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Old 10-09-2019, 12:56 AM   #16
Kyle
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There's a detailed flight profile of Starship and Super Heavy on flightclub.io that you may find useful for a rough estimate.
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Old 10-09-2019, 07:01 PM   #17
francisdrake
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I tried to estimate the lift and drag of a lifting body at hypersonic speeds, based on the NASA paper mentioned earlier. The graph shows lift (blue) and drag (red). Note the different scales of the Y-axis.

The NASA paper only covers an AoA of 0 to 20. The rest is guesswork. The lift/drag ratio changes over the AoA, this is why the drag line has a kink at 15.
Attached is also the Excel-file to play around. This includes sheets for Orbiter's Delta Glider and Atlantis shuttle as well.
Attached Files
File Type: zip Lift vs drag.zip (4.0 KB, 3 views)
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Old 10-09-2019, 08:48 PM   #18
BrianJ
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Quote:
Originally Posted by Kyle View Post
 There's a detailed flight profile of Starship and Super Heavy on flightclub.io that you may find useful for a rough estimate.
Great, thanks. Had a quick look but I could only get the SuperHeavy+Starship ascent profile (will be useful in future) - is there a way to look at the Starship back-flip sequence? I couldn't find it!

@francisdrake
Totally awesome - thanks! I have a feeling I will be needing your help implementing the correct Lift/Drag functions in the code. I'm just using my Falcon booster aerodynamics at the moment, no idea if it is anywhere near correct, so your data will be extremely useful.


Got the mesh into Orbiter just to test the basics, first thing I find is I have to use really strong RCS to get this beast to turn, even when it's mostly empty - what are the Space Shuttle RCS engines rated at? (I better check if I got the right PMI inertia values too).


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Cheers,
Brian
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Old 10-11-2019, 05:44 PM   #19
Kyle
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This is the best I could find and I'm sure you've already seen it. Looks like the flip takes place at 500m (!) moving at a velocity of 66 m/s. What specifically do you wish to know about the backflip sequence? I'm sure I could dig and find out at least educated guesses.

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Old 10-12-2019, 01:45 PM   #20
escorpio
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https://www.spacex.com/sites/spacex/...mars-entry.mp4
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Old 10-12-2019, 04:12 PM   #21
BrianJ
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Thanks for the extremely useful videos, guys I hadn't seen such a clear version of either.
I'm just looking for any and all info about the reentry and landing.
Very useful to see that "terminal velocity" is around 70m/s - I'm surprised it's that low, but that is indeed close to what I'm getting in Orbiter using airfoils sized to the cross section area of hull, wings, etc.

I've implemented vertical/ horizontal airfoils for the hull, and horizontal airfoils for the canards and wings, sized and positioned as realistically as I can, equally balanced around CoG. The aerofoil size and position is set according to the angle of the wing/canard - maximum deflection is 60deg, so that is a 50% reduction in effective area. Seems to steer OK! Yaw torque is a fudge, using a proportion of current drag.

Lift/Drag is about 1/2 at 45deg AoA, which is better than I used previously with the Dragon capsule or Falcon booster, and reflects francisdrake's graph data.

RCS is now more Shuttle style, and mounted above centreline, 9000N each which I think is equivalent to two Shuttle RCS engines.

RCS is switched off while main engines are active, control is by main engine gimballing.

If OH is working, I might upload a trial version soon.

Cheers,
Brian
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Old 10-12-2019, 05:15 PM   #22
Kyle
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OH still isn't working, so you'll have to upload here maybe?
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Old 10-13-2019, 01:12 AM   #23
perseus
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Cheer up, and go ahead with your project

Last edited by perseus; 10-13-2019 at 02:40 PM.
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Old 10-13-2019, 06:17 PM   #24
RacerX
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working on one myself. Heres my hopper

Last edited by RacerX; 10-13-2019 at 06:19 PM.
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Old 10-13-2019, 09:40 PM   #25
BrianJ
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Quote:
Originally Posted by perseus View Post
 Cheer up, and go ahead with your project
Many thanks! I'm full of cheer and storming ahead
That video reminded me they probably aren't going to be using much RCS (according to Elon) on the initial Mk.1 trials. I'm not happy with my RCS solution anyway, will probably change in future, but it works for now.

Quote:
Originally Posted by RacerX View Post
 working on one myself. Heres my hopper
Brilliant! I wanted to play with one of those, but figured I didn't have the time to make it. You have it working in Orbiter? Really nice looking mesh, you have a Starship of similar standard??

