Entry System Options for Human Return from the Moon and Mars

Abstract

Earth entry system options for human return missions from the Moon and Mars were analyzed and compared to identify trends among the configurations and trajectory options and to facilitate informed decision making at the exploration architecture level. Entry system options included ballistic, lifting capsule, biconic, and lifting body configurations with direct entry and aerocapture trajectories. For each configuration and trajectory option, the thermal environment, deceleration environment, crossrange and downrange performance, and entry corridor were assessed. In addition, the feasibility of a common vehicle for lunar and Mars return was investigated. The results show that a low lift-to-drag ratio (L/D = 0.3) vehicle provides sufficient performance for both lunar and Mars return missions while providing the following benefits: excellent packaging efficiency, low structural and TPS mass fraction, ease of launch vehicle integration, and system elegance and simplicity. Numerous configuration options exist that achieve this L/D.

Boundary conditions for skip entry trajectory

“…For higher velocities the centrifugal force (squre of velocity) has also some impact, therefore causing the deviation in the analytical method as compared to the numerical. This can be seen from the equation (10), that we retain only the first term for the derivation of analytical solution for the skip entry.…”

“…By using MATLAB® a design is proposed of reentry parameters for given landing location according to the current alignment of the moon using skip atmospheric trajectory of the CEV. The comparison and updated guidance algorithm for the Apollo vehicle shown that for low L/D ratios long range cannot be achieved without using skip maneuver [8][9][10]. Analytical guidance method for the skip entry trajectory under the constraints of aerodynamic deceleration and heating loads are also studied [11][12][13] .…”

The crew exploration vehicle (CEV) and the next generation of human spaceflight

“…Fig. 1, which was adapted from a 1968 planetary reentry text, is still an excellent presentation of the initial factors which must be considered in the configuration and shape of the spacecraft [1,2].…”

Multiobjective Optimization of Earth-Entry Vehicle Heat Shields

“…(6)] H = exponent [Eq. (7)] h = length along y direction, m h t = altitude, km j = semimajor axis length of a blunt body, m j max = maximum mesh points in x direction k = semiminor axis length of a blunt body, m k max = maximum mesh points in direction L = lift, N l = length along x direction, m M 1 = freestream Mach number m = mass, kg m 1 = number of sides of the superellipsê n = normal unit vector, away from surface n crew = crew number, person n max = peak deceleration load, Earth g n 1 , n 2 , n 3 = superelliptic parameters p xrs = cross range, km Q = heat load, kJ=cm 2 q = heat flux, W=cm 2 q 1 = freestream dynamic pressure, Pa r = base radius, m r n = nose radius of blunted cone, m r s = radius of curvature of spherical segment, m S = area of base cross section, m 2 t = time, s t d = total mission duration, days V PR = pressurized volume, m 3 v 1 , v 2 = superellipse parameters V 1 = freestream velocity, m=s x, y, z = coordinate values, m = angle of attack, = sideslip angle, = trajectory flight-path angle; positive pointing away from planet, so = shock-standoff distance, m "…”

“…This involves entering Earth's atmosphere at superorbital velocities ranging from 10 to 15 km=s with corresponding Mach numbers from 30 to 50 [1] while withstanding 3000 K temperatures. The forward heat shield, which protects the vehicle, is the primary contributor to the vehicle's aerothermodynamic performance, i.e., the aerodynamic forces, moments, and heat transfer [2].…”