There’s nothing quite like rocket science, is there? It’s as fascinating as it is complicated. It’s not enough to just get a design right anymore – you have to get it right on the first go-around or very soon thereafter. Enter AxSTREAM.SPACE and all the functionality upgrades introduced in 2021.
AxSTREAM.SPACE was created by experienced mechanical and turbomachinery engineers to level the playing field when it comes to turbomachine-based liquid rocket engine design. By giving propulsion and system engineers a comprehensive tool that can connect with other proprietary or commercial software packages, the sky is, in fact, not the limit for innovation. It covers everything from flow path aerodynamic and hydrodynamic design to rotor dynamics, secondary flow/thermal network simulation, and system power balance calculations. This year, we are proud to unveil some new features that enhance each of these capabilities, which were developed at the request of our customers.
A critical part of any rocket engine development, as pointed out in a NASA blog, is engine power balance, also known as thermodynamic cycle simulation. AxCYCLE, SoftInWay’s own thermodynamic cycle solver that has been widely used in power generation and aviation is now helping companies build rocket engines from scratch, as well as expand their engine lineup based on an existing system. There are some goodies, however, which make it the perfect tool for power balance, and an asset of AxSTREAM.SPACE.
One of the first upgrades in AxCYCLE for rocket engine design was the integration with NASA’s Chemical Equilibrium with Applications, or CEA, tool. Considered the gold standard when it comes to incorporating accurate chemical properties in your working fluid, CEA was developed by NASA and is widely used throughout the industry, so it makes sense that we’d incorporate it into AxCYCLE for your convenience. Another new feature is the incorporation of burners for rocket engines specifically, and these were validated against NASA’s CEA tool as well.
Another area of focus for AxCYCLE and AxSTREAM.SPACE was nozzles. Convergent-divergent nozzles, also known as De Laval or CD/con-di nozzles, are a staple in just about all rocket engines (and high-speed aircraft). These nozzles help to provide high-velocity thrust, which is a must if you’re planning to have a vehicle reach speeds required to enter space. Naturally, our hard-working engineers incorporated different configurations of these nozzles into our component library. Included in this new batch of components are nozzles with regenerative cooling so that fuel preheating and nozzle cooling can be simulated accurately, which allows for higher engine efficiency.
All in all, AxCYCLE is one of the newest additions to AxSTREAM.SPACE and will smooth the path forward in rocket engine power balance simulation.
Where it all started for AxSTREAM many years ago – turbine design and analysis has been at the very core of SoftInWay and AxSTREAM since we were founded. But old dogs can learn new tricks, and we continue to improve the solutions we provide our customers.
Some of the more notable new features in AxSTREAM for turbine design in rocket engines include integration with NASA’s CEA tool for working fluids design in AxSTREAM.
Additionally, drilled nozzles can now be incorporated into an axial turbine’s design (and have been improved upon, bringing more geometric flexibility), can be viewed in 3D, and can control the geometry of these nozzles to ensure you are getting the best aerodynamic performance from your turbine. With these new parameters, we have added new loss models based on empirical equations and CFD analysis. This means more accurate models and calculations for you, and fewer headaches about real-world performance.
Designing a pump comes with its own set of challenges. Cavitation is a constant adversary of the design engineers as well as the operators, as cavitation can easily lead to an eroded impeller and ruined pump.
That’s where AxSTREAM.SPACE can help you fight back. A new feature our engineers have worked hard to include in the latest version is filtering out preliminary designs based on things like HS Max (cavitation suction lift), and Net Positive Suction Head required (NPSHr), both of which are parameters to consider in cavitation. Based on this, you can pick a pump with a higher positive cavitation suction lift, which is preferable for avoiding pump cavitation.
Inducers are commonly included in turbopump designs, but in some programs, modeling the impeller with the inducer in front of it is not possible. In AxSTREAM, it’s not only possible in the different modules, but this can be done directly in preliminary design, which incorporates staggered blades, and are manufacturable. Each point, also known as a “solution” in preliminary design, has an inducer design that is unique, and yet is a realistic, manufacturable design to fit your needs.
Ah, volutes, the magic metal snail shell. The latest version of AxSTREAM.SPACE allows users to create multiple shapes of a volute. AxSTREAM.SPACE’s volute solver allows engineers to pick different geometries, and parametrize what they are looking for. Once the proper volute has been chosen and modified to fit the system, it can be exported to the CFD, FEA, or CAD program of your choice. The same goes for your impeller geometry – once you have your performance optimized, a performance curve that fits your needs, you can export that geometry to the solver of your choice inside or outside of AxSTREAM!
