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Old 09-24-2019, 03:23 PM   #16
Snax
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Quote:
Originally Posted by kuddel View Post
 I believe, the 2nd 1.d-step should read "ITEM17+0 ENTR", right?
You're right ! Didn't quadruple check my post :p
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Old 09-24-2019, 03:35 PM   #17
DaveS
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You're supposed to use MM302 for the de-orbit burn (title is DEORB MNVR EXEC), not MM202. MM202 is only for on-orbit burns. MM304 comes at at EI-5 minutes. In either MM104, 105, 202 and 302, ITEM 27 is used to maneuver to the correct attitudes. You never use MM201 for any burn preps. The xxx MNVR EXEC screens holds everything required to execute an OMS burn, there's no need for any other screen.
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Old 09-24-2019, 03:52 PM   #18
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Yes I know, that's why I said it's not realistic but gets the job done too.
At least for the beginners (like me) they are safe on the ground.
Because we don't have a TIG and PEG given by BaseSync, so we need another "approach" wich works for me

(edited)

Last edited by Snax; 09-24-2019 at 04:07 PM. Reason: Added a paragraph
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Old 09-24-2019, 04:11 PM   #19
Gingin
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Ant is the anticipation angle . Ie angle from entry interface to the landing site .
75 degrees is a good value, corresponding to 75 times 60 ( Nm) = 4500 Nm from entry interface at 400 kfeet up to landing zone.

I am doing like Snax except everything in ops 3 and major mode 302 for deorbit burn .
On Base sync , you have in closest passage the time in seconds to the target site.
You can calculate your deorbit TIG by targeting the burn 2700 seconds before landing site ( 45 mn / half a period orbit before )

And intensity like I said from a circular orbit : Current perigee minus 20 Nm times 1.8 will give a very good first approximation to what enter in item 19 for Dvx
Then item 22 to load and see the targeted perigee , and play a bit with Dvx to have 20 Nm ish


@Urwumpe: I will try to give an example for Leo tools applied to Orbiter for deorbit burn once I am back behind the computer
Problem is to feed it with the current state vector which is in a different inertial frame in Orbiter and Fg.

But it can be define also with latitude longitude and vertical/horizontal speed which we can easily found In map and surface mfd .
So it might be handy to use with Orbiter, will try that .

No off plane burn propellant burn forecasted With it, but wa can always add a given value to burn on Y axis for fine tune cog trimming giving it will not,change the orbit shape during deorbit burn

Last edited by Gingin; 09-24-2019 at 04:14 PM.
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Old 09-24-2019, 04:45 PM   #20
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Quote:
Originally Posted by Gingin View Post
 @Urwumpe: I will try to give an example for Leo tools applied to Orbiter for deorbit burn once I am back behind the computer
Problem is to feed it with the current state vector which is in a different inertial frame in Orbiter and Fg.
Well, if it is WGS-84, it should fit into SSU.
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Old 09-24-2019, 04:54 PM   #21
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Quote:
Originally Posted by Gingin View Post
 Ant is the anticipation angle . Ie angle from entry interface to the landing site .
75 degrees is a good value, corresponding to 75 times 60 ( Nm) = 4500 Nm from entry interface at 400 kfeet up to landing zone.
Thanks for the info !

Quote:
Originally Posted by Gingin View Post
 You can calculate your deorbit TIG by targeting the burn 2700 seconds before landing site ( 45 mn / half a period orbit before )

And intensity like I said from a circular orbit : Current perigee minus 20 Nm times 1.8 will give a very good first approximation to what enter in item 19 for Dvx
Excellent, I'm saving this on my phone to test when I get home friday
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Old 09-24-2019, 07:01 PM   #22
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Quote:
Originally Posted by Snax View Post
 Hi, if I can be of help, here's how I do it with BaseSync MFD for the Deorbit burn.

