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Earth Entry Simulator

This is a relatively simple low-fidelity sim for blunt capsules (re)entering Earth's atmosphere.

Some features:

  • Simple atmospheric model from Braeunig's Rocket & Space Technology (US Standard Atmos)
  • 2D & 3D versions
    • WGS-84 ellipsoid for 3D
  • fixed aerodynamic coefficients
  • 1st order entry heating and heatshield design (PICA)

Vehicle Design:

Configure the mass, geometry, and aerodynamics of the vehicle (point mass). SpaceX Crew Dragon example from my work here:

% input values: DESIGN
m = 21200/2.205; % mass of entry vehicle (kg)
Cd = 1.23; % drag coefficient
Cl = 0.27*Cd; % lift coefficient          -> modulated in flight (roll angle), used as constant "fudge factor" in this sim
d = 4; % entry vehicle diameter (m)
S = (d/2)^2*pi(); % ref. area (m^2)
BC = m/(S*Cd); % ballistic coefficient (kg/m^2)
Rn = 2; % nose radius (m)                 -> used as a "fudge factor" in this sim for heating calcs
emis = 0.9; % thermal IR emmisivity (0.9 for PICA)

Entry Conditions Setup:

2D:

Specify either: apoapsis height & peripsis height OR inertial entry velocity and entry flight path angle.

Example:

type = 'Orbital'; % specify type of entry: 'Orbital' or 'IC' (initial conditions)
if strcmp(type,'Orbital')
    Conditions = [22,419]; % periapsis and apoapsis altitudes (km) -> LEO return
else % initial conditions case
    Conditions = [-6.45,11.4]; % EFPA (°) and Entry Velocity (km/s) -> Martian direct entry return
end

3D:

Pseudo orbital elements: apoapsis height, peripsis height, inclination, (Earth) longitude of ascending node, argument of peripsis. Again SpaceX Crew Dragon example here & here:

Conditions = [22,418]; % periapsis and apoapsis altitudes (km)

% Initial Orbit Angles
inc = 51.6; % inclination (°)           -> ISS inclination
RAAN = 127; % (Earth) longitude of ascending node (°)
w = 165; % argument of periapsis (°)    -> RAAN & w tuned to facilitate landing near Florida from the northwest

Entry Heating & PICA Heat Shield Design:

Extensive leverage of methods from my work here. Returns a first order estimate of required stagnation point 1D heatshield thickness. Specific to the PICA material:

  • Calculate Sutton & Graves convective & Martin radiative heating rates
  • assume radiative equilibrium to find thermal environment around vehicle stagnation point
  • use PICA ablation data and thermal properties to:
    • estimate & integrate ablation rate to find total thickness "lost"
    • 1D unsteady heat flow to determine minimum "insulation thickness" to keep bondline from failing

Which script to use?

EarthEntry2D.m: For generating quick loading & heating data/plots, vehicle design workshopping, & use with high energy entries (lunar, interplanetary). Example outputs (non-exhaustive):

image

EarthEntry3D.m: For generating quick loading & heating data/plots, vehicle design workshopping, but in 3D. Example outputs (non-exhaustive):

image

EarthEntry3D_Observation.m: For planning/predicting observations of reentering vehicles (like here). Adds heating rate representation to 3D trajectory plots. It skips outputs/plots of ancilliary trajectory data. Example outputs (non-exhaustive):

image