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Grasshopper in September 2012

Falcon 9 prototypes were experimental flight test reusable rockets that performed vertical takeoffs and landings.[1] The project was privately funded by SpaceX, with no funds provided by any government until later on.[2] Two prototypes were built, and both were launched from the ground.[3]

The earliest prototype was Grasshopper. It was announced in 2011[4] and began low-altitude, low-velocity hover/landing testing in 2012. Grasshopper was 106 ft (32 m) tall and made eight successful test flights in 2012 and 2013 before being retired. A second prototype of Falcon 9 was the larger and more capable Falcon 9 Reusable Development Vehicle (F9R Dev, also known as F9R Dev1) based on the Falcon 9 v1.1 launch vehicle. It was tested at higher altitudes and was capable of much higher velocity but was never tested at high velocity. The F9R Dev1 vehicle was built in 2013–2014 and made its first low-altitude flight test on 17 April 2014; it was lost during a three-engine test at the McGregor test site on 22 August 2014,[5] which ended the low-velocity test program. Further expansion of the flight test envelope for the reusable rocket was moved to descending Falcon 9 boosters that had been used on orbital flight trajectories on commercial orbital flights of the Falcon 9.

The Grasshopper and F9R Dev tests were fundamental to the development of the reusable Falcon 9 and Falcon Heavy rockets, which require vertical landings of the near-empty Falcon 9 and Falcon Heavy first-stage booster tanks and engine assemblies. The Grasshopper and the F9R Dev tests led into a series of high-altitude, high-speed controlled-descent tests of post-mission (spent) Falcon 9 booster stages that accompanied the commercial Falcon 9 missions since September 2013. The latter eventually resulted in the first successful booster landing on 21 December 2015.

History

[edit]
Grasshopper performing a 325-meter flight followed by a soft propulsive landing in an attempt to develop technologies for a reusable launch vehicle.

Grasshopper first became known publicly in the third quarter of 2011, when space journalists first wrote about it after analyzing space launch regulations of the Federal Aviation Administration.[1]

Shortly thereafter, SpaceX confirmed the existence of the test vehicle development program, and projected it would begin the Grasshopper flight test program in 2012.[4][6]

Releases of public information in 2011 indicated that the subsonic tests would occur in McGregor, Texas in three phases, at maximum flight altitudes of 670 to 11,500 ft (200 to 3,510 m), for durations of 45 to 160 s (0.75 to 2.67 min). At the time, testing was expected to take up to three years and the initial FAA permit allows up to 70 suborbital launches per year.[1][7] A half-acre concrete launch facility was constructed to support the test flight program.[6] In September 2012, SpaceX announced that they have requested FAA approval to increase the altitude of some of the initial test flights.[8] Looking forward to the next year, CEO Musk said in November 2012: "Over the next few months, we'll gradually increase the altitude and speed. ... I do think there probably will be some craters along the way; we'll be very lucky if there are no craters. Vertical landing is an extremely important breakthrough — extreme, rapid reusability."[9]

In May 2013, SpaceX announced that the higher-altitude, higher-velocity part of the Grasshopper flight test program would be done at Spaceport America near Las Cruces, New Mexico—and not at the Federal Government's adjacent White Sands Missile Range facility as previously planned[3][10][11][12]—and signed a three-year lease for land and facilities at the recently operational spaceport.[11] SpaceX indicated in May 2013 that they did not yet know how many jobs might move from Texas to New Mexico.[13]

SpaceX began constructing a 30 m × 30 m (98 ft × 98 ft) pad at Spaceport America in May 2013, 7 km (4.3 mi) southwest of the spaceport's main campus, planning to lease the pad for US$6,600 per month plus US$25,000 per test flight.[14]

Description

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Grasshopper

[edit]

Grasshopper consisted of "a Falcon 9 [v1.0] first-stage tank, a single Merlin-1D engine" with a height of 32 m (106 ft).[1] The landing gear was fixed.

As Elon Musk stated, Grasshopper could land on Earth with the accuracy of a helicopter.[15]

F9R Dev1

[edit]

F9R Dev1 was constructed out of the used first-stage tank of the Falcon 9 v1.1,[16] it was 160-foot tall,[17] nearly 50% longer than the first Grasshopper.[18] The landing legs were retractable by design, with a telescoping piston mounted on an A-frame. The total span of the four legs was approximately 18 m (60 ft) and the weight less than 2,100 kg (4,600 lb); the deployment system used high-pressure helium.[19] The legs had less weight than on the first Grasshopper. The F9R Dev1 had a different engine bay than the first Grasshopper vehicle.[18]

The F9R Dev1 vehicle in Texas was intended to take off and accelerate with three engines—as the test flight never needs the full thrust to take off a fully loaded Falcon 9 with an orbital payload—while completing the descent and landing with only one engine.[20] The original Grasshopper had flown exclusively with only a single Merlin 1D engine in place, the center engine which is now used to complete the last phase of the deceleration and vertical landing on full-scale Falcon 9 rockets.

