Reusable launch vehicle
A reusable launch vehicle (RLV) is a type of spacecraft or rocket system engineered to return to Earth substantially intact following the delivery of its payload to orbit or beyond, allowing for refurbishment and relaunch multiple times to reduce operational costs compared to expendable vehicles.[1][2] The concept of reusability emerged in the mid-20th century amid efforts to make space access more economical, with early studies by NASA exploring recovery techniques for boosters and stages as far back as the 1960s.[3] The first operational realization came with NASA's Space Shuttle program, launched in 1981, which featured a reusable orbiter vehicle and solid rocket boosters that were recovered and refurbished for 135 missions until the program's retirement in 2011; this partially reusable design demonstrated the feasibility of reuse but highlighted challenges like high maintenance costs and limited flight rates.[4][5] In the 21st century, private sector innovation has driven significant advancements, particularly through SpaceX's Falcon 9 rocket, introduced in 2010, whose first-stage boosters land propulsively on drone ships or ground pads for recovery and reuse—achieving over 500 successful landings by late 2025 and enabling individual boosters to fly up to 31 times, dramatically lowering per-launch costs to under $3,000 per kilogram to low Earth orbit.[6][7][8] This success has spurred competition, with systems like Rocket Lab's Electron rocket incorporating reusable components, Blue Origin's New Glenn which demonstrated partial reusability on its maiden flight and first-stage landing in November 2025, while international efforts include China's reusable variants of the Long March series.[9] Ongoing developments focus on fully reusable architectures to further slash costs and enable high-cadence missions for satellite deployment, crewed exploration, and interplanetary travel; SpaceX's Starship, a two-stage system designed for complete reusability with rapid turnaround, has undergone multiple test flights since 2023, aiming for orbital operations and beyond by 2026, potentially carrying 150 metric tons to orbit at a fraction of traditional expenses.[10][11] The economic advantages of RLVs, including economies of scale and reduced manufacturing needs, are projected to expand the space economy by making launches routine and affordable, supporting NASA's Artemis program and commercial ventures alike.[12][13]Overview
Definition and Principles
A reusable launch vehicle (RLV) is a launch system engineered to deliver payloads to orbit while returning substantially intact to Earth, allowing for recovery, refurbishment, and multiple subsequent flights to achieve cost reductions over single-use alternatives.[1] This design emphasizes the vehicle's ability to perform repeated missions, distinguishing it from expendable launch vehicles that are discarded after one use, thereby prioritizing lifecycle cost efficiency through hardware reuse rather than optimizing for minimal mass in disposable components.[14] Core engineering principles of RLVs center on maintaining structural integrity across multiple stress cycles, including the extreme loads from ascent, orbital insertion, atmospheric reentry, and landing, which necessitate robust materials and higher safety margins compared to expendable systems.[14] Vehicles must incorporate recovery hardware, such as guidance and control systems for precise descent, which adds mass—but enables intact recovery and minimizes refurbishment needs.[14] Propellant loading represents another key principle, involving the refueling of cryogenic or storable propellants prior to each launch, typically hours before liftoff, to support rapid turnaround without replacing propulsion elements.[15] The basic operational cycle of an RLV begins with propellant loading and launch from Earth, followed by ascent to orbit, payload deployment, controlled reentry through the atmosphere, and landing at a designated site for recovery.[14] Post-landing, the vehicle undergoes inspection and refurbishment to verify structural integrity and component functionality, enabling recertification and preparation for relaunch, with goals to reduce turnaround time to days or even hours.[16] This cycle integrates reusability from the conceptual design phase, favoring operability and reliability over peak performance to sustain frequent operations.[14]Advantages and Challenges
Reusable launch vehicles provide substantial cost advantages by distributing the expense of hardware across multiple missions, thereby lowering per-launch expenditures. For SpaceX's Falcon 9, reusability has reduced launch costs to approximately $67 million as of 2023, compared to $160 million for equivalent expendable systems like the ULA Atlas V.[17][18] The cost per kilogram to low Earth orbit has similarly declined from $10,000 to about $2,900 through booster reuse and refurbishment as of November 2025, with individual boosters reused up to 30 times amortizing costs effectively.[19][20] At high flight rates, such as 200 launches annually, reusable systems can achieve costs as low as 52% of expendable vehicles, or roughly $10 million per launch for certain configurations. These vehicles also enhance sustainability by minimizing space debris generation and resource demands. By recovering and reflights components, reusables prevent the addition of discarded stages to orbit, where rocket bodies including spent upper stages account for approximately 5% of cataloged objects and contribute significantly to annual debris mass increases.[21] Reduced manufacturing requirements further lower overall resource consumption and environmental impacts associated with producing new rockets for each mission. Reusability supports higher launch cadence, enabling more frequent missions critical for deploying large satellite constellations or conducting crewed operations. This increased frequency, driven by lower costs and rapid turnaround, has facilitated the rapid buildup of mega-constellations exceeding 10,000 satellites in some cases. Despite these benefits, reusable launch vehicles face notable challenges, including elevated upfront development costs—often three times those of expendable designs—due to the need for advanced recovery and durability features. Ensuring reliability over 10 or more flights per vehicle adds engineering complexity, with issues like material wear under repeated thermal and mechanical stresses requiring extensive testing and maintenance. The Falcon 9 first stage, for instance, has achieved up to 30 reuses as of November 2025, demonstrating progress but highlighting ongoing demands for robust re-flight guarantees.[20] A primary quantitative trade-off is the approximately 30% reduction in payload fraction to accommodate extra mass for landing legs, grid fins, and return propellant, which initially limits mission capacity but yields net savings through repeated use.System Configurations
Fully Reusable Vehicles
