M-V
The M-V, also designated Mu-5, was a three-stage solid-propellant expendable launch vehicle developed by Japan's Institute of Space and Astronautical Science (ISAS, now part of JAXA) as the final iteration in the Mu series for injecting scientific satellites and planetary probes into orbit.[1] Standing 30.7 meters tall with a diameter of 2.5 meters, it featured an optional fourth-stage kick motor for higher-energy trajectories and could deliver payloads of up to 1.8 metric tons to a 250 km low Earth orbit.[2][3]
From its maiden flight in 1997 to its retirement in 2006, the M-V conducted seven launches from the Uchinoura Space Center, achieving six successes and enabling pivotal missions in astronomy and solar system exploration, including the HALCA radio telescope satellite, the Nozomi Mars probe, the groundbreaking Hayabusa asteroid sample-return mission, and X-ray observatories such as Suzaku (ASTRO-E2).[1][4] A single failure occurred during the fourth launch in 2000, when the ASTRO-E satellite was lost due to a first-stage anomaly, but the vehicle's overall precision and reliability in solid-fuel propulsion garnered international recognition as one of the world's premier systems for such scientific endeavors.[1][4] Its discontinuation paved the way for the more cost-efficient Epsilon rocket, reflecting shifts in Japan's space launch strategy toward reduced operational expenses while maintaining capability for small scientific payloads.[4]
Development and Technical Overview
Historical Context and Objectives
The M-V rocket represented the fifth generation in Japan's Mu series of all-solid-propellant launch vehicles, developed by the Institute of Space and Astronautical Science (ISAS, now part of JAXA) as a successor to the M-3SII to meet the escalating requirements of space science missions entering the late 1990s and early 21st century.[5] Building on over a decade of experience with prior Mu rockets, which had enabled observations of cosmic phenomena such as supernovae, aurorae, and Halley's Comet, the M-V aimed to extend ISAS's capabilities into more ambitious astronomical and planetary exploration endeavors.[4] Primary objectives included delivering medium-payload scientific satellites to low Earth orbit with a capacity of up to 1,850 kg to a 250 km sun-synchronous orbit, while achieving an annual launch frequency through cost-effective solid-propellant architecture and streamlined operations.[5] The design prioritized simplicity, leveraging existing facilities at Kagoshima Space Center (formerly Uchinoura Space Center) to minimize development expenses and preparation times, with a focus on advanced materials such as high-tensile HT-230M steel casings, carbon-fiber-reinforced polymer (CFRP) motor structures, and fiber-optic gyroscope (FOG) systems for precise attitude control.[5] Development commenced in the early 1990s, with the first launch occurring on February 12, 1997, successfully deploying the HALCA radio astronomy satellite, followed by the Nozomi Mars probe on July 4, 1998.[6] Over its operational lifespan from 1997 to 2006, the M-V conducted seven launches, supporting four astronomical observation satellites—including Suzaku for X-ray astronomy and Akari for infrared surveys—and two planetary explorers, thereby inaugurating a new phase in Japan's solar system science by enabling deeper investigations beyond Earth orbit.[4] This progression underscored ISAS's commitment to solid-rocket technology for scientific payloads, distinct from the liquid-fueled vehicles pursued by Japan's National Space Development Agency (NASDA) for larger commercial and practical satellites.[2]Design Features and Specifications
The M-V is an all-solid-propellant, three-stage launch vehicle developed by the Institute of Space and Astronautical Science (ISAS), featuring an optional kick stage for high-energy missions such as lunar or planetary trajectories.[7] The vehicle stands 30.8 meters tall, with a diameter of 2.5 meters for the first and second stages and 2.2 meters for the third stage, and a total launch mass of approximately 140 metric tons.[8] Its design emphasizes simplicity, reliability, and cost-effectiveness for scientific payloads, utilizing advanced solid rocket technologies inherited from prior Mu-series rockets.[9] First Stage: Powered by the M-14 solid rocket motor with a case made of HT-230M high-strength steel, it incorporates 72 tons of BP-204J propellant, producing 3,800 kN of thrust over 51 seconds at a specific impulse of 274 seconds. The motor measures 13.73 meters in length and 2.5 meters in diameter, with a stage mass of 138 tons.[7] Second Stage: The M-25 motor, also using HT-230M casing, employs 33 tons of BP-208J propellant for 1,530 kN thrust sustained for 61 seconds, achieving a specific impulse of 289 seconds. It spans 6.61 meters in length and 2.5 meters in diameter, with a stage mass of 52.2 tons.