Editing Tripropellant rocket (section)

== Simultaneous burn ==
Simultaneous tripropellant systems often involve the use of a high energy density metal additive, like [[beryllium]] or [[lithium]], with existing bipropellant systems. In these motors, the burning of the fuel with the [[Oxidizing agent|oxidizer]] provides [[activation energy]] needed for a more energetic reaction between the oxidizer and the metal. While theoretical modeling of these systems suggests an advantage over bipropellant motors, several factors limit their practical implementation, including the difficulty of injecting solid metal into the [[thrust chamber]]; [[heat]], [[mass]], and [[momentum]] [[transport phenomena|transport]] limitations across [[Phase (matter)|phases]]; and the difficulty of achieving and sustaining [[combustion]] of the metal.<ref name="Zurawski">{{cite web |last1=Zurawski |first1=Robert L. |title=Current Evaluation of the Tripropellant Concept |url=https://ntrs.nasa.gov/citations/19860018652|website=ntrs.nasa.gov |publisher=NASA |access-date=14 February 2019 |date=June 1986}}</ref>

In the 1960s, Rocketdyne test-fired an engine using a mixture of liquid lithium, gaseous [[hydrogen]], and liquid [[fluorine]] to produce a [[specific impulse]] of 542 seconds, likely the highest measured such value for a chemical rocket motor.<ref name="Ignition">{{Cite book |last1=Clark |first1=J. D. |author1-link=John Drury Clark|url=https://archive.org/details/ignitioninformal0000clar |title=Ignition! an informal history of liquid rocket propellants |last2=Asimov |first2=Isaac |date=1972 |publisher=Rutgers University Press |isbn=978-0-8135-0725-5 |pages=[https://archive.org/details/ignitioninformal0000clar/page/188 188]-189 |url-access=registration}}</ref> Despite the high specific impulse, the technical difficulties of the combination and the hazardous nature of the propellants precluded further development.<ref>{{Citation |title=The Best Performing (and most dangerous) Chemical Rocket Ever Tested: Rocketdyne Tripropellant | date=25 February 2024 |url=https://www.youtube.com/watch?v=KX-0Xw6kkrc |access-date=2024-02-28 |language=en}}</ref>