electric sail/estcube-1 · 4 some history • magnetic solar wind sail (zubrin and andrews, 1990)...

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Electric sail/ESTCube-1

Pekka Janhunen

Finnish Meteorological Institute

FMI seminar

FMI, October 9, 2013

http://www.electric-sailing.fi

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ContributorsPetri Toivanen, Jouni Envall, Jouni Polkko, Sini Merikallio, Timo Rauhala, Henri Seppänen (Finnish Meteorological Institute), Pekka Salminen (SkyTron, Finland), Edward Haeggström, Jukka Ukkonen, Göran Maconi (Univ. Helsinki, Finland), Sergiy Kiprich (NSC Kharkov Inst. Physics, Ukraine), Hannu Koivisto, Olli Tarvainen, Taneli Kalvas (Univ. Jyväskylä, Finland), Alexander Obraztsov (Univ. Eastern Finland at Joensuu, and Moscow State Univ.), Greger Thornell, Sven Wagner, Johan Sundqvist (ÅSTC, Uppsala, Sweden), Tor-Arne Grönland, Håkan Johansson, Kristoffer Palmer (Nanospace AB, Uppsala, Sweden), Emil Vinterhav (Swedish Space Corporation&ECAPS), Roland Rosta, Tim van Zöst (DLR-Bremen, Germany), Mart Noorma, Viljo Allik, Silver Lätt, Urmas Kvell (Univ. Tartu, Estonia), Giovanni Mengali, Alessandro Quarta, Generoso Aliasi (Univ. Pisa, Italy), Salvo Marcuccio, Pierpaolo Pergola, Nicola Giusti (Alta S.p.A., Pisa, Italy), Giuditta Montesanti (Univ. Roma Tre, Rome, Italy), Jose Gonzalez del Amo, Eduard Bosch-Borras (ESA/ESTEC)


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Contents• History

• Electric solar wind sail

– Physics

– Technology

– Applications

– Projects and roadmap

• Plasma brake

• ESTCube-1 satellite

• Aalto-1 satellite

• Conclusions


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Some history

• Magnetic solar wind sail (Zubrin and Andrews, 1990)

• ESA study on magnetic sail (FMI, 2002-2004)

• Electric solar wind sail idea (Janhunen, 2004)

• E-sail construction principle (Janhunen, 2006)

• Plasma brake for deorbiting (Janhunen, 2010)

• ESAIL FP7 project: E-sail to TRL 4-5 (2011-2013)

• ESTCube-1 satellite: launched on May 8, 2013

• Aalto-1 satellite: planned launch 2014


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The Coulomb drag effect

• A charged wire (or tether) in streaming plasma experiences Coulomb drag

• Both positive and negative polarity can be used; physics is somewhat different

• The utility value was realised starting 2004


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Electric Solar Wind Sail• Uses solar wind for spacecraft propulsion

• Coulomb interaction between solar wind and long, thin, positively charged tethers (10-20 km, 25-50 µm wire, +20-40 kV)

• Up to 1 N thrust (scales ~ 1/r) from 100-200 kg unit

• Power consumption low and scales ~ 1/r²

• Baseline approach uses non-conducting Auxiliary Tethers to stabilise flight without active control

• “Remote Units” at tips contain auxtether reels and spinup propulsion/spin control

Remote UnitAuxiliaryTether

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Plasma simulation of electric sail

(With nominal solar wind parametres at 1 au)

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Approximate thrust formula

V0 = 20 kV tether voltage

V1 = 1 kV solar wind proton energy

Pdyn = ρv² = 2 nPa solar wind dynamic pressure

R = 100 m electron sheath radius

rw = 1 mm effective electric width of tether

==> dF/dz = 500 nN/m thrust per tether length

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E-sail subsystem developmentGeneral design, applications (FMI)

“Flight simulator” (FMI)

Tether manufacture (Univ. Helsinki)

ESTCube-1 (Univ. Tartu) and Aalto-1 (Aalto Univ.) test missions

ESTCube/Aalto small electron gun (Univ. Jyväskylä)

“Remote Unit” (ÅSTC)

Remote Unit gas thruster (Nanospace)

Remote Unit IL-FEEP thruster (Alta)

E-sail trajectory calculation (Univ. Pisa)


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FMI dynamical simulation

Solve Newton's laws for elastic, bending wires

Include E-sail force under real solar wind

Can model manoeuvring by differential potential control

Can test “flight behaviour” of tether rig

→ “Stretched auxtether model” works


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Tether factory


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Tether factory and its products


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Remote Unit prototyping● Remote Unit must hold auxtether reels and

contain spinup/spin control propulsion

● Dry masses: 0.56 kg (cold gas version), 0.86 kg (FEEP version)

● Passed testing in March 2013

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Electric Sail applications• Almost any interplanetary mission faster, cheaper, better

– Only needs solar wind to work

– Thrust direction controllable 0-30° off radial

– Thrust magnitude ~1/r, 100% throttling capability

• Here we'll look into the following:

– Multi-asteroid touring

– Giant planet entry & flyby

– Non-Keplerian orbits

– “Data clippers”

– Asteroid mining


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Multi-asteroid touring mission• E-sail does not consume propellant and can produce

large delta-v (30 km/s/year or even more)

• Enables touring the asteroid belts

• NEO, main belt, Jupiter Trojans

• Flybys: 40-50 days per asteroid

• Rendezvous: 4-6 months per asteroid + proximity ops

• Instrumentation: Remote sensing, penetrator, impactor ...


