Editing Antimatter rocket (section)

===Pure antimatter rocket: direct use of reaction products===

[[Antiproton]] annihilation reactions produce charged and uncharged [[pion]]s, in addition to neutrinos and [[gamma ray]]s. The charged pions can be channelled by a [[magnetic nozzle]], producing thrust. This type of antimatter rocket is a '''pion rocket''' or '''beamed core''' configuration. It is not perfectly efficient; energy is lost as the rest mass of the charged (22.3%) and uncharged pions (14.38%), lost as the kinetic energy of the uncharged pions (which can't be deflected for thrust); and lost as neutrinos and gamma rays (see [[Antimatter#Fuel|antimatter as fuel]]).<ref name=AIAA-2003-4696>[http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/38278/1/03-1942.pdf ''How to Build an Antimatter Rocket for Interstellar Missions: Systems level Considerations in Designing Advanced Propulsion Technology Vehicles''] {{webarchive|url=https://web.archive.org/web/20150502002952/http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/38278/1/03-1942.pdf |date=2015-05-02 }} Robert H. Frisbee, AIAA Paper 2003-4696, July 20–23, 2003,</ref>

[[Positron]] annihilation has also been proposed for rocketry. Annihilation of positrons produces only gamma rays. Early proposals for this type of rocket, such as those developed by [[Eugen Sänger]], assumed the use of some material that could reflect gamma rays, used as a [[light sail]] or [[parabolic reflector|parabolic shield]] to derive thrust from the annihilation reaction, but no known form of matter (consisting of atoms or ions) interacts with gamma rays in a manner that would enable specular reflection. The momentum of gamma rays can, however, be partially transferred to matter by [[Compton scattering]].<ref name=AIAA-2001-3231>[http://physicsx.pr.erau.edu/ExoticPropulsion/propulsion2.pdf ''The Antimatter Photon Drive: A Relativistic Propulsion System''] Darrel Smith, Jonathan Webby, AIAA Paper 2001-3231, 2001</ref><ref name=WebbTATRSBCAR>[http://physicsx.pr.erau.edu/ExoticPropulsion/APD/APD%20Word/Thermal.pdf ''Thermal Analysis of a Tungsten Radiation Shield for Beamed Core Antimatter Rocketry''] Jonathan A. Webb</ref>

One method to reach relativistic velocities uses a matter-antimatter GeV gamma ray laser photon rocket made possible by a relativistic proton-antiproton pinch discharge, where the recoil from the laser beam is transmitted by the [[Mössbauer effect]] to the spacecraft.<ref name="AA-20120821">{{cite journal |last=Winterberg |first=F. |title=Matter–antimatter gigaelectron volt gamma ray laser rocket propulsion |date=21 August 2012 |journal=[[Acta Astronautica]] |volume=81 |issue=1 |pages=34–39 |bibcode = 2012AcAau..81...34W |doi = 10.1016/j.actaastro.2012.07.001 }}</ref>

A new annihilation process has purportedly been developed by researchers from the University of Gothenburg, Sweden. Several annihilation reactors have been constructed in the past years{{when|date=November 2024|reason=which past years?}} which attempted to convert [[hydrogen]] or [[deuterium]] into relativistic particles through laser annihilation. The technology was explored by research groups led by Prof. Leif Holmlid and Sindre Zeiner-Gundersen, and a third relativistic particle reactor is currently being built at the University of Iceland. In theory, emitted particles from hydrogen annihilation processes could reach 0.94c and can be used in space propulsion.<ref>{{cite journal |last1=Holmlid |first1=Leif |last2=Zeiner-Gundersen |first2=Sindre |title=Future interstellar rockets may use laser-induced annihilation reactions for relativistic drive |journal=Acta Astronautica |url=https://iopscience.iop.org/article/10.1088/1402-4896/ab1276/pdf  |date=1 October 2020 |volume=175 |pages=32–36 |doi=10.1016/j.actaastro.2020.05.034 |bibcode=2020AcAau.175...32H |doi-access=free |hdl=20.500.11815/2191 |hdl-access=free }}</ref> However the veracity of Holmlid's research is under dispute and no successful implementations have been peer reviewed or replicated.<ref>{{cite conference | title=Comment on 'Ultradense protium p(0) and deuterium D(0) and their relation to ordinary Rydberg matter: a review' 2019 Physica Scripta 94, 075005 | author=Klavs Hansen | year=2022| arxiv=2207.08133 }}</ref>