, SpaceX's price is under US$100 million.
Space industry analyst Ajay Kothari has noted that SpaceX reusable technology could do for space transport "what jet engines did for air transportation sixty years ago when people never imagined that more than 500 million passengers would travel by airplanes every year and that the cost could be reduced to the level it is—all because of passenger volume and reliable reusability." SpaceX said in January 2014 that if they are successful in developing the reusable technology, launch prices of around US$5 to 7 million for a reusable Falcon 9 were possible, and following the successful first stage recovery in December 2015, Musk said that "the potential cost reduction over the long term is probably in excess of a factor of 100."
As of March 2014[update] launch service providers who compete with SpaceX were not planning to develop similar technology or offer competing reusable launcher options. Neither ILS, which markets launches of the Russian Proton rocket; Arianespace; nor SeaLaunch were planning on developing and marketing reusable launch vehicle services. SpaceX was the only competitor that projected a sufficiently elastic market on the demand side to justify the costly development of reusable rocket technology and the expenditure of private capital to develop options for that theoretical market opportunity.
As of 2014[update], the Falcon 9 v1.1 rocket was designed with about 30 percent more capacity than its official payload specifications; the additional performance was reserved for SpaceX to perform first-stage re-entry and landing tests towards reusability while still achieving the specified orbital payload delivery for customers.
In order to achieve the full economic benefit of the reusable technology, it is necessary that the reuse be both rapid and complete—without the long and costly refurbishment period or partially reusable design that plagued earlier attempts at reusable launch vehicles. SpaceX has been explicit that the "huge potential to open up space flight" is dependent on achieving both complete and rapid reusability. CEO Musk stated in 2014 that success with the technology development effort could reduce "the cost of spaceflight by a factor of 100" because the cost of the propellant/oxidizer on the Falcon 9 is only 0.3 percent of the total cost of the vehicle.
Separate from the market competition brought about by SpaceX lower launch prices and the potential future of even more radically lower launch prices if the technology can be completed successfully, Aviation Week said in 2014 that "SpaceX reusable launch work is an R&D model"—"The audacity of the concept and speed of the program’s progress make it an exemplar. ... [the] breakneck pace of development has been almost Apollo-like in its execution... [even while] success is far from guaranteed."
On March 9, 2016, SpaceX President Gwynne Shotwell gave a more realistic appraisal of the potential savings of a reused launch now that attempts to reuse the second stage had been abandoned due to cost and weight issues. She said at US$1 million cost of refueling and US$3 million cost of refurbishing a used first stage could potentially allow a launch to be priced as low as US$40 million, a 30% saving. SpaceX biggest customer SES said it wants to be the first to ride a reused vehicle, however it wants a launch price of US$30 million or a 50% saving to offset the risk of pioneering the process.
According to Elon Musk, almost every piece of the Falcon should be reused over 100 times. Heat shields and a few other items should be reused over 10 times before replacement. In March 2017, SpaceX announced progress in their experiments to recover, and eventually reuse, the 6-million dollar payload fairing. On the SES-10 mission, one of the fairing halves performed a controlled atmospheric reentry and splashdown using thrusters and a steerable parachute; fairings are eventually slated to land on a floating "bouncy castle" structure.
SpaceX began re-flight of previously-launched booster stages in 2017. The first re-flight was accomplished in March 2017, nearly a year after the booster's maiden flight; the second was in June 2017, only five months after its maiden flight. Both were successful, and both insurers and launch service customers are readily supporting the newly emerging market in launch services provided by multiple-use boosters.
Prior to the reusability program's success in December 2015, the return of an orbital launch system booster rocket had never been accomplished, and many questioned both technical and economic feasibility. And even after this success, the rapid reuse of a rocket has not been attempted. Developing a reusable rocket is extremely challenging due to the small percentage of a rocket's mass that can make it to orbit. Typically, a rocket's payload is only about 3% of the mass of the rocket which is also roughly the amount of mass in fuel that is required for the vehicle's re-entry.
Elon Musk said at the beginning of the program that he believed the return, vertical landing and recovery was possible because the SpaceX manufacturing methodologies result in a rocket efficiency exceeding the typical 3% margin. A SpaceX rocket operating in the reusable configuration has approximately 30% less payload lift capacity than the same rocket in an expendable configuration.
