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Re: Space Shuttle

Postby Thorsten » Tue Apr 07, 2015 3:37 pm

Richard Harrison joined the team - the shape of things to come:

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Re: Space Shuttle

Postby Torsten » Tue Apr 07, 2015 4:55 pm

I think I have an idea what to present at next FSWeekend, November 7th & 8th 2015.

Nice work!

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Re: Space Shuttle

Postby wlbragg » Tue Apr 07, 2015 5:20 pm

8)
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Re: Space Shuttle

Postby Thorsten » Wed Apr 08, 2015 5:13 pm

Re-entry work... managed to get the first version of a guidance computer done which tells you azimuthal deviation and desired acceleration needed to reach the landing site, so that you can fly your rolls and roll reversals accordingly. Sort of works - I managed to hit Vandenberg from 3700 miles away, though a bit high on energy, but it's definitely challenging to get right.

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Re: Space Shuttle

Postby Hooray » Wed Apr 08, 2015 5:17 pm

so it seems, you already got the computations covered then ?
What are you currently using for displaying those, just properties or any gauges/Canvas stuff ?
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Re: Space Shuttle

Postby Thorsten » Wed Apr 08, 2015 5:26 pm

So far, everything flight-relevant goes into the HUD (which changes mode dependent on mission stage). We don't have any cockpit instrumentation done yet.
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Re: Space Shuttle

Postby wlbragg » Thu Apr 09, 2015 12:39 am

Is that really the particle emitter (in the screenshot)? If it is, that is Awesome!

Edit 4/9/15 10:00am

I haven't grinned like I just did in a long time.

What a ride, I tried "final approach" at KEQA, I'm giddy.
Really smooth and really nice!
What a hoot!

Edit 4/9/15 10:23am

Kennedy is out for me, I guess it Rogers Dry Lake next! (oops, wrong Kennedy, some grass strip somewhere), have to try again with the correct airstrip..
This is addictive.
The Speed Brake and chute deploy, well, I'm hooked.
I wish I was proficient at modeling I would do the gear but I'm afraid it would take me way too long.

Oh, when I tried Kennedy and forgot to start terrasync I had to ditch in the water. The shuttle hit the water slowed rapidly to a stop. I switched to external view and it slowly started to sink nose first until just the aft end was showing. Then the sink rate slowed and I left the simulation. Really nice, I'm curious, is that standard JSBSim behavior or programmed in somehow?

2 attempts at Kennedy and overshot the end of the runway by about 100yds 1st attempt, 50yds 2nd attempt.

How many hours do we have to log in the sim before we can take control of the real thing?
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Re: Space Shuttle

Postby Thorsten » Thu Apr 09, 2015 5:33 pm

Is that really the particle emitter (in the screenshot)? If it is, that is Awesome!


Yeah, that's the normal particle system.

Really nice, I'm curious, is that standard JSBSim behavior or programmed in somehow?


I suppose that's a strange interaction between the invisible contact points holding the launch stack upright and the water - they're not 'gear' in the classical sense, because you'd get a really odd landing position if they're out, so there's some tricks involved in moving them upward by hand - but once the gear does not have contact, the virtual points take over... It's an accident basically.

2 attempts at Kennedy and overshot the end of the runway by about 100yds 1st attempt, 50yds 2nd attempt.


Really? You know you're allowed to use brakes, right? :-)

I haven't tried anything fancy, just flying by the published procedures, and Kennedy should be just fine.

How many hours do we have to log in the sim before we can take control of the real thing?


I lost count on how many virtual dollars I wasted losing control at the various stages...
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Re: Space Shuttle

Postby wlbragg » Thu Apr 09, 2015 6:19 pm

Thorsten wrote in Thu Apr 09, 2015 5:33 pm:Really? You know you're allowed to use brakes, right? :-)

Yeah, on the third attempt. :oops: . Then I had all kinds of room!
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Re: Space Shuttle

Postby erik » Thu Apr 09, 2015 7:59 pm

JSBSim (now) has two kinds of contact points: bogey for the gear and structure for anything else.
Bogeys sink in water but structures do not. This makes a neat way for adding floats with wheels. When defines properly such a configuration could land on a runway and on water.

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Re: Space Shuttle

Postby Thorsten » Sun Apr 12, 2015 9:53 am

Shown elsewhere already - progress on the groundtrack map. I don't think it's part of the real instrumentation, but it's still a very useful feature:

Image



Lots of not so visual progress as well. I've been going through 'Trajectory management and Flight Characteristics' in the crew manual and started to implement control modes close to the real CSS in the various mission phases.

On ascent, the CSS mode has a 'stick controls rate' function which I have now implemented using PID control logic. This makes the shuttle almost disappointingly easy to launch (it doesn't really feel like a rocket any more...) - the logic is in fact so good that you can watch the first minute of the launch from outside before going back into cockpit mode. But it does allow to launch into a precise inclination, so there's that.

In orbit, the shuttle has a number of different Digital Autopilot (DAP) modes to control attitude and translation - they're partially mission-specific. I'm having a look at how I can best keep the deadband and rate settings configurable - in principle the modes should all be supportable. Stationkeeping will probably be handled by Nasal scrips supplying input to the DAP - the shuttle has various tracking modes for thermal management.

The guidance computer seems to perform fine - so far I have several selectable landing and TAL abort landing sites, and if you choose any of them within a halfway reasonable range, it will try to provide you with guidance information during entry (it won't do an impossible entry trajectory). Basically, I could aim the shuttle using the procedures published in the crew handbook - still not perfect in every detail, but the outlines of the dynamics are there.

Richard has some progress with the cockpit - we now have a panel in, and for the moment a fake photo texture across it which we'll eventually replace.
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Re: Space Shuttle

Postby Hooray » Sun Apr 12, 2015 2:15 pm

Using Canvas for visualizing orbital flights (cont'd PM)
Thorsten wrote:progress on the groundtrack map. I don't think it's part of the real instrumentation, but it's still a very useful feature [...]
The real avionics is surprisingly (or perhaps not) spartan and not very visual. The entry management displays are velocity vs. altitude diagrams with the pre-calculated track for the mission and the envelope lines shown and the current state of the orbiter as a triangle plotted inside.
Image


diagrams like those (velocity/altitude and lift/drag vs. AOA) should also be pretty straightforward to recreate -and dynamically update- using Canvas, i.e. could be shown in the same GUI dialog if needed (using clipping), which would probably come in handy while developing the other fancy stuff you mentioned above (guidance computer/autopilot modes) - i.e. for debugging/troubleshooting purposes.

It's basically the same technique you're using currently - but you would probably want to use VG_CUBIC_TO or VG_SCUBIC_TO for doing curves between x/y points instead of straight line segments (see api.nas), while considering the x/y axes "static" and only update ~20-30 points per graph.

The triangle/space shuttle symbol could then be loaded from a SVG file or created procedurally using OpenVG paths (line segments).
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Re: Space Shuttle

Postby Thorsten » Sun Apr 12, 2015 3:25 pm

Richard is pretty good at what he's doing - the current (still imperfect, most displays are still fake at this point) state of the cockpit - location is 650 km over Australia:

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Re: Space Shuttle

Postby Hooray » Sun Apr 12, 2015 3:38 pm

looking good - is this based on any of the freely-available 3D models (from NASA or other places) ?

BTW: all that is needed to replace those statically-textured MFDs with dynamic Canvas textures are 5 lines of Nasal code - so that even your little "helper map" could be easily shown inside the cockpit
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Re: Space Shuttle

Postby Johan G » Sun Apr 12, 2015 3:46 pm

Ooh! It will be very interesting to see where this leads. :D
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