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Giant planet entry & flyby• E-sail can one-way-boost payloads to outer solar system

at high speed

• Simple possibilities: atmospheric entry, flyby, orbit capture by small/modest chemical burn

• Travel time in years for 1 N E-sail:


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Non-Keplerian orbits• Earth observation:

– Off-Lagrange point solar wind monitoring (space weather forecasting with longer than 1 hour warning time)

– Watching Earth-approaching NEOs and pseudomoons

– High elliptic orbit whose apogee is locked to morning sector

– Various orbits having view to polar regions

• Solar system science:

– Lifted orbit above ecliptic plane (helioseismology of Sun's poles)

– Jupiter aurora study: Stay above Jupiter-Sun Lagrange L1 point: continuous view to Jupiter's polar aurora and in-situ solar wind measurement (for other giant planets as well)


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“Data clippers”• Ability of E-sail to return home is valuable not only for

physical sample return (which is anyway expensive), but also for returning a large volume of science data

• Flash memories can store more data than what could be radioed from distant targets

• “Data clipper” (Joel Poncy/Thales Alenia): a small E-sail spacecraft that returns to Earth's vicinity from distant target, thus delivering the high resolution data


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E-sail for asteroid mining● Asteroid mining can enable qualitatively different space

activity: large assets with asymptotically low €/kg

● Main product categories:

● H2O and other volatiles, for use as impulsive propellant in space

● Platinum group metals, for selling on Earth

● Iron-nickel, for constructions in space (3-D printing..)

● 2013: deepspaceindustries.com, planetaryresources.com

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Enabler of small solar system probes• Presently we launch planetary probes so that the upper

stage kicks to heliocentric transfer orbit

– If one wants to have a Mars probe, one must buy an escape-capable launcher (and then one pays 40 Meur and gets >1 tonne)

– One could add piggyback payloads, but they will all be destined to the same planet, e.g. Mars

– One could use ion engine, but...

• In contrast, any E-sailer can be launched with any escape orbit launcher

– Enables small and cheap planetary/solar system probes


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ESTCube-1 mission

● Estonia's first satellite

● Launched May 8, 2013 with Vega to 670 km orbit

● Will deploy 10 m tether, charge it to 500 V and measure LEO E-sail effect by sync-deltaspin method


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ESTCube-1 status● Satellite was launched in May with incomplete software

● Since then, successful upload of EPS, camera, CDHS s/w

● ACS software still in progress

● Hardware works fine, some redundant components were dysfunctional (one sun sensor, one memory chip)

● About 40% reduction in solar panel power was experienced during first month, but stable afterwards

● We'll start E-sail experiment as soon as ADC s/w ready, hopefully this year

● Already now, ESTCube-1 is great success to its builders


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ESTCube-1 specific features● Everything was designed and made from scratch by

Estonian students

● ESTCube-1 is not only a student satellite, but a student satellite with a serious scientific mission

● ESTCube-1 was delivered and launched 4 months earlier than what was planned only 9 months before the launch


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ESTCube-1 camera works fine


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ESTCube-1 another shot


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Aalto-1 test mission• 3U CubeSat, work led by Aalto University

• Contains identical E-sail payload as ESTCube-1, but with longer tether (100 m)

• Satellite carries also other payloads

• Planned launch 2014


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Electrostatic Plasma Brake

Space debris at LEO is a growing problem

E-sail -like device provides a solution: negatively charged thin tether

At least on paper, it should be an efficient and robust way to deorbit satellites and existing space debris:

- low mass, low power consumption

- thin tethers are safe to satellites


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E-sail roadmap• ESTCube-1 (2013) and Aalto-1 (2014-2015)

– Demonstrate tether outreeling

– Measure E-sail effect in LEO conditions

• CubeSat solar wind test mission (2016)

– Measure E-sail effect in solar wind

– e.g., CubeSat piggybacked to Moon orbit

• Multi-tether device in LEO or in solar wind (2017?)

• ==> Production E-sails and plasma brakes


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Conclusions

• E-sail for interplanetary propulsion

– 1 km of tether made, Remote Unit passed testing

– ESTCube-1: launched from Kourou (May 8, 2013)

– Aalto-1 in 2014

– Solar wind test mission (CubeSat)

– Wide applicability

• Plasma Brake

– For deorbiting satellites

– High technical synergy with E-sail, physics differs slightly


electric sail/estcube-1 · 4 some history • magnetic solar wind sail (zubrin and andrews, 1990)...

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