Fully reusable launch vehicles represent architectures in which all primary elements—such as boosters, core stages, and upper stages—are engineered to separate, reenter the atmosphere, and land intact for recovery, refurbishment, and relaunch. These systems often employ multi-stage configurations where each component contributes to ascent while maintaining independent yet coordinated return capabilities, enabling the entire stack to be reused without discarding major hardware. This integrated approach contrasts with expendable designs by prioritizing durability and minimal maintenance across the vehicle.[10] Key design features enhance the feasibility of full-system reuse. Propellant cross-feeding allows transfer of fuel and oxidizer from lower to upper stages during powered flight, optimizing mass distribution and reducing structural penalties associated with carrying return propellant reserves. In analyzed two-stage configurations, cross-feeding achieves dry mass reductions of 2% to 14% over non-cross-fed parallel-burn setups, directly improving propellant efficiency by allowing stages to deplete tanks more completely before separation. Synchronized recovery trajectories coordinate the descent paths of all elements to converge on designated landing zones, often using powered vertical descents for precision. Unified avionics architectures integrate guidance, navigation, and control systems across stages, streamlining data sharing and autonomous operations for the full stack.[22] SpaceX's Starship exemplifies this architecture as a fully reusable, two-stage-to-orbit system comprising the Super Heavy booster and Starship spacecraft, both utilizing methalox (methane and liquid oxygen) propulsion via Raptor engines. The design incorporates cross-feeding to supply the upper stage from the booster's reserves during ascent, supporting efficient staging. As of October 2025, Starship has completed 11 integrated flight tests from Starbase, Texas, validating elements like booster hot-staging separation and controlled returns, though routine full-stack reuse remains in iterative development.[10][23] Theoretical performance metrics underscore the scalability of fully reusable vehicles. Designs target reuse cycles exceeding 100 flights per vehicle, amortizing fixed costs and enabling launch cadences of multiple missions per day with minimal refurbishment. Propellant efficiency gains from cross-feeding and optimized trajectories can yield payload capacities up to 150 metric tons to low Earth orbit in reusable mode, with overall system costs potentially reduced by factors of 10 or more through high flight rates.[10][24]Partially Reusable Vehicles
Partially reusable vehicles represent a hybrid approach in launch system design, where only specific components, such as the first stage or booster, are recovered and reflown, while others like the upper stage are discarded after use. This configuration prioritizes the reuse of the lower portions of the vehicle, which separate earlier in the ascent and experience less extreme conditions during return. For instance, the SpaceX Falcon 9 employs booster-only reuse, recovering its first stage via powered landing while expending the second stage to achieve orbital insertion.[25][26] Engineering trade-offs in partially reusable systems favor recovering lower stages due to their suborbital reentry velocities, typically around 2-3 km/s, which reduce thermal and structural stresses compared to upper stages that must decelerate from orbital speeds exceeding 7 km/s. This simplification lowers the mass penalties associated with recovery hardware, such as propulsion reserves and control systems, enabling more feasible refurbishment cycles without compromising payload capacity. The Falcon 9 exemplifies these benefits, with its first stage boosters achieving reuse rates exceeding 30 flights per vehicle by late 2025, demonstrating cost reductions through repeated operations while maintaining operational reliability.[27][28][29] Recovery mechanisms for these partial systems integrate aerodynamic and propulsive elements tailored to the booster's descent profile, including deployable grid fins for atmospheric steering and cold gas thrusters for fine attitude control during reentry and landing burns. In the Falcon 9, four titanium grid fins provide aerodynamic deceleration and guidance from hypersonic speeds down to subsonic, while nitrogen cold gas thrusters in podded clusters enable precise orientation without contaminating the main engines. These systems add minimal dry mass—approximately 2-3% of the booster's inert weight—yet ensure pinpoint landings on drone ships or ground pads.[26][25] The evolution of partial reusability has progressed from initial efforts in recovering secondary components like payload fairings to full-scale stage recovery in operational fleets. SpaceX's program began with successful fairing recoveries using parachutes and recovery vessels starting in 2018, achieving reuse of fairing halves up to 34 times as of November 2025 to incrementally reduce costs. This built toward routine booster recoveries, with over 440 first-stage landings as of November 2025, highlighting a stepwise maturation that balances complexity with economic viability. Refurbishment for partial systems, such as booster inspections, adds 1-2 months per turnaround but supports higher launch cadences than fully expendable designs.[30][29][31][32]Reusable Upper Stages and Spacecraft
Reusable upper stages represent a critical advancement in launch vehicle architecture, enabling the recovery and reuse of components that operate in orbit after payload separation. These stages typically incorporate propulsion systems for controlled deorbit maneuvers, atmospheric reentry, and powered landings, distinguishing them from expendable designs by reserving propellant margins specifically for return operations. For instance, the Starship upper stage, developed by SpaceX, is engineered for full reusability through propulsive recovery, utilizing its Raptor engines to perform deorbit burns from low Earth orbit (LEO) and subsequent vertical landings on Earth or other celestial bodies. This approach allows the stage to execute precise trajectory adjustments post-mission, facilitating rapid turnaround for subsequent flights.[33] Dedicated spacecraft, such as crewed capsules and cargo variants, further exemplify reusability in orbital operations by integrating robust reentry systems with recovery mechanisms. The Crew Dragon spacecraft, operated by SpaceX under NASA's Commercial Crew Program, features a PICA-X ablative heat shield for atmospheric entry protection and deploys drogue followed by main parachutes for splashdown recovery in the ocean, enabling multiple missions per vehicle with refurbishment between flights. Cargo variants like Cargo Dragon similarly employ heat shields and parachutes, allowing the return of up to 3,000 kg of material from orbit while prioritizing structural integrity for reuse. These designs emphasize autonomous navigation and attitude control during reentry to ensure safe landing zones.[34][35] Orbital mechanics play a pivotal role in reusable upper stage and spacecraft operations, necessitating careful propellant allocation to balance payload delivery with return capabilities. Stages must retain reserves—typically around 1-2% of total propellant—for deorbit burns that lower perigee into the atmosphere, followed by additional margins for entry corrections and landing propulsion to counteract gravitational and aerodynamic forces, as in Starship's case with approximately 14 metric tons reserved. In the case of Starship, these reserves support not only direct reentry from LEO but also extended missions requiring orbital maneuvers, ensuring the vehicle achieves the necessary velocity reductions without compromising mission objectives. Such allocations are derived from trajectory optimization models that account for delta-v requirements, typically ranging from 100-200 m/s for deorbit and landing in reusable configurations.[36][33][37] Integration challenges for reusable upper stages and spacecraft arise from the need to interface with orbital infrastructure, such as docking ports or refueling depots, while maintaining autonomy for return. For LEO operations, systems like Crew Dragon demonstrate reliable autonomous docking to the International Space Station using laser-based sensors and thrusters, followed by undocking and independent reentry trajectories. In higher orbits like geostationary Earth orbit (GEO), challenges intensify due to greater delta-v demands for deorbit, often requiring precise rendezvous for propellant transfer or capture by servicing vehicles, as conceptualized in Starship's in-orbit refueling architecture that involves multiple tanker flights to enable return from deep space trajectories. These operations demand advanced guidance algorithms to handle relative motion and collision avoidance, with ongoing demonstrations achieving full autonomy in recent tests.[34][38]Reentry Technologies
