Author Topic: Shuttle Questions Q & A (Part 4) (Read 753771 times)

Jim · « **Reply #180 on:** 12/01/2007 06:27 pm »

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Lee Jay - 1/12/2007 1:54 PM

On final approach the HUD shows glide slope target and when to flare and so on. I thought that stuff came from the microwave landing system like a normal airport localizer. If MLS isn't there, this chart shows it would be replaced by TACAN or, now, GPS. Would the HUD be driven the same way by these systems during final approach, or would that last 5000 feet be flown visually without benefit of the HUD glide slope and flare information?

The HUD is driven by the onboard guidance. The guidance system uses multiple sources (Radar Altimeter, GPS, MLS, air data, etc) to provide the most accurate picture (by reducing errors) of the orbiter's state and to provide redundancy.

Mark probably can list what are the minimum data sources required. Something more than air data and the drag H needs to be used

generic_handle_42 · « **Reply #181 on:** 12/01/2007 06:29 pm »

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MKremer - 1/12/2007 2:05 PM

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Lee Jay - 1/12/2007 12:54 PM

Okay, thanks for the chart. I think one of my misunderstandings was that I thought the HAC was formulated from ground sources, not from the on-board NAV. I got this apparently-erroneous idea from the ground calls that they are on at the 180 etc. It seems that if the crew has the same info as the ground that these calls wouldn't be necessary. Thanks for clearing that up.

It's like the "go at throttle up" call during ascent - done after the actual occurance, but just to let the crew know all the orbiter data the ground is monitoring was still looking good at that point.

In fact, if you watch the spectacular reentry videos on L2, you'll frequently hear the crew mention "on at the 180" and "on at the 90" to each other before the call from the ground.

psloss · « **Reply #182 on:** 12/01/2007 07:35 pm »

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Lee Jay - 1/12/2007 1:54 PM

Okay, thanks for the chart. I think one of my misunderstandings was that I thought the HAC was formulated from ground sources, not from the on-board NAV. I got this apparently-erroneous idea from the ground calls that they are on at the 180 etc. It seems that if the crew has the same info as the ground that these calls wouldn't be necessary. Thanks for clearing that up.

In the name of being prepared it is possible that they might have less awareness on-board than the ground depending on what combination of failures has occurred. Hopefully it's only engaged in sims, but they just recently added HUD display capabilities (among other things) to the BFS, as Chris wrote about:
http://www.nasaspaceflight.com/content/?cid=5254

Zoomer30 · « **Reply #183 on:** 12/03/2007 01:00 am »

Something I noticed during the engine start sequence of STS-118. At about T-9 or T-8 secs I saw a white puff from each engine in sequence. It went from Engine 3 then 2 then 1. Then at -6secs they ignite. What was this "white puff"? I dont think I have seen it before.

Ford Mustang · « **Reply #184 on:** 12/03/2007 02:13 am »

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Zoomer30 - 2/12/2007 9:00 PM

Something I noticed during the engine start sequence of STS-118. At about T-9 or T-8 secs I saw a white puff from each engine in sequence. It went from Engine 3 then 2 then 1. Then at -6secs they ignite. What was this "white puff"? I dont think I have seen it before.

Are these the correct puffs? If so, I believe they are purging the excess LOX/LH2 that is left before igniting the engines.. That's my guess, I'm really not sure.

EDIT: Added STS-120 Launch snaps of the same thing happening..

Zoomer30 · « **Reply #185 on:** 12/03/2007 02:35 am »

Yep that's it. Could just be a function of how humid the air is as to it being visible or not. Since this was Aug, my bet is it was quite humid

I tried to catch a screen shot of it, but I could not stop win media player quick enough.

ChrisGebhardt · « **Reply #186 on:** 12/03/2007 04:13 am »

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Ford Mustang - 2/12/2007 10:13 PM

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Zoomer30 - 2/12/2007 9:00 PM

Something I noticed during the engine start sequence of STS-118. At about T-9 or T-8 secs I saw a white puff from each engine in sequence. It went from Engine 3 then 2 then 1. Then at -6secs they ignite. What was this "white puff"? I dont think I have seen it before.

Are these the correct puffs? If so, I believe they are purging the excess LOX/LH2 that is left before igniting the engines.. That's my guess, I'm really not sure.

EDIT: Added STS-120 Launch snaps of the same thing happening..

I've noticed this as well. I just thought it was part of the normal start-up sequence. Interesting.

Zoomer30 · « **Reply #187 on:** 12/03/2007 09:47 pm »

I have looked at a few other launches I have and you can kinda see them there as well. Must be dependent on where the sun is as to how good it reflects, and on how humid it is. Just seems like in the STS-118 it happened "early" like about 2 secs before engine start, and seemed more "abrupt"

Endeavour118 · « **Reply #188 on:** 12/04/2007 01:13 am »

what ws the name of the entry pattern used on STS-120 and what is the difference between that pattern and the pattern mostly used which is where they come up from S.America.

