Aircraft have different ways totake off and land. Conventionalairplanes accelerate along the ground until reaching a speed that is sufficient for the airplane totakeoff and climb at a safe speed. Some airplanes can take off at low speed, this being a short takeoff. Some aircraft such as helicopters andHarrier jump jets cantake off and land vertically. Rockets also usually take off vertically, but some designs can land horizontally.
Takeoff is the phase offlight in which anaircraft goes through a transition from moving along the ground (taxiing) to flying in the air, usually starting on arunway. Forballoons,helicopters and some specialized fixed-wing aircraft (VTOL aircraft such as theHarrier), no runway is needed. Takeoff is the opposite oflanding.
Landing is the last part of aflight, where a flyingaircraft orspacecraft (oranimals) returns to the ground. When the flying object returns to water, the process is calledalighting, although it is commonly called "landing" and "touchdown" as well. A normal aircraft flight would include several parts of flight includingtaxi,takeoff,climb,cruise,descent and landing.
RTOL aircraft require shorter runways than conventional types, typically 3,500 feet (1,100 m) to 4,500 feet (1,400 m).[1][2]
STOL is anacronym forshort take-off and landing,aircraft with very shortrunway requirements, typically between 2,000 feet (610 m) to 3,500 feet (1,100 m).[2]
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CATOBAR (catapult assisted takeoff but arrested recovery) is a system used for the launch and recovery of aircraft from the deck of anaircraft carrier. Under this technique, aircraft are launched using acatapult and land on the ship (the recovery phase) usingarrestor wires.
Although this system is more costly than alternative methods, it provides greater flexibility in carrier operations, since it allows the vessel to support conventional aircraft. Alternate methods of launch and recovery can only use aircraft withSTOVL orSTOBAR capability.
STOBAR (Short Take Off But Arrested Recovery) is a system used for the launch and recovery of aircraft from the deck of anaircraft carrier, combining elements of bothSTOVL (Short Take-Off and Vertical Landing) andCATOBAR (Catapult Assisted Take-Off But Arrested Recovery).
Horizontal takeoff, horizontal landing (HTHL) — is the mode of operation for the first private commercial spaceplane, the two-stage-to-spaceScaled Composites Tier One from theAnsari X-PrizeSpaceShipOne/WhiteKnightOne combination. It is also used for the upcomingTier 1bSpaceShipTwo/WhiteKnightTwo combination. A prominent example of its use was theNorth American X-15 program. In these examples the space craft are carried to altitude on a "mother ship" before launch.The failed proposals for NASA Space Shuttle replacements,Rockwell X-30 NASP used this mode of operation but were conceived as single stage to orbit.
TheLynx rocketplane was asuborbital HTHL spaceplane developed byXCOR Aerospace that was slated to begin atmospheric flight testing in late 2011.[3] However, after numerous delays, XCOR Aerospace went bankrupt in 2017 without finishing a prototype.[4]
Reaction Engines Skylon, a design descendant of the 1980s BritishHOTOL ("Horizontal Take-Off and Landing") design project, is an HTHLspaceplane currently in the early stages of development in theUnited Kingdom.[5]
Both theLynx rocketplane andSpaceShipTwo have been proffered to NASA to carrysuborbital research payloads in response to NASA's suborbital reusable launch vehicle (sRLV) solicitation under the NASA Flight Operations Program.[6]
An early example was the 1960sNorthrop HL-10 atmospheric test aircraft where the HL stands for "Horizontal Lander".[7]
Different terms are used for takeoff and landing depending on the source of thrust used. VTVL uses rockets, whereas VTOL uses air, propelled via some kind of rotor system.
Vertical Take-Off and Landing (VTOL)aircraft includesfixed-wing aircraft that can hover, take off and land vertically as well ashelicopters and other aircraft with powered rotors, such astiltrotors.[8][9][10][11] The terminology for spacecraft and rockets isVTVL (vertical takeoff with vertical landing).[12] Some VTOL aircraft can operate in other modes as well, such asCTOL (conventional take-off and landing),STOL (short take-off and landing), and/orSTOVL (short take-off and vertical landing). Others, such as some helicopters, can only operate by VTOL, due to the aircraft lackinglanding gear that can handle horizontal motion. VTOL is a subset ofV/STOL (vertical and/or short take-off and landing).
Besides the ubiquitous helicopter, there are currently two types of VTOL aircraft in military service: craft using atiltrotor, such as theBellBoeingV-22 Osprey, and aircraft using directed jet thrust such as theHarrier family. In the civilian sector currently only helicopters are in general use (some other types of commercial VTOL aircraft have been proposed and are under development as of 2017).
Vertical takeoff, vertical landing (VTVL) is a form of takeoff and landing for rockets. Multiple VTVL craft have flown. The most widely known and commercially successful VTVL rocket is SpaceX'sFalcon 9 first stage.
VTVL technologies were developed substantially with small rockets after 2000, in part due toincentive prize competitions like theLunar Lander Challenge. Successful small VTVL rockets were developed byMasten Space Systems,Armadillo Aerospace, and others.
