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BrianJ BrianJ is offline
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Default Starship Mk.1
by BrianJ 10-04-2019, 06:53 PM

"Never compose anything unless the not composing of it becomes a positive nuisance to you." [Gustav Holst]


In terms of Orbiter add-ons, Mr.Musk is proving to be positive nuisance to me


Work in progress.....
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Question is - how to implement those aerofoil control surfaces using OrbiterAPI. Maybe need to go a different route than Orbiter's vertical/horizontal aerofoils and control surfaces?


No idea about RCS placement or landing gear - any info out there?


Cheers,
Brian
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Old 10-04-2019, 09:23 PM   #2
Urwumpe
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Depends - do you think somebody will notice the difference, that this spacecraft is not using real control surfaces, but actually fictive, physically implausible standard aircraft controls? Based on a real world behavior that you don't know and no human might ever know because a computer is doing the magic of turning guidance (or manual) commands into surface position commands?

Then yes, you might need some magic in the air foil functions.

But I think you might get away easy by just animating them as plausible as you can.
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Old 10-04-2019, 11:28 PM   #3
BrianJ
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Hi,
yes, I might go the simple route in the end. I don't really want to get into trying to make my own lift/drag functions. I was looking at those independently variable geometry airfoils and thinking "how's that going to work?"
But it's easy enough to change Orbiter's airfoil area/position on-the-fly, I might give that a try and see how it behaves.
Could be "realistic" enough for me.
Then try and figure how to translate pitch/yaw/roll commands into variable airfoil position/area. Should be interesting :-)
Cheers,
Brian
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Old 10-05-2019, 09:11 AM   #4
clipper
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This thing could be a field day for those fancy D3D9 Client reflections and textures.
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Old 10-05-2019, 01:59 PM   #5
francisdrake
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For starship's reentry I understand the 'forward' motion is in belly direction, while the wings (fins) are swept back. They control
- the roll axis by independently moving left and right wings
- the pitch axis (AoA close to 90) by moving main wings vs. canards
- possibly also the yaw axis by a clever combination of spreading out the mains and canards.

For a start I would do:
Kill the lift function during ascent, to avoid interference during the launch.

For the reentry first define the lift of the main body, a cylindro-conical object at supersonic speed. The center of lift should be aft of the geometrical center.
ESTIMATED AERODYNAMICS OF ALL-BODY HYPERSONIC AIRCRAFT

Then starting adding the fins and playing around with their lift functions.

For subsonic speeds, which will occur only shortly before touchdown, I would again drop all lift functions, using only Orbiters drag and control all movements with the RCS and main thrusters.
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Old 10-05-2019, 08:00 PM   #6
BrianJ
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Quote:
Originally Posted by clipper View Post
 This thing could be a field day for those fancy D3D9 Client reflections and textures.
I'm hoping one of the D3D9 texture artists out there might be interested in helping out :-)


Quote:
Originally Posted by francisdrake View Post
 For starship's reentry I understand the 'forward' motion is in belly direction, while the wings (fins) are swept back. They control
- the roll axis by independently moving left and right wings
- the pitch axis (AoA close to 90) by moving main wings vs. canards
- possibly also the yaw axis by a clever combination of spreading out the mains and canards.

For a start I would do:
Kill the lift function during ascent, to avoid interference during the launch.

For the reentry first define the lift of the main body, a cylindro-conical object at supersonic speed. The center of lift should be aft of the geometrical center.
ESTIMATED AERODYNAMICS OF ALL-BODY HYPERSONIC AIRCRAFT

Then starting adding the fins and playing around with their lift functions.

For subsonic speeds, which will occur only shortly before touchdown, I would again drop all lift functions, using only Orbiters drag and control all movements with the RCS and main thrusters.
Hey, thanks for the ideas and link to extremely informative doc! (lot of stuff for me to take onboard there). In the presentation, Elon is talking about a 60deg AoA and needing lift to control the maximum heating during reentry, also the more lift there is the easier it is to target the touchdown zone during later stages, so I think I'll be needing whatever lift I can use.

I can see the pitch/roll control won't be a problem, using the aerofoils in pairs of aft/fwd or port/stbd. But yaw has me wondering - my onboard fluid dynamics computer (my imagination ;-) is telling me that there will be torque around the yaw axis if an aerofoil is angled back, due to deflection of the airflow, and it's not obvious to me how to do that using Orbiter's horizontal/vertical airfoils.


Actually, I'm just thinking about flying the planned 20km "hop", not even thinking about reentry yet.


Figuring out how to do that last-minute back-flip and land will also be "interesting"!


Cheers,
Brian
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Old 10-06-2019, 01:16 AM   #7
Donamy
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It will have hot gas thrusters. That would work for yaw.
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Old 10-06-2019, 11:46 AM   #8
BrianJ
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 It will have hot gas thrusters. That would work for yaw.
Hi Don, yep, it might have to be that way. Although, I'm not seeing any RCS on the Mk.1 at all (might just not be obvious from the photos) but I've put some on mine anyway, on the aft blisters. My hunch is they are using the Mk.1 to test the aerofoil control system and landing, maybe don't need RCS for that. And I'm wondering if the algorithm for the aerofoil control is more than I can handle anyway, but I'm interested to have a go ;-)
Cheers,
Brian
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Old 10-06-2019, 03:09 PM   #9
Kyle
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Quote:
Originally Posted by BrianJ View Post
 Hi Don, yep, it might have to be that way. Although, I'm not seeing any RCS on the Mk.1 at all (might just not be obvious from the photos) but I've put some on mine anyway, on the aft blisters. My hunch is they are using the Mk.1 to test the aerofoil control system and landing, maybe don't need RCS for that. And I'm wondering if the algorithm for the aerofoil control is more than I can handle anyway, but I'm interested to have a go ;-)
Cheers,
Brian
For Starhopper the RCS was one of the last things they installed. Still quite a bit of work to be done on Starship Mk. 1 before it can fly.
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Old 10-06-2019, 04:55 PM   #10
francisdrake
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Quote:
...maybe don't need RCS for that
The wings become ineffective in slow flight, just before landing. While this can be controlled with the main thrusters, I am pretty sure an RCS will be included in the Starship Mk.1.

