Heating at the surface of spacecraft during atmospheric re-entry is estimated in order to design and determine appropriate thermal protection systems (TPS) for the safe transport and delivery of payloads. It is essential to account for all complex flow phenomena surrounding a spacecraft for an accurate assessment of the extent of heating. Identification of potential hot-spots and estimation of spurts in heating rates are important to fortify the TPS against any and every extreme condition that a spacecraft can potentially be exposed to.
In the current study, supersonic plume ejections from an anticipated combination of reaction control system (RCS) thrusters on a hypothetical spacecraft during transonic and hypersonic atmospheric re-entry are investigated. Re-entry at two different Mach numbers at the same altitude and zero degrees angle of attack are simulated to draw inferences on the impact of freestream velocities and velocity ratios (velocity of jet to freestream) on flow physics and surface heating.
Whereas the heating rate magnitudes in the immediate vicinity of the thruster vents are nearly the same during both re-entry velocities, farther away from the body, the hypersonic freestream (v_jet/v_∞ ~ 1) deflects the supersonic plume back towards the surface of the spacecraft, thereby expanding the area that is exposed to high temperatures. This augments heating rates by a factor of ~5. Furthermore, here, the shockwave upstream of the thruster plume impinges on the surface, further increasing heating rates by a factor of ~15.