Space Shuttle Ultra 1.25 Revision B development

[SiameseCat]

At the moment, I'm working on fixing the horizontal aerodynamics model, which is pretty bad (among other problems, there's no 'natural' yaw force to correct any sideslip).

 

[DaveS]

Checked in a new Discovery texture. This version is valid for missions starting with STS-95 in October 1998 and can be used through STS-133. Atlantis will be next on the upgrade list.

---------- Post added 04-10-12 at 02:56 AM ---------- Previous post was 04-09-12 at 08:49 PM ----------

Atlantis texture now checked in. This texture is valid for missions starting with STS-101 in May 2000 through STS-135. Endeavour will be the final modern texture to be done.

---------- Post added at 09:29 PM ---------- Previous post was at 02:56 AM ----------

And here's the new Endeavour texture. Valid from STS-88 in December 1998 through the final mission STS-134 in May 2011.

---------- Post added 04-11-12 at 02:21 AM ---------- Previous post was 04-10-12 at 09:29 PM ----------

Checked in a updated mesh of the new Ku band DA. I also checked the code changes needed to make the animations work with the new mesh. Looks pretty good now!

 

[RacerX]

I have read all 137 pages and all posts in this thread. I really appreciate everything you guys are trying to accomplish here. What a great effort you people have put forth in order to achieve the most accurate space shuttle that is possible. I applaud you guys for your work. Really nice job! :thumbup:

 

[DaveS]

You might have noticed that when the PLBDs are closed, the new Ku band DA intersect with the radiator panels. I am aware of this issue and investigating it.

 

[DaveS]

You might have noticed that when the PLBDs are closed, the new Ku band DA intersect with the radiator panels. I am aware of this issue and investigating it.

This problem has now been corrected and checked in.

---------- Post added at 06:03 AM ---------- Previous post was at 01:44 AM ----------

Something I have noticed during my work with the Ku band system is that currently the DIRECT STOW switch on R13L work like the normal DEPLOY/GND/STOW switch. This is wrong according to my research. The DIRECT STOW is only linked to the DA drive motor, and doesn't command the DA gimbals.

So all the DIRECT STOW switch should do is rotate the DA to the stowed position without ever rotating the gimbals. This step is for the crew to execute, to manually position the gimbals before stowing the DA. That is done with the SLEW AZM/SLEW ELEV switches on A1U. This is true even for nominal stow that doesn't use the DIRECT STOW method.

 

[DaveS]

Question on the entry guidance: Is it correct that it shouldn't target the the HAC for intercept? For me it never aligns with the HAC prior to going CSS.

 

[SiameseCat]

When are you going CSS? The autopilot only works down to M2.5, after that you have to fly the shuttle manually. The HUD guidance diamond works from M2.5 down to landing.

 

[DaveS]

When are you going CSS? The autopilot only works down to M2.5, after that you have to fly the shuttle manually. The HUD guidance diamond works from M2.5 down to landing.

Usually around that time. But the orbiter is far off-course and nowhere near the HAC for a smooth intercept.

---------- Post added at 02:58 AM ---------- Previous post was at 02:19 AM ----------

Here's a screenshot of the problem. Note the orbiter position relative to the HAC on CRT3:

 

[SiameseCat]

Looks fine to me; you should be able to steer towards the HAC, then roll wings level until HAC intercept. HAC intercept only occurs when the shuttle is subsonic, so it still has to fly for about a minute before HAC intercept.

 

[DaveS]

Looks fine to me; you should be able to steer towards the HAC, then roll wings level until HAC intercept. HAC intercept only occurs when the shuttle is subsonic, so it still has to fly for about a minute before HAC intercept.

True but shouldn't the orbiter already be on a intercept course by the time it enters TAEM?

 

[Cras]

No, that doesnt look right to me. He has to fly quite a bit to intercept the HAC, and he is not even on the right heading to do so.

It also seems the HAC on the SPEC 50 display there is not the one he should be aiming at from his current position.

