A two-stage-to-orbit (TSTO) or two-stage rocket
launch vehicle
A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pad, launch pads, supported by a missile launch contro ...
is a spacecraft in which two distinct
stages
Stage or stages may refer to:
Acting
* Stage (theatre), a space for the performance of theatrical productions
* Theatre, a branch of the performing arts, often referred to as "the stage"
* ''The Stage'', a weekly British theatre newspaper
* S ...
provide propulsion consecutively in order to achieve orbital velocity. It is intermediate between a
three-stage-to-orbit
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 ...
launcher and a hypothetical
single-stage-to-orbit
A single-stage-to-orbit (SSTO) vehicle reaches orbit from the surface of a body using only propellants and fluids and without expending tanks, engines, or other major hardware. The term usually, but not exclusively, refers to reusable vehicles ...
(SSTO) launcher.
At liftoff the first stage is responsible for accelerating the vehicle. At some point the second stage detaches from the first stage and continues to orbit under its own power.
An advantage of such a system over single-stage-to-orbit is that the most of the dry mass of the vehicle is not carried into orbit. This reduces the cost involved in reaching orbital velocity, as much of the structure and engine mass is ejected, and a larger percentage of the orbited mass is payload mass.
An advantage over three or more stages is a reduction in complexity and fewer
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 i ...
s, which reduces cost and risk of failure.
Examples
*Historical
**
Cosmos-3M
The Kosmos-3M (russian: Космос-3М meaning "''Cosmos''", GRAU index 11K65M) was a Russian space launch vehicle, member of the Kosmos rocket family. It was a liquid-fueled two-stage launch vehicle, first launched in 1967 and with over 420 ...
**
Delta IV
Delta IV is a group of five expendable launch systems in the Delta (rocket family), Delta rocket family introduced in the early 2000s. Originally designed by Boeing's Defense, Space and Security division for the National Security Space Launch, ...
(medium variant)
**
Falcon 1
Falcon 1 was a small-lift launch vehicle that was operated from 2006 to 2009 by SpaceX, an American aerospace manufacturer. On 28 September 2008, Falcon 1 became the first privately-developed fully liquid-fueled launch vehicle to go into orbit ...
**
Saturn IB
The Saturn IB (also known as the uprated Saturn I) was an American launch vehicle commissioned by the NASA, National Aeronautics and Space Administration (NASA) for the Apollo program. It uprated the Saturn I by replacing the S-IV second stage (, ...
**
Saturn V-SL1 (
Skylab
Skylab was the first United States space station, launched by NASA, occupied for about 24 weeks between May 1973 and February 1974. It was operated by three separate three-astronaut crews: Skylab 2, Skylab 3, and Skylab 4. Major operations in ...
launch only)
**
Titan II GLV
The Titan II GLV (Gemini Launch Vehicle) or Gemini-Titan II was an American expendable launch system derived from the Titan II missile, which was used to launch twelve Gemini missions for NASA between 1964 and 1966. Two uncrewed launches follo ...
**
Tsyklon-2
The Tsyklon-2 (Cyclone-2), also known as Tsiklon-2 and Tsyklon-M (known as SL-11 by the United States DoD), GRAU index 11K69, was a Soviet, later Ukrainian, orbital carrier rocket used from the 1960s to the late 2000s.
The rocket had 106 launch ...
**
Zenit-2
The Zenit-2 is a Ukrainian, previously Soviet, expendable carrier rocket. First flown in 1985, it has been launched 37 times, with 6 failures. It is a member of the Zenit family of rockets and was designed by the Yuzhmash.
History
With 13–15 ...
and
Zenit-2M
The Zenit-2M, Zenit-2SB, Zenit-2SLB or Zenit-2FG was a Ukrainian expendable carrier rocket derived from the Zenit-3SL. It was a member of the Zenit family of rockets, which were designed by the Yuzhmash.
Development
The Zenit 2M was a modernis ...
*Current
**
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 originally designed by Lockheed Martin, now being operated by United Launch Alliance (ULA), a joint venture be ...
(401 and 501 variants)
**
Electron
The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family,
and are generally thought to be elementary particles because they have no kn ...
**
Falcon 9
Falcon 9 is a partially reusable medium lift launch vehicle that can carry cargo and crew into Earth orbit, produced by American aerospace company SpaceX.
The rocket has two stages. The first (booster) stage carries the second stage and payl ...
**
Long March 5
Long March 5 (LM-5; zh, s=长征五号 , p=Chángzhēng wǔ hào), or Changzheng 5 (CZ-5), and also by its nickname "''Pang-Wu''" (胖五, "''Fat-Five''"), is a Chinese heavy-lift launch vehicle developed by the China Academy of Launch Vehicle ...
