SpaceX reusable launch system development program

SpaceX reusable launch system development program

Falcon 9 Flight 20's first stage successfully landing on dry land in December 2015
Commercial? Yes
Type of project Privately funded
Location Various
Owner SpaceX
Founder Elon Musk
Established Publicly announced 2011
Current status Active

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 long term goal is that both stages of their orbital launch vehicle will be designed to allow reuse a few hours after return.[1]

The program was publicly announced in 2011 and the design for returning the rocket to its launchpad using only its own propulsion systems was completed in February 2012.[1] SpaceX's active test program began in late 2012 with testing low-altitude, low-speed aspects of the landing technology. High-velocity, high-altitude aspects of the booster atmospheric return technology began testing in late 2013 and continued to late 2015, when SpaceX first achieved a successful landing and recovery of a first stage.

The reusable launch system technology is under development for the first stages of the Falcon family of rockets.[2] 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. If the technology is used on a reusable Falcon 9 rocket, the first-stage separation would occur at a velocity of approximately 2.0 km/s (6,500 km/h; 4,100 mph; Mach 6) rather than the 3.4 km/s (11,000 km/h; 7,000 mph; Mach 10) for an expendable Falcon 9, to provide the residual fuel necessary for the deceleration and turnaround maneuver and the controlled descent and landing.[1] The reusable technology will also be extended to both the first and upper stages of the future launch vehicle for the Mars Colonial Transporter[2][3][3] and is considered paramount to the plans SpaceX is developing to colonize Mars.[4]

The first successful controlled landing of an orbital rocket stage on the ocean surface was achieved in April 2014. Two subsequent controlled-descent tests also attempted to land the returning first stage on a floating landing platform—one each in January and April 2015. But although the booster was guided to the floating platform in both cases, neither test was successful in achieving a vertical landing on the platform.[5][6] A historic vertical landing was finally achieved on December 21, 2015, when the first-stage booster of Falcon 9 Flight 20 successfully landed at Landing Zone 1, Cape Canaveral.[7]

History

From left to right, Falcon 1, Falcon 9 v1.0, three versions of Falcon 9 v1.1, and two versions of Falcon Heavy. The SpaceX reusable rocket technology is being developed for both Falcon 9 v1.1 and Falcon Heavy.

The broad outline of the reusable launch system was first publicly described on September 29, 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.[8][9][10][11] In September 2012, SpaceX began flight tests on a prototype reusable first stage with the suborbital Grasshopper rocket.[12] Those tests continued into 2014, including testing of a second and larger prototype vehicle, F9R Dev1.

News of the Grasshopper test rocket become public earlier in September 2011, 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 by September 26.[13][14] 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.[15]

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 will be "an evolution of SpaceX's Falcon 9 booster", and SpaceX reiterated their commitment to develop a breakthrough in vertical landing technology.[16] 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.[12] In early March 2013, SpaceX successfully tested Grasshopper for a fourth time when it flew to an altitude of over 80 meters (260 ft).[17]

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.[18] The April 2013 draft Environmental Impact Statement for the proposed SpaceX private launch site in south Texas includes specific accommodations for return of the Falcon 9 first-stage boosters to the launch site.[19] Elon Musk first publicly referred to the reusable Falcon 9 as the Falcon 9-R in April 2013.[20]

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.[21] 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.[22] 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, with the intention of doing so on the next Space Station cargo resupply flight pending regulatory approvals.[23][24] That flight took place on April 18, 2014.[25][26]

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".[27]

In February 2014, SpaceX made explicit that the newly defined super-heavy launch vehicle for the Mars Colonial Transporter would also make use of the reusable technology.[3] This is 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."[28]

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 will be run in Texas at the McGregor Rocket Test Facility in 2014–2015.[29]

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.[30] SpaceX has not publicly disclosed the cost of the development program.[31]

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."[32]

By late 2014, SpaceX suspended or abandoned the plan to recover and reuse the Falcon 9 second stage;[33] the additional mass of the required heat shield, landing gear, and low-powered landing engines would incur too great a performance penalty.