Although the reusable launch system technology was developed and initially used for the first stages of the Falcon family of rockets it is particularly well suited to the Falcon Heavy where the two outer cores separate from the rocket earlier in the flight, and are therefore moving more slowly at stage separation. For example, on Falcon 9 flight 20, the speed at separation was close to 6000 km/h and this allowed a return to near the launch site. On flight 22, going to a more-energetic GTO orbit, the higher velocity at separation was between 8000 and 9000 km/h. At these faster speeds it is not possible to return the booster to near the launch site for a landing; if a landing is attempted it needs to be hundreds of kilometers downrange on an autonomous droneship.
In 2013 SpaceX was testing reusable technologies both for its first-stage booster launch vehicle designs (with three test vehicles : Grasshopper, F9R Dev1, and F9R Dev2) — and for its new reusable Dragon V2 space capsule (with a low-altitude test vehicle called DragonFly).
SpaceX has publicly disclosed a multi-element, incremental test program for booster stages that includes four aspects:
- low-altitude (less than 760 m/2,500 ft), low-velocity testing of its single-engine Grasshopper technology-demonstrator at its Texas test site
- low-altitude (less than 3,000 m/9,800 ft), low-velocity testing of a much larger, second-generation, three-engine test vehicle called F9R Dev1. The second generation vehicle includes extensible landing legs and will be tested at the Texas test site
- high-altitude, mid-velocity testing was planned but cancelled in favor of post-mission re-entry tests of first-stage boosters. It would have used F9R Dev2 at a SpaceX leased facility at Spaceport America in New Mexico.
- high-altitude (91 km/300,000 ft), very-high-velocity (approximately 2.0 km/s; 6,500 km/h; 4,100 mph; Mach 6) ballistic reentry, controlled-deceleration and controlled-descent tests of post-mission (spent) Falcon 9 booster stages following a subset of Falcon 9 launches that began in 2013.
Eight low-altitude booster flight tests were made by Grasshopper in 2012 and 2013. The first booster return controlled-descent test from high-altitude was made in September 2013, with a second test in April, a third test flight in July and a fourth test in September 2014. All four test flights to date were intended to be over-water, simulated landings. Five low-altitude booster flight tests of F9R Dev1 were flown during April–August 2014, before the vehicle self-destructed for safety reasons on the fifth flight.
Flight test vehicles
SpaceX used a set of experimental technology-demonstrator, suborbital reusable launch vehicles (RLV) to begin flight testing their reusable rocket technologies in 2012. Two versions of the prototype reusable test rockets were built—the 106-foot tall Grasshopper (formerly designated as Grasshopper v1.0) and the 160-foot tall Falcon 9 Reusable Development Vehicle, or F9R Dev1—formerly known as Grasshopper v1.1—as well as a capsule prototype for testing propulsive landings of the Dragon crew and cargo capsule for the Falcon 9—DragonFly. Grasshopper was built in 2011–2012 for low-altitude, low-velocity hover testing that began in September 2012 and concluded in October 2013 after eight test flights. The second prototype vehicle design, F9R Dev1, was built on the much larger Falcon 9 v1.1 booster stage was used to further extend the low-altitude flight testing envelope on a vehicle that better matched the actual flight hardware, and made five test flights in 2014.
Grasshopper, the company's first VTVL test vehicle, consisted of a Falcon 9 v1.0 first-stage tank, a single Merlin-1D engine, and four permanently attached steel landing legs. It stood 106 feet (32 m) tall. SpaceX built a 0.5-acre (0.20 ha) concrete launch facility at its Rocket Development and Test Facility in McGregor, Texas to support the Grasshopper flight test program. Grasshopper was also known as Grasshopper version 1.0, or Grasshopper v1.0, prior to 2014 during the time the followon Grasshopper-class test vehicles were being built.
In addition to three test flights in 2012, five additional tests were successfully flown by the end of October 2013—including the fourth test overall in March 2013—in which Grasshopper doubled its highest leap to rise to 80.1 meters (263 ft) with a 34-second flight. In the seventh test, in August 2013, the vehicle flew to 250 meters (820 ft) during a 60-second flight and executed a 100-meter (330 ft) lateral maneuver before returning to the pad. Grasshopper made its eighth and final test flight on October 7, 2013, flying to 744 meters (2,441 ft) (0.46 miles) before making its eighth successful landing. The Grasshopper test vehicle is now retired.
Falcon 9 Reusable Development Vehicle
As early as October 2012, SpaceX discussed development of a second-generation Grasshopper test vehicle, which was to have lighter landing legs that fold up on the side of the rocket, a different engine bay, and would be nearly 50% longer than the first Grasshopper vehicle. In March 2013, SpaceX announced that the larger Grasshopper-class suborbital flight vehicle would be constructed out of the Falcon 9 v1.1 first-stage tank that was used for qualification testing at the SpaceX Rocket Development and Test Facility in early 2013. It was rebuilt as the F9R Dev1 with extensible landing legs.