Atmospheric Entry Methods
Atmospheric entry for reusable launch vehicles begins with the vehicle's deorbit from orbital velocities, typically around 7.8 km/s for low Earth orbit, where aerodynamic forces in the upper atmosphere initiate deceleration.[39] As the vehicle descends, it encounters hypersonic flow regimes above Mach 5, characterized by strong shock waves that compress and heat the surrounding air to temperatures exceeding 10,000 K, leading to dissociation of molecules like O₂ and N₂.[40] This heating causes ionization of air species, forming a plasma sheath around the vehicle—a low-density ionized layer that can attenuate radio signals and complicate communications during peak heating phases between approximately 100 km and 40 km altitude.[41] The primary deceleration occurs through atmospheric drag, reducing velocity from hypersonic to subsonic speeds (below Mach 1, or roughly 0.3 km/s at sea level) over altitudes from 120 km to 10 km, with peak dynamic pressure and heating concentrated in the 80-50 km range.[40] Reentry trajectories are broadly classified into ballistic and lifting types, each influencing the vehicle's range, heating profile, and control requirements. Ballistic reentry follows a near-parabolic path with negligible lift, relying solely on drag for deceleration, which results in a steep entry angle (typically 1-2 degrees) and concentrated heating over a shorter downrange distance of about 1,000-2,000 km.[42] In contrast, lifting reentry employs vehicles with lift-to-drag ratios (L/D) of 0.3 to 3, using controlled angle of attack—often 30-60 degrees—to generate lift that extends the trajectory, allowing cross-range capabilities up to 5,000 km and more gradual deceleration to manage peak loads.[43] Angle of attack adjustments, combined with bank angle modulation (rolling the vehicle to vector lift), enable trajectory shaping to avoid excessive heating or g-forces while targeting specific landing sites.[44] Guidance during atmospheric entry ensures the vehicle remains within a narrow entry corridor, typically 100-200 km wide, to prevent skip-out to space or excessive atmospheric loading. Modern systems integrate GPS for real-time position and velocity updates, providing accuracy to within 10 meters even through partial plasma attenuation, supplemented by inertial measurement units (IMUs) for attitude determination.[45] Reaction control systems (RCS), consisting of small thrusters firing hydrazine or cold gas, provide fine attitude corrections—up to 5-10 degrees per second—essential for maintaining bank angles and angle of attack in the hypersonic phase where aerodynamic surfaces are ineffective due to low dynamic pressure.[46] These guidance algorithms, often predictive and adaptive, continuously solve for optimal control inputs to minimize cross-track errors and fuel use.[47] The fundamental equation governing deceleration is the aerodynamic drag force: F_d = \frac{1}{2} \rho v^2 C_d A where \rho is atmospheric density, v is vehicle velocity, C_d is the drag coefficient (typically 0.5-1.5 for reentry shapes), and A is the reference area. This equation derives from the conservation of momentum in fluid dynamics: the force equals the rate at which momentum is imparted to the airflow, approximated as half the dynamic pressure \frac{1}{2} \rho v^2 times the effective area C_d A, validated through wind tunnel and flight data for hypersonic regimes.[48] For reusable vehicles, the ballistic coefficient \beta = \frac{m}{C_d A} (with m as mass) quantifies entry harshness; lower \beta (e.g., 100-300 kg/m²) enables higher-altitude deceleration, reducing peak heating by 20-50% compared to higher-\beta ballistic capsules, thus supporting reusability through gentler trajectories.[48] By modulating C_d via shape or angle of attack, reusables optimize F_d to achieve controlled energy dissipation over extended paths.[49]Thermal Protection Systems
Thermal protection systems (TPS) are critical for reusable launch vehicles, shielding the structure from the intense aerodynamic heating encountered during atmospheric reentry while enabling multiple flights with minimal refurbishment. Unlike single-use ablative systems that erode away to dissipate heat, reusable TPS prioritize durability, low mass, and rapid turnaround to support economic viability. These systems must withstand extreme conditions without significant degradation, balancing thermal insulation, structural integrity, and manufacturability.[50][51] Reentry heating arises primarily from the compression of atmospheric gases in the vehicle's shock layer, generating convective heat fluxes, alongside radiative heating from the hot plasma. Peak surface temperatures can reach up to 3,000°F (1,650°C) for typical orbital reentries, though steeper trajectories or higher velocities may push localized hotspots toward 2,000°C or more. This heating profile influences TPS selection, with windward surfaces facing the highest loads and leeward areas requiring lighter protection. Historical ablative TPS, such as those used in the Apollo program, relied on charring materials like phenolic resins but were not designed for reuse.[52][50] Reusable TPS materials fall into two broad categories: passive insulators and active cooling systems. Passive reusable systems include ceramic-based options like reinforced carbon-carbon (RCC) composites for leading edges, which endure temperatures up to 1,650°C through oxidation-resistant coatings, and silica or alumina tiles that provide low-conductivity insulation for body flaps and undersides. Metallic TPS, such as Inconel or titanium panels with insulation blankets, offer robustness for moderate heating zones up to 1,100–1,800°F, supporting attach hardware and reducing maintenance needs. Advanced concepts incorporate heat pipes—evaporative devices that redistribute heat via capillary action—to maintain uniform temperatures in metallic structures, preventing hotspots during reentry.[53][54][55] Active cooling methods, like transpiration cooling, enhance reusability by injecting coolant through porous walls to form a protective boundary layer, potentially reducing surface temperatures by 50% or more compared to passive systems. This approach uses materials such as sintered metals or ceramics permeated with cryogenics from the vehicle's tanks, enabling higher heat flux tolerance for hypersonic reentries. While still in development, transpiration systems promise 100+ flight lifecycles with minimal mass penalties.