enabling technologies and challenges -...

L. Conde, J.M. Donoso, J.L. Domenech-Garret and

E. Del Rio Department of Applied Physics.

Escuela Técnica Superior de Ingeniería Aeronáutica y del Espacio. Univ. Politécnica de Madrid. UPM Spain.

From plasma physics to spacecraft propulsionEnabling technologies and challenges

UPMPlasmaLab

viernes 4 de octubre de 2013

• Low power ion thrusters (plasma sources)• Electron and ion probes (emissive and collecting Langmuir probes, RPA)• RF Electric discharges in communications hardware (multipactor, corona ...)• Electron sources for space applications (cathodes, plasma klystrons, ...)

Members:

Dr. Luis Conde Dr. Jose Manuel Donoso Dr. Juan Luis Domenech Dr. Ezequiel Del RíoMs. Sandra Pilar Tierno (PhD. Student)Mr. Antonio Hernández (Ms. Student)Mr. Jorge González (Ms. Student)

http://plasmalab.aero.upm.es/

Former members:

Mr. Walter Foxworth (Ms. student, now with Busek Co. Inc. USA)Ms. Elena Roibás (PhD, now with the Dept. Aeroelasticity. ETSIA) Mr. Ernesto Criado ( PhD. Student, now with the California University, San Diego)

UPMPlasmaLab


http://plasmalab.aero.upm.es

http://plasmalab.aero.upm.es

T =d

dt(M

s

(t) Vex

)

Msi = mpi +md

Msf = md

�V = Vf

� Vi

=

ZVf

Vi

dV = �Vex

Zmd

mpi+md

dMs

Ms

�V = Vx

ln

✓m

d

+mpi

md

◆mpi

md= e�V/V

ex � 1

Why plasma propulsion in space?

The trust T is the time derivative of momentum

Exhaust velocity of the propellant Total mass of the spacecraft

Decreasing propellant mass

Constant payload mass (dry mass

The mass of propellant required to increment ΔV the rocket speed exponentially decreases when Vex grows

The objective is to increment ΔV = Vf -Vi the velocity of the payload mass md by using the decreasing propellant mass mp(t) expelled with a constant exhaust velocity Vex

(Tsiolkovsky Eq.)

Ms(t) = mp(t) +md


Isp

=Vex

go

�V = Isp

go

ln

✓m

d

+mpi

md

◆

T = Vex

mp

= Isp

go

mp

Isp

=m

p

Vex

mp

go

Isp

=T

mp

go

System Vex (m/s) Isp = Vex / go (s)

SSME (space shuttle) 4,423 (gases) 450

Gridded ion thruster 50.000 (Ion beam) 5.100Hall Ion Thruster (HET) 10.000-30.000 (Ion beam) 1.000-3.000

The specific impulse

Electric charge acceleration is an attractive idea because ions accelerated up to Eb = 1 eV (voltage drop of 1 volt ) reach velocities in the order of Vex ≈105 m/s , much higher than conventional chemical thrusters.

Introducing Isp in seconds as,

Using the previous equation we obtain two equivalent definitions for Isp

The specific impulse allows to compare the efficiency of the different propulsion systems


And how much thrust we obtain? ...

Xenon Acceleration voltage (Vacc)Acceleration voltage (Vacc)Acceleration voltage (Vacc)Acceleration voltage (Vacc)Acceleration voltage (Vacc)Acceleration voltage (Vacc)

Iion (mA) 1 10 100 1.000 1500 10.000

1 0,00165 0,0052 0,00165 0,052 0,064 0,165

5 0,00825 0,0261 0,0825 0,261 0,32 0,825

10 0,0165 0,0522 0,165 0,522 0,64 1,65

50 0,0825 0,2609 0,825 2,61 3,2 8,25

500 0,165 0,523 1,65 5,22 6,39 16,5

100 0,825 2,609 8,25 26,1 31,95 82,5

1000 1,65 5,22 16,5 52,18 63,9 165

1500 2,48 7,83 24,75 78,27 9.586 247,5

T =

r2M

i

eIion

pVacc

The values of ideal thrust in this table are in mN


Different concepts and configurations

Hollow cathode(neutralizer)

Plasma stream of accelerated ions

electrons and neutrals

Ionization chamber

Hall effect thruster Gridded electrostatic thruster

Hollow cathode(neutralizer)

Plasma stream of accelerated ions

electrons and neutrals

Ionization chamber

Ion acceleration by ExB fields Ion acceleration by a set of metallic grids, essentially static.