[7] Third Stage: Equipped with the M-34 motor featuring a carbon fiber reinforced plastic (CFRP) case and an extensible nozzle for vacuum optimization, it uses 11 tons of BP-205J propellant to deliver 327 kN thrust for 97 seconds at 300 seconds specific impulse. The motor length varies between 3.61 and 4.29 meters depending on configuration, with a stage mass of 13.1 tons.[7][8] The optional kick stage mirrors the third stage's CFRP construction and extensible nozzle design, enabling precise insertion into elongated or escape orbits.[8] Guidance and attitude control rely on fiber optic gyroscopes (FOG) for high-precision inertial navigation.[9] Separations between stages employ a "fire-in-the-hole" (FIH) system for the first-to-second interstage and flexible linear shaped charge (FLSC) mechanisms elsewhere, while the payload fairing uses a dedicated jettison system.[9] The M-V supports payloads up to 1,800 kg to low Earth orbit, tailored for astronomical and planetary science missions launched from Uchinoura Space Center.[8]Launch Campaigns
Chronological Launch History
The M-V launch vehicle, developed by Japan's Institute of Space and Astronautical Science (ISAS), performed seven flights from Uchinoura Space Center between 1997 and 2006, primarily to deploy scientific satellites and planetary probes into high-energy orbits such as highly elliptical Earth orbits, Earth-escape trajectories, or solar orbits.[1] A planned M-V-2 mission was canceled due to scheduling uncertainties, resulting in the next flight being designated M-V-3.[10] Of these launches, six achieved nominal orbital insertion, while one (M-V-4) failed due to a first-stage nozzle combustion anomaly.[1][4]| Flight No. | Launch Date | Payload | Outcome |
|---|---|---|---|
| M-V-1 | February 12, 1997 | HALCA (MUSES-B) | Success: Deployed into highly elliptical orbit for space very long baseline interferometry.[1] |
| M-V-3 | July 4, 1998 | Nozomi (PLANET-B) | Success: Injected into hyperbolic trajectory toward Mars.[1] |
| M-V-4 | February 10, 2000 | ASTRO-E | Failure: First-stage engine nozzle failure at 41 seconds caused loss of control and underperformance; payload not inserted into orbit.[1][6] |
| M-V-5 | May 9, 2003 | Hayabusa (MUSES-C) | Success: Escaped Earth's gravity toward asteroid Itokawa.[1] |
| M-V-6 | July 10, 2005 | Suzaku (ASTRO-E II) | Success: Inserted into low Earth orbit for X-ray astronomy (replacement for lost ASTRO-E).[1][11] |
| M-V-7 | February 22, 2006 | AKARI (ASTRO-F) | Success: Placed into Sun-synchronous orbit for infrared astronomy.[1] |
| M-V-8 | September 23, 2006 | Hinode (SOLAR-B) | Success: Achieved Sun-synchronous orbit for solar observation.[1][12] |
Performance Outcomes and Reliability
The M-V rocket executed seven launches from February 12, 1997, to September 23, 2006, achieving six full successes in orbital insertion and one partial failure, yielding a success rate of 86 percent.[5][1] These outcomes demonstrated reliable performance for a solid-propellant launch vehicle designed for small scientific payloads, with all successful missions delivering satellites to their intended orbits despite the technology's inherent challenges in scalability and precision control.[5] The sole failure occurred on the fourth launch, M-V No. 4, on February 10, 2000, which carried the Astro-E X-ray observatory; a first-stage engine nozzle malfunction caused combustion instability, resulting in underperformance and failure to achieve orbital velocity, though the payload separated intact.[1][3] Post-failure investigations by the Institute of Space and Astronautical Science (ISAS) identified material and manufacturing issues in the nozzle, leading to design refinements in subsequent stages, including enhanced quality controls and redundancy in propulsion components.[1] This incident, while highlighting early reliability vulnerabilities in Japan's small-rocket program, did not recur, as the final three launches (M-V No. 5 through No. 7b) operated without anomalies.[5] Reliability improved progressively, with the initial three launches (Nos. 1, 3, and the failed No. 4) reflecting a 67 percent success rate amid developmental teething issues, contrasted by 100 percent success in the later four flights following corrective actions.[5][1] Overall, the program's track record supported its role in enabling precise, low-cost access to sun-synchronous and other specialized orbits, though the single failure underscored limitations in solid-rocket ignition and thrust vectoring compared to liquid-fueled alternatives.[3] No systemic patterns of failure emerged beyond the isolated nozzle event, affirming the M-V's operational maturity by program end.[5]Scientific Contributions
Major Payloads and Missions