[56][57] Reusability-specific innovations focus on multi-mission durability, such as ablative-reusable hybrids like PICA-X, a phenolic-impregnated carbon ablator variant that chars minimally and allows selective tile reuse after inspection. For SpaceX's Starship, the TPS combines thousands of hexagonal ceramic tiles for the windward side, capable of withstanding 1,400–1,600°C, with ablative blankets underneath; ongoing iterations in 2025 continue to address tile adhesion and ablation resistance challenges for rapid refurbishment, targeting 10–100 flights per set. Recent test flights, including Flights 10 and 11 in August and October 2025, demonstrated survival through reentry heating but highlighted issues like tile loss and heat seepage through gaps.[58][33][59][60] Similarly, NASA's Toughened Uni-piece Fibrous Refractory Oxidation-resistant Composite (TUFROC) offers a reusable alternative for leading edges, integrating fibrous insulation with ceramic coatings for 20+ reuses under 1,650°C conditions. These adaptations reduce replacement costs by emphasizing inspect-and-repair protocols over full overhauls.[61] Validation of TPS performance relies on ground-based arc jet facilities and in-flight data to refine thermal models. NASA's Ames Arc Jet Complex simulates reentry environments with plasma flows up to 10 MW/m² enthalpy, testing material recession, temperature gradients, and structural response on instrumented samples. These tests, combined with telemetry from vehicles like the Space Shuttle or Starship prototypes, enable predictive simulations that correlate heat flux to ablation rates or insulation integrity, ensuring reliability across flight profiles. Over 1,000 arc jet runs have qualified systems like Orion's TPS, confirming multi-flight margins.[62][63][64]Landing and Recovery Systems
Vertical Landing Techniques
Vertical landing techniques for reusable launch vehicles rely on propulsion-based descents to achieve precise, controlled touchdowns after atmospheric reentry. These methods involve a powered descent phase where engines are relighted in the atmosphere to decelerate the vehicle from high velocities, typically using a "hoverslam" or suicide burn maneuver. In this approach, the booster free-falls under gravity until the final moments, at which point the engines ignite to rapidly reduce velocity to near zero just above the surface, avoiding the need for prolonged hovering that would consume additional propellant. Throttle control plays a critical role in the terminal phase, allowing engines to modulate thrust for a soft touchdown, with descent rates managed to achieve minimal vertical velocity at contact.[65] Propellant management is essential for these techniques, as reserves must be allocated specifically for the landing burn without compromising ascent performance. Typically, 5-10% of the first-stage propellant is reserved for recovery operations, including reentry and landing burns; for example, studies indicate about 5.6% for the reentry burn and 1.2% for the landing burn in representative configurations.[66] This allocation ensures sufficient delta-v for reentry and landing while minimizing mass penalties, with the exact reserve optimized based on trajectory and vehicle mass.[67] Control systems enable stability during the descent, primarily through gimbaled engines that provide thrust vector control for attitude adjustments and trajectory corrections. Software algorithms, often employing model predictive control or optimal guidance laws, integrate sensor data to execute the hoverslam profile, countering aerodynamic disturbances and ensuring precise alignment. For instance, the Falcon 9 booster uses its central Merlin engine with gimbal actuation and throttling capabilities ranging from 40% to 100% thrust to maintain stability and achieve controlled deceleration.[68] Success metrics for vertical landings emphasize touchdown accuracy and operational reliability, with modern systems achieving positional errors under 10 meters on landing pads or droneships.[65] As of November 2025, Falcon 9 boosters have achieved 518 successful landings with an overall success rate of about 97.5%, and individual boosters have flown up to 31 times, enabling rapid turnaround and cost reductions.Horizontal and Alternative Landing Methods
Horizontal landing methods for reusable launch vehicles typically employ winged or lifting-body configurations that utilize aerodynamic lift and drag during reentry and descent to enable a controlled glide to a runway. These systems, exemplified by the Space Shuttle Orbiter, rely on control surfaces such as elevons, rudders, and speed brakes to modulate trajectory and attitude, achieving precision landings on conventional runways with touchdown speeds around 350 km/h. The Space Shuttle's design featured a hypersonic lift-to-drag (L/D) ratio of approximately 1 during initial reentry, transitioning to a subsonic L/D of about 4.5, which allowed for cross-range capabilities of up to 2,000 km and energy management through bank-angle adjustments up to 80 degrees.[69] Modern examples, such as Sierra Space's Dream Chaser spaceplane, build on this approach with a lifting-body shape optimized for unpowered horizontal landings, incorporating composite materials for reusability over 15+ missions while minimizing thermal stress through a lower reentry angle.[70] Alternative passive recovery methods, including parachutes and airbags, are employed for capsules or stages lacking propulsion for powered descent, prioritizing simplicity and lower mass penalties over precision. Parachute systems typically deploy in sequence: a drogue parachute stabilizes and decelerates the vehicle post-reentry, followed by main parachutes that reduce terminal velocity to 5-7 m/s for splashdown or land impact.[71] NASA's Orion crew module, for instance, uses three main parachutes capable of withstanding the failure of one, achieving a descent rate under 6 m/s even in off-nominal conditions, with mortar-fired deployment from the heat shield apex.[71] For terrestrial landings, airbag systems attenuate impact loads; Orion's configuration includes six venting airbags that inflate to cushion a 7.6 m/s vertical touchdown, absorbing energy through controlled deflation and reducing g-forces to below 4 g for crew safety.[72] Aerostatic recovery concepts, such as helicopter capture, target upper stages or boosters by combining parachutes with mid-air apprehension to avoid ocean exposure and enable rapid refurbishment. In this method, a parachute lowers the stage to 1-2 km altitude, where a helicopter uses a hook or line to snag the parachute risers, suspending the payload for transport to shore.[73] Rocket Lab demonstrated this in 2022 with its Electron booster, successfully capturing an inert stage mid-air before controlled release into the ocean, highlighting the technique's potential for lightweight vehicles under 1,000 kg dry mass.[74] Balloon-assisted variants, though less operational, have been explored for gentler descents of small upper stages, using buoyant platforms to slow descent rates to under 1 m/s, but remain conceptual due to deployment complexities.[75] These non-vertical methods offer trade-offs favoring reduced propellant reserves—potentially saving 5-10% of vehicle mass compared to vertical propulsion—but introduce higher refurbishment demands from aerodynamic heating and structural wear on delicate wings or parachutes.[76] Horizontal approaches excel in precision (errors under 1 km) and reusability for crewed vehicles but incur a 15-20% payload penalty from added mass, while parachute systems simplify integration for upper stages at the cost of variable landing sites and post-flight drying.[77] Overall, they complement vertical techniques by suiting configurations where fuel efficiency trumps pinpoint accuracy.[76]Design and Operational Constraints
