![Vympel-R-77-maks2009](https://upload.wikimedia.org/wikipedia/commons/b/b2/Vympel-R-77-maks2009.jpg)
Grid fins (or lattice fins) are a type of
flight control surface
Aircraft flight control surfaces are aerodynamic devices allowing a pilot to adjust and control the aircraft's flight attitude.
Development of an effective set of flight control surfaces was a critical advance in the development of aircraft. Ea ...
used on
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 ...
s and
bomb
A bomb is an explosive weapon that uses the Exothermic process, exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy. Detonations inflict damage principally through ground- and atmosphere-t ...
s, sometimes in place of more conventional control surfaces, such as planar
fin
A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. Fin ...
s. They were developed in the 1950s by a team led by and used since the 1970s in various
Soviet
The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...
ballistic missile
A ballistic missile is a type of missile that uses projectile motion to deliver warheads on a target. These weapons are guided only during relatively brief periods—most of the flight is unpowered. Short-range ballistic missiles stay within the ...
designs such as the
SS-12 ''Scaleboard'',
SS-20 ''Saber'',
SS-21 ''Scarab'',
SS-23 ''Spider'', and
SS-25 ''Sickle'', as well as the
N-1 N1, N.I, N-1, or N01 may refer to:
Information technology
* Nokia N1, an Android tablet
* Nexus One, an Android phone made by HTC
* Nylas N1, a desktop email client
* Oppo N1, an Android phone
* N1, a Sun Microsystems software brand now mostly ...
(the intended rocket for the
Soviet moon program). In Russia, they are thus often referred to as ' grid fins.
Grid fins have also been used on conventional missiles and bombs such as the
Vympel R-77
The Vympel NPO R-77 missile ( NATO reporting name: AA-12 Adder) is a Russian active radar homing beyond-visual-range air-to-air missile. It is also known by its export designation RVV-AE. It is the Russian counterpart to the American AIM-120 ...
air-to-air missile; the
3M-54 Klub (SS-N-27 Sizzler) family of
cruise missile
A cruise missile is a guided missile used against terrestrial or naval targets that remains in the atmosphere and flies the major portion of its flight path at approximately constant speed. Cruise missiles are designed to deliver a large warhe ...
s; and the American
Massive Ordnance Air Blast
The GBU-43/B Massive Ordnance Air Blast (MOAB , colloquially known as the "Mother of All Bombs") is a large-yield bomb, developed for the United States military by Albert L. Weimorts, Jr. of the Air Force Research Laboratory. It was first tes ...
(MOAB) large-yield conventional bomb, and on specialized devices such as the
Quick-MEDS delivery system and as part of the
launch escape system
A launch escape system (LES) or launch abort system (LAS) is a crew-safety system connected to a space capsule that can be used to quickly separate the capsule from its launch vehicle in case of an emergency requiring the abort of the launch, suc ...
for the
Soyuz spacecraft
Soyuz () is a series of spacecraft which has been in service since the 1960s, having made more than 140 flights. It was designed for the Soviet space program by the Korolev Design Bureau (now Energia). The Soyuz succeeded the Voskhod spacecraf ...
.
In 2014,
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 ...
tested grid fins on a first-stage
demonstration test vehicle of its reusable
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 ...
rocket, and on December 21, 2015 they were used during the high-velocity atmospheric portion of the
reentry
Atmospheric entry is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet, or natural satellite. There are two main types of atmospheric entry: ''uncontrolled entry'', such as the entr ...
to help guide a commercial Falcon 9 first stage back to land for the first successful orbital booster landing in
spaceflight history.
The 1st stage of the private Chinese company i-Space's
Hyperbola-1
i-Space ( zh, s=星际荣耀, p=xīngjì róngyào, l=Interstellar Glory)—also known as Space Honor, Beijing Interstellar Glory Space Technology Ltd., Interstellar Glory or StarCraft Glory—is a Chinese private space technology developmen ...
rocket appeared on July 25, 2019 to be equipped with steerable grid fins for attitude control.
On July 25, 2019, China launched a modified version of
Long March 2C
The Long March 2C (LM-2C), also known as the Chang Zheng 2C (CZ-2C), is a Chinese orbital launch vehicle, part of the Long March 2 rocket family. Developed and manufactured by the China Academy of Launch Vehicle Technology (CALT), the Long Mar ...
which featured grid fins atop the first stage for controlled re-entry of the spent rocket stage away from people in nearby towns and cities.