Deorbit burn preparations
  1. With OPS201 I tell the Shuttle orbiter to be in retrograde (+ or - 15 degrees for the SSMEs):
    1. ITEM14+5 (body reference)
    2. ITEM15+75 (90 for retrograde position minus 15 for SSMEs)
    3. ITEM16+0
    4. ITEM17+0 ENTR
    5. 19 ENTR (the Shuttle will be in retrograde and heads down, you can do 105, 0, 180, to be heads up)
      (you can type as follows: ITEM14+5+75+0+0+ENTR all at once)
    6. DAP in AUTO
  2. Then in OPS202: I enter a huge value in PEG7 in ITEM19 (eg: ITEM19-500 ENTR), Make sure ITEM20 and ITEM21 are nulled. This will give me so much negative DeltaV so I can stop it by shutting down the OMS by hand on the C3 panel.
  3. For the TIG I enter any value that is before the MET so the GPC will believe it's time to burn and tell you to initiate the burn by pressing ENTR again (you'll just need to press ENTR when you want to that way)
  4. Don't use ITEM27 for this "technique", just ITEM22 and ITEM23, you already set your retrograde position.
  5. And now wait until BaseSync tells to, basically when DeltaV reaches 0 in that MFD, you'll need to configure BaseSync for the reentry:
    1. ANG: 1.23 (angle of penetration of the atmosphere)
    2. ANT: 74,48 (don't remember what this value is)
    3. ALT: 121,92km (wich is 400'000ft)
    (here's a turotial for BaseSync by the great David Courtney)

Then for the reentry parameters
  1. with OPS201 I type:
    1. ITEM14+5 (body reference)
    2. ITEM15+230 (pitch +40)
    3. ITEM16+0
    4. ITEM17+0 ENTR
    5. ITEM19 ENTR (to initiate the tracking)
    6. DAP in AUTO
  2. Then I switch to MM303 (OPS303) and wait the TFF to reach 0, a few minutes before to that (~5mins), I start the APUs.
  3. I switch the DAP to LVLH to maintain my 40 pitch of attitude just in case
  4. MM304 when TFF is 0 (Time For Four hundred thousand feet)

I know it's not realistic but it gets the job done when you just want a quick ride in orbit. It works every time.


__________________________________________________ _____

Here's a video how I do it (FYI, I talk in french to my viewers).
[Orbiter] STS-107 Quick Launch and Landing - YouTube

Timestamps
22:45: OPS201 for retrograde position
28:20: retrograde burn initiated
29:46: OPS201 for 40 AoA for the reentry
30:50: OPS303 then SPEC50 for the horiz sit then ITEM4 for KSC RWY33
32:57: APU start
33:54: OPS304 (i forgot to click RESUME to revert the screen to the graph)
37:15: Data Air Probles deployed (below Mach 5) and HUD set to ON, will be live after TRAJ5 in the CRT3
38:20: HUD is live
39:14: going CSS (control stick steering) at Mach 0.95

Thanks for sharing Snax: I think the Attitude parameters in OPS2 don't need to be inputted. Assuming a retrograde head down deorbit attitude, if after the deorbit burn you set the DAP to INRTL the orbiter should reach E.I. with an Alpha around 40. Anyway as soon as you enter MM304 (with the DAP in AUTO) before hitting E.I. the autopilot will set and maintain the desired attitude.
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Old 09-24-2019, 07:55 PM   #23
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Quote:
Originally Posted by Wolf View Post
 , if after the deorbit burn you set the DAP to INRTL the orbiter should reach E.I. with an Alpha around 40.
You should leave the DAP alone for the entire time you're in OPS3. MM303 will re-orient the vehicle to the proper inertial attitude for entry assuming you have ITEM 27 active (the 27 has an asterisk(*) next to it). There's no reason to change the DAP settings once you're getting ready for the de-orbit burn. The DAP configuration should be A/AUTO/PRI/DISC RATE/DISC RATE/DISC RATE.

In fact, this is what happened during the final pre-entry preps of STS-107. The CDR accidentally bumped the RHC out of its detent position causing an System Management (SM) Alert tone to be sounded along with an fault message being displayed in the error log (SPEC 99). He saw that and did put the DAP back into AUTO (it had downmoded to Inertial), but forgot to re-enable ITEM 27 on MM303. The GNC officer in the MCC noticed that the orbiter was drifting out of attitude and requested that the crew perform an ITEM 27 to get back into the proper attitude.

