air-launch-to-orbit
{{short description|Method of launching rockets at altitude from a conventional horizontal-takeoff aircraft}}
{{more footnotes needed|date=March 2013}}
File:Lockheed TriStar launches Pegasus with Space Technology 5.jpg Stargazer launches Pegasus carrying the three Space Technology 5 satellites in the skies of California, 2006]]
Air-launch-to-orbit (ALTO) is the method of launching smaller rockets at altitude from a heavier conventional horizontal-takeoff aircraft, to carry satellites to low Earth orbit. It is a follow-on development of air launches of experimental aircraft that began in the late 1940s. This method, when employed for orbital payload insertion, presents significant advantages over conventional vertical rocket launches, particularly because of the reduced mass, thrust, cost of the rocket, geographical factors, and natural disasters.
Air launching has also been developed for sub-orbital spaceflight. In 2004 the Ansari X Prize $10 Million purse was won by a team led by Burt Rutan's Scaled Composites, launching the SpaceShipOne from the purpose-built White Knight carrier aircraft.
The first air-launch-to-orbit was a test launch of the ASM-135 ASAT antisatellite rocket, the first commercial air-launch-to-orbit took place on 5 April 1990 with a Northrop Grumman Pegasus.
Advantages
The principal advantage of a rocket being launched by a high-flying airplane is that it need not fly through the lower, denser atmosphere, whose drag requires a considerable{{cite web |url=http://www.spacefuture.com/archive/flight_mechanics_of_manned_suborbital_reusable_launch_vehicles_with_recommendations_for_launch_and_recovery.shtml | title=Flight Mechanics of Manned Sub-Orbital Reusable Launch Vehicles with Recommendations for Launch and Recovery}} amount of extra work to overcome. Higher densities at lower altitudes result in larger drag forces acting on the vehicle. In addition, thrust is lost due to over-expansion of the exhaust at high ambient pressure and under-expansion at low ambient pressure; a fixed nozzle geometry cannot provide optimal exhaust expansion over the full range of ambient pressure, and represents a compromise solution. Rockets launched from high altitude can be optimized for lower ambient pressure, thus achieving greater thrust over the entire operating regime.
Propellant is conserved because the air-breathing carrier aircraft lifts the rocket to altitude much more efficiently. Airplane engines do not require on-board storage of an oxidizer, and they can use the surrounding air to produce thrust, such as with a turbofan. This allows the launch system to conserve a significant amount of mass that would otherwise be reserved for fuel, reducing the overall size. A larger fraction of the rocket mass can then include payload, reducing payload launch costs.
Air-launch-to-orbit offers the potential for aircraft-like operations such as launch-on-demand, and is also less subject to launch-constraining weather. This allows the aircraft to fly around weather conditions as well as fly to better launch points, and to launch a payload into any orbital inclination at any time. Insurance costs are reduced as well, because launches occur well away from land, and there is no need for a launch pad or blockhouse.{{citation needed|date=June 2013}}
Air-launch-to-orbit also works well as part of a combination launch system such as a reusable air-launched single-stage-to-skyhook launch vehicle powered by a rocket or jet engine.
An additional benefit of air-launch-to-orbit is a reduced delta V needed to achieve orbit. This results in a greater payload to fuel ratio which reduces the cost per kilogram to orbit. To further leverage the delta V advantage, supersonic air-launch-to-orbit has been proposed.{{cite web |url=http://m-selig.ae.illinois.edu/pubs/ClarkeEtal-2007-AIAA-2007-5841-AirLaunch.pdf |title=Conceptual Design of a Supersonic Air-launch System |accessdate=2014-12-03 |url-status=live |archiveurl=https://web.archive.org/web/20150210181223/http://m-selig.ae.illinois.edu/pubs/ClarkeEtal-2007-AIAA-2007-5841-AirLaunch.pdf |archivedate=2015-02-10 }}
Air-launch-to-orbit also serves as alternative if conditions do not allow launching a rocket vertically from ground to orbit due to certain reasons, such as natural disasters (earthquakes, tsunamis, floods and volcanic eruptions).
