1. Re-Entry Simulation
and Landing Area
For
YES2
(2nd
Young Engineers’ Satellite)
www.YES2.info
Silvia Calzada (stagiaire
ESA/ESTEC)

2. Thesis Objecties
• Development of REST
(Re-Entry Simulator Tool)
• Investigations with REST
Calculations of trajectory and landing area
• Conclusions
1) To choose the best place to land
2) Mission recommendations to minimize
landing area and

3. Re-Entry Simulator Tool
• Inertial <-> Fix to Earth reference system
• Geodetic <-> Geocentric coordinates
• Rotational velocity of the Atmosphere
• Effect of the rotation of the Earth
• Bulge effect of the Earth
• Spherical harmonic expansion for the Earth’s gravitational
potential, J2 (zonal)
• Thermal model
• Heat flux, temperature in the wall
• Drag coefficient for different regimens
• Flow regimen
• Density model NRLMSISE-00
• Wind model HWM-93
• G2S density, wind, gravity wave model
• Landing area (Monte Carlo Simulations)
The REST simulator includes many parameters:

4. Re-Entry Simulator Tool
• Inertial <-> Fix to Earth reference system
• Geodetic <-> Geocentric coordinates
• Rotational velocity of the Atmosphere
• Effect of the rotation of the Earth
• Bulge effect of the Earth
• Spherical harmonic expansion for the Earth’s gravitational potential, J2 (zonal)
• Thermal model
• Heat flux, temperature in the wall
• Drag coefficient for different regimes
• Flow regimen status
• Density model NRLMSISE-00
• Wind model HWM-93
• G2S atmospheric model with the latest meteorological
conditions
• Landing area (Monte Carlo Simulations)
The REST simulator includes

5. REST

6. Altitude and Distance
Geodetic Altitude vs. Distance travel over the Earth
0
20
40
60
80
100
120
140
0 500 1000 1500 2000 2500
Disance travel over the Earth [Km]
GeodeticAltitude[Km]
Perigee,v0=7820,gamma=0.974
Perigee,v0=7806,gamma=1.12
Perigee,v0=7812,gamma=1.244
Apogee,v0=7803,gamma=1.361
Apogee,v0=7812,gamma=1.623
Apogee,v0=7820,gamma=1.92
Release in Perigee
Release in Apogee
First estimation of
landing area

7. Landing Area Depending On Re-
Entry Conditions v0 and γ

8. Re-Entry Special Concerns
Orbit: highest apogee 1) Heat flux &
Temperature in the wall
2) Supercritical Reynolds number
Turbulence flow in subsonic flow regime
3) Because low ballistic coefficient of the capsule, the peak
of the:
wall’s temperature,
heat flux,
dissipated power,
gee-load
are happening in the upper part of the re-entry
(transition from rarefied gas and continuum flow regime)

9. Mission recommendations to
minimize landing area
Orbit: highest apogee, lowest perigee (largest length of tether)
Tether cut time in apogee and descending part of the orbit
Steepest flight angle
Optimal re-entry time: 00:00-03:00 am
Optimal day: around 21th
June
(summer, good weather conditions)
Heavy capsule
Low part of Solar cycle

10. Mission recommendations to
minimize landing area
Orbit: highest apogee, lowest perigee (largest length of tether)
Tether cut time in apogee and descending part of the orbit
Steepest flight angle
Optimal re-entry time: 00:00-03:00 am
Optimal day: around 21th
June
(summer, good weather conditions)
Heavy capsule
Low part of Solar cycle