Research
Space Transportation System Laboratory (STL) has investigated the issues that occur in spacecraft during atmospheric entry. Various phenomena occur during the entry, descent, and landing (EDL) phases. One of the most critical stages in space missions is characterized by the fact that the spacecraft enters the atmosphere with a high velocity and is decelerated by aerodynamic forces.

Targets
During the EDL phase, the flow field around a spacecraft varies widely. For example, the following phenomena and problems occur in spacecraft:

• The effects related to free molecular flow and rarefied gas dynamics are significant in low-Earth orbits at altitudes above 100 km.
• Hypersonic and low-Reynolds-number flows occur at the entry phase between altitudes of 100 and 50 km. In this region, aerodynamic heating and radio-frequency (RF) blackouts are critical problems for spacecrafts.
• Aerodynamic instability has been confirmed in the descent phase between altitudes of 50 and 10 km. In this region, transonic or supersonic flows with turbulence significantly affect the aerodynamic characteristics of spacecraft. Critical events, such as parachute opening , also occur at this altitude.
• The aerodynamic deceleration is almost complete, and the spacecraft reaches the terminal velocity during the landing phase at altitudes below 10 km. The uncertainty of gust and atmospheric density is critical for spacecraft aerodynamics. Accurate prediction of aerodynamic characteristics is required to improve the accuracy of landing point prediction.

We are attempting to solve these phenomena and problems using computational approaches and wind tunnel tests.

Methods
STL is involved in computational approaches using high-performance computers, such as Fugaku, and in experiments using large wind tunnels at JAXA and other institutions. STL is collaborating with JAXA and several universities to contribute to spacecraft design and development and space missions using spacecraft.