Mars Ascent Trajectory for Rendezvous Operations into Elliptical Orbit
- Paper number
IAC-06-C1.P.4.04
- Author
Mr. Emanuele Di Sotto, DEIMOS Engenharia, Portugal
- Coauthor
Mr. Juan-Carlos Bastante, DEIMOS Space, Spain
- Coauthor
Mr. Christian Philippe, European Space Agency (ESA)/ESTEC, The Netherlands
- Year
2006
- Abstract
In the frame of the Mars Sample Return mission a preliminary design has been performed in the context of ESA-Aurora programme in which a circular orbit around Mars is proposed for the orbiter vehicle. The orbiter and the Mars Ascent Vehicle (MAV) will carry out autonomous rendezvous operations in this orbit to transfer the collected sample from one vehicle to the other. The choice for the circular orbit has been derived from the existing European technology for autonomous rendezvous operations that have been studied and developed since the late eighties. However, it appears worth investigate also the elliptical orbit scenario for several advantages provided to the overall mission design. The elliptic orbit represents a very appealing solution due the possibility of saving considerably propellant mass at least in two of the most critical manoeuvres to be faced with the Orbiter propulsion system: Target Orbit Acquisition (TOA) manoeuvre and the Mars Escape manoeuvre (ME). Moreover, elliptical orbit would allow saving DV also for the rendezvous manoeuvre foreseen during the intermediate range operations. In this phase, the most demanding manoeuvre is the one dedicated to bring the two vehicles into coplanar obits, due to eventual difference in orbital inclinations. An elliptical orbit would permit carrying out this manoeuvre with a substantial benefit for the required propellant mass. The main system driver when defining the proper elliptical orbit, where injecting the Orbiter vehicle and carry out rendezvous operations with the MAV, is represented by the MAV performances in attaining this kind of orbit. In this work we propose ascent strategy for the current MAV configuration aiming at attaining the proper Mars elliptical orbit that minimize the orbiter propellant consumption and fulfil the operational constraints. The proposed strategy is driven by the choice of equipping the MAV with a re-startable upper stage. This allows introducing a coast arc in the exo-atmospheric steered flight that considerably increases the vehicle performance. Vehicle steering law has been computed for both the exo-atmospheric propelled arcs in order to maximise the payload mass while attaining the required elliptical orbit. This has been performed using the classical “primer vector” formulation that was originally proposed by Lawden. The problem is formulated in terms of parameters optimisation where the guidance law is completely characterised by the proper choice of the initial adjoints variable at the beginning of each propelled arc. Thrusting and coasting periods are also regarded as optimisation variables. The resulting trajectory fulfils typical aerothermal/dynamic constraints such as: dynamic pressure peak, heat flux peak, and maximum aerothermal flux after fairing jettisoning. The results show that elliptical orbits of more that 1000 km apocenter altitude are attainable through an intermediate ballistic arc. This turns in more than 100 kg propellant mass (conservative assessment) saved for the orbiter overall mass budget. It has been shown that this result is very sensitive to the dynamic pressure peak and a characterisation of the attainable elliptical orbit with respect to this constraint has been provided. The work presented in this paper was done under an ESA/ESTEC contract.
- Abstract document
- Manuscript document
IAC-06-C1.P.4.04.pdf (🔒 authorized access only).
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