(default configuration)
*In development
**
Angara
The Angara ( Buryat and mn, Ангар, ''Angar'', "Cleft"; russian: Ангара́, ''Angará'') is a major river in Siberia, which traces a course through Russia's Irkutsk Oblast and Krasnoyarsk Krai. It drains out of Lake Baikal and is ...
1.2
**
Starship
A starship, starcraft, or interstellar spacecraft is a theoretical spacecraft designed for interstellar travel, traveling between planetary systems.
The term is mostly found in science fiction. Reference to a "star-ship" appears as early as 188 ...
**
New Glenn
New Glenn is a heavy-lift orbital launch vehicle in development by Blue Origin. Named after NASA astronaut John Glenn, design work on the vehicle began in 2012. Illustrations of the vehicle, and the high-level specifications, were initial ...
**
Miura 5
Miura 5 is a two-stage European orbital recoverable launch vehicle of the Spanish company PLD Space currently under development. Miura 5 will be 24.9 m long, capable of inserting 900 kg of payload into a low Earth orbit (LEO), featuring an ...
**
Vulcan
Vulcan may refer to:
Mythology
* Vulcan (mythology), the god of fire, volcanoes, metalworking, and the forge in Roman mythology
Arts, entertainment and media Film and television
* Vulcan (''Star Trek''), name of a fictional race and their home p ...
It is not always clear when a vehicle is a TSTO, due to the use of strap-on
booster rockets
A booster rocket (or engine) is either the first stage of a multistage rocket, multistage launch vehicle, or else a shorter-burning rocket used in parallel with longer-burning sustainer engine, sustainer rockets to augment the space vehicle's t ...
at launch. These are dropped early on in the flight and may or may not be considered an additional stage if the core engine(s) continue firing. These are sometimes considered half a stage, leading to the expression one-and-a-half-stage-to-orbit (1.5STO) e.g. for the
Long March 5B
Long March 5 (LM-5; zh, s=长征五号 , p=Chángzhēng wǔ hào), or Changzheng 5 (CZ-5), and also by its nickname "''Pang-Wu''" (胖五, "''Fat-Five''"), is a Chinese heavy-lift launch vehicle developed by the China Academy of Launch Vehicle ...
or the
Atlas missile
The SM-65 Atlas was the first operational intercontinental ballistic missile (ICBM) developed by the United States and the first member of the Atlas rocket family. It was built for the U.S. Air Force by the Convair Division of General Dyna ...
,
which was a single core stage with additional boosters. Similarly, two-stage designs with additional boosters can be referred to as 2.5-stage rockets e.g. the
Ariane 5
Ariane 5 is a European heavy-lift space launch vehicle developed and operated by Arianespace for the European Space Agency (ESA). It is launched from the Centre Spatial Guyanais (CSG) in French Guiana. It has been used to deliver payloads int ...
or most
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 originally designed by Lockheed Martin, now being operated by United Launch Alliance (ULA), a joint venture be ...
variants (all except the 401 and 501).
Reusable launch systems
With reference to a
reusable launch system
A reusable launch vehicle have parts that can be recovered and reflown, while carrying payloads from the surface to outer space. Rocket stages are the most common launch vehicle parts aimed for reuse. Smaller parts such as rocket engines and boost ...
this approach is often proposed as an alternative to single-stage-to-orbit (or ''SSTO''). Its supporters argue that, since each stage may have a lower
mass ratio
In aerospace engineering, mass ratio is a measure of the efficiency of a rocket. It describes how much more massive the vehicle is with propellant than without; that is, the ratio of the rocket's ''wet mass'' (vehicle plus contents plus propellan ...
than an SSTO launch system, such a system may be built further away from limits of its structural materials. It is argued that a two-stage design should require less maintenance, less testing, experience fewer failures and have a longer working life. In addition the two-stage approach allows the lower stage to be optimized for operation in the Earth's lower atmosphere, where pressure and drag are high, while the upper stage can be optimized for operation in the near-vacuum conditions of the later part of the launch. This allows an increase in the payload mass fraction of a two-stage vehicle over single-stage or stage-and-a-half vehicles, which have to perform in both environments using the same hardware.
Critics argue that the increased complexity of designing two separate stages that must interact, the logistics involved in returning the first stage to the launch site, and the difficulties of conducting incremental testing on a second stage will outweigh these benefits. In the case of airplane-like lower stages they also argue how difficult and expensive high speed aircraft (like the
SR-71
The Lockheed SR-71 "Blackbird" is a Range (aeronautics), long-range, high-altitude, Mach number, Mach 3+ military strategy, strategic reconnaissance aircraft developed and manufactured by the American aerospace company Lockheed Corporati ...
) are to develop and operate, and question performance claims. Many 'mini-shuttle' designs that use transport aircraft as first stages also face similar problems with ice/foam as the
Space Shuttle
The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program na ...
due to the requirement they also carry a large external tank for their fuel.
