In my work with rockets and spacecraft for Outerra, I've had to make many compromises, in part due to there being certain methods necessary for assembly of stages and separation, but mostly due the level of difficulty in building flight models for rockets. I haven't had much time for these endeavors lately, and some of them like the Delta IV Orion LVS, proved to be far too complex to start out with. So in my spare time I've been working on the Atlas V Launch Vehicle. It is my first successful and accurate rocket flight model in JSBSim, and one in which my new methodology seems to be working much better. Instead of building the entire flight model at once, I've decided to take it one stage at a time. In the past I would spend weeks building the flight model for all the stages at once, just for it to crash OT and I found it impossible to identify the cause. My new approach is building and testing in a series of incremental steps, by defining all of the necessary point masses in the mass_balance section of the FDM, and modelling the engines and propellant tanks for the propulsion section for each stage separately, and then finally integrating each stage one at a time until the flight model encompasses the entire launch vehicle. Part of my problem had been determining the best method to model the metrics at each stage separation event, because the aerodynamic parameters, among other things, change dramatically, and the JSBSim vanilla FDM example had no way to account for this. New methods in OT will make this possible without the undue complexity that is presently necessary.
The Atlas V represents a serious step forward in my understanding of JSBSim, JavaScript, physics, rocketry and orbital mechanics. I plan for it to be the benchmark example of rocket/spacecraft for Outerra, from which others can use to build their own. I have started a tutorial on
How To Build A Rocket for those of you who are interested in the technical details. I'll be adding to this considerably starting in December.
When I started working on the Atlas V, I had to pick a payload which could serve some functional game-play role. The Atlas V is the American space launch work horse, and while launching a satellite into Earth orbit, or even an inter-planetary transfer orbit, might be an interesting objective, it also presented serious challenges involving orbital mechanics and the shortcoming of not having a heliocentric solar system.
Instead, I picked a payload which would not only be feasible, but a lot more fun for everyone. The payload of choice is of course the Boeing X-37B atop the Atlas V 501 LVC, (5 meter Payload Fairing, 0 Solid Rocket Boosters, 1 Common Core Booster).
I have completed the first stage Common Core Booster of the flight model, as well as made significant progress on the X-37B flight model, all that is left in terms of the FDM is the Centaur Cryogenic Upper Stage, including some calculations for the new RL-10C engine, and upper stage RCS thrusters. Then it is just a matter of integrating the stages into a single flight model, and integrating the scripts and stage separation events. I'll also add in some electrical sub-systems, a solar array, battery and Inertial Reaction Wheel for the X-37B. There is also a flight model and 3d model of the AeroJet Rocketdyne AJ60A Atlas V Solid Rocket Booster, although it is not used on the Atlas V 501 LVC. Also, I do plan on making all of the other Atlas V 5XX configurations as well as the Atlas V 4XX configurations with the 4 meter Payload Fairings, along with a few payloads, such as satellite missions. There will be a new method for OT in the future to attach/release objects, so it will be possible for anyone to make a payload and launch it using the Atlas V or any other launch vehicle, which will also make it easier to build stages in the flight model. When this is released, I'll be including detailed documentation for building custom mods for the launch vehicle, including making calculations for interplanetary missions once we finally get that heliocentric solar system!
Along with that, I'll include a manual for modelling rockets, including how to implement the code I have developed for calculating the Keplarian Orbital Elements, transfer orbits, navigation parameters, etc, as well as some tricks I have learned along the way.
The video below shows a short simulation of the Boeing X-37B OTV in prograde equatorial Low Earth Orbit with an apogee of 128 miles and perigee of 99 miles. It demonstrates pitch maneuvers and attitude hold with the Reaction Control System thrusters, and a retrograde deorbit burn in preparation for reentry with the AR2-3 main engine. I have still yet to land the X-37B on a runway, but that is mostly due to the complexity of calculating the orbital parameters for the deorbit burn, reentry and navigation to the final approach, and less to do with the flight model itself. I have proven it can successfully reenter the atmosphere and achieve the glide slope necessary for a landing.
The Atlas V Space Launch Complex 41, and Cape Canaveral scenery, built by Acetone is going to be revisited in the coming months for some improvements, as I work to finish the 3d modelling, integrate the launch vehicle and perfect my code. Note that the 3d model is a rough draft, and more for a proof of concept than a detailed rendition. The final models will be extremely accurate, detailed, and fully functional. I plan for the release of this project for around the end of the year or the beginning of January.
Best regards,
Uriah
Author
Topic: [WIP] Atlas V XXX Launch Vehicle (Read 18723 times)