Editing Nuclear pulse propulsion (section)

===''Medusa''===
[[File:MedusaNuclearPropulsionConceptDrawing.png|thumb|left|upright=1.36|Conceptual diagram of a Medusa propulsion spacecraft, showing: '''(A)''' the payload capsule, '''(B)''' the winch mechanism, '''(C)''' the optional main tether cable, '''(D)''' riser tethers, and '''(E)''' the parachute mechanism.]]
[[File:MedusaNuclearPropulsionOperatingSequenceDrawing.png|thumb|right|Operating sequence of the ''Medusa'' propulsion system. This diagram shows the operating sequence of a ''Medusa'' propulsion spacecraft '''(1)''' Starting at moment of explosive-pulse unit firing, '''(2)''' As the explosive pulse reaches the parachute canopy, '''(3)''' Pushes the canopy, accelerating it away from the explosion as the spacecraft plays out the main tether with the winch, generating electricity as it extends, and accelerating the spacecraft, '''(4)''' And finally winches the spacecraft forward to the canopy and uses excess electricity for other purposes.]]

The ''Medusa'' design has more in common with [[solar sail]]s than with conventional rockets. It was envisioned by [[Johndale Solem]]<ref>{{cite book |last=Gilster |first=Paul |title=Centauri Dreams: Imagining and Planning Interstellar Exploration |publisher=Copernicus Books, Atlanta Book Company |year=2004 |isbn=978-0387004365 |page=86 |url={{google books|plainurl=y|id=57HbBwAAQBAJ}} }}</ref> in the 1990s and published in the ''[[Journal of the British Interplanetary Society]]'' (JBIS).<ref>{{cite journal |last=Solem |first=J. C. |title=Medusa: Nuclear explosive propulsion for interplanetary travel |journal=Journal of the British Interplanetary Society |volume=46 |number=1 |pages=21–26 |date=January 1993 |bibcode=1993JBIS...46R..21S |issn=0007-084X}}</ref>

A ''Medusa'' spacecraft would deploy a large sail ahead of it, attached by independent cables, and then launch nuclear explosives forward to detonate between itself and its sail. The sail would be accelerated by the plasma and photonic impulse, running out the tethers as when a fish flees a fisher, generating electricity at the "reel". The spacecraft would use some of the generated electricity to reel itself up toward the sail, constantly smoothly accelerating as it goes.<ref>{{cite journal |last=Solem |first=J. C. |title=Nuclear explosive propulsion for interplanetary travel: Extension of the ''Medusa'' concept for higher specific impulse |journal=Journal of the British Interplanetary Society |volume=47 |number=6 |pages=229–238 |date=June 1994 |bibcode=1994JBIS...47..229S |issn=0007-084X}}</ref>

In the original design, multiple tethers connected to multiple motor generators. The advantage over the single tether is to increase the distance between the explosion and the tethers, thus reducing damage to the tethers.

For heavy payloads, performance could be improved by taking advantage of lunar materials, for example, wrapping the explosive with lunar rock or water, stored previously at a stable [[Lagrangian point|Lagrange point]].<ref>{{cite journal |last=Solem |first=J. C. |title=The Moon and the Medusa: Use of Lunar Assets in Nuclear-Pulse-Propelled Space Travel |journal=Journal of the British Interplanetary Society |volume=53 |number=1 |pages=362–370 |date=2000 |bibcode=2000JBIS...53..362S |url=http://www.jbis.org.uk/paper.php?p=2000.53.362 |access-date=2015-12-02 |archive-date=2019-02-27 |archive-url=https://web.archive.org/web/20190227060241/http://www.jbis.org.uk/paper.php?p=2000.53.362 |url-status=dead }}</ref>

''Medusa'' performs better than the classical Orion design because its sail intercepts more of the explosive impulse, its shock-absorber stroke is much longer, and its major structures are in tension and hence can be quite lightweight. ''Medusa''-type ships would be capable of a [[specific impulse]] of {{convert|50,000|-|100,000|isp|abbr=on}} (500 to 1000&nbsp;kN·s/kg).

''Medusa'' became widely known to the public in the BBC documentary film [[To Mars By A-Bomb (film)|''To Mars By A-Bomb: The Secret History of Project Orion'']].<ref>{{Citation|last=Sykes|first=Christopher|title=To Mars by A-Bomb: The Secret History of Project Orion|date=2003-03-26|url=https://www.imdb.com/title/tt1039992/|type=Documentary|others=Jaromir Astl, Jeremy Bernstein, Arthur C. Clarke, Ed Creutz|publisher=British Broadcasting Corporation |access-date=2021-06-04}}</ref> A short film shows an artist's conception of how the ''Medusa'' spacecraft works "by throwing bombs into a sail that's ahead of it".<ref>Archived at [https://ghostarchive.org/varchive/youtube/20211211/mT4ZdPRADEw Ghostarchive]{{cbignore}} and the [https://web.archive.org/web/20141016072034/http://www.youtube.com/watch?v=mT4ZdPRADEw Wayback Machine]{{cbignore}}: {{Citation|title=The Medusa: An advanced nuclear pulse spacecraft|url=https://www.youtube.com/watch?v=mT4ZdPRADEw|language=en|access-date=2021-06-04|last=Stevens|first=Nick|year=2014}}{{cbignore}}</ref>