The BT-4 is a pressure-fed

liquid A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, an ...

rocket engine A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive Jet (fluid), jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, i ...

designed and manufactured by

IHI Aerospace , formerly known as , is a Japanese engineering corporation headquartered in Tokyo, Japan that produces and offers ships, space launch vehicles, aircraft engines, marine diesel engines, gas turbines, gas engines, railway systems, turbochargers ...

of Japan. It was originally developed for the

LUNAR-A LUNAR-A is a cancelled Japanese spacecraft project that was originally scheduled to be launched in August 2004. After many delays (primarily due to potential thruster faults), the project was eventually cancelled in January 2007. It was planned t ...

project, but it has been used as a liquid apogee engine in some geostationary

communications satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Ear ...

based on the

Lockheed Martin A2100 The A2100 is a model of communications satellite spacecraft made by Lockheed Martin Space Systems. It is used as the foundation for telecommunications payloads in geosynchronous orbit, as well as GOES-R weather satellites and GPS Block IIIA satel ...

and GEOStar-2

satellite bus A satellite bus (or spacecraft bus) is the main body and structural component of a satellite or spacecraft, in which the payload and all scientific instruments are held. Bus-derived satellites are opposed to specially produced satellites. Bus- ...

es. It has also been used on the HTV and Cygnus

automated cargo spacecraft Cargo spacecraft are robotic spacecraft that are designed to carry cargo, possibly to support space stations' operation by transporting food, propellant and other supplies. This is different from a space probe, whose missions are to conduct sci ...

History

During the 1970s, Ishikawajima-Harima Heavy Industries had built under license the Rocketdyne MB-3 for the

N-I The N-I was the former main road from Madrid to France in Spain. Most of the route has now been replaced by the Autovía A-1 and Autopista AP-1. The A-1 starts at Madrid then goes to Burgos. N-I then runs parallel to AP-1 (toll highway) to Mira ...

rocket, for which it had also developed the second stage

attitude control system Spacecraft attitude control is the process of controlling the orientation of a spacecraft (vehicle/satellite) with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, et ...

. In the 1980s it also developed the thrusters for ETS-4 ( Kiku-3), the first to be built in Japan. In 2000 it acquired and merged with the aerospace division of Nissan and became

. IHI Aerospace started developing the BT-4 for the later cancelled

mission to the moon. While the mission was cancelled, the thruster has seen success as a liquid apogee engine on the Lockheed Martin

A2100 The A2100 is a model of communications satellite spacecraft made by Lockheed Martin Space Systems. It is used as the foundation for telecommunications payloads in geosynchronous orbit, as well as GOES-R weather satellites and GPS Block IIIA satelli ...

and

Orbital ATK Northrop Grumman Innovation Systems (NGIS) was a sector (business segment) of Northrop Grumman from 2018 through 2019. It was formed from Orbital ATK Inc. a company which resulted from the merger of Orbital Sciences Corporation and parts of Alli ...

GEOStar-2 platforms. Two other Orbital ATK products that use the BT-4 due to their leverage of the GEOStar-2 platform are the Cygnus spacecraft and the

Antares Antares is the brightest star in the constellation of Scorpius. It has the Bayer designation α Scorpii, which is Latinised to Alpha Scorpii. Often referred to as "the heart of the scorpion", Antares is flanked by σ Scorpii and τ S ...

Bi-propellant Third Stage (BTS). The use on the A2100 platform has allowed IHI to export the BT-4 even to American military programs such programs as the

MUOS The Mobile User Objective System (MUOS) is a United States Space Force narrowband military communications satellite system that supports a worldwide, multi-service population of users in the ultra high frequency (UHF) band. The system provides ...

and

AEHF Advanced Extremely High Frequency (AEHF) is a constellation of communications satellites operated by the United States Space Force. They are used to relay secure communications for the United States Armed Forces, the British Armed Forces, the C ...

. On March 9, 2006, IHI Aerospace announced that the AEHF-2 BT-4 engine had successfully performed its mission, unlike

AEHF-1 USA-214, also known as Advanced Extremely High Frequency-1 or AEHF-1, is a military communications satellite operated by the United States Air Force. It is the first of six satellites to be launched as part of the Advanced Extremely High Freque ...