The second VTVL flight test vehicle—F9R Dev1, built on the much longer Falcon 9 v1.1 first-stage tank, with retractable landing legs—made its first test flight on April 17, 2014. F9R Dev1 was used for low-altitude test flights in the McGregor, Texas area—projected maximum altitude below 3,000 meters (10,000 ft)—with a total of five test flights, all made during 2014. This vehicle self-destructed as a safety measure during its fifth test flight on August 22, 2014.
By April 2014, a third flight test vehicle—F9R Dev2—was being built and was planned to be flown at the high-altitude test range available at Spaceport America in New Mexico where it was expected to be flown at altitudes up to 91,000 meters (300,000 ft)-plus. It was never flown as SpaceX moved the high-altitude testing program to its controlled-descent testing of used boosters following their use on a paid orbital launch and ascent.
DragonFly is a prototype test article for a propulsively landed version of the SpaceX Dragon capsule, a suborbital reusable launch vehicle (RLV), intended for low-altitude flight testing. It will undergo a test program in Texas at the McGregor Rocket Test Facility, in 2014–2015.
The DragonFly test vehicle is powered by eight SuperDraco engines, arranged in a redundant pattern to support fault-tolerance in the propulsion system design. SuperDracos utilize a storable propellant mixture of monomethyl hydrazine (MMH) fuel and nitrogen tetroxide oxidizer (NTO), the same propellants used in the much smaller Draco thrusters used for attitude control and maneuvering on the first-generation Dragon spacecraft. While SuperDraco engines are capable of 73,000 newtons (16,400 lbf) of thrust, during use on DragonFly flight test vehicle each will be throttled to less than 68,170 newtons (15,325 lbf) to maintain vehicle stability.
A test flight program of thirty flights has been proposed, including two propulsive assist (parachutes plus thrusters) and two propulsive landing (no parachutes) on flights dropped from a helicopter at an altitude of approximately 3,000 meters (10,000 ft). The other 26 test flights are projected to take off from a pad: eight to be propulsive assist hops (landing with parachutes plus thrusters) and 18 to be full propulsive hops, similar to the Grasshopper and F9R Dev booster stage test flights.
Falcon 9 booster post-mission flight tests
In an arrangement unusual for launch vehicles, some first stages of the SpaceX Falcon 9 v1.1 rockets are being used for propulsive-return controlled-descent flight tests after they complete the boost phase of an orbital flight. These boosters would ordinarily just be discarded in the ocean after setting their payloads on their way. The over-water tests take place in the Pacific and Atlantic oceans south of Vandenberg Air Force Base and east of Cape Canaveral Air Force Station. The first flight test occurred on September 29, 2013, after the second stage with the CASSIOPE and nanosat payloads separated from the booster. These descent and simulated landing tests continued over the next two years, with the second flight test taking place on April 18, 2014, and four subsequent tests conducted in 2015.
Re-entry and controlled descent development
Following analysis of the flight test data from the first booster-controlled descent in September 2013, SpaceX announced it had successfully tested a large amount of new technology on the flight, and that coupled with the technology advancements made on the Grasshopper low-altitude landing demonstrator, they were ready to test a full recovery of the booster stage. The first flight test was successful; SpaceX said it was "able to successfully transition from vacuum through hypersonic, through supersonic, through transonic, and light the engines all the way and control the stage all the way through [the atmosphere]". Musk said, "the next attempt to recovery [sic] the Falcon 9 first stage will be on the fourth flight of the upgraded rocket. This would be [the] third commercial Dragon cargo flight to ISS."
This second flight test took place during the April 2014 Dragon flight to the ISS. SpaceX attached landing legs to the first stage, decelerated it over the ocean and attempted a simulated landing over the water, following the ignition of the second stage on the third cargo resupply mission contracted to NASA. The first stage was successfully slowed down enough for a soft landing over the Atlantic Ocean. SpaceX announced in February 2014 the intent to continue the tests to land the first-stage booster in the ocean until precision control from hypersonic all the way through subsonic regimes has been proven. Five additional controlled-descent tests were conducted in the remainder of 2014 through April 2015, including two attempts to land on a floating landing platform—a SpaceX-built Autonomous Spaceport Drone Ship—on the Atlantic Ocean east of the launch site, both of which brought the vehicle to the landing platform, but neither of which resulted in a successful landing.
