Sailing with E-Sail to the outer planets

Jupiter 5.2 AU from the Sun Payload Travel time Entry Speed 500 kg 1.0 yr. 53 km/s 1000 kg 1.6 yr. 49 km/s 1500 kg 2.5 yr. 47 km/s Neptune 30 AU from the Sun Sailing with E-Sail to the outer planets Sini Merikallio, Pekka Janhunen and Petri Toivanen, Finnish Meteorological Institute Jean-Pierre Lebreton, European Space Research and Technology Center ESTEC Payload Travel time Entry Speed 500 kg 4.6 yr. 38 km/s 1000 kg 8.0 yr. 28 km/s 1500 kg 14.9 yr. 23 km/s Outer planets Accurate knowledge of the atmospheric composition of the outer planets Jupiter, Saturn, Uranus and Neptune could be used to test different solar system formation theories. To do this, the scientist wants to look at trends in the composition of the accretion disk from which the planets formed, which implies that one should measure the atmospheres of all the outer planets. Thus far only Jupiter’s atmosphere To gain the maximum science output for ixed cost, one could has been probed. That was done by Galileo spacecraft in 1995, which dropped a manufacture four identical atmospheric probes and send them towards all 340 kg probe in the Jovian atmosphere. The probe survived the violent reentry at 47 km/s and transmitted data for almost an hour until inally crushed by the pressure of the deeper atmosphere. It took six years for the Galileo lander and Electric Solar Wind Sail All at once? orbiter to get into the vicinity of Jupiter. Now with E-sail technology, travel times the giant planets. Designing spacecraft is expensive, but building identical reduces unit costs. The probes could be launched together or separately as opportunities The Electric Solar Wind Sail (E-sail) is a new propulsion method that uses long, thin to outer planets are signiicantly shorter than with traditional techniques and at the and positively charged tethers to turn solar wind momentum lux into spacecraft same time launch masses are reduced, which decreases the mission cost. Whereas thrust. The E-sail was invented in 2006 and is currently under development and traditional missions need to carefully select their launch date within the so-called launched since in the solar wind the propellantless E-sail takes care of the funded e.g. by the European Union’s Seventh Framework Programme for Research launch window, the E-sail probe could be launched at any time as there is no need acceleration. and Technological Development, EU FP7. According to current estimates, the E-sail is to gather extra speed by suitable planetary ly-by’s. arise. It does not matter into which Earth escape orbit the probe is 2-3 orders of magnitude more eficient than traditional propulsion methods (chemical rockets and ion engines) in terms of produced lifetime-integrated impulse per propulsion system mass. The force of an E-sail is inversely proportional to the distance from the sun (F α 1/r) Saturn 9.6 AU from the Sun Payload Travel time Entry Speed 500 kg 1.7 yr. 37 km/s 1000 kg 2.8 yr. 30 km/s 1500 kg 4.6 yr. 27 km/s while, in comparison, the force produced by a photonic solar sail is F α (1/r2) . Thus the E-sail has particular potential for outer solar system missions. Uranus 19 AU from the Sun Payload Travel time Entry Speed E- sail needs no fuel, it only needs a modest amount of electric power that can be 500 kg 3.1 yr. 36 km/s easily obtained from solar panels. This allows quite small total spacecraft mass 1000 kg 5.3 yr. 25 km/s compared to the thrust. A baseline E-sail has 100 tethers, each of which is 20 km long. 1500 kg 9.6 yr. 20 km/s The thrust produced by such an E-sail is 1 N at Earth’s distance from the Sun (1 AU). The travel times and entry speeds on this poster have been calculated assuming a baseline 1 N sail. Ways are foreseen to enhance the thrust by further technology development in the future. www.electric-sailing.i Images courtesy of NASA and ESA, design: Sini.Merikallio@fmi.i