As a vehicle re-enters the Earth’s atmosphere, it will be travelling at hypersonic speeds through the quiescent atmospheric gas for the majority of its journey. Consequently, a bow shock forms ahead of the vehicle, creating a sudden temperature and pressure increase. The post-shock temperatures are high enough to excite internal energy modes of the gas particles and promote vibrational...
Background of the study
When a vehicle travels through Earth’s atmosphere at hypersonic speeds, the temperature in the shock layer rises significantly. This causes air molecules to dissociate. For higher enthalpies flow regions may experience chemical nonequilibrium, ionization, and thermal nonequilibrium. In addition, transitions between bound-bound, and, for a partially ionized gas,...
Background: Recent investigations of ice and gas giant entry flows have been motivated by the high priority listing of probe missions to Saturn and Uranus in the 2023-2032 planetary science decadal survey [1]. The atmospheres of these planets are primarily composed of H2 and He, with trace amounts of CH4. The convective and radiative heat loads encountered by these vehicles is controlled...
In recent times, satellite systems boasting thousands of satellites have been launched into orbit. The relatively short lifespan of these satellites, typically lasting only 3-5 years, has lead to increasing chances of in-orbit collisions and overall space cluttering. As the number of space debris experiencing post-mission uncontrolled re-entry rapidly increases, there is growing concern for...
Previous studies in the scope of Icy Giants entries and aerocapture have highlighted \cite{Coelho:2023} that small concentrations of \ce{CH4} in the freestream, as well as injection of carbon-containing ablation products in the boundary layer may yield dramatic increases of radiation, owing to the formation of C-containing species that are known to be strongly radiative at the representative...
We present an analysis for the radiative heating of characteristic spacecraft shapes in representative entry trajectories into the Icy Giants Uranus and Neptune.
The current analysis develops upon the CFD analysis performed by Fluid Gravity Eng. (FGE) which has yielded a complete set of simulations for an axi-symmetric capsule flying at four representative trajectory points during an Uranus...
Emission spectroscopy measurements of N2/CH4 plasma are presented from 350 to 850 nm. The high-temperature plasma is generated at atmospheric pressure using a 50-kW Inductively Coupled Plasma (ICP) torch. The plasma is found to be close to LTE at ~ 6900 K and is then passed at high velocity through a water-cooled tube. The water-cooled tube induces rapid cooling and fast recombination....
Background of the study:
For most re-entry cases, spacecraft experience radiative heating from the hot shock layer flow which envelops the vehicle during planetary entry. Due to the long length scales that are required for the flow to equilibrate at conditions near peak heating, there is often significant uncertainty in the chemical environment in many planetary entry scenarios which...
Background of the study:
With increasing interest in both manned and unmanned missions to Mars, human spaceflight to the red planet is becoming a critical focus. Unlike robotic missions, human missions require significantly shorter transit times between Earth and Mars to minimize astronaut exposure to space hazards. For a 120-day transit to Mars, entry velocities could reach as high as...
Predictive models are a cornerstone of NASA’s ability to design missions to outer planets. For hypersonic entry into an atmosphere, chemical rate data, excitation cross sections, and emission probabilities are a necessary precursor for these models to compute the radiative heat flux on a vehicle. This data is inferred from ground based test facilities which attempt to reproduce certain aspects...
Shock tube flows can be used to investigate non-equilibrium thermochemistry and radiative processes found in hypersonic flows, commonly through spectroscopy techniques which can be used to infer energy levels and number densities. The flow in a shock tube contains many flow non-uniformities, in particular boundary layer effects. For the purpose of studying the properties of the test slug, the...
Introduction
The study of thermochemical non-equilibrium effects in hypersonic flows is valuable for the development of predictive tools for atmospheric entry vehicles and high-speed propulsion systems. Facilities like the Electric Arc Shock Tube (EAST) at NASA Ames Research Center play a vital role in investigating these phenomena by generating high-enthalpy flows. Recent experiments...
Measuring electron number densities in hypersonic plasma flows is crucial for understanding aerothermodynamic phenomena, where traditional fluid dynamics principles no longer apply due to high speeds. The gas around the vehicle becomes hot enough to cause dissociation and ionisation of molecules, creating a chemically reacting flow [1]. The aerothermodynamic phenomena include chemical...
The critical design review status of the Dragonfly aerothermal environments and simulations will be presented. Titan’s atmosphere predominantly consists of nitrogen (~98% by mole) with small amounts of methane (~2% by mole) and other trace gases. CN is a strong radiator and is found in nonequilibrium concentrations for Titan entry, and is of particular importance on the backshell, where...
Shock and expansion tubes are important facilities used to investigate hypersonic conditions experienced at high Mach numbers and during planetary entry. However, they are limited by short test times depending on the facility design and test conditions used. The NASA Ames EAST shock tube, for example, has test times between 3 and 20 µs whereas the Chinese JF-12 facility has test times between...