The M-V rocket primarily deployed scientific satellites for astronomical observations and interplanetary exploration, enabling Japan's Institute of Space and Astronautical Science (ISAS, now part of JAXA) to conduct high-precision studies of cosmic phenomena and solar system bodies. Successful missions included four dedicated astronomical payloads and two planetary probes, with launches occurring between 1997 and 2006 from Uchinoura Space Center. These payloads leveraged the rocket's capability to deliver up to 1,850 kg to low Earth orbit or 550 kg to a heliocentric trajectory, supporting instruments requiring stable, vibration-minimized environments for sensitive optics and detectors.[5][1] HALCA (Highly Advanced Laboratory for Communications and Astronomy, also known as MUSES-B), launched on February 12, 1997, via M-V-1, was the world's first space-based very long baseline interferometry (VLBI) satellite. Equipped with an 8-meter deployable antenna, it operated in a highly elliptical orbit to correlate radio signals with ground telescopes, achieving resolutions down to 0.7 milliarcseconds for imaging quasars, active galactic nuclei, and supernova remnants—ten times finer than ground-based VLBI alone. The mission collected data until oxygen depletion in 1999 and hydrogen issues in 2003, yielding breakthroughs in understanding relativistic jets and compact radio sources.[14][15] Nozomi (Planet-B), launched on July 4, 1998, aboard M-V-3 (or M-V-2 per some records), aimed to orbit Mars for atmospheric and magnetospheric studies using plasma analyzers, ion mass spectrometers, and cameras. Massing 540 kg, it encountered thruster valve failures and fuel leaks during Earth swing-bys, preventing Mars orbit insertion; it conducted partial remote sensing before burning up in Mars' atmosphere on December 9, 2003. Despite operational shortfalls, the launch validated M-V's interplanetary injection accuracy.[16][17] Hayabusa (MUSES-C), deployed on May 9, 2003, by M-V-5, was a 510 kg asteroid rendezvous mission targeting sample return from near-Earth asteroid Itokawa. It demonstrated ion propulsion for trajectory corrections, autonomous optical navigation, and micro-sampling via a bullet-like projectile, touching down in September 2005 despite challenges like failed sampler horns and solar panel damage from micrometeoroids. The re-entry capsule returned to Australia on June 13, 2010, containing over 1,500 microscopic particles confirmed as asteroid regolith—the first such extraterrestrial sample return—providing insights into S-type asteroid composition and formation.[18][19] Suzaku (Astro-E2), launched July 10, 2005, on M-V-6, was a 1,700 kg X-ray astronomy observatory replacing the failed Astro-E (lost in the February 10, 2000, M-V-4 launch failure). Its four X-ray Imaging Spectrometers and X-ray Spectrometer enabled high-resolution spectroscopy of black hole accretion disks, galaxy clusters, and supernova remnants, detecting diffuse emission and spectral lines indicative of plasma dynamics. Operational until mid-2015, it contributed data on over 1,000 sources, advancing models of high-energy astrophysics.[20][21] Hinode (Solar-B), launched September 22, 2006, via M-V-8, focused on solar magnetic activity with a 1,400 kg payload including the Solar Optical Telescope (resolution 0.2 arcseconds), X-ray Telescope, and Extreme Ultraviolet Imaging Spectrometer. It orbited in a sun-synchronous path to study sunspots, flares, and coronal mass ejections, revealing dynamic reconnection events and magnetic field evolutions. The mission continued observations beyond its planned five years, aiding space weather forecasting and solar physics until at least 2020.[1][5]Impacts on Astronomy and Space Exploration
The M-V rocket facilitated key advancements in X-ray, infrared, and solar astronomy through precise launches of specialized satellites into high-inclination orbits, enabling long-duration observations of cosmic phenomena.[5] Its solid-propellant design allowed for rapid deployment of small scientific payloads, contributing to Japan's independent access to space for fundamental research without reliance on larger liquid-fueled systems.[2] Between 2003 and 2006, successful M-V missions placed four astronomical satellites into orbit, yielding data that refined models of stellar evolution, galactic structures, and solar dynamics.[5] The Suzaku (Astro-E2) X-ray observatory, launched on July 10, 2005, aboard M-V Flight #6, achieved unprecedented sensitivity in the 0.3–700 keV energy range, detecting faint emissions from supernova remnants and black hole accretion disks.[22] Observations revealed detailed elemental abundances, such as silicon and sulfur in supernova fireballs, challenging prior assumptions about explosive nucleosynthesis and providing empirical constraints on progenitor star compositions.