Mass and Structural Penalties
Reusable launch vehicles require additional hardware for recovery and reentry, including landing legs, grid fins for aerodynamic control, and heat shields for thermal protection, which collectively increase the dry mass by approximately 10-20%. For instance, the mass of landing gear such as legs and grid fins can raise the first-stage dry mass by 15%. These components are essential for enabling controlled descent and landing but impose a direct penalty on overall vehicle efficiency.[78][79] This added mass fraction, often denoted as \Delta m_{\text{reuse}} / m_{\text{total}} \approx 0.15, reduces the payload capacity to low Earth orbit (LEO) by decreasing the effective \Delta v budget according to the Tsiolkovsky rocket equation: \Delta v = v_e \ln \left( \frac{m_0}{m_f} \right), where v_e is exhaust velocity, m_0 is initial mass, and m_f is final mass after burnout; the reusability hardware increases m_f, thereby lowering the achievable payload mass. Quantitative assessments indicate payload reductions of up to 50% compared to equivalent expendable vehicles, as seen in reusable two-stage-to-orbit designs where first-stage inert weight rises by 10% and upper-stage by 20%, compounded by reserved propellants for return.[36][78] To endure repeated launch, ascent, reentry, and landing cycles, structural reinforcements incorporate fatigue-resistant materials such as aluminum-lithium (Al-Li) alloys, which offer superior strength-to-weight ratios and improved cryogenic performance over traditional aluminum alloys. These materials, like alloy 2195, enable thinner walls and higher load capacities while mitigating crack propagation under cyclic stresses.[80][81] Mitigation strategies focus on lightweight composites, such as graphite-epoxy for propellant tanks, which can achieve 20-40% mass savings relative to metallic structures, and optimized geometries via advanced manufacturing like friction stir welding for Al-Li components. By 2025, these approaches, including carbon-fiber reinforced plastics and refined finite element sizing, have minimized overall vehicle mass penalties to as low as 4% in innovative designs through targeted structural enhancements.[80][82]Refurbishment and Reliability Issues
The refurbishment process for reusable launch vehicles begins immediately after recovery, involving a structured workflow of inspection, testing, and maintenance to prepare the hardware for subsequent flights. Non-destructive testing techniques, such as ultrasonic inspections and radiographic evaluations, are employed to assess structural integrity without damaging components, allowing operators to identify potential issues like cracks or material fatigue. Component replacement occurs as needed, with high-wear elements like certain engine parts or thermal protection tiles swapped out; for instance, Merlin engines on the Falcon 9 undergo detailed post-flight analysis and refurbishment at dedicated facilities, with full engine replacements typically required after approximately 10 flights to maintain performance standards.[25][83][84] Turnaround times for refurbished boosters have significantly shortened, enabling rapid reuse cycles that typically span days to weeks. SpaceX's Falcon 9 has achieved turnaround times as low as 2 days between flights for select boosters as of late 2025, facilitated by streamlined processes at launch sites and dedicated refurbishment facilities in Texas and California. This workflow culminates in recertification through static fire tests and system checks to verify operational readiness, ensuring the vehicle meets flight safety criteria before relaunch.[85][86] Reliability remains a core focus, with refurbished vehicles demonstrating exceptional performance metrics. Falcon 9 first-stage boosters have achieved over 497 successful re-flights as of November 2025, with a near-100% mission success rate for reflown hardware—though one reused booster (B1086) was lost post-landing in March 2025—contributing to an overall program reliability exceeding 99% across hundreds of missions. Industry targets for failure rates in reusable systems aim for less than 1% per flight, a threshold met through rigorous post-recovery validation and redundancy in critical systems like propulsion.[25][85][87][88] Key challenges in refurbishment stem from cumulative wear due to repeated thermal cycles during reentry and high-frequency vibrations from launch and landing, which can accelerate material degradation in engines and structural elements. To address these, predictive maintenance strategies incorporating AI-driven analytics are increasingly utilized to forecast component lifespans and prioritize interventions, minimizing downtime and enhancing long-term reliability.[89][90] Economically, refurbishment balances upfront hardware savings—estimated at up to 70% reduction in launch costs through reuse—against ongoing expenses for labor, specialized facilities, and testing. For SpaceX, these operational costs have been optimized to under 10% of new booster production expenses, supporting high launch cadences while recouping investments via repeated missions.[91][25]Historical Development
Early Concepts and 20th-Century Efforts
The concept of reusable launch vehicles emerged in the early 20th century amid foundational rocketry theories. Russian scientist Konstantin Tsiolkovsky, often regarded as a father of astronautics, along with Friedrich Tsander, proposed early ideas for winged reusable spacecraft capable of reaching orbit and returning to Earth, emphasizing recovery to enable sustained space exploration.[92] These visions built on Tsiolkovsky's 1903 rocket equation and his 1929 multistage rocket proposals, which laid groundwork for efficient propulsion but highlighted the need for recoverable designs to reduce costs.[93] In the mid-20th century, German-American engineer Wernher von Braun advanced reusable rocket concepts through popular media and technical studies. In a 1952 Collier's magazine series, von Braun described a three-stage "Ferry Rocket" system for transporting crews and cargo to orbit, featuring recoverable upper stages with winged reentry vehicles to enable routine spaceflight.[94] His designs, illustrated by artist Chesley Bonestell, influenced public and military interest in reusability, including proposals for recoverable boosters in Walt Disney's 1955 Man in Space television program, which reached over 40 million viewers.[95] However, these ideas relied on unproven materials and propulsion, remaining largely conceptual amid the Cold War focus on ballistic missiles. Soviet efforts in reusable systems culminated in the Buran program during the 1970s and 1980s, driven by competition with the U.S. Space Shuttle. Buran, an orbiter launched atop the expendable Energia rocket, achieved its maiden unmanned orbital flight on November 15, 1988, completing two orbits before an automated runway landing, demonstrating partial reusability through its recoverable airframe and thermal protection.[96] The program, which traced roots to 1960s prototypes like the MiG-105 and Spiral, aimed for 10 planned flights but was curtailed by economic pressures and the USSR's dissolution in 1991, with only one flight executed.