First landing on ground pad
During the 2015 launch hiatus, SpaceX requested regulatory approval from the FAA to attempt returning their next flight to Cape Canaveral instead of targeting a floating platform in the ocean. The goal was to land the booster vertically at the leased Landing Zone 1 facility—the former Launch Complex 13 where SpaceX had recently built a large rocket landing pad. The FAA approved the safety plan for the ground landing on December 18, 2015. The first stage landed successfully on target at 20:38 local time on December 21 (01:38 UTC on December 22).
SpaceX does not plan to fly the Falcon 9 Flight 20 first stage again. Rather, the rocket was moved a few miles north to the SpaceX hangar facilities at Launch pad 39A, recently refurbished by SpaceX at the adjacent Kennedy Space Center, where it was inspected before being used on January 15, 2016, to conduct a static fire test on its original launchpad, Launch Complex 40. 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 tests delivered 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.
Near-misses on the oceans
Falcon 9 Flight 21 launched the Jason-3 satellite on January 17, 2016, and attempted to land on the floating platform Just Read the Instructions, located for the first time about 200 miles (320 km) out in the Pacific Ocean. Approximately 9 minutes into the flight, the live video feed from the drone ship went down due to the losing its lock on the uplink satellite. The vehicle landed smoothly onto the vessel but one of the four landing legs failed to lock properly, reportedly due to ice from the heavy pre-launch fog preventing a lockout collet from latching. Consequently the booster fell over shortly after touchdown and was destroyed in a deflagration upon impact with the pad.
Flight 22 was carrying a heavy payload of 5,271 kilograms (12,000 lb) to geostationary transfer orbit (GTO). This was heavier than previously advertised maximum lift capacity to GTO being made possible by going slightly subsynchronous. Following delays caused by failure of Flight 19 SpaceX agreed to provide extra thrust to the SES-9 satellite to take it supersynchronous. As a result of these factors, there was little propellant left to execute a full reentry and landing test with normal margins. Consequently the Falcon 9 first stage followed a ballistic trajectory after separation and re-entered the atmosphere at high velocity, making it less likely to land successfully. The atmospheric re-entry and controlled descent were successful despite the higher aerodynamical constraints on the first stage due to extra speed. However the rocket was moving too fast and was destroyed when it collided with the drone ship. SpaceX collected valuable data on the extended flight envelope required to recover boosters from GTO missions.
Landings at sea
Starting in January 2015, SpaceX positioned stable floating platforms a few hundred miles off the coast along the rocket trajectory; those transformed barges were called autonomous spaceport drone ships. On April 8, 2016, Falcon 9 Flight 23, the third flight of the full-thrust version, delivered the SpaceX CRS-8 cargo on its way to the International Space Station while the first stage conducted a boostback and re-entry maneuver over the Atlantic ocean. Nine minutes after liftoff, the booster landed vertically on the drone ship Of Course I Still Love You, 300 km from the Florida coastline, achieving a long-sought-after milestone for the SpaceX reusability development program.
A second successful drone ship landing occurred on May 6, 2016, with the next flight which launched JCSAT-14 to GTO. This second landing at sea was more difficult than the previous one because the booster at separation was traveling about 8,350 km/h (5,190 mph) compared to 6,650 km/h (4,130 mph) on the CRS-8 launch to low Earth orbit. 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. Elon Musk indicated this first stage may not be flown again instead being used as a life leader for ground tests to confirm others are good.
A third successful landing followed on 27 May, again following deceleration from the high speed required for a GTO launch. The landing crushed a "crush core" in one leg, leading to a notable tilt to the stage as it stood on the drone ship.
Over the subsequent missions, landing of the first stage gradually became a routine procedure, and since January 2017 SpaceX ceased to refer to their landing attempts as "experimental". Low-energy missions to the ISS fly back to the launch site and land at LZ-1, whereas more demanding satellite missions land on drone ships a few hundred miles downrange. Occasional missions with heavy payloads, such as EchoStar 23, do not attempt to land, flying in expendable configuration without fins and legs.
Further successful landings occurred:
- on the LZ-1 ground pad: CRS-9 on 18 July 2016, CRS-10 on 19 February 2017, NROL-76 on 1 May, CRS-11 on 3 June, CRS-12 on 14 August, Boeing X-37B OTV-5 on 7 September, CRS-13 on 15 December, and Zuma on 8 January 2018.