[23] Suzaku's broad-band spectroscopy also mapped temperature gradients in galaxy clusters, informing dark matter distribution models through gravitational lensing correlations.[22] AKARI (Astro-F), deployed on February 21, 2006, via M-V Flight #7, conducted an all-sky infrared survey with enhanced resolution and sensitivity over prior missions like IRAS, cataloging over 870,000 point sources and resolving obscured star-forming regions in distant galaxies.[24] This data advanced understanding of dust-enshrouded protostars and active galactic nuclei, quantifying polycyclic aromatic hydrocarbon contributions to interstellar medium chemistry.[24] Hinode (Solar-B), launched September 23, 2006, on M-V Flight #8, delivered high-resolution magnetograms and vector field measurements of the solar photosphere, elucidating coronal heating mechanisms via nanoflares and magnetic reconnection events.[25] Its observations traced solar wind origins to pseudostreamers and open field lines, correlating plasma outflows with photospheric motions and predicting space weather impacts on Earth's magnetosphere.[26] Over 11 years of operation, Hinode's data supported causality in solar flare energy release, linking sub-photospheric flows to eruptive prominences.[27] In space exploration, the Hayabusa probe, launched May 9, 2003, by M-V Flight #4, achieved the first asteroid sample return from Itokawa in 2010, validating ion propulsion for deep-space maneuvers and autonomous optical navigation under low-thrust conditions.[2] Recovered particles confirmed S-type asteroid regolith properties, informing collisional evolution models and resource utilization prospects for future mining missions.[2] These outcomes demonstrated M-V's role in enabling precursor technologies for interplanetary sample returns, influencing subsequent endeavors like Hayabusa2.[2]Operational Challenges
Failures and Root Causes
The M-V launch vehicle experienced a single failure across its four operational missions, occurring on February 10, 2000, during the M-V-4 flight intended to deploy the Astro-E X-ray observatory satellite. Approximately 41 seconds after liftoff from the Uchinoura Space Center, the first-stage solid rocket motor suffered a combustion anomaly, resulting in insufficient thrust and a shortfall in velocity that prevented orbital insertion; the payload followed a suborbital trajectory and was lost.[1][28] Post-flight analysis identified the root cause as the detachment of a ceramic heat insulator within the first-stage nozzle, which enlarged the nozzle throat area and degraded engine performance by reducing pressure and specific impulse. This insulator failure was preceded by anomalous vibrations detected at 25 seconds, likely exacerbating structural stresses on the graphite-based nozzle components. Investigations revealed potential material defects in the graphite, such as undetected cracks or delaminations, that compromised insulator adhesion under high thermal and aerodynamic loads.[29][3] In response, the Institute of Space and Astronautical Science (ISAS, predecessor to JAXA components) enhanced quality control protocols, including advanced ultrasonic testing for graphite materials to detect subsurface flaws prior to integration, which informed subsequent successful launches like M-V-5 (Hayabusa) in 2003. No systemic design flaws beyond this isolated material integrity issue were identified, underscoring the challenges of solid-propellant nozzle durability in high-performance regimes where erosion, vibration, and thermal gradients can propagate minor defects into catastrophic failures.[30]Cost and Efficiency Critiques
The M-V program's development cost totaled approximately 15 billion yen, reflecting investments in advanced solid-propellant stages tailored for scientific payloads.[31] Per-launch expenses reached about 7 billion yen, equivalent to roughly $60 million in 1999 dollars, driven by bespoke manufacturing of high-performance motors and extensive ground support infrastructure.[32][6] These figures positioned the M-V as one of the more expensive small-lift vehicles of its era, with an individual launcher priced at around $56 million excluding payload integration.[13] Critiques of the M-V's efficiency highlighted its design prioritization of payload performance—such as 1,300 kg to a 200 km polar orbit—over cost containment, resulting in limited economies of scale from low production volumes.[6] Outdated operational concepts, including lengthy preparation times and minimal automation, inflated recurrent costs without corresponding benefits in reliability or cadence.[33] The program's infrequent launches, spanning only a decade with sparse missions, poorly amortized development and sustainment expenses, yielding a high effective cost per kilogram delivered compared to clustered or liquid-fueled competitors.