Technologies

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."[32]

Falcon 9 booster stage re-entry with grid fins, February 2015 following the launch of the DSCOVR mission

The technologies that were developed for this program, some of which are still being refined, include:

Falcon 9 v1.1 with landing legs attached, in stowed position as the rocket is prepared for launch in its hangar
Autonomous Spaceport Drone Ship, in port in January 2015.

Economic issues

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.[23] 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.[23] In December 2015, following the recovery of the first stage from the 22 December launch, SpaceX projected that the first reflight of a recovered booster would likely occur in 2016, but that their plan was to not refly the 22 December recovered stage for that purpose.[49] Musk projects that the reflight step of the program will be "straightforward," because of the multiple full duration firings of the engines that have been done on the ground, and the multiple engine restarts that have already been demonstrated, with no significant degradation seen.[50] Several industry analysts continue to see potential problems that could prevent economic reuse because costs to refurbish and relaunch the stage are not yet demonstrated. Moreover, the economic case for reuse will be highly dependent on launching frequently, and that is simply unknown as of 2015.[51]

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.[23][52] 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."[21] 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.[53][54]

Depiction of Falcon 9 landing trajectory for some of the floating-platform recovery tests

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."[55] 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,[56] 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."[51]

As of March 2014 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 are 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.[44]

SpaceX pricing and payload specifications published for the non-reusable Falcon 9 v1.1 rocket actually include about 30 percent more performance than the published price list indicates; the additional performance is reserved for SpaceX to do reusability booster demonstration flight tests while still achieving the specified payloads for customers.[57]

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"[58] is dependent on achieving both complete and rapid reusability.[25][53] CEO Musk stated in 2014 that success with the technology development effort could reduce "the cost of spaceflight by a factor of 100"[59] because the cost of the propellant/oxidizer on the Falcon 9 is only 0.3 percent of the total cost of the vehicle.[60]

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 has said 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."[61]

Technical feasibility

Prior to the reusability program's success in December 2015, the return of an orbital launch system had never been accomplished. And even after this success, the rapid reuse of a rocket is still yet to be attempted. Developing a reusable rocket is extremely challenging due to the small percentage of a rocket's mass that can make it to orbit.[9][62] 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.[63]

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.[22]

Test program

SpaceX is currently testing reusable technologies both for its first-stage booster launch vehicle designs—with three test vehicles—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:

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,[23][26][67] a third test flight in July[68] and a fourth test in September 2014. All four test flights to date were intended to be over-water, simulated landings.[32] 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.[69][70]

Prototype vehicle flight testing

Main article: Grasshopper (rocket)
Grasshopper rocket performing a 325 meter flight followed by a soft propulsive landing in an attempt to develop technologies for a reusable launch vehicle.

Grasshopper is a set of experimental technology-demonstrator, suborbital reusable launch vehicles (RLV). Two versions of the prototype reusable test vehicles was 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.[58] Grasshopper was built in 2011-2012 for low-altitude, low-velocity hover testing at the SpaceX Rocket Test Facility in McGregor, Texas, 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 for higher-altitude and higher-velocity flight testing.[58][71][72]

The low-altitude, low-speed flights of the first test vehicle—Grasshopper—were conducted .[13][14] F9R Dev1 was also tested at the Texas facility.

Grasshopper

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.[14] 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.[73] 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.[74] 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.[75] 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.[76] The Grasshopper test vehicle is now retired.[77]

Falcon 9 Reusable Development Vehicle (F9R Dev)

Beginning in October 2012, SpaceX discussed development of a second-generation Grasshopper test vehicle, which would 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.[72] 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 has been 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, and with retractable landing legs—made its first test flight on April 17, 2014.[58][69] F9R Dev1 was used for low-altitude test flights in the McGregor, Texas area with projected maximum altitude below 3,000 meters (10,000 ft).[58] This vehicle self-destructed as a safety measure during a test flight on August 22, 2014.[78]

As of 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.[58]

DragonFly

Main article: DragonFly (rocket)

DragonFly is a prototype test article for a propulsively-landed version of the SpaceX Dragon space 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.[29][79]

The DragonFly test vehicle is powered by eight SuperDraco engines, arranged in a redundant pattern to support fault-tolerance in the propulsion system design.[80] 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.[79] 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.[79]