- on drone ships: JCSAT-16 on 14 August 2016, Iridium NEXT-1 on 14 January 2017, SES-10 on 30 March and BulgariaSat-1 on 23 June (first and second recoveries of re-flown boosters), Iridium NEXT-2 on 25 June, Formosat-5 on 24 August, Iridium NEXT-3 on 9 October, SES-11/EchoStar 105 on 11 October, and Koreasat 5A on 30 October 2017.
During 2016 and 2017, SpaceX has recovered a number of first stages to both land and drone ships, helping them optimize the procedures needed to re-use the boosters rapidly. In January 2016 Elon Musk estimated the likelihood of success at 70 percent for all landing attempts in 2016, hopefully rising to 90 percent in 2017; he also cautioned that we should expect "a few more RUDs" (Rapid Unscheduled Disassembly, Musk's euphemism to denote destruction of the vehicle on impact). Musk's prediction was vindicated, as 5 out of 8 flown boosters ( 63%) were recovered in 2016, and 14 out of 14 ( 100%) in 2017. Three GTO missions for heavy payloads (EchoStar 23 in March 2017, Inmarsat-5 F4 in May 2017 and Intelsat 35e in July 2017) were flown in an expendable configuration, not equipped for landing. One booster which could have been recovered was intentionally flown without legs and left to sink after a soft touchdown in the ocean (booster B1036 for the Iridium NEXT 31–40 mission in December 2017).
Since late 2017, incremental testing with refinements to the fairing recovery design have been conducted. SpaceX has indicated that they expected to recover an intact fairing in 2017, and to fly a recovered fairing in 2018. As of December 2017[update], no official information on progress in the fairing recovery process was available.
As of 6 February 2018[update], SpaceX had recovered 17 first-stage boosters from previous missions, of which six were recovered twice, yielding a total 23 landings. In 2017, SpaceX flew a total of 5 missions out of 20 with re-used boosters ( 25%). In total, eight boosters have been re-flown as of February 2018[update].
On July 28, 2016, the first stage from the JCSAT-2B mission was successfully test-fired for a full duration at the SpaceX McGregor facility. The first reuse attempt occurred on 30 March 2017 with the launch of SES-10, resulting in a successful flight and second landing of the B1021 first stage recovered from the CRS-8 mission of April 2016. Another reflight succeeded in June 2017 with BulgariaSat-1 riding the B1029 booster from the January 2017 Iridium NEXT mission. Booster B1031 flew the CRS-10 mission to the ISS in February 2017 and helped loft communications satellite SES-11 to geostationary orbit in October 2017. Boosters B1035 and B1036 were flown twice each for the same customer, B1035 for NASA missions CRS-11 and CRS-13 in June and December 2017, and B1036 for two batches of 10 Iridium NEXT satellites, also in June and December 2017. B1032 was re-used for GovSat-1 in January 2018 after NROL-76 in May 2017. Finally, B1023 and B1025 were re-used as side boosters on the Falcon Heavy test flight in February 2018.
SpaceX spent four months refurbishing the first booster to be re-used, B1021, and launched it again after approximately one year. The second booster to be flown again, B1029, was refurbished in "only a couple of months" and re-launched after five months. Elon Musk has stated a goal to turn around a first stage within 24 hours before the end of 2017, but that did not happen.
Boosters B1019 and B1021 were retired and put on display. B1029 was also retired after the BulgariaSat-1 mission.[better source needed] B1023, B1025, B1031 and B1035 were recovered a second time, while B1032 and B1036 were deliberately sunk at sea after a soft ocean touchdown.
As early as mid-2015, Musk hinted that SpaceX might be working on fairing reusability, following the discovery of wreckage of an unidentified Falcon 9 launch vehicle section off the coast of The Bahamas, and was subsequently confirmed by SpaceX to be a component of a payload fairing that had washed ashore. By April 2016, they had publicly announced Falcon 9 fairing recovery as an objective.
In March 2017, as part of the SES-10 mission, SpaceX for the first time performed a controlled landing of the payload fairing and successfully recovered a fairing half, aided by attitude-control thrusters and a steerable parachute, helping it glide towards a gentle touchdown on water. The company announced intent to land the fairings eventually on a dry flexible structure, jokingly described by Musk as a "floating bouncy-castle", with the aim of full fairing reuse. With successive tests and refinements on several flights, intact fairing recovery was stated as an objective for 2017, with reflight of a recovered fairing planned in 2018.