Secondary Flows, Seals, and other Thermal Networks
Let’s talk seals for a minute.
Okay so marine mammal puns aside, mechanical seals play a large role in the successful operation of turbopumps and liquid rocket engines. Similar to other turbomachinery, turbopumps utilize mechanical seals. That’s why our development team has been hard at work adding to the fluid seal library with components just for turbopumps. In a similar fashion, another set of components our engineers added to AxSTREAM NET that is of interest for AxSTREAM.SPACE is bearings. Both bearings and seals need to be considered in a system to accurately calculate secondary flows, and that’s where AxSTREAM NET helps!
Another important area to consider is two-phase or multiphase flows. For those unfamiliar, phase changes are very common in liquid rocket engines, as the oxidizer which is partly responsible for engine combustion is typically liquid oxygen, having cryogenic properties with a boiling point of -297 degrees Fahrenheit. Combine this with the combustion chamber of a rocket engine which can be as hot as 5,800 degrees F, and phase change of the fuels and oxidizers are all but inevitable. It’s important to simulate the multiphase behavior of these fluid systems, analyze heat transfer, and also examine any mixtures (or lack thereof in the previous figure where the Helium zone – in red – acts as a buffer to prevent mixing of the propellants which would lead to unwanted combustion in the leakage area).
Lastly, regenerative cooling is very common in liquid rocket engines as I mentioned earlier. You can see that in AxSTREAM NET, the regenerative cooling system can be made in a 1D layout with channels for the fuel coming from the pump discharge through to the combustion chamber fuel injector and a supercritical turbine. You can see that in our video here.
Bearings and Rotor Dynamics
One last area we’re going to examine before this blog comes in for a landing is rotor dynamics and bearings. While I’ve discussed (arguably ad nauseum) the importance of rotor dynamics and bearing analysis, I’m going to harp on this important topic again for a minute. When you have lives on the line, as well as hundreds of billions of dollars in equipment to care for, a rather niche discipline like rotor dynamics analysis can prove catastrophic if not properly addressed. So, what have our engineers done to address this part of liquid rocket engine design?
Our engineers started by incorporating all of the most common bearing types and other common supporting components which need to be considered into AxSTREAM Bearing. The different kinds of hydrostatic bearings that are commonly seen in turbopump rotor trains are there, and ready to be selected, designed and configured with the click of a mouse button (the left one, obviously). From there, AxSTREAM.SPACE’s structural engineers made it easy to design and simulate bearing characteristics, both in AxSTREAM Bearing and AxSTREAM RotorDynamics. Additionally, the fluid properties of the bearings’ lubricant can be input manually or selected from a database.
In AxSTREAM RotorDynamics, all of the bearing geometry and data can be exported over into a rotor train project easily.
Wait. Your turbopump has multiple rotors with gears between the two? Ah, well, we came prepared!
In AxSTREAM RotorDynamics, you can easily build a complete model of your rotor train that contains lumped mass inertia points to represent impellers and turbine blades, as well as rotor couplings, gearboxes, and the numerous ancillary support components previously discussed like bearings and seals. Once your model is built, you can complete the full scope of rotor dynamics analyses in seconds and minutes, not hours and days. Everything from critical speed analysis to stability analysis and undamped response analysis can be solved in less time than it takes to count down a rocket launch. Thus, you can have peace of mind, knowing that all the potential hazards of undamped critical speeds and natural frequency resonances have been accounted for, and your turbopump rotor is ready to spool up.
Putting it All Together
At the end of the day, AxSTREAM.SPACE is constantly being added and expanded to incorporate real world functionality. By working with clients including Orbex, Orbital Machines, and others, we have given engineering teams both large and small the ability to create liquid rocket engines and turbopumps from scratch in less time than ever thought possible.
We haven’t even covered the capabilities of the platform when AxSTREAM ION is used to run all the AxSTREAM modules in batch mode. Nor have we covered how the entire turbopump preliminary design (turbine, pumps, rotor dynamics and secondary flows) can be done in as little as 4 hours (No, seriously, we were able to get a complete turbopump design done in less time than it takes to fly from New York to London, granted, not with a rocket).
If you are interested in learning more about what AxSTREAM.SPACE can do to propel your vehicle into orbit, or to keep your astronauts and critical components in a controlled environment, contact us at email@example.com and speak with us today!