Trajectory

The Nautilus mission will be launched in May 2025 with a Soyuz on a quasi-direct trajectory to an active main belt asteroid enforced by electrical propulsion. En route to this rendezvous target (currently Ceres) around which Nautilus will orbit for ~1.5 years, the mission will fly-by at least two asteroids. Options with a fly-by of Mars will be further investigated during the assessment phase. The arrival date (April 2031) is set before Ceres reaches its perihelion (Feb 2032), as the pre-perihelion season is the one associated – for now – with activity on this object.

 

The C3 at departure has been adjusted in order to minimize cruise duration (minimizing operational costs) while still allowing for a system margin above 20% on the mass budget. The resulting mission features are:

  • Launched mass 1610kg, including 110kg of adapter
  • C3=11km²/s², Vinf=3.32km/s
  • Launch date: May 7th 2025
  • Maximum usable thrust beneath 1.5AU: 145mN with Isp=4120s
  • Thrust beyond 1.5AU: average value of 75mN (see section 5.5.4.2) with Isp=3710s
  • 297 e+7 N.s total impulse (leading to a need of 3 engines, with 1 additional for redundancy)
  • Only one QinetiQ T6 engine used at a time
  • No Mars fly-by (conservative assumption)
  • Two asteroid fly-by’s on the way to Ceres
  • Arrival close to Ceres on April 16th 2031 at zero Vinf
  • Allowable mass at Ceres arrival: 1160kg
  • Approach phase for Ceres: two months

The perihelion of Ceres will occur on February 13th 2032, leaving ample margins for the Ceres arrival date. To be conservative when sizing the propellant, the mass at Ceres’ arrival includes the dry mass plus a system margin, all of the hydrazine (although part of it will have been consumed on the way), the Xenon to be used in orbit around Ceres as well as a 5% Xenon provision for delta-V uncertainties during the cruise phase.

 

Several iterations have been made for establishing the preliminary trajectory. For each of the iterations, two scientifically sound flyby targets could always be found within reach (e.g., at least one binary target and one peculiar target such as a metallic asteroid). Ultimately, the selection of those targets will depend upon the retained trajectory after the assessment phase. Concerning the trajectory presented here, the two most reachable flyby targets on the way to Ceres would be:

  • Binary asteroid 3034 Climenhaga (flyby in July 2027, at 1.86 AU from the Sun)
  • Metallic asteroid 497 Iva (flyby in December 2027, at 2.02 AU from the Sun)

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Fig. 1: Proposed trajectory