Editing Hypergolic propellant (section)

=== Disadvantages ===
Relative to their mass, traditional hypergolic propellants possess a lower [[Heat of combustion|calorific value]] than cryogenic propellant combinations like LH<sub>2</sub>/LO<sub>2</sub> or [[Methane#Fuel|LCH<sub>4</sub>]]/LO<sub>2</sub>.<ref name=NIST>{{cite book |title=NIST Chemistry WebBook |date=2021 |publisher=NIST Office of Data and Informatics |series=NIST Standard Reference Database Number 69 |doi=10.18434/T4D303 |last1=Linstrom |first1=Peter }}</ref> A launch vehicle that uses hypergolic propellant must therefore carry a greater mass of fuel than one that uses these cryogenic fuels.

The [[corrosivity]], [[toxicity]], and [[carcinogen]]icity of traditional hypergolics necessitate expensive safety precautions.<ref>{{Internet Archive|NASA_NTRS_Archive_20090029348|A Summary of NASA and USAF Hypergolic Propellant Related Spills and Fires }}</ref><ref>{{YouTube|id=Zha9DyS-PPA|title="Toxic Propellant Hazards"}}</ref> Failure to follow adequate safety procedures with an exceptionally dangerous UDMH-nitric acid propellant mixture nicknamed [[Devil's venom|"devil's venom"]], for example, resulted in the deadliest rocketry accident in history, the [[Nedelin catastrophe]].<ref>{{citation|url=http://www.spacesafetymagazine.com/space-disasters/nedelin-catastrophe/historys-launch-padfailures-nedelin-disaster-part-1/|title=The Nedelin Catastrophe, Part 1 |date=28 October 2014 |url-status=live |archive-date=15 November 2014 |archive-url=https://web.archive.org/web/20141115205657/http://www.spacesafetymagazine.com/space-disasters/nedelin-catastrophe/historys-launch-padfailures-nedelin-disaster-part-1/}}</ref>