How shall we go to Mars? A review of mission scenarios

Abstract

Various scenarios for manned Mars missions are reviewed, and four mission classes-opposition, conjunction, fast-transfer conjunction, and split sprint-are identified as contenders for the initial missions. These four mission classes are then compared with regard to three factors: 1) reduced gravity effects, 2) exposure to space radiation, and 3) initial mass in Earth orbit. It is concluded that the choice of mission scenario depends to a large extent on the amount of physical deconditioning caused by long-term exposure to the 3/8 Earth gravity environment of the Martian surface. Although important, exposure to space radiation is not a clear discriminator because the various scenarios yield roughly comparable radiation doses and even with conservative assumptions, none of them, significantly exceed the National Council on Radiation Protection and Measurement limits. If it is assumed that 3/8 Earth gravity is as harmful as zero gravity, the only acceptable mission scenario is the split sprint, which is truly attractive only when a high specific impulse propulsion system, such as nuclear thermal propulsion, is used. If, on the other hand, it is assumed that during their stay on the Martian surface the astronauts experience no further deconditioning, the mission scenario of choice is the fast-transfer conjunction class because of its low radiation doses, short exposure to zero gravity, and low Earth departure masses for either chemical propulsion with aerobraking or nuclear thermal propulsion. a,b D s , H E M P m N n x,y. Nomenclature =factors determined from regression of historical cost data, used in TRANSCOST =blood-forming organ radiation dose, rem =fabrication cost-estimating relationships for stages and propulsion systems, respectively, used in TRANSCOST =corrective factors used in TRANSCOST costestimating relationships to account for technology status, etc. =acceleration due to gravity at Earth's surface, 9.807 m/s 2 =development cost-estimating relationships for stages and propulsion systems, respectively, used in TRANSCOST =specific impulse, s =vehicle stage or propulsion system dry mass, used in TRANSCOST, kg =vehicle or payload mass, see Eqs. (1-8), kg =number of vehicle stages, used in TRANSCOST =number of identical units (e.g., engines) per stage, used in TRANSCOST =entry velocities at Mars and Earth, respectively, km/s =factors determined from regression of historical cost data, used in TRANSCOST =e l.05DV/gls PjSee Eq. (5) AV = velocity increment, km/s y =aerobrake mass factor, (m^ +m p/L )/m p/L K -structural mass factor, (m s +m p )/m p \j/ = overall mass factor for a propulsive stage, m/m p/L , see Eq. (6) Subscripts AB =aerobrake E =Earth return ERM = Earth return module HAB = habitation module M =Mars arrival MEM =Mars excursion module MID = midcour se burn p/L = pay load p =propellant s = structure TMI =trans-Mars injection 1 = Earth departure 2 = outbound midcourse A V 3 =Mars arrival 4 =Mars departure 5 = Earth return

Cooperative evolutionary algorithm for space trajectory optimization

“…Three classes of missions are considered (Walberg 1993;Casalino et al 1998). Conjunction-class missions are minimum-V missions characterized by long trip time (about 1000 days); they comprise two Hohmann-like transfers joined by a long stay on Mars to wait for suitable phasing between the planets to start the return leg.…”

Mission design options for human Mars missions

“…Two major types of human Mars missions have been proposed based upon their interplanetary trajectories and associated Mars stay times, known as conjunction-class (or long-stay) and opposition-class (or short-stay) missions (Walberg 1993). Conjunction-class missions are characterized by long stay times on Mars (order of 400 to 600 days), short in-space durations (approximately one year total for the Earth-Mars and Mars-Earth legs), and relatively small propulsive requirements.…”

Search the Optimal Rendezvous Opportunities for Manned Mars Mission

“…Various mission and trajectory designs have been proposed to achieve the first human mission to Mars [WIL,91], [WAL,93], [LYN,98], [PAT,98]. The chief concern in all proposals is how to minimize the exposure of the crew to the hazardous space environment, while keeping the propellant costs at an acceptable level.…”