[97] U.S. programs in the 1990s pursued practical demonstrations of reusability. The Delta Clipper Experimental (DC-X), a suborbital prototype developed by McDonnell Douglas under DARPA's Ballistic Missile Defense Organization (later transferred to NASA), conducted 12 vertical takeoff and landing tests, of which 8 were successful, between 1993 and 1996 at White Sands, validating rapid reusability, cryogenic tank integrity, and autonomous control for single-stage vehicles.[52] Building on this, NASA's X-33 program, partnered with Lockheed Martin from 1996, sought to prove all-composite structures for a reusable single-stage-to-orbit vehicle under the VentureStar concept, investing $912 million by 2001 but canceling the effort due to persistent failures in the composite liquid hydrogen tank, such as leaks during cryogenic testing.[98] Throughout the 20th century, technological limitations hindered widespread adoption of reusable launch vehicles, favoring expendable designs. Materials challenges, including insufficient high-temperature tolerance in composites (limited to ~600°F) and superalloys prone to oxidation and creep at reentry heats exceeding 1800°F, demanded extensive development absent in the post-Apollo era.[99] Structural issues, such as cryogenic tank durability for repeated cycles and thermal protection systems vulnerable to gap heating, compounded costs and risks. Additionally, computing constraints restricted precise real-time control for reentry and landing, with early avionics lacking the processing power for dynamic stability in reusable engines, as seen in the need for advanced fault-tolerant systems only emerging later.[100] These barriers, coupled with high development expenses, entrenched expendable rockets as the dominant paradigm until the century's end.21st-Century Advancements and Operational Systems
The 21st century marked a pivotal shift in reusable launch vehicle development, driven primarily by private sector innovation and government partnerships, transitioning from experimental prototypes to operational systems capable of routine flights. SpaceX led this resurgence with its Grasshopper test vehicle, a suborbital prototype that demonstrated vertical takeoff and landing (VTVL) capabilities through a series of hops in 2013, reaching altitudes of up to 744 meters during its final test on October 7. These tests validated propulsion and control systems essential for booster recovery, paving the way for orbital applications. Building on this foundation, SpaceX achieved a historic milestone on December 21, 2015, with the first successful return-to-launch-site (RTLS) landing of a Falcon 9 first-stage booster following an orbital payload deployment, enabling the vehicle's reuse on subsequent missions. By October 2025, SpaceX had recorded over 500 successful Falcon 9 booster landings, with individual boosters achieving up to 31 flights and many flying more than 20 times, establishing reusability as a core operational practice that supported high-cadence launches. Other private entities contributed to suborbital and conceptual advancements, while NASA facilitated crewed reuse. Blue Origin's New Shepard, a fully reusable suborbital system, completed its first powered booster landing on November 23, 2015, during an uncrewed test flight reaching 100 kilometers altitude, and has since flown 36 missions by October 2025, including multiple crewed space tourism flights with rapid turnaround times between reuses. United Launch Alliance (ULA) explored partial reusability for its Vulcan Centaur rocket, announcing in August 2025 progress on recovering the BE-4 engine section to lower costs, though operational demonstrations remain in development. NASA's Commercial Crew Program played a crucial role by certifying SpaceX's Crew Dragon spacecraft for reuse in June 2020, allowing the capsule to fly multiple astronaut missions to the International Space Station starting with Crew-2 in 2021, thereby integrating human-rated reusability into U.S. spaceflight operations. Key milestones in scaling reusability included SpaceX's Starship program, which began prototype testing in 2019 with suborbital hops and evolved to full-stack orbital attempts by 2023, achieving six successful integrated flights by October 2025 despite early challenges like stage separations and reentry. These efforts addressed prior design constraints through iterative improvements in materials and software, enabling rapid prototyping at Starbase, Texas. Overall, reusability drove substantial cost reductions; for instance, Falcon 9 launches dropped to approximately $67 million per flight by 2025, compared to over $200 million for comparable expendable systems a decade earlier, primarily due to booster refurbishment efficiencies and amortized development. This economic impact has democratized access to space, supporting constellations like Starlink and fostering a competitive launch market.Key Operational Techniques
Powered Return to Launch Site
The Powered Return to Launch Site (RTLS) maneuver enables the first stage of a reusable launch vehicle to return directly to the originating launch pad or an adjacent landing zone following separation from the upper stage. This technique is particularly suited for missions with lower energy requirements, such as low Earth orbit insertions, where the booster does not travel far downrange. The process relies on vertical takeoff, vertical landing (VTVL) principles, adapted for site-specific recovery. The maneuver sequence commences immediately after stage separation, typically at altitudes around 70-80 km and velocities of approximately 2 km/s. The boost-back burn involves reigniting a subset of the first-stage engines—often three out of nine for systems like the Falcon 9—to reverse the booster's horizontal velocity and arc its trajectory back toward the launch site; this burn lasts about 20-30 seconds and occurs roughly 2-3 minutes post-launch. Following a ballistic coast phase, the reentry burn activates one or more engines for 15-25 seconds at altitudes of 50-70 km to decelerate the vehicle, reducing peak heating and dynamic loads during atmospheric entry, where grid fins provide steering for stability. The sequence culminates in the landing burn, igniting the center engine (or multiple engines in a sequenced pattern) about 30-60 seconds before touchdown to nullify residual velocity, achieving a soft vertical landing with throttle control for precision.[25][101] Fuel budgeting for RTLS demands precise allocation of residual propellant after ascent, reserving margins for the boost-back, reentry, and landing burns while maximizing payload delivery. Compared to downrange recovery, RTLS requires additional propellant specifically for the boost-back burn to counteract downrange momentum, typically necessitating 3-5% more of the first stage's total propellant load to enable the return without compromising upper-stage performance. This reservation, drawn from the overall first-stage capacity of around 400 metric tons for vehicles like the Falcon 9, can reduce mission payload capability by up to 60% relative to expendable profiles, though optimizations in trajectory design mitigate this penalty for suitable missions.[75][25] Achieving RTLS demands stringent precision in navigation and control, with landing tolerances on the order of tens of meters to ensure safe touchdown on concrete pads or zones. Autonomous systems, relying on onboard avionics, GPS receivers, inertial measurement units, and real-time telemetry, handle the entire descent without ground intervention, computing trajectory corrections via algorithms that integrate sensor data for grid fin actuation and engine throttling. SpaceX's Falcon 9 exemplifies this, having completed numerous RTLS landings at Landing Zone 1 near Cape Canaveral with high reliability, leveraging redundant flight computers to manage uncertainties like wind shear or atmospheric variability.[25] Key advantages of RTLS include facilitating rapid turnaround for booster reuse, as the recovered stage remains at the launch site without requiring maritime retrieval or overland transport, thereby streamlining logistics and reducing operational delays. By 2025, this has supported SpaceX's high-cadence launch manifest, with Falcon 9 boosters routinely refurbished and reflown within weeks, contributing to cost savings estimated at over 30% per mission through minimized recovery expenses and enhanced reliability.[25][75]Other Recovery and Reuse Strategies