Design characteristics
Conventional planar control fins are shaped like miniature
wing
A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is expres ...
s. By contrast, grid fins are a lattice of smaller aerodynamic surfaces arranged within a box. Their appearance has sometimes led them to be compared to
potato masher
A potato masher, tater masher, bean masher, pea masher, masher, or crusher is a food preparation utensil used to crush soft food for such dishes as mashed potatoes, Retrieved November 2016 apple sauce, or refried beans. Potatoes mashed using a po ...
s or
waffle iron
A waffle iron or waffle maker is a utensil or appliance used to cook waffles.
It comprises two metal plates with a connecting hinge, molded to create the honeycomb pattern found on waffles. The iron is heated and either batter is poured or dou ...
s.
Grid fins can be folded, pitched forward (or backwards), against the cylindrical body of a missile more directly and compactly than planar fins, allowing for more compact storage of the weapon; this is of importance where weapons are launched from a tube or for craft which store weapons in internal bays, such as
stealth aircraft
Stealth aircraft are designed to avoid detection using a variety of technologies that reduce reflection/emission of radar, infrared, visible light, radio frequency (RF) spectrum, and audio, collectively known as stealth technology. The F-117 N ...
. Generally, the grid fins pitch forward/backward away from the body shortly after the missile has cleared the firing craft.
Grid fins have a much shorter
chord (the distance between leading and trailing edge of the surface) than planar fins, as they are effectively a group of short fins mounted parallel to one another. Their reduced chord reduces the amount of
torque
In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of th ...
exerted on the steering mechanism by high-speed airflow, allowing for the use of smaller fin
actuators
An actuator is a component of a machine that is responsible for moving and controlling a mechanism or system, for example by opening a valve. In simple terms, it is a "mover".
An actuator requires a control device (controlled by control signal) an ...
, and a smaller tail assembly overall.
Grid fins perform very well at subsonic and supersonic speeds, but poorly at
transonic
Transonic (or transsonic) flow is air flowing around an object at a speed that generates regions of both subsonic and supersonic airflow around that object. The exact range of speeds depends on the object's critical Mach number, but transonic ...
speeds; the flow causes a
normal shock
In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a me ...
wave to form within the lattice, causing much of the airflow to pass completely around the fin instead of through it and generating significant
wave drag
In physics, mathematics, and related fields, a wave is a propagating dynamic disturbance (change from equilibrium) of one or more quantities. Waves can be periodic, in which case those quantities oscillate repeatedly about an equilibrium (res ...
. At high
Mach number
Mach number (M or Ma) (; ) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a boundary to the local speed of sound.
It is named after the Moravian physicist and philosopher Ernst Mach.
: \mathrm = \frac ...
s, grid fins flow fully supersonic and can provide lower
drag and greater maneuverability than planar fins.
Application in reusable launch vehicles
![Falcon 9 preparing to launch DSCOVR (16822013226)](https://upload.wikimedia.org/wikipedia/commons/b/bc/Falcon_9_preparing_to_launch_DSCOVR_%2816822013226%29.jpg)
Grid fins are used on the
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 ...
rocket for increased precision and accuracy in control of the landing location for
reusable launch vehicle
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 ...
s. It therefore helps the rocket to land on the landing pad or on the
autonomous spaceport drone ship
An autonomous spaceport drone ship (ASDS) is an ocean-going vessel derived from a deck barge, outfitted with station-keeping engines and a large landing platform and is autonomously controlled when on station for a landing. Construction of ...
more precisely with good accuracy. The grid fin
development effort is a part of the
SpaceX reusable launch system development program
SpaceX is privately funding the development of orbital launch systems that can be reused many times, in a manner similar to the reusability of aircraft. SpaceX has been developing the technologies over several years to facilitate full and ...
that has been underway since 2012. The first
hypersonic
In aerodynamics, a hypersonic speed is one that exceeds 5 times the speed of sound, often stated as starting at speeds of Mach 5 and above.
The precise Mach number at which a craft can be said to be flying at hypersonic speed varies, since in ...
flight test
Flight testing is a branch of aeronautical engineering that develops specialist equipment required for testing aircraft behaviour and systems. Instrumentation systems are developed using proprietary transducers and data acquisition systems. D ...
with grid fins was in February 2015, and grid fins were subsequently used on all reusable Falcon 9 experimental test landings and, eventually, after December 2015, an increasing number of successful first stage landings and recoveries.