I've added an attitude controller and one basic function - go to anti-groundspeed vector (useful for landing, throttle is still manual). A few more things to check (not sure the gimballed main engines are going to be compatible with IMFD, etc.) and I'll upload a "Beta" version somewhere.


Cheers,
Brian

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Old 10-14-2019, 06:05 PM   #26
BrianJ
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Default Beta test .zip

OK, here's a beta test pack for anyone that's interested....
Unzip into Orbiter folder as usual, docs and test scenarios in their respective folders.

I've added a "Reentry Mode" with aerofoils folded back and stable at 60deg AoA, and some alternative cockpit views so I can see the HUD airspeed indicator while landing etc.

Still a lot of work to do with this. Do let me know if you have any bug reports, suggestions, etc.

I haven't managed to land on target yet.

starship_mk1_beta_191014.zip
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Old 10-15-2019, 02:12 AM   #27
NextBigLeap
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I haven't tried to land in a specific spot per say, but I've managed to get the thing on the ground upright at a relatively gentle velocity. Cant seem to get the flip maneuver at ALL, I pitch down a bit to cancel any backwards velocity at a low altitude, then go vertical with rcs, and apply thrust to a touchdown. This obviously isn't the engine gimbal to flip the ship against the velocity vector that we've seen in the video. Cant wait for the real Mk1 flight data!
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Old 10-15-2019, 10:47 AM   #28
vchamp
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Does it work for everyone? I get crashes when start a Starship scenario or add Starship in scenario editor, with the default graphics client or D3D9ClientR3.10. All other modules are disabled. Orbiter.log doesn't have error messages.
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Old 10-15-2019, 11:34 AM   #29
BrianJ
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Quote:
Originally Posted by NextBigLeap View Post
 I haven't tried to land in a specific spot per say, but I've managed to get the thing on the ground upright at a relatively gentle velocity. Cant seem to get the flip maneuver at ALL, I pitch down a bit to cancel any backwards velocity at a low altitude, then go vertical with rcs, and apply thrust to a touchdown. This obviously isn't the engine gimbal to flip the ship against the velocity vector that we've seen in the video. Cant wait for the real Mk1 flight data!
Hi,
I manage to get it down safely about 10% of the time, best I've done is about 2km from target (more by luck, I think). I usually try to level out at about 3km alt., then hit the "retro attitude" button, then immediately engage main engines at about 50% and give it a few bursts at full throttle if it's coming down too quick.


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Originally Posted by vchamp View Post
 Does it work for everyone? I get crashes when start a Starship scenario or add Starship in scenario editor, with the default graphics client or D3D9ClientR3.10. All other modules are disabled. Orbiter.log doesn't have error messages.
You might post your orbiter.log anyway, it might have some clues. Works for me anyway (obviously).


I'm just wondering if the "default" position for the wings/canards is actually folded back, and steering is done by opening them out - I'm doing it the other way around at the moment. Might give it a try and see if it makes life easier.



