Shadow Tracking

Using RadCAD® for Shadow Tracking

Using the Monte Carlo ray tracing capabilities in RadCAD, Olivier Godard and Tejas Shah came up with this visual simulation of tracking the shadow of the International Space Station (ISS) on the belly of the Space Shuttle. The Shuttle is oriented with the payload bay doors looking nadir (facing earth) while the ISS, traveling at the same speed at a slightly higher altitude, passes over the belly of the shuttle blocking the sun's light.

ISS shadow tracking across the orbiter

The image has been postprocessed in RadCAD with the scale on the left representing the nodal heat flux, the view being the shuttle belly. The color scale maximum is 1354 W/m2 which represents full solar heating. As the ISS passes over the shuttle, the resulting shadow or blockage is displayed by the blue color (0 W/m2).

This simulation could have been performed using a raytracer for animated movie rendering but the advantage of RadCAD is that you can obtain a similar result directly applicable for other thermal related computations.

This example of using RadCAD to track IR and solar shadowing has been provided by Igor Carron of the Spacecraft Technology Center at Texas A&M University.

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dispersed vs. coalesced front

Tuesday, June 26, 2018, 1-2pm PT, 4-5pm ET

This webinar describes flat-front modeling, including where it is useful and how it works. A flat-front assumption is a specialized two-phase flow method that is particularly useful in the priming (filling or re-filling with liquid) of gas-filled or evacuated lines. It also finds use in simulating the gas purging of liquid-filled lines, and in modeling vertical large-diameter piping.

Prerequisites: It is helpful to have a background in two-phase flow, and to have some previous experience with FloCAD Pipes.

Register here for this webinar

FloCAD model of a loop heat pipe

Since a significant portion of LHPs consists of simple tubing, they are more flexible and easier to integrate into thermal structures than their traditional linear cousins: constant conductance and variable conductance heat pipes (CCHPs, VCHPs). LHPs are also less constrained by orientation and able to transport more power. LHPs have been used successfully in many applications, and have become a proven tool for spacecraft thermal control systems.

However, LHPs are not simple, neither in the details of their evaporator and compensation chamber (CC) structures nor in their surprising range of behaviors. Furthermore, there are uncertainties in their performance that must be treated with safety factors and bracketing methods for design verification.

Fortunately, some of the authors of CRTech fluid analysis tools also happened to have been involved in the early days of LHP technology development, so it is no accident that Thermal Desktop ("TD") and FloCAD have the unique capabilities necessary to model LHPs. Some features are useful at a system level analysis (including preliminary design), and others are necessary to achieve a detailed level of simulation (transients, off-design, condenser gradients).

CRTech is offering a four-part webinar series on LHPs and approaches to modeling them. Each webinar is designed to be attended in the order they were presented. While the first webinar presumes little knowledge of LHPs or their analysis, for the last three webinars you are presumed to have a basic knowledge TD/FloCAD two-phase modeling.

Part 1 provides an overview of LHP operation and unique characteristics
Part 2 introduces system-level modeling of LHPs using TD/FloCAD.
Part 3 covers an important aspect of getting the right answers: back-conduction and core state variability.
Part 4 covers detailed modeling of LHPs in TD/FloCAD such that transient operations such as start-up, gravity assist, and thermostatic control can be simulated.