Monthly Archive for October, 2009

I’m working on FCS (flight control system) for X-30, it’s a piece of software (and some hardware) that makes actual steering in mid-air possible. It consists of these parts:

1. Hydraulic system – there are 4 servos in X-30 that control rudder surfaces, and elevon surfaces on wings. Every servo is attached to it’s corresponding hydraulic lines. Left and right rudders are behind hydraulic valves 1 and 2 (respectively), and left and right elevons are behind valves 3 and 4.
2. Software control – XGDC software takes input from RHC/joystick, and turns it into command for hydraulic servos. It turns a pair of 3 values (commands for pitch, yaw, and roll) into 4 commands for 4 hydraulic servos (rudder left/right, elevon left/right).
3. Autopilot and artiftical stability – special portion of software that controls and steers the vehicle, and also provides some artiftical stability to it’s fligth, making it smoother, and less shaky (it shakes a real lot because of it’s slim design, there’s no real vertical tail to prevent it from oscillating on yaw and roll axes)

The flight control system data display looks like this:

It displays current state of all controls, commands given to them, pressures in hydraulic lines, and also later possibly will show some information about artiftical stability, and autopilot. Autopilot is operating in either of two modes (suborbital or orbital). The FCS also automatically transfers between atmospheric flight, powered atmospheric flight and orbital flight. These three modes differ as following:

1. Atmospheric flight – only using control surfaces
2. Powered atmospheric flight – high-altitude flying, using control surfaces and reaction control system (RCS)
3. Orbital flight – using only reaction control system (RCS), and possibly main engines (for large manuevers)

Sorry for downtimes & my sisters website hosted instead of this. And for that ugly temporary link (with direct IP access…), it’s just some problem I know you all can live with (and also the website is really slow, and I got out of my daily update pace).

But I’m still doing stuff! A lot of stuff I should have posted! Let’s start with my new experiments in aerodynamics of X-30 (they are actually one week old…). First, pressure map, distribution of air pressure around the spaceplane:

Compression lift!

Now, here’s better part – temperature map, or more exactly map of air temperature above ships surface. The most red areas are approx 120 degrees C, and the blue areas area around zero (0*C):

These simulations ran for about 2 hours each, at higher precision than previous, albeit in “draft” (I didn’t compete one full cycle of simulation). But it roughly shows these three problems I had, and which I solved from before. Oh yeah, here’s the new CAD model of X-30 (for aerodynamics at least):


You can already see one major difference – the tail dihedral. The tail/rudders are now slightly angled, and why, I’m gonna tell you in a second.

So yeah, these are 3 weak points that I want to solve:

1. There was low pressure area forming in where tails joined fuselage, I fixed this by slightly altering fuselage shape, and adding some dihedral to the rudder. It doesn’t affect perfomance that much though.
2. The nose is burning hot. On the other hand, it’s made from a very resistant material, although the nose is designed to evaporate during the flight – while starting with completly perfect cone nose, after atmospheric reentry you can see that it lost at least quarter of it’s original nose (it just burned away). The nose itself is made from some material I forgot the name of. Or just something carbon – it doesn’t really matter, the nose has to withstand temperatures of 1700 degrees before melting/vaporing off.
3. The low pressure volume forming at aft wing tips – you can see the red stripe on where wings meet fuse. I think of adding a small curvature to the wing there, or possibly having a fixed – profile wing there to reduce this, because it’s very bad and unwanted. Such contrast in temperature is very structurally bad.

I always wanted to get into CAD, and now I did. I really like it – it’s not that hard, and it gives a real lot of control over shape and how everything is composed together. And there’s also liquid/gas flow simulation in SolidWorks! So I can fit my models into supersonic stream of air, and you know that’s what I like to do.

I’m working on a fully-detailed (actually, precise up to a centimeter) model of X-30. It means that the whole thing WILL change, to become realistic and to become able to sustain all aerodynamic forces acting upon its shell. Also I feel the need for knowing precise locations of key elements like hydraulic system and RCS, and this need has been increasing ever since I started this project.

So far I got this, a rough draft of outter composite shell (the shell is created from several parts, but in the end it will all be welded together into this solid shell):

I’m going to try add internal structures tomorrow, also break up that into composite model of wings, chassis, and tail fins (all separate).x