Disadvantages
According to Aviation Week and Space Technology, air-launch-to-orbit is limited by aircraft size. Additionally, airplanes may generate large lateral forces which could damage payloads.{{cite news|last1=Norris|first1=Guy|title=Design Space |work=Aviation Week and Space Technology|issue=2|date=15 February 2015|volume=177 }}
Air launch systems
Operational:
- Northrop Grumman Innovation Systems (originally Orbital Sciences, then Orbital ATK, since 2018 Northrop) Pegasus
Retired:
- ASM-135 ASAT (anti-satellite system)
- NOTS-EV-1 Pilot
- Virgin Orbit LauncherOne
Under development:
- Stratolaunch
- CubeCab {{cite web |title=Technologies |url=http://cubecab.com/technologies.html |accessdate=2015-12-01 |url-status=live |archiveurl=https://web.archive.org/web/20151208062458/http://cubecab.com/technologies.html |archivedate=2015-12-08 }}
- ARCASPACEARCA Space, [http://www.arcaspace.com/images/Haas_Orbital_Rocket_Launcher.pdf Haas Orbital Rocket Launcher] {{webarchive|url=https://web.archive.org/web/20120722021228/https://www.arcaspace.com/images/Haas_Orbital_Rocket_Launcher.pdf |date=2012-07-22 }} fact sheet, Dec. 2, 2008 (accessed 22 Sept 2014)
- Generation Orbit Launch Services{{cite news | last=Leone|first=Dan | title=Startup Generation Orbit Launch Service Bets Big on 'Small Space' | url=http://www.spacenews.com/article/launch-report/38365startup-generation-orbit-launch-service-bets-big-on-%E2%80%98small-space%E2%80%99 | archive-url=https://archive.today/20140407181528/http://www.spacenews.com/article/launch-report/38365startup-generation-orbit-launch-service-bets-big-on-%E2%80%98small-space%E2%80%99 | url-status=dead | archive-date=April 7, 2014 | date=November 26, 2013}} - contracted for NASA NEXT{{cite news| last=Diller| first=George| title=NASA Awards First CubeSat-Class Launch Services Contract| url=http://www.nasa.gov/centers/kennedy/news/releases/2013/release-20130930.html#.U0LmXahdXuN| date=September 30, 2013| url-status=live| archiveurl=https://web.archive.org/web/20130930203724/http://www.nasa.gov/centers/kennedy/news/releases/2013/release-20130930.html#.U0LmXahdXuN| archivedate=September 30, 2013}}
- NASA Armstrong Flight Research Center Towed Glider Air-Launch System
- CDTI, CNES, DLR Aldebaran (rocket)
- Antonov, Aerospace Industry Corporation of China Antonov An-225 Mriya{{cite news|last1=Borys|first1=Christian|title=The world's biggest plane may have a new mission|url=http://www.bbc.com/future/story/20170503-the-worlds-biggest-plane-may-have-a-new-mission|accessdate=20 October 2017|publisher=BBC|date=7 May 2017|url-status=live|archiveurl=https://web.archive.org/web/20171020053757/http://www.bbc.com/future/story/20170503-the-worlds-biggest-plane-may-have-a-new-mission|archivedate=20 October 2017}}
- Orbit Boy microsatellite air-launch system
Proposed:
- Vulcan Aerospace 75-percent-scaled Dream Chaser crew-carrying spaceplane with rocket by Orbital Sciences
{{cite news |last1=Gebhardt |first1=Chris |title=SNC, Stratolaunch expand on proposed Dream Chaser flights |url=http://www.nasaspaceflight.com/2014/11/snc-stratolaunch-dream-chaser-flights/ |accessdate=2014-11-27 |work=NASASpaceFlight.com |date=2014-11-26 |url-status=live |archiveurl=https://web.archive.org/web/20141128230714/http://www.nasaspaceflight.com/2014/11/snc-stratolaunch-dream-chaser-flights/ |archivedate=2014-11-28 }}
- {{Interlanguage link|OREL (rocket)|uk|3=Авіаційний космічний ракетний комплекс «Оріль»|lt=OREL}} (proposed by Ukraine)
- {{Interlanguage link|Sura (reusable launch vehicle)|uk|3=Безпілотний повітряно-космічний транспортний літак багаторазового використання «Сура»|lt=Sura}} (proposed by Ukraine)
Abandoned projects:
- DARPA ALASA
- AirLaunch LLC
- MAKS
- Ishim[http://www.bilkent.edu.tr/~crs/russiakazakhstan.htm Russia, Kazakhstan to develop unique space system] {{webarchive|url=https://web.archive.org/web/20130209151518/http://www.bilkent.edu.tr/~crs/russiakazakhstan.htm |date=2013-02-09 }}: "Ukrainian experts moved to develop the Svityaz system based on the An-225 Mriya (Dream) Cossack jumbo transport plane and the Zenit-2 rocket", "The Ishim complex will include two MiG-31I aircraft, a three-stage launch vehicle on a streamlined store between engine nacelles, as well as an Ilyushin Il-76MD Midas surveillance plane."
- {{Interlanguage link|Svityaz (rocket)|uk|3=Авіаційний космічний ракетний комплекс Світязь|lt=Svityaz}}
- Orbital Sciences Pegasus II – contracted design/build for Stratolaunch Systems
{{cite news |last=Bergin |first=Chris |title=Stratolaunch and Orbital – The Height of Air Launch |url=http://www.nasaspaceflight.com/2013/05/stratolaunch-orbital-air-launch/ |accessdate=2013-05-24 |newspaper=NASASpaceFlight.com |date=2013-05-25 |url-status=live |archiveurl=https://web.archive.org/web/20130608063833/http://www.nasaspaceflight.com/2013/05/stratolaunch-orbital-air-launch/ |archivedate=2013-06-08 }}
- Swiss Space Systems SOAR
- XCOR Aerospace Lynx Mark III
- Falcon 9 Air Developed 2011-2012, In partnership between SpaceX and Stratolaunch systems
See also
References
{{reflist}}
External links
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- [http://mae.engr.ucdavis.edu/faculty/sarigul/aiaa2001-4619.pdf A Study of Air Launch Methods for RLVs] (AIAA 2001-4619)
- [https://web.archive.org/web/20091229175301/http://www.ae.uiuc.edu/ISJ/Reports/BurtonJSRPaper.pdf Low Cost Launch of Payloads to Low Earth Orbit ]
- [https://web.archive.org/web/20110816184546/http://www.ae.illinois.edu/ISJ/ Illini Space Jet]