Cheers,
Brian
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Old 10-15-2019, 11:57 AM   #30
vchamp
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This is the log with only Orbiter base package and Starship Mk1 installed. When I start another scenario without a crash then the log seems to be the same.
Code:
**** Orbiter.log
000000.000: Build Aug 28 2016 [v.160828]
000000.000: Timer precision: 3.20724e-007 sec
000000.000: Found 0 joystick(s)
000000.000: Devices enumerated: 6
000000.000: Devices accepted: 5
000000.000: [ ] RGB Emulation (SW)
000000.000: [ ] Direct3D HAL (HW)
000000.000: [x] Direct3D T&L HAL (HW)
000000.000: [ ] Direct3D HAL (Intel(R) HD Graphics 4600) (HW)
000000.000: [x] Direct3D T&L HAL (Intel(R) HD Graphics 4600) (HW)
000000.000: Module AtlantisConfig.dll .... [Build 160828, API 160828]
000000.000: Module AtmConfig.dll ......... [Build 160828, API 160828]
000000.000: Module DGConfigurator.dll .... [Build 160828, API 160828]
000000.000: Module ScnEditor.dll ......... [Build 160828, API 160828]
000000.000: 
000000.000: **** Creating simulation session
000000.000: DirectDraw interface OK
000000.000: Direct3D interface OK
000000.000: Graphics: Viewport: Window 694 x 365 x 32
000000.000: Graphics: Hardware T&L capability: Yes
000000.000: Graphics: Z-buffer depth: 32 bit
000000.000: Graphics: Active lights supported: 8
000000.000: Loading 15382 records from star database
000000.000: ---------------------------------------------------------------
000000.000: >>> ERROR: DDraw error DDERR_BLTFASTCANTCLIP
000000.000: >>> [OrbiterGraphics::clbkBlt | .\OGraphics.cpp | 1633]
000000.000: ---------------------------------------------------------------
000000.000: Module Sun.dll ............... [Build 160828, API 160828]
VSOP87(E) Sun: Precision 1e-006, Terms 554/6634
000000.000: Module Mercury.dll ........... [Build 160828, API 160828]
VSOP87(B) Mercury: Precision 1e-005, Terms 167/7123
000000.000: Module Venus.dll ............. [Build 160828, API 160828]
000000.000: Module VenusAtm2006.dll ...... [Build 160828, API 160828]
VSOP87(B) Venus: Precision 1e-005, Terms 79/1710
000000.000: Module Earth.dll ............. [Build 160828, API 160828]
000000.000: Module EarthAtmJ71G.dll ...... [Build 160828, API 160828]
VSOP87(B) Earth: Precision 1e-008, Terms 2564/2564
000000.000: Module Moon.dll .............. [Build 160828, API 160828]
ELP82: Precision 1e-005, Terms 116/829
000000.000: Module Mars.dll .............. [Build 160828, API 160828]
000000.000: Module MarsAtm2006.dll ....... [Build 160828, API 160828]
VSOP87(B) Mars: Precision 1e-005, Terms 405/6400
000000.000: Module Phobos.dll ............ [Build ******, API 060425]
000000.000: Module Deimos.dll ............ [Build ******, API 060425]
000000.000: Module Galsat.dll ............ [Build 160828, API 160828]
000000.000: Module Jupiter.dll ........... [Build 160828, API 160828]
VSOP87(B) Jupiter: Precision 1e-006, Terms 1624/3625
000000.000: Module Io.dll ................ [Build 160828, API 160828]
000000.000: Module Europa.dll ............ [Build 160828, API 160828]
000000.000: Module Ganymede.dll .......... [Build 160828, API 160828]
000000.000: Module Callisto.dll .......... [Build 160828, API 160828]
000000.000: Module Satsat.dll ............ [Build 160828, API 160828]
000000.000: Module Saturn.dll ............ [Build 160828, API 160828]
VSOP87(B) Saturn: Precision 1e-006, Terms 2904/6365
000000.000: Module Mimas.dll ............. [Build 160828, API 160828]
SATSAT Mimas: Terms 113
000000.000: Module Enceladus.dll ......... [Build 160828, API 160828]
SATSAT Enceladus: Terms 33
000000.000: Module Tethys.dll ............ [Build 160828, API 160828]
SATSAT Tethys: Terms 101
000000.000: Module Dione.dll ............. [Build 160828, API 160828]
SATSAT Dione: Terms 59
000000.000: Module Rhea.dll .............. [Build 160828, API 160828]
SATSAT Rhea: Terms 68
000000.000: Module Titan.dll ............. [Build 160828, API 160828]
SATSAT Titan: Terms 100
000000.000: Module Iapetus.dll ........... [Build 160828, API 160828]
SATSAT Iapetus: Terms 605
000000.000: Module Uranus.dll ............ [Build 160828, API 160828]
VSOP87(B) Uranus: Precision 1e-006, Terms 1827/5269
000000.000: Module Miranda.dll ........... [Build ******, API 060425]
000000.000: Module Ariel.dll ............. [Build ******, API 060425]
000000.000: Module Umbriel.dll ........... [Build ******, API 060425]
000000.000: Module Titania.dll ........... [Build ******, API 060425]
000000.000: Module Oberon.dll ............ [Build ******, API 060425]
000000.000: Module Neptune.dll ........... [Build 160828, API 160828]
VSOP87(B) Neptune: Precision 1e-006, Terms 391/2024
000000.000: Finished initialising world
000000.000: Module starship_mk1.dll ...... [Build 191014, API 160828]
000000.000: Finished initialising status
000000.000: Finished initialising camera
000000.000: Finished setting up render state
000000.000: Finished initialising panels
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