SpaceX
Space Exploration Technologies Corp. (SpaceX) is an American spacecraft manufacturer, launcher, and a satellite communications corporation headquartered in Hawthorne, California. It was founded in 2002 by Elon Musk with the stated goal of ...
is the only launch provider which
achieved
Achieved (13 May 1979 – 1993) was an Irish Thoroughbred racehorse and sire. He won four of his nine races in a track career which lasted from July 1981 to September 1982. As a two-year-old he was undefeated in three starts including the ...
first-stage reuse of an orbital vehicle with the two-stage
Falcon 9
Falcon 9 is a partially reusable medium lift launch vehicle that can carry cargo and crew into Earth orbit, produced by American aerospace company SpaceX.
The rocket has two stages. The first (booster) stage carries the second stage and payl ...
and 2.5-stage
Falcon Heavy
Falcon Heavy is a partially reusable heavy-lift launch vehicle that is produced by SpaceX, an American aerospace manufacturer. The rocket consists of two strap-on boosters made from Falcon 9 first stages, a center core also made from a Falc ...
.
Rocket Lab
Rocket Lab is a public American aerospace manufacturer and launch service provider, with a New Zealand subsidiary. The company operates lightweight Electron orbital rockets, which provide dedicated launches for small satellites. Rocket Lab also ...
has recovered a first stage of their
Electron
The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family,
and are generally thought to be elementary particles because they have no kn ...
rocket, but has not flown it again.
Helicopter-like first stage
Taking the view that airplane like operations do not translate to airplane-like appearance, some reusable TSTO concepts have first stages that operate as
VTOL
A vertical take-off and landing (VTOL) aircraft is one that can take off and land vertically without relying on a runway. This classification can include a variety of types of aircraft including helicopters as well as thrust-vectoring fixed-win ...
or
VTOHL aircraft. The
DC-X
The DC-X, short for Delta Clipper or Delta Clipper Experimental, was an uncrewed prototype of a reusable single-stage-to-orbit launch vehicle built by McDonnell Douglas in conjunction with the United States Department of Defense's Strategic De ...
has proven the VTOL option design workable. Other designs like the
DH-1 concept take it a step further and use a 'pop-up/pop-down' approach, which delivers the orbiting stage to a point about 60 km above the earth's surface, before dropping down to the launch pad again. In the case of the DH-1, the upper stage is effectively an 'almost SSTO' with a more realistic mass fraction and which was optimised for reliability.
Airplane-like first stage
Some TSTO designs comprise an
airplane
An airplane or aeroplane (informally plane) is a fixed-wing aircraft that is propelled forward by thrust from a jet engine, propeller, or rocket engine. Airplanes come in a variety of sizes, shapes, and wing configurations. The broad spe ...
-like first stage and a
rocket
A rocket (from it, rocchetto, , bobbin/spool) is a vehicle that uses jet propulsion to accelerate without using the surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely fr ...
-like second stage. The airplane elements can be wings, air-breathing engines, or both. This approach appeals because it transforms
Earth's atmosphere
The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for ...
from an obstacle into an advantage. Above a certain speed and altitude, wings and
scramjet
A scramjet (supersonic combustion ramjet) is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow. As in ramjets, a scramjet relies on high vehicle speed to compress the incoming air forcefully ...
s cease being effective, and the rocket is deployed to complete the trip to orbit.
Saenger (spacecraft)
Saenger or Sänger was a West German concept design for a two-stage-to-orbit spaceplane. It is named after Eugen Sänger, who had been a key figure in the development of the concept for aerospace company Junkers.Hallmann, Willi and Ley, W. (Eds.) ...
was among the first concepts of this type.
While not an orbital vehicle, the successful private
SpaceShipOne
SpaceShipOne is an experimental air-launched rocket-powered aircraft with sub-orbital spaceflight capability at speeds of up to 3,000 ft/s (900 m/s, 3240 km/h), using a hybrid rocket motor. The design features a unique "feathering" a ...
suborbital spacecraft developed for the
Ansari X Prize demonstrated that a two-stage system with a winged aircraft as the "lower half" can reach the
edge of space. The team behind SpaceShipOne has built and flown a commercial sub-orbital launch system —
SpaceShipTwo
The Scaled Composites Model 339 SpaceShipTwo (SS2) is an air-launched suborbital spaceplane type designed for space tourism. It is manufactured by The Spaceship Company, a California-based company owned by Virgin Galactic.
SpaceShipTwo is car ...
— based on this technology.
The
Pegasus rocket
Pegasus is an Air launch to orbit, air-launched launch vehicle developed by Orbital Sciences Corporation (OSC) and now built and launched by Northrop Grumman. Capable of carrying small payloads of up to into low Earth orbit, Pegasus first fl ...
while airplane launched, is not a two-stage-to-orbit system because the rocket component itself is composed of multiple stages.
References
{{DEFAULTSORT:Two-Stage-To-Orbit
Chinese inventions
Space access
Rocket propulsion
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