A modular rocket is a kind of

multistage rocket A multistage rocket or step rocket is a launch vehicle that uses two or more rocket ''stages'', each of which contains its own engines and propellant. A ''tandem'' or ''serial'' stage is mounted on top of another stage; a ''parallel'' stage is ...

which has components that can interchanged for different missions. Several such rockets use similar concepts such as unified modules to minimize expenses on manufacturing, transportation and for optimization of support infrastructure for flight preparations. The

National Launch System The National Launch System (or New Launch System) was a study authorized in 1991 by President George H. W. Bush to outline alternatives to the Space Shuttle for access to Earth orbit. Shortly thereafter, NASA asked Lockheed Missiles and Space, ...

study (1991-1992) looked at future launchers in a modular (cluster) fashion. This concept has existed since the

creation of NASA The National Aeronautics and Space Administration (NASA) was created in 1958 from the National Advisory Committee for Aeronautics (NACA), and other related organizations, as the result of the Space Race between the United States and the Soviet U ...

Examples

Saturn C

A government commission, the "Saturn Vehicle Evaluation Committee" (better known as the

Silverstein Committee The Saturn Vehicle Evaluation Committee, better known as the Silverstein Committee, was a US government commission assembled in 1959 to recommend specific directions that NASA could take with the Saturn rocket program. The committee was chaired by ...

), assembled in 1959 to recommend specific directions that NASA could take with the existing Army rocket program (Jupiter, Redstone, Sergeant). NASA's Space Exploration Program Council (1959-1963) was tasked with developing the launch architecture for the new

Saturn Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...

rocket series, called Saturn C. The Saturn C architecture consisted of five different stages ( S-I,

S-II The S-II (pronounced "S-two") was the second stage of the Saturn V rocket. It was built by North American Aviation. Using liquid hydrogen (LH2) and liquid oxygen (LOX) it had five J-2 engines in a quincunx pattern. The second stage accelerated ...

, S-III,

S-IV The S-IV was the Multistage rocket, second stage of the Saturn I rocket used by NASA for early flights in the Apollo program. The S-IV was manufactured by the Douglas Aircraft Company and later modified by them to the S-IVB, a similar but distinc ...

, and S-V/

Centaur A centaur ( ; ; ), occasionally hippocentaur, also called Ixionidae (), is a creature from Greek mythology with the upper body of a human and the lower body and legs of a horse that was said to live in the mountains of Thessaly. In one version o ...

) that could be stacked vertically for specific rockets to meet various NASA payload and mission requirements. This work led to development of the

Saturn I The Saturn I was a rocket designed as the United States' first medium lift launch vehicle for up to low Earth orbit Payload (air and space craft), payloads.Terminology has changed since the 1960s; back then, 20,000 pounds was considered "heavy l ...

Saturn IB The Saturn IB (also known as the uprated Saturn I) was an American launch vehicle commissioned by the National Aeronautics and Space Administration (NASA) for the Apollo program. It uprated the Saturn I by replacing the S-IV second stage (, 43,3 ...

, and

Saturn V The Saturn V is a retired American super heavy-lift launch vehicle developed by NASA under the Apollo program for human exploration of the Moon. The rocket was human-rated, had multistage rocket, three stages, and was powered by liquid-propel ...

rockets.

Atlas V

The

Atlas V Atlas V is an expendable launch system and the fifth major version in the Atlas (rocket family), Atlas launch vehicle family. It was developed by Lockheed Martin and has been operated by United Launch Alliance (ULA) since 2006. Primarily used to ...

expendable launch system An expendable launch system (or expendable launch vehicle/ELV) is a launch vehicle that can be launched only once, after which its components are destroyed during reentry or impact with Earth, or discarded in space. ELVs typically consist of s ...

uses the liquid fueled

Common Core Booster The Common Core Booster (CCB) is a rocket stage, which is used as the first stage of the American Atlas V rocket as part of its modular design. It was also intended that two additional CCBs would be used as boosters on the Atlas V Heavy, however ...

as its first stage. In many configurations, a single CCB is used with strap-on

solid rocket booster A solid rocket booster (SRB) is a solid propellant motor used to provide thrust in spacecraft launches from initial launch through the first ascent. Many launch vehicles, including the Atlas V, SLS and Space Shuttle, have used SRBs to give laun ...

s. A proposed configuration for heavier loads strapped together three CCBs for the first stage. The Common Core Booster utilizes the Russian made

RD-180 The RD-180 () is a rocket engine that was designed and built in Russia. It features a dual combustion chamber, dual-nozzle design and is fueled by a RP-1/ LOX mixture. The RD-180 is derived from the RD-170 line of rocket engines, which were use ...

burning

RP-1 RP-1 (Rocket Propellant-1 or Refined Petroleum-1) and similar fuels like RG-1 and T-1 are highly refined kerosene formulations used as rocket fuel. Liquid-fueled rockets that use RP-1 as fuel are known as kerolox rockets. In their engines, RP- ...

fuel with

liquid oxygen Liquid oxygen, sometimes abbreviated as LOX or LOXygen, is a clear cyan liquid form of dioxygen . It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an application which is ongoing. Physical ...

producing a thrust of 3.8 MN. The liquid propellant tanks use an

isogrid Isogrid is a type of partially hollowed-out structure formed usually from a single metal plate with integral triangular stiffening stringers. It was patented by McDonnell Douglas (now part of Boeing) in 1975. Isogrids are extremely light and stif ...

design for strength, replacing previous Atlas tank designs which were pressure stabilized. The length of the common core booster is , and has a diameter of .

