Coming Home

De-orbit burn The craft spins itself 180 degrees so that it is facing backward with respect to its velocity The engine is fired, decelerating the craft by m/s It then flips end over end, lining up for approach

Lower orbital velocity drops the craft out of orbit placing apogee within the Earth’s surface

How does it do it? The craft uses it’s large planform area to generate drag and slow itself down This creates incredible heat and structural stresses on the craft Structural and material limitations guide the reentry

Taking advantage of the thermosphere From the 200,000 km orbit down to the Entry Interface [around 120,000 km] drag is quite low From then on, low density means low heating: maximal use of planform for maximum drag When heating becomes too great, angle of attack is lowered: less drag, lower descent rate

Ideal Reentry for Lifting Body Picture thanks to

Reentry Altitude Over Time Interesting Notes: Sharp drop in altitude results from low drag due to low air density As you will soon see, at 1km in altitude, velocity is ~200 mph Nice linear profile at low altitude means the craft has entered it’s controlled gliding phase The drop in altitude at around 1600 seconds [altitude of about 16,000 ft] is due to an decreased angle of attack to begin landing phase From that point on the craft acts just as a typical airplane and enters the landing phase

Serenity Reentry Velocity Maximum of 1.35 g’s The reentry profile must balance heating rate and reentry forces [G’s] while still landing at a reasonable speed.

Downrange Distance As predicted, at landing, the craft has traveled just over 10,000 km. With this value it is possible to designate a range of points in the orbit for accurate reentry.

Ground Track

To the right is a diagram of a Westerly Approach to the Heading Alignment Cylinder Shown here is the reentry ground track with two optional headings

Future Considerations Get a more accurate model of the thermosphere if possible. Model of body forces to ensure structural limitations are not exceeded Optimization for heating rate and maximum g’s felt Newly introduced heating rate limitation will help with producing the safest reentry profile