 

[DaveS]

No, that doesnt look right to me. He has to fly quite a bit to intercept the HAC, and he is not even on the right heading to do so.

It also seems the HAC on the SPEC 50 display there is not the one he should be aiming at from his current position.

Correct. It seems like it is hardcoded to aim for RWY15 despite RWY33 being selected on SPEC 50.

 

[SiameseCat]

Have you actually tried following the HUD guidance and trying to land? An approach to RWY 33 works fine for me.

---------- Post added at 10:21 PM ---------- Previous post was at 10:20 PM ----------

True but shouldn't the orbiter already be on a intercept course by the time it enters TAEM?

Why? All the documentation I've seen on the entry guidance is that it tries to maintain DELAZ within some limit (+/- 10.5 degrees below M5, IIRC). It should be close to an intercept course, but not on an intercept course.

 

[Cras]

from the Shuttle Crew Ops Manual:


At TAEM acquisition, the orbiter is turned until
it is aimed at a point tangent to the HAC and
continues until it reaches way point (WP) 1. At
WP-1, the TAEM heading alignment phase
begins.


So the Orbiter should be headed to the HAC during this part. THere is a provision for a further S-turn to dissipate excess energy.

 

[SiameseCat]

That seems to prove my point - at the start of TAEM, the shuttle turns until it is aimed at the HAC.

 

[Cras]

That seems to prove my point - at the start of TAEM, the shuttle turns until it is aimed at the HAC.

That is true, but according to that picture, he is on the wrong side of the field. I do not recall ever seeing a ground track of the Shuttle landing that resembled a downwind leg that would be required in that picture.

 

[zerofay32]

From what I understand, that would be considered a Straight-in Approach. I think as a general rule, the shuttle plans to make an Overhead Approach (final line up via HAC on the opposite side of the Runway CL) to insure plenty of energy (if the shuttle is low on energy, then they "downmode" to a straight-in approach or a closer aim point). The straight-in approach could also be selected for wind or other weather conditions that don't prompt use of the opposite runway heading. At least that is how I understand it.

 

[SiameseCat]

That is true, but according to that picture, he is on the wrong side of the field. I do not recall ever seeing a ground track of the Shuttle landing that resembled a downwind leg that would be required in that picture.

The link below has the NASA predicted ground track for one of the STS-120 deorbit opportunities. The path looks pretty close to what DaveS has.
http://www.nasa.gov/images/content/196114main_KSC239_close.gif

---------- Post added at 12:10 PM ---------- Previous post was at 12:05 PM ----------

From what I understand, that would be considered a Straight-in Approach. I think as a general rule, the shuttle plans to make an Overhead Approach (final line up via HAC on the opposite side of the Runway CL) to insure plenty of energy (if the shuttle is low on energy, then they "downmode" to a straight-in approach or a closer aim point). The straight-in approach could also be selected for wind or other weather conditions that don't prompt use of the opposite runway heading. At least that is how I understand it.

DaveS's picture is an Overhead approach (HAC turn angle > 180 degrees). That's why the shuttle has to approach from the other side of the runway - if the shuttle was on the same side of the runway as the HAC, the turn angle would be less than 180 degrees and it would be a Straight-In approach.

 

[Cras]

That STS-120 ground track is what one would expect, you cross the runway on the landing side infront of the threshold ,and fly into the HAC. A second look at the DaveS' pic shows that that may be the case here. At first look it didnt seem like that is the trajectory he was heading in , but such things are hard to gauge from just one still.

 

[zerofay32]

DaveS's picture is an Overhead approach (HAC turn angle > 180 degrees). That's why the shuttle has to approach from the other side of the runway - if the shuttle was on the same side of the runway as the HAC, the turn angle would be less than 180 degrees and it would be a Straight-In approach.

Crap, you're right. The first time I looked at the picture, I thought the HAC was on the left side of the CL. Oops :embarrassed:. Sorry about that. (helps to look at longer than 2 sec.)