F9R Dev2 (never flown)

[edit]

A third flight test vehicle—F9R Dev2—was initially planned to be flown only at the high-altitude test range at Spaceport America[11][2] and at altitudes of up to 91,000 meters (300,000 ft).[17][21][16] In September 2014, following the destruction of the F9R Dev1, SpaceX changed the plans, so the F9R Dev2 vehicle would fly first in McGregor for low-altitude testing. The initial FAA permit to fly the Falcon 9 Reusable Development Vehicle at McGregor in Texas was open until February 2015.[22]

On 19 February 2015 SpaceX announced that the F9R Dev2 would be discontinued.[23]

During April 2015, SpaceX performed tanking tests on the In-Flight Abort rocket on the Vandenberg Air Force Base SLC-4E. Since this rocket only had three Merlin 1D engines, and the New Mexico site was to have been used for testing the returned first stages, it was speculated that the discontinued F9R Dev2 was re-purposed as the launch vehicle in the In-Flight Abort Test.[24]

In May 2015, a press article stated that due to the technical success of many aspects of the booster rocket landing attempts on the sea and on the ASDS, SpaceX was planning on using the New Mexico site for testing the returned stages.[25][26]

Flight testing

[edit]

Grasshopper flight tests

[edit]

The first Falcon 9 prototype, Grasshopper, made a total of eight test flights between September 2012 and October 2013.[27] All eight flights were from the McGregor, Texas test facility.

Grasshopper began flight testing in September 2012 with a brief, three-second hop, followed by a second hop in November 2012 with an 8-second flight that took the testbed approximately 5.4 m (18 ft) off the ground, and a third flight in December 2012 of 29 seconds duration, with extended hover under rocket engine power, in which it ascended to an altitude of 40 m (130 ft) before descending under rocket power to come to a successful vertical landing.[28] Grasshopper made its eighth, and final, test flight on October 7, 2013, flying to an altitude of 744 m (2,441 ft) before making its eighth successful vertical landing.[29] The Grasshopper test vehicle is now retired.[27]

Flight tests at the Texas facility were limited to a maximum altitude of 2,500 ft (760 m) by the initial FAA regulatory permit.[30]

# Date (y-m-d) Highest altitude Duration Video Remarks
1 2012-09-21[10] 1.8 m (6 ft)[10] 3s[10] [31] A "brief hop"[32] with a near-empty tank.
2 2012-11-01[33] 5.4 m (17.7 ft)[33] 8s[33] [33]
3 2012-12-17[34] 40 m (131 ft)[34] 29s[34] [35] First flight to include the cowboy mannequin
4 2013-03-07[36] 80 m (262 ft)[37] 34s[37] [38] Touchdown thrust-to-weight ratio greater than one[39]
5 2013-04-17[40] 250 m (820 ft)[40] 58s [41] Demonstrated ability to maintain stability in wind[42]
6 2013-06-14[43] 325 m (1,070 ft)[43] 68s[44] [45] New navigation sensor suite tested; needed on the F9-R for precision landing[46]
7 2013-08-13[47] 250 m (820 ft)[47] 60s [48] Successfully completed a "divert test" performing 100 m (330 ft) lateral maneuver before returning to the pad.[47]
8 2013-10-07[49] 744 m (2,440 ft)[50] 79s[51] [50] Final flight of Grasshopper. Vehicle retired after the flight.[27]

From the announcement in 2011 until 2014, SpaceX has achieved each of the schedule milestones that they publicly announced. SpaceX said in February 2012 that they were planning several vertical-takeoff, vertical-landing (VTVL) test flights during 2012,[3] and confirmed in June 2012 that they continued to plan to make the first test flight within the next couple of months.[6]

F9R Dev1 flight tests

[edit]

The Falcon 9 Reusable Development Vehicle, or F9R Dev, was announced in October 2012. F9R Dev1 was initially named, since late 2012 until early 2014, as Grasshopper v1.1.[17][29] In March 2013 Musk said that SpaceX hoped to reach hypersonic speed before the end of 2013.[52] In March 2013, it was announced that the second Grasshopper-class suborbital flight vehicle would be constructed out of the Falcon 9 v1.1 first-stage tank that had been used for qualification testing in Texas at the SpaceX Rocket Development and Test Facility prior to March.[16]

In 2014, the FAA permit was increased to 10,000 ft (3,000 m) for the F9R Dev testing at McGregor,[21] when the first Grasshopper was limited to an altitude of 2,500 ft (760 m).