Elon also mentioned in the presentation to do the flip-over rather with the RCS, as the main engines are giving it initially a forward push, in the wrong direction if you want to slow down.
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Old 10-07-2019, 06:22 PM   #11
BrianJ
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Quote:
Originally Posted by Kyle View Post
 For Starhopper the RCS was one of the last things they installed. Still quite a bit of work to be done on Starship Mk. 1 before it can fly.
Right. If anyone sees any RCS installation, let me know :-) Or landing gear, for that matter.

Quote:
Originally Posted by francisdrake View Post
 The wings become ineffective in slow flight, just before landing. While this can be controlled with the main thrusters, I am pretty sure an RCS will be included in the Starship Mk.1.

Elon also mentioned in the presentation to do the flip-over rather with the RCS, as the main engines are giving it initially a forward push, in the wrong direction if you want to slow down.
I'm sure your right about the wings in slow flight. My experience with the Falcon booster and Dragon capsule add-ons was that you need to use any bit of lift you can get to help targeting the touchdown zone, before you switch the engines on, so I'm loath to get rid of any!
IIRC Elon said they could do the back-flip with RCS only when they go to "hot gas" RCS (Mk.3 or 4), and something tells me that will be easier than using only main engines, so I might end up doing that

Got a workable mesh, so now to work on the code. And then some flight test fun.

Cheers,
Brian
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Old 10-07-2019, 09:28 PM   #12
4throck
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Quote:
Originally Posted by clipper View Post
 This thing could be a field day for those fancy D3D9 Client reflections and textures.

That's easy, use the D3D9 debugger
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Old 10-08-2019, 08:37 AM   #13
barrygolden
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I did see a test version for a full nose thruster pack and it look a lot like the crewed dragon pattern. and a lot like the Shuttle's nose It will use the wings and canards quite a bit lower in its descent. If you guys have a go at the winged landing up might keep in mind an MFD for all winged craft like the Shuttle or X33. I did speak with one engineer and he has done the calculations for Venture Star and using today's knowledge about metal tanks it would have been feasible.
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Old 10-08-2019, 10:12 AM   #14
vchamp
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It's almost as exciting as the real Starship.
Quote:
Got a workable mesh, so now to work on the code.
Does the mesh also have landing legs?
It would be great if you could share your work in progress, preferably via a git repository.
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Old 10-08-2019, 03:04 PM   #15
BrianJ
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Quote:
Originally Posted by 4throck View Post
 That's easy, use the D3D9 debugger
Ah! I'll take a look at that. The texturing needs a bit more work anyway. Thanks.

Quote:
Originally Posted by barrygolden View Post
 I did see a test version for a full nose thruster pack and it look a lot like the crewed dragon pattern. and a lot like the Shuttle's nose It will use the wings and canards quite a bit lower in its descent. If you guys have a go at the winged landing up might keep in mind an MFD for all winged craft like the Shuttle or X33. I did speak with one engineer and he has done the calculations for Venture Star and using today's knowledge about metal tanks it would have been feasible.
Hi Barry, many thanks! Can't beat info from the shop floor
I wasn't happy about having RCS on the underside anyway (I imagine holes in the heatshield are not a good thing) - going to remake my RCS along Shuttle lines.

Yes, I'm guessing the aerodynamic steering only starts somewhere below 20km (my Falcon booster starts at ~15km) and well past peak heating.

Quote:
Originally Posted by vchamp View Post
 Does the mesh also have landing legs?
It would be great if you could share your work in progress, preferably via a git repository.
Yes, six very basic stubby legs at the moment, tucked away in the aft blisters and wing/hull assembly. When I get something flyable I'll upload somewhere. Autopilot for landing etc. may well take some time for me to figure out(if ever!).

I realised last night that since I know(reasonably accurately) the cross-section area of the hull, canards and wings, and can estimate their respective CoP points - I can calculate the total effective area(depending on aerofoil angle) and effective CoP, and simulate that using one (or maybe three) aerofoils. And if I can calculate where the CoP needs to be for steering, then I can set the aerofoil angle as required.

And as a fudge for the yaw torque, I figure I can calculate that by using proportion of the total drag * aerofoil area * sin(aerofoil angle) ... or something like that.

Unsurprisingly, I find if I shift the CoG on my mesh down 3m, the canards and wings turn out to be nicely "balanced" (aerofoil area x distance to CoG). Think I'll go with that. I'm ignoring shift in CoG due to fuel consumption for the time being, but I think it would actually help stability on the way up and down.

Going to give it a try and see what happens. Need to remake RCS and shift mesh, etc.etc. before that though.

Cheers,
Brian
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