Space Shuttle Ultra 1.25 Revision B development

[Donamy]

How about stowing the SSMEs after ET sep ?

 

[Poscik]

The HAC radius isn't constant.

When you're flying the HAC, you might want to try following the guidance diamond - it seems to work pretty well after HAC intercept, especially in the roll channel, although it doesn't work until you're on/near the HAC.

Yeah, roll channel works pretty fine, but it messes up with pitch sometimes, "suggesting" me to fly too low on HAC intercept.

 

[Urwumpe]

Can anyone tell me if HAC radius is calculated "in-time" or is it constant? I mean in SSU algorithm. I'm flying STS-107 scenario and I have real problem to remain on energy during HAC. Any chance to "quick-lock" HAC radius to be constant if so?

AFAIR, HAC radius is not constant, but a function of altitude.

 

[SiameseCat]

Yeah, roll channel works pretty fine, but it messes up with pitch sometimes, "suggesting" me to fly too low on HAC intercept.

That sounds about right. The TAEM guidance is only implemented after HAC intercept, at the moment, so I think the guidance is slightly messed up.

 

[Poscik]

Ok. If SSU calculates range to touchdown somehow, I can add "glide slope" indicator to SPEC50, so we will be able to intercept HAC on correct altitude. AFAIK glide path angle is 20 degrees. Please Correct me if I'm wrong

 

[DaveS]

Ok. If SSU calculates range to touchdown somehow, I can add "glide slope" indicator to SPEC50, so we will be able to intercept HAC on correct altitude. AFAIK glide path angle is 20 degrees. Please Correct me if I'm wrong

OGS is based on vehicle weight. Lightweight orbiter(less than 180,000 lbs) targets 20° while heavyweight orbiters(more than 220,000 lbs) target 18°. Midweight orbiters can target any glideslope between 18° and 20°.

Recommended reading is SCOM, section 7.4 Terminal Area Energy Management and Approach-

 

[Poscik]

Ok, so I'll set it temporarily to 19°. It is meant to be from mach 2.5 till HAC intercept. Then already done guidance will do the rest of the job.

[EDIT]
Do GetMass() function include mass of attached objects?

 

[SiameseCat]

The 18-20 degree glideslope is for final approach, not from Mach 2.5 to HAC intercept.

 

[Poscik]

I found necessary info in SCOM.

The HAC is intercepted at various altitudes, depending on HAC turn angle. The altitude varies between about 50,000 ft for a 360° HAC to 20,000 ft for a 90° HAC (straight in).

 

[Urwumpe]

Do GetMass() function include mass of attached objects?

Should not do that.

 

[SiameseCat]

I have some documents describing the TAEM guidance (that's where the HAC code came from); I should be able to finish the rest of the TAEM guidance sometime next week.

 

[DaveS]

Checked in an updated Ku band DA mesh/texture. Now I have really taken it as far as I can take it. The only things that needs to be added is the dish ribs and the gold mylar foil on the DEA. Additionally but not required is the various wires and cables connecting the various components of the DA.

I have also noticed that we're missing a panel related to the Ku band system and the RMS. This is panel A14 which is below the A8 panels. A14 has the OMS/RCS heater switches along with the jettison switches for the Ku band DA and starboard/port RMS units.

---------- Post added 04-02-12 at 01:46 AM ---------- Previous post was 04-01-12 at 03:14 AM ----------

Here's a set of comparison images of the new(left), real(center) and current(right) Ku band DAs:

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Which of the two versions would you prefer?

 

[Donamy]

What's the difference in polys ?

 

[DaveS]

What's the difference in polys ?

The delta is 1390 in favor of the new mesh which has 4746 polys vs 6136 polys for the original.

---------- Post added at 03:32 AM ---------- Previous post was at 02:40 AM ----------

Checked in a corrected DA mesh which fixes the missing material definitions on the alpha gimbal/boom as well as the position of the gimbal lock structure and the dish.

 

[SiameseCat]

I have some documents describing the TAEM guidance (that's where the HAC code came from); I should be able to finish the rest of the TAEM guidance sometime next week.

Does anyone know what the 'normal' bank angle around the HAC is? SSU currently flies at about 30 degrees, but I think this might be too low.

 

[DaveS]

Does anyone know what the 'normal' bank angle around the HAC is? SSU currently flies at about 30 degrees, but I think this might be too low.

Based on my own experiences with the HAC flyaround, I would say it is around 45°s.

 

[Poscik]

Following SCOM it is 45 degrees, with option to 60 degrees during strong tailwind.

 

[Urwumpe]

Isn't the actual bank angle calculated by guidance and adaptive to speed and location relative to the HAC?

 

[SiameseCat]

Checked in the guidance code for the Acquisition phase (i.e from M2.5 to HAC intercept).

---------- Post added at 03:21 PM ---------- Previous post was at 03:18 PM ----------

Isn't the actual bank angle calculated by guidance and adaptive to speed and location relative to the HAC?

Yes; I was asking about the normal bank, for when the shuttle is on the HAC with the correct velocity/altitude.

 

[Poscik]

Just tested the guidance. Works fantastic! Great job!