The F9R Dev1 was built on the much longer Falcon 9 v1.1 first stage tanks, and with retractable landing legs.

SpaceX performed a short-duration ground test (static test) of F9R Dev1 on March 28, 2014, at their McGregor, Texas test site,[53] and made their maiden test flight of the new vehicle, to an altitude of 250 meters (820 ft), on April 17, 2014.[21][20] The F9R Dev1 flew for the fifth and last time on August 22, 2014.[17][54] During this flight, anomalous sensor data from the vehicle during its ascent caused the rocket to deviate from nominal flight trajectory, prompting its flight termination system to end the mission by neutralizing the vehicle. No injuries or near-injuries were reported following the breakup of F9R Dev1 and an FAA representative was present during the test. Video from the accident was released by CBS and multiple images from the accident were posted on social media.[5][55]

Test # Date (year-month-day) Test vehicle Location Highest altitude Video Remarks
1 2014-04-17[17] F9R Dev1 McGregor 250 m (820 ft)[17] [56] Hovered, moved sideways, landed successfully.[20]
2 2014-05-01[57] F9R Dev1 McGregor 1,000 m (3,280 ft)[58] [58] Hovered, moved sideways, landed.[57]
3 2014-06-17 F9R Dev1 McGregor 1,000 m (3,280 ft)[59] [59] First test flight with steerable grid fins.[59]
4 2014-08-01[60] F9R Dev1 McGregor No public information was provided by SpaceX about this flight.[61]
5 2014-08-22[60] F9R Dev1 McGregor [62][63] Vehicle was destroyed following a flight anomaly that began to take F9R Dev1 off of its planned flight path. No injuries.[54][64] A blocked sensor was the cause of the anomaly. The sensor had no backup in the prototype F9R Dev vehicle but flight-rated Falcon 9 rockets do have a redundant backup.[65] First activation of an autonomous flight termination system on a US rocket.[66]

Falcon 9 post-mission landing tests

[edit]
Falcon 9 first stage attempts landing on ASDS after second stage with CRS-6 continued onto orbit. Landing legs are in the midst of deploying.
Main article: Falcon 9 first-stage landing tests

In 2013, SpaceX moved to using their mainstream Falcon 9 vehicles for VTVL testing, in addition to their existing tests with flying test vehicles. In March 2013, SpaceX announced that, beginning with the first flight of the stretch version of the Falcon 9 launch vehicle—the sixth flight overall of Falcon 9 (then anticipated for summer 2013), every first stage would be instrumented and equipped as a controlled descent test vehicle.[67] SpaceX attempted numerous over-water landings, both over the sea, resulting in soft landings into the water, and onto specialized Autonomous Spaceport Drone Ships, barges modified to be landing platforms. None were completely successful.

SpaceX eventually succeeded in landing a production vertical-landing rocket on land in late 2015. The first attempt to land the first stage of the Falcon 9 on land, near its launch site, occurred on Falcon 9 Flight 20, on 21 December 2015. The landing was successful, and the first stage of the Falcon 9 Full Thrust vehicle was recovered.[68][69][70] By May 27, 2016, SpaceX had successfully completed three first-stage landings on a drone ship at sea.[71]

