Benefits of In Situ Resources Utilization (ISRU) for propellant production in a rapid crewed mission to Mars

A way to mitigate the risks of a crewed mission to Mars is reducing the time of transfer to and from the planet, with the downside of a meaningful increase in the mass required to achieve faster travel. In this work it was considered the possibility of producing the propellant needed for the return journey for such a rapid crewed mission on the surface of Mars, taking advantage of In Situ Resources Utilization (ISRU) technology. Although ISRU is typically considered as way to reduce mass when designing a mission to Mars, it was not clear whether this would be the case when the quantity of propellant to produce is very large. Through numerical analysis the Initial Mass in Low Earth Orbit (IMLEO) was computed both for an ISRU fitted spacecraft and a full tank of propellant of comparable size, the numbers were then compared with each other. In particular to estimate the mass of propellant needed for the ISRU spacecraft it was needed to study both ascent and Entry, Descent and Landing (EDL). Moreover for both cases the interplanetary transfer was modeled using a modified rocket equation which takes into account burn losses and jettison of depleted propellant tanks. Five modern and future propulsive systems were considered and for all of them the employment of ISRU resulted in a lower IMLEO, suggesting that even with less optimistic hypothesis this might be a successful approach. On the other hand potential buckling during EDL requires additional work on the lander structure.