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.[79][80]

The DragonFly test program is not expected to start until after the completion of the F9R Dev1 booster testing at the McGregor facility.[80]

Falcon 9 booster post-mission, controlled-descent tests

CRS-6 booster landing attempt

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 once boost phase is complete. The over-water tests occurred 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 into 2014 and 2015, with the second flight test having occurred on April 18, 2014,[23][26][67] and the fifth, sixth, seventh and eighth tests occurring in 2015.[81]

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]".[22] 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."[24]

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.[26] 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.[67] 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 dry-land landing test

Falcon 9 Flight 20's first stage landing viewed from a helicopter, 22 December 2015.

SpaceX applied to the FAA for regulatory approval to make the next test, the 8th booster descent test overall, to attempt a landing on land rather than on a floating landing platform in the ocean. The goal was to bring the booster down at the Landing Zone 1 facility—the former CCAFS Launch Complex 13—that SpaceX has recently built at Cape Canaveral Air Force Station.[82] The FAA approved the ground safety plan for the land landing on 18 December 2015. [83] SpaceX successfully accomplished the first stage landing at Landing Zone 1 on 21 December, Florida time (22 December UTC).[84][81]

As of December 2015, SpaceX don't plan to fly the Falcon 9 Flight 20 first stage again. Rather, the rocket was moved to the new SpaceX launch pad several miles to the north leased from the adjacent Kennedy Space Center where, on 15 January 2016, SpaceX conducted a static fire test on the recovered booster to assess capabilities for reflight of the launch vehicle design after future landings..[85][81] They reported that the test was good overall but one of the outer engines, "engine 9", showed thrust fluctuations. Elon Musk reported that this may have been due to debris ingestion.[86]

First stage of Falcon 9 Flight 21 descending over the floating landing platform, 17 January 2016, immediately prior to a soft touchdown followed by deflagration of the rocket after a landing leg failed to latch, causing the rocket to tip over.

Pacific drone-ship landing test

Falcon 9 Flight 21 launched Jason 3 satellite on January 17, 2016 and attempted a landing on their floating landing platform located for the first time in the Pacific. The vehicle made a soft landing onto the drone ship, but one of the four landing legs failed to lock properly—reportedly due to ice from the heavy pre-launch fog causing a lockout collet to fail to latch—leading to the stage falling over after touchdown, resulting in a deflagration of the rocket on impact with the landing pad.[87][88][89]

Future tests

SpaceX aims to return a number of first stages to both land and drone ships in 2016 to clarify the procedures needed to re-use flown boosters. The company hopes to be able to begin offering flown Falcon 9 rocket stages by the end of the year, aiming for a re-flight of a stage in the not too distant future.[90] Musk indicated in January 2016 that he thought the likelihood of successful landings for all of the attempted landings in 2016 would be approximately 70 percent, hopefully rising to 90 percent in 2017, and cautioned that we should expect "a few more RUDs" (Rapid Unscheduled Disassembly).[91]

