Technically it's just a physical representation of actual processes going on in my head ([hosted on my home computer, bear with it until I get the new server])
I’ve decided to rewrite all my internal systems simulation – now it’s A LOT better than it was, and it’s actually easy to add new systems there.
Primary change is that now there’s global table with all simulation-related stuff, and you can access any variable of any system from any point in simulation. For example if you want to find out voltage on specific bus, you can just write XSV.Systems.Electric.Bus["ac2"].Voltage. That is long, but it’s also reason for rewrite: I found large, long descriptive names really helpful when dealing with simulation code.
All systems have been rewritten, especially sensor system. Now every sensor is fully specified, it’s physical location, location of it’s wiring, electric bus it belongs to, type (various types make them behave differently), etc.
And what’s best – adding sensor instantly registers it in computer software, you can access it by using it’s literal name. There’s 280 or so sensors right now. And also there’s information about this sensor in computer database (limits, units, description).
Actual sensor data is decoded by MDM (multiplexor/demultiplexor, a device which gathers a lot of analog information from devices, and converts it into digital information to send to computers), and send over the bus.
I started working on XS Venture APU systems simulation. APU is auxiliary power unit, and it drives hydraulic pumps to provide hydraulic pressure in all parts of the spacecraft, oil pumps to lubricate mechanics of APU itself, and fuel pump to pump fuel for APU and extra torque for primary fuel pumps (which are electric though).
APU itself is a turbine – hydrazine is pumped and mixed with catalyst (like Shell 405), and reaction occurs, which generates heat (a lot of heat), and also gas. The gas is allowed to go through turbine, spinning it up. Computer systems control pressure by pulsing valves, which also changes RPM of the turbine.
Here’s part of the APU panel (which is used to start up and control it):
I also added technical documentation to SVN, which includes description for all sensors in the ship (so far 280 of them), various checklists (added as more and more systems work), and also I’ve wrote tetris for the on-board computer system:
I’ve been working a bit on MFD displays, bringing more information to them. The changes were small, mostly cosmetic, and I added few more variables output to them, and I thought it would be nice to have several examples of them, so here they are:
P.S. Exam results so far: theoretical mechanics – excellent, electromagnetism – excellent, differential equations – excellent, electric circuits and signals – excellent, just economy left.
Here’s one variant of XS Ventures fuselage, although it’s quite incomplete (lacks two distinctive tails, and also has some problems on the curvy side). It looks a bit wider and boxier than it really is, because of isometric projection.
Actually it has length of about 70 meters, and wingspan of only about 30 meters, and also I’m trying to fight with guidelines in SolidWorks:
I’m gonna call this one XSV Variant-1, there’s gonna be several distinct variations, to determine best aerodynamic shape (plus of course changes to every of those variations, in case it only needs some small fix).
Exams still going, so far really good. But also I’ve worked a bit more with solidworks, and I found out how to make complex surfaces, now I’ve got green light for starting for on final version of XS Venture’s hull. There will be several iterations, all of them roughly follow sketch I posted earlier, but I’ll test which one has better aerodynamics.
General sizes and parameters remain the same:
Length: 68 meters
Wingspan: 20 to 30 meters
Two slightly angled tails, two elevons
This is front view of one possible wing and fuselage configuration:
Sorry for lack of updates, I’m currently having exams, so they will come with delays. Anyway, I worked more on the autopilot, altered constants a bit, so it’s now much smoother.
I also recorded a video. I’m sorry for the quality, but there is a problem with simulation – it has to run fast enough, else autopilot will not be able to compensate for increasing error. If spacecraft is traveling at 5000 meters per second (less than orbital), then FPS of 100 results in spacecraft skipping 50 meters every frame, while FPS drop to 20 will make it skip 250 meters per frame – that’s more than enough to create major error.
I had to record video quickly, so I just used my old videocamera, and TV tuner to record the video:
I’ve been working more on ascent autopilot, now it’s much more fuel efficient (altough it doesn’t follow the equations I wrote up before, it’s just a general autopilot), and smoother. There are some small issues to fix with smoothing, but it’s already ready for XS10 mission (which will test it in a real mission).
Here’s altitude, in feet:
And here’s graphs for engine fuel flows:
Here’s engine thrust and atmosphere density. Notice how engine thrust grows as density decreases (while aircraft speed increases):
After reaching certain maximum thrust output it starts to decay, because as we’re getting higher and higher, there is less and less oxygen for engines to work. Thrust and fuel flow are nearly similar, that’s just how X-Plane models the engines…
I want to learn more about aerodynamics, and hypersonic aerodynamics (actually aerothermodynamics), plus I need a model of scramjet engine for XS Venture, so I decided to check out one configuration I found on the internet. It’s a fixed-geometry scramjet engine designed for 5 mach airflow.
You can see CFD pictures below, shockwaves are clearly visible, and you can see why engines loose efficiency outside of pretty small range of about 4.5 to 5.5 mach. The red area is area of high pressure. The fuel is injected into high-pressure area to increase volume of resulting gas, increasing its velocity. As you can see, the high-pressure area starts moving from it’s intended location when you increase or reduce airflow (at some point it even touches engine surface, which is very bad stress for engine structure).
All simulations are done at about 30km altitude, so the pressures are quite low. Static pressure does not affect distribution, it only affects absolute values, so it should be fine.
