Rapid Descent Suborbital Approach Profile (RaDSAP)

In the earliest days of Space Travel, spacecraft returning to a planet with an atmosphere would use the aerodynamic forces of the atmosphere to decelerate the spacecraft to a safe speed prior to landing. While many craft in the 28th century have the engine power and efficiency to decelerate to safe speeds without aerobraking, this is still the most efficient way to slow an aircraft prior to landing on an atmospheric planet.

When a Spacecraft uses this method to approach a planetside spaceport, it is referred to as their Rapid Descent Suborbital Approach Profile, abbreviated as RaDSAP. During a RaDSAP approach, the airspeed of the craft makes it difficult to control. Additionally, the air on the hull of the craft will often superheat and form an ionized plasma. This plasma disrupts any electromagnetic communication, meaning that a craft reentering the atmosphere cannot communicate with traffic controllers.

For this reason, whenever a craft is on a RaDSAP approach, they are often instructed to follow a particular flight trajectory and "notify when cool" or "notify when at the bottom of your RadSAP." Ships in the process of a RaDSAP decent are given priority over other traffic, who are often diverted to give the descending ship ample room.

Alternatives
A ship may choose to fire their engines to decelerate prior to entering the atmosphere. This process is less efficient than a RaDSAP approach, but puts less strain on the hull of the craft.

Certain ships may be specifically designed for hypersonic flight in the atmosphere. These craft may make an Injection approach, wherein they enter the upper atmosphere with a steep angle of attack, then bleed speed more gradually as the atmosphere becomes more dense. While this requires a specially designed craft, it is generally much faster and less taxing on the craft. It is not without risks, though. At such extreme speeds, the aerodynamic pressure on the front of the craft can cause superheating of critical components or dynamic aerodynamic stalls. The pilot and craft must maintain very specific angles of attack to balance aerodynamic pressure, temperature, and airspeed.