Editing Hall-effect thruster (section)

=== Propellants ===

==== Xenon ====
[[Xenon]] has been the typical choice of propellant for many electric propulsion systems, including Hall thrusters.<ref name="auto">{{Cite web|title=Krypton Hall effect thruster for spacecraft propulsion|url=https://www.sciencedaily.com/releases/2011/10/111006084023.htm|access-date=28 April 2021|website=ScienceDaily|language=en}}</ref> Xenon propellant is used because of its high [[atomic weight]] and low [[ionization potential]]. Xenon is relatively easy to store, and as a gas at spacecraft operating temperatures does not need to be vaporized before usage, unlike metallic propellants such as bismuth. Xenon's high atomic weight means that the ratio of energy expended for ionization per mass unit is low, leading to a more efficient thruster.<ref>{{Cite web|title=Hall Thruster Project|url=https://w3.pppl.gov/~fisch/hall_thruster_project4.htm|access-date=28 April 2021|website=w3.pppl.gov}}</ref>

==== Krypton ====
[[Krypton]] is another choice of propellant for Hall thrusters. Xenon has an ionization potential of 12.1298 eV, while krypton has an ionization potential of 13.996 eV.<ref name="lenntech">{{Cite web|title=The elements of the periodic table sorted by ionization energy|url=https://www.lenntech.com/periodic-chart-elements/ionization-energy.htm|access-date=28 April 2021|website=www.lenntech.com}}</ref> This means that thrusters utilizing krypton need to expend a slightly higher energy per mole to ionize, which reduces efficiency. Additionally, krypton is a lighter ion, so the unit mass per ionization energy is further reduced compared to xenon. However, xenon can be more than ten times as expensive as krypton per [[kilogram]], making krypton a more economical choice for building out [[Satellite constellation|satellite constellations]] like that of [[SpaceX]]'s [[Starlink]] V1, whose original Hall thrusters were fueled with krypton.<ref name="auto" /><ref name=":0" />

==== Argon ====
[[SpaceX]] developed a new thruster that used [[argon]] as propellant for their [[Starlink]] V2 mini. The new thruster had 2.4 times the thrust and 1.5 times the specific impulse as [[SpaceX]]'s previous thruster that used krypton.<ref name="sn-20230228" /> Argon is approximately 100 times less expensive than Krypton and 1000 times less expensive than Xenon.<ref>{{cite book |author1=Shuen-Chen Hwang |first2=Robert D. |last2=Lein |first3=Daniel A. |last3=Morgan |date=2005 |title=Kirk Othmer Encyclopedia of Chemical Technology |chapter=Noble Gases |doi=10.1002/0471238961.0701190508230114.a01 |pages=343–383 |publisher=Wiley |isbn=978-0-471-23896-6 }}</ref>

==== Comparison of noble gasses ====
{| class="wikitable sortable wide"
|+ Noble gas properties and cost comparison table
|-
! Gas !! Symbol !! at wt (g/mol) !! ionization potential (eV) <ref name="lenntech" /> !! unit mass per ionization energy 
! reference price<ref>{{Cite web|title=Chemical elements by market price|url=http://www.leonland.de/elements_by_price/en/list|access-date=17 September 2023|language=en}} Using the Reference Price column, as the cost per unit weight values are inconsistent. The table provides dates that appear to be when quotes were obtained, but has links only to generic supplier websites.</ref>
! cost / m³ (€) !! density (g/l) !! cost / kg (€) !! relative to cheapest
|-
!
!
!
!
!
!
!
!
!
!
|-
| [[Xenon]] || Xe || 131.29 || 12.13 || 10.824 || 25 € / l || 25000 || 5.894 || 4241.60 || 1905
|-
| [[Krypton]] || Kr || 83.798 || 14.00 || 5.986 || 3 € / l || 3000 || 3.749 || 800.21 || 359
|-
| [[Argon]] || Ar || 39.95 || 15.81 || 2.527 || $0.12 / ft³ || 3.97 || 1.784 || 2.23 || 1
|-
| [[Neon]] || Ne || 20.18 || 21.64 || 0.933 || € 504 / m³ || 504 || 0.9002 || 559.88 || 251
|-
| [[Helium]] || He || 4.002 || 24.59 || 0.163 || $7.21 / m³ || 6.76 || 0.1786 || 37.84 || 17
|}