Initial Mass In Low Earth Orbit Research Articles

Mission analysis for Earth to Mars-Phobos distant Retrograde Orbits

This paper focuses on the trajectory design for missions destined to explore Mars and/or Phobos departing from Low Earth Orbit (LEO) and arriving into a Mars-Phobos Distant Retrograde Orbit (DRO). Lunar DROs are also briefly explored as an alternative departure location. A Mars-Phobos DRO is a relatively stable environment which would make both the surfaces of Mars and Phobos available for a reasonable propellant expenditure. This paper presents the methodology used to compute LEO to Mars-Phobos DRO trajectories and results regarding required C3 at launch, v∞ at arrival, Time-of-Flight (TOF), and total ΔV for various Mars-Phobos DROs using full ephemeris planetary data. The results show that propellant-optimal trajectories from LEO to a specified Mars-Phobos DRO could be used as a staging location between Mars and Phobos. Assuming that refueling is available at the targeted DRO, LEO to Low Mars Orbits (LMO) trajectories would have higher total ΔV due to the additional stop at the Mars-Phobos DRO. However, the aformentioned trajectories would have lower Initial Mass in LEO (IMLEO) and thus a lower gear ratio thanks to the added “pit stop” located at the given DRO. This results in a lower overall spacecraft dry mass that needs to be launched into space from Earth's surface.

Earth-Mars transfers through Moon Distant Retrograde Orbits

This paper focuses on the trajectory design which is relevant for missions that would exploit the use of asteroid mining in stable cis-lunar orbits to facilitate deep space missions, specifically human Mars exploration. Assuming that a refueling “gas station” is present at a given lunar Distant Retrograde Orbit (DRO), ways of departing from the Earth to Mars via that DRO are analyzed. Thus, the analysis and results presented in this paper add a new cis-lunar departure orbit for Earth-Mars missions. Porkchop plots depicting the required C3 at launch, v∞ at arrival, Time of Flight (TOF), and total ΔV for various DRO departure and Mars arrival dates are created and compared with results obtained for low ΔV Low Earth Orbit (LEO) to Mars trajectories. The results show that propellant-optimal trajectories from LEO to Mars through a DRO have higher overall mission ΔV due to the additional stop at the DRO. However, they have lower Initial Mass in LEO (IMLEO) and thus lower gear ratio as well as lower TOF than direct LEO to Mars transfers. This results in a lower overall spacecraft dry mass that needs to be launched into space from Earth's surface.

Campaign-level dynamic network modelling for spaceflight logistics for the flexible path concept

This paper develops a network optimization formulation for dynamic campaign-level space mission planning. Although many past space missions have been designed mainly from a mission-level perspective, a campaign-level perspective will be important for future space exploration. In order to find the optimal campaign-level space transportation architecture, a mixed-integer linear programming (MILP) formulation with a generalized multi-commodity flow and a time-expanded network is developed. Particularly, a new heuristics-based method, a partially static time-expanded network, is developed to provide a solution quickly. The developed method is applied to a case study containing human exploration of a near-Earth object (NEO) and Mars, related to the concept of the Flexible Path. The numerical results show that using the specific combinations of propulsion technologies, in-situ resource utilization (ISRU), and other space infrastructure elements can reduce the initial mass in low-Earth orbit (IMLEO) significantly. In addition, the case study results also show that we can achieve large IMLEO reduction by designing NEO and Mars missions together as a campaign compared with designing them separately owing to their common space infrastructure pre-deployment. This research will be an important step toward efficient and flexible campaign-level space mission planning.

Affordable Mars Exploration Architectures: Applying Systems From The Commercial Development Of Space

This paper discusses the possibility of leveraging systems concepts and technologies needed for the commercial development of space in innovative, affordable human Mars exploration architectures. Since the late 1980s, various space agencies, industry and university groups have examined a diverse set of human Mars exploration options. In the United States, the 1989 Space Exploration Initiative (SEI) initiated a continuing series of studies and assessments of options for human exploration. Typically, these studies have focused first on the exploration mission itself and have attempted to optimize key mission metrics—such as the initial mass in low Earth orbit (IMLEO)—through the use of government-developed systems. In light of these concepts, technology needs have typically been identified. Occasionally, potential secondary value of these technologies to terrestrial and space applications has been assessed. An alternative approach might involve a consideration of commercial investments might best be leveraged in exploration missions. Such an approach might begin by determining what technologies and systems concepts are needed to enable the robust commercial development of space, and then attempt to use these technologies and concepts in devising human exploration of Mars scenarios; an approach of this type is presented here. This paper examines a variety of prospective commercial space developments—ranging from near-term plans to far-term opportunities—and draws from these a “tool-kit” of potential systems and technologies that might be applied in constructing a more affordable Mars exploration mission architecture. A notional scenario for applying commercial space development technology and systems in a Mars architecture is described. The paper concludes by comparing and contrasting some of the relative benefits of the two approaches and suggests that—if commercial space development is a viable goal—such an approach may substantially strengthen support among international and US policy-makers for human exploration missions. The paper includes various graphs, tables and conceptual renderings of potential commercial space and human exploration approaches.

Influence of interplanetary trajectory selection on Earth atmospheric entry velocity of Mars missions

Many current manned Mars mission studies are using low lift-to-drag ratio vehicles to aerobrake at both Mars and Earth. This paper will demonstrate that if entry velocity constraints are incorporated into the interplanetary analysis of aerobraking Mars missions, more opportunities can be achieved for only a small increase in initial mass in low-Earth orbit (IMLEO). These additional opportunities result from varying the initial launch date and the encounter dates and possibly using a powered Venus swingby on either the inbound or outbound transfer. This paper not only presents unconstrained entry velocity missions but also includes results for entry velocities below 12.5 and 14 km/s on Earth return and between 6.0-8.5 km/s at Mars arrival. The results indicate that, regardless of the Mars entry velocity range selected, an Earth entry velocity below 14 km/s is easily attainable for a minimal IMLEO increase. Although there are fewer 12.5 km/s Earth entry velocity missions possible, both Mars entry velocity constraint cases have over 50 percent of their missions requiring a negligible IMLEO increase.