's. On November 29, 2010 IHI Aerospace announced that it had received and order from Lockheed Martin of four BT-4 engines for AEHF-4, MUOS-4, MUOS-5 and

Vinasat-2 Vinasat-2 (stylized all uppercase) is the second Vietnamese satellite to be placed in orbit. It was launched at 22:13 UTC on May 15, 2012 (5:13am on May 16 in the Vietnam time zone) at the European Spaceport in Kourou in French Guiana in South ...

. With this order, it achieved its 100th-unit foreign engine export since it started selling abroad in 1999. For the HTV project, IHI developed a new version, the HBT-5, which enabled them to replace the American

R-4D The R-4D is a small hypergolic rocket engine, originally designed by Marquardt Corporation for use as a reaction control system thruster on vehicles of the Apollo crewed Moon landing program. Today, Aerojet Rocketdyne manufactures and markets m ...

from the third flight onward. On October 3, 2013, with the successful berthing of the

Cygnus Orb-D1 Orbital-D1, also known as Orb-D1, and Cygnus 1, was the first flight of the Cygnus cargo spacecraft developed by Orbital Sciences Corporation. It was named after the late NASA astronaut and Orbital Sciences executive G. David Low. The flight ...

mission, IHI announced that the propulsion was based on their 500N Delta-Velocity Engines. In January 2018, a BT-4 kick motor was used on the

GovSat-1 SES-16 / GovSat is a geostationary communications satellite designed and manufactured by Orbital ATK; LuxGovSat is a joint venture between SES and Luxembourg government. It has a mass of and has a design life of at least 15 years. The satelli ...

geosynchronous commsat flight.https://www.nasaspaceflight.com/2018/01/spacex-govsat-1-falcon-9-launch/
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Versions

The BT-4 is a family that has been used as liquid apogee engine, orbital maneuvering engine and as a thruster. Known variations: *BT-4 (Cygnus): Used mainly as thruster, it burns MMH/ N₂O₄ with a thrust of . It weighs and is tall. *BT-4 (450N): Used mainly as

LAE Lae () is the capital of Morobe Province and is the second-largest city in Papua New Guinea. It is located near the delta of the Markham River and at the start of the Highlands Highway, which is the main land transport corridor between the Highl ...

, it burns

Hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazin ...

/ N₂O₄ in a 1.69

O/F ratio Rocket propellant is the reaction mass of a rocket. This reaction mass is ejected at the highest achievable velocity from a rocket engine to produce thrust. The energy required can either come from the propellants themselves, as with a chemical ...

. It has a thrust of , a specific impulse of and an input pressure of . As of 2014, it had a demonstrated life of 32,850 seconds. *BT-4 (500N): Used mainly as

, it burns

/ N₂O₄ with a thrust of , a specific impulse of . It weighs and is tall. *490N MON Thruster: Burns MMH/ MON-3 with a nominal thrust, a specific impulse of and an inlet pressure of . As of 2014, it had a demonstrated life of 15,000 seconds. *HBT-5: Developed for the HTV to crew-rated standards, it burns MMH/ MON-3, and has a thrust of . Used in HTV-3 and since

HTV-5 Kounotori 5, also known as HTV-5, was the fifth flight of the H-II Transfer Vehicle, an uncrewed cargo spacecraft launched to resupply the International Space Station. It was launched on 19 August 2015. Specifications Major changes of Kouno ...

onward. *SELENE OME: Based on the DRTS Liquid apogee engine, the

SELENE In ancient Greek mythology and religion, Selene (; grc-gre, Σελήνη , meaning "Moon"'' A Greek–English Lexicon's.v. σελήνη) is the goddess and the personification of the Moon. Also known as Mene, she is traditionally the daughte ...

Orbital Maneuvering Engine burned a

/ MON-3 mixture. It had a thrust of and a specific impulse of with an input pressure of .

References

{{Orbital spacecraft rocket engines Rocket engines using hypergolic propellant Rocket engines using the pressure-fed cycle