In aviation the term VTOHL ("Vertical Take-Off and Horizontal Landing") as well as several VTOHL aviation-specific subtypes: VTOCL, VTOSL, VTOBAR exist.
Thezero length launch system orzero length take-off system (ZLL, ZLTO, ZEL, ZELL) was a system wherebyjetfighters andattack aircraft were intended to be placed uponrockets attached to mobilelaunch platforms. Most zero length launch experiments took place in the 1950s, during theCold War.
Vertical takeoff, horizontal landing (VTHL) is the mode of operation for all current and formerly operational orbitalspaceplanes, such as theBoeing X-37, theNASASpace Shuttle, the 1988 SovietBuran space shuttle, and thePRCReusable experimental spacecraft/Shenlong. For launch vehicles an advantage of VTHL over HTHL is that the wing can be smaller, since it only has to carry the landing weight of the vehicle, rather than the takeoff weight.[13]
There have been several VTHL proposals that never flew, including the circa-1960USAFBoeing X-20 Dyna-Soar project, NASA Space Shuttle proposed replacements,Lockheed Martin X-33, andVentureStar. The 1990s NASA concept spaceplane, theHL-20 Personnel Launch System (HL stands for "Horizontal Lander"), was VTHL, as was a circa-2003 derivative of the HL-20, theOrbital Space Plane concept.
As of March 2011[update], two VTHLcommercial spaceplanes were in various stages of proposal/development, both successors to the HL-20 design. TheSierra Nevada CorporationDream Chaser follows theouter mold line of the earlier HL-20.The circa-2011 proposedOrbital Sciences CorporationPrometheus was ablended lifting body spaceplane that followed the outer mold line of the circa-2003 Orbital Space Plane, itself a derivative of the HL-20; however, Prometheus did not receive any NASA contracts and Orbital has announced they will not pursue further development.[14]
German Aerospace Center studied reusable VTHLLiquid Fly-back Boosters from 1999. Design was intended to replaceAriane 5solid rocket boosters.[15] TheU.S. government-funded,US$250,000,000,Reusable Booster System program, initiated by the USAF in 2010,[16]had specified a high-level requirement that the design be VTHL,[17]but the funding was discontinued after 2012.[18]
In 2017 DARPA selected a VTHL design forXS-1.
Few airplanes can operate with conventional takeoff and vertical landing (and its subtypesSTOVL, CATOVL) as theF-35B.
Horizontal takeoff and vertical landing (HTVL) in spaceflight has not been used, but has been proposed for some systems that use a two-stage to orbit launch system with a plane based first stage, and a capsule return vehicle. One of the few HTVL concept vehicles is the 1960s concept spacecraftHyperion SSTO, designed byPhilip Bono.[19]
Vehicles use more than one mode also exist.
Vertical and/or short take-off and landing (V/STOL)aircraft that are able to take off or land vertically or on short runways. Vertical takeoff and landing (VTOL) includes craft that do not require runways at all. Generally, a V/STOL aircraft needs to be able to hover; helicopters are not typically considered under the V/STOL classification.
A rolling takeoff, sometimes with a ramp (ski-jump), reduces the amount of thrust required to lift an aircraft from the ground (compared with vertical takeoff), and hence increases the payload and range that can be achieved for a given thrust. For instance, the Harrier is incapable of taking off vertically with a full weapons and fuel load. Hence V/STOL aircraft generally use a runway if it is available. I.e. Short Take-Off and Vertical Landing (STOVL) or Conventional Take-off and Landing (CTOL) operation is preferred toVTOL operation.
V/STOL was developed to allow fast jets to be operated from clearings in forests, from very short runways, and from smallaircraft carriers that would previously only have been able to carryhelicopters.
The main advantage of V/STOL aircraft is closer basing to the enemy, which reduces response time and tanker support requirements. In the case of theFalklands War, it also permitted high performance fighter air cover and ground attack without a large aircraft carrier equipped with a catapult.
The latest V/STOL aircraft is theF-35B, which entered service in 2015.[20]
work is coming along nicely on building the first test flight vehicle which the company hopes to fly by the end of the year.
Lynx: Type: HTHL / Piloted ... SpaceShipTwo: Type: HTHL / Piloted
CEO Dave Thompson said ... "I don't, at this time, anticipate that we'll continue to pursue our own project in that race. We'll watch it and if an opportunity develops we may reconsider. But at this point, I would not anticipate a lot of activity on our part in the commercial crew market."
Officials anticipate awarding up to three contracts for the project, where winners would compete for individual tasks of experiments and demonstrations that address technology, processes and other attributes of a reusable booster system, or RBS. Air Force officials envision an RBS that includes a reusable rocket and an expendable upper stage rocket. The reusable rocket would be launched vertically and return, landing aircraft style on a runway, after carrying the space craft to a point where the expendable rocket could take over.
The 'Hyperion' vehicle was truly remarkable since it would have been launched horizontally and landed vertically (HTVL) — an extremely rare combination. The payload capability was 110 passengers or 18t of cargo.