[6] These inefficiencies contributed to the M-V's retirement after its February 2006 launch, as Japanese space officials sought alternatives to sustain small satellite access amid budget constraints.[32] The successor Epsilon program explicitly addressed these shortcomings by incorporating heritage components from larger rockets like the H-IIA's solid boosters and streamlining processes to halve launch costs to approximately 3.8 billion yen.[34] Despite its technical achievements in precision orbital insertion, the M-V's model underscored the challenges of all-solid architectures in balancing specialized performance against fiscal realism for national space agencies.[33]Legacy and Successors
Technological Transition to Epsilon
The Epsilon launch vehicle was developed by the Japan Aerospace Exploration Agency (JAXA) as the direct successor to the M-V, following the latter's retirement in 2006 after seven launches, primarily to address the M-V's high operational costs exceeding $70 million per mission.[35][36] Epsilon inherits core solid-propellant motor technologies from the M-V for its second and third stages while incorporating the H-IIA rocket's solid rocket booster (SRB-A) as the first stage, enabling a three-stage configuration optimized for payloads up to 1,200 kg to low Earth orbit—approximately two-thirds of the M-V's capacity.[37][34] This hybrid approach reduced development expenditures and leveraged proven components to accelerate deployment, with Epsilon's maiden flight occurring on September 21, 2013.[38] Key innovations in the transition emphasized cost efficiency and operational simplicity over the M-V's design, which relied on an inclined launch pad and extensive pre-launch preparations requiring about two months and 150 personnel.[35] Epsilon introduced a vertical launch system with a mobile service tower, electric-powered ignition for all stages (replacing pyrotechnic systems), and autonomous health checks using onboard artificial intelligence to monitor systems and detect anomalies, shrinking ground crew needs to seven people and preparation time to one week.[38][34] These changes stemmed from a two-step development strategy initiated around 2007 under project manager Yasuhiro Morita, who had previously led the M-V program, focusing first on next-generation technologies like simplified ground infrastructure before full-scale production.[39][40] The transition also optimized structural elements for reliability and payload protection, such as enhanced vibration damping during ascent and a redesigned fairing derived from M-V components but with improved separation mechanisms.[41] While retaining the M-V's second-stage motor (upgraded as the M-34E) and adapting its third stage, Epsilon's overall smaller footprint—standing 26 meters tall compared to the M-V's 29 meters—facilitated launches from Uchinoura Space Center using a compact, truck-transportable assembly process.[38][37] This evolution marked Japan's shift toward commercially viable small-launch capabilities, with per-launch costs targeted at under $40 million, though subsequent variants like the Enhanced Epsilon have further refined motor casings and guidance for heavier payloads up to 1,450 kg.[36][42]Long-Term Program Implications
The M-V program's elevated per-launch costs, estimated at approximately 8 billion yen (around 80 million USD in early 2000s values), highlighted the economic unsustainability of bespoke solid-fuel rockets for infrequent scientific missions, influencing JAXA's subsequent emphasis on cost reduction through simplified designs and higher launch cadences.[43] This fiscal pressure contributed to the decision to retire the M-V after its final flight in 2006, redirecting resources toward the Epsilon launch vehicle, which inherited second- and third-stage motors from the M-V while incorporating automation to lower operational expenses by up to 30% compared to predecessors.[37] Reliability issues, including three failures among seven launches—such as the 1998 second-stage anomaly, 2000 first-stage nozzle malfunction, and 2006 guidance system error—exposed vulnerabilities in solid-propellant quality control and testing protocols, eroding confidence in Japan's independent launch capabilities during the early 2000s.[1] These setbacks, alongside parallel H-II series problems, catalyzed the 2003 merger of NASDA, ISAS, and NAL into JAXA, aiming for streamlined management and annual savings of 10 billion yen through reduced duplication.[44] Technologically, the M-V advanced domestic expertise in high-thrust solid motors and attitude control systems, such as the Solid Motor Side Jet, which informed Epsilon's enhanced variants and long-term aspirations for reusable vehicles capable of daily operations.[37] However, the program's mixed record underscored the causal trade-offs of all-solid architectures—rapid deployment versus precision limitations—prompting a hybrid approach in successors that balances self-reliance with international benchmarking to sustain Japan's niche in space science amid global competition.[45] This evolution reinforced policy priorities for rigorous failure analysis and iterative improvements, fostering resilience in JAXA's framework despite initial setbacks.[44]Strategic and Comparative Analysis
