Editing Bussard ramjet (section)

==Feasibility==
Since the time of Bussard's original proposal, it has been discovered that the region surrounding the [[Solar System]] has a much lower density of hydrogen than was believed at that time (see [[Local Interstellar Cloud]]). In 1969, John Ford Fishback made an important contribution, describing the details of the required magnetic field.<ref>{{cite journal |last=Fishback |first=J. F. |year=1969 |title=Relativistic interstellar spaceflight |journal=Astronautica Acta |volume=15 |pages=25–35 |bibcode=1969AsAc...15...25F}}</ref> 

In 1978, [[T. A. Heppenheimer]] analyzed Bussard's original suggestion of fusing [[protons]], but found the [[Bremsstrahlung]] losses from compressing protons to [[nuclear fusion|fusion]] densities was greater than the power that could be produced by a factor of about 1 billion, thus indicating that the proposed version of the Bussard ramjet was infeasible.<ref>{{cite journal |first=T.A. |last=Heppenheimer |title=On the Infeasibility of Interstellar Ramjets |journal=Journal of the British Interplanetary Society |volume=31 |page=222 |year=1978|bibcode = 1978JBIS...31..222H }}</ref> However, Daniel P. Whitmire's 1975 analysis<ref name="Whitmire1975">{{cite journal |first=Daniel P. |last=Whitmire |title=Relativistic Spaceflight and the Catalytic Nuclear Ramjet |journal=Acta Astronautica |volume=2 |issue=5–6 |date=May–June 1975 |pages=497–509 |doi=10.1016/0094-5765(75)90063-6 |url=http://www.askmar.com/Robert%20Bussard/Catalytic%20Nuclear%20Ramjet.pdf |bibcode=1975AcAau...2..497W |citeseerx=10.1.1.492.6775 |access-date=2009-08-30 |archive-url=https://web.archive.org/web/20181031134647/http://www.askmar.com/Robert%20Bussard/Catalytic%20Nuclear%20Ramjet.pdf |archive-date=2018-10-31 |url-status=dead }}</ref> indicates that a ramjet may achieve net power via the [[CNO cycle]], which produces fusion at a much higher rate (~10<sup>16</sup> times higher) than the [[proton–proton chain]].{{fact|date=August 2023}}

[[Robert Zubrin]] and Dana Andrews analyzed one hypothetical version of the Bussard ramjet design in 1988.<ref>{{Cite conference|last1=Andrews |first1=D.G. |last2=Zubrin |first2=R.M. |date=1988 |conference=39th [[International Astronautical Congress]], Bangalore|title=Magnetic sails and interstellar travel |article-number=IAF Paper IAF-88-533}}</ref> They determined that their version of the ramjet would be unable to accelerate into the solar wind.{{fact|date=August 2023}}

A 2021 study found that, while feasible in principle, the practical construction of a useful Bussard ramjet would be beyond even a civilization of [[Kardashev scale|Kardashev type II]].<ref>{{cite journal |title=The Fishback ramjet revisited |journal=Acta Astronautica |volume=191 |date=February 2022 |pages=227–234 |first1=Peter |last1=Schattschneider |first2=Albert A. |last2=Jackson |doi=10.1016/j.actaastro.2021.10.039|bibcode=2022AcAau.191..227S |doi-access=free }}</ref><ref name="ars-20220106">{{Cite news |last=Ouellette |first=Jennifer |date=January 6, 2022 |title=Study: 1960 ramjet design for interstellar travel—a sci-fi staple—is unfeasible |url=https://arstechnica.com/science/2022/01/study-1960-ramjet-design-for-interstellar-travel-a-sci-fi-staple-is-unfeasible/ |url-status=live |archive-url=https://web.archive.org/web/20240123142943/https://arstechnica.com/science/2022/01/study-1960-ramjet-design-for-interstellar-travel-a-sci-fi-staple-is-unfeasible/ |archive-date=January 23, 2024 |work=[[Ars Technica]] }}</ref>