Use of a new type of propellant for electric propulsion

Abstract

The present invention relates to the use of natural uranium hexafluoride UF6 as propellant in an electric propulsion system.

Description

[0001] USE OF A NEW TYPE OF PROPELLANT FOR ELECTRIC PROPULSION

[0002] DESCRIPTION

[0003] TECHNICAL FIELD

[0004] The invention relates to the use of a new type of propellant for electric propulsion and, in particular, electric space propulsion.

[0005] Generally speaking, propulsion relies on the exchange of momentum between an ejected material and the propulsion device, the ejected material being able to consist of:

[0006] - hot gases resulting from an exothermic combustion reaction of a propellant comprising a fuel and an oxidizer, these gases being ejected by expansion at high temperature through a nozzle, this scenario corresponding to chemical propulsion; or

[0007] - charged particles from a plasma generated from a propellant, the energy to create the plasma and accelerate the ions of this plasma for ejection being an energy of electrical origin, this scenario thus corresponding to electric propulsion.

[0008] Electric propulsion, also called plasma propulsion or ion propulsion, allows, thanks to a separation between the energy source and the material to be ejected, to achieve a high ejection speed, which thus induces a very low propellant consumption, unlike chemical propulsion. When electric propulsion is used in the space sector and, more specifically, in satellite propulsion, it is thus possible to reduce the mass of the propelled satellites and, thus, their launch cost or, moreover, to extend the duration of a mission and increase its impact. Thus, despite a low level of thrust and lower than that of chemical propulsion, electric propulsion allows gains in capacity and costs and allows the performance of maneuvers and missions that would otherwise be difficult to achieve.

[0009] Currently, electric propulsion is provided primarily and operationally by two relatively similar technologies: electric grid thrusters and Hall effect thrusters. These two technologies differ in the way they generate the electric field that causes ion ejection, the electric field being generated by two polarized grids for electric grid thrusters, and being generated by the combination of a magnetic field and an electrostatic potential difference between an anode and a cathode for electric Hall effect thrusters.

[0010] Different types of propellants can be used in these electric thrusters and, in particular:

[0011] - rare gases, such as xenon, which is used mainly, or krypton or argon;

[0012] - solid propellants, such as iodine, magnesium or zinc.

[0013] Electric propulsion can also be provided, to date but still at the prototype stage, by so-called "electronegative thrusters" which use both positive ions and negative ions for thrust, which typically requires the management of two propellants, one propellant capable of generating positive ions (for example, argon) and one propellant capable of generating negative ions (for example, sulfur hexafluoride) under a similar pressure, the use of two types of propellant however causing excess weight which is detrimental to propulsion performance.

[0014] In view of what already exists, the inventors of the present invention have set themselves the objective of proposing a new propellant which can be used effectively in the context of electric propulsion and, more particularly, of space electric propulsion, as a replacement for the propellants already used in this field and, more precisely, which can be used in all types of electric thrusters, in particular in electronegative electric thrusters, without requiring the use of two separate propellants.

[0015] STATEMENT OF THE INVENTION

[0016] Thus, the invention relates to the use of natural uranium hexafluoride UFe as propellant in an electric thruster and, more particularly, in a space electric thruster.

[0017] The concept of propellant corresponds to the concept known under English terminology

[0018] "propellant" which can also be referred to as propellant gas. Classically, natural uranium hexafluoride corresponds to uranium hexafluoride whose uranium has an isotopic composition comprising a low abundance of light isotopes, and, more specifically, between 0.6% and 0.8% of 235 U.

[0019] Natural uranium hexafluoride as a propellant in electric propulsion has the following advantages:

[0020] - a vapor pressure with a sublimation limit at near-ambient temperature and pressure;

[0021] - much better thrust at fixed power, due to the fact that UFe gas is significantly heavier (352 g / mol) compared to xenon (131 g / mol);

[0022] - temperature-only management of the density of the propelled uranium hexafluoride, due to the fact that the very stable uranium hexafluoride sublimes at normal temperatures, thus allowing its transport in crystallized form and thus no longer involving management of liquefied or cryogenic gases;

[0023] - simplified ground tests with a vacuum in the test chamber obtained by cryogenics and not pumping, the management of uranium hexafluoride being well known to those involved in the nuclear fuel cycle;

[0024] - a possibility of use in all types of electric thrusters and in particular in electronegative electric thrusters, due to the fact that uranium hexafluoride is capable of producing both positive ions (in this case, UFs + ) than negative ions (in this case, F ) during the ionization process; and

[0025] - the possibility of being used for all types of space flights, except those with strong gravitation and, in particular, for space flights intended for a change of orbit, reorientation of a satellite, interplanetary travel, avoidance of objects.

[0026] The invention will now be described with reference to the following example.

[0027] DESCRIPTION OF A PARTICULAR EMBODIMENT

[0028] A successful test was carried out using natural uranium hexafluoride in a Hall effect electric thruster with a power of the order of a kilowatt. Furthermore, the particularly high ionization cross-section can accommodate the wide power range available in Hall effect thrusters on the market.

Claims

CLAIMS 1. Use of natural uranium hexafluoride UFe as propellant in an electric thruster.

2. Use according to claim 1, wherein the electric thruster is a space electric thruster.