Editing Beam-powered propulsion (section)

==Proposed systems==

===Lightcraft===
{{main|Lightcraft}}
A '''lightcraft''' is a vehicle currently{{When|date=May 2023}} under development that uses an external pulsed source of laser or maser energy to provide power for producing thrust.

The laser shines on a parabolic reflector on the vehicle's underside, concentrating the light to produce a region of extremely high temperature. The air in this region is heated and expands violently, producing thrust with each pulse of laser light. A lightcraft must provide this gas from onboard tanks or an ablative solid in space. By leaving the vehicle's power source on the ground and using the ambient atmosphere as reaction mass for much of its ascent, a lightcraft could deliver a substantial percentage of its launch mass to orbit. It could also potentially be very cheap to manufacture.

====Testing====
Early in the morning of 2 October 2000 at the High Energy Laser Systems Test Facility (HELSTF), Lightcraft Technologies, Inc. (LTI) with the help of Franklin B. Mead of the U.S. [[Air Force Research Laboratory]] and [[Leik Myrabo]] set a new world's altitude record of 233 feet (71 m) for its 4.8&nbsp;inch (12.2&nbsp;cm) diameter, {{convert|1.8|oz|adj=on}}, laser-boosted rocket in a flight lasting 12.7 seconds.<ref>{{Citation|last=Myrabo|title=LightCraft Launch Oct 2000 - laserbeam powered propulsion|date=2007-06-27|url=https://www.youtube.com/watch?v=KtH-SxqdtaA |archive-url=https://ghostarchive.org/varchive/youtube/20211211/KtH-SxqdtaA| archive-date=2021-12-11 |url-status=live|access-date=2016-12-08}}{{cbignore}}</ref> Although much of the 8:35 am flight was spent hovering at 230+ feet, the Lightcraft earned a world record for the longest ever laser-powered free flight and the greatest "air time" (i.e., launch-to-landing/recovery) from a light-propelled object. This is comparable to [[Robert Goddard (scientist)|Robert Goddard]]'s first test flight of his rocket design. Increasing the laser power to 100 kilowatts will enable flights up to a 30-kilometer altitude. They aim to accelerate a one-kilogram microsatellite into [[low Earth orbit]] using a custom-built, one-megawatt ground-based laser. Such a system would use just about 20 dollars worth of electricity, placing launch costs per kilogram to many times less than current launch costs (which are measured in thousands of dollars).{{Citation needed|date=January 2014}}

Myrabo's "[[lightcraft]]" design is a reflective funnel-shaped craft that channels heat from the laser toward the center, using a reflective parabolic surface, causing the laser to explode the air underneath it, generating lift. Reflective surfaces in the craft focus the beam into a ring, where it heats air to a temperature nearly five times hotter than the surface of the Sun, causing the air to expand explosively for thrust.