Lee Jay · « **Reply #189 on:** 12/04/2007 01:21 am »

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Endeavour118 - 3/12/2007 7:13 PM

what ws the name of the entry pattern used on STS-120 and what is the difference between that pattern and the pattern mostly used which is where they come up from S.America.

I think you're referring to descending instead of ascending node.

Ascending is when you are moving North as you pass the desired ground point, descending is when you are traveling South (East too in orbit, of course).

If you're moving South-West to North-East, that's ascending node and the norm for the Shuttle. They were going the opposite way, North-West to South-East, on STS-120. Apparently this was asked for by the crew and agreed to because it led to a day-time landing, instead of a landing in the dark.

DarthVader · « **Reply #190 on:** 12/04/2007 08:53 pm »

Does anyone know what type of camera is used for the ET umbilical camera?

psloss · « **Reply #191 on:** 12/04/2007 10:22 pm »

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DarthVader - 4/12/2007 4:53 PM

Does anyone know what type of camera is used for the ET umbilical camera?

It's made by:
http://www.eclipticenterprises.com/

(May be in one of their brochures...don't have time to go through them right now.)

DarthVader · « **Reply #192 on:** 12/04/2007 10:46 pm »

Thanks psloss.

jscott227 · « **Reply #193 on:** 12/04/2007 11:01 pm »

This may be off the wall...but I'm curious. In the unlikely event a shuttle crew found themselves low on energy when landing; can the OMS engines be fired to provide some thrust and help reach the runway?

Thanks, John

Jorge · « **Reply #194 on:** 12/04/2007 11:17 pm »

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jscott227 - 4/12/2007 6:01 PM

This may be off the wall...but I'm curious. In the unlikely event a shuttle crew found themselves low on energy when landing; can the OMS engines be fired to provide some thrust and help reach the runway?

No. The OMS engine nozzles are designed for vacuum and should not be fired at altitudes below 70,000 ft, otherwise the nozzle may collapse due to the pressure difference. More to the point, there is no capability in the entry/TAEM/landing software (OPS 304 and 305) to perform an OMS burn.

Lee Jay · « **Reply #195 on:** 12/05/2007 12:02 am »

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Jorge - 4/12/2007 5:17 PM

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jscott227 - 4/12/2007 6:01 PM

This may be off the wall...but I'm curious. In the unlikely event a shuttle crew found themselves low on energy when landing; can the OMS engines be fired to provide some thrust and help reach the runway?

No. The OMS engine nozzles are designed for vacuum and should not be fired at altitudes below 70,000 ft, otherwise the nozzle may collapse due to the pressure difference. More to the point, there is no capability in the entry/TAEM/landing software (OPS 304 and 305) to perform an OMS burn.

One time I saw a Shuttle landing on TV it was intermittently leaving a contrail (on the order of a second at a time). The PAO said they were burning off excess fuel. This was probably within a minute or two of landing. Were they firing aft RCS or something?

psloss · « **Reply #196 on:** 12/05/2007 12:19 am »

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Lee Jay - 4/12/2007 8:02 PM

One time I saw a Shuttle landing on TV it was intermittently leaving a contrail (on the order of a second at a time). The PAO said they were burning off excess fuel. This was probably within a minute or two of landing. Were they firing aft RCS or something?

I believe the RCS are used to help with yaw control until around Mach 1. (More than a minute before landing...usually still approaching the HAC.)

(Throwing in a few caps from the STS-83 approach. The last two frames are roughly 5 minutes from main gear touchdown.)

Jorge · « **Reply #197 on:** 12/05/2007 01:38 am »

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psloss - 4/12/2007 7:19 PM

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Lee Jay - 4/12/2007 8:02 PM

One time I saw a Shuttle landing on TV it was intermittently leaving a contrail (on the order of a second at a time). The PAO said they were burning off excess fuel. This was probably within a minute or two of landing. Were they firing aft RCS or something?
I believe the RCS are used to help with yaw control until around Mach 1. (More than a minute before landing...usually still approaching the HAC.)

That's correct.

Jorge · « **Reply #198 on:** 12/05/2007 01:41 am »

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psloss - 4/12/2007 5:22 PM

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DarthVader - 4/12/2007 4:53 PM

Does anyone know what type of camera is used for the ET umbilical camera?
It's made by:
http://www.eclipticenterprises.com/

(May be in one of their brochures...don't have time to go through them right now.)

You sure you're not confusing the umbilical camera with the LOX feedline camera?

(The feedline camera is made by Ecliptic, but I'm not sure about the umbilical camera... NASA had a still camera in the umbilical well since STS-1, but made a lot of changes after 107.)

MKremer · « **Reply #199 on:** 12/05/2007 02:31 am »

IIRC it's a Kodak digital camera assy, and it actually uses Kodak's EasyShare tech for linking with the in-cabin PGSC to transfer images (maybe why the new XP PGSCs have the comm synch problems).