Delta IV

The

Delta IV Delta IV was a group of five expendable launch systems in the Delta rocket family. It flew 45 missions from 2002 to 2024. Originally designed by Boeing's Defense, Space and Security division for the Evolved Expendable Launch Vehicle (EELV) p ...

launcher family used the liquid fuel

Common Booster Core The Common Booster Core (CBC) was an American rocket stage, which was used on the Delta IV rocket as part of a modular rocket system. Delta IV rockets flying in the Medium and Medium+ configurations each used a single Common Booster Core as th ...

as the first stage of the various rocket configurations. One or three modules could be used as the first stage. In most configurations a single CBC is used with or without strap-on SRBs. Three CBCs together formed the first stage of the Heavy configuration. The CBC used the

Rocketdyne Rocketdyne is an American rocket engine design and production company headquartered in Canoga Park, California, Canoga Park, in the western San Fernando Valley of suburban Los Angeles, California, Los Angeles, in southern California. Rocketdyne ...

RS-68 The RS-68 (Rocket System-68) was a liquid-fuel rocket engine that used liquid hydrogen (LH2) and liquid oxygen (LOX) as propellants in a gas-generator cycle. It was the largest hydrogen-fueled rocket engine ever flown. Designed and manufacture ...

engine and burned

liquid hydrogen Liquid hydrogen () is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecule, molecular H2 form. To exist as a liquid, H2 must be cooled below its critical point (thermodynamics), critical point of 33 Kelvins, ...

with liquid oxygen producing a thrust of .

Angara

The

Universal Rocket Module Universal Rocket Module (URM) is the name of the modular liquid fuelled first and second stage of the Angara expendable launch system. The first stage and booster variant is referred to as URM-1, while the second stage is referred to as URM-2. T ...

(URM) is the modular liquid fueled first stage of the Angara

. Depending on the configuration, the first stage can consist of 1, 3, 5 or 8 URMs. Each URM uses a Russian-made

RD-191 The RD-191 () is a high-performance single-combustion chamber rocket engine, developed in Russia and sold by Roscosmos. It is derived from the RD-180 dual-combustion chamber engine, which itself was derived in turn from the four-chamber RD-170 ...

engine burning

fuel with

producing a thrust of 1.92 MN.

Falcon Heavy

The Falcon Heavy launch vehicle consists of a strengthened

Falcon 9 Block 5 Falcon 9 Block 5 is a Reusable launch system#Partial reusable launch systems, partially reusable, human-rating certification, human-rated, two-stage-to-orbit, medium-lift launch vehicle designed and manufactured in the United States by SpaceX. I ...

center core with two regular Falcon 9 Block 5 core stages with aerodynamic nosecones mounted on top of both acting as liquid-fuel strap-on boosters. Each core is powered by nine

Merlin 1D Merlin is a family of rocket engines developed by SpaceX. They are currently a part of the Falcon 9 and Falcon Heavy launch vehicles, and were formerly used on the Falcon 1. Merlin engines use RP-1 and liquid oxygen as rocket propellants in a gas ...

engines burning rocket-grade kerosene fuel with

producing almost of thrust, and all three cores together producing over 22 MN of thrust. A first design of the Falcon Heavy included a unique propellant crossfeed capability, where fuel and oxidizer to power most of the engines on the center core would be fed from the two side cores, up until the side cores would be near empty and ready for the first

separation event A multistage rocket or step rocket is a launch vehicle that uses two or more rocket ''stages'', each of which contains its own engines and propellant. A ''tandem'' or ''serial'' stage is mounted on top of another stage; a ''parallel'' stage is ...

. However, due to its extreme complexity this feature was cancelled in 2015 leaving each of the three cores to burn its own fuel. Later evaluations revealed that the propellant needed for each side booster to land (reuse) are already close to the margins so there is really no advantage to crossfeed. Like the single stick Falcon 9, each Falcon Heavy booster core is reusable. The

Falcon Heavy Test Flight The Falcon Heavy test flight (also known as the Falcon Heavy demonstration mission) was the first attempt by SpaceX to launch a Falcon Heavy rocket on February 6, 2018, at 20:45 UTC. The successful test introduced the Falcon Heavy as the m ...

demonstrated the two side boosters landing simultaneously near their launch site, while the central booster attempted a landing on SpaceX's

Autonomous spaceport drone ship An autonomous spaceport drone ship (ASDS) is a modified ocean-going barge developed by SpaceX and equipped with propulsion systems to maintain precise position and a large floating landing platform, landing platform. They were developed to re ...

, which resulted in a hard landing near the ship. During the second mission all three boosters landed softly. A Falcon Heavy launch that succeeds in recovering all three core boosters has the same material expenditure as the Falcon 9, i.e. the upper stage and potentially the

payload fairing A payload fairing or nose fairing is a nose cone used to protect a launch vehicle, spacecraft payload (air and space craft), payload against the impact of dynamic pressure and aerodynamic heating during launch through an atmosphere. An additiona ...

. As such, the difference in cost between a Falcon 9 and a Falcon Heavy launch is limited, mainly to the extra fuel and refurbishing three as opposed to one booster core.

External links

EELV: The Next Stage of Space Launch

Angara page by Khrunichev Space Center (Russian)

References

{{DEFAULTSORT:Modular Rocket Rocketry Spacecraft components