**3. Propulsion options**

*Solar System Planets and Exoplanets*

**2.1 Orbital transfer delta-V**

are 9,378 and 22,459 km [2].

**2. Mission design and options**

**192**

**Table 1.**

**Figure 1.**

*OTV delta-V, Phobos and Deimos orbital transfer missions.*

**Mission option High thrust Low thrust** Phobos to Deimos 1.80 1.58 Phobos to areocentric Mars orbit (AMO) 1.61 1.38 Phobos to 100,000 km altitude 2.76 2.99 Deimos to areocentric Mars orbit (AMO) 0.29 0.24 Deimos to 100,000 km 1.54 1.42

Phobos and Deimos exploration and exploitation methods have been studied for many decades: landers, flybys, etc. [6–11]. While landers have been assessed in the past, this chapter will focus on the orbital transfer delta-V requirements and orbital transfer vehicle designs that would allow the 2 moons' exploration and exploitation. The orbital missions are controlled by the delta-V or change of velocity needed for the orbit transfers. Both high-thrust missions and low-thrust missions were assessed. The high-thrust delta-V values were computed with a standard Hohmann transfer Equations [12]. The values for the low-thrust delta-V were calculated using the Edelbaum equation [13]. The nominal semi major axes for Phobos and Deimos

In all cases, the delta-V values are for round trip missions. There are 5 trips that were assessed: Phobos to Deimos, Phobos to areosynchronous Mars orbit (AMO), Phobos to 100,000 km altitude, Deimos to AMO, and Deimos to 100,000 km altitude. **Figure 1** and **Table 1** provide the round trip delta-V for Phobos and Deimos missions. Both high thrust and low thrust delta-V values are presented. Due to the typical gravity losses with high thrust propulsion systems, a 20% delta-V increase

*Orbital transfer mission options (for the high thrust options, the delta-V is increased by 20%).*

High thrust chemical propulsion, using oxygen/hydrogen rocket engines is a natural choice [14]. If indeed water were available on the Martian moons, it would make sense to capitalize on that water resource, and finally producing rocket-purity oxygen and hydrogen.

Electric propulsion systems with either ion or Hall thrusters are potential options. Xenon or other inert gases are the typical choice for such thrusters. Using hydrogen as an electric propulsion propellant with a pulsed inductive thruster (PIT) has also been proposed.

### **3.1 Advanced propulsion options**

Several advanced propulsion options for Martian moon transportation, exploration, and industrialization were investigated. Chemical propulsion and nuclear electric propulsion (NEP) with a range of power levels for Martian orbital transfer vehicles (OTVs) were assessed. Design parameters, vehicle mass scaling equations, and summaries of these analyses are presented; Mass scaling equations were developed for the O2/H2 chemical propulsion and the nuclear electric propulsion systems [14].