The SM alert for the RHC bump is at 0:32 while the call for the ITEM 27 from the CAPCOM is at 1:56.


Last edited by DaveS; 09-24-2019 at 08:06 PM.
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Old 09-25-2019, 02:02 PM   #24
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Quote:
Did you have an example for that?
I'm not sure what 'that' refers to - an example for optimizing a PEG-4 de-orbit burn is given on the page I linked. An example for a pocket formula GinGin has sort of given.

Quote:
And can you also allow burning off-target to dump excessive aft propellant mass in the solution?
That's trivial, because it's completely independent of the targeting which only produces retrograde and radial DV components (the lateral offset you manage with the remaining OMS propellant is far tinier than the cross range capability, so it is pretty much irrelevant) - so the realistic workflow would be that you first run the optimizing tool to get the best PEG-4 parameters plus TIG, enter that into the Shuttle MNVR page, add the desired amount of fuel to be wasted there and let the Shuttle compute that PEG-4 problem.

The alternative workflow is that you take the PEG-7 parameters from the optimizer (which do not contain a DY component), take a pocket calculator to see how much DY you need to burn the amount of fuel you want, add that, enter that as PEG-7 target on MNVR and do that burn.

---------- Post added at 10:58 AM ---------- Previous post was at 09:44 AM ----------

Quote:
Well, if it is WGS-84, it should fit into SSU.
No, it's the standard JSBSIm inertial system initialized for zero time - so you need to rotate it with the sidereal time of the assumed simulation starting date/time (there may even be an option to do that automagically - anyway, it's not complicated to do the trafo).

---------- Post added at 02:02 PM ---------- Previous post was at 10:58 AM ----------

Quote:
Yes I know, that's why I said it's not realistic but gets the job done too.
Wow - that is one ugly hack of Shuttle procedures...




Quote:
The DAP configuration should be A/AUTO/PRI/DISC RATE/DISC RATE/DISC RATE.
Actually, changing to OPS 3 should eliminate most of the orbital DAP options, because it loads the transition DAP until MM 304 (where Aerojet is loaded). so most of these should no longer be illuminated.

But, well, the point of the hack seems to be to override the on-board targeting with fake values so that the Base Sync MFD can be used (think of the idea to manually end the burn, to manually calculate prograde direction...) - which probably works much better in OPS 2 than in OPS 3, because OPS 3 has more safeguards against that kind of thing...
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Old 09-27-2019, 09:52 AM   #25
Gingin
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A quick example of Peg 4 with Thorsten tool applied to Orbiter for deorbit and spherical gravity to start with.

Reminder to the links with tutorials and explanations about the tool

http://www.science-and-fiction.org/s...targeting.html



Scenario tested is "Atlantis in Orbit" from SSU files


I fired Base Sync and waited to have a good crossrange ( here in One orbit, crossrange of 500 km, good)







To define the position of the Shuttle, we need longitude, latitude, Total speed ( Orbital Speed), upward speed ( vertical speed) , altitude and course ( heading when in prograde vector, ie LVLH Yaw equal zero)
We can get those in Surface MFD really quickly





Then we enter them in a config file ( converted for imperial units in my case, but can be in meters with SI units)
For now, we can't set the MET coupled to that position ( Thorsten is editing a fix)
So at the position defined in the file, time is set at zero, like a Base Time in Spec 34

Position in game was at MET 000/06:38:00, so it is our new base time .


Then we enter some value under PEG 4 guidance ( I took STS 30 one's, and adjusted a bit theta angle to have an almost null radial velocity)
Time of ignition is roughly 2700 seconds before KSC like we explained earlier, giving us 00:39:00 mn after the base time, ie. 000/ 07:17:00 in game


And then we run the tool, giving us a burn of 311 ft/s retrograde and 5 ft/s radial upward, for a re entry range of 4200 Nm ish






Solution loaded in MM 302, and quite coherent so far ( perigee targeted of 19 Nm)





Burn time , not too far from our 2700 sec from KSC rule of thumb




And entry range at 4300 Nm at Entry interface.
So really useful in Orbiter for complex Peg 4 calculations and even OMS 1/2 targeting, Rendez Vous planning coupled with Indy FDO tools

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