See also

References

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  33. ↑ https://www.youtube.com/watch?v=y13jbl7ASxY&feature=youtu.be&t=14m20s
  34. 1 2 3 4 Shotwell, Gwynne (January 14, 2014). Shotwell statement on reusable technology development. Parabolic Arc. Event occurs at 16:15–17:05. Retrieved January 15, 2014. [Rocket stages are not passively stable on rentry from orbit], ... 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.
  35. ↑ Gwynne Shotwell (March 21, 2014). Broadcast 2212: Special Edition, interview with Gwynne Shotwell (audio file). The Space Show. Event occurs at 51;50–52;55. 2212. Archived from the original (mp3) on March 22, 2014. Retrieved March 22, 2014.
  36. ↑ "X MARKS THE SPOT: FALCON 9 ATTEMPTS OCEAN PLATFORM LANDING". SpaceX. December 16, 2014. Retrieved December 17, 2014. 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.
  37. ↑ Rosenberg, Zach (March 21, 2013). "SpaceX Merlin 1D qualified for flight". Flightglobal. Retrieved March 18, 2014.
  38. ↑ "SpaceX Falcon 9 v1.1 Data Sheet". Space Launch Report. March 12, 2014. Retrieved March 18, 2014.
  39. ↑ Boyle, Alan (May 2, 2013). "SpaceX's Elon Musk shows off Grasshopper test rocket's latest hop". NBC News. Retrieved March 9, 2013.
  40. ↑ "Woo-hoo! Awesome SpaceX Grasshopper "Hover-Slam" Rocket Launch Doubles Previous Height". Daily Kos. March 9, 2013.
  41. ↑ Grasshopper 325m Test | Single Camera (Hexacopter). YouTube.com (SpaceX). June 14, 2013. Retrieved July 6, 2013.
  42. ↑ Bergin, Chris (November 24, 2014). "SpaceX’s Autonomous Spaceport Drone Ship ready for action". NASASpaceFlight.com. Retrieved November 26, 2014.
  43. ↑ Bergin, Chris (December 17, 2014). "SpaceX confirms CRS-5 launch slip to January 6". NASASpaceFlight.com. Retrieved December 24, 2014.
  44. 1 2 Foust, Jeff (March 24, 2014). "Reusability and other issues facing the launch industry". The Space Review. Retrieved April 1, 2014.
  45. ↑ "Landing Legs". SpaceX.com. July 29, 2013. Retrieved December 4, 2013. 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.
  46. ↑ "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.
  47. ↑ Lindsey, Clark (May 2, 2013). "SpaceX shows a leg for the "F-niner"". NewSpace Watch. Archived from the original on June 30, 2013. Retrieved May 2, 2013. (subscription required (help)). 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.
  48. ↑ Bergin, Chris (February 28, 2014). "SpaceX outlines CRS-3 landing legs plan toward first stage recovery ambitions". NASAspaceflight.com. Retrieved May 10, 2014.
  49. ↑ Jessica Orwig (2015-12-25). "Elon Musk's SpaceX already knows what it's going to do with the history-making rocket — but it's not what you think". Business Insider. Retrieved 2015-12-25.
  50. ↑ "Postlanding teleconference with Elon Musk". 2015-12-22. Retrieved 2015-12-25.
  51. 1 2 Bill Harwood (2015-12-22). "Experts applaud SpaceX rocket landing, potential savings". CBS News. Retrieved 2015-12-25.
  52. ↑ Boozer, R.D. (March 10, 2014). "Rocket reusability: a driver of economic growth". The Space Review. Retrieved March 25, 2014.
  53. 1 2 Belfiore, Michael (April 22, 2014). "SpaceX Brings a Booster Safely Back to Earth". MIT Technology Review. Retrieved April 25, 2014.
  54. ↑ Orwig, Jessica (November 25, 2014). "Elon Musk Just Unveiled A Game-Changing Ocean Landing Pad For His Reusable Rockets". Business Insider. Retrieved December 11, 2014. The first successful "soft landing" of a Falcon 9 rocket happened in April of this year
  55. ↑ Kothari, Ajay P. (April 14, 2014). "Robust and reusable?". The Space Review. Retrieved April 14, 2014.
  56. ↑ Messier, Doug (January 14, 2014). "Shotwell: Reusable Falcon 9 Would Cost $5 to $7 Million Per Launch". Parabolic Arc. Retrieved January 15, 2014.
  57. ↑ Gwynne Shotwell (March 21, 2014). Broadcast 2212: Special Edition, interview with Gwynne Shotwell (audio file). The Space Show. Event occurs at 08:15–11:20. 2212. Archived from the original (mp3) on March 22, 2014. Retrieved March 22, 2014. [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.
  58. 1 2 3 4 5 6 Bergin, Chris (April 22, 2014). "Rockets that return home – SpaceX pushing the boundaries". NASAspaceflight.com. Retrieved April 23, 2014.