The PPS 1350 based in the original Fakel SPT 100. Four Astrium communication satellites are now in orbit equipped with these modules composed of two redundant HET thrusters. Few missions will be equipped with gridded electrostatic engines as Artemis or Beppi Colombo.

Some commercial propulsion systems

There exist on going efforts to reduce the size, electric power and gas consumption of these systems. As the 500 g mini HT100 from Alta (Italy).

www.alta-space.com

Mini Hall Thruster HT-100

HT-100 is a small, low-power Hall Effect Thruster (HET) designed to perform orbit control

tasks on micro-spacecraft and attitude control tasks on mini-satellites.

HT-100 firing in Alta IV-4 facility

HT-100 is the smallest and lowest power HET ever developed in Europe, whose

performance and characteristics represent the state-of-the-art of this technology.

The HT-100 thruster unit is fully based on Italian know-how and technology, as are all

of the key sub-system components. If required, the sub-system can be offered in an ITAR-

free version.

HT-100 scheme (left) and HT-100 mounted on Alta thrust balance (right)

PPS redundant HETpropulsion system Gridded electrostatic thruster

T5 from Quinetic Inc. UK

miniHT 100 from Alta (Italy)

A comprehensive review where most available systems are discussed; C. Charles. Plasmas for spacecraft propulsion. J. Phys. D: Appl. Phys. 42 163001-1,18 (2009)


The plasma propulsion foreseen future

Space waste and orbiting debris is one of the main concerns of space industry. In a nearby future legislations will bind satellite builders to provide the orbiters with the means to abandon the orbit after the mission.

Advantages• Powered by solar panels.• Propelled by chemically innert gases (xenon) of easy long term stowage.• High efficiency: large values of the specific impulse allows long term missions.

Drawbacks• Only operate on the outer space. • Low levels of thrust, in the order of 1-100 mN (space manoeuvres take long!)• Require of neutral gas mass flow rates in the order of tens of sccm (standard cubic

centimeters by minute). • The large electric power (typically few kW) required limits the use of these systems

to heavy satellites with large solar panels (up to 30 kW).

Our target: The micro-spacecrafts with masses in the range 10–100 Kg have reduced payload weights and the available electric power lies well below the current propulsion requirements. This requires low electric power consumption, small size and weight.

The plasma propulsion offers considerable advantages for applications as in in orbit station keeping, long-term geostationary satellites and deep space missions or planetary probes.


The dramatic effect of ion beam neutralization, …

The neutralizer wire emits large thermionic electron currents for temperatures over Tnh = 2400 K (Inh = 1.01 A) and this electron current breaks the space charge allowing an outgoing ion flux from the discharge chamber.

This distant collecting Langmuir probe Langmuir probe is placed 60 cm away from the acceleration grid.

Level of noise: Probe currents below 10-2 mA

The electron emission neutralizes the ion space charge. The ion-electron plasma expands from the

thruster and fills the vacuum tank.

Low thermionic electron emission: The ions could not flow out from the discharge

chamber. The plasma density is very low.


First design: the plasma properties along the Z axis, …


Future work and conclusions

• Our gridded thrusters would help to precision positioning of medium sized satellites (roughly below 100 Kg) and/or space waste control.

• The performances are similar to exiting models but using much lower electric power consumption (in the order of 150 W or below).

• Eventual demonstration flight of space waste control with small scientific or expandable small satellites.

• The future developments will require of industrial partnership. The required budget and prototypes production are beyond the scope of small scale scientific grants. The vacuum facility needs to be upgraded for testing.

• The electron production for either primary plasma production and neutralization revealed as a critical issue. More involved cathodes made of porous tungsten, iridium alloys and/or lanthanum hexaboride will be tested. Advanced materials based based carbon nanotubes would provide higher electron current densities: We are open to possible collaborations with groups from material science.

• The determination of the actual trust levels as well as the properties of the ion energy spectra using an advanced RPA are on the way.


Acknowledgements

This work was funded by the Ministerio de Ciencia e Innovación of Spain under Grants numbers ENE2010-21116-C02-01 and ENE2010-21116-C02-02

THANK YOU FOR YOUR INTEREST


enabling technologies and challenges -...

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