Iteration on the design of the Falcon 9 grid fins continued into 2017. SpaceX CEO
Elon Musk
Elon Reeve Musk ( ; born June 28, 1971) is a business magnate and investor. He is the founder, CEO and chief engineer of SpaceX; angel investor, CEO and product architect of Tesla, Inc.; owner and CEO of Twitter, Inc.; founder of The Bori ...
announced in early 2017 that a new version of the Falcon 9 grid fins would improve reusability for the company's vehicles.
Falcon 9 Block 5
Falcon 9 Block 5 is a Reusable launch system#Partial reusable launch systems, partially reusable two-stage-to-orbit medium-lift launch vehicle designed and manufactured in the United States by SpaceX. It is the fifth version of Falcon 9 Full Thr ...
introduce new cast and cut
titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...
grid fins. Musk had noted the original Falcon 9 grid fins were made from
aluminum
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It has ...
. The fins experience temperatures near their maximum survivability limits during
reentry
Atmospheric entry is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet, or natural satellite. There are two main types of atmospheric entry: ''uncontrolled entry'', such as the entr ...
and landing, and so the aluminum fins were coated with an ablative thermal protection system. In fact, some aluminum grid fins have actually caught fire during the entry and landing sequence. The new titanium grid fins should introduce greater controllability to the rocket and increase the payload to orbit capability by allowing Falcon 9 to fly at a higher
angle of attack
In fluid dynamics, angle of attack (AOA, α, or \alpha) is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is m ...
.
The larger and more robust titanium grid fins are left unpainted and were first tested in June 2017. They are used on all reusable Block 5 Falcon 9 first stages since late 2017.
Gallery
File:Jsc2005e15407.jpg, Grid fins (here folded against the payload fairing
A payload fairing is a nose cone used to protect a spacecraft payload against the impact of dynamic pressure and aerodynamic heating during launch through an atmosphere. An additional function on some flights is to maintain the cleanroom environm ...
) are part of the launch escape system
A launch escape system (LES) or launch abort system (LAS) is a crew-safety system connected to a space capsule that can be used to quickly separate the capsule from its launch vehicle in case of an emergency requiring the abort of the launch, suc ...
of Soyuz spacecraft
Soyuz () is a series of spacecraft which has been in service since the 1960s, having made more than 140 flights. It was designed for the Soviet space program by the Korolev Design Bureau (now Energia). The Soyuz succeeded the Voskhod spacecraf ...
.
File:Shenzhou-12 roll out 02.png, Folded grid fins on Long March 2F designed to ferry crewed Shenzhou spacecraft
Shenzhou (, ; see ) is a spacecraft developed and operated by China to support its crewed spaceflight program, China Manned Space Program. Its design resembles the Russian Soyuz spacecraft, but it is larger in size. The first launch was on 19 ...
.
File:RSD-10 Grid stabilizer 1.jpg, Grid fins stowed against the base of an SS-20
The RSD-10 ''Pioneer'' (russian: ракета средней дальности (РСД) «Пионер» tr.: ''raketa sredney dalnosti (RSD) "Pioner"''; en, Medium-Range Missile "Pioneer") was an intermediate-range ballistic missile with a ...
ballistic missile
File:Falcon 9 first stage in hangar.jpg, Grid fins on a SpaceX Falcon 9 rocket. They guide the rocket's first stage during landing.
File:Falcon 9 1st stage re-entry with grid fins; DSCOVR mission (16849254595).png, First test of grid fins by SpaceX during a Falcon 9 controlled-descent test on 11 February 2015.
File:Starship SN16 and Booster in the High Bay.png, Grid fins deployed Super Heavy Booster Section of the 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 ...
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 ...
References
External links
Missile Grid Fins, ''Aerospaceweb.org''*
ttp://www.aviationweek.com/aw/generic/story_generic.jsp?channel=awst&id=news/03173news.xml "It's the Big One", ''Aviation Week''KLUB (SS-N-27) ASCM, ''Bharat-Rakshak.com''*
ttps://web.archive.org/web/20090312033219/http://www.defensetech.org/archives/001044.html Medical Missile Prepped for Launch, ''DefenseTech.org''
{{DEFAULTSORT:Grid Fin
Aerospace technologies
Aircraft wing design
Aircraft controls
Soviet inventions