Dual-Use Military Potential
The M-V rocket's all-solid-propellant, three-stage design provided inherent dual-use potential due to the technology's storability, simplicity, and ability to enable rapid launches without pre-flight fueling, characteristics highly valued in military ballistic missiles for quick-response scenarios.[46] This contrasts with liquid-fueled systems, which require complex infrastructure and extended preparation times, making solid rockets preferable for defense applications like anti-ship or theater-range missiles. The M-V's first stage used a large-diameter solid motor derived from sounding rocket heritage, delivering thrust exceeding 1 million pounds-force, while subsequent stages employed high-performance composites for efficiency, technologies transferable to missile upper stages for precision guidance and payload delivery.[47] Analysts have assessed the M-V's configuration as possessing intercontinental ballistic missile (ICBM) capability if repurposed, with potential to deliver payloads of approximately 1-2 tons over trans-Pacific distances when optimized for suborbital trajectories rather than orbital insertion.[48] [47] For instance, its demonstrated reliability in seven launches from 1997 to 2006, including successful deployments of astronomy satellites to sun-synchronous orbits at altitudes around 700 km, underscored the maturity of its propulsion and avionics systems, which could hypothetically support nuclear or conventional warhead delivery with minimal modifications to reentry vehicles and targeting. Some Japanese defense advocates have explicitly compared the M-V to U.S. MX Peacekeeper ICBMs in terms of solid-fuel staging and test pedigree, arguing it as a latent asset for counterstrike options amid regional threats.[49] Despite this technical potential, Japan's Basic Space Law (enacted 2008, post-M-V era) and preceding policies strictly limited space activities to peaceful purposes, prohibiting offensive military adaptations of launch vehicles like the M-V, which conducted no defense-related missions during its operational lifespan from Uchinoura Space Center.[50] No verified instances exist of M-V technology being directly transferred to Japan's Self-Defense Forces for missile programs; instead, solid-rocket expertise influenced civilian successors like the Epsilon, while military rocketry drew from separate indigenous developments, such as Type 12 surface-to-ship missiles. Regional observers, including in China and North Korea, have cited the M-V's capabilities in critiques of Japan's space program as a veiled proliferation risk, though empirical evidence supports only civilian utilization.[47] The program's termination after the February 2006 M-V-8 failure shifted focus to cost-reduced alternatives, mitigating any escalation of dual-use concerns at the time.Benchmarks Against Global Solid-Fuel Rockets
The M-V rocket's payload capacity of 1,800 kg to a 200 km low Earth orbit (LEO) at 30° inclination marked a significant advancement over legacy solid-fuel vehicles like the U.S. Scout, which delivered approximately 210 kg to similar orbits.[6] This capability enabled the M-V to support heavier scientific payloads, such as astronomical observatories and planetary probes, without hybrid liquid stages or air-launch assistance. In comparison, Russia's Start-1, derived from the SS-25 ICBM, offered 500–632 kg to LEO but with limited operational tempo and mixed reliability across fewer than five launches.[51] U.S. Minotaur variants, repurposed from Minuteman and Peacekeeper missiles, provided competitive capacities—Minotaur I at 580 kg to LEO and Minotaur IV at up to 1,730 kg—but benefited from mature military-grade components, achieving 100% success in 11 Minotaur I missions.[52] The M-V's six successful missions out of seven attempts, primarily for precision science orbits, yielded an approximate 86% rate, lower than the Scout's 96% across 114 launches but reflective of its bespoke design for non-reusable, high-fidelity scientific insertion rather than mass-produced reliability.[5][53]| Vehicle | Country | LEO Payload (kg) | Launches | Success Rate |
|---|---|---|---|---|
| M-V | Japan | 1,800 | 7 | ~86% |
| Scout | USA | 210 | 114 | 96% |
| Start-1 | Russia | 500–632 | ~4 | Variable |
| Minotaur I | USA | 580 | 11 | 100% |