In the event, the "bouncy castle" idea was superseded by a net strung between large arms, and SpaceX was still working to perfect the fairing landing and recovery approach in February 2018. The net, installed on Mr. Steven (a fast platform supply vessel equipped with dynamic positioning systems), was tested on the launch of the Paz satellite from Vandenberg Air Force Base Space Launch Complex 4E in that month. This mission was also the first to use a version 2 fairing, explicitly designed to "improve survivability for post-launch recovery attempts, and to be reusable on future missions".. This recovery attempt was not fully successful; the fairing missed the boat by a few hundred meters but landed intact in the water before being recovered and taken back to port.
Despite early public statements that SpaceX would endeavor to make the Falcon 9 second-stage reusable as well, by late 2014, they determined that the mass needed for a re-entry heat shield, landing engines, and other equipment to support recovery of the second stage as well as the diversion of development resources from other company objectives was at that time prohibitive, and indefinitely suspended their second-stage reusability plans for the Falcon rockets. However, in July 2017 they indicated that they might do experimental tests on recovering one or more second-stages in order to learn more about reusability to inform their new, much-larger, BFR launch vehicle development process.
Both stages of the BFR—planned to replace all existing SpaceX launch and space vehicles after the mid-2020s: Falcon 9, Falcon Heavy and the Dragon spacecraft, and initially aiming at the Earth-orbit launch market, but explicitly adding substantial capability to support long-duration spaceflight in the cislunar and Mars mission environments.—is being designed to be reusable. The second stage on this new generation of launch vehicle is fully reusable, and is an integrated second-stage-with-spaceship design that has not been commonly used in previous launch vehicles.
In the first year of successful stage return from the experimental test flights, SpaceX performed ad hoc and flight-specific evaluation and component testing on each successfully landed stage. Stages were processed and initially evaluated in either launch hangars, or for Cape Canaveral landings, in the new hangar SpaceX recently completed at Kennedy Space Center Launch Complex 39. Returned rocket parts have also been transported to SpaceX Hawthorne and SpaceX McGregor for engineering evaluation and testing.
In February 2017, after eight rocket cores had successfully landed — seven of them having launched from Cape Canaveral — SpaceX announced plans to expand their physical facilities to process and refurbish rockets. They will do so in both leased space and in a new building to be built in Port Canaveral, Florida, near the location where the Atlantic Autonomous Spaceport Drone Ship is berthed, and where stages that land on the east-coast droneship are now removed from the ship.
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SpaceX exists to further [the vision of humans becoming multi-planetary] on several fronts: to develop the reusable rocket technology that would be needed to ferry large numbers of people, and large amounts of cargo, to Mars; ...
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I think we are quite close to being able to recover the fairing. ... about a 5 or 6 million dollar piece of equipment. We've got a decent shot of recovering a fairing by the end of the year, and reflight by late this year or early next. ... Upper stage is about 20 percent of the cost of the mission. So if you get boost stage and fairing we're around 80 percent reusable. ... Think for a lot of missions, we could even bring the second stage back. So were going to try to do that, but our primary focus [for the next couple of years will be crew Dragon].
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'The earliest Falcon 9 launches carried parachutes which were to have been used to recover the first stage. However, this was abandoned due to the stage disintegrating during reentry, before the parachutes could be deployed. Instead, SpaceX began to investigate using the stage’s engines to make a powered descent and landing. Alongside this, an improved Falcon 9 vehicle, the Falcon 9 v1.1, was developed.'
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(@18:15 It is a very tough engineering problem—and it wasn't something that I thought, wasn't sure it could be solved for a while. But then, just relatively recently, in the last 12 months or so, I've come to the conclusion that it can be solved. And SpaceX is going to try to do it. Now, we could fail. I am not saying we are certain of success here, but we are going to try to do it. And we have a design that, on paper, doing the calculations, doing the simulations, it does work. Now we need to make sure that those simulations and reality agree, because generally when they don't, reality wins. So that's to be determined.)
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much bigger [than Falcon 9], but I don’t think we’re quite ready to state the payload. We’ll speak about that next year.
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Q. What is strategy on booster recover? Musk: Initial recovery test will be a water landing. First stage continue in ballistic arc and execute a velocity reduction burn before it enters atmosphere to lessen impact. Right before splashdown, will light up the engine again. Emphasizes that we don’t expect success in the first several attempts. Hopefully next year with more experience and data, we should be able to return the first stage to the launch site and do a propulsion landing on land using legs. Q. Is there a flight identified for return to launch site of the booster? Musk: No. Will probably be the middle of next year.