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Falcon 9 prototypes

View on Grokipedia
from Grokipedia
The Falcon 9 prototypes were a series of experimental suborbital vehicles developed by to demonstrate and refine vertical takeoff, vertical landing () technologies essential for achieving reusability in the rocket's first stage, with the goal of drastically reducing launch costs through rapid turnaround and recovery. These prototypes, privately funded by , underwent a progression of increasingly complex test campaigns at the company's facility between 2012 and 2014, paving the way for the operational reusability demonstrated in full orbital missions starting in 2015. The initial prototype, known as Grasshopper, was a single-engine testbed constructed around the first-stage tank of an early Falcon 9 v1.0 qualification unit, standing approximately 32 meters (106 feet) tall with fixed landing legs and powered by one Merlin 1D engine. Its purpose was to validate basic VTVL maneuvers, including precise hovers and controlled descents, using the full navigation sensor suite and closed-loop control systems derived from the design. completed eight successful test flights from September 2012 to October 2013, progressively increasing in altitude and complexity: early hops reached 1.8 to 40 meters, later tests achieved 250 meters in April 2013 and a sideways divert of 100 meters at 250 meters altitude in August 2013, with a record 744 meters (2,440 feet) on October 7, 2013, before soft-landing on the pad each time. Following these successes, was retired in late 2013 as testing shifted to more advanced configurations. Succeeding Grasshopper was the F9R Dev1, a more capable prototype based on the Falcon 9 v1.1 first-stage structure, featuring three Merlin 1D engines for greater thrust and the first implementation of deployable landing legs to simulate operational recovery scenarios. Designed to push the limits of multi-engine control, cold-gas thrusters, and higher-altitude hovers, F9R Dev1 conducted five test flights from April 17 to August 22, 2014, including a notable 1,000-meter ascent on May 1, 2014. The program encountered a setback on its final flight, when an onboard anomaly—detected during a complex multi-engine test—triggered the flight termination system, resulting in the vehicle's destruction over McGregor without injuries; SpaceX described this as an expected part of iterative testing to identify issues early. A second vehicle, F9R Dev2, was constructed with similar specifications for planned high-altitude tests at Spaceport America, New Mexico, but was discontinued in February 2015 amid accelerating progress in orbital landing attempts, with its hardware dismantled. These prototype efforts were instrumental in developing the software, propulsion gimballing, and aerodynamic control systems that enabled the Falcon 9's first successful orbital booster on December 21, 2015, marking a in commercial spaceflight reusability and influencing subsequent Block 5 vehicles capable of over 20 reflights. By validating at suborbital scales, the program reduced development risks for full missions and contributed to SpaceX's broader vision of routine, cost-effective access to space.

Development Background

Program Origins

SpaceX was founded in May 2002 by with the goal of reducing the cost of space travel through the development of reusable technology, beginning with the expendable two-stage designed for deployment to . The , powered by the engine in its first stage and the engine in its second, represented SpaceX's initial effort to create a reliable, low-cost orbital using off-the-shelf components and in-house manufacturing to compete with established aerospace firms. Following the Falcon 1's first successful orbital flight on September 28, 2008—the first achieved by a privately developed liquid-fueled —SpaceX began pivoting toward reusability to further drive down launch costs and enable ambitious goals like Mars colonization. This shift was influenced by earlier experimental programs, notably NASA's DC-X (Delta Clipper-Experimental) from the mid-1990s, a suborbital that successfully demonstrated vertical takeoff, horizontal flight, and vertical landing using RL10A-5 engines and composite materials. The DC-X's rapid development cycle and proof-of-concept for single-stage reusability informed 's strategy, emphasizing iterative testing over traditional expendable designs despite the engineering challenges this imposed on the program. In September 2011, SpaceX announced the project as a dedicated, low-cost VTOL testbed to validate reusable first-stage technologies for future rockets, building on the engine lineage that originated with . Early prototypes, first static-fired in March 2003 at the McGregor test facility, provided the foundational propulsion system, achieving initial thrust levels of around 60,000 pounds while undergoing iterative improvements for reliability. Constrained by private funding sources—including Musk's personal investments and —SpaceX adopted simplified prototype architectures to minimize development costs and accelerate validation of reusability, avoiding the high expenses of full-scale orbital vehicles during early experimentation. This lean approach, reliant on surplus hardware and modular designs, allowed rapid prototyping under financial pressures that nearly bankrupted the company prior to the 2008 Falcon 1 success.

Reusability Objectives

The primary goal of the Falcon 9 prototype program was to demonstrate controlled vertical landings of the first-stage booster to enable its recovery and after launch, fundamentally aiming to lower the overall cost of access by reflying the most expensive component of the rocket. This reusability approach sought to reduce per-launch expenses from around $60 million for expendable flights to a fraction of that through multiple uses of the same hardware, with projecting significant savings by avoiding the need to manufacture new boosters for each mission. Secondary objectives included validating key technologies essential for precise booster control during and landing, such as cold gas thrusters for attitude adjustments and autonomous guidance software to manage the without ground intervention. Cold gas thrusters, utilizing pressurized , provided reliable, low-complexity control for pointing and roll during the booster's return, complementing the main engines. The autonomous software handled real-time navigation, ensuring stability through phases like boost-back burns and entry. These elements were tested iteratively to integrate seamlessly with the full architecture. The program specifically addressed engineering challenges inherent to propulsive landings, including managing high dynamic pressure environments during atmospheric reentry, achieving precise throttle modulation of engines for stable hover and touchdown, and executing landings without parachutes to enable pinpoint accuracy and rapid turnaround. Early experiments, such as those with the prototype, served as subscale validations before scaling to full-size implementations on operational boosters. Economically, the reusability focus targeted at least 10 reuses per booster to drive costs down to approximately $1,000 per kilogram to , a dramatic improvement over the $10,000+ per kilogram typical for expendable launchers at the time.