Downrange recovery strategies extend the operational flexibility of reusable launch vehicles beyond launch-site returns, accommodating missions with heavier payloads that require expending more propellant during ascent. These methods typically involve precision landings on autonomous drone ships positioned hundreds of kilometers offshore or on remote land-based pads, allowing the first stage to achieve higher orbital insertions. For instance, SpaceX's Falcon 9 has executed over 400 successful downrange landings on drone ships as of August 2025, demonstrating the reliability of this approach for geostationary transfer orbit missions.[102] This technique prioritizes payload capacity over immediate site recovery, with the drone ships equipped for stable platform landings in open ocean conditions.[25] Capture methods represent innovative alternatives for recovering lighter components like payload fairings, often using airborne or ship-based systems to minimize water exposure and simplify refurbishment. SpaceX initially tested helicopter-assisted drops of fairing halves into nets aboard fast-moving recovery ships to simulate descent and capture dynamics, gathering data on structural integrity during 2018 trials.[103] Although early attempts at dry net capture were abandoned by 2021 in favor of wet recovery—where fairings splash down under parachutes and are retrieved by ships using cranes or divers— this evolution has enabled routine reuse, with fairing halves re-flown on 307 missions at 100% success rate by February 2025.[104][25] Such techniques highlight the trade-offs in recovery complexity for components not requiring full vertical landing capabilities. Following downrange or capture recovery, transport and return logistics form a critical chain to enable rapid turnaround and multi-site reuse. Recovered boosters are secured vertically on the drone ship's deck using custom fixtures to withstand sea transit, with the vessel then towed or self-propelled back to port over 1-3 days depending on weather and location.[105] Upon arrival, the booster is offloaded via crane onto barges or trucks for horizontal transport to processing facilities, often covering distances between sites like Florida's Cape Canaveral and California's Vandenberg Space Force Base. This global reuse infrastructure, refined through iterative operations, supports booster relocations for optimized launch cadences while adding logistical steps that influence overall refurbishment timelines.[25] Emerging strategies like in-orbit refueling expand reuse paradigms to upper stages and spacecraft, decoupling recovery from Earth return for interplanetary missions. SpaceX's Starship architecture envisions tanker variants launching to low Earth orbit to transfer cryogenic propellants—methane and oxygen—to a dedicated orbital depot or directly to the target vehicle via docking ports and fluid lines. An intervehicular propellant transfer demonstration is planned for 2026, paving the way for full-scale operations, with plans for a Starship-derived depot to be refilled by up to a dozen tankers for lunar missions by 2026.[106][107] This approach enables extended vehicle lifespans without atmospheric reentry penalties, though it demands precise cryogenic management to prevent boil-off.[108]Examples of Reusable Systems
Orbital Launch Vehicles
Orbital launch vehicles represent the core of reusable space access, enabling repeated use of major rocket components to reduce costs and increase launch frequency for missions to low Earth orbit (LEO) and beyond. The pioneering Falcon 9, developed by SpaceX, achieved the first orbital-class first-stage reuse in 2017 and has since become the workhorse of the industry, with over 500 successful booster landings by November 2025, demonstrating a landing success rate exceeding 98% across thousands of attempts. This partial reusability—recovering the first stage via propulsive landing on drone ships or ground pads—has enabled payload capacities of up to 22,800 kg to LEO in reusable configuration, supporting a diverse array of commercial, scientific, and national security missions. Advancements toward full reusability are exemplified by SpaceX's Starship system, which underwent multiple integrated flight tests in 2024 and 2025, including engine reuse and booster catch attempts by late 2025, aiming for rapid turnaround of both stages without refurbishment. While still in developmental testing with 11 flights completed by October 2025, Starship targets 150 metric tons to LEO in fully reusable mode, positioning it as a super heavy-lift vehicle for ambitious goals like satellite constellations and interplanetary transport. European efforts, led by ArianeGroup under the Themis program, are exploring reusable first-stage technologies as an evolution from the expendable Ariane 6, with prototype testing progressing in 2025 to address competitiveness gaps. Emerging players are also advancing reusable orbital systems. Relativity Space's Terran R focuses on 3D-printed manufacturing for rapid production and first-stage recovery, targeting 23,500 kg to LEO in reusable mode with a maiden flight anticipated in 2026. Similarly, Rocket Lab's Neutron medium-lift rocket plans sea-based first-stage landings, offering 13,000–15,000 kg to LEO reusable, with its debut launch scheduled for 2026.[109]| Vehicle | Operator | Reuse Type | First Reuse Date | Notes |
|---|---|---|---|---|
| Falcon 9/Heavy | SpaceX | First stage (propulsive landing) | 2017 | Over 500 successful landings by November 2025; 99%+ recovery success rate; 22,800 kg to LEO reusable for Falcon 9, 26,700 kg for Heavy sides/center core. |
| Starship | SpaceX | Full stack (both stages, tower catch for booster) | 2025 (test flights) | 11 integrated tests by October 2025; advancing to operational full reuse; 150 t to LEO reusable. |
| Themis (Ariane evolution) | ArianeGroup/ESA | First stage partial reusability | Developmental (2025 prototypes) | Testing reusable booster tech for Ariane 6 successor; aims for cost reduction; payload TBD. |
| Terran R | Relativity Space | First stage (propulsive) | Planned 2026+ | In advanced development with 50%+ design release by mid-2025; 23,500 kg to LEO reusable. |
| Neutron | Rocket Lab | First stage (sea landing) | Planned 2026+ | First launch in 2026; 13,000–15,000 kg to LEO reusable; focuses on constellation deployments. |
Reusable Spacecraft