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The April 17 F9R Dev 1 flight, which lasted under 1 min., was the first vertical landing test of a production-representative recoverable Falcon 9 v1.1 first stage, while the April 18 cargo flight to the ISS was the first opportunity for SpaceX to evaluate the design of foldable landing legs and upgraded thrusters that control the stage during its initial descent.
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hopeful that sometime in the next couple of years we'll be able to achieve full and rapid reusability of the first stage—which is about three-quarters of the cost of the rocket—and then with a future design architecture, achieve full reusability.
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This technology element [reusable launch vehicle technology] all this innovation is being done by SpaceX alone, no one is paying us to do it. The government is very interested in the data we are collecting on this test series. ... This is the kind of thing that entrepreneurial investment and new entrants/innovators can do for an industry: fund their own improvements, both in the quality of their programs and the quality of their hardware, and the speed and cadence of their operations.
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SpaceX is using private capital to develop and demonstrate the Falcon 9 rocket's reusability. SpaceX has not disclosed how much the reusable rocket program will cost
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Musk said SpaceX made the Falcon 9 rocket’s first stage reusable with entirely private funding, investing at least $1 billion in the effort [...]
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So it is a bit tricky. Because we have to figure out how to improve the cost of the trips to Mars by five million percent ... translates to an improvement of approximately 4 1/2 orders of magnitude. These are the key elements that are needed in order to achieve a 4 1/2 order of magnitude improvement. Most of the improvement would come from full reusability—somewhere between 2 and 2 1/2 orders of magnitude—and then the other 2 orders of magnitude would come from refilling in orbit, propellant production on Mars, and choosing the right propellant.
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The Dragon capsule has a shape that is stable on reentry from orbit, whereas rocket states traditionally are not stable on reentry, so there is a lot of software involved, a lot of guidance navigation and control involved, and a lot of thermal protection required; so we have to make advances in all those areas. We also have to restart the engines supersonically.
- Gwynne Shotwell (June 17, 2013). Singapore Satellite Industry Forum 2013 - Opening Keynote. Retrieved April 9, 2016.
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A key upgrade to enable precision targeting of the Falcon 9 all the way to touchdown is the addition of four hypersonic grid fins placed in an X-wing configuration around the vehicle, stowed on ascent and deployed on reentry to control the stage’s lift vector. Each fin moves independently for roll, pitch and yaw, and combined with the engine gimbaling, will allow for precision landing – first on the autonomous spaceport drone ship, and eventually on land.
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The Falcon 9 first stage carries landing legs which will deploy after stage separation and allow for the rocket’s soft return to Earth. The four legs are made of state-of-the-art carbon fiber with aluminum honeycomb. Placed symmetrically around the base of the rocket, they stow along the side of the vehicle during liftoff and later extend outward and down for landing.
- "Falcon Heavy Landing Legs". SpaceX.com. April 12, 2013. Retrieved December 4, 2013.
The Falcon Heavy first stage center core and boosters each carry landing legs, which will land each core safely on Earth after takeoff. After the side boosters separate, the center engine in each will burn to control the booster’s trajectory safely away from the rocket. The legs will then deploy as the boosters turn back to Earth, landing each softly on the ground. The center core will continue to fire until stage separation, after which its legs will deploy and land it back on Earth as well. The landing legs are made of state-of-the-art carbon fiber with aluminum honeycomb. The four legs stow along the sides of each core during liftoff and later extend outward and down for landing.
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F9R (pronounced F-niner) shows a little leg. Design is a nested, telescoping piston w A frame... High pressure helium. Needs to be ultra light.
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The crush core in the Falcon legs is reusable after soft landings, but needs to be replaced after hard.
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The first successful "soft landing" of a Falcon 9 rocket happened in April of this year
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[Falcon 9 v1.1] vehicle has thirty percent more performance than what we put on the web and that extra performance is reserved for us to do our reusability and recoverability [tests] ... current vehicle is sized for reuse.
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SpaceX's work with the F9R is part of an effort to develop fully and rapidly reusable launch systems, a key priority for the company. Such technology could slash the cost of spaceflight by a factor of 100.
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Expendable rockets, which many smart people have worked on in the past, get maybe 2% of liftoff mass to orbit -- really not a lot. Then, when they’ve tried reusability, it’s resulted in negative payload, a 0 to 2% minus payload [laughs]. The trick is to figure out how to create a rocket that, if it were expendable, is so efficient in all of its systems that it would put 3% to 4% of its mass into orbit. On the other side, you have to be equally clever with the reusability elements such that the reusability penalty is no more than 2%, which would leave you with a net ideally of still 2% of usable load to orbit in a reusable scenario, if that makes sense. You have to pry those two things apart: Push up payload to orbit, push down the mass penalty for reusability -- and have enough left over to still do useful work.