Grasshopper Prototype

Design and Specifications

The Grasshopper prototype featured a single-stage structure measuring 32 m (106 ft) in height, incorporating the tankage from the first stage. This configuration allowed for suborbital testing of maneuvers while maintaining compatibility with core hardware elements, such as carbon-overwrapped pressure vessels (COPVs) for pressurization. Propulsion was provided by a single Merlin 1D engine, delivering sea-level of approximately 650 kN (147,000 lbf) and capable of throttling between 50% and 100% to enable precise descent control. The vehicle used (refined kerosene) and (LOX) as propellants, stored in the shared tankage, with a pressurant system employing or to inert the tanks and maintain structural integrity during flight. Guidance and control systems included four nitrogen-fed cold gas thrusters for attitude adjustments, supplemented by GPS and inertial navigation (INS) for positioning and trajectory management; steering during early operations relied on gimbaling of the main engine, without the addition of grid fins. The landing system comprised four fixed steel legs, initially requiring manual deployment, which provided stable support upon touchdown. In contrast to the operational , represented a subscale with only one engine instead of nine, omitting the upper stage and to prioritize reusability validation over orbital capability.

Flight Test Campaign

The flight test campaign took place at SpaceX's facility, beginning in September 2012 and spanning approximately 13 months. The series consisted of eight progressively ambitious vertical takeoff and landing () demonstrations, all successful with no failures, aimed at validating the vehicle's ability to perform controlled ascents, hovers, and descents while collecting data on key reusability elements such as thrust vector control, aerodynamic stability, and autonomous guidance software. The campaign began with short, low-altitude hops to confirm basic liftoff and landing capabilities. The first flight on , 2012, achieved a brief 3-second hover at 1.8 meters, demonstrating initial systems integration. The second, on November 1, 2012, extended to 8 seconds at 5.4 meters, incorporating a short hover phase. Subsequent tests rapidly scaled in height and duration: the third on December 17, 2012, reached 40 meters for 29 seconds, marking the first inclusion of a test to simulate effects. By March 7, 2013, the fourth flight hovered at 80 meters for 34 seconds, achieving a touchdown exceeding one for enhanced landing control. Advancements continued with the fifth flight on April 17, 2013, climbing to 250 meters over 58 seconds while testing stability in windy conditions. The sixth, on June 14, 2013, attained 325 meters in 68 seconds, validating a new navigation sensor suite essential for precise landings. The seventh flight on , 2013, returned to 250 meters for about 60 seconds but introduced a divert maneuver, shifting laterally 100 meters mid-flight before centering on the pad. The campaign culminated on October 7, 2013, with the eighth and final flight reaching a record 744 meters in 79 seconds, after which was retired in favor of more advanced prototypes. These tests provided foundational data for subsequent recovery efforts, confirming the feasibility of propulsive landings without reliance on extensive ground infrastructure.
FlightDateAltitudeDurationRemarks
1Sep 21, 20121.8 m3 sInitial systems check with near-empty tank.
2Nov 1, 20125.4 m8 sFirst hover demonstration.
3Dec 17, 201240 m29 sIncluded test ; steady ascent/descent.
4Mar 7, 201380 m34 s TWR >1; doubled prior height.
5Apr 17, 2013250 m58 sWind stability validation.
6Jun 14, 2013325 m68 sTested new navigation sensors.
7Aug 13, 2013250 m60 s100 m lateral divert and recenter.
8Oct 7, 2013744 m79 sRecord height; vehicle retired post-flight.