  59. ↑ Wall, Mike (September 7, 2014). "Dazzling SpaceX Nighttime Launch Sends AsiaSat 6 Satellite Into Orbit". SPACE.com. Retrieved September 7, 2014. 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.
  60. ↑ http://www.space.com/21386-spacex-reusable-rockets-cost.html
  61. ↑ "SpaceX’s Plan Shows Aggressive Investment In R&D". Aviation Week. April 28, 2014. Retrieved May 17, 2014.
  62. ↑ Clash, Jim (April 2014). "Elon Musk Interview". AskMen. Retrieved September 27, 2014. 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.
  63. ↑ "National Press Club: The Future of Human Spaceflight". September 29, 2011.
  64. ↑ Abbott, Joseph (May 8, 2013). "SpaceX's Grasshopper leaping to NM spaceport". Waco Tribune. Retrieved October 25, 2013.
  65. ↑ Foust, Jeff (May 5, 2014). "Following up: reusability, B612, satellite servicing". The Space Review. Retrieved May 6, 2014.
  66. ↑ Wang, Brian (March 23, 2013). "Spacex May try to "land / recover" the first stage of it next Falcon 9 v1.1 launch this summer". Next Big Future. Retrieved April 6, 2013.
  67. 1 2 3 Klotz, Irene (February 24, 2014). "SpaceX Falcon Rocket to Test Landing Legs". Discovery News. Retrieved February 25, 2014.
  68. ↑ Bergin, Chris (July 28, 2014). "SpaceX Roadmap building on its rocket business revolution". NASAspaceflight. Retrieved July 28, 2014. 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
  69. 1 2 Abbott, Joseph (April 17, 2014). "Grasshopper's successor flies at SpaceX's McGregor site". Waco Tribune. Retrieved April 18, 2014.
  70. ↑ Foust, Jeff (August 23, 2014). "Falcon 9 test vehicle destroyed in accident". NewSpace Journal. Retrieved August 23, 2014.
  71. ↑ Klotz, Irene (September 27, 2011). "A rocket that lifts off—and lands—on launch pad". NBC News. Retrieved November 23, 2011.
  72. 1 2 Lindsey, Clark (October 2, 2012). "A 2nd-gen Grasshopper + A new video of first hop". NewSpace Watch. Archived from the original on January 4, 2013. Retrieved November 4, 2012. (subscription required (help)).
  73. ↑ Clark, Stephen (July 9, 2012). "Reusable rocket prototype almost ready for first liftoff". Spaceflight Now. Retrieved July 13, 2012. 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.
  74. ↑ "Grasshopper Completes Highest Leap to Date". SpaceX.com. March 10, 2013. Retrieved April 21, 2013.
  75. ↑ Boyle, Alan (August 14, 2013). "SpaceX's Grasshopper test rocket flies sideways successfully". NBC News. Retrieved August 15, 2013.
  76. ↑ "Grasshopper flies to its highest height to date". Facebook.com. SpaceX. October 12, 2013. Retrieved October 14, 2013. WATCH: Grasshopper flies to its highest height to date - 744 m (2441 ft) into the Texas sky. http://youtu.be/9ZDkItO-0a4 This was the last scheduled test for the Grasshopper rig; next up will be low altitude tests of the Falcon 9 Reusable (F9R) development vehicle in Texas followed by high altitude testing in New Mexico.
  77. ↑ Klotz, Irene (October 17, 2013). "SpaceX Retires Grasshopper, New Test Rig To Fly in December". Space News. Retrieved October 21, 2013.
  78. ↑ Musk, Elon (August 22, 2014). "Three engine F9R Dev1 vehicle...". Twitter.com. Retrieved August 22, 2014.
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  86. ↑ "SpaceX Tests Recovered Falcon 9 Stage and Prepares for Next Launch". 15 January 2016. Retrieved 2016-01-15.
  87. ↑ Boyle, Alan (2016-01-17). "SpaceX rocket launches satellite, but tips over during sea landing attempt". GeekWire. Retrieved 2016-01-18.
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  89. ↑ "SpaceX: ice buildup may have led rocket to tip over". Washington Post (Washington Post). 2016-01-18. Retrieved 2016-01-18. Musk tweeted that the lockout collet on one of the rocket’s four legs didn’t latch, causing it to tip over after landing. He said the “root cause may have been ice buildup due to condensation from heavy fog at liftoff.”
  90. ↑ "returned falcon 9 booster fires up for static fire test". spaceflight101. 15 January 2016. Retrieved 18 January 2016.
  91. ↑ https://twitter.com/elonmusk/status/689299216607232000, 19 January 2016.

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