ACE designs thermal control systems for aerospace and terrestrial applications and performs steady state and transient thermal analysis using advanced thermal system analysis methods and software, including SINDA finite difference programs. Trade studies that consider alternative thermal system design approaches and operating scenarios are used to identify preferred thermal system configurations. ACE formulates finite difference or finite element models of thermal systems that are progressively refined as thermal system design evolves to maturity. Finite difference or finite element models used to evaluate thermal system performance must correctly represent thermal processes; system configuration and geometry; and conductive, convective, and radiation boundary conditions. ACE often applies models of a thermal system in conjunction with thermodynamic process analyses and models to calculate the thermodynamic state of fluids during mission operations. ACE performs thermal analyses and design concurrently and interactively with structural analyses and design so that optimal designs are arrived at quickly and efficiently.
ACE designs and analyzes cryogenic systems for aerospace or terrestrial applications. Cryogenic systems must be configured to store, transfer, and/or utilize cryogenic fluids such that mission objectives are met. Cryogenic systems for spacecraft or launch vehicle applications may include a PED or a surface tension PMD.
An example of concurrent and interactive thermal and structural design that ACE carried out was a cryogenic tank with a capacity of 4000 pounds of initially subcooled liquid oxygen for an upper stage orbital vehicle. ACE designed this tank to have the capability to orbit for up to 23 hours with fill fractions as low as 15 percent and then deliver bubble free propellant through a surface tension PMD to the rocket engine. This design did not use a thermodynamic vent to keep the propellant free of vapor bubbles. The complexity of a thermodynamic vent was avoided by paying careful attention to heat leaks through tank to vehicle attachments and tank penetrations, and the use of innovative designs for tank to vehicle mounts and for tank thermal isolation.
ACE has developed a design for a lightweight Dewar liquid hydrogen tank for a high altitude, ultra-long duration, unmanned aerial vehicle. The tank is capable of supplying liquid hydrogen for extended time periods. The vacuum insulated LH2 tank design consists of two concentric spherical aluminum shells with a vacuum space between the shells. The inner shell inside diameter is approximately 96.0 inches to contain 1100.0 lbs of liquid hydrogen at 2% ullage. The inner shell membrane thickness will accommodate an operating pressure of 30 psid. The outer shell is stiffened with an isogrid pattern on the outer surface to provide buckling strength and reduced weight. The vacuum seal between the inner and outer shells at the top and bottom polar boss mounts is a unique design controls heat leak into the inner shell.
ACE develops innovative and cost effective designs for cryogenic systems by using advanced methods in a concurrent and interactive approach to thermal, structural, and fluid systems design.