F9R Development Vehicles

F9R Dev1

The F9R Dev1 (Falcon 9 Reusable Development Vehicle 1) was a key prototype in SpaceX's reusability program, serving as an evolution from the single-engine Grasshopper demonstrator to validate vertical takeoff and landing (VTVL) technologies on a full-scale Falcon 9 configuration. Built in 2013–2014, it enabled testing of critical systems for first-stage recovery under more demanding conditions, including multi-engine operations and atmospheric control. The vehicle utilized the full-scale first-stage tank, measuring approximately 41 m (135 ft) in height, and was powered by three Merlin 1D engines arranged in a triangular configuration, with the center engine throttlable to 40% thrust for fine control during descent and landing maneuvers. It incorporated several innovations, including the first deployment of retractable pneumatic landing legs derived from evolving designs, which allowed for compact storage during ascent and reliable extension for touchdown. Initial testing of grid fins for reentry stability was also conducted on the prototype, alongside upgraded avionics systems adapted from to handle increased complexity in guidance and propulsion coordination. These features supported aggressive test profiles aimed at simulating real mission stresses. Flight testing occurred at SpaceX's McGregor facility in Texas from early 2014 through August, with several low-altitude hops demonstrating VTVL controllability and soft landings limited by FAA airspace restrictions to under 1,000 m. The inaugural public test on April 17 reached 250 m altitude for a successful hover and landing, validating basic multi-engine stability. A subsequent flight on May 1 achieved 1,000 m, quadrupling the prior height while executing a controlled hover and precise touchdown, showcasing improved ascent and descent performance. An additional test in June focused on steerable grid fins for enhanced aerodynamic control during simulated reentry phases. These efforts progressively built confidence in the vehicle's dynamics. The program concluded on August 22 during a more ambitious test, when anomalous sensor readings triggered an uncommanded engine shutdown at low altitude, activating the flight termination system and destroying the vehicle mid-air with no injuries reported. Post-incident analysis identified a faulty engine sensor as the root cause, leading to software updates and hardware redundancies implemented in subsequent Falcon 9 development to mitigate similar risks. Overall, the F9R Dev1 provided essential data on multi-engine synchronization, higher-altitude maneuvers, and reusability hardware integration, directly informing the shift toward operational propulsive landings.

F9R Dev2

The F9R Dev2 was the second and final planned development vehicle in SpaceX's Falcon 9 Reusable (F9R) prototype series, intended to build on lessons from the F9R Dev1 by enabling more advanced vertical landing tests at higher altitudes and velocities. Constructed partially in 2014 at SpaceX's McGregor test facility in , it utilized a first-stage structure approximately 41 m (135 ft) tall, equipped with three 1D engines configured for full control. Key upgrades over the F9R Dev1 included enhanced structural integration for stacking with a second-stage to replicate full-vehicle dynamics during descent, as well as the capability for high-altitude flights reaching up to 91 kilometers (300,000 feet) to simulate hypersonic reentry conditions. The design incorporated advanced aerodynamic features such as grid fins for atmospheric maneuvering and was planned to feature autonomous landing legs for propulsive touchdown, advancing toward operational reusability goals. These elements aimed to test the full complement of technologies needed for first-stage recovery without risking live missions. Although the vehicle underwent static tanking tests in April 2015 at Vandenberg Air Force Base's SLC-4E pad as part of preparations for a potential Crew Dragon in-flight abort demonstration, it never conducted flight tests. SpaceX canceled the F9R Dev2 program in February 2015, deeming the data from Dev1's low-altitude hops—combined with early sea recovery attempts on operational flights like CRS-3 in April 2014—sufficient to proceed directly to orbital-class landing experiments, thereby accelerating development timelines and reducing costs associated with dedicated prototypes. Following its decommissioning, the F9R Dev2 remained in storage near Landing Zone 4 at Vandenberg until late 2018, when it was dismantled and scrapped. This decision reflected SpaceX's pivot to iterative testing on flight-proven hardware, marking the end of standalone prototype campaigns for first-stage reusability.

Testing Legacy

Key Achievements and Lessons

The Falcon 9 prototype program marked a pivotal advancement in reusable rocket technology by proving the feasibility of vertical takeoff and vertical landing (VTVL) maneuvers. The Grasshopper prototype successfully executed eight test flights between 2012 and 2013, demonstrating stable hovers and precise landings, with its highest achieving an altitude of 744 meters before a controlled return to the launch pad. These tests validated core VTOL principles using a single Merlin engine and fixed landing legs, laying the groundwork for more complex operations. Meanwhile, the F9R development vehicles extended this success to multi-engine configurations, showcasing improved stability during ascent and descent phases with three Merlin 1D engines and retractable legs. A key outcome was the maturation of autonomous guidance and control software, initially honed on these prototypes, which has since enabled over 500 successful first-stage recoveries in operational missions as of November 2025. This software integrates real-time sensor data for trajectory corrections, engine throttling, and landing precision, reducing reliance on ground intervention. The prototypes' iterative testing directly contributed to over 500 booster landings as of November 2025, transforming reusability from concept to routine practice and enabling to refly boosters up to 31 times per unit. The program also yielded critical lessons on reliability and limitations. The F9R Dev1 conducted five test flights from April to August 2014, with its final flight ending in an anomaly due to faulty data during ascent, triggering the flight termination and underscoring the need for robust control and precision to prevent deviations in multi-engine setups. Early reliance on cold gas thrusters for attitude control, as implemented on for lateral maneuvers, revealed their insufficiency for full-scale vehicles due to limited thrust from pressurized , prompting upgrades to more powerful reaction control systems in operational boosters. Testing across the prototypes—totaling more than a dozen flights—generated extensive data on , , and integration, validating computational simulations for high-speed orbital reentry and descent. These insights helped overcome environmental challenges, including management through enhanced guidance algorithms that adjust for gusts during low-altitude hovers, and slosh mitigation via internal baffles in fuel tanks to maintain stable . Economically, the prototypes exemplified cost-effective development, integrated into the broader program that completed for approximately $300–$400 million—far below NASA's $4 billion estimate for a comparable expendable —allowing rapid iteration without prohibitive expenses compared to traditional billion-dollar new rocket programs. This approach not only accelerated reusability but also demonstrated scalable savings, with each reused booster avoiding the need for full hardware replacement.