===Laser thermal rocket===
{{Main|Thermal rocket}}
A laser thermal rocket is a [[thermal rocket]] in which the propellant is heated by energy provided by an external laser beam.<ref>H. Krier and R. J. Glumb. [http://arc.aiaa.org/doi/abs/10.2514/3.8610 "Concepts and status of laser-supported rocket propulsion"], ''Journal of Spacecraft and Rockets'', Vol. 21, No. 1 (1984), pp. 70-79.
https://dx.doi.org/10.2514/3.8610</ref><ref>{{cite book | chapter-url=http://arc.aiaa.org/doi/abs/10.2514/5.9781600865633.0129.0148 | doi=10.2514/5.9781600865633.0129.0148 | chapter=Laser Thermal Propulsion | title=Orbit-Raising and Maneuvering Propulsion: Research Status and Needs | year=1984 | pages=129–148 | isbn=978-0-915928-82-8 }}</ref> 
In 1992, the late [[Jordin Kare]] proposed a simpler, nearer-term concept with a rocket containing liquid hydrogen.<ref>Kare, J. T. (1992). Development of Laser-Driven Heat Exchanger Rocket for Ground to-Orbit Launch. Washington, DC International Astronautical Federation Congress. {{bibcode|1992wadc.iafcQY...K}}</ref> The propellant is heated in a heat exchanger that the laser beam shines on before leaving the vehicle via a conventional nozzle. This concept can use continuous beam lasers, and the semiconductor lasers are now cost-effective for this application.<ref>{{cite web | url=http://www.niac.usra.edu/files/library/meetings/fellows/mar04/897Kare.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.niac.usra.edu/files/library/meetings/fellows/mar04/897Kare.pdf |archive-date=2022-10-09 |url-status=live | title=Modular Laser Launch Architecture: Analysis and Beam Module Design | work=niac.usra.edu | date=March 24, 2004 | access-date=July 19, 2016 | author=Jordin T. Kare}}</ref><ref>{{cite web|url=http://www.jkare.com/VG_HX_4-29-SAS.pdf |access-date=August 11, 2010 |url-status=dead |archive-url=https://web.archive.org/web/20110724205642/http://www.jkare.com/VG_HX_4-29-SAS.pdf |archive-date=July 24, 2011|title=HX Laser Launch: It's Steamship Time}}</ref>

=== Microwave thermal rocket ===
{{Main|Thermal rocket}}
In 2002, [[Kevin L. Parkin|Kevin L.G. Parkin]] proposed a similar system using microwaves.<ref name="parkin" /><ref>Parkin, K. L. G., et al. (2002). A Microwave-Thermal Thruster for Ultra Low-Cost Launch of Microsatellites, Jet Propulsion Center, California Institute of Technology.</ref><ref>{{cite news| url=http://www.foxnews.com/scitech/2011/01/25/nasa-exploring-lasers-beams-zap-rockets-outer-space/ | work=Fox News |first=Prachi |last=Patel | title=NASA Exploring Laser Beams to Zap Rockets Into Outer Space | date=25 January 2011 |url-status=dead |archiveurl=https://web.archive.org/web/20110127183155/http://www.foxnews.com/scitech/2011/01/25/nasa-exploring-lasers-beams-zap-rockets-outer-space/ |archivedate=2011-01-27}}</ref><ref>{{cite magazine|url = http://www.scientificamerican.com/article/microwave-powered-rockets-would-slash-cost-of-reaching-orbit/|title = Microwave-Powered Rockets Would Slash Cost of Reaching Orbit|date = December 1, 2015|magazine = Scientific American |doi=10.1038/scientificamerican1215-33}}</ref> In May 2012, the DARPA/NASA Millimeter-wave Thermal Launch System (MTLS) Project<ref>{{Cite book|title=Microwave Thermal Propulsion - Final Report|last=Parkin|first=Kevin|publisher=NASA|year=2017|hdl = 2060/20170009162}}</ref> began the first steps toward implementing this idea. The MTLS Project was the first to demonstrate a millimeter-wave absorbent refractory heat exchanger, subsequently integrating it into the propulsion system of a small rocket to produce the first millimeter-wave thermal rocket. Simultaneously, it developed the first high-power cooperative target millimeter-wave beam director and used it to attempt the first millimeter-wave thermal rocket launch. Several launches were attempted, but problems with the beam director could not be resolved before funding ran out in March 2014.

=== Mass Beam Systems ===
Aerospace and mechanical engineer [https://samueli.ucla.edu/people/artur-davoyan/ Artur Davoyan] has been [https://web.archive.org/web/20240720072227/https://www.nasa.gov/general/pellet-beam-propulsion-for-breakthrough-space-exploration/ funded by NASA] to study a pellet-beam system that would propel one ton payloads to 500 AU in under 20 years.

Nordley and Crowl propose vast solar arrays built by self-replicating robots placed at the Sun-Venus equilateral Lagrange points, capable of generating beams in the hundreds of petawatt range. With such technologies, craft could be driven to relativistic speeds, capable of reaching nearby stars in decades.