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At this point, we are highly confident of being able to land successfully on a floating launch pad or back at the launch site and refly the rocket with no required refurbishment
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SpaceX has constructed a half-acre concrete launch facility in McGregor, and the Grasshopper rocket is already standing on the pad, outfitted with four insect-like silver landing legs.
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SES’s contract with SpaceX called for the rocket to deploy SES 9 into a “sub-synchronous” transfer orbit with an apogee around 16,155 miles (26,000 kilometers) in altitude. Such an orbit would require SES 9 to consume its own fuel to reach a circular 22,300-mile-high perch, a trek that Halliwell said was supposed to last 93 days. The change [SpaceX offered] in the Falcon 9’s launch profile will put SES 9 into an initial orbit with an apogee approximately 24,419 miles (39,300 kilometers) above Earth, a low point 180 miles (290 kilometers) up, and a track tilted about 28 degrees to the equator
- "SES-9 Mission" (PDF). Press Kit. SpaceX. February 23, 2016. Retrieved February 24, 2016.
This mission is going to a Geostationary Transfer Orbit. Following stage separation, the first stage of the Falcon 9 will attempt an experimental landing on the “Of Course I Still Love You” droneship. Given this mission’s unique GTO profile, a successful landing is not expected.
- Drake, Nadia (April 8, 2016). "SpaceX Rocket Makes Spectacular Landing on Drone Ship". National Geographic. Retrieved April 8, 2016.
To space and back, in less than nine minutes? Hello, future.
- You tube JCSat 14 hosted webcast
- You tube CRS8 hosted webcast
- Elon Musk [@elonmusk] (May 6, 2016). "Yeah, this was a three engine landing burn, so triple deceleration of last flight. That's important to minimize gravity losses" (Tweet). Retrieved May 8, 2016 – via Twitter.
- Florida Today Landed spacex rocket suffered max damage
- Elon Musk [@elonmusk] (January 19, 2016). "My best guess for 2016: ~70% landing success rate (so still a few more RUDs to go), then hopefully improving to ~90% in 2017" (Tweet) – via Twitter.
- Landed Falcon 9 First Stage Test Firing. SpaceX. July 28, 2016.
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- Musk, Elon (2018). "Missed by a few hundred meters, but fairing landed intact in water. Should be able catch it with slightly bigger chutes to slow down descent". Twitter. Retrieved 22 February 2018.
- Ananian, C. Scott (October 24, 2014). Elon Musk MIT Interview. Event occurs at 14:20. Retrieved July 16, 2017 – via YouTube.
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Shotwell said SpaceX plans to attempt second stage recoveries from the existing Falcon family is less to reuse them, and more to learn about reusability in preparation for the BFR’s second stage
- Elon Musk (29 September 2017). Becoming a Multiplanet Species (video). 68th annual meeting of the International Astronautical Congress in Adelaide, Australia: SpaceX. Retrieved 8 March 2018 – via YouTube.
- "SpaceX to lease building at Port Canaveral, build another one". Florida Today. August 24, 2016. Retrieved August 24, 2016.
|Wikimedia Commons has media related to Grasshopper (rocket).|
- Video of 8th and final low-altitude Grasshopper v1.0 test flight, to 744 meters (0.462 miles), October 7, 2013.
- Low-resolution photograph of the Falcon 9 booster controlled-descent test on September 29, 2013, just moments before impacting the Atlantic ocean.
- Video of Falcon 9 Reusable Development vehicle no. 1 (F9R Dev1) 1st test flight, to 250 meters (0.16 miles), hovering and then landing just next to the launch stand, April 17, 2014.
- Video of CRS-3 booster stage landing test, April 2014: low quality, corrupted data and higher quality, after video frames recovered by open-source recovery effort by NSF team.
- On-board camera video of ORBCOMM Mission-1 booster stage landing test: Falcon 9 First Stage Return : ORBCOMM Mission, SpaceX-released video of the controlled descent test, July 2014.
- Chase-plane camera video of ORBCOMM Mission-1 booster stage landing test: Falcon 9 First Stage Reentry Footage from Plane , SpaceX-released video of the controlled descent test, released August 14, 2014.
- SpaceX rocket nails launch but narrowly misses landing test, Reuters, Irene Klotz, January 10, 2015.