Transition to Operational Landings

The transition from prototype testing to operational landings on Falcon 9 missions began with early post-mission recovery attempts that built directly on lessons from the Grasshopper and F9R development vehicles. The first such effort occurred during the CRS-3 mission on April 18, 2014, when the Falcon 9 first stage, equipped with newly integrated landing legs inspired by F9R designs, attempted a controlled soft splashdown in the Atlantic Ocean. However, the stage exhausted its hydraulic fluid during descent, forcing reliance on low-thrust cold gas thrusters for attitude control, which resulted in insufficient deceleration and a hard ocean impact. Subsequent attempts refined these prototype-derived elements, including the adoption of grid fins from F9R testing for aerodynamic steering during reentry and software algorithms from for the precise hover-slam maneuver. On the CRS-6 mission launched April 14, 2015, the first stage targeted SpaceX's (ASDS) in the Atlantic, marking the inaugural barge landing trial. The booster successfully reached the platform but experienced excessive descent velocity, leading to a hard touchdown that caused it to tip over shortly after contact—a partial success that validated the propulsive landing sequence in an operational context. These initial efforts paved the way for the first full success: a Return to Launch Site (RTLS) landing on December 21, 2015, during the ORBCOMM-2 mission, where the first stage propulsively touched down on Landing Zone 1 at after deploying 11 satellites to orbit. This milestone, achieved through iterative refinements to prototype hardware like foldable legs and grid fins, enabled routine recoveries by 2017, with boosters increasingly returning via either RTLS for lighter payloads or downrange ASDS landings for heavier missions to optimize fuel margins. By mid-2025, reached its 500th launch, with the program continuing to set reuse records, including a booster completing 31 flights in 2025. Unlike the suborbital, low-velocity profiles of and F9R tests, operational reentries involved full orbital insertion velocities exceeding Mach 8, necessitating an entry burn to reduce speed from hypersonic to subsonic levels and mitigate plasma heating on the interstage and engine compartments. Heat protection for these high-energy reentries relied on ablative materials and precise burn timing rather than ceramic tiles, which were tested separately for fairing recovery efforts that paralleled booster techniques by using ships for mid-air catches. By November 2025, had achieved over 500 successful first-stage landings across more than 570 missions, a reliability rate exceeding 97%, which facilitated booster reuses of up to 31 flights per unit and drastically reduced launch costs through propulsive recovery. Lessons from early failures, such as the Dev1 explosion, informed safer ignition sequences without repeating ground-test specifics. This evolution from prototype validation to operational dominance underscored the scalability of vertical landing for commercial orbital access.

