Electric propulsion: a key to success in the satellite market

Pro.qrammes

& Products

I Electric Propulsion: 1a Key to Success i in the Satellite Market Jean-FranGois

PIERRE

Plasma thrusters such as the PPS 7350 developed by Snecma and manufactured af the company’s Melun-Villcrfoche plant, will significantly reduce the weight of satellite platforms, enabling them to carry larger payloads. In other words, this technology offers CYdecisive edge in the commercial battle between satellite manufacturers.

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aving logged extensive inorbit experience on Russian satellites since the 197Os, plasmapropulsion is set to begin its commercialcareer in the West. First, however, two SnecmaPI’S 1350 thrusters (figure 1) will be qualified in orbit on Stentor,the Frenchtelecomstechnologydemonstration satellite, which will alsobe fitted with two SPT 100 stationary plasma thrustersbuilt by the Russiancompany Fakel.The EuropeanspacecraftSmart-l, designed for a lunar observation mission,will also be equipped with a ITS 1350. On the commercial side, the first operator to chooseSnecma’splasma propulsionsolutionis SES,for the Astra 1K geostationary telecommunications satellite. Snecma plasma propulsion systemsare alsoon the short list for the “contract of the century”, to equip the 84 satellites in the SkyBridge multimedia constellation, being built by Alcatel Spaceasprime contractor.

type of propulsion technology. Europeanmanufacturersarealreadyoffering telecom satellites equipped with Snecma plasma propulsion systems, becausethe weight savingsallowsthem to give customersa muchlargernumber of transmissionchannels.For example, a plasmapropulsion systemtranslates into weight savings of about 800 kilogramson a 3 500 kg geostationary telecommunications satellite with a designlife of 15years.This is due to the muchhigher specificimpulseofferedby plasmapropulsion,in comparisonwith the bipropellant chemical thrusters

Significant commercial advantages Other applications will undoubtedly follow in the near future, becauseof the major weight savings offered by this

Figure 1. PPS 1350 Plasma (Dot. SNECMA) AIR

Thruster.

& SPACE

generally ,used on geostationary satellites. However, plasmapropulsion will only reach its full potential with the development of high-power thrusters capable of performing orbital transfer duties relatively quickly, thus totally eliminating the need for chemical propulsionsystems.

How plasma propulsion works Plasmathrusters use electrical energy, instead of the chemical reactions generating thrust on conventional chemicalpropulsion systems,whether mono- or bipropellant. In a plasma propulsion system,electrically charged particles(ionsof xenon) are accelerated within a plasma,then ejectedat very high speedto generatethrust. The ions arecreatedby bombardingxenonatoms with a stream of electrons; some of theseelectronsareusedto neutralizethe beam leaving the thruster, so that the satellite doesnot take on an electrical charge. Thrusters that operate in this way are called stationary plasma thrusters(figure 2). There are other electric propulsion technologies,such as ion propulsion, which producesthe ions in the same way,but accelerates themin an electrical field generated by grids. In pulsed EUROPE

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Figure 3. PPS Plasma Thruster in firing test. (Dot. SNECMA)

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Figure 2. Stafionary

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plasma propulsion, an electrical arc bombardment,field emissionthrusters, erodes a solid target to generate etc.).The PI’S 1350offersslightly higher particles.Other propulsiontechnologies performancethan the SPT100.Built by use electricalenergy to heat gasesand Fake1 and marketed in Europe by therefore “dope” the chemicalreaction Snecma,within the scopeof the ISTI (e.g.,resistojet,arcjet). joint venture, the SPT 100 has now Stationary plasmapropulsion offers a successfullycompletedsupplementary goodperformancetradeoff. It providesa qualification tests to ensure compatihigh enoughspecificimpulseto ensure bility with Westernstandards. significant fuel savings, along with relatively high thrust sothat maneuvers The relentless race to do not last too long, operationdoesnot demand sophisticatedelectronics,and satisfy market needs enduranceis comparableto the lifespan American satellite-makerHughes, the of commercialsatellites. world leader, had pulled aheadof its Westerncompetitorsby offering the HS PPS 1350 already 601HP platform equipped with the Xenon Ion Propulsion System (XIPS). qualified for Stentor The first satellite of this type, the The PI’S 1350stationaryplasmathruster PanAmSatPAS5, waslaunchedin 1997, was developed by Snecmawith the and five othershave sincefollowed. In financialsupportof Frenchspaceagency 1998,NASA launchedthe DeepSpace1 CNES,and the technicalsupportof Fakel. probe, equippedwith an ion propulsion It hasalreadypassedenvironmentaltests (figure3), andhasloggedthe 4 000hours of operation required for the Stentor satellite.Qualificationwill continueup to 7 000 hours to satisfy the demandsof commercialgeostationarysatellites. The PI’S 1350thruster will be entirely fabricated using Westerntechnologies, while drawing on Russia’s technological heritage and Snecma’s long experience (via SEP,now a division) with electric propulsion technologies startingin the early 1970s(resistojet,ion

system.JapanlaunchedComets,its first satellite equipped with the Melco electric thrusters, in February 1998, following an initial trial on ETS6. Theseinitial orbitalapplications of electric propulsionconfirmedthe advantagesof this technology.The challengenow is to be ready when the growing demandfor more transmission channelsmeansthat manufacturers must absolutely offer electric propulsion on their telecom satellitesto remaincompetitive. Becauseof the potential commercial stakes of this market, a number of initiativesaretakingshape,includingthe developmentof other stationaryplasma thrusters (Boeing and Primex in the United States,Matra Marconi Spacein Europe),andconsolidationof ion thruster . expertise (Hughes,JPL in the United States;DERA and Dasain Europe).The primary success criteriafor thesedifferent initiatives will be the availability of a qualifiedproduct, followedby how well the product meetsmarket requirements for competitiveness andreliability. Snecma’slong-term commitment to plasma propulsion, combined with initial demonstrationsof marketcompetitiveness,augur very well indeedfor a successful commercialcareer. I

Jean-Frayois PIERRE is deputy manager, $3 SNECMA,Satellite Propulsion and Equipment D