Reusable orbital spacecraft represent a critical advancement in space transportation, enabling repeated missions to low Earth orbit for crewed and cargo delivery while reducing costs through refurbishment and relaunch. These vehicles, distinct from launch systems, focus on orbital operations, docking, and safe return, primarily serving the International Space Station (ISS) for human spaceflight and logistics. Key examples include capsules and spaceplanes designed for multiple flights, with reentry methods like parachutes or gliding optimized for structural integrity and rapid turnaround. The Crew Dragon, developed by SpaceX in partnership with NASA under the Commercial Crew Program, is a crewed and cargo-capable capsule that has achieved operational reusability since 2020. It supports up to seven astronauts or equivalent cargo, docking autonomously to the ISS for crew rotations and resupply missions. As of November 2025, the most-flown Crew Dragon capsules, such as Endeavour, have completed up to 7 reuses, with NASA and SpaceX extending the design life to 15 missions per vehicle through rigorous post-flight inspections and component replacements. Reusability is enhanced by its heat shield, which withstands multiple reentries, and landing via four main parachutes that deploy sequentially for a soft ocean splashdown, allowing recovery and refurbishment within months. Key missions include Demo-2 (first crewed flight in 2020), ongoing NASA Crew rotations (e.g., Crew-8 in 2024 and Crew-9 in 2025), and private Axiom Space missions to the ISS.[85][110] Sierra Space's Dream Chaser is an uncrewed cargo spaceplane designed as a lifting-body glider for ISS resupply, emphasizing rapid reusability with a planned lifespan of 15 or more missions per vehicle. It carries up to 5,500 kg of pressurized and unpressurized cargo, launching atop a Vulcan Centaur rocket and returning via runway landing to facilitate quick turnaround without ocean recovery logistics. As of November 2025, the vehicle remains in development, with its inaugural free-flyer demonstration mission delayed to late 2026 due to integration challenges and NASA contract modifications; it will initially operate without ISS docking to validate reusability features. The glider's winged design enables precise horizontal landings on runways like Kennedy Space Center's Shuttle Landing Facility, tying reusability to minimal wear on aerodynamic surfaces. Future roles include ISS cargo delivery under NASA's Commercial Resupply Services program.[111][112][113] Boeing's CST-100 Starliner, also part of NASA's Commercial Crew Program, is a crewed capsule intended for up to seven astronauts, with the crew module designed for reusability up to 10 flights and a six-month turnaround. It features autonomous docking to the ISS and lands via three main parachutes for splashdown or airbag-assisted ground landing, supporting crew transport and potential cargo roles. As of November 2025, Starliner has not achieved operational reusability due to ongoing certification delays from thruster and helium leak issues during its 2024 crewed test flight (Crew Flight Test), with the next uncrewed flight targeted for early 2026; the service module remains expendable. Despite challenges, NASA maintains plans for Starliner to complement Crew Dragon in ISS crew rotations once certified.[114][115][116]| Spacecraft | Operator | Reuse Flights (as of Nov 2025) | Key Missions |
|---|---|---|---|
| Crew Dragon | SpaceX/NASA | Up to 7 per capsule | ISS Crew rotations (Crew-1 to Crew-9), Axiom-1 to Axiom-4 |
| Dream Chaser | Sierra Space | Planned 15+ (not yet flown) | Planned ISS cargo resupply (CRS-33+), free-flyer demo 2026 |
| Starliner | Boeing/NASA | Planned 10 (not yet achieved) | Crew Flight Test (2024), planned OFT-2 (2026) |
Suborbital and Test Vehicles
Suborbital and test vehicles play a pivotal role in advancing reusable launch technologies by enabling controlled experiments with vertical propulsion, landing systems, and recovery processes in environments below orbital velocity. These platforms focus on short-duration missions, such as low-altitude hops and high-altitude suborbital trajectories, to validate design iterations, reduce development risks, and gather data on material stresses and control algorithms without the need for full orbital infrastructure. By iteratively testing reusability elements like engine relights and autonomous guidance, they serve as foundational steps toward scalable orbital systems. Blue Origin's New Shepard exemplifies a mature suborbital reusable vehicle, consisting of a single-stage liquid hydrogen/oxygen booster and a crew capsule for tourism and scientific payloads. Launched vertically from West Texas, the system reaches approximately 100 km altitude before the booster performs a powered descent and landing near the pad, while the capsule deploys parachutes for a soft touchdown. This configuration has enabled rapid reuse cycles, with minimal refurbishment between flights. As of November 2025, New Shepard has achieved 36 successful missions, including crewed flights carrying 86 humans, demonstrating reliable suborbital reusability through repeated vertical landings and booster reflights. A key milestone includes sustaining operations with the same hardware fleet across multiple years, contributing to cost reductions in access to space.[120][121] SpaceX's Starship prototypes, particularly the SN series (SN8 through SN15), conducted essential suborbital hop tests from 2020 to 2021 at the Boca Chica facility in Texas to refine reusability features for the larger Starship system. These stainless-steel prototypes, powered by Raptor engines, performed controlled ascents to altitudes of 6–12 km, followed by flip maneuvers, atmospheric reentry simulations, and propulsive landings to test grid fin stability and engine throttling. While early attempts (SN8–SN14) resulted in hard landings or explosions that provided critical failure data, SN15 achieved the first successful high-altitude landing in May 2021, validating the belly-flop and catch-up burn techniques central to vertical reusability. These tests, though not involving hardware reuse themselves, established empirical foundations for subsequent prototypes and full-stack flights.[122][123] Rocket Lab's Electron rocket incorporates reusability trials focused on its first stage and kick stage (the Photon upper stage), aimed at enabling economical small satellite launches. The carbon-composite first stage uses electric pump-fed Rutherford engines for precise control during descent, with recovery via parachutes and splashdown in the Pacific Ocean. The kick stage, evolved into the Photon spacecraft, supports suborbital payload delivery and has been tested for post-separation recovery to assess refurbishment viability for future missions. As of 2025, Rocket Lab has conducted multiple first-stage recoveries—beginning with intact splashdowns in 2020 and advancing to structural upgrades for potential powered landings—while kick stage trials emphasize orbit insertion and deorbit maneuvers to preserve hardware integrity. These efforts represent incremental progress toward operational reuse in the small-launch market.[124][125] The following table summarizes key suborbital and test vehicles, highlighting their contributions to reusability development:| Vehicle | Operator | Test Type | Reuse Count | Status |
|---|---|---|---|---|
| New Shepard | Blue Origin | Suborbital hops, vertical landings, payload delivery | 36 total flights; boosters reused 5–12 times each | Operational |
| Starship SN series | SpaceX | High-altitude hops, propulsive maneuvers | 0 (prototypes one-time use) | Testing complete; informs ongoing program |
| Electron (kick stage trials) | Rocket Lab | First-stage recovery, upper-stage payload validation | 3+ first-stage recoveries; 0 full reuses | Trials ongoing |