References

  1. https://space.skyrocket.de/doc_lau/grasshopper.htm
  2. https://www.space.com/26921-spacex-reusable-rocket-explodes-over-texas-video.html
  3. https://www.nbcnews.com/sciencemain/spacexs-grasshopper-reusable-rocket-makes-highest-leap-yet-6c10573570
  4. https://www.space.com/22379-spacex-grasshopper-rocket-sideways-flight-video.html
  5. https://newatlas.com/grasshopper-retires-altitude-record/29384/
  6. https://www.sma.nasa.gov/LaunchVehicle/assets/spacex-falcon-9-v1.2-data-sheet.pdf
  7. https://www.elonx.net/cancelled-spacex-projects-f9r-dev2-and-spaceport-america/
  8. https://www.spacex.com/assets/media/falcon-users-guide-2025-05-09.pdf
  9. https://www.businessinsider.com/spacex-history-biggest-moments-elon-musk-2022-12
  10. https://www.smithsonianmag.com/air-space-magazine/the-tale-of-falcon-1-5193845/
  11. https://www.wired.com/2008/09/space-x-did-it/
  12. https://www.discovermagazine.com/dc-x-the-nasa-rocket-that-inspired-spacex-and-blue-origin-40911
  13. https://frstrategie.org/sites/default/files/documents/publications/autres/2017/2017-wohrer-these.pdf
  14. https://www.smithsonianmag.com/air-space-magazine/is-spacex-changing-the-rocket-equation-132285884/
  15. https://www.space.com/26042-spacex-grasshopper.html
  16. https://www.spacedaily.com/news/rocketscience-03k.html
  17. https://spacenews.com/spacex-performs-first-rocket-engine-firing/
  18. https://www.spacex.com/vehicles/falcon-9/
  19. https://spacenews.com/spacexs-reusable-falcon-9-what-are-the-real-cost-savings-for-customers/
  20. https://www.popularmechanics.com/space/rockets/a7446/elon-musk-on-spacexs-reusable-rocket-plans-6653023/
  21. https://spaceflightnow.com/news/n1207/10grasshopper/
  22. https://nstxl.org/reducing-the-cost-of-space-travel-with-reusable-launch-vehicles/
  23. https://www.faa.gov/about/office_org/headquarters_offices/ast/media/20110922%2520spacex%2520grasshopper%2520draft%2520ea.final.pdf
  24. https://sma.nasa.gov/LaunchVehicle/assets/spacex-falcon-9-data-sheet.pdf
  25. https://www.pcmag.com/news/spacex-grasshopper-rocket-performs-sideways-maneuver
  26. https://spacenews.com/37740spacex-retires-grasshopper-new-test-rig-to-fly-in-december/
  27. https://www.space.com/19039-spacex-private-reusable-rocket-test.html
  28. https://spacenews.com/32173spacex-fires-up-reusable-grasshopper-test-rig-again/
  29. https://www.nasaspaceflight.com/2012/12/spacexs-grasshopper-conducts-40-meter-leap/
  30. https://www.americaspace.com/2013/03/10/spacex-conducts-fourth-successful-grasshopper-launch-doubles-previous-altitude/
  31. https://www.nasaspaceflight.com/2013/08/spacex-bothering-bovines-revolutionizing-rockets/
  32. https://www.nasaspaceflight.com/2014/08/spacex-static-fire-asiasat-6-test-failure/
  33. https://www.wevolver.com/specs/falcon-9-v12-or-full-thrust-block-5
  34. https://www.kvue.com/article/news/state/spacex-rocket-explodes-during-test-flight-no-injuries/269-310053984
  35. https://spacenews.com/40457spacexs-f9r-reusable-rocket-test-bed-flies-again/
  36. https://www.universetoday.com/articles/spacex-rocket-prototype-explodes-in-texas-rockets-are-tricky-musk-says
  37. https://www.nasaspaceflight.com/2015/04/spacex-tanking-tests-in-flight-abort-falcon-9/
  38. https://www.nasaspaceflight.com/2015/03/spaceport-america-spacex-reusability-testing/
  39. https://www.nasaspaceflight.com/2020/01/spacex-crew-dragon-in-flight-abort-test/
  40. https://arstechnica.com/space/2024/02/rocket-report-falcon-9-flies-for-300th-time-ariane-6-ships-to-kourou/
  41. https://everydayastronaut.com/rocket-engine-cycles/
  42. https://spacenews.com/nasa-finishes-wind-tunnel-testing-falcon-9-1st-stage/
  43. https://www.quora.com/Do-spacecraft-fuel-tanks-require-baffles-to-prevent-fuel-from-sloshing-around-too-much
  44. https://payloadspace.com/rocket-development-costs-by-vehicle-payload-research/
  45. https://www.nasa.gov/wp-content/uploads/2015/01/586023main_8-3-11_NAFCOM.pdf
  46. https://newatlas.com/falcon-9-landing/31797/
  47. https://spacenews.com/spacex-launches-dragon-cargo-spacecraft-rocket-stage-makes-hard-landing-2/
  48. https://www.theverge.com/2015/12/21/10640306/spacex-elon-musk-rocket-landing-success
  49. https://space.stackexchange.com/questions/17878/why-does-the-spacex-falcon-9-rocket-do-a-180-flip-for-reentry
  50. https://www.space.com/space-exploration/launches-spacecraft/400-rocket-landings-spacex-notches-reuse-milestone
  51. https://www.nasaspaceflight.com/2025/07/spacex-roundup-q22025/
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